Expression Of COX-2 In Renal Cell Carcinoma Cells And Inhibitive Effect Of Non-steroid Anti-inflammatory Drugs NS398 On Renal Cell Carcinoma Cells

ObjectiveCarcinogenesis in humans has been shown to be inhibited by non - steroidal anti - inflammatory drugs ( NSAIDs ). The suppression of prostaglandin ( PG ) biosynthesis via inhibition of the corresponding cyclooxygenase ( COX ) by NSAIDs in thought to be the main molecular mechanism for their antineoplasia effect. Such data have promted the examination of expression of COX in human cancer tissues. Two forms of COX, COX - 1 and COX - 2, which can convert arachidonic acid to prostaglandins, have been identified. COX - 1 is constitu-tively expressed in most tissues, at a relatively stable level, and it exerts diverse homeostatic functions, such as protecting the gastrointestinal tract from injury and regulating renal blood flow. In contrast, COX - 2 is undetectable in most normal tissues. It is induced by cytokines, growth factors, oncogenes, and tumor promoters, and therefore contributes to the synthesis of prostaglandins in inflamed and malignant tissues.Preview studies have shown that most cancer cells are found to exhibit over - expression of COX - 2, which can stimulate cellular division and angiogenesis and inhibit apoptosis. NS398, one of the selective COX - 2 inhibitors, has been shown to inhibit proliferation and induce apoptosis in many human carcinomas. But the detail mechanism is unclear. In this study, we aimed to evaluate the effects of NS398 on cellular proliferation and apoptosis in human renal cell carcinoma (RCC) cell line 786 - 0, and to examine possible mechanisms responsible for the anti - proliferative effects of NS398.MethodsHuman RCC cell line 786 - 0 was grown in culture using standard technique and treated with NS398 at doses of 25jxM, 50jxM, 100|xM, 150jxM and 200jxM respectively. Cellular viability was measured by MTT at 24 and 48h. Flow cytometry was used to detect cell apoptosis after treatment of NS398 at various concentrations for 24hr. The level of PGE2 in 786 - 0 cells was detected by EIA after treatment by NS398 at various concentrations for 24hr. 786 - 0 cells were treated by NS398 at various concentrations for 24hr, then reverse transcription - polymerase chain reaction ( RT - PCR) was used to detect COX - 2mRNA and Bel - 2mRNA, and Western blotting was used to examine the expression of COX - 2 and Bel - 2 at protein levels.ResultsNS398 exhibited significant cell growth inhibition at 24 and 48 hr in the 786 - 0 cells in time - and concentration - dependent manner ( P < 0. 05 ). NS398 significantly induced apoptosis in 786 - 0 cells in dose - dependent manner ( P < 0.05). NS398 significantly inhibited the release of PGE2in 786 - 0 cell at dose - dependent manner (P < 0.05). COX - 2 and Bel - 2 were significantly decreated by NS398 both at mRNA and protein levels.ConclusionsOver - expression of COX - 2mRNA and protein exist in human 786 - 0 RCC cell line and COX - 2 may play a crucial role in carcinogenesis of RCC. NS398 can suppress the proliferation of 786 - 0 RCC cells by induction of apoptosis. There are many mechanisms of NS398 to inhibit proliferation and induce apoptosis in RCC cells. One of the possible mechanisms of NS398 to induce apoptosis in 786 - 0 cells is due to the inhibition of COX - 2, which down - regulated the expression of Bel - 2 and resulted in the increase of apoptosis. PGE2 isan important simulative factor to accelerate carcinogenesis in RCC cells. Inhibition of COX - 2 to reduce the synthesis of PGE2 by NS398 maybe another mechanism to increase apoptosis. The results suggest that COX - 2 may become a new target gene for RCC treatment, and NS398 maybe a potentially effective a-gent against human RCC expressing COX -2.