Targeting prostate cancer cell metabolism: impact of hexokinase and CPT-1 enzymes

Abstract

Glycolysis has been shown to be required for the cell growth and proliferation in several cancer cells. However, prostate cancer cells were accused of using more fatty acid than glucose to meet their bioenergetic demands. The present study was designed to evaluate the involvement of hexokinase and CPT-1 in the cell growth and proliferation of human prostate cancer cell lines, PC3, and LNCaP-FGC-10. Hexokinase and CPT-1 activities were examined in the presence of different concentrations of their inhibitors, lonidamine and etomoxir, to find the concentration of maximum inhibition ([I max]). To assess cell viability and proliferation, dimethylthiazol (MTT) assay was carried out using [I max] for 24, 48, and 72 h on PC3 and LNCaP cells. Apoptosis was determined using annexin-V, caspase-3 activity assay, Hoechst 33258 staining, and evaluation of mitochondrial membrane potential (MMP). Moreover, ATP levels were measured following lonidamine and etomoxir exposure. In addition, to define the impact of exogenous fatty acid on the cell growth and proliferation, CPT-1 activity was evaluated in the presence of palmitate (50 μM). Hexokinase and CPT-1 activities were significantly inhibited by lonidamine [600 μM] and etomoxir [100 μM] in both cell lines. Treatment of the cells with lonidamine [600 μM] resulted in a significant ATP reduction, cell viability and apoptosis, caspase-3 activity elevation, MMP reduction, and appearance of apoptosis-related morphological changes in the cells. In contrast, etomoxir [100 μM] just decreased ATP levels in both cell lines without significant cell death and apoptosis. Compared with glucose (2 g/L), palmitate intensified CPT-1 activity in both cell lines, especially in LNCaP cells. In addition, activity of CPT-1 was higher in LNCaP than PC3 cells. Our results suggest that prostate cancer cells may metabolize glucose as a source of bioenergetic pathways. ATP could also be produced by long-chain fatty acid oxidation. In addition, these data might suggest that LNCaP is more compatible with palmitate.

The Metabolic Phenotype of Prostate Cancer

“…As noted above, benign prostate cells evade oxidative phosphorylation at baseline. It has been shown that early prostate cancers rely on lipids and other energetic molecules for energy production and not on aerobic respiration (16, 17). Therefore, the Warburg effect does not hold consistent in the pathogenesis of prostate cancer, as these cells do not have the increased glucose uptake (18).…”

Mechanism of antineoplastic activity of lonidamine

“…The data of Guo et al (52) suggest substantial decreases in flux through the PPP and glycolytic pathways, which may be consistent with inhibition of hexokinase II but does not prove it since inhibition of these pathways could result from other mechanisms such as acid inhibition of specific enzymes in the PPP and glycolytic pathways. Sadeghi et al (18) have reported the inhibition of hexokinase with 600 μM LND in prostate cancer cells using glucose 6-phosphate dehydrogenase (G6PD)-coupled assay. Cervantes-Madrid et al (17) have also suggested the inhibitory effects of LND on hexokinase based on genetic manipulation of hexokinase mRNA.…”

The dark side of glucose transporters in prostate cancer: Are they a new feature to characterize carcinomas?

“…34 HKII is also involved in the increase in glucose metabolism after androgen deprivation in PTEN/tumor protein p53-(TP53)-deficient PCa cells. 36 Moreover, pentose phosphate pathway (PPP) is promoted by an AR/mTOR-mediated mechanism, maintaining glucose-6-phosphate dehydrogenase levels higher during PCa progression. 36 Moreover, pentose phosphate pathway (PPP) is promoted by an AR/mTOR-mediated mechanism, maintaining glucose-6-phosphate dehydrogenase levels higher during PCa progression.…”