Pleuronectes platessa), European flounder (Platichthys flesus), lemon sole (Microstomus kitt), megrim (Lepidorhombus whiffiagonis), and thornback ray (Raja clavate), often captured as by-catch in Norway, were characterized for their nutritional value and potential accumulation of hazardous components. The proximate composition, protein profile, fatty acid profile as well as essential and toxic trace elements and polychlorinated biphenyls (PCBs) were analyzed. Digestible indispensable amino acid (DIAA) ratios and scores (DIAAS) and contributions of omega-3 fatty acids to the diet were calculated. Analysis on proximate composition revealed low fat contents of 0.74 to 1.25% and sufficient protein contents between 16.9 and 24% in the five species. Results of DIAA indicate a profitable distribution, with contributions exceeding the daily intake recommendations for an adult person related to a 200 g fillet. Moreover, findings on the distribution of eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) showed remarkable results, considering that the investigated species are lean fish. All five investigated fish exceed the recommended average daily intake level (AI) of EPA + DHA in a 200 g portion. As to toxic trace elements and PCBs, no significantly elevated levels were found considering a portion size of 200 g. Consequently, the nutritional quality of the investigated fish can be regarded as profitable with overall low potential health risks.Exploring and making use of underutilized marine resources can be a sustainable approach to achieve future demands of fish consumption by the ever-growing population. Five species, namely European plaice ( By 2050, the demand for food is projected to increase by 50% as the world’s population is expected to reach 9.7 billion people , 2. At tThe excellent nutritional composition of fish and seafood in general has been reported in various studies and reviewed amongst others by Khalili Tilami et al. . MoreoveNext, to being a source of valuable macronutrients, fish contain essential trace elements like calcium and selenium. As a key indicator of bone density, calcium is crucial for the health of the skeleton and plays a vital role in many metabolic processes. Moreover, selenium deficiencies can lead to several diseases . Next toPleuronoectiformes) species, and a ray (Rajiformes), whereof all are often captured as by-catch in Norway and regarded as underutilized species. More specifically, the study presents the chemical and nutritional profile of European plaice (Pleuronectes platessa), European flounder (Platichthys flesus), lemon sole (Microstomus kitt), megrim (Lepidorhombus whiffiagonis), and thornback ray (Raja clavate), including comparisons between species related to health promoting nutritional components. The analyses contained the proximate composition, total and free amino acids as well as fatty acid profile. Marine food sources in general are regarded as the main contributors to the intake of contaminants, which pose a potential risk for the consumers. Therefore, PCBs and trace elements, including both essential and toxic elements, were determined to support the safe consumption of these species.The aim of the present study was to characterize four different flatfish , as shown in n = 5), as it consists of two central fillets  and two Kjeldahl Tablets Eco (3.5 g K2SO4/0.105 g CuSO4 × 5H2O/0.105 g TiO2) were added to samples (1.5 g) before digestion. Digested samples were first neutralized with NaOH  and H2SO4 (0.25 mol/l) was used as the titration solution subsequently. To determine the total protein concentration, a conversion factor of 6.25 × nitrogen (%) was applied  was determined using the Kjeldahl method . A Kjeld applied .Total lipids (%) were determined following the method of Bligh et al. . Samplesn = 5), four samples for megrim (n = 4), and three samples each for lemon sole (n = 3) and flounder (n = 3). As these fish are very lean and individual fish were limited in size, it was necessary to merge samples to obtain at least 0.02 g of lipids per sample. Samples from European plaice were not merged due to bigger fish sizes, and 6 individuals (n = 6) were chosen for analysis. Nitrogen evaporation was conducted at 30°C until all chloroform was removed from the samples, and 3 ml KOH in methanol (0.5 M) was added to the samples and vortexed to saponify the lipids. Samples were incubated in a water bath at 70°C for 20 min, vortexed, and cooled on ice. Afterwards, 5 ml of boron trifluoride-methanol  was added to allow acid-catalyzed esterification of the fatty acids. The samples were re-incubated in the water bath at 70°C for 5 min and cooled on ice. N-butyl acetate (2 ml) was added, and the samples were shaken. Subsequently, saturated NaCl (around 1.5 ml), and two spatulas of powdered sodium sulfate (Na2SO4) were added to the samples, and the samples were rested at room temperature (21°C) to allow phase separation. Around 0.5 ml of hexane was added, and the lipid phase was then pipetted out and filtered using a 0.2 μm PTFE membrane  into GC vials.Fatty acids were prepared as methyl esters for analysis by gas chromatography. For fatty acid methyl ester (FAME) preparation, the method of Metcalfe et al.  was usedThe FAMEs were analyzed by gas chromatography (GC) using a GC apparatus . The samples (2–3 μl) were introduced by an evaporation injector . Hydrogen was used as a carrier gas to pass the samples onto a polyethylene glycol column , where FAMEs were separated at different times along the stationary phase. A flame ionization detector (FID) adjusted to 310°C was used to detect the samples. The oven program was set to a constant temperature of 160°C for 3 min, with an increase of 3°C/min to 240°C and held for 3 min.Fatty acids were identified by comparing relative retention times (RRTs) of the external FAME standard mix containing 37 fatty acid methyl esters  with sample peaks. Chromatogram peaks, showing similar RRTs to the external standard were considered for determination. The intensity of each peak was calculated against the total intensity of FAMEs, to determine the percentage distribution of the individual fatty acids in each sample.Total amino acids were extracted from the samples following the method of Blackburn . Sampleso-phtalaldehyde (OPA) method was applied and the flow rate was adjusted to 0.9 ml/min. After passing through the column, the amino acids were detected by fluorescence and recognized by a Dionex RF2000 detector. Alpha-aminobutyric acid (Aba) was used as an internal standard. Three amino acids were not analyzed: cysteine, proline, and tryptophan. The amino acids glycine and arginine were co-eluted in the analysis.Both free and total amino acids were analyzed by ultra-high-performance liquid chromatography . As mobile phase, methanol and sodium acetate (0.08 M) with 2% tetrahydrofuran were applied. The HPLC was equipped with a Nova-Pak C18 column , a TSP P400 pump and an injection valve (ultimate 3000WP injector). A pre-column derivatization step using the 7H6O6S) to allow protein breakdown. The samples were shaken vigorously and placed in a fridge (4°C) for 30 min. After protein breakdown, the tubes were centrifuged for 10 min at 2700 g and 4°C . The supernatant containing the free amino acids was suitably diluted. The diluted samples were filtered through 0.2 μm polyethersulfone membrane filters and 0.205 ml of the samples were transferred to vials before performing HPLC analysis as described in section 2.4.1.Free amino acids were extracted from the samples following the method of Osnes et al. . Approxin = 2) were examined.For analyzing potentially elevated levels of contaminants in the samples, a variety of trace elements and polychlorinated biphenyls (PCBs) were chosen, and samples were pooled together. Each sample contained two individuals (three for European plaice) of same size, equally distributed and homogenized. Per species, two pooled samples  system was used. The system was linked to an autosampler . To test the accuracy of the analysis, certified reference materials (CRM) were used, namely MODAS-5  and MODAS-3 . The procedure of sample preparation, including microwave digestion and subsequent steps were previously described in detail by Kendler et al.  followinThe analysis for PCBs included PCB-3, 8, 28, 52, 101, 118, 138, 153, 180, 195, 206, and 209, including the ICES-6 PCBs  and the dioxin-like PCB 118. A GC–MS system  was employed to detect PCBs. The system included split liner injection, an inert mass selective detector  and a Thermo TG 5MS column . A detailed description of the procedure can be found in Kendler et al. . The samThe protein quality of a foodstuff can be determined by calculating the digestible indispensable amino acid score (DIAAS). For calculations on the quality of the distinct amino acid profiles of the five investigated fish species, the DIAAS as proposed by FAO  was consThe score is a product of the amino acid scoring pattern of the protein and the digestibility of these amino acids. The amino acid scoring pattern is related to how the amino acids in the protein correspond to the nutritional requirements set by FAO . A benefThe DIAA reference ratios can be calculated for each DIAA from the amino acid content and the ileal digestibility, as seen in Where:df: true ileal digestibility factor for specific amino acids in fish as proposed by FAO . When spreference protein: nutritional requirements set by FAO et al. .An estimation of the total amounts of fatty acids per 100 g edible fillet wet weight (ww) of the investigated species was conducted using Where:Weight% FAME: results from FAME analysis, assuming the same as weight%-FA since marine lipids mainly consist of long-chain fatty acids .FACF: fatty acid conversion factor (g FA/g lipid), from conversion factors proposed by Weihrauch et al.  calculatTLC: total lipid content as measured in g lipid per g fillet ww from the analysis on total lipids .α < 0.05 was conducted to find outliers in the data set. Data were analyzed using univariate analysis of variance (ANOVA) combined with Tukey HSD post hoc test when significance was detected to investigate the differences between groups. Statistical differences were reported at the level of α < 0.05. For flatfish representatives, analyses were carried out in 2 × 2 parallels  and are presented as means ± standard deviation (SD) if not other stated. For thornback ray, the same analyses were performed in duplicates.All statistical analyses were performed using Minitab 19p > 0.05). Hence, the data of the UB and LL fillets were combined, giving one mean value for each flatfish individual, which was further considered when presenting the results. This leads to the assumption that nutrients are equally distributed throughout the body regions of the investigated flatfish species. The findings correspond with our previous study on European plaice . The measured water content for megrim equaled the values found by Afonso et al.  and thornback ray (p < 0.001).The ash content of the four flatfish representatives was between 1.0–1.25%, while fillets from thornback ray (0.9%) showed lower values of inorganic material. This was in line with previous investigations on flatfish, although previous studies on thornback ray found slightly higher ash values (1.1–1.4%) for this species , 33. Ashp = 0.036), flounder (p = 0.003) and plaice (p = 0.024) with an average of 19.6%, being marginally higher than the studies by Barbosa et al. (p < 0.001). The measured protein content of thornback ray was not in correspondence with previous studies and was 4–5% higher than observed in studies by Colakoglu et al.  with 0.74% and thornback ray (p = 0.036) with 0.76% total fat content. The findings in this study show lower lipid contents for megrim (0.98%) compared to the study of Pastoriza et al.  were found for most of the amino acids between the five species. All species have a preferable distribution of indispensable amino acids (IAA), accounting for more than 50% of the TAA distribution. Megrim was found to have significantly higher amounts of IAA  compared to flounder (6.14 g/100 g), lemon sole (6.07 g/100 g), plaice (5.62 g/100 g), and thornback ray (5.88 g/100 g). Furthermore, megrim has comparably more total amino acids  than the other species. This was also found in three of the four species for the total protein content, with the exception of thornback ray, where an overestimated protein content is suspected. The amino acid determination by Blackburn  were investigated to determine the nutritional value of the proteins in the fish. The TAA results for the species are given in lackburn  directlylackburn . FurtherThe DIAA ratios were calculated and the DIAAS was calculated based on the DIAA ratios. The DIAA reference ratios are displayed in p = 0.114; Arg/Gly as combined values), threonine (p = 0.866) and methionine (p = 0.872). Lysine showed significant differences amongst the species (p < 0.001), with flounder and megrim having notably higher values. Flounder, lemon sole and plaice were identified to have significantly higher levels of histidine (p < 0.001), while megrim and thornback ray show comparatively low values of 0.51 and 0.84 mg/100 g sample, respectively. The most prevalent FAA are allocated in the group of “Sweet” amino acids with arginine/glycine having the highest content, followed by lysine and alanine.In addition to their nutritional importance, amino acids are associated with taste when occurring unbound in the form of free amino acids (FAA) in biological systems. Referring to the TAA and FAA distribution of the five investigated species, high variances within the species were observed, which is expressed by relatively large standard deviations as shown in The following sections (section 3.3 and 3.4) highlight the potential of the studied species as sources for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in human nutrition. Flounder, plaice and thornback ray were found to have significantly higher total PUFA compositions than megrim with 50.7, 47.2, and 49.3%, respectively, as can be seen in Although the studied fish are categorized as lean species, the fatty acid composition is of high importance. Health promoting effects due to prevention of cardiovascular diseases (CVD), tumor cell proliferation and inflammation processes as well as beneficial effects on brain, retina and neurodevelopment in children are primarily attributed to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) .The total EPA and DHA intake when consuming the five investigated species was calculated to highlight how the species contribute to providing these indispensable FAs to human diet. The contribution to the daily recommendations of 250 mg EPA and DHA by the EFSA Panel on Dietetic Products et al.  are showWith regards to EPA and DHA, all investigated fish species contribute significantly to the daily suggested intake of 250 mg by EFSA . The relp < 0.001), magnesium (p = 0.002) and iron (p = 0.047). High values in selenium, ranging from 0.25 mg kg−1 in thornback ray to 0.49 mg kg−1 in lemon sole were found in this study. Compared to the study of Karl et al.  is used. The DRV in this study refers to either the average requirement (AR), the population reference intake (PRI) or the adequate intake (AI), depending on the available data from the expert panel on Dietetic Products, Nutrition and Allergies from EFSA (p = 0.213) in selenium content between species was detected, an effect on the contribution to meet the DRV is visible, given as % of DRV. Hence, a 200 g fillet of lemon sole covers the selenium intake to 140%, whereas a 200 g fillet of thornback ray reaches only 74.3% of the daily selenium coverage. Moreover, all five species are a good source of potassium, covering around 20% of the DRV. Differences in species are visible for the magnesium contribution, where a 200 g portion of plaice covers 10% of the DRV and megrim contributes up to 16% of the daily recommended intake.Marine fish are good sources for both macro and trace elements, including minerals like calcium, magnesium or selenium, being vital for human health. All fish contain sufficient amounts of potassium (K) and magnesium as shown in l et al.  on differom EFSA . Even thPleuronoectiformes and Rajiformes are more likely to accumulate PCBs and hazardous trace elements than other fish species (p = 0.002), nickel (p < 0.001), cadmium (p < 0.001) and lead (p < 0.001). The highest accumulation of chromium and cadmium were found in thornback ray with 56.36 ± 29.12 μg kg−1 and 0.58 ± 0.05 μg kg−1 respectively. Large varieties within species can be seen for all elements, with particular great SD in the mercury content of plaice (112.9 ± 54.1 μg kg−1) and thornback ray (174.37 ± 169 μg kg−1). Despite differences between species as well as individuals, the maximum levels of cadmium (0.1 mg kg−1), lead (0.3 mg kg−1) and mercury (0.5 mg kg−1) set by the EC , Trondheim.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. 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Existing evidence concerning the relationship between daytime napping and type 2 diabetes (T2D) is inconsistent, and whether the effects of napping differ by body fat percentage (BFP) and C‐reactive protein (CRP) is unclear. We aimed to investigate the association between daytime napping frequency and T2D risk and whether such an association was modified by BFP and CRP.We included 435 342 participants free of diabetes from the UK Biobank. Participants were categorized as nonnappers, occasional nappers, and frequent nappers based on napping frequency, and BFP/CRP was divided into quartiles. Cox proportional hazards models were used.p for multiplicative interaction <.001) between napping and BFP, whereby a higher hazard of T2D associated with more frequent napping was greatest among participants in the highest BFP quartile . The results for CRP were similar .During a median follow‐up of 9.2 years, 17 592 T2D cases occurred. Higher frequency of daytime napping was significantly associated with an increased risk of T2D. Compared with nonnappers, the adjusted hazard ratios (HRs) for occasional nappers and habitual nappers were 1.28  and 1.49 (95% CI: 1.41–1.57), respectively. There was a significant additive and multiplicative interaction , and such relations are modified by body fat percentage (BFP) and C‐reactive protein (CRP) levels. The association between daytime napping and T2D risk is strongest among those with the lowest BFP and CRP levels, which provides implications for the development of T2D prevention strategies targeting the reduction in BFP and CRP levels among adults with napping habits. Subjects with longer napping durations were found to have an increased level of interleukin‐6,22.1www.ukbiobank.ac.uk).The UK Biobank is a large‐scale and prospective cohort study with over 500 000 participants aged 40–69 years recruited from 2006 to 2010 from across the United Kingdom (n = 28 410) and those with missing data on daytime napping (n = 1634), CRP (n = 30 141), or BFP (n = 6980) at baseline, leaving a total of 435 342 participants in the main analysis  never or rarely (< once per week), (b) sometimes (1–3 times per week), or (c) usually (≥4 times per week), where every category increase reflected more frequent napping. Prefer not to answer responses were set to missing.Blood samples were collected from the participants at the initial assessment center visit (2006–2010). CRP (mg/L) was measured by immunoturbidimetric high‐sensitivity analysis on a Beckman Coulter AU5800, glucose (mmol/L) was measured by hexokinase analysis on a Beckman Coulter AU5800, and glycosylated hemoglobin  was measured by high‐performance liquid chromatography analysis on a Bio‐Rad VARIANT II Turbo. Details on quality control and sample preparation have been described previously.Body composition measures of all participants were assessed by trained personnel using a standard protocol at enrollment. BFP was estimated using a Tanita BC418MA segmental body composition analyzer  according to the manufacturer's instructions. This device estimates body composition by conducting bioimpedance analysis. Both log (CRP) and BFP levels were treated as continuous variables. In addition, participants were grouped based on quartiles of log (CRP) and BFP to evaluate the effects of these variables on the association between daytime napping and incident T2DM.2.3International Classification of Diseases, Tenth Revision code E11.The UK Biobank algorithms2.4n (percentage) according to the frequency of daytime napping . The relationship between daytime napping and CRP levels, BFP levels, glucose levels, and HbA1c levels was evaluated using a general linear model. The associations of CRP, BFP, and daytime napping with incident T2D were investigated using Cox proportional hazard models. The proportional hazards assumption was tested using Schoenfeld residuals. Follow‐up time was calculated from the baseline date to diagnosis of T2D, death, loss to follow‐up, or censoring date , whichever came first.Baseline characteristics of the participants are described as the means (SDs) or HRFrequent nappers,highestBFP/CRPquartile−HRFrequent nappers,lowestBFP/CRPquartile−HRNonnappers,highestBFP/CRPquartile+1. The confidence intervals (CIs) for RERI were estimated using the standard delta method.Two approaches were used. First, separate associations of daytime napping and quartiles of CRP and BFP with incident T2D were investigated. CRP and BFP were also treated as continuous variables, and hazard ratios (HRs) per one SD increase in inflammation and adiposity were estimated. Second, joint associations between daytime napping, CRP, and incident T2D and between daytime napping, BFP, and incident T2D were evaluated. Daytime napping frequencies and quartiles for CRP and BFP were derived, and HRs were calculated, with the referent category comprising individuals who were in both the lowest frequency group of daytime napping (never/rarely) and the highest quartile of CRP or BFP. To investigate whether adiposity and/or inflammation moderated the association between daytime napping and the risk of incident T2D, we assessed the relative excess risk due to interaction (RERI) as an index of additive interaction. In our study, RERIs were defined for dichotomized exposures2), smoking status , alcohol consumption , physical activity , healthy diet (yes/no), family history of diabetes (yes/no), antihypertensive medication use (yes/no), cholesterol medication use (yes/no), aspirin use (yes/no), and nonaspirin nonsteroidal anti‐inflammatory drug (NSAID) use (yes/no). A healthy diet was defined as an adequate intake of at least four of seven commonly eaten food groups recommended as dietary priorities for cardiometabolic healthSeveral potential confounders were adjusted in the models described: age (continuous), sex , race (white and others), UK Biobank assessment center, Townsend deprivation index (continuous), average total annual household income , BMI , physical activity (<600 MET min/week or ≥ 600 MET min/week), healthy diet (yes or no), sleep duration , smoking status , alcohol consumption status , Townsend deprivation index (<median or ≥ median), family history of diabetes (yes or no), aspirin use (yes or no), and nonaspirin NSAID use (yes or no). Sleep duration was based on the following standardized question: “Approximately how many hours do you sleep every 24 h?”, for which responses were given in hours (https://bbams.ndph.ox.ac.uk). Sleep duration information was considered to be missing if participants failed to answer or had a sleep duration <4 or > 18 h to reduce the possibility of an implausible sleep duration. Based on the classification proposed by the National Sleep Foundation,n = 6242) or HbA1c levels ≥48 mmol/mol  to address the issues of potential undiagnosed diabetes at baselinen = 18 254)n = 116 095); andWe performed a stratified analysis to evaluate potential modification effects according to the following factors: sex , race , age (<55 or ≥ 55 years), BMI . All statistical tests were two sided, and 33.1Table After adjustment for a set of covariates, daytime napping frequencies showed a significant positive association with glucose, HbA1c, BFP and CRP levels at baseline . After further adjustment, the HRs were 1.28 (95% CI: 1.24–1.32) and 1.49 (95% CI: 1.41–1.57) among occasional nappers and habitual nappers, respectively.During a median of 9.2 years of follow‐up (4 013 849 person‐years), 17 592 incident cases of T2D were identified. Kaplan–Meier curves of incident T2D demonstrated a significant, incremental increase in rates of incident T2D associated with increasing frequency of daytime napping , participants with a high level of HbA1c (≥48 mmol/mol [6.5%]), participants who developed T2D within 2 years of follow‐up or participants who took any anti‐inflammatory drugs or after adjusting for glucose levels, fasting time, HbA1c levels, or CRP levels (Supplementary Tables p for interaction <.001), White and Black individuals (p for interaction = .011), younger participants  and obese participants .We also conducted stratified analyses according to potential T2D risk factors to evaluate whether these factors modified the association between daytime napping and the risk of T2D , a one‐SD increase in CRP levels (1.1 mg/L) was associated with a 40% increase in the risk of incident T2D (95% CI: 37%–42%), and a one‐SD increase in BFP (8.5%) was associated with a 69% increase in the risk of incident T2D (95% CI: 64%–75%).We first evaluated the separate associations between inflammation, adiposity, and risk of incident T2D. Table p for multiplicative interaction = .009; Figure p for multiplicative interaction = .089), a similar additive interaction  was observed . These results remained materially unchanged after performing several sensitivity analyses . Finally, causality cannot be determined because of the observational nature of this study, and randomized clinical trials are needed to verify our findings. However, we deemed that this criticism could be assuaged to some extent, given that several previous prospective cohort studies and Mendelian randomization have consistently reported positive associations of daytime napping with obesity and T2D but not vice versa,6In summary, the present prospective population‐based cohort study of 435 342 people indicates that a higher frequency of daytime napping is associated with an increased risk of incident T2D, and such relations are modified by BFP and CRP levels. These findings may have implications for the development of T2D prevention strategies targeting the reduction in BFP and CRP levels among older adults with napping habits.Rui Zhou designed the study, performed the statistical analysis, interpreted the data, and drafted and critically revised the manuscript; Hao‐Wen Chen helped perform the analysis with constructive discussions and contributed to the interpretation of the results; Yi‐Ning Huang, Qi Zhong, and Fu‐Rong Li contributed to data preparation; Rui‐Dian Huang, Hua‐Min Liu, Jia‐Zhen Zheng, and Jia‐Wen Xu contributed to the interpretation of the results and critical revision of the manuscript; Xian‐Bo Wu conceived and designed the study and contributed to the supervision and project administration of the manuscript. All authors approved the final manuscript. The corresponding author had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.No potential conflicts of interest relevant to this article were reported.Appendix S1. Supporting InformationClick here for additional data file.


Small tyrosine kinase inhibitors (TKIs) show activity against breast cancer brain metastases (BCBM) of the human epidermal growth factor receptor 2 (HER2)‐positive subtype. This meta‐analysis aimed to objectively explore the efficacy and safety of TKIs.Electronic databases were searched for relevant clinical trials. We conducted a pairwise meta‐analysis, pooled analysis, and estimated summary survival curves to compare survival outcomes following TKIs therapy for BCBM patients using Stata version 16.0 or R x64 4.0.5.p = 0.132), although the difference is not statistically significant. Summary survival curves reported the summary median PFS and overall survival were 7.9 months and 12.3 months. Subgroup analysis revealed that TKIs combined with capecitabine (TKI + Cap) regimens resulted in improved survival outcomes. Tucatinib may be more effective in BCBM patients. The main grade 3–5 adverse events (AEs) were diarrhea , neutropenia , hepatic toxicity , and sensory neuropathy .Thirteen clinical trials involving 987 HER2‐positive BCBM patients were analyzed. A trend of longer progression‐free survival (PFS) was observed in the TKI‐containing arm compared to the non‐TKI‐containing arm (hazard ratio = 0.64, 95% confidence interval [CI]: 0.35–1.15, TKIs therapy improved the survival outcomes of HER2‐positive BCBM patients, especially when combined with capecitabine and tolerable AEs. We also identified the clinical value of tucatinib, which appears to be the most favorable TKI drug for BCBM patients. Unfortunately, the time to intracranial progression after these therapies is approximately 6–12 months.The use of small‐molecule tyrosine kinase inhibitors (TKIs), which inhibit both HER2 and EGFR targets, may improve patient outcomes.A debate is ongoing over the use of TKIs for treating HER2‐positive BCBM owing to a lack of sufficient clinical evidence, mainly a preponderance of results from single‐arm clinical trials and existing randomized controlled trials (RCTs) that reported mixed results. Questions have also been raised owing to differences in the baseline characteristics of patients in various clinical trials. In addition, there is no consensus on the optimal combination drug with TKIs and the TKI drug with better efficacy. A complete analysis of all relevant clinical studies is important to provide useful clinical references. Therefore, we conducted this meta‐analysis using the latest data to provide a comprehensive overview of TKIs therapy for HER2‐positive BCBM patients.2inplasy.com (https://doi.org/10.37766/inplasy2021.7.0064). The protocol for this systematic review and meta‐analysis has not been previously published in peer‐reviewed journals.Our study was registered on INPLASY (INPLASY202170064) and the details are available at 2.1We developed the eligibility and exclusion criteria for this study in advance. All clinical trials  investigated TKI regimens for the treatment of HER2‐positive BC patients with brain metastases. A subgroup analysis of patients with brain metastases within relevant trials was also performed in our study. Survival or tumor response data were available for all patients. The studies were grouped based on treatment regimens, regardless of active or inactive brain metastases, treatment lines, or prior treatment. Phase II or III clinical trials published as full papers or abstracts if full papers were not available  were included in the analysis. Case reports, systematic reviews, and retrospective studies were excluded from the analysis. In case of multiple publications from the same trial, only the most recent publication was included.2.2This meta‐analysis followed the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines. Searches were performed on PubMed, Embase, and Cochrane Central Register of Clinical Trials, utilizing the following keywords: “(breast OR mammary) AND  AND  AND (positive OR +) AND  AND (metastasis OR metastases OR metastatic) AND ”, only in English, without any limitations on factors such as time or race. We also assessed the ASCO and ESMO annual meetings and SABCS online articles, and included articles published before January 1, 2023. The references of all studies that met the eligibility criteria were examined for other relevant studies, especially for relevant meta‐analyses.2.3Two investigators (YSY and JZ) independently extracted the data, and all included items required consensus. The first author, year of publication, trial name, locations, trial phase, number of analyzed participants, therapy regimens, therapy details, Eastern Cooperative Oncology Group Performance Status, and the efficacy endpoints of each eligible trial were recorded. The primary outcome was progression‐free survival (PFS). The secondary outcomes were CNS ORR, median PFS, median OS, and grade 3–5 adverse events (AEs). All data were recorded from the original articles or using the GetData Graph Digitizer if the original statistical curve pictures were acquired from the articles.2.4Outcome analyses, including PFS, CNS ORR, median PFS, and median OS, were conducted based on the investigator‐assessed response according to RECIST 1.1. The data have also been corrected and are indicated in the Characteristics of the Trials. Neutropenia, vomiting/nausea, diarrhea, stomatitis mucositis, skin and subcutaneous tissue disorders, sensory neuropathy, and hepatic toxicity were considered as the most crucial side effects. Grade 3–5 AEs were calculated using the National Cancer Institute Common Terminology Criteria version 4.0.2.5We conducted a pairwise meta‐analysis to evaluate PFS as hazard ratios (HRs) with corresponding 95% confidence intervals (95% CI) between TKI‐containing and non‐TKI‐containing regimens using available data. Owing to limited data, single‐arm trials were also included in our study to better describe the efficacy of TKIs in BCBM patients. Because no HRs or risk ratios could be produced with these single‐arm studies, we conducted them in three steps to better demonstrate their effectiveness. First, we attempted to estimate tumor response and survival results using a pooled analysis from a quantitative perspective. Continuous variables, including median PFS and median OS, are presented as pooled mean values. Dichotomous variables, including CNS ORR and grade 3–5 AEs incidence rates, were presented as pooled effect sizes with 95% CIs. Second, to indicate the analysis of time survived to an outcome event that cannot be reflected in pooled analysis, a R package entitled MetaSurv was used to estimate “summary survival curves” from single‐arm studies' K‐M curves by the product‐limit estimator method, then the summary median survival can be calculated based on the summary survival curve.I2 statistic. We used a fixed‐effects model for the analysis if the pooled results showed low heterogeneity (I2 ≤ 50%). Conversely, a random‐effects model was used for significant heterogeneity (I2 > 50%). Begg's and Egger's tests were used to examine the potential publication bias of the included clinical trials. All statistical analyses were performed using Stata version 16.0 or R x64 4.0.5, and statistical significance was set at p < 0.05.Cochran's Q chi‐square test was used to examine the heterogeneity across studies, and inconsistencies were tested using the 2.6The study quality of the five included RCTs was assessed using the Cochrane risk of bias tool. Eight single‐arm studies were assessed using the MINORS index scored.2.7The patients and the public were not involved in the design, conduct, reporting, or dissemination plans of our research.33.1The initial search revealed 670 potentially relevant manuscripts and one additional abstract. After a detailed review of the titles and abstracts, 548 manuscripts were excluded. The full texts of the remaining 123 articles were read, and a total of 14 articles from 13 trials—including five RCTs and eight single‐arm clinical trials that met the requirements—were obtained according to the inclusion and exclusion criteria  as calculated by the random‐effects model.Five RCTs compared the HRs of PFS compared TKI‐containing regimens with non‐TKI‐containing regimens. The pooled analysis results are provided in Figure 3.3.2I2 = 95.71%, p < 0.001), as calculated using the random‐effects model with high heterogeneity . While TKI + Cap‐containing regimens subgroup showed an obviously higher summary median PFS time of 9.1 months   with TKI‐containing regimens treatment  in TKI + Cap‐containing regimens subgroup  Figure . The OS t Figure . While fp Figure .I2 = 0.00%)  Figure  compared) Figure . As Lapa) Figure . However) Figure . In conc3.4We generated grade 3–5 AEs that occurred most frequently during treatment, including neutropenia, vomiting/nausea, diarrhea, stomatitis, mucositis, skin and subcutaneous tissue disorders, sensory neuropathy, and hepatic toxicity. In general, the pooled analysis results showed that the safety outcomes of the TKI‐containing regimens were acceptable. The common toxicities with grade 3–5 AEs during treatment with TKI‐containing regimens included diarrhea , neutropenia , hepatic toxicity , and sensory neuropathy . Compiled grade 3–5 AEs in HER2‐positive BCBM patients are shown in Figure 4Survival outcomes of patients with HER2‐positive BC have greatly improved with the availability of additional treatment approaches. However, an increase in the incidence of CBM has been reported over the last few years. This may be due to the combination of poor penetrability of the BBB to chemotherapy drugs, monoclonal antibodies, and antibody‐dependent cell‐mediated cytotoxicity (ADCC) drugs, allowing the CNS to become a “shelter” for cancer cells, and advanced medical imaging technology becoming better at detecting brain metastatic lesions.The presupposition for disease control and overall efficacy in treating CBM is adequate target engagement and drug penetration into the brain and tumors.Subgroup analysis showed that the TKI + Cap regimens had a more substantial benefit with a favorable CNS ORR of 43% compared with that of TKI (monotherapy) (5%) and TKI + Others (11%) and produced longer median PFS and OS. These results are consistent with those of a phase II trial that assessed lapatinib efficacy and reported a CNS ORR of 6%. Of the 50 patients who entered the capecitabine extension phase, 20% achieved an objective CNS response.The TKIs available for clinical practice or under investigation mainly include lapatinib, neratinib, afatinib, pyrotinib, and tucatinib. However, the optimal treatment for HER2‐positive BCBM remains controversial. We performed a subgroup analysis to explore the efficacy of the different TKIs. Owing to limited data, we could not perform any summary analysis apart from Lapatinib‐containing regimens. However, the HER2CLIMB showed significantly better outcomes of a tucatinib‐containing regimen of 9.9 months for PFS and 18.1 months for OS compared with those of lapatinib‐containing regimens of 5.90 months for PFS and 12.99 months for OS.89Zr‐trastuzumab was detected in brain lesions at an 18‐fold higher concentration than that in normal brain tissue, which supports the feasibility of HER2‐targeting therapy in patients with BCBM.HER2‐targeting antibody therapies, including trastuzumab, trastuzumab emtansine (T‐DM1), trastuzumab deruxtecan (T‐DXd), and pertuzumab, were discovered in a medical history. Generally, they have limited roles in treating BM as first‐line therapy because of the BBB. However, recent studies have suggested the opposite view, as some clinical trials have shown that large‐molecule drugs can be effective treatments for BCBM.To our knowledge, this study is the first to assess the efficacy and safety of TKI‐containing regimens for the treatment of HER2‐positive BCBM. Our meta‐analysis included five RCTs and eight single‐arm clinical trials of high quality and integrity. A pairwise meta‐analysis was performed to compare the efficacy of TKI‐containing regimens and non‐TKI regimens. Pooled analyses and summary survival curves obtained from single‐arm studies provided quantitative and intuitive results. However, trial design discrepancies between different studies can account for the high heterogeneity of pooled analyses in single‐arm studies. Subgroup analysis was used to reduce heterogeneity and yielded reliable results.5TKI therapy improves the survival outcomes of HER2‐positive BCBM patients, especially when combined with capecitabine and tolerable AEs. We also paid attention to the clinical value of tucatinib, which appears to be the most favorable TKI drug for BCBM patients.Yushuai Yu: Conceptualization ; data curation ; formal analysis ; methodology ; writing – original draft . Kaiyan Huang: Formal analysis ; methodology ; writing – original draft . Yuxiang Lin: Methodology ; writing – review and editing . Jie Zhang: Data curation ; methodology ; writing – original draft . Chuangui Song: Conceptualization ; writing – review and editing .This study was not supported by any financial or personal relationships with other people or organizations.The authors have declared that no competing interests exist.This article does not include studies with human participants conducted by any author.As this study contained data released from the published literature, informed consent was not required.Table S1Click here for additional data file.Appendix S1Click here for additional data file.Appendix S2Click here for additional data file.Figure S1Click here for additional data file.Figure S2Click here for additional data file.Figure S3Click here for additional data file.


Guan X, Ma F, Xu B. Pooled analyses of randomized controlled trials on pyrotinib plus capecitabine and a rethink of the first‐line options for HER2‐positive relapsed or metastatic breast cancer. Cancer Innovation.2022;1‐5.In the funding information, the Grant/Award Number of National Nature Science Foundation of China was incorrect. The Grant/Award Number should be “82103634”.We apologize for this error.


Myeloid‐derived suppressor cells (MDSCs) are an immature group of myeloid‐derived cells generated from myeloid cell precursors in the bone marrow. MDSCs appear almost exclusively in pathological conditions, such as tumor progression and various inflammatory diseases. The leading function of MDSCs is their immunosuppressive ability, which plays a crucial role in tumor progression and metastasis through their immunosuppressive effects. Since MDSCs have specific molecular features, and only a tiny amount exists in physiological conditions, MDSC‐targeted therapy has become a promising research direction for tumor treatment with minimal side effects. In this review, we briefly introduce the classification, generation and maturation process, and features of MDSCs, and detail their functions under various circumstances. The present review specifically demonstrates the environmental specificity of MDSCs, highlighting the differences between MDSCs from cancer and healthy individuals, as well as tumor‐infiltrating MDSCs and circulating MDSCs. Then, we further describe recent advances in MDSC‐targeted therapies. The existing and potential targeted drugs are divided into three categories, monoclonal antibodies, small‐molecular inhibitors, and peptides. Their targeting mechanisms and characteristics have been summarized respectively. We believe that a comprehensive in‐depth understanding of MDSC‐targeted therapy could provide more possibilities for the treatment of cancer. Myeloid‐derived suppressor cells play a crucial role in tumor progression and metastasis through their immunosuppressive effects. In different environments and conditions, these cells vary in mechanisms of immunosuppressive functions. Since only a small amount exists in physiological conditions, myeloid‐derived suppressor cell‐targeted therapy has become a promising research orientation for tumor treatment with minimal side effects. In recent years, various kinds of targeted drugs against myeloid‐derived suppressor cells have been developed, as a novel way of cancer treatment. Various diseases develop along with immune system dysfunctions. In steady‐state conditions, myeloid precursors in the bone marrow eventually differentiate into monocytes and neutrocytes, maintaining a normal and well‐balanced immune status. However, under some pathological processes, such as tumor progression, myeloid cells can abnormally differentiate into immature cells named myeloid‐derived suppressor cells (MDSCs).CD14 and CD15 expression differs between these types, which is a key feature for distinguishing them.MDSC, a kind of cell that mainly accumulates in a few situations, such as cancer and chronic inflammations,In tumor progression, MDSCs can be generated and activated via complex molecular mechanisms and then recruited into the TME to perform protumoral functions, which is modulated mainly by CXC motif chemokine receptor (CXCR) 2.Since MDSCs have multiple mechanisms promoting tumor progression, MDSC‐targeted therapy appears to be a promising treatment for malignant tumors. Another notable peculiarity of MDSCs is that they are present in small quantities under healthy and physiological conditions. Therefore, therapy targeting MDSCs may reduce damage to normal tissues, side effects are expected to be averted.This review first presents the essential characteristics of MDSCs to briefly introduce them. Then, it describes the functional features of MDSCs in various conditions and classifies them based on their molecular mechanisms. This review mainly highlights the environmental specificity of MDSC, including the differences between tumor‐infiltrating and circulating MDSCs and between MDSCs from patients with cancer and healthy donors. The following section summarizes and emphasizes MDSC‐targeted drugs and therapies, hoping to provide researchers and clinical workers with guidance and insights into a new target in cancer therapy.22.1In the bone marrow, myeloid cells can be briefly classified into two groups (granulocytes and mononuclear cells), which primarily contribute to the body's immune reaction. MDSCs are pathologically and immaturely differentiated from myeloid precursors (granulocytic and monocytic cell lines) and are divided into the two main populations as mentioned above (PMN‐MDSCs and M‐MDSCs).2.2Myeloid cells in the bone marrow differentiate into mature neutrophils and monocytes in response to acute inflammatory stimulations, such as pathogenic invasion. Those differentiating into monocytes subsequently generate macrophages and dendritic cells (DCs) to provide protection and manifest a proinflammatory activity.MDSC accumulation from myeloid progenitor cells in vivo comprises two stages: immature myeloid cell expansion and pathological activation.In the second stage, besides inflammation‐promoting factors, such as IL‐1β and tumor necrosis factor (TNF)‐α, and some other mediators, MDSCs can also be activated by a specific highly conserved mechanism—endoplasmic reticulum stress.The immature differentiation of granulocytes in the bone marrow usually leads to the generation of PMN‐MDSCs. However, Mastio et al. showed that a branch of cells from the monocytic lineage could differentiate into PMN‐MDSCs.2.3+ Gr‐1+. Movahedi et al.+ Ly6G+Ly6Clow and M‐MDSCs as CD11b+ Ly6G− Ly6Chigh+CD33+, but have discrepant CD14 and CD15: while PMN‐MDSCs and neutrophils are CD11b+CD14−CD15+ CD66b+ CD33+, M‐MDSCs and monocytes are CD11b+CD14+CD15− CD66b− CD33+ 5. However, density gradient is a distinguishing indicator of PMN‐MDSCs and neutrophils,Different MDSC subtypes in mice share the same molecular features as CD11b+ cells in tumor tissues could be marked as MDSCs.In the TME, more features of MDSCs with specificity have been identified. Lectin‐like oxidized low‐density lipoprotein receptor 1 (LOX1), a kind of transmembrane glycoprotein with a mass of 50 kDa, is defined as a specific marker of PMN‐MDSCs,Notably, the current definition and classification methods for MDSC subsets are based on the immune suppressive functions and surface markers. However, MDSCs have more complex heterogeneity and plasticity, and a more integrated definition and classification of MDSCs should focus on the differences in immunosuppressive mechanisms .3As previously mentioned, MDSCs rarely exist under healthy conditions in humans. Under tumor progression, MDSCs can form during tumor progression, leading to their expansion and discrepant quality. Therefore, it is essential to find out how MDSCs differ in different sites so that they can be targeted more accurately. Since the differences between mature myeloid cells and MDSCs and between MDSC subpopulations have already been detailed in other reviews,3.1ARG‐1, IDO, IL10, and iNOS expression was higher in MDSCs from patients with cancer than from healthy donors.The number of MDSCs was significantly larger in patients with cancer than in healthy donors.3.23.2.1+HLA−DR−/lowCD14−CD15+,high can be acquired from peripheral blood.+ HLA‐DR−/low CD14+ CD15−low.MDSCs primarily form in the bone marrow but can also be induced by tumor‐related cytokines in peripheral blood from peripheral blood myeloid cells. The phenotypic characteristics of MDSCs vary in the tumor site and peripheral blood in patients with different tumors. In patients with non‐small‐cell lung cancer (NSCLC), PMN‐MDSCs obtained from tumor tissue were CD11b3.2.2In some cancer types, there are more tumor‐infiltrating MDSCs than MDSCs in peripheral organs.3.2.3CAT2), ARG‐1, and nitric oxide synthase 2 (NOS2) expression, decreasing l‐arginine production, increasing nitric oxide (NO) production, and enhancing the detrimental effects on T cells.HIF1α) expression increases in the tumor environment due to hypoxia, enhancing PD‐L1 expression in MDSCs.CCL) 3, CCL4, and CCL5 expression to recruit regulatory T cells (Tregs) via chemokine–CCR5 interactions  and PGE2 expression in TAMs, leading to their dysfunction. Substantial increases occur in memory and effector CD8+ T cells and natural killer (NK) cells due to upregulation of IL‐2‐ and TNF‐α‐associated inflammatory signaling and suppression of oxidative phosphorylation.Tumor‐infiltrating PMN‐MDSCs but not M‐MDSCs or circulating PMN‐MDSCs were recently found to induce spontaneous ferroptosis, one basis of their immunosuppressive ability. Ferroptosis is the dominating cell death pattern in tumor‐infiltrating PMN‐MDSCs, causing tumor progression.3.3S100A9), a chemokine strategic for MDSC migration,Some studies have artificially induced circulating MDSCs using cytokines, such as GM‐CSF, IL‐1, IL‐6, VEGF, TNF‐α, and PGE2, which differ from noninduced MDSCs.3.4Circulating MDSCs in patients with cancer and premalignant conditions share the same composition and function but with larger amounts in cancer environments.4MDSCs play a vital immunosuppressive role in various pathological processes, especially in all kinds of tumors and TMEs. Herein, we orderly introduce the specific functions of MDSCs in a physiological situation, inflammation, and tumor progression.4.14.1.1+ PMN‐MDSCs in all stages of pregnancy, which correlated negatively with intrauterine growth retardation.ARG‐1, or functioning through cell contact. Moreover, MDSCs appear in neonates for a transient period.Bone marrow‐derived myeloid cells usually differentiate into mononuclear cells and granulocytes.4.1.2Staphylococcus aureus (S. aureus), a large number of MDSCs were found in the surrounding bacterial biofilm, contributing to the persistence and low clearance of S. aureus, by secret iNOS, ARG‐1, as well as IL‐10 to inhibit the infiltration of immune cellsS. aureus will upregulate formate acetyltransferase (pflB) to form a larger and more pervasive biofilm.Schistosoma japonicum, MDSCs are also able to increase the expression of PD‐L1, modulating the immunoactivity of T cells via the PD‐1/PD‐L1 pathway.The roles of MDSCs in chronic and acute infectious diseases have been elucidated in recent years, whose immunosuppressive ability promotes the progression of these infectious diseases, and the detailed mechanisms of MDSCs acting on individual diseases were summarized by several reviews.+ and CD8+ T cells while promoting the expansion of Tregs and HIV infection.In virus infections, since the acquired immune deficiency syndrome is characterized by immune deficiency, the role of MDSCs after human immunodeficiency virus (HIV) invasion has been widely explored. For one thing, MDSCs will inhibit the proliferation of CD44.1.3+ T cell proliferation  and infiltration and the proinflammatory cytokine production by CD4+ T cells, restrict B cell proliferation and antibody production , promote Treg cell proliferation (via IL‐10 generation), as well as stimulate IL‐10+ Breg cell generation .ARG‐1, contributing to SLE‐related renal injury.Rheumatoid arthritis (RA) is a systemic, cartilage‐and‐bone‐destructive autoimmune disease of which immune cell infiltration and accumulation in the synovial joints have a vital role in the pathogenesis,4.1.4As a kind of therapeutic tool, MDSCs can be used for immunosuppression in organ transplantation for beneficial utilization. Acute graft‐versus‐host disease (GVHD) is the most substantial threat among organ transplant recipients, and MDSCs play a positive role in transplantation immune tolerance, reducing the incidence of GVHD.4.1.5Another possible direction is to apply MDSCs in anti‐inflammatory therapy. Various substances can induce MDSC production in vivo or in vitro Table . Xu et a+ M‐MDSCs with a stronger immunosuppressive activity.As mentioned above, MDSCs can be used when treating inflammation‐related diseases in multiple organs in three ways: first, endogenous MDSCs are able to be increased by inducing their formation or inhibiting continued differentiation. For example, rapamycin can inhibit MDSC differentiation and improve heart failure.4.24.2.1The role of MDSCs in the TME mainly involves inhibiting of T cell activation. The direct effects of MDSCs are principally to reduce the expression of specific recognition receptors on the T cells’ surface and to promote T cell apoptosis. Their indirect effect is to regulate the T cells’ proliferation and differentiation by changing the microenvironment's physical and chemical components.MDSCs can produce large amounts of ROS and reactive nitrogen species (RNS), which inhibit the activation of the Janus kinase (JAK) 3/STAT5 signaling pathway, downregulating the expression of MHC‐II molecules and inhibiting T cell apoptosis.+ T cells into Tregs by releasing of cytokines or cell‐to‐cell contact and Treg proliferation.IDO overexpression by MDSCs causes Tregs migrate to tumor sites and lymph nodes.+ T cells by decreasing aspartate, serine, and glycine synthesis and reducing the dominating aggressor granzyme and perforin. Itaconate can serve as a promising cancer therapy target and a tumor prognosis biomarker.Besides their impact on the death of proinflammatory T cells, MDSCs can also directly mediate T cells’ generation, differentiation, and migration of T cells. MDSCs inhibit the generation and proliferation of tumor antigen‐specific T helper 1 cells by producing IL‐6.M‐MDSCs can degrade arginine by secreting ARG‐1 and RNS. When arginine is competitively consumed in the microenvironment, the T‐cell‐receptor ξ chain and CD3 expression on T cells’ surface is downregulated, and the expression of cyclin D3 (CCND3) and cyclin‐dependent kinase 4 (CDK4) is inhibited, inducing T cell cycle arrest in the G0/G1 phase.4.2.2The inhibitory effect of MDSCs on immune cells is also manifested in macrophages. MDSCs are involved in activating of TAMs and promoting the conversion of M1 to M2/TAM.S100A9 expression, but most monocyte‐derived macrophages or tissue‐resident macrophages do not. The difference in S100A9 expression indicates that the presence of S100A9 in macrophages is critical to its inhibitory activity.While TAMs and MDSCs are regarded as independent entities, the boundary between them is unclearly demarcated, and they have many common features.4.2.3MDSCs recruit suppressive immune cells by expressing TGF‐β, VEGF, fibroblast growth factor 2 (FGF2), MMP9, IL‐10, PD‐L1/2, IDO, iNOS, and ARG‐1 and establishing a microenvironment that suppresses host immunity by expressing suppressive cytokines  and surface molecules .bFGF) to help tumor cells build new vascular systems and deliver nutrients and oxygen to cancer cells.The nonimmunosuppressive functions of MDSCs include tumor angiogenesis and metastasis.VEGF and CXCR expression in tumor cells,PMN‐MDSCs can secrete proangiogenic factors.Notably, unlike the formation of blood vessels under physiological conditions, tumor blood vessel formation has a disorganized structure and a discontinuous and incomplete vessel wall.In addition, VEGF secreted by MDSCs directly effects on cancer cells or tumor stem cells. It may induce cancer cell proliferation and promote tumor‐initiated cell self‐renewal by activating VEGFR1 signaling.TGF‐β is secreted by various tumor cells and is closely associated with tumor growth and immunity.MDSCs induce EMT in tumor cells via the TGF‐β signaling pathway. They can secrete multifunctional proteoglycans to induce EMT in cancer cells via the TGF‐β signaling pathway,TGF‐β is also involved in downregulating the expression of the killer cell lectin‐like receptor K1 (KLRK1/NKG2D) on the NK cell surface,MYC/c‐Myc).PD‐L1 and ARG‐1 expression and NO and ROS production, increasing MDSC function.MDSCs induce the differentiation of regulatory B cells and regulatory DCs2+ influx, immune cell recruitment, and inflammatory processes+ MDSCs to secrete cellular effectors, such as IL‐10, TGF‐β, NO, and ARG molecules that inhibit hematopoiesis and promote T cell tolerance as well as myelosuppression and inflammation.MDSCs also secrete chemokines, such as S100 calcium‐binding proteins A8 (S100A8) and S100A9, which are actively transported to the TME and distant tissues via exosomes secreted by tumor‐associated immune cells .MDSCs also express ectonucleoside triphosphate diphosphate hydrolase 1 (ENTPD1/CD39) and 5’‐nucleotidase ecto (NT5E/CD73). CD39 catabolizes adenosine triphosphate to adenosine diphosphate/adenosine monophosphate (AMP), while CD73 mediates the subsequent catabolism of AMP to adenosine. Their expression and activity are elevated in tumor tissue and blood and are frequently associated with clinical signs of disease and poor prognosis in some cancers.IL‐1 is an inflammatory cytokine that plays a key role in tumorigenesis and progression. It is a key mediator of natural and acquired immunities and is involved in multiple pathways related to microbial recognition, activation, and functional localization of lymphocytes. IL‐1 plays different roles in tumorigenesis and progression by influencing different components of the TME.PD‐1/ PD‐L1 expression. Malignant tumor cells suppress the immune function of T lymphocytes through pathways such as PD‐1/PD‐L1 pathway to weaken their recognition by the immune system and evade immune surveillance, achieving immune escape and prolonging the life span of tumor cells. NF‐κB also regulates TNF‐α and epidermal growth factor receptor (EGFR), forming a positive feedback regulatory loop between them to promote tumor cell proliferation.IL‐1α/IL‐1 receptor signaling is located upstream of nuclear factor kappa B (NF‐κB),Both IL‐1α and IL‐1β promote tumor angiogenesis and invasion,Altogether, MDSCs in the TME can induce immunosuppressive functions in various ways: affecting T cells’ generation, differentiation, migration, proliferation, and viability; inducing M2 polarization of macrophages; mediating the status of NK cells and DCs; recruiting other immunosuppressive cells; inhibiting self‐differentiation; and promoting tumor cells’ progression, EMT, and metastasis of tumor cells to construct a tumor‐promoting inflammatory environment Figure .5MDSC‐targeted drugs in cancer therapies can be divided into mAbs, small‐molecular inhibitors, and peptides based on their chemical structure. In this section, we summarize studies of MDSC‐targeted drugs and introduce their applications and mechanisms. These targeted drugs can achieve anti‐MDSC effects by inhibiting MDSC functions, inhibiting MDSC recruitment into the TME, restraining myelopoiesis or MDSC development, inducing MDSC differentiation, inhibiting dedifferentiation into MDSCs, and mediating MDSC depletion Figure .5.15.1.1PD‐1 is a self‐protective protein receptor expressed on the surface of immune cells (mainly T cell). PD‐L1 is its corresponding ligand on the surface of multiple cells, including hematopoietic and tumor cells.In the study conducted by Tzeng et al.,LGALS9), the ligand of hepatitis A virus cellular receptor 2 (HAVCR2/TIM3), are correlated with reduced CD8+ T cell secretion. Pretreatment with anti‐TIM3 could be an effective approach for reducing resistance to nivolumab, a type of PD‐1 blockade, in patients with NSCLC.Patients suffering from various cancers (such as melanoma and NSCLC) easily showed undesired or poor clinical effects after receiving anti‐PD‐1/PD‐L1 treatment due to drug resistance.5.1.2Whether MDSCs express CTLA‐4 remains unclear.5.1.3+ M‐MDSCs increasing in abundance in patients with tumor progression. Undesirable anti‐VEGF therapeutic effects may be attributed to increase GM‐CSF levels after treatment, which mediate MDSC migration and differentiation.SET domain‐containing 2 histone lysine methyltransferase (SETD2/HIF‐1) and VEGF are abundantly activated in tumor sites, enhancing angiogenesis, which also induces MDSC migration to and differentiation at tumor sites.5.1.4While the modulating pathways between the EGFR and MDSCs are unclear, studies have observed changes in MDSCs after interfering with the EGFR.5.25.2.1Sunitinib is a type of receptor protein‐TKI (RPTKI) with multiple targets, including VEGFR, ret proto‐oncogene (RET), and KIT proto‐oncogene receptor tyrosine kinase (KIT/c‐Kit),+ T cells into the TME.Other TKIs have also shown anti‐MDSC efficacies. Stiff et al. showed that ibrutinib, a type of Bruton's TKI, could weaken NO and IDO production in MDSCs and MDSC cytopoiesis and migration.5.2.2Chemokines are important mediators in tumor progression. The CXCR–CXCL system can induce immune cell infiltration, tumor proliferation, metastasis, and angiogenesis.5.2.3CRBN expression in MDSCs from naïve and tumor‐bearing individuals is necessary. Kuwahara‐Ota et al.IRF8 expression and downregulating CCR5 in peripheral blood mononuclear cells in vitro. Notably, the multiregulatory mechanism of lenalidomide could also increase CD14+CD15+ MDSCs, causing T cell suppressive effects.Immunomodulatory drugs (IMiDs), consisting of lenalidomide and pomalidomide, are a group of antitumor drugs derived from the prototype compound thalidomide that can be used for some hematologic tumors, especially multiple myeloma.5.2.4+ Tregs.IDO1 expression and assisted in tryptophan catabolism partly via the STAT3/NF‐κB/IDO pathway, which forms positive feedback.hi DCs, and reversing the accumulation of Treg‐like cells.Tryptophan is an essential amino acid required that is taken in through diet, and tumor burden is associated with tryptophan catabolism. Initially, this kind of catabolism, which results in the depletion of tryptophan, is controlled by IDO and tryptophan dioxygenase. Tryptophan starvation suppresses T cell growth and activation, promoting tumor immune escape, metastasis, and angiogenesis.5.2.5PD‐L1 expression and MDSC and Treg infiltration.+ Gr‐1+ MDSCs in pancreatic cancer by almost 50% via two distinct delivery routes: oral administration and a targeted nanoparticle‐encapsulated approach. Nanoparticle usage doubled the half‐life of IPI‐549 and ensured drug accumulation in the tumor site, but the MDSC concentration did not significantly differ between the two distinct routes, suggesting that the anti‐MDSC effects of IPI‐549 may be dose‐independent. Additionally, the dual PI3K/mechanistic target of rapamycin kinase (mTOR) inhibitor dactolisib downregulated the oxidative phosphorylation of MDSCs.+ Gr‐1+ MDSC recruitment at tumor sites.Once activated by upstream signals from receptor tyrosine kinases, phosphoinositide‐3‐kinases (PI3Ks) will lead to several key regulations in tumor‐associated immunity.5.2.6ARG‐1 and iNOS expressions are mediated by STAT6/IL‐4 receptor alpha (IL‐4Rα), and PDE5 inhibitors can affect outcomes by reducing of IL‐4 Rα in the upstream pathway.+ MDSCs decreased by 5.6% in patients with end‐stage multiple myeloma after 11 months of treatment with tadalafil. Given its influence on MDSC function, IL‐4Rα expression markedly decreased from 51.37 to 2.13% after treatment, and both IL‐4Rα and ROS levels were restored to baseline.Phosphodiesterase (PDEs) are common metallohydrolases downstream of cyclic‐AMP and cyclic‐GMP that induce the inactivation of both secondary messengers. Among the 11 subtypes of PDEs, PDE5 has a cGMP‐specific hydrolytic function.5.2.7Vorinostat, entinostat, and ricolinostat are histone deacetylase (HDAC) inhibitors that promote histone acetylation, transforming gene expressions via epigenetic reprogramming.5.2.8PGE2 is an inflammatory cytokine that tumors secrete to create a local proinflammatory microenvironment.5.2.9+ T cell proliferation and CD8+ T cell‐mediated direct tumoricidal effects.Colligan et al.5.32) does not induce MDSC mobilization in peripheral blood and recruitment to the tumor site.+ T cell activation.Tumor‐targeting peptide is a state‐of‐the‐art research direction for tumor‐related targeted treatments. Peptides are notable for their small molecule mass, synthetic convenience, and good biocompatibility compared with proteins. The peptides used to target MDSCs, or broadly the TME can be divided into two categories: (1) those without antitumor efficacies used only in targeted combinations of specific receptors, and 2) those with specific antitumor functions. The first group of peptides functions as carriers of antitumor drugs. The pharmacological actions of antitumor drugs can be achieved via specific binding to superficial, intracellular, or intranuclear receptors. Most studies have focused on delivering drugs to tumor cell surfaces or targeting vascular endothelial cells to block tumor nutrient sources. FAM‐A54, selected by phage display approaches, has shown binding specificity for diverse liver cancer cell lines with the potential binding motif of Pro‐Ser. A54‐covered doxorubicin has shown a high absorptivity in cancer cells. those wi5.4Previous studies have revealed that drug‐resistant tumors are especially sensitive to ferroptosis, indicating the promising effect of ferroptosis in tumor therapy.6MDSC is a kind of immunosuppressive cell which plays a vital role in various inflammatory diseases and tumor pathogenesis, progression as well as metastasis. Several studies have described the characteristics of MDSCs, dividing them into subtypes and elaborating on their functions in pathological conditions. Under most inflammatory circumstances, their immunosuppressive capacity can worsen inflammation progression. But in some scenarios such as hyperinflammation and autoimmune diseases, inhibiting autologous immune response is beneficial to disease prognosis. Besides, MDSCs were surprisingly proven to have some proimmune functions as well as nerve system regeneration promoting capacities in autoimmune diseases, indicating that MDSC cannot be merely considered as an immunosuppressive cell, and further investigations of its potential functions are necessary. Applying the immunosuppressive property of MDSCs to treat inflammation through in vitro MDSC induction and amplification is another novel field that draws much attention. A number of studies have already achieved artificial MDSC induction by adding cytokines, and the process is accessible theoretically. However, how to systematically induce high‐quality anti‐inflammatory MDSCs at a low cost remains unclear.MDSCs have a critical role in transforming TME into a protumoral environment, and the main mechanism is to modulate the proliferation and functions of multifarious immune cells. In the current literature, we have summarized the various immunosuppressive functions of MDSCs and the corresponding mechanisms, and we finally established an integrated MDSC interaction network based on previous research results. However, the explorations on MDSC generation, differentiation, and functional mechanisms are still insufficient. Future work is required and is vital to improve clinical antitumor treatment.Anti‐MDSC effects have recently shown for many targeted antitumor drugs, including some widely used mAbs, small‐molecular inhibitors, and peptides. And we have generalized their functions into five issues: (1) inhibiting MDSC functions, (2) inhibiting MDSC recruitment into TME, (3) restraining myelopoiesis or MDSC development, (4) inducing MDSC differentiation or inhibiting dedifferentiation into MDSCs, and (5) mediating MDSC depletion. Our summary will provide comprehensive references and instructions for clinical drug applications. However, the detailed mechanisms behind the clinical benefits of MDSC‐targeted therapy are poorly understood for most drugs. Further studies should evaluate drug‐MDSC interaction modes, including direct/indirect targeting, or outcomes of secondary tumor‐targeted changes. Since only a small amount of MDSCs exist under steady‐state and normal conditions, MDSC‐targeted therapy can be much less harmful to healthy tissues and cells than traditional chemotherapies, which therefore prevents severe side effects during anticancer treatments.In the future, after further investigation into MDSCs and their mechanisms in the immune microenvironment, MDSC‐targeted anticancer therapy and MDSC‐based anti‐inflammatory treatment may be finally applied.B. S. and R. Y. R. designed the project. R. Y. R., C. Y. X., R. Y. M., and Y. X. W. drafted the manuscript. R. Y. R., C. Y. X., R. Y. M., Y. X. W., and T. Y. Y. finished the search of data for the article. B. S., R. Y. R., and J. Y. Y. revised and finalized the manuscript. All authors read and approved the final manuscript.The authors declare that they have no competing interests.Not applicable.


Factors predicting the response to pembrolizumab plus platinum and pemetrexed combination therapy (Pemb‐Plt‐PEM) in nonsquamous non‐small cell lung cancer (non‐sq NSCLC) are unclear. We investigated the Glasgow Prognostic (GP) score, neutrophil‐to‐lymphocyte ratio (NLR), and body mass index (BMI) as predictors of response to initial treatment with combination therapy in individuals with advanced non‐sq NSCLC.We retrospectively reviewed 236 patients who received initial treatment with combination therapy for non‐sq NSCLC at 13 institutions between December 2018 and December 2020. The usefulness of the GP score, NLR, and BMI as prognostic indicators was assessed. Cox proportional hazard models and the Kaplan–Meier method were used to compare progression‐free survival (PFS) and overall survival (OS).p = 0.0002; OS: 29.4 vs. 12.0 months, p < 0.0001). BMI predicted the treatment response—individuals with BMI ≥22.0 kg/m2 had longer OS than did those with BMI < 22.0 kg/m2 .The response rate was 51.2% (95% CI: 44.9–57.5%). The median PFS and OS after beginning Pemb‐Plt‐PEM were 8.8 (95% CI: 7.0–11.9) months and 23.6 (95% CI: 18.7–28.6) months, respectively. The NLR independently predicted the efficacy of Pemb‐Plt‐PEM—the PFS and OS were more prolonged in individuals with NLR <5 than in those with NLR ≥5 .The NLR independently predicted the efficacy of Pemb‐Plt‐PEM—the PFS and OS were more prolonged in individuals with NLR <5 than in those with NLR ≥5 (PFS: 12.8 vs. 5.3 months,  The highest number of deaths related to cancer is attributed to lung cancer; the death rate is higher for lung cancer than for colon, breast, or prostate cancer.Pembrolizumab (Pemb), a monoclonal IgG4 antibody that targets the PD‐1 receptor, has been investigated for use in cancers, including NSCLC.Distant metastases are often present when NSCLC is diagnosed. In advanced stages, weight loss and systemic inflammatory responses (SIRs), including cancer cachexia, may occur.Previous studies have reported that SIR‐based markers predict the treatment efficacy of ICIs. Indeed, the NL ratio predicted the outcome of ICI treatment in individuals with skin,Body mass index (BMI) might be a predictor of prognosis in malignancies. BMI is also used as a measure of sarcopenia, which correlates with adverse prognosis in individuals with NSCLC who receive ICIs.Currently, limited data are available regarding the relationship of the GP score, NL ratio, and BMI with the effectiveness of frontline combined chemoimmunotherapy for individuals with non‐sq NSCLC. Furthermore, first‐line Pemb‐Plt‐PEM is frequently used in patients with non‐sq NSCLC, but none of them have been studied. We aimed to evaluate whether these factors predicted the effectiveness of initial Pemb‐Plt‐PEM in individuals with non‐sq NSCLC.We retrospectively analyzed the efficacy of first‐line Pemb‐Plt‐PEM treatment for non‐sq NSCLC at 13 Japanese institutions (December 2018 to December 2020). The study participants (1) had non‐sq NSCLC at inoperable disease stage III/IV or postoperative recurrent disease, which was diagnosed with histological or cytological analysis and (2) had undergone initial Pemb‐Plt‐PEM treatment.There were 248 consecutive individuals who were administered Pemb‐Plt‐PEM; among them, 11 with druggable driver gene mutations/translocations received molecular targeted therapy as first‐line treatment. One individual had a significant amount of missing data. Overall, 236 individuals were included in the study  systemThe design of the current study was approved by the Institutional Ethics Committee of the International Medical Center, Saitama Medical University . The study followed the institutional and national ethical standards and the Declaration of Helsinki (2013 revision). No animal experiments were performed. Because of its retrospective design, patient informed consent was not obtained. However, the opt‐out method was available to refuse participation in the study.2 body surface area) or carboplatin , according to the investigator's discretion, plus PEM (500 mg/m2) up to six cycles, all administered intravenously every 3 weeks, followed by PEM (500 mg/m2) and 200 mg of Pemb every 3 weeks. The premedication consisting of folic acid, vitamin B12, and glucocorticoids was administered based on each institution's treatment protocol. In some individuals, Pemb or PEM was omitted from the Pemb and PEM maintenance therapy, dependent on the treating physician's decision. Treatment was discontinued if progressive disease developed, irreversible toxicity was noted, or the individual withdrew their consent to receive anticancer therapy.Individuals with a history of receiving ICIs, including the Pemb‐Plt‐PEM regimen, were not present in the current analysis population. The basic therapeutic regimen consisted of Pemb (standard dose of intravenous 200 mg on day 1 of each cycle), intravenous cisplatin  has thresholds of ≥5 and <5.2]) was assessed before the start of Pemb‐Plt‐PEM administration. We evaluated the potential correlation between BMI and Pemb‐Plt‐PEM effectiveness based on a BMI cutoff value of 22.0 kg/m2, that is, the ideal BMI for the Japanese population2, respectively).BMI .t‐test, respectively, in subgroups defined by the GP score, NL ratio, and BMI. Cox proportional hazard models with stepwise regression were used to evaluate factors predicting PFS and OS. The hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated. Univariate and multivariable logistic regression analyses were undertaken for different outcomes. Kaplan–Meier survival analysis was performed to estimate survival, whereas survival was evaluated using the log‐rank test. Two‐tailed p < 0.05 indicated statistical significance. Statistical analyses were performed using JMP software for Windows, version 11.0 (SAS Institute).Categorical and continuous variables were analyzed using Fisher's exact test and Welch's n = 236). Table Table p < 0.05).The characteristics of the GP score, NL ratio, and BMI subgroups are demonstrated in Table p < 0.05).The NL ratio at the start of Pemb‐Plt‐PEM administration was categorized as low  or high . The median age at treatment, PS, bone metastases at the start of treatment, BMI, prior radiotherapy, number of Pemb‐Plt‐PEM administration cycles, serum CRP and albumin levels, neutrophil and lymphocyte counts, and disease control rate were related to the NL ratio values .The pretreatment BMI was low and high in 114 and 122 individuals, respectively. Sex and the number of maintenance therapy administration cycles, serum CRP level, albumin concentration, and lymphocyte count were related to the BMI  months Figure  and 23.6p < 0.0001) and bone metastases at initial treatment  were related to worse PFS, whereas a low (<5) NL ratio was related to prolonged PFS . The multivariable analyses also showed that a PS of 0–1  and low (<5) NL ratio  correlated with better OS, whereas PD‐L1 TPS < 50% , bone metastases at initial treatment , and low (<22.0 kg/m2) BMI  correlated with shorter OS.The multivariable analysis demonstrated that PD‐L1 TPS < 50% , it was not significantly different between them and those with BMI < 22.0 kg/m2  than with BMI < 22.0 kg/m2 .2, that is, the ideal BMI for Japanese individuals; however, whether this is an appropriate cutoff value should be investigated in a future analysis, given the presence of variance related to differences in ethnicities and populations. Furthermore, BMI is influenced by various factors, including natural body size, genetic factors, tumor progression, the presence of cachexia, and psychological factors. We suspect that BMI contains many confounding factors. Therefore, even with multivariable analysis, it is difficult to identify the relationship between BMI and treatment efficacy or OS independently.A large retrospective cohort study suggested that a high BMI was related to better PFS and OS after ICI treatment of advanced melanoma.Our study has some weaknesses. First, this retrospective study depended on subjective assessments of tumor responses that might have led to errors in the recorded data related to treatment responses and PFS. Second, as there are no absolutely established cutoff values for the GP score, NL ratio, and BMI, we used cutoff values from previous studies. It will be important to examine whether the findings of the current analysis are clinically appropriate for other and larger cohorts in the future.In summary, our findings suggest that the NL ratio is independently correlated with PFS and OS. Additionally, BMI is independently correlated with OS. Large‐scale studies should examine the generalizability of our findings. Although future analyses are required to confirm these results, our findings indicate that determining the NL ratio and BMI may help predict the efficacy and prognosis of individuals with advanced non‐sq NSCLC treated with initial Pemb‐Plt‐PEM treatment.Conceptualization and methodology, H.I. and K.K. (Kaira); Formal analysis and data curation, H.I. and K.K. (Kaira); Project administration, visualization, and writing—original draft preparation, H.I.; Supervision, K.K. (Kaira) and H.K.; Investigation and resources, S.W., T.T., Y.N., T.K., K.M., T.O., Y.M., Y.U., A.O., H.M., Y.Y., J.N., Y.K., H.T., H.O., and T.K.; Writing—review and editing, all authors.All authors have approved the final manuscript. All authors had full access to the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. No potential conflict of interest exits.Data S1. Supporting InformationClick here for additional data file.