The c-erbB-2 oncogene amplification by competitive PCR in aneuploid cell clones flow sorted from breast cancer samples

The amplification of c-erbB-2 oncogene has been reported to have clinical r elevance as a prognostic index in breast cancer. However, controversies sti ll remain about its interpretation, mainly due to the inaccuracy of methods used for this purpose and to the unpredictable variability of the ratio be tween cancer and normal cells. Accurate quantitative assay, combined with s trategies for selection or enrichment of tumor cell populations, could shed a new light on the relationships between molecular alterations and their c linical relevance. In this study, amplification of c-erbB-2 was measured by competitive PCR in 21 aneuploid breast cancers using a multiple DNA compet itor both in whole homogenized cancer cells and in aneuploid enriched clone s obtained after flow cytometry cell sorting. Most breast cancers (10/12) c arrying c-erbB-2 oncogene amplification showed a significant increase in co py number in sorted aneuploid clones, and 2/9 apparently not amplified in b asal samples were found to be amplified after being sorted for the aneuploi d population. A general concordance between amplification and c-erbB-2 over expression was found. The mean degree of amplification in sorted aneuploid clones is increased in breast cancers with the highest levels of c-erbB-2 p rotein overexpression. These data indicate that in breast cancers the ampli fication of c-erbB-2 oncogene is mainly associated with aneuploid cells.