3-Bromopyruvate Inhibits the Growth and Glucose Metabolism of TNBC Xenografts in Nude Mice by Targeting c-Myc

Background: Due to the lack of effective drug treatment, triple-negative breast cancer (TNBC) is prone to recurrence and metastasis after an operation. As a glycolytic inhibitor, 3-bromopyruvic acid (3-BrPA) can inhibit the proliferation and induce apoptosis of TNBC cells. However, whether it has similar effects in animal models remains unclear. Objective: To observe the effect of 3-BrPA on the growth and glucose metabolism of human TNBC transplanted tumors in nude mice and to investigate the mechanism. Methods: We constructed subcutaneous xenografts of human TNBC in nude mice and treated them with low, medium and high concentrations of 3-BrPA. After 15 days, nude mice were sacrificed to detect hexokinase (HK) activity and adenosine triphosphate (ATP) content in tumor tissues. Hematoxylin-eosin (HE) staining was used to detect the damage of transplanted tumors and liver and kidney in nude mice, which 3-BrPA caused. The expression of c-Myc in tumor tissues was detected by Immunohistochemistry (IHC). Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining was used to detect the apoptosis of tumor tissues. Besides, the expressions of Cytc, Bax, Bcl-2 and Caspase-9 were detected by Western blotting. Results: Compared with the control group, intraperitoneal injection of 3-BrPA inhibited the growth of human TNBC transplant tumors, decreased HK activity and ATP production in tumor tissues, disrupted the tissue structure of transplant tumors, and did not significantly damage liver and kidney tissues. IHC staining and Western blotting showed that 3-BrPA could decrease the expression of c-Myc and Bcl-2, increase the expression of Cyt -c, Bax and Caspase-9 expression and promote apoptosis in tumor tissues. Conclusion: The above data indicate that 3-BrPA inhibits the growth of human TNBC transplanted tumors and promotes their apoptosis. Its anti-cancer mechanism might reduce HK activity by down-regulating c-Myc expression, eventually leading to decreased glycolytic pathway energy production and promoting apoptosis of transplanted tumors.