Abstract 570: Breast cancer chemopreventive activity of a novel amide derivative of sulindac involves inhibition of PDE5, activation of PKG, and attenuation of Wnt/β-catenin signaling

Abstract

Abstract The nonsteroidal anti-inflammatory drugs (NSAIDs) and cyclooxygenase-2 (COX2) inhibitors demonstrate promising chemopreventive activity against a number of cancer types, including breast cancer. Unfortunately, potentially fatal toxicities associated with COX inhibition have precluded the development of these drugs for such indications. However, some studies suggest that their anticancer activity may be due to COX-independent mechanisms, suggesting the ability to target such mechanisms for the development of potentially safer and more effective chemopreventive agents. Here we describe a novel amide derivative of the NSAID sulindac sulfide (SS), termed sulindac sulfide amide (SSA). SSA lacked the ability to inhibit either COX1 or COX2 but demonstrated as much as a twenty-fold increase in potency to inhibit growth and induce apoptosis of breast tumor cells compared to SS. Moreover, SSA was selective for tumor cells, having no measurable effect on apoptosis of nontumorigenic mammary epithelial cells. As we have shown previously with SS, SSA inhibited the cGMP specific phosphodiesterase 5 (PDE5) enzyme. This resulted in accumulation of intracellular cGMP and activation of cGMP-dependent protein kinase (PKG) at concentrations comparable to those that induced breast tumor cell apoptosis. Mirroring the effects on PKG, SSA also resulted in decreased Wnt/β-catenin signaling, including decreased expression of the Tcf/Lef controlled proteins, cyclin D1 and survivin. Furthermore, SSA caused a 50% reduction in the incidence and a 30% reduction in the multiplicity of mammary tumors using the MNU model of mammary carcinogenesis. Interestingly, mammary tumors induced by MNU displayed high levels of PDE5 expression. These findings further demonstrate the COX-independent nature of the anticancer activity of certain NSAIDs, provide additional evidence that PDE5 may serve as an effective target for breast cancer chemoprevention, and reveal the utility of chemically modifying the NSAIDs to remove COX inhibitory activity while enhancing anticancer activity in order to produce safer and more effective chemopreventive agents. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 570. doi:1538-7445.AM2012-570