Abstract 2270: TRAIL-TZD combinatorial treatment induces apoptosis in prostate cancer cells through modulation of AMPK signaling pathway

Prostate cancer is the second most frequently diagnosed cancer of men and the fifth most common cancer overall. Treatment options for localized disease include surgery, radiation therapy, and hormonal therapy, but they are not effective in the advanced stages of the disease. Most of the anticancer drugs in current use primarily act by inducing apoptosis in target cells. So, the identification of novel targets for drug-induced apoptosis will be useful for treating resistant forms. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer therapy that preferentially induces apoptosis in cancer cells. However, many neoplasms are resistant to TRAIL by mechanisms that are poorly understood. Our previous studies indicated that combinatorial treatment with Troglitazone (TZD), a synthetic ligand for peroxisome proliferator-activator receptor gamma and TRAIL can induce significant apoptosis in TRAIL-resistant cancer cells. In this study we determined AMP-activated protein kinase (AMPK) as a potential target for TRAIL-TZD-induced apoptosis in prostate cancer cells. AMPK is a family of serine/threonine protein kinase and is highly conserved from yeast to human. It consists of three subunits: a catalytic α subunit and regulatory β and γ subunits. AMPK is a well-accepted target for the treatment of metabolic syndrome and Type 2 diabetes. We used C42-DN (stably overexpressing AMPK α1-dominant negative) and C42-EV (empty vector) prostate cancer cell lines to study differences in TRAIL-TZD-induced apoptosis. Our studies showed a dose dependent increase in TRAIL-induced apoptosis with increasing concentrations of TZD (upto 100μM), which was significantly higher in C42-EV cells compared with C42-DN cells. The peak of apoptosis was around 4h following treatment. Similarly, using MTT assay, we observed a dramatic reduction in cell viability in the C42-EV compared to C42-DN cells when treated with same concentrations of TRAIL-TZD, thus suggesting that C42-DN cells were more resistant to this treatment. In addition, time course studies with C42-EV cells showed an increase in pAMPK T172 levels (indicating AMPK activation) and pACC S79 (downstream target of AMPK) levels coinciding with the time of apoptosis. Small interference RNA (siRNA)-mediated knockdown of endogenous AMPK α1 expression showed a reduction of apoptosis in DU145 and LNCaP cells. Studies are currently underway to determine whether knocking down both AMPK α1 and α2 produces a more complete inhibition of apoptosis. These studies suggest that apoptosis induction by TRAIL-TZD combination is mediated via AMPK in prostate cancer cells. Citation Format: Sreevidya Santha, Sunipa Majumdar, Navin Viswakarma, Ajay Rana, Basabi Rana. TRAIL-TZD combinatorial treatment induces apoptosis in prostate cancer cells through modulation of AMPK signaling pathway. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2270. doi:10.1158/1538-7445.AM2014-2270