LAUSR

Tumor cell metabolism is a hallmark of chemoresistance and its role has been well-defined in BRAF inhibitor resistance in melanoma. Melanoma cells are highly proliferative and are shown to develop addiction towards the metabolic pathways like glycolysis and mitochondrial respiration to meet energy demands. Melanoma cells predominantly utilize cytosolic aerobic glycolysis or Warburg effect to develop resistance towards BRAF inhibitors (vemurafenib and dabrafenib). Our observations indicated that vemurafenib resistant cells possessed 1.5 fold higher extra-cellular acidification rate (ECAR), an indicator of glycolysis when compared to sensitive cells. We also observed that STAT3, a known regulator of glycolysis was up-regulated in A375 and SKMEL28 BRAF inhibitor resistant cells when compared to the parental cell line. In addition, LDH-A, a key glycolytic enzyme was significantly overexpressed in A375 vemurafenib resistant cells when compared to its parental counterpart. Consequently, we observed that vemurafenib and dabrafenib treatment induces the expression of STAT3 in A375 and SKMEL-28 melanoma cells. Our results showed that piperlongumine inhibits the survival of A375 vemurafenib resistant (A375VR) melanoma cells. Our observations indicated that the combination of piperlongumine with vemurafenib and dabrafenib shows synergistic effects by suppressing 75% - 85% of cell survival when compared to vemurafenib/dabrafenib and piperlongumine (25% - 45%) treatment alone in A375 and SKMEL-28 BRAF inhibitor resistant melanoma cells. Moreover, the combination of piperlongumine with vemurafenib or dabrafenib induced 2-8 fold apoptosis when compared to vemurafenib/dabrafenib and piperlongumine treatment alone in A375 and SKMEL-28 BRAF inhibitor resistant melanoma cells. Piperlongumine treatment reduced the ECAR (glycolysis) in a concentration dependent manner after 12h of treatment in A375VR cells and suppressed nearly 50% of ECAR parameters glycolysis and glycolytic capacity. Treatment of A375VR cells with piperlongumine for 48h inhibited the expression of LDH-A and its upstream regulators pSTAT3 (Y705), β-catenin, c-Myc and HIF-1α as evaluated by western blot. In addition, oral administration of piperlongumine and vemurafenib combination suppressed 86% of tumor growth when compared to vemurafenib treatment. Taken together, our study thus indicate that piperlongumine potentiates the effects of BRAF inhibitors by inhibiting Warburg effect and its upstream regulators. [Supported in part by R01 grant CA129038, awarded to (S.K.S) by the National Cancer Institute. Citation Format: Sharavan Ramachandran, Neel Fofaria, Sanjay Srivastava. Piperlongumine, a novel treatment option to overcome BRAF inhibitor resistance in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3518.