Tetraploid cells produced by absence of substrate adhesion during cytokinesis are limited in their proliferation and enter senescence after DNA replication

Abstract

Tetraploidy has been proposed as an intermediate state in neoplastic transformation due to the intrinsic chromosome instability of tetraploid cells. Despite the identification of p53 as a major factor in growth arrest of tetraploid cells, it is still unclear whether the p53-dependent mechanism for proliferation restriction is intrinsic to the tetraploid status or dependent on the origin of tetraploidy. Substrate adherence is fundamental for cytokinesis completion in adherent untransformed cells. Here we show that untransformed fibroblast cells undergoing mitosis in suspension produce binucleated tetraploid cells due to defective cleavage furrow constriction that leads to incomplete cell abscission. Binucleated cells obtained after loss of substrate adhesion maintain an inactive p53 status and are able to progress into G1 and S phase. However, binucleated cells arrest in G2, accumulate p53 and are not able to enter mitosis as no tetraploid metaphases were recorded after one cell cycle time. In contrast, tetraploid metaphases were found following pharmacological inhibition of Chk1 kinase, suggesting the involvement of the ATR/Chk1 pathway in the G2 arrest of binucleated cells. Interestingly, after persistence in the G2 phase of the cell cycle, a large fraction of binucleated cells become senescent. These findings identify a new pathway of proliferation restriction for tetraploid untransformed cells that seems to be specific for loss of adhesiondependent cytokinesis failure. This involves Chk1 and p53 activation during G2. Inhibition of growth and entrance into senescence after cytokinesis in suspension may represent an important mechanism to control tumor growth. In fact, anchorage independent growth is a hallmark of cancer and it has been demonstrated that binucleated transformed cells can enter a cycle of anchorage independent growth.

The ISWI ATPase Smarca5 (Snf2h) Is Required for Proliferation and Differentiation of Hematopoietic Stem and Progenitor Cells

“…), which further aggravated the anemic phenotype. Polyploidy was also previously shown to increase tolerance to mitotic errors and may result in appearance of binucleate‐like cells that were also readily observable in the mutant FLs. Activation of p53 and its program including induction of p21 as a consequence of polyploidy has been observed experimentally upon addition of microtubule assembly inhibitors .…”

Tetraploidy in cancer and its possible link to aging

“…In general, tetraploidization leads to p53 stabilization, resulting in cell cycle arrest, cellular senescence, or apoptosis, thus suppressing the proliferation of tetraploid cells (Figure ). Consequently, aneuploidization after tetraploidization is observed mainly in p53‐inactivated cells .…”

“…In a recent stochastic model recapitulating karyotypic evolution in cancer cells, the near-triploid state commonly seen in cancer cells was shown to be achieved from both diploid and tetraploid precursors, but tetraploid cells reached the state more efficiently than diploid cells because the survival cost to achieve the state is smaller in tetraploid cells compared to diploid cells. 28 In general, tetraploidization leads to p53 stabilization, resulting in cell cycle arrest, 29-34 cellular senescence, 35 or apoptosis, 36 thus suppressing the proliferation of tetraploid cells (Figure 1). Consequently, aneuploidization after tetraploidization is observed mainly in p53-inactivated cells.…”

Heterogeneity in sarcoma cell lines reveals enhanced motility of tetraploid versus diploid cells

“…In normal tissues, protective mechanisms insure that tetraploidization does not happen [1, 19, 38] and if an accident occurs the resulting tetraploid cells are rapidly eliminated [39, 40]. Nonetheless, cycling tetraploid cells with supernumerary centrosomes and aberrant mitoses are observed at very early stages of tumorigenesis [10, 41–43] and surviving tetraploid cells were proposed to trigger chromosome instability (CIN) and aneuploidy in absence of TP53 -mediated G1 checkpoint [12, 18, 24, 44, 45].…”