Effects of cell fusion on mitomycin C induced SCE levels.

Recent studies have shown that fusion of Bloom syndrome (BS) cells with normal cells results in complete correction of the highly elevated sister chromatid exchange (SCE) level in the former cells. Furthermore, fusion experiments strongly suggested that normalization of the SCE levels in BS cells can be achieved by factors present in the cells of various mammalian species. In the present study, the effects of cell fusion on the elevated SCE levels in mitomycin C (MC) treated normal cells when fused with non-treated normal cells were examined and compared to those obtained through fusion between Bs and normal cells. Evidence is presented that through the increased levels of SCE in Bs cells were normalized by fusion with non-treated normal cells, MC-induced increased levels of SCE were not normalized by fusion with normal cells, and that the mechanism involved in the induction of SCE by exogenous agents is not identical to that leading to spontaneous SCE.