Abstract 1180: Hexokinase II plays a pivotal role in colorectal cancer cell proliferation and survival

Abstract

Abstract The Warburg Effect describes the widely observed metabolic phenotype of cancer cells and their heavy reliance on the glycolytic pathway for energy production regardless of oxygen tension. This is a result of alterations to metabolic signaling pathways leading to an upregulation in key glycolytic enzymes. Hexokinase II (HKII) catalyzes the first irreversible step of glycolysis and is often overexpressed in tumors. 3-bromopyruvate (3BP) has been shown to primarily target HKII, and is a promising anti-cancer compound capable of targeting critical metabolic pathways in cancer cells. Here we examine the importance of HKII to cell proliferation and survival and also whether its inhibition could provide a therapeutic strategy in human colorectal cancer (CRC). Initially, established human CRC cell lines (HCT116, Caco2, SW480, DLD-1) were screened for HKII mRNA and protein expression. Cell proliferation and survival following HKII inhibition via both siRNA and 3BP treatment was determined using crystal violet staining, flow cytometry and western blotting. Sensitivity to 3BP was correlated with HKII expression amongst the cell lines screened. We next examined the pro-survival AKT signaling pathway via western blotting and found that AKT phosphorylation was dependent on 3BP dose and was residue-specific. Immunofluorescence was then used to examine subcellular HKII localization. Following 3BP treatment, mitochondrial localization of HKII was lost. As a result of tumor vascular abnormalities, regions within a tumor are exposed to transient and/or chronic ischemia, resulting in altered oxygen and nutrient availablity. To examine the effects of glucose availability on 3BP sensitivity, media glucose was gradually reduced in a step-wise manner and HKII expression, cell proliferation and cell survival were evaluated in CRC cell lines. Cells grown under reduced or normal glucose conditions were less sensitive to 3BP exposure than cells grown under high glucose conditions, and responses correlated with changes in HKII expression. Using immunostaining, we examined the expression of HKII in both normoxic and ischemic regions in FFPE samples of human CRC. These results were correlated to tumor stage and grade, along with patient outcome. Results from this study further define the role of HKII in colorectal cancer progression and show that 3-bromopyruvate could be useful as an anti-cancer therapy against CRC tumors with high expression of HKII. Citation Format: Nelson Ho, Brenda L. Coomber. Hexokinase II plays a pivotal role in colorectal cancer cell proliferation and survival. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1180. doi:10.1158/1538-7445.AM2015-1180