Abstract
Cell survival has been measured in normal and Fanconi's anaemia (FA) human fibroblasts after treatment with the bifunctional alkylating agent, nitrogen mustard (HN2). Two FA cell lines exhibited 6- to 10-fold greater sensitivity than the normal cell line. Flow cytometry was used to investigate the effects of HN2 on cell cycle progression of normal and FA cells. After 0.1 microgram/ml HN2 (surviving fraction, s.f. = 0.8) normal cells exhibited an S phase accumulation within 6 h, followed by a transient G2 delay. At higher doses of HN2, the S phase delay became more pronounced and there was considerably greater accumulation of cells in G2. HN2 at 0.01 microgram/ml (s.f. = 0.8) induced no detectable S or G2 delay in FA cells. A higher dose, 0.1 microgram/ml (s.f. = 0.13 and 0.29), again induced no S phase delay, but a gradual accumulation of cells in G2 was observed up to 78 h after treatment. The presence of an S phase delay in normal cells after HN2 treatment may be important in allowing time for DNA repair before completion of DNA synthesis. The absence of such a delay in FA cells suggests that an inability to delay S phase traverse in response to DNA damage from bifunctional alkylating agents may contribute to the sensitivity of FA cells to such drugs.
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