LACK OF CORRELATION BETWEEN ATM PROTEIN EXPRESSION AND TUMOR-CELL RADIOSENSITIVITY

Purpose: Cells derived from individuals in which the ataxia telangiect asia (ATM) gene is mutated are hypersensitive to ionizing radiation. W hether differences in ATM protein levels exist among human malignant g lioma cell lines and whether such differences are correlated with cell ular radiosensitivity were determined. Materials and methods: Polyclon al antibodies were raised to separate regions of the ATM protein. ATM protein expression in human malignant glioma cell lines, SV40 transfor med normal human fibroblasts and SV40 transformed AT fibroblasts was a nalysed by Western blotting. Reverse transcriptase polymerase chain re action (RT-PCR) was used to assess the presence of ATM transcript. Res ults: While ATM protein was detected in all cell extracts, significant differences in the level of expression were observed. There was no ap parent correlation between cellular radiosensitivity and differences i n ATM protein levels in these human glioma cells. Extremely low levels of ATM protein were observed in M059J cells, which provide the only e xample of DNA-dependent protein kinase (DNA-PKcs) deficiency in a cell line of human origin. Conclusions: Variations in the levels of ATM pr otein are insufficient to explain the differences in cellular radiosen sitivity observed in a panel of human malignant glioma cell lines.