Simultaneous inhibition of PFKFB3 and GLS1 selectively kills KRAS-transformed pancreatic cells.

Activating mutations of the oncogenic KRAS in pancreatic ductal adenocarcinoma (PDAC) are associated with an aberrant metabolic phenotype that may be therapeutically exploited. Increased glutamine utilization via glutaminase-1 (GLS1) is one such feature of the activated KRAS signaling that is essential to cell survival and proliferation; however, metabolic plasticity of PDAC cells allow them to adapt to GLS1 inhibition via various mechanisms including activation of glycolysis, suggesting a requirement for combinatorial anti-metabolic approaches to combat PDAC. We investigated whether targeting the glycolytic regulator 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3) in combination with GLS1 can selectively prevent the growth of KRAS-transformed cells. We show that KRAS-transformation of pancreatic duct cells robustly sensitizes them to the dual targeting of GLS1 and PFKFB3. We also report that this sensitivity is preserved in the PDAC cell line PANC-1 which harbors an activating KRAS mutation. We then demonstrate that GLS1 inhibition reduced fructose-2,6-bisphosphate levels, the product of PFKFB3, whereas PFKFB3 inhibition increased glutamine consumption, and these effects were augmented by the co-inhibition of GLS1 and PFKFB3, suggesting a reciprocal regulation between PFKFB3 and GLS1. In conclusion, this study identifies a novel mutant KRAS-induced metabolic vulnerability that may be targeted via combinatorial inhibition of GLS1 and PFKFB3 to suppress PDAC cell growth.

PFKFB2 regulates glycolysis and proliferation in pancreatic cancer cells.

Tumor cells increase glucose metabolism through glycolysis and pentose phosphate pathways to meet the bioenergetic and biosynthetic demands of rapid cell proliferation. The family of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatases (PFKFB1-4) are key regulators of glucose metabolism via their synthesis of fructose-2,6-bisphosphate (F2,6BP), a potent activator of glycolysis. Previous studies have reported the co-expression of PFKFB isozymes, as well as the mRNA splice variants of particular PFKFB isozymes, suggesting non-redundant functions. Majority of the evidence demonstrating a requirement for PFKFB activity in increased glycolysis and oncogenic properties in tumor cells comes from studies on PFKFB3 and PFKFB4 isozymes. In this study, we show that the PFKFB2 isozyme is expressed in tumor cell lines of various origin, overexpressed and localizes to the nucleus in pancreatic adenocarcinoma, relative to normal pancreatic tissue. We then demonstrate the differential intracellular localization of two PFKFB2 mRNA splice variants and that, when ectopically expressed, cytoplasmically localized mRNA splice variant causes a greater increase in F2,6BP which coincides with an increased glucose uptake, as compared with the mRNA splice variant localizing to the nucleus. We then show that PFKFB2 expression is required for steady-state F2,6BP levels, glycolytic activity, and proliferation of pancreatic adenocarcinoma cells. In conclusion, this study may provide a rationale for detailed investigation of PFKFB2's requirement for the glycolytic and oncogenic phenotype of pancreatic adenocarcinoma cells.

6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase-3 is required for transforming growth factor ß1-enhanced invasion of Panc1 cells in vitro.

Transforming growth factor ß1 (TGFß1) is a well-established inducer of the epithelial-mesenchymal transition (EMT) that is essential for the acquisition of malignant properties, such as invasion, in tumor cells. Although recent studies suggest that the EMT in tumor cells is associated with reprogramming of energy metabolism and TGFß1 has been shown to stimulate glycolysis in multiple primary cell lines, little is known about TGFß1's effect on glycolysis and glycolytic regulators in transformed cells. Given the known regulatory role of 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase-3 (PFKFB3) in glycolysis and association of glycolytic activity with malignant features such as invasion, we sought to investigate whether TGFß1 regulates PFKFB3 expression and if PFKFB3 is involved in the TGFß1-mediated increase in the invasive ability of the Panc1 cell cline-a well-established model of TGFß1-initiated EMT. Herein we demonstrate that TGFß1 induces PFKFB3 expression and stimulates glycolysis in Panc1 cells. We also show that siRNA silencing of PFKFB3 prevents the stimulation of glycolysis and in vitro invasive ability of Panc1 cells by TGFß1. Furthermore, PFKFB3 silencing suppresses the TGFß1-mediated induction of the Snail protein, suggesting that PFKFB3 is required for the regulation of Snail expression by TGFß1. Taken together, our study identifies PFKFB3 as a key TGFß1 effector protein that mediates TGFß1's effect on Snail expression, invasion, and glycolysis.