Metformin enhances antitumor action of sodium dichloroacetate against glioma C6

Abstract

Summary. It is known that the arsenal of chemotherapeutic agents for the treatment of malignant brain tumors is quite limited, which causes the high relevance of research aimed at finding new effective antitumor regimens, including the use of energy metabolism modifiers. Aim: To investigate the anti-glioma activity of sodium dichloroacetate (DCA) and metformin (MTF) used in combination in vitro and in vivo. Materials and Methods: Cell survival, cell cycle, apoptosis, mitochondrial membrane potential (Δψm), ATP level, the glucose consumption rate, and lactate production rate were determined in vitro in cultured glioma C6 cells. The antitumor action of agents in vivo was evaluated routinely by the prolongation of the life span of rats with transplanted intracerebral glioma C6 and was confirmed by histological examination of tumor tissue. Results: The half maximal inhibitory concentration (IC50) for DCA and MTF used separately was 79.2 ± 2.1 mM and 78.4 ± 4.0 mM, respectively, whereas IC50 for DCA used in combination with 7.8 mM MTF was 3.3 fold lower (24.0 ± 1.2 mM, p < 0.05). The 1-day incubation of cells with DCA at a concentration close to IC50 (25 mM), in combination with MTF at a concentration by order lower than IC50 (7.8 mM), in contrast to their separate use, resulted in a decrease in the number of viable cells by 40% (p < 0.05); redistribution of the cells by the cell cycle phases toward decreased proportion of cells in the S-phase by 46% (p < 0.05) and an increased percentage of cells in the G0/G1 phase by 24% (p < 0.05) compared to similar indices in the control. High proapoptotic activity of DCA in combination with MTF was supported by a significantly higher percentage of apoptotic cells in vitro than in the control (18.9 ± 4.4% vs 5.7 ± 1.3%, p < 0.05) and a high number of tumor cells with signs of apoptosis revealed during the histological examination of tumor pathomorphosis. The combined effect of DCA and MTF resulted in almost 4-fold decrease of the glucose consumption rate by glioma C6 cells (0.23 ± 0.05 μmol/106 cells/h vs 0.91 ± 0.12 μmol/106 cells/h, p < 0.05) compared to the corresponding parameters in the control, and 2-fold increased rate of lactate production (1.06 ± 0.03 μmol/106 cells/h vs 0.53 ± 0.03 μmol/106 cells/h, p < 0.05). At the same time, both Δψm and the level of intracellular ATP in the glioma C6 cells treated with DCA and MTF, both separately and in combination, did not differ significantly from those indices in the control. In in vivo studies, the average life span of rats with intracranial transplanted glioma C6, treated with DCA in combination with MTF in a total dose of 1.1 and 2.6 g/kg body weight, respectively, was 50% higher (p < 0.001) than in the control group. In contrast, in the case of single-use (at a dose of 2.6 g/kg), MTF increased the life span of tumor-bearing animals just by 19% (p < 0.01), whereas DCA alone (at a dose of 1.1 g/kg) did not significantly change the survival time of rats. Conclusions: The obtained data indicate synergism of anti-glioma action of DCA and MTF in a case of their combined use both in vitro and in vivo and may be considered a starting point for the development of effective treatment regimens for malignant brain tumors based on the combined use of DCA and MTF.

Metformin as Potential Therapy for High-Grade Glioma

“…The antitumor effect was mainly due to the effect on the induction of apoptosis and the cell cycle course of the samples tested. It is worth noting that achieving a therapeutic effect in the case of combined treatment was associated with the administration of smaller doses of the drugs, which is particularly important in light of the threatening side effects [173]. Similar results of simultaneous administration of both drugs were previously seen in observations on ovarian cancer cells [177].…”

“…In 2019, Kolesnik et al, conducted a study on the effect of including metformin in cancer therapy using sodium dichloroacetate (DCA). Observations were made on GBM cell lines in vitro and in vivo using a rat model [173]. DCA is a drug that has been mainly used in the treatment of metabolic disorders for many years, but recently its antitumor properties have been studied, also regarding gliomas [174][175][176].…”

Cancer cachexia has many symptoms but only one cause: anoxia

“…• DCA targets mainly cells that cannot use the oxidative metabolism 248 . This concept is further confirmed by the synergy between DCA and metformin [267][268][269][270][271][272][273][274] . The fundamentals of this association stem from the fact that metformin inhibits mitochondrial Complex I and reduces oxidative metabolism while DCA inhibits glycolysis.…”

Metformin and Risk of Malignant Brain Tumors in Patients with Type 2 Diabetes Mellitus

“…In recent years, the potential usefulness of metformin on the treatment of MBT has been investigated [18]. According to in vitro and in vivo studies, metformin may inhibit the growth of human glioblastoma cells and enhance therapeutic responses to chemotherapy (e.g., temozolomide) and radiotherapy [18][19][20]. Several clinical trials are being conducted to investigate its potential usefulness in the treatment of MBT but the outcomes remain unknown [17,21,22].…”