COL8A1 and familial pancreatic carcinoma: On the other hand, the observed increased invasion in the absence of MUC4 was a bit surprising as we did not find any significant variation of metalloproteinase expression (MMP2, -7 or -9) (not shown) and decrease of collagen, type VIII alpha 1 (COL8A1) expression, a component of the stromal reaction in pancreatic cancer, was observed in microarray analyses.