Abstract
BACKGROUND: Our previous studies have confirmed that cobalt chloride (CoCl(2)) can induce the formation of polyploid giant cancer cells (PGCCs), which is the key to the heterogeneity of solid tumors. PGCC formation is closely related to the abnormal expression of cell cycle-related proteins and cell fusion. In this study, we investigated the molecular mechanism of PGCCs formation by detecting the expression of cell cycle-related proteins in mutant and wild-type p53 cancer cell lines. METHODS: HEY, BT-549, SKOv3 and MDA-MB-231 cells were treated with CoCl(2) and the cell cycle was detected by flow cytometry. The expression and subcellular localization of cell cycle-related proteins, kinases, and P53 were compared before and after CoCl(2) treatment. Immunoprecipitation was used to analyze the interacting proteins of pCDC25C-Ser216 and pCDC25C-Ser198. The clinicopathologic significances of these cell cycle-related proteins and protein kinases expression were studied. RESULTS: CoCl(2) induced the formation of PGCCs and G2/M arrest. CDC25C, cyclin B1, and CDK1 expressions after CoCl(2) treatment were lower than that in control cells. Cytoplasmic CDC25C was degraded by ubiquitin-dependent proteasome. The expression of P53 and phosphokinases including CHK1, CHK2, PLK1, and Aurora A increased after CoCl(2) treatment. The expression of pCDC25C-Ser216 and pCDC25C-Ser198 depended upon the genotype of p53. The expressions of cell cycle-related proteins and kinases gradually increased with the development of ovarian cancer and breast cancer. CONCLUSION: CHK1, CHK2-pCDC25C-Ser216-cyclin B1-CDK1, and Aurora A-PLK1-pCDC25C-Ser198-cyclin B1-CDK1 signaling pathways may participate in the formation of PGCCs and different phosphorylation sites of CDC25C may be associated with the genotype of p53.