Glucose-regulated stresses cause decreased expression of cyclin D1 and hypophosphorylation of retinoblastoma protein in human cancer cells.
Glucose-regulated stress response of cancer cells occurs during the growth of solid tumors and is induced in culture by treatments with various agents, including 2-deoxyglucose, glucosamine, and calcium ionophore A23187. We previously reported that the three stressors commonly induced cell-cycle arrest in the G1 phase and resistance to antitumor drugs in human cancer A2780 and HT-29 cells. In this study, we investigated the mechanisms of stress-induced G1 arrest by determining the expression of cell-cycle-regulating proteins. Among G1 cyclins and cyclin-dependent kinases (cdk) examined, the expression levels of cyclin D1 preferentially decreased in the stressed cells. A time-course study showed that the decrease in cyclin D1 coincided with the appearance of hypophosphorylated retinoblastoma protein (pRb), which is the growth suppressive form. These findings suggest that the stress-induced G1 arrest is mediated through the down-regulation of cyclin D1-associated kinases (cdk4/6), pRb kinases during G1 phase. This was also supported by decreased cdk4 expression in stressed HT-29 cells. In addition, p21WAF1, a cdk inhibitor, was induced in the stressed cells, particularly A23187-treated cells. A23187, compared with the other stressors, caused extreme pRb hypophosphorylation, suggesting that p21WAf1 is involved in the regulation of pRb phosphorylation in the stressed cells. Our present findings could explain a molecular-based mechanism of a growth-arrested quiescent state and also resistance to chemotherapy of solid tumor cells.
Tomida
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Institute of Molecular and Cellular Biosciences, University of Tokyo, Yayoi, Bunkyo-ku, Japan.
Suzuki
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Kim
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Tsuruo
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D000001:Calcimycin / Q000494:pharmacology; D019938:Cyclin D1; D051358:Cyclin-Dependent Kinase 4; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism*; D003847:Deoxyglucose / Q000494:pharmacology; D016193:G1 Phase / Q000187:drug effects* / Q000502:physiology; D005944:Glucosamine / Q000494:pharmacology; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D019073:HT29 Cells / Q000187:drug effects; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D015513:Oncogene Proteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein / Q000378:metabolism*; D013312:Stress, Physiological
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D018840:HSP70 Heat-Shock Proteins; D008565:Membrane Proteins; D015513:Oncogene Proteins; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; C018551:glucose-regulated proteins; D019938:Cyclin D1; D000001:Calcimycin; D003847:Deoxyglucose; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D005944:Glucosamine