Abstract
Although CD19 CAR-T has been highly effective against B-cell blood cancers, there are few reports of successful treatments for solid cancers, probably because there are few protein antigens specifically expressed on the surface of the cancer cell membrane. The key to developing a groundbreaking CAR-T cell therapy effective against solid cancers is to "overcome the heterogeneity of cancer antigens". For this purpose, it is necessary to target multiple cancer antigens simultaneously. In this study, we performed immunohistochemical analysis of various solid cancer specimens using antibodies against ROBO1, EphB4, CLDN1, and LAT1 in addition to GPC3, which we have previously studied. These antigens were frequently expressed in various solid cancers but shown to be rarely expressed, with some exceptions, in non-cancerous normal organs adjacent to the cancer. Although ROBO1 and GPC3 are often expressed in cytoplasm, there are also cases in which they are expressed on the cell membrane depending on the type of cancer. On the other hand, it has been revealed that three antigens-EphB4, CLDN1, and LAT1-are frequently expressed only on the cell membrane of cancer cells in various solid cancers, suggesting that they may be ideal targets for CAR-T cell therapy.