Uncontrolled nuclear division in normal x transformed somatic cell hybrids.

Uncontrolled nuclear division (UND), as indicated by progressive multinucleation when cell division is inhibited by cytochalasin B, is a very characteristic property of transformed cells growing in vitro. In an attempt to determine the genetic basis for this transformation phenotype we have produced a series of somatic cell hybrids between different transformed and normal cells. In all hybrids there was suppression of UND but in some this was only transient. In hybrids between transformed human cells and mouse 3T3 cells, UND was only re-expressed when the human parental cell line had been transformed by SV40 virus. The results lend tentative support to the suggestion that cellular mechanisms involved in the induction and suppression of UND may not be the same in all cell lines.