High aerobic glycolysis of rat hepatoma cells in culture: Role of mitochondrial hexokinase

Abstract

A tumorigenic anchorage-dependent cell line (H-91) was established in culture from an azo-dye-induced rat ascites hepatoma. When grown in a glucose-containing medium the cells exhibit high rates of lactic acid production characteristic of rapidly growing tumor cells. However, when glucose is replaced with galactose the cells grow equally well but exhibit only moderately elevated rates of lactic acid production. The molecular basis for this observation cannot be attributed to differences in permeability because initial rates of glucose and galactose entry into hepatoma cells are identical. Rather, the activity of hexokinase (ATP:Dhexose 6-phosphotransferase, EC 2.7.1.1) is found to be high in hepatoma cells, about 20-fold higher than that of control and regenerating rat liver. Moreover, tumor hexokinase activity is not inhibited by low concentrations (<0.6 mM) of the reaction product glucose 6-phosphate. Additionally, 50% of the hexokinase activity of hepatoma cells is found associated with the mitochondrial fraction. This fraction is 3fold enriched in hexokinase activity relative to the homogenate and 4-fold enriched relative to the nuclear and postmitochondrial fractions. Tumor mitochondrial hexokinase appears to be coupled directly to oxidative phosphorylation, because addition of glucose to respiring hepatoma mitochondria (after a burst of ATP synthesis) resu ts in stimulation of respiration. In contrast, glucose has no effect on the respiration of mitochondria from control and regenerating liver. These results suggest that the high glycolytic capacity of HI9 hepatoma cells is due, at least in part, to an elevated form of hexokinase concentrated in the mitochondrial fraction of the cell.The most characteristic biochemical phenotype of cancer cells is their propensity for high aerobic rates of glycolysis (1-4). Rapidly growing tumor cells, in particular those growing in ascitic form, are known to exhibit markedly elevated rates of lactic acid production when compared with normal cells (1-4). Cells from slowly growing tumors also have elevated rates of aerobic glycolysis (4), although the elevation is not nearly as dramatic.The reason for the high aerobic lactic acid production of rapidly growing cancer cells has puzzled biochemists for more than 50 years, and as of this date a satisfactory explanation acceptable to most workers in the field of cancer research has not been forthcoming. Possible explanations for the very "high glycolysis" of rapidly growing cancer cells usually involve mitochondria, which are assumed to be either defective in some capacity or less effective than glycolytic enzymes in competing for common intermediates (2, 5).To more definitely establish the relationship(s) between mitochondria and glycolysis in rapidly growing cancer cells, the studies described in this paper have focused on differences in the catabolism of glucose and galactose by a hepatoma cell line growing in culture. Because such cancer cells grow equally well on both carbohydrate sources but produce large amounts o...

Hexokinase isozyme distribution and regulatory properties in lymphoid cells

“…However, there are only a few reports available on changes of regulatory properties of particular enzymes of glycolysis in cancer cells. Bustamante and Pedersen [3] found a decreased inhibition of hexokinase by glucose-6-phosphate in rat hepatoma cells. Kahn et al [4] described a glucose-6-phosphate dehydrogenase altered by some modifying factor.…”

“…For brain, liver and uterus tissue, hexokinase II has been reported to be a tumor marker [6--8,22], the presence of which was even described to correlate with malignancy for brain tumors [6]. Most of the other reports on hexokinase isozymes and cancer deal with hepatomas [3,10,22].…”

Inhibitory effect of quercetin on OVCA 433 cells and presence of type II oestrogen binding sites in primary ovarian tumours and cultured cells

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A translational study “case report” on the small molecule “energy blocker” 3-bromopyruvate (3BP) as a potent anticancer agent: from bench side to bedside

“…Significantly, much earlier work from the corresponding author's laboratory (Bustamante and Pedersen 1977) reported that the "Warburg Effect" common to most cancers is due in large part to their overexpression of hexokinase 2 (HK2) that binds to the outer mitochondrial membrane. This likely helped lead in part to the most common imaging technique used today to detect cancer throughout the world, i.e., positron emission tomography (PET).…”