Plasmodium induced by SU6656, an Src family kinase inhibitor, is accompanied by a contractile ring defect

We have shown that SU6656, a potent Src family kinase inhibitor, has the ability to induce multinucleation at a high frequency in diverse cells: rat skin fibroblasts, bone marrow adherent cells, 5F9A mesenchymal stem cell-like clones, 2C5 tracheal epithelial cells and MDCK epithelial cells from dog kidney. To gain insight into the mechanism of multinucleation, we observed the process by time-lapse and confocal microscopy. These multinuclei generally seem to exist independently in one cell without any connections with each other. By time-lapse microscopy, multinucleated cells were found to be formed through the mechanism of plasmodium: karyokinesis without cytokinesis. The observation of EGFP-actin transfected cells by time-lapse confocal laser scanning microscopy suggested that plasmodium occurred with deficient contractile ring formation. Although we examined the differentiation of these cells, the multinucleated cells could not be categorized into any type of cell in vivo known to exhibit multinuclei.