Tamoxifen-induced DNA adducts in leucocytes of breast cancer patients.

Tamoxifen-induced DNA adducts were searched in leucocyte DNA from breast cancer patients. Total white blood cell DNA from tamoxifen-treated and control patients was analysed by 32P-postlabelling using HPLC-radioactivity detection. Rat liver DNA was used as a positive standard. In blinded analysis four of the six treated patients showed DNA adducts; none of the five controls were positive. The identity of fraction as a tamoxifen adduct was confirmed by using different chromatographic systems, each with spiked rat liver samples. The level of adducts in the treated patients was 5.5 adducts/10(9) nucleotides as compared to an apparent level of 1.9/10(9) in the controls.