COMPARISON OF SPONTANEOUS AND INDUCED MUTATION-RATES IN AN IMMORTALIZED HUMAN BRONCHIAL EPITHELIAL-CELL LINE AND ITS TUMORIGENIC DERIVATIVE

To determine the relationship between neoplastic transformation and in creased genetic instability, spontaneous and induced mutation rates we re compared in a nontumorigenic, immortalized human bronchial epitheli al cell line (NL20) and a tumorigenic cell line (NL20T) spontaneously derived from the NL20 line. Using the hypoxanthine phosphoribosyltrans ferase (HPRT) locus as a marker for determining mutation rate, fluctua tion analysis was utilized to evaluate the spontaneous mutation rate. Induced mutation rates were determined for each cell line after N-meth yl-N'-nitro-N-nitrosoguanidine exposure. Both the spontaneous and indu ced mutation rates were noted to be significantly higher in the nontum origenic NL20 cell line. These findings suggest that increasing geneti c instability, as measured by spontaneous or induced mutation rate in the HPRT locus, does not correlate with tumorigenicity in these cells.