Expression Of COX-2 Gene In Human Prostate Cancer Cells And The Effect Of Selective COX-2 Inhibitor

Background: Cyclooxygenase(COX) is the rate-limiting enzyme in the synthesis of prostaglandins(PGs). Two isoforms of COX have been identified: COX-1 is constitutively expressed in most tissue and considered a housekeeping gene responsible for various physiological functions such as cytoprotection of the gastric mucosa, regulation of renal blood flow and platelet aggregation. Whereas COX-2, which can undergo rapid induction in response to a variety of stimuli, including tumor promoters, carcinogenes, cytokines and growth factors as an inducible immediate-early gene and increase the PGs production such as PGEi, may have various other functions in addition to its well-known role in inflammatory reactions. Many studies indicated that overexpression of COX-2 in patients with malignant tumors such as colon, gastric, lung and bladder cancers in recent years and there are evidences showing correlation between COX-2 overexpression and the development and progression of malignant tumors. Moreover, a number of clinical and epidemiological studies suggest that the nonsteroidal anti-inflammatory drugs (NSAIDs) induce a significant regression of colonic polyps in patients with familial adenomatous polyposis and reduce the risk of colon cancer. Thus, NSAIDs may be a new way of chemoprevention and chemotherapy for human malignant tumors.Prostate cancer is one of the most common malignant diseases and a leading cause of death in much of the developed world especial in American. In China, more and more patients with prostate cancer have been diagnosed and the morbidity of prostate cancer is steady increasing. Thus, it is important to understand the mechanism of prostate cancer development and provide practical measures for treatment, prevention and early detection. There are evidences that COX-2 and its selective inhibitors correlate with prostate cancer as other malignant tumors, but the molecular mechanismsof overexpression of COX-2 in malignant tumors and the antitumorigenic effect of selective COX-2 inhibitors is not very clear.The study has been performed to investigate the expression and relationship of COX-2 gene, COX-2 protein and PGEi release in human androgen-nonresponsive PC-3m and PC-3 cells by using in situ hybridization, immunohistochemistry, western blot and ELISA, and the effect of celecoxib, a selective COX-2 inhibitor, on COX-2 protein activity and proliferation of PC-3m and PC-3 cells. The study also elucidated the role of the overexpression of COX-2 to the more highly invasive and metastatic ability of PC-3m cell line than PC-3 cell line.Chapter I: Expression of cyclooxygenase-2 gene in human androgen-nonresponsive PC-3 and PC-3m cells.Objective: To detect the expression of COX-2 in human androgen-nonresponsive PC-3 and PC-3m cells, the role of the COX-2 overexpression to the development and progression of human prostate cancer and the correlation between the COX-2 overexpression and the more highly invasive and metastatic ability of PC-3m cell line than PC-3 cell line.Methods: In situ hybridization, immunohistocheniistry(SABC) and western blot were used to investigate the expression of COX-2 in PC-3 and PC-3m cell lines.Results: 1) COX-2 mKNA expression was observed in PC-3 and PC-3m cells.2) Positive staining of COX-2 and COX-1 protein was seen in PC-3 and PC-3m cells. When compared to COX-1, COX-2 showed a stronger signal at protein level of PC-3 and PC-3m cells.3) There is no stronger signal at mRNA and protein level of COX-2 in PC-3m cells compared in PC-3 cells.Conclusions: 1) There is overexpression of COX-2 in PC-3m cell line as in PC-3 cell line.2) Overexpression of COX-2 contributes to the development and progression of human prostate cancer.3) There seems no correlation between the COX-2 overexpression and the more highly invasive and metastatic ability of PC-3m cell line than PC-3 cell line.