Identification of new tumor antigens using testis-specific proteins

癌-睾丸（CT）抗原在正常睾丸和各种肿瘤中表达，是肿瘤免疫治疗的有希望的靶点。为了鉴定新的CT抗原，我们使用了两种策略：分离睾丸特异性基因，这些基因也在肿瘤细胞中表达，以及用癌症患者的血清筛选睾丸cDNA文库。利用SAGE（serial analysis of gene expression）技术分析睾丸mRNA的表达谱，在睾丸SAGE文库中鉴定出约20，000个标签，其中包含12，400个不同蛋白质的标签。通过将其与选定的其他正常和癌症组织的SAGE数据库进行比较，我们获得了新CT抗原的候选标签。然而，对这些选择的标签的更多延迟分析显示，含有这些高表达标签的基因对睾丸和癌症不是特异性的。因此，在这些选择的基因中未鉴定出新的CT。对具有相对低表达的所选标签的进一步分析仍有待进行。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是一个新基因，未在基因数据库中注册。5例胰腺癌患者和10例肾癌患者血清中分别有1例和1例检出CT-1 IgG抗体，而20例健康人血清中均未检出CT-1 IgG抗体。在检测的正常组织中，CT-1仅在睾丸中表达，在15个胰腺癌细胞系中的1个和5个胰腺癌组织中的2个中表达。这些结果表明，CT-1是一个新的CT抗原表达在某些胰腺癌。

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.