ATM and breast cancer: Heterozygous carriers of the ataxia-talangiectasia gene ATM have been reported to be at increased risks of breast cancer (Swift et al, 1991; Easton, 1994; Olsen et al, 2001) and there is also evidence that rare HRAS1 alleles may be associated with moderate risks for breast cancer (Krontiris et al, 1993).