Analysis of COL6A3, COL6A5 and COL6A6 Gene Expression in Breast and Prostate Tumors

Collagen VI is a ubiquitous extracellular matrix (ECM) protein that plays a structural role in the ECM and is found in close association with the basement membranes of a variety of cell types. Collagen VI that exists as a heterotrimer of three chains; 1(VI), 2(VI) and 3(VI) encoded by the COL6A1, COL6A2 and COL6A3 genes, respectively. Two new collagen VI genes have been described recently in humans; COL6A5 and COL6A6. The role of collagen VI in cancer is very poorly understood although it has recently been shown that the expression of the collagen VI genes has been shown to be altered in several different types of solid tumors. The aim of this study is to investigate the tissue distribution of COL6A3 and the two new collagen VI genes, COL6A5 and COL6A6 and to determine whether the expression of these genes is altered in breast and prostate tumors. We found that COL6A3 is expressed in a wide range of tissues with highest expression in skin and uterus. In contrast, COL6A5 and COL6A6 were expressed in a much smaller subset of tissues and, in general, not co-expressed in the same tissues. There were stage-specific differences in expression of COL6A3 in breast and prostate tumor panels. The expression of COL6A3 decreased with increasing tumor stage in both the breast and prostate models although the only the changes in prostate tumors were statistically significant (P=0.04). Our data suggest the exciting possibility that, since collagen VI gene expression decreases as the tumor becomes more malignant, collagen VI may be a clinically useful biomarker for tumor progression.