Double minutes are frequently found in ovarian carcinomas.

Double minutes (dmins) are acentric chromosomal-like entities that are important in the etiology of cancer because they are known to harbor amplified oncogenes and drug resistance genes. Because dmins can be unequally partitioned at mitosis they have the ability to confer genetic diversification rapidly. Selective pressures operative in vitro may be quite different than those in vivo; therefore, tumor cells which harbor dmins could be selected against during short-term in vitro propagation. We wanted to determine the incidence of dmins in human ovarian cancer cells obtained from fresh ovarian specimens with an absolute minimum of culture time (6-24 hours). In "direct" chromosomal preparations obtained from these clinical specimens we found dmins present in 88% of these samples. This remarkable finding that dmins are found so frequently in ovarian cancers underscores the importance of gene amplification in human tumor biology. Therefore, the presence of dmins in patient specimens indicates that these unstable genetic elements may play a significant role in the maintenance or progression of malignancy.