In Vivo and in Vitro Methylcholanthrene Carcinogenesis in Diffusion Chambers

Two-compartment diffusion chambers containing murine fibroblasts and a 5% (150 μg) or 1% (30 μg) MCA-discs were placed either in the peritoneal cavity of syngeneic adult mice or incubated in vitro. After 4–28 weeks of culture, groups of 5–6 DC's were recovered at 4 weeks intervals, the MCA discarded, and the contents individually implanted into immunodepressed syngeneic mice. The carcinogen displayed a strong cytotoxicity in vitro but not in vivo with both doses. On the whole, when 5% MCA was applied sarcomas appeared in 22/23 mice implanted with cells of the in vivo DC cultures and in 11/16 mice which received the in vitro cultured cells; with the lower dose, the in vivo induced tumors were 19/22 and the in vitro ones 6/12. In all groups the tumor outgrowth into the assay animals was inversely correlated with the time of exposure to MCA during the culture period.