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Enhancement of G2 checkpoint function by gelsolin transfection in human cancer cells
1Cancer Institute, Department of Internal Medicine II, Hokkaido University School of Medicine, Kita-15, Nishi-7 Kita-Ku, Sapporo, 060-8638, Japan.
Abstract:
We have previously reported that human gastric (TMK1) and urinary bladder (UMUC2) cancer cell lines show markedly reduced expression of an actin-regulatory protein, gelsolin [S. Moriya et al., (1994), Int. J. Oncol. 5, 1347-1351, M. Tanaka et al. (1995), Cancer Res. 55, 3228-3232]. When gelsolin expression is restored by transfection, cancer cells lost tumorigenicity in vivo [M. Tanaka et al. (1995), Cancer Res. 55, 3228-3232]. Here, we show that gelsolin-overexpressing TMK1 and UMUC2 cells are more resistant to UVC irradiation. Increased resistance is associated with increases in the proportion of cells in the G2 phase of the cell cycle compared to similarly treated control neotransfectants. After UVC irradiation, synchronized gelsolin-overexpressing UMUC2 cells had a prolonged S phase followed by delayed G2 accumulation compared to neotransfected UMUC2 cells as determined by cell cycle analysis. The levels of cyclin B1 and cdk1 histone H1 kinase activity in gelsolin transfectants remained low during S and early G2 phase and the production of diacylglycerol induced by UVC was reduced in gelsolin transfectants compared to neotransfectants. These observations suggest that gelsolin enhances G2 checkpoint function of cells through lipid metabolism, leading to UVC resistance. Considered together with recent evidence that radiation clastogenesis and chemical carcinogenesis are cell-cycle-dependent, down regulation of gelsolin may lead to the malignant transformation of human gastric or urinary bladder cancers by attenuating G2 checkpoint function.
Insights
Gelsolin, an actin-regulatory protein, enhances cancer cell resistance to UVC irradiation by strengthening the G2 cell cycle checkpoint, potentially through lipid metabolism. Reduced gelsolin may promote cancer development.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Human gastric (TMK1) and urinary bladder (UMUC2) cancer cell lines exhibit significantly reduced gelsolin expression.
- Restoring gelsolin expression in cancer cells leads to a loss of tumorigenicity in vivo.
- Gelsolin is an actin-regulatory protein crucial for cellular functions.
Purpose of the Study:
- To investigate the role of gelsolin in cellular resistance to UVC irradiation.
- To elucidate the mechanisms by which gelsolin influences cell cycle progression and DNA damage response.
- To explore the potential link between gelsolin downregulation and cancer malignant transformation.
Main Methods:
- Gelsolin expression was restored in TMK1 and UMUC2 cancer cell lines via transfection.
- Cellular resistance to UVC irradiation was assessed in gelsolin-overexpressing and control cells.
- Cell cycle analysis (including S and G2 phase progression) was performed using flow cytometry.
- Levels of cyclin B1, cdk1 histone H1 kinase activity, and diacylglycerol production were measured.
Main Results:
- Gelsolin-overexpressing cells demonstrated increased resistance to UVC irradiation compared to control cells.
- Increased resistance correlated with a higher proportion of cells in the G2 phase of the cell cycle.
- Gelsolin-overexpressing cells exhibited a prolonged S phase and delayed G2 accumulation after UVC exposure.
- UVC-induced diacylglycerol production was reduced in gelsolin transfectants, and cyclin B1/cdk1 activity remained low during S/G2 phases.
Conclusions:
- Gelsolin enhances the G2 checkpoint function, contributing to UVC resistance, potentially via modulation of lipid metabolism.
- Downregulation of gelsolin may attenuate G2 checkpoint function, facilitating malignant transformation in gastric and urinary bladder cancers.
- Gelsolin plays a significant role in DNA damage response and cell cycle regulation, impacting cancer progression.