Mechanisms of ploidy increase in human cancers: a new role for cell cannibalism

Aneuploidy is a hallmark of human cancers originating from abnormal mitoses. Many aneuploid cancer cells also have greater-than-diploid DNA content, suggesting that polyploidy is a common precursor to aneuploidy during tumor progression. Polyploid cells can originate from cell fusion, endoreplication, and cytokinesis failure. Recently we found that cell cannibalism by entosis, a form of cell engulfment involving live cells, also leads to polyploidy, as internalized cells disrupt cytokinesis of their engulfing cell hosts. By this mechanism, cannibalistic cell behavior could promote tumor progression by leading to aneuploidy. Here, we discuss cell cannibalism in cancer and other mechanisms that result in the formation of polyploid cancer cells.