肾癌骨转移的基因组学研究

Bone metastases are common in advanced renal cell carcinoma (RCC), which results in poorer survival because of the fact that the treatment by diphosphonate is non-specific. The deluge of genomic data is of great importance to understand the carcinogenesis of primary RCC, but the mechnisms of secondary RCC remains elusive, partly owing to the dearth of genomic data. We, thereafter, hypothesized that exploring the whole genomic feature is beneficial to probe into the bone metastases of RCC. What’s the interaction between gene mutations and epigenetic alteration to facilitate RCC skeleton spreading? In this proposal, four platforms (whole genome mutation signatures, DNA-methylome, DNA-hydromethylome, and TCGA data repository of RCC) will be utilized in this integrative analysis. So far, we have achieved pivotal development for this project. First, we had collected bone metastatic samples from 23 RCC patients. Secondly, we had solved the issue of genomics library construction with as little as 1ng DNA, especially in formalin fixed-paraffin embedded samples. Thirdly, the interim analysis from two advanced RCC patient showed that both genomic mutations and epigenetic alterations were involved in metastasis. Furthermore, our previous works verified that SPOP is a hub in tumorigenesis of RCC by degrading PTEN protein and the corresponding inhibitor was invented recently. Moreover, we found the epigenetic marker, 5hmC level, is absolutely decreased globally and the loss of 5hmC leads to the gain of 5mC, especially in the gene body region of RCC. Based on these advancements, we are seeking to provide insights into the metastatic process of RCC via whole genomic comparison of mutations and epigenetic alterations. Taken together, we further dedicate to explore the bone metastatic cascade in RCC using genomic and epigenomic strategy. To some degree, our proceedings will speed up omic-based study in cancer metastasis and translation medicine.

肾癌骨转移的治疗无特异性；预后差。肾癌基因组学数据丰富了对肾癌原发灶发生发展的理解；暂无转移灶组学数据--转移灶手术样本少且多为石蜡包埋样本。我们设想：探究肾癌骨转移的组学特性有望解析基因突变或表观遗传变异如何促进转移？本研究将用四个平台（全基因组突变谱、甲基化谱、羟甲基化谱、TCGA 肾癌数据库）剖析这一适应性过程。前期基础如下：①已采集23位肾癌骨转移样本；②解决了少量DNA建库瓶颈(尤其石蜡DNA)；③初步数据表明基因突变和表观变异都参与了骨转移过程。更重要的是，我们已证实肾癌在低氧环境下诱发SPOP蛋白过表达，降解PTEN等重要蛋白而促发肾癌；已研发了相应抑制剂。此外，在全基因组单碱基水平，我们发现肾癌DNA羟甲基化和甲基化呈现此消彼长的规律。综上，我们将利用基因组学平台研究肾癌原发灶/骨转移灶的基因突变谱和表观变异谱，为肾癌骨转移的医学转化提供理论指导和数据支持。

转移性肿瘤的演化轨迹在很大程度上是未知的，而其对于肿瘤的防治至关重要。本项目对8个肾透明细胞癌患者的19个肿瘤样本及配对的8个肾组织癌旁样本进行了外显子组测序或全基因组测序。描绘了8个肾癌患者骨转移发生发展的基因组变异图谱。我们鉴定了转移灶和原发肿瘤的克隆起源和平行进化模式，同时发现他们的进化分支在肿瘤发展早期就已经发生了分化。更大规模的基因组变异包括体细胞拷贝数变异（SCNAs）和杂合性缺失（LOHs）发生在转移灶中。其中我们发现14q的LOH、14q32.31的缺失和6p22.2的获得是转移过程中被高度选择的事件。对SCNA区域内多个基因的进一步功能验证表明，这些基因的表达变化可增加转移发生的风险，同时是潜在治疗靶点。该研究提供了肾癌骨转移基因组进化的模式，促进了基础研究向转化研究的过渡。