A method for accelerating progression to a malignant phenotype in rodent cells

This report describes a system of suspension culturing that enhances the expression of transformed cells in carcinogen-treated rodent cells and decreases the time required to observe clear evidence of the neoplastic or malignant phenotype by 2-8 wk or more. Retrovirus-infected Fischer rat embryo cells, uninfected Balb/c 3T3 mouse cells and Syrian hamster embryo cells in monolayer culture were treated with the chemical carcinogens, dimethylbenzanthracene, benzo[a]pyrene or N-methyl-N'-nitro-N-nitrosoguanidine, following a protocol appropriate to each cell type. The cultures were divided into two groups, one seeded directly onto a plastic surface, and the other suspended in liquid medium over agar before seeding onto a plastic surface. In all three cell types incluson of the suspension phase accelerated chemically induced transformation as indicated by clonogenicity in soft agarose (rat, mouse and hamster cells) and by morphological transformation and formation of tumours in athymic nude mice (hamster cells).