NEOPLASTIC AND STROMAL CELL CROSS-TALK PROMOTES A COLLAGEN SIGNALING COMPLEX IN PANCREATIC CANCER
Annie Li*, Thomas P. Hank, Kim C. Honselmann, David Birnbaum, Sebastian Begg, Keith D. Lillemoe, Andrew L. Warshaw, Carlos Fernández-del Castillo, Andrew S. Liss
General Surgery, Massachusetts General Hospital, Cambridge, MA
Background:
Pancreatic ductal adenocarcinoma (PDAC) is characterized by an extensive desmoplastic reaction formed by extracellular matrix (ECM) components and cancer-associated fibroblasts (CAFs). The ECM represents a heterogenous group of proteins that support soluble and mechanical signaling in the tumor. Despite its importance, little is known about the regulation of ECM expression in PDAC. Here we investigate the regulation of collagen XVII and collagen VII that are key components of an epithelial cell signaling complex.
Methods:
The expression of COL17A1 and COL7A1 was examined by qPCR in mono- and co-cultures of PDAC cell lines and immortalized cultures of CAFs. The expression of both COL17A1 and COL7A1 was analyzed by RNA-sequencing in cancer and stromal cells isolated by laser capture microdissection from 13 human PDAC samples. Immunohistochemistry was performed in patient-derived xenograft (PDX) tumors, chronic pancreatitis and untreated murine pancreas to determine the expression patterns of collagen XVII. To further describe the localization of collagen XVII immunofluorescence studies were performed on PDAC and CAF cell lines.
Results:
COL17A1 was highly expressed in PDAC cells in comparison to COL7A1, which was almost absent. Conversely, CAFs did not express COL17A1 but expressed high levels of COL7A1. Upon co-culture with CAFs, an upregulation of COL17A1 and robust expression of COL7A1 was observed in PDAC cells. Additionally, COL7A1 expression increased in CAFs after co-culture with PDAC cells; however, CAFs still failed to express COL17A1. Importantly, these co-culture models recapitulate the expression of COL17A1 and COL7A1 observed in tumors. Analysis of human PDAC samples revealed COL17A1 was predominantly expressed in the cancer cells, whereas the expression of COL7A1 was more prevalent in the adjacent stroma. Consistent with this, immunofluorescent analysis demonstrated a strong membranous staining of for collagen XVII in cultured PDAC cells which was absent in immortalized CAF cells. The expression of collagen XVII appears to be unique to pancreatic cancer as immunohistochemistry analyses showed a strong expression of collagen XVII, which was absent in normal and chronic inflammatory pancreatic tissue. In contrast, collagen VII was pre-dominantly expressed in the stromal compartments of PDAC samples and not in the tumor cells.
Conclusion:
The present findings highlight the different contribution of PDAC and CAF cells in the production of a collagen XVII - collagen VII signaling complex. Furthermore, the upregulation of collagen XVII and collagen VII upon the co-culture of stromal and neoplastic compartments underlines the importance of PDAC-CAF crosstalk in pancreatic cancer.
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