Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related deaths in the United States with a five-year survival rate of approximately 7%. Its highly invasive characteristics, lack of biomarkers for early detection, limited therapeutic targets and inherent resistance to chemotherapy are the central factors that lead to an overall poor prognosis for this malignancy. Since most cancer-related deaths are a result of metastatic tumors, we reasoned that our previously published proteomic signature of the cell pseudopodium (PD) may be a good pool from which to identify novel protein biomarkers or therapeutic targets in pancreatic cancer. We cross-referenced PD enriched proteins with Oncomine and identified 37 genes that are upregulated in pancreatic cancer. The function of integrin alpha 1 (ITGA1), a cell surface receptor for collagen and regulator of cell adhesion, has not been previously characterized in the context of PDAC. Our results indicate that ITGA1 is required for PDAC cell viability, promoting cell survival and tumor growth. We further analyzed ITGA1 cell-surface levels and discovered that ITGA1hi cells represent a subpopulation of Aldehyde Dehyrogenase high (ALDH1hi) cells, and that ITGA1 knockdown reduces the ALDH1hi cell population. One mechanism by which PDAC cells acquire metastatic potential is via epithelial-mesenchymal transition (EMT). Thus, we searched for prominent EMT genes among the top ITGA1 co-expressors using RNA-Seq data from the Cancer Bio Portal. Interestingly, ZEB1 (a transforming growth factor beta, TGFbeta, response gene and central regulator of EMT) and PEAK1 kinase (a protein we’ve shown to be required for pancreatic cancer progression and TGFbeta/ZEB1-induced EMT) co-expresses with ITGA1. We tested the function of ITGA1 on TGFbeta-induced EMT and found that ITGA1 is upregulated by TGFbeta during EMT, and required for metastasis and a complete EMT response to TGFbeta. We also demonstrate that PEAK1 is required for TGFbeta-induced ITGA1 in PDAC cells. Finally, we demonstrate that ITGA1 is responsible for collagen-induced spreading and an EMT-like shift in PDAC cell morphology. Taken together, these results point to a novel TGFbeta/PEAK1/ZEB1/ITGA1 signaling cascade that when targeted can abrogate PDAC cell survival, stemness, EMT and tumor growth/metastasis.
Citation Format: Armen Gharibi, Sa La Kim, Daniel Brambilla, Yvess Adamian, Malachia Hoover, Joy Lin, Megan Agajanian, Laurelin Wolfenden, Jonathan A. Kelber. The PEAK1/ZEB1/ITGA1 pathway mediates survival, stemness and TGFbeta-induced EMT in pancreatic cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4426.