GLUTATHIONE-S-TRANSFERASE MU-1 (GSTM1) - BREAST-CANCER SUSCEPTIBILITYGENE

Glutathione S-transferases mu (GSTM) are dimeric cytosolic isoenzymes. They catalyze glutathione conjugation upon a large variety of electro philes as carcinogens, trans-stilbene peroxide or benzo(a)pyrene. The gene GSTM1 is localized on chromosome 1p13, it has drawn attention bec ause it is absent approximately in 50% of the white population. GSTM1 null genotype seems linked with susceptibility to cancers as lung, col on and bladder cancers. We have studied GSTM1 genotype from 373 primar y breast tumours. The GSTM1 null genotype was found in 50% of the case s (185/373). The incidence study of GSTM1 copy number on clinical and biological variables displayed a significant difference (p < 0.01) of the GSTM1 genotype, showed by the tumour, according to the patient age at diagnosis. The patients younger than 55 years had a percentage mor e important of primary tumours (65%) with a copy number of GSTM1 gene, inferior or equal at one, compared to the patients older than 55 year s (52%). The tumours, whose cathepsin D level was high, presented few copies of GSTM1 gene (p < 0.03). There was no other relationship, part icularly, with tumour size, node status, histological type, hormonal r eceptors, pS2 cytosolic level GSTM1 gene seems protect the mammary gla nd from cancerogenesis with its detoxification role. This result had n ot, pointed out in breast cancer, yet.