Molecular detection of circulating renal cell carcinoma cells by RT-PCR

抗人肾细胞癌(RCC)的鼠源性单抗G250(MAbG25O)(Oosterwijk，et al，1986)能与大比例的RCC反应，但不与正常肾组织反应。MAbG25O识别的抗原存在于细胞膜中，并在几种类型的恶性肿瘤中表达。最近，G250抗原基因已被分离(Oosterwijk等人)。1995年)，数据库分析表明G250抗原与最初来源于Hela细胞的MN/CAIX相同(Pastorek等，1994)。为探讨G250抗原(MN/CAIX/G250)能否作为治疗靶点和肿瘤标记物，对147例肾细胞癌进行免疫组织化学和逆转录聚合酶链式反应(RT-PCR)分析。此外，还分析了患者外周血中提取的总RNA中MN/CA9/G250的mRNA信号。免疫组织化学结果显示128/147(87.1%)肾细胞癌组织呈强阳性表达，而正常肾组织呈弱阳性表达。对冷冻标本进行RT-PCR分析，137/147(93.2%)组织中MN/CA9/G25OmRNA信号清晰可见，且与免疫组织化学结果基本一致。尽管高级别和高分期肿瘤的表达明显低于低级别和低分期肿瘤，但大部分肿瘤表达MN/CA9 IX/G250蛋白和mRNA.RT-PCR分析显示循环中存在MN/CA9/G25O表达细胞。这些发现表明，该抗原可能是一种潜在的治疗靶点和肾癌的诊断标志。

A murine monoclonal antibody G250 (MAbG25O) raised against human renal cell carcinoma (RCC)(Oosterwijk, et al, 1986) has been known to react with a large proportion of RCC, but not with the norma1 kidney tissue. The antigen recognized by MAbG25O is present in the plasma membrane and expresses in several types of malignancies. Recently, G250 antigen gene has been isolated (Oosterwijk et al. 1995), and database analysis revealed that G250 antigen is identical to MN/CA IX originally deribed from Hela cell (Pastorek et al, 1994). To determine whether G250 antigen (MN/CA IX/G250) could be a potential therapeutic target and a tumor marker, a total of 147 cases of RCC were investigated immunohistochemically as well as, by reverse transcriptase polymerase chain reaction (RT-PCR) anilysis. In addition, total RNAs extracted from patients' peripheral blood samples were analyzed for MN/CA9/G250 mRNA signals. Immunohistochenistry resulted in strong expression in 128/147 (87.1%) of RCC, in contrast to the lack of expression observed in normal tissues. RT-PCR analyses of frozen specimens resulted in the clear detection of MN/CA9/G25OmRNA signals in 137/147 (93.2 %), and despite of the subtle differences, the results were almost identical to those for immunohistochemistry. Although high grade and stage tumors exhibited significaitly lower expression than low grade and stage tumors, a large proportion of tumors expressed MN/CA9 IX/G250 protein as well as mRNA.RT-PCR analysis of patients' blood samples revealed the presence of circulating MN/CA9/G25O expressing cells. These findings suggest that this antigen may be a potential therapeutic target as well as diagnostic marker for RCCs.