Background: Human colorectal cancer is caused by mutations and is thought to be maintained by a population of cancer stem cells. Further phenotypic changes occurring at the invasive edge suggest that colon cancer cells are also regulated by their microenvironment. Type I collagen, a promoter of the malignant phenotype in pancreatic carcinoma cells, is highly expressed at the invasive front of human colorectal cancer.
Methods: This study investigates the role of type I collagen in specifying the colorectal cancer cell phenotype. The effect of type I collagen on morphology, localisation of cell-cell adhesion proteins, differentiation and stem cell-like characteristics was examined in a panel of human colorectal carcinoma cell lines.
Results: Human colorectal carcinoma cells grown on type I collagen in serum-free medium show an epithelial-mesenchymal-like transition (EMT-like), assuming a more flattened less cohesive morphology. Type I collagen downregulates E-cadherin and beta-catenin at cell-cell junctions. Furthermore, type I collagen inhibits differentiation, increases clonogenicity and promotes expression of stem cell markers CD133 and Bmi1. Type I collagen effects were partially abrogated by a function-blocking antibody to alpha2 integrin.
Conclusion: Together, these results indicate that type I collagen promotes expression of a stem cell-like phenotype in human colorectal cancer cells likely through alpha2beta1 integrin.