Double minutes in prematurely condensed chromatin of human tumor cells.

Comparative studies on the occurrence of double minutes (DMs) were performed on metaphases and prematurely condensed interphases (G1, G2) of cells from 28 cancerous effusions of 24 carcinoma patients. In 21 of these effusions, agreement between metaphase and prematurely condensed chromatin (PCC) data was obtained concerning occurrence or nonoccurrence of DMs (10 DM positive, 11 DM negative). In two cases, DMs were observed in metaphases only, whereas in five cases, they were found in interphases only. In normal cells, no DMs could be found, neither in metaphase nor in PCC. No causal correlation of the occurrence of DMs and cytostatic therapy was found. The data suggest that cytogenetic screening of prematurely condensed interphase cells from human tumors or cancerous effusions provides a valuable method for estimating the incidence of gene amplification in malignant cells, particularly in those with poor mitotic yield.