IMPROVED DETECTION OF LOSS OF HETEROZYGOSITY AT RETINOBLASTOMA GENE LOCUS IN HUMAN BREAST-CARCINOMA

Loss of heterozygosity (LOH) at the retinoblastoma (Rb) gene locus was investigated in 33 breast carcinomas by polymerase chain reaction sin gle-strand conformation polymorphism (PCR-SSCP) analysis after tumor c ell enrichment by cell sorting. The efficacy of cell sorting was evalu ated by comparing the results of PCR-SSCP with and without cell sortin g. Ten of 17 (59%) informative cases showed LOH at this locus by cell sorting combined with PCR-SSCP, although LOH was detectable in six (35 %) cases without cell sorting. Flow cytometry and histologic examinati on revealed that this underestimation may occur when the tumor cell po pulation is less than 50% in the specimens analyzed. It is concluded t hat LOH of the Rb gene occurs more frequently in human breast carcinom a than previously thought, and thus may contribute significantly to th e development and/or progression of this tumor.