Results of sodium lactate and cyclophosphamide treatment in C57BL/6 mouse tumor model

Abstract

Background: In the tumor microenvironment, lactate, rather than glucose, serves as a source of energy for immune cells. Researchers at Southwestern Simmons Cancer Center have shown that lactate, a metabolic byproduct produced during vigorous exercise, enhances antitumor immune responses by increasing tumor-specific CD8+ T cells within the tumor microenvironment. The effects of lactate on T-regulatory cells are currently unknown, and there is interest in exploring the potential synergistic action with cyclophosphamide therapy, one of the main chemotherapeutic agents known to inhibit T-regulatory cells. This research is motivated by the absence of studies testing the combined effect of lactate and cyclophosphamide treatment in mouse tumor models. Aim: To investigate the combined effect of sodium lactate and cyclophosphamide treatment on a tumor model induced in C57BL/6 experimental mice. Materials and Methods: Experimental animals: Female C57BL/6 mice aged 6-8 weeks were utilized for the experiment. Cell culture: Mouse colon tumor cells (MC-38) were cultured in Dulbecco’s Modified Eagle Medium (DMEM) supplemented with 10% fetal calf serum and 0.5% antifungal and antibiotic mixture (Amphotericin B, Penicillin G, Streptomycin) under 5% CO2 at 37°C. Tumor model generation method: MS38 tumor cells were diluted with phosphate-buffered saline solution, and 1x106 cells in 100 μl were subcutaneously injected into the right abdomen of experimental animals to induce cancer. Methods of combined treatment with lactate and cyclophosphamide: On the 8th day after tumor cell injection, when the tumor volume reached 150 mm3, mice were divided into 5 groups and treatment was initiated. Tumor size measurement method: using an automatic caliper, the length and width of the tumor were measured three times daily. Results: The mean tumor volume in the lactate isotonic solution group was statistically significantly reduced compared to the glucose and PBS treatment groups (p<0.01). Additionally, the mean tumor volume in the combined lactate and cyclophosphamide treatment group was significantly reduced compared to either lactate or cyclophosphamide treatment alone (p<0.05). Therefore, combined treatment effectively inhibits tumor growth. All animals tested (n=20) were observed for 30 days post-treatment, with 65% mortality occurring within 20 days post-treatment. Mice treated with the combination of lactate and cyclophosphamide exhibited statistically significant (p<0.001) longer survival compared to both other treatment groups and the control group. Conclusion: Combined treatment effectively suppresses tumor growth and enhances the probability of survival in experimental animals. This synergistic effect is attributed to the antitumor properties of lactate, which promotes lymphocyte activation within the tumor microenvironment, coupled with the inhibitory action of cyclophosphamide on T regulatory cells.