BCAT1 promotes proliferation of endometrial cancer cells through reprogrammed BCAA metabolism

Branched-chain amino acid aminotransferase 1 (BCAT1) enzyme is an aminotransferase of glutamate and branched-chain amino acids (BCAAs), which is required for survival of various cancers. However, the role of BCAT1 in human endometrial cancer (EC) remains unknown. We analyzed the expression of BCAT1 in endometrial lesions using IHC. After BCAT1 gene knockdown and activity inhibition, cell proliferation, apoptosis, and metabolism were detected using CCK-8 assay, flow cytometry, and LC-MS/MS analysis. We analyzed molecular signature characteristics to understand how BCAT1 promotes cell proliferation. In this study, we demonstrated a significant increase in BCAT1 expression from normal endometrium to atypical endometrial hyperplasia (AEH) and then to EC, and the expression of BCAT1 in EC samples was related to tumor grade, FIGO stage and lymph node metastasis. Next, cell proliferation was markedly inhibited by lentiviral BCAT1 knockdown or Gbp treatment, but this had little effect on apoptosis rate. Further, BCAT1 knockdown resulted in 31.2% and 33.3% decreases in the amount of intracellular isoleucine and leucine produced, respectively, relative to a control. BCAT1 knockdown or activity inhibition resulted in a decrease of pS6K, a downstream target kinase of mTORC1. In conclusion, our study showed that BCAT1 is essential for EC progression and to increase EC cell proliferation through the production of BCAAs to activate the mTORC1 pathway, providing ideas for clinicians to identify metabolism-based targeted approaches for patients with EC.