The prognostic significance of collagen VI in pancreatic ductal adenocarcinoma.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is characterized by poor prognosis and lack of effective diagnostic and prognostic biomarkers. A rich and activated desmoplastic tumor stroma is considered a hallmark of PDAC, and therefore stromal components could be a source of possible new prognostic biomarkers. Expression of collagen VI (COL6) has been found to associate with prognosis in many forms of cancer but has been less extensively studied in PDAC. Some previous studies indicate that COL6 expression is upregulated in PDAC, and it could have prognostic value. In this study the expression of COL6 was analyzed by immunohistochemistry in tissue microarrays (TMAs) containing tumor tissue samples from 164 (n = 164) PDAC patients who had undergone surgical resection. Scoring results were combined with clinical data, and the prognostic significance of COL6 was estimated with Kaplan-Meier survival estimates and multivariable Cox regression analysis. COL6 protein expression patterns were further investigated in The Cancer Proteome Atlas (TCPA) dataset (n = 103) and in the Clinical Proteomic Tumor Analysis Consortium (CPTAC) dataset (n = 138). COL6 mRNA expression in PDAC tissue was investigated using The Cancer Genome Atlas (TCGA) by forming a dataset containing gene expression data and corresponding clinical variables of 168 (n = 168) PDAC patients. In this large PDAC TMA cohort we could not find statistically significant (p < 0.05) differences in survival when comparing patients with high and low protein expression of any of the analyzed COL6 α-chains (α1(VI): HR 0.90, 95% CI 0.64-1.28; α2(VI): HR 1.28, 95% CI 0.86-1.89; α3(VI): HR 0.91, 95%CI 0.64-1.29). Similar results were obtained when assessing expression of COL6 in public data from TCPA, CPTAC and TCGA. In contrast with previous studies and some other cancer forms, we did not find any association of COL6 tissue expression and PDAC survival on protein or mRNA level.