Growth inhibition and transformation of a human fetal tracheal epithelial cell line by long-term exposure to diethylnitrosamine

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Abstract
In order to obtain more information on the in vitro transformation of human cells, a human fetal tracheal epithelial cell line (FHET16/5) was exposed for a long time to diethylnitrosamine (DEN). In 20 passages, this cell line (diploid, male) maintained strong immunohistochemical reactivity for carcino-embryonnic antigen and wool merokeratin; it was negative for vimentin. The cells contained PAS-positive mucous substances and ultrastructurally were found to have desmosomelike attachments. Treatment of the cells was with 0.3% dimethyl sulphoxide (DMSO), or DMSO with 150, 450, 1000 or 2000 μg/ml of DEN. It was started at the ninth passage and continued for six passages over 9 weeks for the control (DMSO) and the three lowest control doses of DEN, and for three passages over 9 weeks for the 2000 μg/ml DEN group. Cells grown for 13 days after the end of treatment were plated in soft agar and injected subcutaneously in nude mice. The frequency of anchorage-independent colonies grown in soft agar was directly related to DEN dose. Colony-forming efficiency, as an expression of toxic effect, was also dose dependent. Autoradiographically detected unscheduled DNA synthesis indicated an association between anchorage-independent transformation and DNA alterations induced by DEN. Cells injected into nude mice did not produce tumours during a 6-month period, but invasiveness was observed when cells from the 2000 μg/ml DEN group were transplanted on the dermis of cultured chick embryo skin. The results indicate that DEN causes anchorage-independent transformation accompanied by unscheduled DNA synthesis in a fetal human tracheal epithelial cell line.