Inhibition of energy-producing pathways of HepG2 cells by 3-bromopyruvate1

Abstract

3-BrPA (3-bromopyruvate) is an alkylating agent with anti-tumoral activity on hepatocellular carcinoma. This compound inhibits cellular ATP production owing to its action on glycolysis and oxidative phosphorylation; however, the specific metabolic steps and mechanisms of 3-BrPA action in human hepatocellular carcinomas, particularly its effects on mitochondrial energetics, are poorly understood. In the present study it was found that incubation of HepG2 cells with a low concentration of 3-BrPA for a short period (150 microM for 30 min) significantly affected both glycolysis and mitochondrial respiratory functions. The activity of mitochondrial hexokinase was not inhibited by 150 microM 3-BrPA, but this concentration caused more than 70% inhibition of GAPDH (glyceraldehyde-3-phosphate dehydrogenase) and 3-phosphoglycerate kinase activities. Additionally, 3-BrPA treatment significantly impaired lactate production by HepG2 cells, even when glucose was withdrawn from the incubation medium. Oxygen consumption of HepG2 cells supported by either pyruvate/malate or succinate was inhibited when cells were pre-incubated with 3-BrPA in glucose-free medium. On the other hand, when cells were pre-incubated in glucose-supplemented medium, oxygen consumption was affected only when succinate was used as the oxidizable substrate. An increase in oligomycin-independent respiration was observed in HepG2 cells treated with 3-BrPA only when incubated in glucose-supplemented medium, indicating that 3-BrPA induces mitochondrial proton leakage as well as blocking the electron transport system. The activity of succinate dehydrogenase was inhibited by 70% by 3-BrPA treatment. These results suggest that the combined action of 3-BrPA on succinate dehydrogenase and on glycolysis, inhibiting steps downstream of the phosphorylation of glucose, play an important role in HepG2 cell death.

Targeting cancer metabolism: a therapeutic window opens

“…HK is also a target of 3--bromopyruvate, a compound shown to be toxic to cancer cells 91,95 . However, 3--bromopyruvate is also toxic to some cancer cells at concentrations that are too low to inhibit HK and it has been argued that the combined inhibition of multiple metabolic enzymes accounts for the toxic effects of this compound on cancer cells 96 .…”

Metabolic interplay between glycolysis and mitochondrial oxidation: The reverse Warburg effect and its therapeutic implication

“…Therefore, therapeutic strategies should focus on both targets, glycolysis and mitochondrial OXPHOS. Even though some studies reported that mitochondrial OXPHOS is also one of 3-BP targets [185] , 3-BP has been mainly demonstrated to be the most potent glycolytic inhibitor among various types of inhibitors. However, including our studies, the results of in vivo studies that have used human HCC cell lines did not exhibit complete remission, but showed only partial remission after 3-BP treatment [18,19, .…”

Glutamine Deprivation Enhances Antitumor Activity of 3-Bromopyruvate through the Stabilization of Monocarboxylate Transporter-1

“…3-Bromopyruvate (3-BrPA) is a halogenated and alkylating analog of pyruvic acid able to curb the growth of many tumors, frequently refractory to standard therapeutics, by compromising ATP synthesis through the inhibition of glycolysis and mitochondrial complex II activity (12)(13)(14)(15)(16). In accordance with current challenges aimed at identifying metabolic conditions chemopotentiating the effectiveness of antitumor drugs, our study argues for the ability of glutamine deprivation to sensitize carcinoma cells to the cytotoxic effects of 3-BrPA both in vitro and in vivo.…”