Polyploid/Multinucleated Giant and Slow-Cycling Cancer Cell Enrichment in Response to X-ray Irradiation of Human Glioblastoma Multiforme Cells Differing in Radioresistance and TP53/PTEN Status

Abstract

Radioresistance compromises the efficacy of radiotherapy for glioblastoma multiforme (GBM), the most devastating and common brain tumor. The present study investigated the relationship between radiation tolerance and formation of polyploid/multinucleated giant (PGCC/MGCC) and quiescent/senescent slow-cycling cancer cells in human U-87, LN-229, and U-251 cell lines differing in TP53/PTEN status and radioresistance. We found significant enrichment in MGCC populations of U-87 and LN-229 cell lines, and generation of numerous small mononuclear (called Raju cells, or RJ cells) U-87-derived cells that eventually form cell colonies, in a process termed neosis, in response to X-ray irradiation (IR) at single acute therapeutic doses of 2–6 Gy. For the first time, single-cell high-content imaging and analysis of Ki-67- and EdU-coupled fluorescence demonstrated that the IR exposure dose-dependently augments two distinct GBM cell populations. Bifurcation of Ki-67 staining suggests fast-cycling and slow-cycling populations with a normal-sized nuclear area, and with an enlarged nuclear area, including one resembling the size of PGCC/MGCCs, that likely underlie the highest radioresistance and propensity for repopulation of U-87 cells. Proliferative activity and anchorage-independent survival of GBM cell lines seem to be related to neosis, low level of apoptosis, fraction of prematurely stress-induced senescent MGCCs, and the expression of p63 and p73, members of p53 family transcription factors, but not to the mutant p53. Collectively, our data support the importance of the TP53wt/PTENmut genotype for the maintenance of cycling radioresistant U-87 cells to produce a significant amount of senescent MGCCs as an IR stress-induced adaptation response to therapeutic irradiation doses.

Dormant cancer cells and polyploid giant cancer cells: The roots of cancer recurrence and metastasis

“…The G Alert , spG0, G0 states in quiescence-and/or senescence-like may be an adaptive response of PGCCs to radiation stress. 127,128 Mallin et al 12 showed that PACC (PGCCs) exhibit increased motility and deformability mediated by increased mesenchymal-related protein expression, and that PACC show increased metastatic potential. PGCCs have thicker and longer actin fibres with an abnormal overexpression of actin components compared with the diploid cancer cells, which confers PGCCs a slow yet persistent migratory phenotype.…”

“…Severe DNA damage from chemotherapy or hypoxia induces P53 up-regulation and cells with mutant P53 become aneuploid. 127 Endoreduplication increases the cell size, DNA content and nuclear heterogeneity in response to various stressors. 144,145 In PGCCs, CDK1 and cyclin B1 expression is down-regulated, whereas the expression of P53 is up-regulated.…”

“…G0 cells without Ki‐67 expression are fully quiescent. The G Alert , spG0, G0 states in quiescence‐ and/or senescence‐like may be an adaptive response of PGCCs to radiation stress 127,128 …”

“…The p16/pRb and P53/p21 pathways can regulate the expression of CDK. Severe DNA damage from chemotherapy or hypoxia induces P53 up‐regulation and cells with mutant P53 become aneuploid 127 . Endoreduplication increases the cell size, DNA content and nuclear heterogeneity in response to various stressors 144,145 .…”

Molecules promoting circulating clusters of cancer cells suggest novel therapeutic targets for treatment of metastatic cancers

“…Interestingly, interaction with white blood cells also correlates with mixed Epithelial-mesenchymal phenotype and cancer cells polyploidy ( 21 , 68 , 69 ) that play a key role in cancer resistance to treatment and metastasis ( 37 , 70 – 72 ).…”