Differential regulation of protein expression, growth and apoptosis by natural and synthetic retinoids.
All-trans retinoic acid (ATRA) can down regulate the anti-apoptotic protein Bcl-2 and the cell cycle proteins cyclin D1 and cdk2 in estrogen receptor-positive breast cancer cells. We show here that retinoids can also reduce expression of the inhibitor of apoptosis protein, survivin. Here we have compared the regulation of these proteins in MCF-7 and ZR-75 breast cancer cells by natural and synthetic retinoids selective for the RA receptors (RARs) alpha, beta, and gamma then correlated these with growth inhibition, induction of apoptosis and chemosensitization to Taxol. In both cell lines ATRA and 9-cis RA induced the most profound decreases in cyclin D1 and cdk2 expression and also mediated the largest growth inhibition. The RARalpha agonist, Ro 40-6055 also strongly downregulated these proteins although did not produce an equivalent decrease in S-phase cells. Only ATRA induced RARbeta expression. ATRA, 9-cis RA and 4-HPR initiated the highest level of apoptosis as determined by mitochondrial Bax translocation, while only ATRA and 9-cis RA strongly reduced Bcl-2 and survivin protein expression. Enumeration of dead cells over 96 h correlated well with downregulation of both survivin and Bcl-2. Simultaneous retinoid-mediated reduction of both these proteins also predicted optimal Taxol sensitization. 4-HPR was much weaker than the natural retinoids with respect to Taxol sensitization, consistent with the proposed requirement for reduced Bcl-2 in this synergy. Neither the extent of cell cycle protein regulation nor AP-1 inhibition fully predicted the antiproliferative effect of the synthetic retinoids suggesting that growth inhibition requires regulation of a spectrum of RAR-regulated gene products in addition even to pivotal cell cycle proteins.
Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5. cpratt@uottawa.ca
M A Christine
MA
Pratt
Minying
M
Niu
Dawn
D
White
D017209:Apoptosis / Q000187:drug effects*; D042846:CDC2-CDC28 Kinases / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002999:Clone Cells / Q000187:drug effects; D019938:Cyclin D1 / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D051034:Inhibitor of Apoptosis Proteins; D008024:Ligands; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009363:Neoplasm Proteins; D017239:Paclitaxel / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D012176:Retinoids / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D016196:S Phase / Q000187:drug effects; D000077022:Survivin; D018808:Transcription Factor AP-1 / Q000378:metabolism
C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D008024:Ligands; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D018168:Receptors, Retinoic Acid; D012176:Retinoids; D000077022:Survivin; D018808:Transcription Factor AP-1; C082925:retinoic acid receptor beta; D019938:Cyclin D1; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D017239:Paclitaxel