Radiosensitive melanoma cell line with mutation of the gene for ataxia telangiectasia.

The human melanoma cell lines MM96L, A2058 and HT144 were examined for sensitivity to ionizing radiation and UVB radiation. HT144 demonstrated a significant increase in sensitivity to ionizing and UVB radiation compared with the MM96L and A2058 cells. Sensitivity to both agents was associated with susceptibility to apoptosis. Using a protein truncation assay, a mutation for the gene for ataxia telangiectasia (ATM) was identified in HT144 cells. This was confirmed to be a homozygous mutation by subsequent sequencing of the abnormal region. Protein truncation assay of the other two cell lines showed no abnormality. The results suggest that somatic mutation of the A-T gene may be important in determining tumour radiosensitivity.