假基因GOLGA2P10拷贝数变异调控癌基因GOLGA2与人群肺癌发生发展的关联及其分子机制研究

Pseudogene was previously considered to be “junk DNA” without biologic function but now has become a heated issue in the field of cancer research, because recent studies have identified some of them with function on regulating activity of the corresponding coding genes. In some preliminary experiments, we have found that the frequency of high copy number of copy number variation-72323 (CNV-72323) that is located in a pseudogene GOLGA2P10 was significantly higher in lung cancer cases than controls. Meanwhile, the pseudogene GOLGA2P10 was up-regulated in lung cancer tissues compared to adjacent normal tissues. Interestingly, the expression of GOLGA2P10 exerted significant correlation with that of its corresponding coding gene GOLGA2, which is recognized to be an oncogene. The oncogene is also up expressed in cancer tissues and the copy number of CNV-72323 was significantly correlated with both GOLGA2P10 and GOLGA2. By bioinformatics analysis, we further found that the GOLGA2P10 and GOLGA2 have shared some miRNA binding sites, indicating a hypothesis that the CNV-72323 could enhance GOLGA2P10 expression and thus indirectly GOLGA2 high expression to increase the risk of lung cancer underlying a mechanism of competition against the miRNA binding. Here, this project intends to assess the association between the CNV-72323 and lung cancer risk as well as prognosis in two-center and large population case-control studies; to investigate the regulation mechanism of the CNV-72323 on regulating the expression of GOLGA2P10 as well as GOLGA2P10 on that of GOLGA2 with a series of biological experiments conducted both in vivo and in vitro, especially with several human bronchial epithetical model cell lines carrying different copy number of the CNV-72323. Through this analysis, we will finally illustrate the biological mechanism of CNV-72323 on lung cancer risk and prognosis. This project will help to clarify the mechanism of lung cancer pathology and provide scientific evidences for prevention and treatment of lung cancer.

假基因之前被认为是没有功能的“垃圾DNA”，近年研究发现某些假基因可参与调控相应同源编码基因的表达，假基因调控由此成为肿瘤研究新热点。课题组预实验发现肺癌病例组存在假基因GOLGA2P10高拷贝数变异CNV-72323；癌组织中该假基因和相应编码基因GOLGA2均高表达，并与高拷贝数变异呈正相关。生物信息学分析发现该假基因和具有癌基因功能的GOLGA2存在共有的miRNA结合位点，提示该假基因高拷贝数变异将增强假基因表达，并通过与癌基因竞争miRNA结合的方式，促进癌基因GOLGA2表达进而增加人群的肺癌发病风险。本课题拟通过两中心、大样本病例-对照研究，分析上述假基因拷贝数变异与肺癌发病、预后的关联；构建携带假基因不同拷贝数的模式细胞系，通过系统的体内、体外研究方法，揭示假基因GOLGA2P10拷贝数变异影响肺癌发生发展的生物学机制，为肺癌高危人群筛查和防治提供新的科学依据。

传统观点认为假基因是基因组中没有功能的“DNA垃圾”，但近年研究发现某些假基因可影响相应同源编码基因的表达，参与体内细胞分化、炎症和凋亡等重要生命过程。其在肿瘤中的作用角色受到关注。本项目旨在前期预实验基础上，分析探讨假基因GOLGA2P10拷贝数变异与我国人群肺癌发生发展的关联性，及揭示其生物学机制。项目在广州和苏州两地区人群中揭示了假基因GOLGA2P10的拷贝数变异CNV-72323与我国人群肺癌发病存在关联性，发现随着CNV-72323拷贝数的增加，肺癌的发病风险也随之增加。显性模型分析结果显示：与2-copy携带者相比，3/4-copy携带者发生肺癌的风险增加了73%（OR=1.73，95%CI=1.41-2.11）；苏州人群研究结论与广州人群一致，3/4-copy携带者发生肺癌的风险是2-copy携带者的1.77倍（OR=1.77，95%CI=1.34-2.35）。系列功能实验显示，CNV-72323与GOLGA2P10表达呈正相关，CNV-72323拷贝数增加会导致GOLGA2P10表达升高；GOLGA2P10具有癌组织高表达特异性，其能够增强肺癌细胞的增殖、克隆形成、裸鼠成瘤以及迁移侵袭能力。机制实验显示，GOLGA2P10可通过竞争性结合miR-940而上调促癌基因GOLGA2的表达，进而发挥促癌功能。以上结果说明，CNV-72323可通过影响类促癌基因GOLGA2P10而影响我国人群肺癌的发病风险，是我国人群肺癌易感性评估和高危人群筛选的一个潜在标志。GOLGA2P10发挥促癌作用，可作为肺癌治疗的潜在新分子靶标。