Identification of new tumor antigens using testis-specific proteins

肿瘤-睾丸(CT)抗原在正常睾丸和多种肿瘤中表达，是肿瘤免疫治疗的靶点。为了确定新的CT抗原，我们采用了两种策略：分离在肿瘤细胞中也表达的睾丸特异基因，以及从癌症患者的血清中筛选睾丸cDNA文库。用SAGE(基因表达序列分析)分析了睾丸的mRNA表达谱，在睾丸SAGE文库中鉴定了大约20,000个标签，包含12,400个不同蛋白质的标签。通过与其他正常组织和癌组织SAGE数据库的比较，我们获得了新的CT抗原的候选标签。然而，对这些选定标签的更多滞留分析表明，包含这些高表达标签的基因并不是睾丸和癌症所特有的。因此，在这些选定的基因中没有发现新的CT。对具有相对低表达的所选标签的进一步分析仍有待执行。用2例胰腺癌患者和1例膀胱癌患者的血清筛选睾丸cDNA文库，获得5个阳性克隆。从胰腺癌患者血清中分离到的CT-1是一个未在基因数据库中注册的新基因。5例胰腺癌患者和10例肾癌患者血清中分别有1例和1例检测到CT-1抗体，而20例健康人血清中未检测到CT-1抗体。CT-1仅在正常组织中表达，在15个胰腺癌细胞株中有1个表达，在5个胰腺癌组织中有2个表达。这些结果表明CT-1是一种在某些胰腺癌中表达的新的CT抗原。

Cancer-Testis (CT) antigens that are expressed in normal testis and various tumors are promising targets for immunotherapy for cancer. To identify new CT antigens, we used 2 strategies: Isolation of testis specific genes that also express in tumor cells, and screening of a testis cDNA library with sera from cancer patients. Profile of mRNA of testis was analyzed using SAGE (serial analysis of gene expression), and approximately 20,000 tags containing 12,400 tags for distinct proteins were identified in the testis SAGE library. By comparing it with SAGE databases from selected other normal and cancer tissues, we have obtained candidate tags for new CT antigens. However, more detained analysis of these selected tags revealed that genes containing these tags with high expression were not specific for testis and cancer. Thus, new CT was not identified among these selected genes. Further analysis of selected tags with relatively low expression remains to be performed. The testis cDNA library was screened with sera from 2 pancreatic cancer patients and a bladder cancer patient, and 5 positive clones were obtained. CT-1 isolated with the pancreatic cancer patient's serum was a novel gene not registered in the gene database. IgG antibodies for CT-1 was detected in 1 of 5 sera from pancreatic cancer patients and 1 of 10 sera with renal cancer patients, but was not detected in 20 sera from healthy individuals. CT-1 was expressed in only testis among normal tissues tested and in 1 of 15 pancreatic cancer cell lines and 2 of 5 pancreatic cancer tissues. These results demonstrated that CT-1 was a new CT antigen expressed in some pancreatic cancers.