Abstract 3322: Elucidation of the signaling pathways that mediate berberine-induced effects in cancer cells

Abstract

Abstract Resistance towards standard therapeutic regimens and evasion of apoptosis are some of the hallmarks of advanced forms of cancer, which include Sorafenib-resistance in hepatocellular carcinoma (HCC), castration-resistance in prostate cancer. Development of effective therapeutic strategies that can target these resistant forms is critically needed. In an effort to understand the molecular mechanism mediating resistance in cancer, in previous studies utilizing Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-resistant cancer cells we showed that combination of TRAIL along with the PPARγ ligand Troglitazone (TZD) can sensitize them towards apoptosis. Using more molecular approaches these studies identified the serine/threonine protein kinase, AMP-activated protein kinase (AMPK) as a mediator of TRAIL-TZD-induced apoptosis. Since AMPK seemed to be a major mediator of this apoptosis, in the current studies we utilized the natural compound Berberine (BBR), a known activator of AMPK in combination with TRAIL. These demonstrated a significant reduction of cell viability (MTT assay) and induction of apoptosis (caspase activation) when treated with a combination of TRAIL and BBR. This apoptosis is attenuated in cells overexpressing AMPKα-dominant negative (DN), suggesting an involvement of AMPK in mediating this. To understand the downstream targets and the mechanism involved, an apoptosis PCR array analysis was performed, which suggested induction of TNFRSF10B (DR5) gene expression by BBR. In addition, knockdown of DR5 expression attenuated TRAIL-BBR-induced apoptosis, suggesting DR5 to be a potential target of BBR in this apoptotic cascade. Future studies will include determining any crosstalk of AMPK in BBR signaling to modulate DR5 pathway. Our earlier studies also demonstrated an involvement of β-catenin in mediating cancer cell resistance. Stabilizing mutations and overexpression of β-catenin has been reported in many cancers, most profoundly in HCC leading to an activation of Wnt/β-catenin signaling. To understand any role of β-catenin in TRAIL-BBR-induced apoptosis, we determined the effect of BBR on β-catenin pathway. These revealed a significant attenuation of β-catenin protein expression by BBR in various HCC cells in a time and dose-dependent manner. BBR treatment also attenuated β-catenin/TCF-induced transcriptional activity, indicating antagonism of β-catenin pathway. Our studies indicate that combination of TRAIL and AMPK activator BBR might be an effective means of antagonizing β-catenin pathway and ameliorating TRAIL resistance via DR5 in advanced forms of cancer. Citation Format: Basabi Rana, Rong Ke, Kanchan Vishnoi, Navin Viswakarma, Subhasis Das, Ajay Rana. Elucidation of the signaling pathways that mediate berberine-induced effects in cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3322. doi:10.1158/1538-7445.AM2017-3322