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-钙粘附蛋白以及肾近端肾小管上皮细胞。在体外实验中，肾癌细胞频繁表达cadherin-6和N-cadherin，cadherin-6与肾癌细胞的生物学行为相关。因此，我们研究是否钙粘蛋白-6是一个有用的分子标志物在肾细胞癌使用单克隆抗体对人类钙粘蛋白-6。43例肾癌中24例cadherin-6表达异常，预后明显差，尤其是E-cadherin缺失者，由于cadherin-6和N-cadherin在肾癌转移灶中表达保留，我们接下来研究了可以使用RT-PCR检测循环血液中的这些特异性钙粘蛋白mRNA的RCC细胞。肾癌细胞系、正常肾组织及肾癌标本中均有钙粘蛋白表达。然而，在健康志愿者外周血中，N-cadherin mRNA经常使用巢式RT-PCR系统检测。在15例有转移的肾癌患者中有11例检测到钙粘蛋白-6mRNA，而在12例无转移的肾癌患者中有6例检测到钙粘蛋白-6mRNA。因此，我们用定量RT-PCR重新分析了外周血中钙粘蛋白-6 mRNA的表达水平。正常人肾组织中检测到cadherin-6 mRNA，转移性肾细胞癌中检测到cadherin-6 mRNA的有9例，36例无转移性肾细胞癌中，13例术前检测到cadherin-6 mRNA，术后6例降至正常范围。钙粘蛋白-6定量RT-PCR可作为检测肾细胞癌患者循环血中肾癌细胞的有效方法。

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.