SCE and UDS studies in a family with retinoblastoma: a case study

The frequencies of both spontaneous and mitomycin C (MMC)-induced sister chromatid exchanges (SCE) were analyzed in mixed lymphocyte cultures from a kindred with retinoblastoma. Both the affected daughter and male proband, as well as two normal controls, were studied. No differences were observed in the spontaneous or in the MMC-induced SCE frequencies obtained from the peripheral lymphocytes of these patients compared to the normal controls. Unscheduled DNA synthesis (UDS) was observed in the lymphocytes treated with varying concentrations of both MMC and M-methyl-N-nitro-N-nitrosoguanidine (MNNG). Whereas no differences were observed in the rate of [3H]thymidine incorporation in the retinoblastoma-derived lymphocytes exposed to MMC when compared to the controls, differences were seen in the response to MNNG. Our data suggest that cells from these retinoblastoma patients respond like normal cells to damage induced by MMC, but that they are unable to repair damage induced by MNNG.