Department of Immunology, School of Basic Medical Sciences, Key Laboratory of Immunology, Ministry of Health, Peking University Health Science Center, Beijing 100191, PR China.
Eur J Cancer. 2011 Sep;47(13):2068-76. doi: 10.1016/j.ejca.2011.04.021. Epub 2011 May 18.
Inappropriate gene silencing and subsequent promiscuous activity define the transformation of many solid tumours including renal cell carcinoma (RCC). Here, we report that UNC5C, one of the Netrin-1 receptors, was frequently inactivated in RCC cell lines and primary tumours. UNC5C protein was expressed in the proximal convoluted tubules of the human kidney, the presumed origin of clear cell RCC (ccRCC) and papillary RCC (pRCC). Compared to paired adjacent non-malignant tissues, both UNC5C mRNA and protein expression were significantly down-regulated in RCC. Immunohistochemical analysis showed that UNC5C was inactivated in 94.3% of the samples and the loss of UNC5C occurred at the early stage of RCC. Methylation specific PCR showed that UNC5C promoter was methylated in two renal carcinoma cell lines. Pharmacologic demethylation alone or in combination with inhibition of deacetylation dramatically induced UNC5C expression. Furthermore, bisulfite genomic sequencing (BGS) confirmed that dense methylation existed in UNC5C promoter. In paired tumour samples, UNC5C methylation was observed in 12 out of 44 patients (27.3%). Moreover, we analysed the loss of heterozygosity (LOH) of UNC5C in renal cell carcinoma, the LOH was observed in 27 out of 44 patients (61.4%). Finally, restoration of UNC5C expression suppressed the colony formation of renal carcinoma cells. In addition, UNC5C inhibited tumour cell proliferation, migration and enhanced chemosensitivity to cisplatin and etoposide. Therefore, UNC5C acts as a tumour suppressor in RCC and is down-regulated in RCC. Loss of heterozygosity and DNA methylation contribute to the inactivation of UNC5C in renal cell carcinoma.
不适当的基因沉默和随后的混杂活性定义了许多实体瘤的转化，包括肾细胞癌（RCC）。在这里，我们报告 UNC5C，一种 Netrin-1 受体，在 RCC 细胞系和原发性肿瘤中经常失活。UNC5C 蛋白在人肾脏的近端卷曲小管中表达，这是透明细胞 RCC（ccRCC）和乳头状 RCC（pRCC）的推测起源。与配对的相邻非恶性组织相比，RCC 中 UNC5C mRNA 和蛋白表达均显著下调。免疫组织化学分析显示 UNC5C 在 94.3%的样本中失活，并且 UNC5C 的丢失发生在 RCC 的早期阶段。甲基化特异性 PCR 显示 UNC5C 启动子在两个肾癌细胞系中发生甲基化。单独或联合抑制去乙酰化的药物去甲基化可显著诱导 UNC5C 表达。此外，亚硫酸氢盐基因组测序（BGS）证实 UNC5C 启动子存在密集的甲基化。在配对的肿瘤样本中，在 44 例患者中的 12 例（27.3%）中观察到 UNC5C 甲基化。此外，我们分析了肾细胞癌中 UNC5C 杂合性丢失（LOH），在 44 例患者中有 27 例（61.4%）观察到 LOH。最后，恢复 UNC5C 表达抑制了肾癌细胞的集落形成。此外，UNC5C 抑制肿瘤细胞增殖、迁移并增强顺铂和依托泊苷的化疗敏感性。因此，UNC5C 在 RCC 中作为肿瘤抑制因子发挥作用，在 RCC 中下调。杂合性丢失和 DNA 甲基化导致 UNC5C 在肾细胞癌中的失活。
