Differential expression of cell death regulators in response to thapsigargin and adriamycin in Bcl-2 transfected DU145 prostatic cancer cells.
Functional overexpression of Bcl-2 has been reported to confer an anti-apoptotic potential in a variety of cell types. The role of Bcl-2 in epithelial cell-cycle control and in interactions with other cell-cycle regulators is not clearly understood. Its expression has been correlated with the hormono- and chemo-resistant phenotype in advanced prostate cancer. The aim of this study was to investigate the mechanisms through which Bcl-2 mediates increased cytotoxic chemoresistance by assessing alterations in the expression of cell death regulatory molecules. The DU145 human prostatic adenocarcinoma cell line was stably transfected with a Bcl-2 encoding expression plasmid. Two Bcl-2 transfectants, DKC9 and DKC11, were expanded for further study. The effects of Bcl-2 expression on cellular proliferation, cell death (+/- adriamycin or thapsigargin), and expression of cell-cycle/death regulators (p53, PCNA, Bax, Bak, Bcl-X(L)) were evaluated. Compared with controls, Bcl-2 transfectants showed no difference in the rate of proliferation, a decrease in p53 (approximately two-fold), an increase in Bax (approximately two-fold) and PCNA (approximately three-fold), and no change in the levels of Bcl-X(L) and Bak proteins. DKC9 and DKC11 also exhibited a significantly increased chemoresistance to adriamycin (0.0025-5 microM) and thapsigargin (0.0025-5 microM) compared with controls. In the presence of thapsigargin or adriamycin, levels of Bcl-2 and its heterodimeric partner Bax were elevated approximately two-fold with no change in Bak in Bcl-2 transfectants in contrast to controls, where Bak was increased (two-fold). This is the first study to demonstrate that Bcl-2 transfection modulates the expression of mutant p53, Bax, and PCNA in prostate cancer cells. Moreover, Bcl-2 overexpression conferred a significant cytotoxic chemoresistance and altered the balance of expression of death promoters (from Bak, a dominant death promoter in controls, to Bax) in response to thapsigargin and adriamycin.
Chaudhary
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Department of Histopathology, Hammersmith Hospital Campus, Imperial College School of Medicine, Du Cane Road, London W12 0NN, UK. e.lalani@ic.ac.uk
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D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology; D000970:Antineoplastic Agents / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D019254:Genes, bcl-2; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000473:pathology; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; D019284:Thapsigargin; D004317:Doxorubicin