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Effect of tumour promoters and non-genotoxic carcinogens on terminal differentiation and proliferation in mouse teratoma XB2 cells cultured in low calcium medium.

XB2 cells, a teratocarcinoma derived cell line of keratinocyte lineage, have been shown to proliferate and differentiate in low calcium medium (0.03 mM Ca2+) at a density of 500 cells/9.6 cm2 without the need for fibroblast feeder layers or conditioned medium. The degree of differentiation can be assessed by measurements of keratin production and stratification of colonies of cells. Both of these parameters, as well as the proliferative capacity of the cells, can be altered by treatment of the cultures with various promoting agents and non-genotoxic carcinogens. Treatment with teleocidin and 12-O-tetradecanoyl phorbol-13-acetate induced large increases in proliferation, stratification and keratinization; mezerein-treated cells showed increased stratification at higher doses; butylated hydroxyanisole treatment resulted in hyperkeratinization and hyperstratification to lower levels than that seen with the phorbol-ester-like promoters; butylated hydroxytoluene had purely hyperproliferative effects. We suggest that this culture system may provide a useful model for studies of the mechanism of promotion and non-genotoxic carcinogenesis in epithelial tissues.