Factors influencing mutation at the hprt locus in T-lymphocytes: studies in normal women and women with benign and malignant breast masses.

A prospective, longitudinal study was performed to test the hypothesis that environmental factors (e.g., diet or cigarette smoking) modulate genetic damage caused by treatment for breast cancer and render these women more susceptible to developing second malignancies. A total of 107 women (49 with breast cancer, 52 with benign breast masses, and 6 normal women) were enrolled. This report describes initial studies at the time of enrollment and disease presentation. Mutant frequency at the hprt locus and cloning efficiency of peripheral blood lymphocytes did not differ significantly among the 3 groups. Mutant frequency increased with age, with a history of cigarette smoking, and with the number of years that current smokers used cigarettes. There was no correlation in women with benign masses between mutant frequency and the incidence of chromosome aberrations (28 women) or sister chromatid exchanges (23 women). A maternal history of breast cancer did not influence mutant frequency. There was no significant relationship between dietary intake of vitamins A, B12, C and E, folacin, selenium, calcium, caffeine, or multivitamin pills, and mutant frequency. Serum folate levels in the deficient range were associated (P = 0.02) with elevated mutant frequencies, whereas SCE rates inversely correlated with serum vitamin B12 levels. These results confirm the importance of age and, less so, cigarette smoking as factors that influence mutant frequency and suggest that a micronutrient, folic acid, may modify genetic damage at the hprt locus. To the extent that somatic mutation contributes to carcinogenesis, these environmental factors may enhance the risk of developing malignant transformation.