In vitro models for the identification and characterization of tumor-promoting and protective factors for colon carcinogenesis.

The present review aims to give a short overview of the existing cell culture models and their characteristics. While both the induction and the prevention of tumors can only be unequivocally demonstrated in vivo, in vitro models of colorectal cell growth are essential tools for the identification of candidate compounds and for the analysis of underlying mechanisms. Unfortunately normal and premalignant colorectal epithelial cells that represent the target cells of tumor promoters like desoxycholic acid or 1,2-diglyceride and could be used to investigate their cell biological effects are difficult to obtain. Cell line studies have mostly used carcinoma cell lines or rat small intestinal epithelial cells. Some normal immortalized cell lines have been established but are not widely used, and premalignant adenoma cell lines are extremely rare. However, those that do exist are useful both in mechanistic studies of cell growth and for the analysis of tumor promoters and chemoprotectors of colorectal carcinogenesis.