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.
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