“Mitotic Slippage” and Extranuclear DNA in Cancer Chemoresistance: A Focus on Telomeres

Abstract

Mitotic slippage (MS), the incomplete mitosis that results in a doubled genome in interphase, is a typical response of TP53-mutant tumors resistant to genotoxic therapy. These polyploidized cells display premature senescence and sort the damaged DNA into the cytoplasm. In this study, we explored MS in the MDA-MB-231 cell line treated with doxorubicin (DOX). We found selective release into the cytoplasm of telomere fragments enriched in telomerase reverse transcriptase (hTERT), telomere capping protein TRF2, and DNA double-strand breaks marked by γH2AX, in association with ubiquitin-binding protein SQSTM1/p62. This occurs along with the alternative lengthening of telomeres (ALT) and DNA repair by homologous recombination (HR) in the nuclear promyelocytic leukemia (PML) bodies. The cells in repeated MS cycles activate meiotic genes and display holocentric chromosomes characteristic for inverted meiosis (IM). These giant cells acquire an amoeboid phenotype and finally bud the depolyploidized progeny, restarting the mitotic cycling. We suggest the reversible conversion of the telomerase-driven telomere maintenance into ALT coupled with IM at the sub-telomere breakage sites introduced by meiotic nuclease SPO11. All three MS mechanisms converging at telomeres recapitulate the amoeba-like agamic life-cycle, decreasing the mutagenic load and enabling the recovery of recombined, reduced progeny for return into the mitotic cycle.

The Role of the Meiotic Component in Reproduction of B-RAF-Mutated Melanoma: A Review and “Brainstorming” Session

“…Although currently the study of IM in human cancer is in infancy [62], the IM related to telomere DSBs well fits several peculiarities found in tumors: cellular senescence linked to telomere attrition, polyploidy associated with cellular senescence, mitotic slippage, reprogramming, and alternative telomere lengthening characteristic for some cancers [62]. We proposed a hypothesis that ALT-associated PML bodies in mitotic slippage of tumor cells may serve as a site for IM recombination repair [177]. Interestingly, the meiotic genes involved in the homology search and recombination RAD21L (Rec8 paralog) and Hop2-Mnd1 heterodimer (RAD51-dependent) were found associated with ALT [178,179].…”

“…While the majority of somatic cells are deficient in active telomerase, cancer cells not only can reactivate telomerase, but can also initiate a mechanism of the alternative telomere maintenance (ALT) in the absence of telomerase activity [176] or undergo transient ALT [177]. Some meiosis genes were found associated with supposed homology search in ALT [178,179].…”

“…The latter is often overlooked [189] as being hidden due to the low proportion in relation to the mitotic cycles. The ploidy cycle of giant cells associated with senescence reprogramming becomes clearly manifested in resistant tumors after high dosage DNA damage with anticancer drugs and ionizing irradiation [177,[196][197][198]. Therefore, cancer research needs prolong follow up of individual cells and ploidy measurements [177,191,199,200].…”

Improved Autophagic Flux in Escapers from Doxorubicin-Induced Senescence/Polyploidy of Breast Cancer Cells

“…In our previous studies, by using an immunostaining method, we showed that giant cells, which originate due to the mitotic slippage, eventually acquired an amoeboid phenotype and bud the depolyploidized progeny, restarting the mitotic cycling [29]. Here, we show some more pictures which illustrate aberrant mitosis and cell budding (Figure 4a We extended our studies by using live cell imaging, employing two different methodsholographic microscopy (HoloMonitor4, LabSoft, Warsaw, Poland) and scanning disc confocal microscopy (Zeiss, Oberkochen, Germany).…”

“…issue [29] ( Figure S1a). Namely, we treated cells for one day (D1) with 100 nM doxorubicin (dox), which yielded the highest number of SA-β-gal-positive cells without a cytotoxic effect.…”