Role Of Cyclooxygenase-2 In The Development And Treatment Of Bladder Cancer

Role of Cyclooxygenase-2 in the Development and Treatment of Bladder CancerObjectives: The mechanism is not very clear during tumorigenesis of bladder cancer. Recent investigation suggests a correlation between cyclooxygenase-2 ( COX-2 ) and tumorigenesis. This study is designed to investigate the role of COX-2 in the development and progression of bladder cancer, and explore the influence of selective COX-2 inhibitor on growth of bladder cancer cell.Methods: 1. Reverse transcriptase-polymerase chain reaction(RT-PCR) and immunohistochemistry was applied to detect the mRNA and protein expression of COX-1,COX-2 in bladder transitional cell carcinoma(BTCC), tissue adjacent to cancer, normal mucosa , mucosa of chronic cysititis and bladder cell line. Furthermore, we compared the COX-2 expression level in tumor with pathologic parameters. 2. COX expression in two bladder cancer cell lines, T24 and 5637, was examined after cells were stimulated with recombinant human epidermal growth factor (rhEGF) alone and combined with selective COX-2 inhibitor SC-58125 or nuclear transcription factor kappaB (NF-κB) inhibitor PDTC. 3. The influence of selective COX-2 inhibitor SC-58125, celecoxib and nonselective COX inhibitor indomethacin on proliferation of bladder cell line T24 was studied by MTT method. To determine the apoptosis of T24 cell line induced by SC-58125, flow cytometry ( FCM ) , DNA ladder electrophoresis and Hoechst33258 fluorescent staining were used. Meanwhile the changes of apoptosis-related Bcl-2 , Bax expression were analyzed by RT-PCR. 4. Cell invasion assay in vitro and RT-PCR were used to determined the effect of SC-58125 on cell invasive ability,matrix metalloproteinase( MMP ) and tissue inhibitor of metalloproteinase ( TIMP ) expression of T24 cell line respectively.Results: 1. COX-2 was expressed in human BTCC as well as in bladder cancer cell lines but was hardly expressed in tissue adjacent to tumor, normal bladder mucosa and mucosa of chronic cysititis. The level of COX-2 expression in BTCC was correlated with tumor stage and grade. COX-1 was mainly expressed in nontumor tissue. 2. After exposure to rhEGF, COX-2 mRNA expression and the level of prostaglandin E2(PGE2) in culture medium increased in both bladder cell lines, but COX-1 mRNA expression in T24 cell line did not changed. SC-58125 had no effect onrhEGF-induced COX-2 upregulation, but could reduce PGE2 synthesis. In contrast, PDTC could decrease expression of COX-2 in response to rhEGF while attenuating PGE2 production. 3. SC-58125, celecoxib and indomethacin could inhibit the proliferation of T24 cell line to a different extent. SC-58125 tened to be more efficacious. All three apoptosis assays showed that apoptosis increased after exposure to SC-58125 in T24 cell line but the expression of apoptosis-related Bcl-2, Bax genes did not changed. 4. SC-58125 could reduce invasion of T24 cell line in vitro and inhibit the expression of MMP-9.Conclusions: 1. COX-2 was overexpressed in bladder cancer and correlated with tumor stage and grade. 2. EGF could induce upregulation of COX-2 and the subsequent production of PGE2 in bladder cancer cells. 3. Selective COX-2 inhibitors could suppress the proliferation and induce apoptosis of bladder cancer cell line. 4. Selective COX-2 inhibitor could inhibit invasion of bladder cell line. The proposed mechanism was correlated with downregulation of MMP-9.