EVIDENCE FOR ALTERED CELL-CYCLE TRAVERSE OF THE NON-MODAL CELLS OF THE HETEROPLOID MCA-11 LINE

Classic stem cell theory states that the growth of heteroploid cell po pulations is due to the proliferation of 'main stemline' cells with mo dal DNA content and chromosome number. Cells with non-modal DNA conten t and chromosome number are thought to be blocked and/or destroyed at mitosis. To test this, we studied two chromosomally stable cell popula tions (mouse bone marrow and WCHE-5 cells) and one heteroploid, chromo somally diverse cell line (MCa-11). The heteroploid MCa-11 cells showe d significant [H-3]dT labelling for cells with DNA contents below the modal G0/G1 peak and above the modal G2 peaks (P<0.001). This was cons istent with the presence of cells with the non-modal DNA content that were engaged in replicative DNA synthesis. A percentage labelled mitos is analysis showed that MCa-11 cells with non-modal DNA content and ch romosome number were able to complete mitosis, although with prolonged pre-karyokinetic time. These results suggest that many non-modal cell s present in heteroploid cell populations are capable of continued pro liferation.