ABSTRACT
The ability of mutagens to transform benign papillomas to malignancy in the mouse skin model of multistage carcinogenesis [Hennings et al. Nature 303, 67-68 (1983)] suggests that multiple events may underlie carcinogenic progression, and that mutagenic exposures separated by time can act synergistically. Such synergism may result from initial mutagenic exposure which induces heritable sensitivity to subsequent mutagenic exposures. For example, progeny of X-irradiated V79 cells are hypersensitive to subsequent mutation induced by psoralen plus long-wave ultraviolet light, PUVA [Frank and Williams, Science 216, 307-308 (1982)]. In the present studies 100 to 200 surviving clones of short-wave ultraviolet light (UVC) irradiated V79 cells were assayed for mutation at two loci. Cultures derived from these cells were found to be hypermutable at the hypoxanthine guanine phosphoribosyl transferase (HGPRT) locus following exposure to PUVA, but showed mutant frequencies similar to control cells following UVC challenge at the HGPRT and ATPase loci.