Lactate-induced lactylation circularly regulates glucose metabolism enzymes in breast cancer.

e13092 Background: Breast cancer is the most common malignant tumor in the female population worldwide and has become the disease with the highest cancer-related mortality. Among the molecular subtypes of breast cancer, triple-negative breast cancer accounts for only 15% of primary malignancies, but due to its increasing recurrence, metastasis, and mortality, we need to find new therapeutic targets to address this phenomenon. Analysis from the field of metabolism found that the level of glycolysis in triple-negative breast cancer was significantly higher than that in other cancers. Glycolysis is a common malignant phenotype of cancer, namely the famous Warburg effect. LDHA is the last metabolic enzyme in the glycolytic pathway, and its expression is increased in triple-negative breast cancer. Lactate is the final product of glycolysis, which converts pyruvate to lactate and NADH to NAD+ under the catalysis of LDHA. The acidic tumor microenvironment formed by the accumulation of lactate will not only affect the progression of tumors and the therapeutic effect of anticancer drugs, but also inhibit the function of immune cells. Lactic acid groups can bind to histones and non-histone proteins to produce a new post-translational modification, lactylation. Methods: Breast cancer cells were infected with lentivirus vectors overexpressing or knocking down LDHA, and cell proliferation and cytotoxicity assay, transwell assay and Lactic Acid Content Assay were performed. To further explore the presence of lactylation of LDHA, immunoprecipitation experiments were performed and the modification sites were mutated to examine the enzymatic activity and function of LDHA. Results: In triple negative breast cancer with strong glycolytic metabolic phenotype, altering LDHA level can affect the biological function of breast cancer cells. Secondly, RNA-seq sequencing results showed that LDHA can affect the protein and transcription levels of MEST and CSTA. Finally, the lactylation of histones was also significantly changed after LDHA dysregulated. Reduced levels of LDHA were accompanied by reduced levels of MEST, CSTA, and histone lactylation. In addition, LDHA itself also has lactic acid modification, and mutations in the modification sites can change the enzymatic activity and function of LDHA. Conclusions: The regulatory axis of LDHA-lactate-lactylation has important value and function in the occurrence and development of breast cancer. LDHA regulates the function of some genes by lactate-induced lactylation of histones. In addition, the lactylation of LDHA can alter the enzyme activity, which may be a new therapeutic target for breast cancer.