胃癌相关基因IRX4的发现及生物学功能研究

IRX4是位于5p15.33位点的同源盒基因，该基因调控胚胎发育期的器官发育，在出生后的生物学作用以及与肿瘤发生发展的关系尚不清楚。课题组近期在研究胃癌对酪氨酸激酶抑制剂（TKI）药物的反应性差异时发现，视黄酸受体ɑ（RARA）分子网络的活性与肿瘤对TKI类药物的应答性密切相关，IRX4恰恰是该分子调控网络的重要基因之一。我们推测：IRX4可能单独或者与RARA相互作用参与胃癌的发生发展或对药物治疗的应答，但迄今缺乏有力的实验研究证据。为了探究IRX4的确切生物学作用，本研究拟构建稳定过表达及稳定敲低IRX4的真核表达载体，通过体外实验和动物实验，探究IRX4对细胞增殖、细胞侵袭、细胞周期、凋亡以及对TKI类药物的反应差异；通过免疫共沉淀、蛋白质共定位以及染色质免疫沉淀测序等实验，探究IRX4与RARA相互作用以及对下游靶基因的调控。本项目的实施有望为胃癌精准诊治提供有价值的分子靶标。

IRX4 is a member of homeobox genes located on 5p15.33, and plays important role in embryonic development. However, the postnatal function of IRX4 and its relationship to tumor development is not clear yet. In our recent work, we studied the responsive discrepancy of cancer cells to targeted drug of tyrosine kinase inhibitors (TKI) on gastric cancer, and found that the active status of retinoid acid receptor alpha (RARA) regulatory network is closely related to responsiveness of cancer cells. IRX4 is an important interaction protein in RARA regulatory network. We suppose that IRX4 or IRX4 interacting with RARA may play important roles on carcinogenesis and development of gastric cancer as well as on responsiveness to drug therapy. However, it needs more experimental evidences. In order to confirm our speculation that IRX4 was involved in the development of stomach cancer, and further explore the molecular regulatory mechanisms, we will construct the stable expressed IRX4 eukaryotic expression vector or stable knockdown IRX4 vector and analyze the biological functions such as cell growth, cell invasion, cell cycle, apoptosis as well as responsiveness to TKI by means of in vitro and in vivo experiments. We also analyze the protein-protein interaction between IRX4 and RARA and the downstream target genes by co-immunoprecipitation (Co-IP) or chromatin immunoprecipitation-sequencing (ChIP-Seq), etc. This study will enrich the understanding of IRX4 homeobox gene, and provide valuable molecular targets for precise diagnosis and treatment of stomach cancer.