ALLELIC IMBALANCE ON CHROMOSOME 13Q - EVIDENCE FOR THE INVOLVEMENT OFBRCA2 AND RB1 IN SPORADIC BREAST-CANCER

Recently, the breast cancer susceptibility gene BRCA2 has been identif ied in chromosome 13q, a region that also contains the retinoblastoma gene RB1. To elucidate a possible role of BRCA2 and RB1 in sporadic br east tumorigenesis, allelic imbalance (AI) at 13q loci was examined in 78 primary sporadic breast tumors. AI was found in 52 - 63% of tumors . Nine tumors showed AI only in the BRCA2 region but not at RBI. Six t umors showed AI at RBI but not in the BRCA2 region. AI in the BRCA2 re gion correlated significantly with aneuploidy (P = 0.032) and AI at RB I with small tumor size (P = 0.025). Our data suggest that BRCA2 and R BI mag be both distinct target loci for AI on chromosome 13 in sporadi c breast cancer.