Cytotoxic activity of metformin in vitro does not correlate with its antitumor action in vivo

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

Effectiveness of sodium dichloroacetate against glioma с6 depends on administration schedule and dosage

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

Effect of enterosorption on paraneoplastic syndrome manifestations in mice with highly angiogenic variant of lewis lung carcinoma

Aim: To study the correcting effects of microgranulated HSGD enterosorbent on hematological, morphological and biochemical indices of paraneoplastic syndrome in mice with highly angiogenic variant of Lewis lung carcinoma LLC/R9. Methods: The study was performed on male С57/ВL6 mice with transplanted LLC/R9. Enterosorbent HSGD was administered daily at a dose of 0.625 g/kg for 2 weeks starting from 7th day after tumor cell transplantation. When enterosorption was completed, an analysis of peripheral blood, biochemical indices and morphological structure of tumor, lung, liver, spleen and thymus was carried out by standard methods. Results: It has been shown that administration of enterosorbent did not affect LLC/R9 growth but resulted in nearly two fold decrease of the volume of lung metastases (p < 0.05). Erythrocyte number and hemoglobin level were higher by 30.0% (p < 0.05) and 23.3% (p < 0.05), respectively, in mice treated with enterosorbents as compared to untreated animals. In addition sorbent treatment completely normalized the thrombocyte index resulting in elevation of platelet number by 54.5% (p < 0.01) up to their level in intact mice. The morphological examination of liver and biochemical analysis of peripheral blood evidenced on significant positive correcting effect of enterosorption on histological structure of this organ and its functional acti­vity. Normalization of total proteins and serum albumin level as well as significant decrease of total lipid concentration by 29% (p < 0.01) in blood of treated mice were observed. Conclusion: Positive influence of microgranulated carbon sorbent on some hematological, morphological and biochemical indices of tumor associated symptoms in LLC/R9-bearing mice denotes that enterosorption-based therapy can be considered as a prospective treatment for correction of some paraneoplastic syndrome signs in cancer patients. Key Words: paraneoplastic syndrome, Lewis lung carcinoma LLC/R9, enterosorption

CYTOTOXIC ACTIVITY OF METFORMIN IN VITRO DOES NOT CORRELATE WITH ITS ANTITUMOR ACTION IN VIVO

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

EFFECTIVENESS OF SODIUM DICHLOROACETATE AGAINST GLIOMA С6 DEPENDS ON ADMINISTRATION SCHEDULE AND DOSAGE

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