Background: Anticancer action of sodium dichloroacetate (DCA) could be related to its ability to activate oxidative phosphorylation leading to enhanced generation of reactive oxygen species and induction of apoptosis. On the other hand, activation of oxidative phosphorylation could promote tumor cell survival, in particular, via increased ATP synthesis. Such ambiguous effects of DCA could influence its anticancer effectiveness, depending on biological properties of a tumor, schedule of DCA administration and its dosage. The aim of the study was to analyze anticancer effect of DCA against glioma С6 in rats under conditions of different schedules of its administration and various dosages. Materials and Methods: The study was carried out in Wistar rats with intracerebrally transplanted glioma С6 cells. Therapy with DCA was performed as follows: daily for 6 days starting from the second day after tumor cell transplantation (schedule І) or 7th day (schedule ІІ) at a dose of 1.0 g/kg, or daily for 13 days starting from the second day at doses of 1.0; 1.5 or 4.5 g/kg (schedule ІІІ). An influence of hypoxia on anticancer effect of DCA was studied using hypoxic chambers where oxygen content was maintained at a level of 12.5–13% for 3 h after DCA administration to glioma С6 bearing rats. The state of mitochondrial electron transport chain components in tumor cells was studied using electron paramagnetic resonance. Results: It has been shown that therapy with DCA using schedule I resulted in 15% decrease of animals life span (LS; р < 0.05), while the use of schedule II had no effect on this index. Prolonged administration of DCA (schedule ІІІ) resulted in significant antitumor effect and increased LS of rats by 25.5% (p < 0.05). Under hypoxic conditions, treatment with DCA resulted in a significant increase of animal LS by 15–22%. Dosage of DCA had a moderate effect of its anticancer action. Maximal effect, an increase of LS by 34.5% (p < 0.05) was detected at a dose of 1.5 g/kg. It has been shown that anticancer activity of DCA under all studied conditions is not related to its influence on a functional state of tumor cell mitochondria. Conclusion: Anticancer effect of DCA significantly depends on a schedule of its administration; being administered at equal total dose, but dependent on the schedule DCA could cause ambiguous effects varying from tumor growth stimulation to significant anticancer activity. Under hypoxic conditions, anticancer efficacy of DCA against glioma С6 is significantly enhanced.

Aerobic glycolysis that supports high proliferation rate and survival of tumor cells in unfavorable conditions is among fundamental features of tumor metabolism. The search for active modulators of energetic metabolism capable of suppressing tumor growth and metastasis could result in higher effectiveness of anticancer therapy. Aim: To study antitumor and antimetastatic activity of the modulators of energetic metabolism dichloroacetate (DCA) and 2-deoxy-D-glucose (2DG) used in combination treatment of Lewis lung carcinoma (LLC). Materials and Methods: As experimental tumor model, LLC/R9 variant was used. DCA and 2DG were administered per os to С57Bl/6 mice 5 times per week for 3 weeks at a total dose of 1.5 and 0.98 g/kg, respectively, as single agents or in combination starting from the following day after tumor cell transplantation. Growth of primary tumor and number and volume of lung metastases were registered. Lactate and pyruvate content was determined by enzymatic methods using lactate dehydrogenase. Electron paramagnetic resonance was used for analyzing the functional state of the components of mitochondrial respiratory chain. Engulfing activity and reactive oxygen species (ROS) production in tumor-associated CD14+ cells was analyzed by flow cytometer with the use of FITC-labeled staphylococcus, and by spectrofluorometry with the use of 2.7-dichlorofluorescein diacetate, respectively. Results: DCA administered as a single agent did not affect primary tumor growth but decreased the number and volume of lung metastases by 60% (p < 0.05) and 90% (p < 0.05), respectively. In mice treated with 2DG only, primary tumor volume as well as the number and volume of lung metastases were not affected. Combination treatment with DCA and 2DG resulted in the decrease of primary tumor volume, the number and volumes of lung metastases by 70; 46, and 90%, respectively (р < 0.05). High antitumor activity of DCA + 2DG was associated with 31% decrease (p < 0.05) of lactate content in tumor tissue and 120% increase (p < 0.01) of ROS production in СD14+ cells recruited to the region of tumor growth. Conclusion: 2DG that possesses neither antitumor nor antimetastatic activity against LLC/R9 significantly enhanced antitumor activity of DCA with accompanying inhibition of glycolysis and increase of cytotoxic activity of CD14+ cells infiltrating tumor tissue. Taking into account significant antimetastatic activity of DCA this substance could be considered as a promising antimetastatic agent.

It is known that metformin is a hypoglycemic drug used to treat type II diabetes mellitus. Recently active studies of its antitumor activity in relation to different types of malignant cells are conducted. Aim: To determine the relationship between cytotoxic activity of metformin in vitro and its antitumor activity in vivo. Materials and Methods: The rat C6 glioma cell line and mouse Lewis lung carcinoma cells (LLC) were used in this work. The number of living cells in the cytotoxic test was evaluated using sulforhodamine B. Parameters of tumor cell susceptibility to metformin activity in vitro were calculated using nonlinear and linear regression of experimental data. The antitumor action of metformin in vivo was evaluated routinely by the extension of survival time (ST) (in rats with intracerebral C6 glioma) and its effect on the volume of the primary tumor, the number and volume of metastases (in mice with LLC). Results: In cultured LLC cells in vitro, the proportions of metformin-resistant (A1, %) and metformin-sensitive (A2, %) subpopulations were 10.0 ± 2.2% and 92.0 ± 3.5%, respectively, in terms of the total number of living cells. Parameter t, which characterizes the sensitivity of cancer cells to metformin action (the lower is the value of this parameter the higher is sensitivity of cells to metformin cytotoxicity), for metformin-resistant and metformin-sensitive subpopulations was: t1(mM) = ∞ and t2(mM) = 2.9 ± 0.3, correspondingly. For metformin-sensitive subpopulation of LLC cells IC50 (mM) = 2.42 ± 0.34. The volume of the primary tumor, the amount and volume of metastases in mice receiving metformin at a dose of Dmin (0.15 g/kg) and Dmax (0.3 g/kg) values did not significantly differ from those in the control. However, in the case of Dmin, there was a tendency to increased volume of the primary tumor, in the case of Dmax, there was a tendency to increased volume of metastases. The analogical parameters (A1, A2, b1, b2, IC50 (1), IC50 (2)) characterizing cell sensitivity to the action of metformin in vitro were obtained in relation to C6 glioma cells. In metformin-resistant subpopulation, these parameters were: A1 (%) = 72.3 ± 1.4; b1 (%/mM) = 0.43 ± 0.005; IC50 (1) (mM) = 84.1 ± 2.4. For metformin-sensitive subpopulation, these parameters were: A2 (%) = 30.8 ± 2.3; b2 (%/mM) = 2.87 ± 0.4; IC50 (2) (mM) = 5.37 ± 0.45. In vivo, a statistically significant anti-glioma effect of metformin was observed: at a dose of Dmax (5.2 g/kg) administration of this preparation resulted in a prolongation of the mean ST of tumor-bearing rats by 23% (p < 0.05) compared with that in the control. Conclusions: We found no correlation between the cytotoxic/cytostatic action of metformin in vitro and its antitumor activity in vivo on the two types of tumor cells; these results indicate a significant contribution of the tumor microenvironment to the implementation of the antitumor activity of the drug.

Significant variability of anticancer efficacy of dichloroacetate (DCA) stimulated an active search for the agents capable to enhance it antitumor action. Therefore, the aim of this work is the study of capability of aconitine-containing antiangiogenic agent BC1 to enhance anticancer activity of DCA against Ehrlich carcinoma. Materials and Methods: DCA (total dose was 1.3 g/kg of b.w.) and BC1 (total dose was 0.9 mg/kg of b.w.) were administered per os starting from the 2nd and 3rd days, respectively (8 admini strations for each agent). Antitumor efficacy of agents was estimated. Lactate level, LDH activity and the state of mitochondrial electron transport chain in tumor cells as well as phagocytic activity and reactive oxygen species (ROS) production of tumor-associated macrophages (TAM) were studied. Results: Combined administration of DCA and ВС1 resulted in 89.8% tumor growth inhibition (p < 0.001), what is by 22.5% (p < 0.05) higher that that of DCA alone. This combined treatment was accompanied with a decrease of lactate level in tumor tissue by 30% (p < 0.05) and significant elevation of LDH activity by 70% (p < 0.01). Increased level of NO-Fe-S clusters and 2-fold reduction of Fe-S cluster content were revealed in tumor tissue of mice after DCA and BC1 administration. It was shown that combined therapy did not effect TAM quantity and their phagocytic activity but stimulated ROS production by TAMs by 78% (p < 0.05) compared to this index in control animals. Conclusion: Antiangiogenic agent ВС1 in combination with DCA considerably enhances antitumor activity of DCA via significant decrease of Fe-S-containing protein level resulted from substantial elevation of nitrosylation of these proteins.