Effect of Dichloroacetate on Lewis Lung Carcinoma Growth and Metastasis

Abstract

A hallmark of malignancy is excessive tumor glycolysis, even in the presence of oxygen, which causes lactacidosis in the tumor microenvironment and favors tumor cell proliferation and survival. For this reason antimetabolic agents which target tumor cell metabolism are being researched extensively as promising anticancer drugs. Aim: To study the effect of lactacidosis on survival of Lewis lung carcinoma (LLC) cells at the conditions of nutritional substrate deficiency in vitro and evaluate antitumor and antimetastatic activity against LLC/ R9 in vivo. Materials and Methods: LLC variant LLC/R9 was used as experimental tumor model. Tumor cell viability was determined using trypan blue staining. Apoptosis level was counted with the use of Hoechst 33258 dye. Lactate content in the tumor tissue was evaluated by enzyme method with the use of lactate dehydrogenase. Reactive oxygen species was determined using 2.7-dichlorofluorescein diacetate. Effects of dichloroacetate (DCA) on the growth and metastasis of LLC/R9 were analyzed by routine procedures. Evaluation of DCA effect toward electron-transport chain (ETC) components was performed using EPR. Results: It has been shown that at the conditions of lactacidosis and glucose deficiency, LLC/R9 cell viability in vitro was higher by 30% (р < 0.05) and apoptosis level was triply lower (р < 0.05) than these indices at the conditions of glucose deficiency only. In mice with transplanted LLC/R9 tumors treated for 3 weeks per os with DCA at the total dose of 1.5 g/kg of body weight starting from the next day after tumor transplantation, the primary tumor volume was just by 30% lower than that in control group. At the same time, the number and volume of lung metastases in animals treated with DCA were by 59% (р < 0.05) and 94% (р < 0.05) lower, respectively, than these indices in the control group. DCA treatment resulted in nearly 30% increase (р < 0.05) of lactate content in tumor tissue compared to that in the control, but did not affect significantly the levels of heme iron complexes with NO (at gmed = 2.007) in mitochondrial ETC proteins and Fe-S cluster proteins (at g = 1.94) in tumor cells. Conclusions: It has been shown that lactacidosis significantly promoted LLC/R9 cell survival at the conditions of glucose deficiency in vitro. If LLC/R9 developed in vivo, DCA as the compound with antilactacidosis activity did not suppress significantly the primary tumor growth but exerted significant antimetastatic activity.

The Importance of Gender-Related Anticancer Research on Mitochondrial Regulator Sodium Dichloroacetate in Preclinical Studies In Vivo

“…The accumulated lactate could be used by tumor cells as an energetic fuel and appear as the factor responsible for tumor resistance to treatment [192,206,207]. Sodium dichloroacetate suppresses lactate acidosis in the tumor microenvironment [173,208,209]. Hypoxia is a feature of solid tumors associated with resistance to therapy [210,211].…”

“…The DCA treatment was suggested to induce a stronger immune response to the tumor as an increase in the number of T lymphocytes in tumor tissue [190], which may be related to lactate level reduction in the tumor; a high lactic acid level has been shown to depress the T cell function [207]. Several studies have reported DCA anti-tumor effects to be related to the inhibition of angiogenesis, followed by the reduced tumor vascularity perfusion [171] and metastasis suppression [190,208].…”

Time-dependent cytotoxicity of dichloroacetate and metformin against Lewis lung carcinoma

“…Interestingly, despite the ability of DCA to stimulate the migration capacity of LLC/R9 cells, we previously demonstrated its high antimetastatic activity, which was manifested by a significant reduction in both the number of metastases and the volume of pulmonary metastases in mice transplanted with LLC/R9 [21]. This can be explained by the fact that in conditions of in vivo metastatic activity of a malignant tumor is determined not only by the migration capacity of tumor cells, but also by their ability to overcome all the numerous stages of the metastatic process.…”

“…The use of antioxidants helps cells to adapt and leads to an increase in the number of metastases, while inhibition such adaptation processes, on the contrary, reduces the amount of metastases. From these positions, the ability of DCA to enhance the production of reactive oxygen species by tumor cells [24,25] may be involved in its anti-metastatic effect in relation to LLC/R9 in vivo [21].…”

Dichloroacetate for Cancer Treatment: Some Facts and Many Doubts

“…Regarding lung carcinoid cells, DCA re-sensitized cells resistant to carboplatin [269]. In Lewis lung carcinoma DCA decreased slightly the proliferation of the primary tumor (30% less) and decreased markedly the number and volume of metastasis [270].…”