Regulation of PD-L1 expression and secretion by branched-chain amino acids in melanoma and prostate cancer cells

Cancer immunotherapy, particularly immune checkpoint blockade targeting programmed death ligand 1 (PD-L1), has revolutionized cancer treatment. Branched-chain amino acids (BCAAs) are essential amino acids whose metabolism can be an indicator of certain cancers. However, the relationship between branched-chain amino acids (BCAAs) and PD-L1 expression is largely unknown. Our study examines the relationship between BCAAs and PD-L1 expression and sheds light on potential avenues for refining cancer treatment strategies. We tested BCAA supplementation on two cell lines, melanoma and prostate cancer, and performed Western blot analysis of cells and exosomes. The research reveals that supplementation of BCAAs such as isoleucine and valine selectively promotes PD-L1 expression, particularly within extracellular vesicles (EVs). These findings suggest an important role for BCAAs in modulating immune checkpoint dynamics in cancer. Despite acknowledging limitations such as cell line specificity, the study proposes novel therapeutic avenues, including targeting PD-L1-associated EVs and considering BCAA supplementation as adjuvant therapy. The implications extend to the identification of EV-associated PD-L1 as a potential predictive biomarker for immunotherapy response, guiding personalized treatment strategies. Future research directions involve in vivo studies and a deeper exploration of the molecular mechanisms underlying BCAA-mediated effects, aiming to bridge the gap between in vitro observations and clinical applications in cancer treatment.