Several investigators have reported the generation of androgen independent cell clones that are not only capa ble of growing in the absence of androgen, but also secrete IL 8. We reported previously, that forced expres sion of IL 8 in androgen responsive cells leads to andro gen independent cell growth and up regulation of several key selleck chemical Panobinostat attributes of invasion and metastasis. In addition, over expression of IL 8 in IL 8 secreting AIPC cells causes them Inhibitors,Modulators,Libraries to grow as more aggressive and angiogenic tumors in vivo. However, the mechanism of growth advantage rendered by constitutive IL 8 production, with out over expression, is not delineated. For example, earlier studies attributed most of Inhibitors,Modulators,Libraries the tumor growth promoting activities of IL 8 to its effect on angiogenesis, not the sur vival.

We hypothesized that IL 8 is a survival fac tor that not only promotes proliferation pathway, but also controls apoptotic pathway, due to its interaction with protein Inhibitors,Modulators,Libraries kinase B and NF Inhibitors,Modulators,Libraries kB. The focus of the present report is to demonstrate the contribution of IL 8 in prostate cancer cell survival, invasion and resistance to chemotherapeutic drugs in two AIPC cell lines, PC 3 and DU145 by RNA interference. Results Effect of siRNA directed IL 8 silencing in AIPC cells Transfection of PC 3 and DU145 cells with Smartpool siRNA, directed against IL 8 mRNA reduced the expres sion of IL 8 mRNA in a dose dependent manner at a concentration range of 25 nM to 100 nM. How ever, non target, scrambled sequence siRNA and IL 8 siRNA, both, showed off target toxicity at 100 nM.

At 50 nM, C siRNA did not cause an alteration in cell viability, or IL 8 mRNA, but transfection with 50 nM IL 8 siRNA caused 98% and 92% decrease in IL 8 mRNA levels in PC 3 and DU145 cells, respectively. Fur thermore, we observed Inhibitors,Modulators,Libraries mean decreases of 92% and 85% in secreted IL 8 levels at 72 h after transfection in PC 3 and DU 145 cells, respectively. IL 8 depletion causes inhibition of PC selleck inhibitor 3 and DU145 cells proliferation Reduction of IL 8 expression by transfection with 50 nM IL 8 siRNA caused a significant decrease in cell viability. Decrease in cell viability was measured with an MTT reduction assay, 48 h following transfection. Cell viability decreased by 30 5. 2% in PC 3 and 28 4. 7% in DU145 cells, respectively, to that of mock transfection. As shown in Fig. 2A, C siRNA had no significant effect on cell prolif eration in either cell lines. Furthermore, IL 8 siRNA had no effect on the proliferation of androgen responsive, IL 8 non secreting LNCaP cells. Since siRNA mediated gene silencing lasts two to four days in cell culture, we did not use clonogenic survival assays or generate cell growth curves to determine the long term growth inhibition.