Induction of the p75NTR by Aryl Propionic Acids in Prostate Cancer Cells

Epidemiologic studies show that patients chronically consuming nonsteroidal anti-inflammatory drugs (NSAID) for arthritis exhibit a reduced incidence of prostate cancer. In addition, some NSAIDs show anticancer activity in vitro . NSAIDs exert their anti-inflammatory effects by inhibiting cyclooxygenase (COX) activity; however, evidence suggests that COX-independent mechanisms mediate decreased prostate cancer cell survival. Hence, we examined the effect of selected aryl propionic acid NSAIDs and structurally related compounds on the decreased survival of prostate cancer cell lines PC-3, DU-145, and LNCaP by induction of the p75 protein. p75 has been shown to function as a tumor suppressor in the prostate by virtue of its intracellular death domain that can initiate apoptosis and inhibit growth. The most efficacious compounds for induction of p75 and decreased survival, in rank-order, were R-flurbiprofen, ibuprofen, oxaprozin, fenoprofen, naproxen, and ketoprofen. Because R-flurbiprofen and ibuprofen exhibited the greatest efficacy, we examined their dose-dependent specificity of induction for p75 relative to other members of the death receptor family. Whereas treatment with R-flurbiprofen or ibuprofen resulted in a massive induction of p75 protein levels, the expression of Fas, p55, DR3, DR4, DR5, and DR6 remained largely unchanged. Moreover, transfection of either cell line before Rflurbiprofen or ibuprofen treatment with a dominant negative form of p75 to antagonize p75 activity or p75 small interfering RNA to prevent p75 protein expression rescued both cell lines from decreased survival. Hence, R-flurbiprofen and ibuprofen selectively induce p75-dependent decreased survival of prostate cancer cells independently of COX inhibition. [Cancer Res 2007;67(7):3254–62]