Analysis of Naturally Processed Human Histocompatibility Leukocyte Antigen Class I‐Bound Peptides from Hepatocellular Carcinoma Tissues in vivo

Naturally processed self‐peptides bound to human histocompatibility leukocyte antigens (HLA) class I molecules of human hepatocellular carcinoma tissues (HLA‐A2.1, ‐B44, ‐B13) in vivo were isolated for sequence analysis. Acid‐eluted peptides were subjected to reversed‐phase high‐performance liquid chromatographic separation and single‐fraction sequencing was performed by Edman degradation. The peptides were found to be octamers or nonamers and they were derived from the processing of intracellular proteins. Three independent sequences were obtained from HLA‐A2.1 molecules. One of the peptides showed sequence homology to the hepatitis B virus (HBV) pre‐S protein, one to aldehyde dehydrogenase, and the other to no known protein. Two independent sequences were obtained from HLA‐B44, B13 molecules: one showed sequence homology to the human c‐abl protein, the other showed no homology to any known protein. A synthetic biotinylated peptide based on the HBV pre‐S peptide sequence was confirmed to bind to HLA‐A2.1 gene‐transfected L cells. These data suggested that peptides potentially recognized by cytotoxic T cells can bind to HLA class I molecules on tumor cells in vivo.