This study describes the identification and characterization of a novel tumor antigen, NY-ESO-1, using the SEREX (Serological Analysis of Recombinant cDNA Expression Libraries) approach. The method involves screening recombinant cDNA libraries with autologous patient sera to identify immunogenic tumor antigens. In this case, the researchers applied SEREX to an esophageal squamous cell carcinoma sample and identified several candidate antigens, including NY-ESO-1. NY-ESO-1 was found to be expressed in normal testis and ovary tissues but aberrantly expressed in various human cancers, including melanoma, breast cancer, bladder cancer, prostate cancer, and hepatocellular carcinoma. The protein encoded by NY-ESO-1 has no known homology to any other protein and is predicted to have a molecular mass of 17,995 Da. The expression pattern of NY-ESO-1 suggests it belongs to a family of immunogenic testicular antigens that are aberrantly expressed in human cancers in a lineage-nonspecific manner. This finding highlights the potential of these antigens as targets for cancer vaccination. The study also discusses the limitations of traditional autologous typing methods and the advantages of SEREX in identifying antigens across different tumor types.This study describes the identification and characterization of a novel tumor antigen, NY-ESO-1, using the SEREX (Serological Analysis of Recombinant cDNA Expression Libraries) approach. The method involves screening recombinant cDNA libraries with autologous patient sera to identify immunogenic tumor antigens. In this case, the researchers applied SEREX to an esophageal squamous cell carcinoma sample and identified several candidate antigens, including NY-ESO-1. NY-ESO-1 was found to be expressed in normal testis and ovary tissues but aberrantly expressed in various human cancers, including melanoma, breast cancer, bladder cancer, prostate cancer, and hepatocellular carcinoma. The protein encoded by NY-ESO-1 has no known homology to any other protein and is predicted to have a molecular mass of 17,995 Da. The expression pattern of NY-ESO-1 suggests it belongs to a family of immunogenic testicular antigens that are aberrantly expressed in human cancers in a lineage-nonspecific manner. This finding highlights the potential of these antigens as targets for cancer vaccination. The study also discusses the limitations of traditional autologous typing methods and the advantages of SEREX in identifying antigens across different tumor types.