New MAGE-4 antigenic peptide recognized by cytolytic T lymphocytes on HLA-A1 tumor cells

: ‘Cancer‐germline’ genes such as those of the MAGE family are expressed in many tumors and in male germline cells, but are silent in other normal tissues. They encode shared tumor‐specific antigens, which have been used in small therapeutic vaccination trials of cancer patients. Gene MAGE‐4, which is expressed in more than 50% of carcinomas of esophagus, head and neck, lung, and bladder, has two known alleles. Using PCR amplifications and digestions of the amplified product, we found that one third of the MAGE‐4‐positive samples expressed MAGE‐4a. We folded HLA‐A1 tetramers with peptide MAGE‐4a169−177 EVDPASNTY, which is homologous to MAGE‐1‐ and MAGE‐3‐encoded peptides recognized on HLA‐A1 by cytolytic T lymphocytes. Blood lymphocytes from an individual without cancer were directly labelled with these A1/MAGE‐4 tetramers. The very rare cells that were stained were sorted by flow cytometry and cloned. We isolated a cytolytic T‐lymphocyte clone that lyzed specifically cells pulsed with this MAGE‐4 peptide and HLA‐A1 tumor cells expressing MAGE‐4a, demonstrating that this antigenic peptide is processed efficiently in tumor cells. This peptide might therefore be useful for therapeutic antitumoral vaccination.