In turn, S1P acts as a double edge sword in the retina. It is essential for retina development, promoting the survival of photoreceptors and ganglion cells and regulating proliferation and differentiation of photoreceptor progenitors. However, S1P has also deleterious effects, stimulating migration of Müller glial cells, angiogenesis and fibrosis, contributing to the inflammatory scenario of proliferative retinopathies and age related macular degeneration (AMD). C1P, as S1P, promotes photoreceptor survival and differentiation. Collectively, the expanding role for these sphingolipids in the regulation of critical processes in retina cell types and in their dysregulation in retina degenerations makes them attractive targets for treating these diseases.The sphingolipids ceramide (Cer), sphingosine-1-phosphate (S1P), sphingosine (Sph), and ceramide-1-phosphate (C1P) are key signaling molecules that regulate major cellular functions. Their roles in the retina have gained increasing attention during the last decade since they emerge as mediators of proliferation, survival, migration, neovascularization, inflammation and death in retina cells. As exacerbation of these processes is central to retina degenerative diseases, they appear as crucial players in their progression. This review analyzes the functions of these sphingolipids in retina cell types and their possible pathological roles. Cer appears as a key arbitrator in diverse retinal pathologies; it promotes inflammation in endothelial and retina pigment epithelium (RPE) cells and its increase is a common feature in photoreceptor death  Sphingolipids entered the group of Bioactive Lipids about three decades ago; however, they are still regarded by many as newcomers, less familiar than the phosphatidylinositol phosphates, prostaglandins or leukotrienes. Yet, the overwhelming amount of literature accumulated evidences that simple sphingolipids such as Cer, Sph, and their phosphorylated derivatives, S1P and C1P  have takFirst identified in the brain by Thudichum in the late 19th century, for virtually another century their functions remained as enigmatic as the Sphinx their name honors. Being lipid molecules, they were considered as ubiquitous membrane components both in animal and plant cells for several decades. Even just as such, they have multiple and relevant roles. They are crucial constituents of lipid rafts and regulate their formation and expansion, essential for building signaling platforms ; they arThese bioactive lipids respond to a diversity of cell stimuli by modifying their intracellular levels, thus regulating multiple signaling pathways that finally induce major changes in cell fate. Their roles have strikingly extended to include virtually every aspect of cell biology, from cell cycle, differentiation, endosome and exosome formation, adhesion and migration to angiogenesis, immune response, inflammation and cell death, including autophagy and apoptosis. Recent advances have revealed that sphingolipid mediators play important roles in human disease.This Review focuses on the functions played by simple sphingolipids in the retina during development and particularly in the onset of retina pathologies. Lipids have long been known to be essential for maintaining both the structure and functionality of the visual system. Docosahexaenoic acid (DHA) has been shown to promote photoreceptor survival and differentiation, and docosanoids, such as Neuroprotectin D1, and elovanoids have relevant neuroprotective roles in the retina . ConversThe sphingolipid family encompasses a huge diversity of molecular species that place them among the major lipid classes in eukaryotic cells. Sph, a straight, long chain (18–20 carbon atoms) aminoalcohol, is the common backbone shared by all these species . Attachmde novo synthesis, degradation of sphingomyelin (sphingomyelinase pathway) and recycling of Sph and complex sphingolipids . De novo synthesis begins in the ER  shift SPT preference to use alanine and glycine instead of serine  % of both rat and bovine retinal lipids . SM is tDiverse studies confirm the earlier observations that the sphingolipid profile is modified in retinal pathologies. Cer mass content decreases in retinas from diabetic mice compared to normal retinas, without modifying its fatty acid composition, with a concomitant increase in GlucoCer, and no changes in Sph and SM . The relin vivo and in vitro has contributed to our understanding of these roles. In vivo studies with animal models have provided comprehension on the biological functions of sphingolipids and allowed to test the physiological effects of modulating its levels. Research in vitro has allowed dissecting their specific effects on particular cell types and the biochemical pathways involved in these effects. We will now highlight the findings that support that significance of sphingolipids during normal development and in pathologies affecting the retina.The fact that sphingolipids are affected during the course of degeneration intuitively makes them likely candidates to have a role in retinal diseases. A combination of studies Cer has a central role in the sphingolipid family, both structural and metabolic. Consisting in a Sph molecule bound to a fatty acid of 16 to 24 carbons length , these ltrans Golgi region, to generate SM, involves a CERT, which carries it in a non-vesicular manner  appear as novel players in the modulation of sphingolipid metabolic enzymes. Work from the Busik laboratory showed miR-15a participates in the regulation of Cer levels; its expression is decreased by high glucose whereas its overexpression downregulates acid SMase expression in human RPE cells, restoring normal Cer levels . This adAcid SMase activation has been shown in aged RPE and in a Stargardt disease mouse model, and the consequent Cer increase impairs autophagic flux, which is crucial for preserving functional RPE and photoreceptor cells . Efficie2O2 and UV radiation induce ER and stress-activated protein kinase (AMPK) axis, which promote RPE cell death , and a long-chain sphingoid base backbone (Sph) . Sph is 1-5. Most cells express one or more subtypes of S1PRs, and depending on the G-protein they are coupled with, S1PRs exhibit unique properties and regulate different cellular processes. Downstream effectors of S1PRs include adenylate cyclase, PI3-kinase, phospholipase C, protein kinase C and intracellular calcium  inhibitor to epigenetically regulate gene transcription , cytopla calcium . In addi calcium .Sphingosine-1-phosphate is a pleiotropic bioactive lipid mediator; its cellular concentration responds to different stimuli and is tightly regulated. Concentrations of S1P in blood and lymph are actually higher than in tissues . The finSphingosine-1-phosphate induces a wide spectrum of cellular effects, including proliferation, differentiation, survival, migration, angiogenesis and immune responses . These pde novo synthesis of Cer . S1P has been linked to microglial activation; S1P addition to cultured microglial cell lines increases the release of pro- inflammatory cytokines whereas microglial activation activity . Astrocyactivity . S1P1 exactivity .Inflammation, angiogenesis, proliferation and migration are common features in most retinopathies; hence, S1P signaling of these processes makes it an ideal candidate to regulate the onset and progression of these diseases. We will here discuss current knowledge regarding the role of S1P in eye and retina development and during retina pathological disorders, particularly the opposing functions of S1P in both neuronal survival and inflammation and fibrosis in the retina.SphK1 is low in most mouse ocular tissues and highest in the retina and optic nerve, whereas higher levels of SphK2 are observed in all mouse eye tissues. Interestingly, both SphK2 and SphK1 increase in the retina during early development, peaking at adulthood. S1p1 and S1p3 are expressed in the retina, while expression of S1p2 and S1p5 is minimal; S1P3 expression remains high and constant during retina development, whereas S1P1 increases gradually. Photoreceptors express both S1P1 and S1P3; S1P1 is highly expressed in RPE cells while S1P3 is localized in ganglion cells , nuclear factor NF-κB (NF-κB) and glucogen synthase kinase 3 (GSK3) . C1P proMounting evidence points to different roles for C1P in the nervous system. A 5-fold increase in C1P levels in the subventricular zone in Huntington disease patients has been reported, with no associated changes in Cer levels; this increase might represent a response to the chronic brain damage in these patients and might either reflect an attempt at neuroprotection and enhanced neurogenesis or contribute to neuroinflammation and neurodegeneration . C1P hasDrosophila eye revealed an indirect effect of Drosophila ceramide kinase (DCerK) in phototransduction. DCerK is an integral membrane protein that phosphorylates Cer, thus decreasing its levels .Higher levels of C12-, C16- and C24-C1P, and of C16- and C18-Cer have been found in retinas in a rat model of endotoxin-induced uveitis, together with increases in TNF-α and IL-6 levels, suggesting these sphingolipids might participate in the inflammation process . OngoingCeramide-1-phosphate functions in the retina are just starting to be uncovered. Existing evidence points to a crucial role of C1P in photoreceptor functionality, promoting their proliferation, survival and advancing differentiation. It might also be involved in modulation of phototransduction. Its contribution to inflammatory and proliferative pathologies of the retina has to be further explored.de novo synthetic pathway, had long been considered as an inactive sphingolipid, since its exogenous addition had little effect on cell death (Dihydroceramide, the immediate precursor of Cer in the ll death . Howeverll death . DHCer all death . Therefoll death .Drosophila eye leads to DHCer accumulation, increased ROS production and loss of photoreceptor functionality and viability; in turn, blocking DHCer synthesis preserves their viability (In the eye, early work showed distinct effects between Cer and DHCer. Cer induces cell death in cultured rat photoreceptors and amacrine neurons, in human RPE cells, in human corneal stromal fibroblasts and in lens epithelial cells, whereas addition of DHCer has no deleterious effect in these cell types . Howeveriability . Furtherde novo synthesis or by SM breakdown activates different downstream pathways leading to cell death. Cer buildup, due to an activation or increased expression of SMases is also crucial in the onset of RPE cell death and inflammation. Preventing Cer increase through the inhibition or modulation of different enzymes of its intricate metabolism has been shown to effectively prevent photoreceptor and RPE cell death, both in vivo and in vitro, and preserve visual function. These findings underscore both the relevance of imbalances in Cer levels as inducers of RPE and photoreceptor cell death and the significance of modulation of the sphingolipid metabolism as a therapeutic strategy for the treatment of retina neurodegenerations. Having an integral picture of the functions of Cer in the retina and of the effects of preventing its accretion demands establishing the processes regulated by Cer in glial cells and its potential role in their gliotic response. Several questions remain to be answered in order to accomplish the fine tuning of the highly interconnected sphingolipid metabolism, which is crucial for the development of new treatments for retinal pathologies. The complexity of this metabolism makes its modulation a powerful approach for preserving vision function but might also be an Achilles’ heel, jeopardizing strategies based on the inhibition of one of the metabolic pathways leading to Cer synthesis. Being Cer the central molecule in sphingolipid metabolism, the effects of blocking a single pathway established as crucial in generating Cer accumulation in a particular pathological circumstance should be explored. This inhibition might efficiently reduce cell death but impair other key, Cer-dependent, retinal processes or affect them indirectly, through the increase in bioactive sphingolipid metabolites. As blocking a certain biosynthetic pathway for Cer has been shown to provide a transient protection, it is critical to explore whether altering the flux through the network activates alternative Cer biosynthetic pathways and/or leads to the accumulation of bioactive sphingolipids, such as Sph or DHCer, which might trigger cell death. Further research aimed at understanding these balances and connections in a comprehensive molecular way might contribute to devising successful treatments based in new or already established drugs or suggest the necessity of combining different drugs in order to simultaneously modulate these metabolic processes.Sphingolipids emerge as crucial mediators in the activation of numerous pathways that might either activate neuroprotective mechanisms or whose dysregulation might lead to retina dysfunction. Cer stands out as a key messenger in the onset of degeneration in photoreceptors induced by oxidative stress and in numerous models of retina neurodegeneration; its increase through Modulation of the sphingolipid rheostat might provide clues for preventing the death of photoreceptors . NeverthMS wrote and edited the manuscript and contributed to the design of the figures. FPS wrote and edited the manuscript and contributed to the design of the figures. MV wrote the manuscript. NR designed the manuscript and figures and wrote and edited the manuscript.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.


The unconventional secretion of proteins is generally caused by cellular stress. During the tumorigenesis, tumor cells experience high levels of stress, and the secretion of some theoretically intracellular proteins is activated. Once in the extracellular space, these proteins play different paracrine and autocrine roles and could represent a vulnerability of cancer. One of these proteins is the high mobility group A1 (HMGA1), which is frequently overexpressed in tumors and presents a low expression in normal adult tissues. We have recently described that HMGA1 establishes an autocrine loop in invasive triple-negative breast cancer (TNBC) cells. The secretion of HMGA1 and its binding to the receptor for advanced glycation end products (RAGE) mediates the migration, invasion, and metastasis of TNBC cells and predicts the onset of metastasis in these patients. In this review, we summarized different strategies to exploit the novel tumorigenic phenotype mediated by extracellular HMGA1. We envisioned future clinical applications where the association between its change in subcellular localization and breast cancer progression could be used to predict tumor aggressiveness and guide treatment decisions. Furthermore, we proposed that targeting extracellular HMGA1 as monotherapy using monoclonal antibodies, or in combination with chemotherapy and other targeted therapies, could bring new therapeutic options for TNBC patients. In the last decade, the profiling of the cancer secretome has been widely used as a tool for biomarker discovery projects, as well as for the study of different aspects of cancer biology and therapeutics ,2,3,4. TThe omics profiling in cancer research is generally performed by genomics and transcriptomics analysis. However, the cancer secretome is more accurately measured using proteomic techniques, considering that levels of messenger ribonucleic acid (mRNAs) and proteins codified by genes that give rise to the secretome have shown a poor correlation . Our labWe decided to study a nuclear protein called the high mobility group A1 (HMGA1) out of the group of non-classical secreted proteins since it was significantly over-secreted from invasive breast cancer cells. HMGA1 is a chromosomal protein that binds to the minor groove of Adenine-Thymidine (AT)-rich deoxyribonucleic acid (DNA) strands through its three AT-hooks and controls the transcriptional activity of several genes by interacting with the transcription machinery . HMGA1 iHMGA1 is often overexpressed in tumor tissues, and this overexpression frequently correlates with the presence of metastasis and reduced patient survival [Despite gene mutations or rearrangements are rare in malignant solid tumors, survival ,21,22,23survival ,27,28,29survival . In the following section, we had focused on the most intriguing results of our work and how they could provide new opportunities to understand the role of HMGA1 in cancer biology. These results are summarized in The over-secretion of HMGA1 by invasive breast cancer cells opens the possibility that HMGA1 establishes new molecular interactions in the extracellular space that could complement its function as a transcriptional regulator in tumor cells. Another HMG protein, the high mobility group B1 (HMGB1), also previously known as HMG-1 and amphoterin, can also be secreted from both tumor and immune cells. In fact, HMGB1 can either be passively released or actively secreted from several cell types, including different immune and tumor cells ,32,33. WThe secretion of HMGB1 can be triggered by different cellular insults that lead to cellular stresses and death, and it is also associated with cell migration ,37. BothThe study by immunofluorescence of the HMGA1 expression and localization in breast cancer cells that secrete the protein led us to detect an accumulation of HMGA1 in the cytoplasm of these cells. Although the cytoplasmic localization was faint compared to its nuclear levels, we were able to show that the detection of the cytoplasmic localization of HMGA1 was a surrogate of its secretion. In a personal communication, Dr. Raymond Reeves, who pioneered the biochemical and molecular studies of HMGA1, brought to our attention that his laboratory had previously described a cytoplasmic localization of HMGA1. In these studies, the Reeves’ lab uncovered a dynamic, cell cycle-dependent translocation of HMGA1 proteins from the nucleus into the cytoplasm and mitochondria of NIH3T3 cells . HoweverRAGE is a member of the immunoglobulin receptor superfamily . Under nThe binding of ligands to RAGE elicits cellular responses, activating different cellular signaling pathways, including nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB), mitogen-activated protein kinase (MAPK), and the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) . SeveralIn our recent report, we added HMGA1 to the list of ligands of RAGE . We demoHMGA1 is an oncogene, mediating neoplastic transformation [Mounting evidence accumulated for two decades has suggested an oncogenic role for HMGA1. Since the mid-nineties, various reports proposed that ormation ,55,56,57ormation ,59,60. Iormation ,63,64,65ormation . Escherichia coli was not fully functional due to the lack of PTMs. Nevertheless, our experiments proved that extracellular HMGA1 was able to mediate migration and invasion in tumor cells. In our research, we demonstrated that the over-secretion of HMGA1 by invasive breast cancer cells could somehow mediate the invasive phenotype of these cells . The firRAGE gene is a close relative to other genes coding for adhesion receptors belonging to the cell adhesion molecules (CAMs) family [Regarding the molecular mechanism by which extracellular HMGA1 mediates a pro-invasive phenotype, we demonstrated that extracellular HMGA1 regulated adhesion of TNBC cells. Upon identifying extracellular HMGA1 as a ligand of RAGE in TNBC cells, we determined that extracellular HMGA1 induced a decreased adhesive phenotype in invasive breast cancer cells. The ) family . Therefore, based on our results, we considered that an autocrine loop of HMGA1-RAGE was responsible for increased mobility of tumor cells, and therefore an enhanced migratory ability. We believed that the increased adhesion occurring when extracellular HMGA1 was blocked was, at least, partially responsible for the decreased migratory phenotype observed. However, a mechanistic explanation of how extracellular HMGA1 could impact tumor invasion is not yet known. We could not rule out that adhesion, migration, and invasion would need the coordinated effort of both the nuclear and the extracellular form of HMGA1. In addition to the cell-autonomous processes described in In our experiments, both the ablation of HMGA1 expression and the blocking of the extracellular form with a specific antibody clearly decreased the incidence of metastasis in our xenograft model . AlthougTogether with the preclinical experiments, we were able to show a correlation between the subcellular localization of HMGA1 in primary tumors from TNBC patients and the incidence of distant metastasis . In thisHMGA1 gene mutations are rarely identified in solid tumors, gene amplification is more frequent; consequently, HMGA1 protein is widely overexpressed in different tumor types, as previously mentioned in Ever since the discovery of the upregulation of HMGA1 in tumors, several reports have identified HMGA1 as a candidate tumor biomarker. Although This protein overexpression in tumors, together with its low expression in normal adult tissues, makes HMGA1 an excellent target for drug development, as well as an ideal biomarker of tumor progression. However, its lack of enzymatic activity and the nuclear localization of this protein have seriously hampered the therapeutic options based on HMGA1. Fortunately, the novel tumorigenic phenotype mediated by HMGA1 in the extracellular space, in conjunction with the observed association between the change in subcellular localization of HMGA1 and breast cancer progression, opens a number of applications in a wide range of settings, including prognostic assessment, monitoring treatment response, and development of new anticancer therapies . β-catenin complex at the plasma membrane sustains the integrity of epithelial tissue morphology [β-catenin, which is found in the cytoplasm and nucleus in a large number of tumors. In the nucleus, β-catenin becomes a transcription factor that plays a key role in the abnormal activation of the Wnt signaling pathway. The nuclear localization of β-catenin measured by immunostaining has been used for the diagnosis of endometrial cancer, and it has been associated with poor prognosis in different types of cancer, including colorectal, non-small cell lung, and hepatocellular carcinoma [The change in the subcellular localization of several proteins is relevant for the outcome prediction in different tumor types. In this way, the subcellular localization of beta-catenin is one of the clearest examples of how the subcellular localization of a protein can be important for cancer prognosis. The E-cadherin/rphology . The dysarcinoma ,86,87,88arcinoma ,90,91. Farcinoma . Finallyarcinoma . Howeverarcinoma . This apRegarding HMGA1, although our initial study only included a small number of patients, the subcellular localization of HMGA1 in primary triple-negative breast tumors seems to be significantly correlated with the development of distant metastasis . Based oTherefore, it would be necessary to confirm that HMGA1 could predict tumor aggressiveness and also guide treatment decisions by measuring the protein levels and analyzing the subcellular localization of HMGA1 in the primary tumors of a large cohort of TNBC patients with and without metastatic involvement. Moreover, the evaluation of this function in other breast cancer subtypes and even in additional cancer types, including colorectal, pancreatic, and ovarian, in which HMGA1 is also highly expressed, merits additional investigation.Different studies have reported that both HMG and S100 proteins could be used as biomarkers of therapeutic response in cancer patients. In the case of HMGB1, changes in the levels of circulating HMGB1 have been associated with the response to neoadjuvant therapy in breast cancer patients . The oveIn breast cancer, the levels and subcellular localization of HMGA1 could be also useful to evaluate the antitumor efficacy and monitor the response to a specific therapy in TNBC patients. Based on these results, it is required to assess, either prospectively or retrospectively, the changes in the levels and/or subcellular localization of HMGA1 in TNBC patients treated with chemotherapy. This could be preferably performed using the neoadjuvant setting through the evaluation of the changes in the levels and/or subcellular localization of HMGA1 assessed by immunofluorescence between the pretreatment core biopsy and an on-treatment biopsy or the post-treatment surgical specimen. A change in the levels and/or subcellular localization of HMGA1 could help to identify those patients who derive more benefit from the neoadjuvant treatment. In the metastatic scenario, a setting more limited by the availability of paired tumor samples, it would be very appropriate to analyze the changes in the levels and/or subcellular localization of HMGA1 in circulating tumor cells (CTCs). The detection of changes in the subcellular localization and or the levels of HMGA1 in CTCs could offer the potential to more accurately predict patient outcomes than classical tumor response assessment methods, such as radiological evaluation or serum tumor markers. However, CTCs might not be detectable from all metastatic patients.Due to the limited availability of pharmacological therapies and its aggressive clinical course, TNBC is the subtype with the worst outcome with a median overall survival of approximately 18 months or less. This result contrasts with the overall survival of patients with advanced luminal or HER2-positive breast cancer that ranges from 48 to 60 months.Chemotherapy remains the mainstay of treatment for TNBC with disappointing results because despite the high sensitivity of early-stage TNBC to cytotoxic agents, in the metastatic setting, this treatment achieves relatively low rates of antitumor response ranging from 10% to 30% along with a short median progression-free survival that ranges from around six months in the first-line setting to approximately three months in refractory patients ,102.Thus, numerous efforts are currently being undertaken to develop more effective therapeutic strategies in order to improve the overall outcome of TNBC patients, and new advances in the knowledge of molecular biology of TNBC are increasing the treatment options of this complex disease.HMGA1 has been a promising cancer drug candidate for years, but, being a nuclear protein, it was nearly impossible to target it. However, the novel pro-invasive and metastatic role of extracellular HMGA1, as well as the identification of the interaction between HMGA1 and RAGE, opens the possibility of targeting HMGA1, RAGE, and perhaps some of its other ligands as a new potential therapeutic option in patients with TNBC .HMGA1 currently in clinical development. Nevertheless, several small molecule inhibitors of RAGE, binding either the extracellular or the intracellular RAGE domain, are being developed for the treatment of diabetic vascular complications and neurodegeneration, although the results obtained with these inhibitors are disappointing [Unfortunately, there are no clinically viable therapeutics directly targeting pointing ,104. EveTherefore, considering the new data regarding the oncogenic potential of the extracellular localization of HMGA1, along with other proposed functions for HMGA1, such as EMT activation and cancer stem cells (CSC) maintenance, new specific drugs targeting HMGA1 are needed. HMGA1. Although many studies have assessed the critical role of HMGA1 in tumor progression, there has been relatively little work focused on targeting HMGA1 in cancer considering the classical nuclear localization of this protein. One of the main objectives of our work was to identify new therapeutic strategies to target the metastatic phenotype mediated by extracellular Myc oncogene with a self-penetrating dominant-negative called Omomyc [Until now, disrupting the function of oncogenic transcription factors has been challenging, given the limitations of delivery and specificity. One exception is the recent case of targeting the d Omomyc . Even sod Omomyc ,106. Luckily, the novel pro-invasive and metastatic role of extracellular HMGA1 raises exciting opportunities to develop new compounds targeting extracellular HMGA1, including blocking monoclonal antibodies targeted against HMGA1 or soluble decoy receptors that would prevent HMGA1 from binding to its receptors. In fact, our laboratory is currently developing monoclonal antibodies directed against the extracellular form of HMGA1. Despite most monoclonal antibodies used in cancer therapy generally target membrane receptors, in some cases, monoclonal antibodies have also been successfully developed against ligands instead or in addition to its receptors. An example of the targeting of protein ligands in oncology is that of the vascular endothelial growth factor (VEGF). Several agents directed against the VEGF/VEGF receptor (VEGFR) signaling pathway have been developed and are now approved across several indications, although the first targeted antiangiogenic drug authorized for use in cancer patients was bevacizumab, a humanized monoclonal antibody that targets VEGF-A to prevent its interaction with VEGFR-1 and -2 .The full-length human RAGE consists of an extracellular (amino acid residues 23–342), hydrophobic transmembrane (residues 343–363), and cytoplasmic domains (residues 364–404). The extracellular structure of RAGE can be further subdivided into three immunoglobulin-like domains: a variable domain (residues 23–116) and two constant C1 (residues 124–221) and C2 (residues 227–317) domains . In addition to the previously described oncogenic effects of extracellular HMGA1, RAGE expression is also higher in metastatic TNBC cell lines and is associated with poor outcome, playing an essential role in promoting breast cancer growth and metastasis ,109,110,Following the overexpression of RAGE in neurodegenerative disorders, such as Alzheimer’s disease, various antagonists binding to the extracellular or intracellular RAGE domain have been developed and evaluated in this context. Unfortunately, phase III clinical trials using the RAGE antagonist, Azeliragon, failed to meet their primary endpoint . DespiteAt the moment, the design of single-agent clinical studies based on the inhibition of RAGE and extracellular HMGA1 activity might be premature. However, in this section, we looked at the future and proposed a rationale to bring these candidates drug targets to the clinic, provided that sufficient experimental data is presented in the near future.In the case of an HMGA1 inhibitor, the most reasonable proposal in the future for these compounds would be to design a phase Ib dose-escalation trial. The purpose of this study would be to evaluate the safety (maximum tolerated dose and dose-limiting toxicities) and preliminary efficacy of a specific HMGA1 inhibitor in patients with pretreated metastatic TNBC. Regarding RAGE inhibitors, and taking into account that these drugs have already been assessed in other diseases, it seems more appropriate to directly launch a phase II single-arm trial in pretreated patients with metastatic TNBC using Simon’s two-stage design, where overall response rate would be the primary endpoint. Another chance to clarify the mechanism of action of RAGE and HMGA1 inhibitors would be through the design of a phase 0 (window of opportunity) neoadjuvant trial, including patients with localized TNBC treated with a short-course administration of a RAGE or a future HMGA1 inhibitor. This study would represent the best opportunity to elucidate how these compounds work and also to explain the potential antitumor activity of these agents. The primary objective of this trial would be to test if the treatment with a RAGE or an HMGA1 inhibitor is able to change the subcellular localization of HMGA1 between the pretreatment core biopsy and the post-treatment surgical specimen. This study would also allow assessing the pharmacokinetics, pharmacodynamics, reduction in Ki67 proliferation index, and the discovery of other potential biomarkers.To our knowledge, the only evidence supporting a synergistic effect of the combination of chemotherapy and RAGE inhibitors comes from a preclinical model of pancreatic cancer. In this model, the combination of RAGE inhibitors with gemcitabine significantly reduced tumor growth compared with either agent alone . So far,In TNBC, chemotherapy, alone or in combination with targeted therapies, remains the standard of care . This tuAmong others, HMGA1 and RAGE promote EMT in TNBC cell lines ,111, andMultiple lines of preclinical and clinical evidence have demonstrated that tumors can evade destruction by the immune system by expressing surface ligands that engage inhibitory receptors on tumor-specific T cells and induce immune tolerance . Immune-Early results of immunotherapy with immune checkpoint inhibitors in patients with metastatic TNBC have demonstrated encouraging activity with durable responses and substantial overall survival in pretreated patients. Unfortunately, there is a relatively small subset of patients that derive a benefit from single-agent treatment ,121. HowPD-L1 expression has been correlated with the expression of CSC markers and HMGA1 in clinical colorectal cancer specimens. Therefore, PD-L1 could participate in the maintenance of CSC self-renewal by activating HMGA1-dependent signaling pathways  UnfortunAngiogenesis plays an important role in cancer progression. The development of new vessels is decisive for the growth and spread of tumor cells because malignant tumors are unable to grow beyond a few millimeters without new vasculature . LinderhRecently, it has been postulated that HMGA1 increases breast cancer aggressiveness by favoring tumor angiogenesis . TherefoTumor cells have to cope with substantial levels of cellular stress, including hypoxia, nutrient starvation, and acidosis, in order to successfully generate tumors and promote metastasis. Growing evidence suggests that cellular stress is associated with the unconventional secretion of proteins, highlighting among them the secretion of DAMPs, such as HMGB1 and S100s proteins, that probably connects unconventional protein secretion with cancer. Based on our recent results, although HMGA1 binds to RAGE like other DAMPs, the secretion of HMGA1 does not fully fit with the concept of DAMP, considering that we have only shown a cell-autonomous phenotype. In fact, our results demonstrated that an HMGA1 autocrine loop was established in invasive TNBC cells, mediating a migratory and an invasive phenotype. However, we could not discard a danger signal triggered by HMGA1 in the tumor microenvironment, and future studies are needed to determine whether extracellular HMGA1 binds to other receptors beyond RAGE either in tumor or stromal cells.The clinical significance of extracellular HMGA1 has yet to be understood, but our preliminary observations warrant further evaluation in different directions despite the important gaps in the knowledge of the putative role of extracellular HMGA1 and whether targeting this secreted form would benefit cancer patients. First of all, although HMGA1 is mostly nuclear in luminal breast cancer cells, it would not be unexpected that HER2-positive cells also secrete HMGA1. In addition, other cancer types in which the expression of HMGA1 is high, including colorectal, pancreatic, and ovarian cancer, could also secrete HMGA1. Nevertheless, if the secretion of HMGA1 in these cancer types is associated with tumor invasion, the onset of metastasis remains to be defined. Secondly, the alternative functions of non-classical secreted proteins by tumor cells might offer a new strategy to fight against cancer. This is especially relevant, taking into account that these proteins are not likely to be constitutively secreted by healthy tissues. Therefore, the use of monoclonal antibodies that specifically target the extracellular function of these multicompartment proteins might help to interfere with different aspects of tumorigenesis with a favorable toxicity profile. It seems particularly appropriate to combine chemotherapy or other targeted therapies, such as immunotherapy and antiangiogenics agents with HMGA1 inhibitors, in clinical practice.Lastly, the evaluation of HMGA1 as a new prognostic biomarker in patients with TNBC, predicting the development of distant metastasis, merits additional investigation.


During development, neural crest (NC) cells are early precursors of several lineages including melanocytes. Along their differentiation from multipotent cells to mature melanocytes, NC cells will go through successive steps which require either proliferative or motile capacities. For example, they will undergo Epithelial to Mesenchymal Transition (EMT) in order the separate from the neural tube and migrate to their final location in the epidermis . The dif Importantly, these models represent valuable alternative of drug testing or cell/gene therapy for diseases with so far no therapeutic options. Moreover, since melanoma is considered as a NC-derived tumor, these PSC-based models bring an additional and powerful tool to investigate the transformation of this tumor entity and its response to the drugs used in the clinic. About half melanoma patients carry a BRAF mutation and are typically given combined BRAF and MEK inhibitors such as dabrafenib and trametinib, vemurafenib and cobimetinib, and encorafenib and binimetinib (FDA-approved) (Human embryonic pluripotent stem cells (hESCs) were first isolated in 1998 . Derivedpproved) . Unfortuin vitro models of NCs as a comparative and predictive tool for the study of melanoma progression and resistance to cancer therapies. We will therefore examine TFs, role of which has been described both during the development of human NC cells and during melanoma initiation or progression. Then, we will present several differentiation protocols which are used to generate human NC cells from stem cells. Finally, we will discuss the implications of the key regulation of such TFs during melanoma therapy resistance, and the high pertinence of investigating lineage specific signalings in order to improve our understanding of how melanoma still overcomes current treatments in the clinic.The objective of this review is to emphasize to power of stem cell-based SOX10 haploinsufficiency for example, leads to Waardenburg syndrome type IV with ganglionic megacolon due to the loss of ganglion cells, pigmentary abnormalities due to the lack of melanocytes and deafness due to the loss of sensory innervation. Mutations of PAX3 have been identified in Waardenburg syndrome type I and the related splotch mouse model presents white spots due to defects in NCs -Box 10 (SOX10) and Paired box protein 3 (PAX3) are TFs expressed in the NCs, which play a role in the specification of several NC derivatives and in particular of melanocytes. s in NCs .Interestingly, SOX10 and PAX3 are described to colocalize at melanocyte-specific regulatory elements in the promoter of microphthalmia-associated transcription factor (MITF) . The latin vitro studies could correlate reduced BRN2 expression with melanocyte differentiation, its expression and role in vivo seems to be less clear ] transgenic mouse model. In the second study, SOX10 haploinsufficiency in Tyr::NrasQ61KINK4a−/− mice counteracted melanoma formation. A study integrating data from transcriptome, open chromatin and histone modification maps of melanoma cultures identified SOX10/MITF as regulator of the proliferative state and AP-1/TEAD as regulator of the invasive state   . Mutatedlesions) .In sum, these data demonstrate the high value of PSC-derived NC models in order to produce large amounts of human melanocytes. These cells can therefore be used for basic research, drug discovery and ultimately in the clinic for patients with melanocyte-associated diseases. For this purpose, the safety of PSC-derived melanocytes will have to be tightly evaluated before being implanted into patients.FOXD1 is required for melanoma progression since its silencing could significantly impair melanoma migration and invasion . Interestingly, when these cells where compared to mature melanocytes in a gene expression analysis, a subset of TFs including JUN, AP2C, ID2, ID3, and STAT1 was enriched, suggesting a specific involvement of these genes during embryonic development. In this study, the transcriptome of melanoma cells which were exposed to short-term (adaptive resistance) or long-term (acquired resistance) treatment with vemurafenib was also included. Strikingly, the melanoblasts presented more similarities with adaptive resistant melanoma than with acquired resistant melanoma which implies that resistance gene regulation may overlap to some extent with that observed during melanoblast differentiation. Nevertheless, this gene regulation may vary between adaptive and acquired resistance due to obvious differences in kinetics. When compared to vemurafenib-sensitive melanoma cells, melanoblasts and both resistant melanoma cells presented gene enrichment in cell cycle regulation, DNA damage regulation, metabolism of amino acids and nucleotides, JAK–STAT and p53 signalings. Moreover, genes regulated in melanoblasts and acquired resistant melanoma cells were specifically involved in antigen presentation (HLA), cellular movement , and ILK signaling. HLA downregulation in particular, was already described in acquired MAPKi-resistant tumors from melanoma patients . Since all three receptors are common targets of the TGFβ signaling, it suggests an involvement of this pathway in the response to vemurafenib treatment. Although a TGFβ gene signature was associated with the «invasive phenotype» described by Hoek, a link to drug resistance is so far unknown. In addition, the authors observed a reversibility of this resistant state when taking the cells off the drug, a characteristic which could offer an alternative to a subpopulation of reatment . Repressreatment .Recently, the involvement of SOX10 in melanoma drug resistance was reanalyzed at the single cell level. Rare cell populations with non-genetic differences have been identified during the establishment of vemurafenib resistance and the authors proposed the following model: non-resistant tumor cells can switch to a pre-resistant reversible state with expression of AXL, EGFR, and NGFR but variable expression of SOX10. After vemurafenib stimulation, these pre-resistant cells could switch to a resistant state with epigenetically stable changes and a low expression of SOX10. This second switch would be mediated, at least in part, by TFs such as JUN, AP-1, or TEAD . TherefoBased on the demonstration that either SOX10 phosphorylation or SOX10 sumoylation play an important role in its expression and in the activation of its downstream targets in melanoma, it would be interesting to investigate the role of SOX10 post-translational modifications in drug resistance . Indeed Finally, SOX2, another member of the SOX TF family which regulates stem cells pluripotency in connection with OCT4 and NANOG  was receIn sum, mechanisms of drug resistance are numerous and distinct subpopulation of resistant cells with either high SOX10 and high MITF expression or low SOX10 and low MITF expression may exist in the same tumor, rendering difficult to completely eliminate the tumor with one targeted treatment.In conclusion, stem cell-based models of human NCs represent a concrete alternative for probing melanoma progression. Reactivation of developmental signaling during the advancement of melanoma has allowed concentrating the investigations on specific genes. Nevertheless these models will allow identifying new targets which were not tested in a melanoma setting so far. Several NC differentiation methods are nowadays available but few of them lead to a pure cell population and therefore, more NC markers are still needed for better characterization. The availability of melanocyte early progenitors will greatly help the discovery of new candidate genes, targeting of which could improve current melanoma treatments or the prediction of melanoma cell response to a particular drug. MITF or SOX10 have been extensively investigated and allowed a better comprehension of resistance to cancer therapies, underlying the importance of lineage specific signaling in our understanding of how melanoma still overcomes current treatments in the clinic.LL conceived, designed the presented idea, and wrote the manuscript. JU provided financial support and revised the written manuscript.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.


Silicon nanotubes (SiNTs) with unique well-defined structural morphologies have been successfully fabricated and recognized as a novel architecture in the nanoscale Si family. While the typical dendritic microstructure of mesoporous silicon prepared anodically has been exploited previously for therapeutics and biosensing, our status of utilizing SiNTs in this regard is still in its infancy. In this review, we focus on the fundamental properties of such nanotubes relevant to therapeutic applications, beginning with a description of our ability to sensitively tune the structure of a given SiNT through synthetic control and the associated detailed in vitro dissolution behavior (reflecting biodegradability). Emphasis is also placed here on the range of functional moieties available to attach to the surface of SiNTs through a summary of current studies involving surface functionalization and strategies that facilitate conjugation with molecules of interest for multiple purposes, including cell labeling, nucleotide attachment, and scaffolding of therapeutic metallic nanoparticles. Experiments addressing our ability to load the interior of a given nanotube with species capable of providing magnetic field-assisted drug delivery are also briefly described. Given the range of diverse properties demonstrated to date, we believe the future to be quite promising for employing SiNTs as therapeutic platforms. For some time, porous silicon (pSi) has attracted great attention in applications relevant to diagnosis and therapy, owing in part to its biocompatibility and biodegradability in aqueous physiologically-relevant environments ,2,3,4. SWhile SiNTs have been actively evaluated in several applications, including Li ion batteries  and photThus, in this article we focus on several fundamental aspects of SiNTs relative to their possible utility as a therapeutic platform: (1) Convenient synthetic protocols; (2) temporal degradation in biologically-relevant media; and (3) surface modification strategies. As we will see shortly, the latter category has implications not only with regard to imaging and delivery, but also in our ability to create more sophisticated metal-semiconductor nanostructures, also of therapeutic value. Finally, we also demonstrate proof of concept in loading the large interior of the nanotube, utilizing superparamagnetic nanoparticles.4) diluted in He gas (0.5%) serves as a precursor. Hollow SiNTs are achieved via a gas-phase etching process, which involves decomposition of NH4Cl into NH3 and HCl at 450 oC in He to remove the ZnO NW core. By controlling ZnO growth conditions 2 and hexamethylenetetramine (HMTA) and growth time), the subsequent average inner diameter and length of SiNTs can be manipulated from 30 to 200 nm and 500 nm to 10 μm, respectively (32+)  template method  11]. In. In11]. ectively . Interesly (32+) g [11]. Aly (32+) h. An add)4 (and is eliminated from the body via the kidneys in a non-toxic manner), thereby implying favorable biodegradability of this type of SiNT .,63.62,63Using this strategy, one can ideally achieve targeted delivery of a drug attached to the outer nanotube surface, while guided by the presence of an external magnetic field to the desired site in vitro/in vivo . This isThis review has covered a number of key aspects of SiNTs that have interesting implications in therapeutics. While additional opportunities remain, multiple clear advantages of exploiting surface tunability of SiNTs for exploiting their functional tubular structure have been demonstrated. Studies involving biocompatibility of the SiNTs and applications in drug/gene delivery are underway to broaden our knowledge of its interactions with biological systems and potential applications of this novel one-dimensional material.


Risky, Impulsive, and Self-destructive Behavior Questionnaire in community (N = 439) and incarcerated (N = 262) samples to examine latent affect profiles for risky and impulsive behavior. Four affective profiles emerged: low avoidance and low approach, average avoidance and average approach, high avoidance, and high approach. Conditional probability correlations revealed meaningful differences across these profiles in psychiatric symptomatology, personality characteristics, and behavior. Consideration of affective triggers provides an important framework for dissociating the underlying reasons why individuals engage in risky behavior.Common theoretical models of risky and impulsive behaviors suggest that individuals engage in risky behavior to avoid negative affect or enhance positive affect. However, little research has been done to identify person-centered affective profiles of risky and impulsive behavior, and delineate the individual differences across these profiles. The present study used the  Risky and impulsive behavior encompasses a range of acts from speeding to substance misuse to aggression. Collectively these behaviors exact staggering costs by increasing the likelihood of premature death, long-term disability, and poor mental health outcomes . AdditioEngagement in risky and impulsive behaviors emerges in a wide variety of circumstances, but especially when individuals are in negative mood states or are influenced by immediate temptations . AccordiOn the one hand, states of negative affect can serve as triggers for risky and impulsive behavior. For example, exposure to drug-associated cues and contexts increase susceptibility to relapse and substance addicted individuals are highly vulnerable to relapse during periods of withdrawal-induced negative affect . Over vaOn the other hand, seeking positive affect may trigger risky and impulsive behavior. Among college students, positive affect increases the likelihood of illegal drug use and risky sexual behavior over the course of college . In treaNotably, these two affective triggers are not mutually exclusive. While for some individuals, negative affect triggers risky and impulsive behavior, for other individuals, positive affect may be the trigger, for others both negative and positive affect may be the trigger, and for some, risky and impulsive behavior may occur without an affective trigger. Understanding the diversity in affective triggers for risky and impulsive behavior is essential for accurately identifying individuals who engage in these behaviors, and eventually intervening based on the underlying etiological and reinforcement mechanisms subserving their behavior. However, little research has been done to actually define affective profiles in a range of risky behaviors and delineate the individual differences across these profiles.Risky, Impulsive, and Self-destructive Behavior Questionnaire  recruited from the general community through flyers in New Haven County, Connecticut and Internet advertisements posted nationally. Individuals were eligible to participate if they were age 18 or older. Participants that were in the New Haven area came into the lab and participants who were national filled out the survey online using Qualtrics  and female (59%) adults ages 18–66  recruited from a maximum-security prison in Connecticut. A prescreen of institutional files and assessment materials was used to exclude individuals who had performed below the fourth-grade level on a standardized measure of reading  “How many times have you done this in the past month?,” (c) “How old were you the first time?,” and (d) “Did it ever cause you any problems, such as going to the hospital, legal trouble, problems at work, with family or friends.” Participants were asked to rate on a 5-point Likert-type scale (0 = “Strongly Disagree” to 4 = “Strongly Agree”) how much they agreed with the following for each behavior endorsed: (e) “I do this behavior to stop feeling upset, distressed, or overwhelmed” and (f) “I do this behavior to feel excitement, to get a thrill, or to feel pleasure.” The last two questions assessing Avoidance and Approach, respectively, encompassed both the automatic action tendency and the valence motivating these behaviors. That is, the Avoidance scale included negative basic emotions  and avoidance motivational impulses, whereas the Approach scale included positive basic emotions and approach motivational impulses. Though emotion and motivation are not interchangeable, these groupings across emotion and motivation categories represent two theoretically relevant conceptualizations of affective triggers for risky behaviors and there is evidence that the neural systems involved in the emotional and motivational “avoidance” versus “approach” systems are overlapping  rlapping .Dimensions of Anger Reactions-5  5 DAR-5; , a 5-iteale DTS; , a 15-itBIS/BAS; , a 20-itory PAI;  BorderliMAST-AD; , a 25-itStructural Clinical Interview for DSM-5 , we first residualized the average ratings on the affective scales by total lifetime engagement in risky behavior before submitting them to the latent profile analysis. We evaluated five latent profile models (2- through 6-class models). The relative fit of the models was compared using the Bayesian Information Criterion , entropy  samplehttp://quantpsy.org). Conditional probabilities were used in order to reduce the impact of unbalanced sample sizes across latent classes. All tests were completed using SPSS version 23.0 .Comparison of latent profiles was examined by correlating the probability of membership in each class with external variables using Pearson correlations. Differences in the magnitude of pairs of associations between external variables and the probability of membership in different latent classes were evaluated using a test of dependent correlations  characterized 30% of the sample, class 2 (Average) characterized 47% of the sample, class 3 (High Avoid) characterized 16% of the sample, and class 4 (High App) characterized 7% of the sample.In terms of substance use, the probability of membership in the class marked by selectively high ratings on RISQ Avoidance class 3) was associated with higher prior alcohol use symptoms and cannabis use symptoms than the classes characterized by low and average scores on the RISQ affect scales . Next, in terms of criminal activity, probability of membership in the High Approach class was associated with higher total number of crimes and non-violent crimes than membership in the other classes. Probability of membership in the class marked by low ratings on both of the RISQ affect scales (class 1) was associated with higher total number of violent crimes than membership in class 2 or 3, though this relationship was largely driven by higher numbers of sex crimes in class 1. Finally, in terms of disciplinary violations within prison, the probability of membership in the High Approach class was associated with higher total number of disciplinary violations than membership in class 2. Probability of membership in the High Avoid class was associated with higher number of violations against persons than membership in class 2 but lower number of substance use violations than membership in classes with low and average ratings on the RISQ affect scales (classes 1 and 2). Further, probability of class membership in the Average class was associated with fewer total days in segregation as punishment for substance use violations than membership in classes marked by high avoid and approach, respectively (classes 3 and 4)  and another subset who engaged in risky behaviors primarily because of approach tendencies . Moreover, some individuals tended to report risky behaviors in the context of low or average levels of both avoidance/approach tendencies.Individuals who were primarily motivated by avoidance reported higher levels of behavioral inhibition and symptomatology related to mood and anxiety disorders, and lower ability to tolerate distress. This profile among incarcerated individuals was predictive of alcohol and marijuana use disorders and disciplinary violations  against people within the prison. It is possible that this profile captures individuals who use substances to self-mediate, who struggle to tolerate unpleasant states, and who have difficulty disengaging from risky behavior in the face  of psychological or physical distress . By contTogether, these four profiles may represent the influence of levels of affect on behavior along a continuum. At the low end and in the middle, affective tendencies may not dissociate or may be non-specific predictors of behavior. However, at the high end of arousal, avoidance or approach affective tendencies become predominant and a primary affective trigger emerges to best characterize risky behavior within an individual. The emergence of distinct affective profiles highlights the importance of assessing both behavioral engagement across high-risk behaviors and people’s differing emotions and motivations for engaging in them. One advantage of this approach is that it may have greater transdiagnostic relevance for understanding affective profiles for risky behavior than previous research on category-specific subtypes. Further, examining affective triggers for a range of risky behaviors has high ecological validity, given that individuals who engage in one type of risky behavior are at higher risk for other types of risky and impulsive behaviors . Thus, tRISQ. Second, the sample sizes in the community and prison samples were moderate in size. It is possible that larger samples would produce different class solutions that better separate individuals  and pathological outcomes (violent crimes).Several limitations should be noted. First, although our data indicated a 4-class solution best fit the data, it is entirely possible that other profiles exist, and further exploration of such subtypes should be examined in future research on the The present results contribute a strong empirical model that future research on the affective triggers for risky and impulsive behavior can build upon. Given that risky and impulsive behaviors are transdiagnostic features of many psychiatric diagnoses and social problems , researcAB-S and NS collected the data. EK, NS, and AB-S conducted the analyses and wrote the manuscript.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.


CXCL8  can produce different biological effects by binding to its receptors: CXCR1, CXCR2, and the Duffy antigen receptor for chemokines (DARC). CXCL8 and its receptors are associated with the development of various tumor types, especially colorectal cancer and its liver metastases. In addition to promoting angiogenesis, proliferation, invasion, migration, and the survival of colorectal cancer (CRC) cells, CXCL8 and its receptors have also been known to induce the epithelial-mesenchymal transition (EMT) of CRC cells, to help them to escape host immunosurveillance as well as to enhance resistance to anoikis, which promotes the formation of circulating tumor cells (CTCs) and their colonization of distant organs. In this paper, we will review the established roles of CXCL8 signaling in CRC and discuss the possible strategies of targeting CXCL8 signaling for overcoming CRC drug resistance and cancer progression, including direct targeting of CXCL8/CXCR1/2 or indirect targeting through the inhibition of CXCL8-CXCR1/2 signaling. CXCL8, also known as neutrophil-activating factor (NAF) and interleukin 8 (IL-8), was the first chemokine identified, and it was originally identified as a leukocyte chemoattractant . CXCL8 i+ angiogenic chemokines and inhibits tumor development [CXCL8 may control leukocyte trafficking during inflammation as well as during homeostasis, principally through interacting with the chemotaxis receptor CXCR1 , and it elopment , 13. HowκB inhibitors) and direct strategies, such as CXCL8 inhibition or inhibition of its receptors   see .Considerable evidence has shown that EMT is a pathological process contributing to cancer invasion and metastasis. When EMT occurs in the epithelial tumor cells, they develop some characteristics of mesenchymal cells, such as reduced cell-cell adhesion, which can improve their invasive migration abilities and promote the movement of tumor cells from the extracellular matrix and their release into the blood or lymph. The tumor cells in the blood or lymph are called CTCs, and these become potential “seeds” for distant metastases.P < 0.01), and the process occurred along with the activation of the PI3K/Akt-ERK1/2 signaling pathway. After EMT, CRC cells can regulate CXCL8 in an autocrine manner and increase the expression of its CXCR1 and CXCR2 receptors, which could contribute to cancer progression, particularly to cancer invasion, dissemination, and metastasis. The antibody inhibition test showed that CXCR1 but not CXCR2 was active in this process [Hwang et al. isolated colonospheres from 22 primary CRC tissues and several CRC cell lines and characterized their gene expression patterns by microarray analysis, including CXCL8, snail, and the colon cancer stem cell marker CD44, as well as the mesenchymal marker vimentin . The res process . In addi process . Among t process  may coopβ2 integrins on PMNs, which facilitate melanoma cell adhesion to the EC. After adhesion to the EC, the subsequent extravasation of the tumor cells by a shear rate-dependent mechanism was also regulated by endogenously secreted CXCL8 within the tumor microenvironment. This phenomenon indicated that CXCL8 can mediate the adhesion of tumor cells to the EC and the resulting exosmotic process into the peripheral blood. Identical results were found in similar tests of other types of tumor cells. Interestingly, cells grown at low density were more effective in invading endothelial monolayers than cells grown at high density. When maintained at low cell density, triple-negative human MDA-MB-231 breast cancer cells that were widely used for modeling cellular invasion showed an easily discernible endothelial monolayer invasive phenotype, which was associated with a YAP-dependent upregulation of the cytokines, including CXCL8. Antibody blockade of cytokine receptors (such as CXCR2) inhibited invasion and confirmed that they were rate-limiting drivers that promoted cancer cell vascular invasiveness [A variety of mesenchymal cells  and blood flow shear stress are involved in the extravasation process of the tumor cells from the tumor tissue. In the adhesion assay of tumor cells to endothelial cells, Li et al.  found thsiveness . This phsiveness .Mechanistic analyses determine that CXCL8 and its receptors contribute to the survival of CRC cells, mainly by reducing the survival pressure of tumor cells and helping them become resistant to anoikis before and after invading the blood. Moreover, CXCL8 and its receptors are also involved in the mechanism of CRC cells and circulating CRC cells escaping from immune surveillance.Hypoxia , a repreAs is well known, the wild type of TP53 is an important broad-spectrum tumor suppressor molecule, but the mutated TP53 exhibits new oncogenic functions, such as the promotion of survival, proliferation, and invasion . It has Autophagy, a catabolic process of cellular self-digestion that acts as a double-edged sword in tumor survival mechanisms and progression, is a potential target for antineoplastic therapies. On the one hand, the tumor cells can increase the level of autophagy themselves to relieve the survival pressure and resistance to apoptosis; on the other hand, excessive autophagy may be able to induce autophagic apoptosis, and the balance between proapoptotic and antiapoptotic effects directly affects the survival of the tumor cells. To obtain a more comprehensive understanding of the survival mechanisms of the tumor cells, it is very important to look for one or more specific markers reflecting the level of autophagy, which is difficult and costly to detect clinically. Kraya et al.  used ELIIn our published study , we show+low NK cells are endowed with cytotoxic and cytokine-producing capacities. These two immune cells predominate in the peripheral blood, and more than 90% of them are equipped with CXCR1 and CXCR2 [+ chemokines and to participate in the earliest phase of the innate immune response [Neutrophils are commonly known as “professional” phagocytic cells of the innate immune system, and CD56nd CXCR2 , which gresponse . To studresponse  develope+ T cell cytotoxic activity, which damaged the immune response. Therefore, CXCL8 and its receptors may act as a defensive shield for escaping immune surveillance of the tumor cells as well as CTCs. Above all, the finding that CXCL8 levels towards the center of cancer tissue are lower than those towards cancer-adjacent tissue [When tumor cells intrude into the blood, they are called CTCs. Despite the fact that most CTCs are killed by immune effector cells, a small number of them evade immune surveillance and survive in the blood, eventually resulting in clonal expansion and the formation of metastatic lesions. It is crucial to define the characteristics that enable a select CTC population to escape immune surveillance; in particular, it must be determined whether interactions between adhesive immune cells and CTCs provide a protective effect on CTC survival. To study human CXCL8, Asfaha and colleagues  developet tissue  seems toFurthermore, to evaluate the influence of the innate immune response marker TLR ligands on autophagy-mediated innate immune responses, Li et al.  transfec+Ly6G+ neutrophils, the mainly excretive cells of CXCL8, accumulated in the lung first and then facilitated the metastatic cancer cell transfer to the lung. As an important neutrophil chemotactic factor, CXCL8 is likely to play a significant role in the aggregation of neutrophils to the metastases, and in return, the aggregate neutrophils will secrete more CXCL8. This cascade effect contributes to the formation of the premetastasis inflammatory microenvironment and the preparation for the homing of tumor cells . Therefore, we have reason to speculate that CXCL8 aggregated in the premetastases would be the key chemotactic factor in the homing of CTCs. Moreover, to identify candidate tumor-derived attractants for CTCs, Kim et al. [+ tumor cells to CXCL8 high expression sites. This phenomenon disappeared when the tumor cell CXCR1/2 was knocked out, indicating that CXCL8 may attract CXCR1/2+ CTCs homing to the primary tumor or metastases. In another study, Li et al. [Over the years, the “seed and soil” doctrine and the theory of the inflammatory microenvironment have received more and more attention. That tumor cells are able to transfer to a specific organ and then grow there is mainly related to the suitable “soil” provided for the tumor cells in the target organ. The inflammatory microenvironment is also active in the tumor development and transfer processes. In the breast cancer lung metastasis model of mice, Wculek and Malanchi  found thm et al.  comparedi et al.  observedMesenchymal-epithelial transition (MET), as the inverse process of EMT, reverses tumor cells that have undergone EMT to an epithelial cell state, making them easy to integrate into new tissues and organs and form metastases. In our recent study mentioned above , we showOsteopontin (OPN) is widely distributed in various tissues and cells and is involved in tissue repair, self-metabolism, and other functions that allow OPN to play an important role in tumor metastasis –46. PresP < 0.0001), and they found a prominent linear correlation between OPN and CXCL8 mRNA expressions in tumor tissues, indicating that there was a synergistic role between CXCL8 and OPN in regulating the development of colorectal cancer. Overall, they can not only coregulate the motility, chemotaxis, and shaping of cancer cells but also synergistically induce the MET process of CRC cells.It has been demonstrated that OPN has chemotactic activity for leukocytes, which is involved together with CXCL8 in prostate cancer recurrence . What isβ2 integrin signaling pathway [β2 integrin signaling pathway. Intravital microscopy demonstrated that cancer cells could adhere directly on top of the arrested neutrophils, indicating that neutrophils may act as a bridge to promote interactions between cancer cells and the liver parenchyma.PMNs in the peripheral blood can not only promote tumor cell adhesion to the endothelial cell and extravasation into the blood but also participate in the adhesion and colonization of the target organ by CTCs via CXCL8 and the ICAM-1- pathway . Using i pathway  found thP < 0.05), while the survival curve analysis also showed that the significantly decreased disease-free survival (DFS) and overall survival (OS) (P < 0.05) were highly related to the high expression of CXCL8 in CRC patients, which led to tumor progression and a poor prognosis [CXCL8 and its receptors are involved not only in mediating interactions between tumor cells and stromal cells but also in regulating the tumor microenvironment in primary CRC as well as its liver metastasis and promoting colorectal cancer progression by inducing angiogenesis, regulating tumor-associated stroma, or acting directly on tumor cells. Numerous clinical studies, including our research, have demonstrated that the elevated levels of CXCL8 in serum and tissues from colorectal cancer patients were related to the grade, stage, lymph node metastasis, and liver metastasis of CRC  expression in tumor-associated fibroblasts, which enhanced the growth of PDAC cell allografts but not the PDAC cells themselves; the tumor progression was attenuated by CXCR2 inhibition, which indicated that tumor-stromal interactions regulated tumor progression via a CXCR2-dependent chemokine and Ctgf axis. Singh et al. [Recently, mesenchymal stem cells (MSCs) have been shown to home to carcinoma and facilitate the formation of the tumor-associated stroma. Wang et al.  reportedh et al.  found thh et al.  establisCXCL8 and its receptors can affect the tumor cells directly to promote their growth and proliferation. Lee et al.  developeP < 0.05), and CXCL8 expression was significantly higher in CRLM than in primary CRC tissues. This concentration gradient of CXCL8 would be a pivotal factor inducing CRC cells to metastasize to the liver in a chemotactic pathway. Moreover, when the metastases form, more and more CXCL8 will be secreted in the tumor microenvironment to accommodate the growth of metastases, and the role of CXCL8 seems to be more important in metastasis than in primary CRC tissues. In the CRLM model, not only did Varney et al. [Furthermore, CXCL8 is highly expressed not only in primary tumors but also in the metastases. Compared with the corresponding neighboring tissues, Rubie et al.  showed ty et al.  find thaSurgical resection is the primary therapeutic approach for CRC, but distant metastasis or recurrence is the main reason influencing the curative effect of the radical surgery, which indicates a poor prognosis of malignant tumors. Therefore, it is particularly significant for patients being treated with drugs to improve the curative ratio before and/or after the surgery. However, drug resistance to conventional antineoplastic therapies is a serious issue. CXCL8 and its receptors are involved in almost the entire process of colorectal cancer progression. Targeting CXCL8-CXCR1/2 signaling axes may be a potential new therapeutic strategy to control CRC progression and overcome the drug resistance of colorectal cancer.κB inhibitors and anti-inflammatory medications) and direct CXCL8 or CXCR1/2 blocking .The possible strategies of targeting CXCL8-CXCR1/2 signaling in CRC include indirect strategies  regulation of the CXCL8 gene by NT in HCT116 cells. What is more, curcumin, which blocked NT-mediated NF-κB induction, and BAPTA-AM, a Ca2+ chelator, both inhibited CXCL8 mRNA expression and protein secretion in HCT116 cells. The inhibition of CXCL8 was then found to inhibit the growth and migration of HCT116 cells [CXCL8-CXCR1/2 signaling may be targeted not only directly by regulation of CXCL8/CXCR1/CXCR2 expression and signaling but also indirectly by the regulation of significant signaling pathways and transcription factors, including PI3K/Akt, MEK/ERK, and NF-LY294002 . FurtherLY294002 , indicat16 cells . StrategκB activity [In addition, to determine the association with colorectal cancer risk and overall survival, Bondurant et al.  detectedactivity . AlthougAs previously mentioned, CXCL8-induced migration of endothelial cells and the growth, proliferation, and migration of tumor cells as well as the chemotaxis of CTCs to the metastases can all be abrogated by neutralizing antibodies of CXCL8/CXCR1/CXCR2 or small-molecule receptor antagonists of CXCR1/CXCR2, indicating that directly targeting CXCL8-CXCR1/2 signaling is critical to controlling the CXCL8-mediated CRC progression. To study the role of small-molecule receptor antagonists in tumor progression, Varney et al.  establis+ T cells and thus helped the tumor cells to escape from immune surveillance [+CD11b+Ly6Ghi MDSCs in the tumor bed was the root cause limiting the efficacy of PD1 checkpoint blockade in cancer. MDSCCXCR2+-mediated suppression of antitumor immunity was just a local phenomenon because inhibition of MDSCCXCR2+ trafficking to the tumor enhanced the potency of PD1 checkpoint blockade, which indicated that combining CXCR2 inhibitors with immune checkpoint inhibitors may become a new combination immunotherapy strategy in cancer.Immunotherapy has recently become a hot topic in the field of cancer therapy. CXCL8 and its receptors can induce the recruitment of tumor-associated immune cells into the tumor sites, which inhibited the activity of CD8eillance . Otherwieillance  developeIn addition, because the autophagy-CXCL8 signaling axis is one of the potential mechanisms in cellular resistance to apoptosis, targeting both autophagy and CXCL8 may provide double antitumor effects. Since autophagy plays a dual role in the development of colorectal cancer, we should determine what role autophagy plays in each patient first and then establish a combination therapy, including CXCL8/CXCR1/CXCR2 antagonists and autophagy inhibitors/activators, to enhance the antitumor effects according to the CXCL8/CXCR1/CXCR2 and autophagy expression levels of the patient. These combination therapies based on CXCL8 and its related signaling would provide a new breakthrough in tumor therapy.Primary or acquired resistance to conventional chemotherapeutic drugs is a general phenomenon that causes failure to antitumor therapy. Many molecular mechanisms have been found to be involved in drug resistance: apoptotic resistance or activation of survival signaling pathways, DNA damage repair, mutation of drug targets, alterations in drug metabolism, and increased rates of drug efflux, in which apoptotic resistance of cancer cells during treatment with conventional therapeutic drugs is the fundamental mechanism of drug resistance in antitumor therapy. As CXCL8 and its receptors play an important antiapoptotic role in the survival of CRC cells, targeting CXCL8 and its receptors could become a new strategy to reverse drug resistance in CRC therapy.Hypoxia in the tumor microenvironment can induce the expression of CXCL8 and CXCR1/2, which allows the hypoxic cancer cells to be able to tolerate etoposide, a chemotherapeutic drug that works via DNA damage. When CXCL8 expression was inhibited, the efficacy of etoposide was significantly enhanced, suggesting that CXCL8 contributed to the apoptotic resistance and subsequent drug resistance . DabkeviAbove all, the upregulation of CXCL8 and its receptors is an obstacle to improving the efficacy of conventional chemotherapeutic drugs , and theMost intestinal diseases, including colorectal cancer, need endoscopy to make a clear diagnosis. However, for some chronic and recurrent intestinal diseases, frequent endoscopy also has a certain risk. Many patients refuse the endoscopy because of the creativity. Therefore, the emergence of a new biomarker or imaging technology is particularly important. In order to detect and locate the disease activity of patients with IBD with (99 m) tc-cxcl8 SPECT, Aarntzen et al.  injectedAlthough CXCL8 and its receptors play a variety of roles in the process of colorectal liver metastases, the explicit mechanism of CXCL8 and its receptors in the resistance to anoikis and the immune tolerance of circulating cancer cells as well as the chemotaxis for CTCs homing to the liver remain unclear. Currently, the importance of accurate medical therapy is widely recognized in the field of cancer therapy, and monotherapy and combination therapies based on therapeutic strategies targeting CXCL8-CXCR1/2 signaling and other therapies could become an important route for preventing cancer recurrence and distant metastases. Because neutralizing antibodies and small-molecule antagonists of CXCL8 and its receptors have been used in various preclinical trials including colorectal cancer, they will be applied in clinical practice in the near future if the efficacy and specific treatment standards are sufficiently verified in clinical trials.