Abstract 1852: Down-regulation of PRMT6 drives Warburg effect through ERK induced relocalization of PKM2 to promote tumorigenicity and sorafenib resistance in hepatocellular carcinoma

Abstract

Cancer cells have a high dependence of glycolysis for ATP production, especially under hypoxic environment. Metabolic reprogramming in cancer drives an increased glycolytic rate that supports maximal production of nutrients for tumorigenesis. Our group has recently identified the post-translational modification enzyme, protein arginine methyltransferase 6 (PRMT6) to be frequently down-regulated and to exhibit a tumour suppressive effect in maintenance of cancer stemness in hepatocellular carcinoma (HCC) (Chan LH et al. Cell Reports 2018). Our current study finds transcriptome and metabolome profiling of HCC cells with PRMT6 repressed to exhibit enrichment of genes and metabolites involved in glycolysis. In vitro , PRMT6 negatively regulates glycolysis, glucose uptake, lactate production and pyruvate kinase activity in HCC cell lines and patient-derived organoids. Our previous work found PRMT6 to interfere with RAS/RAF binding by directly binding to CRAF and methylating arginine100 residue. Supporting the importance of PRMT6-mediated CRAF methylation, we find overexpression of catalytic inactive PRMT6 to exhibit no effect on glycolysis. MEK/ERK, known downstream effectors of RAS/RAF signalling, has been shown to induce nuclear PKM2 localization. Consistently, we find modulation of PRMT6 to negatively regulate ERK and PKM2 expression and localization. Rescue experiments involving the ERK inhibitor U0126 and shPKM2 further substantiate the importance of ERK/PKM2-mediated glucose metabolic reprogramming in HCC cells with PRMT6 suppressed. Functionally, inhibition of glycolysis by 2-deoxyglucose sensitized PRMT6 knockdown cells to sorafenib treatment in vitro and attenuated tumor growth in vivo . In addition, we also find PRMT6 expression to be regulated via hypoxia by binding of RE1-silencing transcription factor to the promoter region. Rescue experiments by re-expressing PRMT6 under hypoxic conditions further support the involvement of PRMT6 in driving glycolysis in oxygen deprived environments. Our work uncovers a critical function for PRMT6 in driving Warburg effect through regulating expression and localization of PKM2 via post-translational modification of CRAF, thereby promoting HCC initiation and sorafenib resistance. Citation Format: Tin-Lok Wong, Lok-Hei Chan, Stephanie Ma. Down-regulation of PRMT6 drives Warburg effect through ERK induced relocalization of PKM2 to promote tumorigenicity and sorafenib resistance in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1852.