ИСТИНА

Entosis is a type of cell cannibalism during which one tumor cell invades the other tumor cell. It was shown that invasion occurs with participation of acto-myosin complex and formation of adhesive junctions between outer and inner cells. The fate of inner cell can be different: it can leave the entotic vacuole, divide within it, or be subjected to lysosome-mediated degradation. Entosis is now shown to perturb cytokinesis of outer cell and induce the formation of aneuploid cells. The aim of our work was to determine whether the cells can pass cell cycle phases during entosis. A431 (human epidermoid carcinoma cell line) and MCF7 (human breast adenocarcinoma cell line) cell culture lines were used in this work. The frequency of entotic cells was 0,42 ± 027% in A431 culture and 1,01 ±0,37 % in MCF7 culture. It was shown that cells after detachment from substrate can penetrate the neighboring cell (it took up to 2h). Some cells penetrated at the late telophase. Inner cell could be inside the vacuoles during more than 72 h. Lysosome-mediated degradation is a slow process and takes about 48 hours. Frequently inner cell could leave entotic vacuole and this exit lasted from 30 to 100 min. Inner cells as well as outer cells could synthesize DNA and enter mitosis. S-phase index and mitotic index of the outer cells coincided with corresponding indexes of the whole cell population. Mitotic index of the inner cells was higher, than of the cell population. Probably it was a result of mitosis delay in the inner cells. At the same time the S-phase index of the inner cells was lower that of the cell population. So the entering DNA replication seemed to be disturbed at the entosis. Block of the cell cycle at G1/S and S-phase by hydroxyurea treatment did not affect the entosis frequency. Thus, the data obtained showed that the outer and inner cells could pass different phases of the cell cycle including S-phase and mitosis.