Expression and prognostic significance of cadherin and detection system of ciculating cancer cells in renal cell carcinoma

大多数肾细胞癌(RCC)不表达E-钙粘蛋白和肾近端小管上皮细胞。相反，肾细胞癌在体外频繁表达钙粘蛋白-6和N-钙粘蛋白以及与其生物学行为相关的钙粘蛋白-6。因此，我们使用抗人钙粘蛋白-6的单抗来研究钙粘蛋白-6是否是肾癌中有用的分子标志物。43例肾癌患者中有24例存在钙粘蛋白-6的异常表达，其预后明显较差，尤其是E-钙粘蛋白缺失者。由于肾细胞癌转移灶中钙粘蛋白-6和N-钙粘蛋白的表达一直保持不变，因此我们进一步研究了利用RT-PCR技术在循环血中检测到这些特异性钙粘蛋白的表达。然而，在健康志愿者的外周血中，用巢式RT-PCR系统频繁地检测到N-钙粘素的mRNA。在15例转移性肾癌患者中有11例检测到钙粘蛋白-6基因的表达，而在12例肾癌转移性肿瘤患者中有6例检测到钙粘蛋白-6基因的表达。考虑到需要进行定量分析以稳定该方法的敏感性，因此我们用定量RT-PCR法重新分析了外周血中钙粘蛋白-6基因的表达水平。在检测了健康志愿者外周血中钙粘蛋白-6基因的表达水平后，在13例转移性肾细胞癌患者中有9例检测到了钙粘蛋白-6基因的表达。钙粘附素-6的定量RT-PCR可能是检测肾癌患者循环血中肾细胞癌细胞的有用工具。

Most renal cell carcinomas (RCCs) do not express E-cadheirn as well as renal proximal tubular epithelium. Instead of this, RCC frequently expresses cadheirn-6 and N-cadherin and cadherin-6 correlated with biological behavior of RCC cell line in vitro. Thus, we investegated whether cadherin-6 was a useful molecular marker in RCC using monoclonal antibody against human cadherin-6. Abnormal expression of cadherin-6 was observed in 24 of 43 RCC patients and those patients siginificantly had a poorer prognosis, specially in the patietns with E-cadherin-absent RCC.Since expression of cadherin-6 and N-cadherin was preserved in the metastatic site of RCC, we next studied that RCC cells could be detected in circulating blood using RT-PCR for these specific cadherin mRNA.Both of cadheirn-6 and N-cadherin were expressed in RCC cell line, normal kidney and RCC specimens. However, in the peripheral blood from healthy volunteers N-cadherin mRNA was frequently detected using nested RT-PCR system. Cadherin-6 mRNA was observed in 11 out of 15 patietns with metastasis, whereas in 6 out of 12 patients withour metastasis of RCC.It has been considered that quantitative nanalyses should be needed to stabilize the sensitivity of this PCR assay, so that we reanalysed the expression level of cadherin-6 mRNA in peripheral blood using quantitative RT-PCR.After cut off level of cadhiern-6 mRNA was determined in healthy volunteers, cadherin-6 mRNA was detected in 9 out of 13 patietns with metastatic RCC.In contrast, in 36 RCC patients withour metastasis, cadheirn-6 mRNA was detected in 13 patietns before nephrectomy and it decreased into normal range in 6 patients after surgery. Quantitative RT-PCR for Cadherin-6 might be a useful tool to detect RCC cells in ciculating blood in RCC patients.