A Novel Cancer Testis Antigen That Is Frequently Expressed in Pancreatic, Lung, and Endometrial Cancers

Purpose: To isolate cancer testis antigens that are expressed in pancreatic cancers and may be useful in clinical applications. Experimental Design: To efficiently isolate cancer testis antigens, a testis cDNA library was immunoscreened (SEREX) with serum from a patient with pancreatic ductal adenocarcinoma. The expression of isolated antigens in various cancer cell lines and tissues was evaluated by reverse transcription-PCR and Northern blot analyses. The immunogenicity of the antigen in cancer patients was evaluated by detection of the IgG antibody in sera from patients with various cancers. Results: Of the three clones isolated through screening of a total of 2 × 106 cDNA library clones, one clone (KU-CT-1) was found to be expressed in various cancers but only in testis among normal tissues, indicating that it was a novel cancer testis antigen. The KU-CT-1 gene is located on chromosome 10p12 and produces two splice variants, which encode proteins of 397 and 872 amino acids, respectively. KU-CT-1 was expressed in pancreatic cancer tissues (3 of 9, 33%), lung cancer tissues (9 of 24, 38%), and endometrial cancer tissues (7 of 11, 64%). Specific serum IgG antibodies were detected in 3 of 20 pancreatic cancer patients, 2 of 12 endometrial cancer patients, 1 of 18 colon cancer patients, and 1 of 10 prostate cancer patients but not detected in 30 healthy individuals. Conclusions: KU-CT-1 is a new cancer testis antigen that is expressed in pancreatic, lung, and endometrial cancers and may be useful for diagnosis and immunotherapy for patients with various cancers.