Abstract 5391: MUC1 and HIF-1α signaling interactions modulate glucose flux in pancreatic cancer.
Authors: Purohit Vinee , Chaika Nina V. , Gebregiworgis Teklab , Radhakrishnan Prakash , Zhang Bo , Mehla Kamiya , Yu Fang , Johnson Keith R. , Powers Robert , Hollingsworth Michael A. , Singh Pankaj K. 
Published: August 2014

Abstract
MUC1, a type-I transmembrane protein, is significantly overexpressed in pancreatic cancer. High expression of MUC1 in pancreatic cancer correlates with poor prognosis. Pancreatic tumors demonstrate significant hypoxia, which causes stabilization of HIF-1α, a key modulator of glycolytic gene expression. Recently, we observed that MUC1 occupies multiple HIF-1α–regulated glycolytic gene promoters. By performing in vitro and in vivo studies we observed that MUC1 overexpression causes up-regulation of glucose uptake, lactate release and expression of genes involved in glucose metabolism in pancreatic cancer cell lines. Based on these data we hypothesized that MUC1 regulates the stabilization/activity of HIF-1α to facilitate the glycolytic phenotype in pancreatic cancer. To investigate the regulation of HIF-1α by MUC1, we performed lentiviral shRNA-mediated knock down of HIF-1α in MUC1-overexpressing S2-013 and Capan1 pancreatic cancer cells and assayed for glucose uptake, lactate release and glycolytic gene expression. We observed that knocking down HIF-1α abrogated the MUC1-induced up-regulation of glucose metabolism. To investigate if MUC1 physically interacts with HIF-1α, we performed co-immunoprecipitation assays by utilizing a mAb against the cytoplasmic tail of MUC1. Our results indicated significant interaction between MUC1 and HIF-1α. Additionally, by performing chromatin immunoprecipitation we observed that MUC1 co-occupies the promoter regions of ENO1 and PGM2 glycolytic genes along with HIF-1α. MUC1 also increased HIF-1α activity by facilitating P300 recruitment and resultantly enhancing histone3 lysine9 acetylation on the MUC1-occupied promoters. By performing 1H-13C HSQC NMR experiments on the methanol extracts from MUC1-overexpressing or control S2-013 cells cultured with 13C-glucose, we observed an increased glycolytic flux and faster glucose turnover in pancreatic cancer cells. Furthermore, MUC1 overexpression caused a reduction in the levels of 2-oxoglutarate, a substrate for prolyl hydroxylases that regulate HIF stability. Thus, MUC1-mediated reduction in 2-oxoglutarate levels indirectly stabilizes HIF-1α by reducing the activity of prolyl hydroxylases. Overall, our results demonstrate that MUC1 serves as a novel metabolic regulator in pancreatic cancer that facilitates glycolytic flux by increasing HIF-1α stability and activity.
Citation Format: Vinee Purohit, Nina V. Chaika, Teklab Gebregiworgis, Prakash Radhakrishnan, Bo Zhang, Kamiya Mehla, Fang Yu, Keith R. Johnson, Robert Powers, Michael A. Hollingsworth, Pankaj K. Singh. MUC1 and HIF-1α signaling interactions modulate glucose flux in pancreatic cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5391. doi:10.1158/1538-7445.AM2013-5391