Iodoacetate and 3-bromopyruvate modulate cell signaling to decrease the pancreatic cancer cell survival

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Cancer cells’ dependence on glycolysis for their energy requirements was suggested by Warburg in the1920’s (the Warburg hypothesis). There has been renewed interest to derived novel experimental paradigms using this hypothesis. In this study, we investigated the functional relation between the glycolytic pathway and tumor cell survival and proliferation by determining the effects on pancreatic cancer cells (PANC-1) of two glycolytic enzyme inhibitors, iodoacetate (IAA), an inhibitor of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and 3-bromopyruvate (3BP), an inhibitor of hexokinase II (HKII). We hypothesized that IAA and 3BP inhibit the functional roles of GAPDH and HKII leading to decreased survival of pancreatic cancer cells. To test our hypothesis, we performed cell survival (MTT) assay on IAA- or 3BP-treated PANC-1cells and found that both inhibitors induced decreases in survival of PANC-1cells in a dose-related manner. However, IAA was approximately six times more potent than 3BP, the IC50 for IAA and 3BP being 3 and 17µM, respectively. To elucidate the putative mechanism of cell death induced by IAA and 3BP, we determined lactate dehydrogenase (LDH) release from treated cells into the medium which correlates with the extent of necrotic cell damage/death. Our results revealed treatment with both inhibitors induced increases in cellular necrosis. However, although IAA is more potent than 3BP in lowering survival of PANC-1 cells, when the cells were treated at their respective IC50 concentrations, IAA produced no increase in the LDH release while 3BP induced 35% increase in the LDH release as compared to that in untreated cells. To assess the putative signaling mechanism(s) mediating the effects of IAA and 3BP on PANC-1 cells, western blot analysis was performed. We found that 3BP treatment of the cells reduced the expression of K-ras and phosphorylation of AKT but not that of ERK-1, whereas IAA treatment neither affected the expression of K-ras nor the phosphorylation of ERK-1 and AKT. We conclude that there may be a cross-talk between signaling pathways and glycolysis in regulating pancreatic cancer cell survival and death. Thus, a combination of agents that inhibit both glycolytic and signaling mechanisms may provide a novel approach to target pancreatic cancer effectively.