RETINOIDS & RECEPTORS IN BLADDER CANCER CHEMOPREVENTION

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DESCRIPTION: (Applicant's Description) Bladder cancer is the 6th most common cancer in the developed world. More than 50,000 new cases of bladder cancer and 11,200 deaths from this cancer occur each year in the United States. Bladder carcinogenesis, like oral premalignancy, is an excellent model for chemopreventive study. Natural and synthetic retinoids have been tested as chemopreventive and chemotherapeutic agents against oral tumors, but the effects of these retinoids on bladder cancers are not well documented. The objective of the proposed study is to explore the feasibility of using natural or synthetic retinoids in the prevention and treatment Of bladder cancer and to investigate the mechanisms of retinoids in this setting. The effect of different retinoids on cell growth, differentiation, apoptosis, and expression of retinoic acid receptors (RARs) in bladder cancer cell lines and normal bladder epithelial cells in short-term cultures will be studied. The hypotheses are: a) retinoids inhibit the growth of bladder cancer cells partially through the induction of apoptosis; b) RARs, especially RARB, play a role in regulating the growth and differentiation of bladder cancer cells; and C) some receptors are down-regulated in certain bladder cancers and can be up-regulated by retinoids in vivo. The hypotheses will be examined by fulfilling the following specific aims: 1) to evaluate the effects of different retinoids on growth and differentiation in normal bladder epithelial cells and bladder cancer cells by examining morphology, cell cycle, and the expression of cytokeratins 4, 7, 8, 13, 18, and 19 using western blotting; 2) to determine the effects of different retinoids on the induction of apoptosis in bladder cancer cells by using DNA fragmentation, propidium iodide staining, and terminal deoxynucleotidyl transferase assays and the effects of combinations of RAR-selective and retinoid X receptor (RXR)-selective retinoids on growth inhibition and apoptosis to find possible additive or synergistic actions of these compounds; 3) to examine the expression of retinoid receptors and their induction by different retinoids in normal bladder epithelial cells and bladder cancer cells by using reverse-transcriptase polymerase chain reaction and western blotting to determine the relationship between receptor expression and the chemopreventive effect of different retinoids; and 4) to analyze the expression of retinoid receptors in bladder cancer specimens before and after chemoprevention with 4-(hydroxyphenyl)retinamide (4HPR) by in situ hybridization and polymerase chain reaction. The results of these studies are expected to increase our understanding of the mechanisms of action and potential usefulness of new retinoids in bladder cancer chemoprevention.