Cancer cells that survive checkpoint adaptation contain micronuclei that harbor damaged DNA

Abstract

We have examined the relationship between checkpoint adaptation (mitosis with damaged DNA) and micronuclei. Micronuclei in cancer cells are linked to genomic change, and may induce chromothripsis (chromosome shattering). We measured the cytotoxicity of the cancer drug cisplatin in M059K (glioma fibroblasts, IC50 15 mM). Nearly 100% of M059K cells were positive for histone gH2AX staining after 48 h treatment with a cytotoxic concentration of cisplatin. The proportion of micronucleated cells, as confirmed by microscopy using DAPI and lamin A/C staining, increased from 24% to 48%, and the total micronuclei in surviving cells accumulated over time. Promoting entry into mitosis with a checkpoint inhibitor increased the number of micronuclei in cells whereas blocking checkpoint adaptation with a Cdk inhibitor reduced the number of micronuclei. Interestingly, some micronuclei underwent asynchronous DNA replication, relative to the main nuclei, as measured by deoxy-bromo-uracil (BrdU) staining. These micronuclei stained positive for histone gH2AX, which was linked to DNA replication, suggesting that micronuclei arise from checkpoint adaptation and that micronuclei may continue to damage DNA. By contrast the normal cell line WI-38 did not undergo checkpoint adaptation when treated with cisplatin and did not show changes in micronuclei number. These data reveal that the production of micronuclei by checkpoint adaptation is part of a process that contributes to genomic change.

G2/M-Phase Checkpoint Adaptation and Micronuclei Formation as Mechanisms That Contribute to Genomic Instability in Human Cells

“…Investigation of checkpoint adaptation led to the finding that it causes the formation of micronuclei in cells [ 10 , 11 ]. Micronuclei are distinct from the main nucleus and encapsulate full lagging chromosomes or fragments of chromosomes that are not incorporated in the main nucleus after anaphase [ 12 , 13 , 14 ].…”

“…Micronuclei contribute to genomic instability, and are a characteristic of cancer cells. Cells that undergo checkpoint adaptation show a 50% increase in the number of micronuclei compared with non-treated cancer cells [ 10 , 11 ]. The cells containing micronuclei are able to survive for several cycles, and chromosomes enclosed in these micronuclei could be reunited in the main nucleus of the daughter cells.…”

Accumulation of DNA methylation alterations in paediatric glioma stem cells following fractionated dose irradiation

“…The Alu element is commonly found in repetitive regions. Recently, many environmental factors were shown to alter Alu methylation, which could lead to chromosomal instability resulting in chromosomal rearrangements [46]. We found that loci in long repetitive regions were significantly enhanced in DMPs following 15 and 15 + 3 FDIR, demonstrating that also irradiation can induce such alterations.…”

Expression of γ-H2AX, 53BP1 and Micronuclei as Genome Damage Biomarker of Population in Keang and Salumati Village, Mamuju West Sulawesi Province

“…The process of DNA damage in general and specially in DNA DSB repair are occur in G2 or adaptive checkpoint before the cell entering the mitotic phase. Lewis and Goldstein [24] found that, production of micronuclei were correlated to checkpoint adaptation as part of process that contribute to genomic change. These processes were indicated by high expression of γ-H2AX and 53BP1 foci.…”