In vitro transformation of submandibular gland epithelial cells and fibroblasts of adult rats by methylcholanthrene.

Rat salivary gland epithelial cell cultures were initiated and maintained by the avoidance of trypsin in the early passages. These cells and fibroblasts were treated with 3-methylcholanthrene and 7,12 dimethylbenzanthracene according to estab lished protocols. The epithelial cell lines were remarkably susceptible to the toxicity of the hydrocarbons for their first 15 to 20 passages. After the 20th passage, the epithelial cells were better able to survive hydrocarbon toxicity and were capable of being subcultured. Ten to 12 weeks after treatment, epithelial lines and fibroblasts showed increased growth rate and piling up in culture. They produced tumors upon inoculation into syngeneic weanling hosts. These tumors were transplantable and showed clear-cut carcinomatous or sarcomatous morphology. To date, 18 months after the start of the study, no evidence of transformation of untreated or dimethyl sulfoxide-treated control cells has been seen in either fibroblast or epithelial lines.