In this study, we used an orthotopic, highly immunogenic and metastatic murine breast carcinoma model (4T1) [30] in order to determine: i) whether LDH-A depletion and the resulting metabolic alterations would change the tumor microenvironment (TME); ii) whether LDH-A/lactate modification impacts on HIF-1 signaling and its downstream targets; and iii) how these alterations affect the anti-tumor immune response and the development of metastases in immunocompetent mice. The gene discussed is HIF1A; the disease is neoplasm.