Macrophage-secreted MMP9 induces mesenchymal transition in pancreatic cancer cells via PAR1 activation.
PURPOSE
Targeting tumor-infiltrating macrophages limits progression and improves chemotherapeutic responses in pancreatic ductal adenocarcinoma (PDAC). Protease-activated receptor (PAR)1 drives monocyte/macrophage recruitment, and stromal ablation of PAR1 limits cancer growth and enhances gemcitabine sensitivity in experimental PDAC. However, the functional interplay between PAR1, macrophages and tumor cells remains unexplored. Here we address the PAR1-macrophage-tumor cell crosstalk and assess its contributions to tumor progression.


METHODS
PAR1 expression and macrophage infiltration were correlated in primary PDAC biopsies using gene expression datasets and tissue microarrays. Medium transfer experiments were used to evaluate the functional consequences of macrophage-tumor cell crosstalk and to assess the contribution of PAR1 to the observed responses. PAR1 cleavage assays were used to identify a macrophage-secreted PAR1 agonist, and the effects of candidate proteases were assessed in medium transfer experiments with specific inhibitors and/or recombinant agonist.


RESULTS
PAR1 expression correlates with macrophage infiltration in primary PDACs, and macrophages induce mesenchymal transition of PDAC cells through PAR1 activation. Protease profiling identified macrophage-secreted matrix metalloprotease 9 (MMP9) as the relevant PAR1 agonist in PDAC. PAR1 and/or MMP9 inhibition limited macrophage-driven mesenchymal transition. Likewise, preventing mesenchymal transition by silencing ZEB1 or by pharmacological inhibition of the MMP9/PAR1 axis significantly reduced the ability of tumor cells to survive the anti-tumor activities of macrophages.


CONCLUSION
Macrophages secrete MMP9, which acts upon PDAC cell PAR1 to induce mesenchymal transition. This macrophage-induced mesenchymal transition supports the tumor-promoting role of macrophage influx, explaining the dichotomous contributions of these immune cells to tumor growth.
['Tekin|Cansu|C|http://orcid.org/0000-0003-3961-5603', 'Aberson|Hella L|HL|', 'Waasdorp|Cynthia|C|', 'Hooijer|Gerrit K J|GKJ|', 'de Boer|Onno J|OJ|', 'Dijk|Frederike|F|', 'Bijlsma|Maarten F|MF|', 'Spek|C Arnold|CA|']
D014408:Biomarkers, Tumor D016923:Cell Death D045744:Cell Line, Tumor D002470:Cell Survival D058750:Epithelial-Mesenchymal Transition D015972:Gene Expression Regulation, Neoplastic D006801:Humans D008264:Macrophages D020780:Matrix Metalloproteinase 9 D010190:Pancreatic Neoplasms D044463:Receptor, PAR-1 D015398:Signal Transduction
MMP9 Pancreatic cancer PAR1 Macrophages PDAC EMT