肿瘤抗原基因IGF2BP2在大肠癌的早期诊断及其功能机制的研究

The missense mutation of tumor associated antigen IGF2BP2 was identified from whole exom sequencing of colorectal cancer (CRC) samples. IGF2BP2 is oncofetal protein, which is highly expressed in fetal development and tumor, but not in mature tissue. It was verified to be recurrently mutated and highly expressed in CRC in our preliminary study. The following comprehensive analysis of IGF2BP2 in CRC would be performed in our study: 1) The protein expression of IGF2BP2 in CRC tissue and blood serum; 2) The functional study of wide-type and mutant IGF2BP2 in CRC cell line; 3) The regulation of mTOR→IGF2BP2→IGF2 pathwathy in CRC, and the effection of mutant IGF2BP2 binding with IGF2; 4) The expression of IGF2BP2 to be regulated by transcription factor HMGA2 in CRC. The aim of this study is: 1) To evaluate IGF2BP2 as an early diagnosis marker in Chinese CRC; 2) To explain the function of wide-type and mutant IGF2BP2 in CRC, and the mechanism of transcription and expression of IGF2BP2 in CRC.

本研究通过大肠癌（CRC）肿瘤样本的外显子测序，筛选到突变的肿瘤相关抗原基因IGF2BP2。该基因为癌胚基因，在胚胎发育早期以及肿瘤形成时呈高表达。我们在大样本的验证以及重测序分析中发现该基因在CRC中发生高频突变及高表达。本项目对IGF2BP2在CRC中的功能以及作用机制进行了系统研究，包括：1.CRC患者肿瘤组织及外周血血清IGF2BP2的蛋白表达水平。2.野生型及突变体IGF2BP2在CRC细胞中的功能；3.CRC细胞中 mTOR→IGF2BP2→IGF2信号通路的调控情况以及突变体IGF2BP2结合IGF2的影响；4.CRC细胞中转录因子HMGA2对 IGF2BP2的表达调控。从而预期获得的研究目标：1.评估IGF2BP2可否作为中国大肠癌患者早期诊断的标志物；2.阐述野生型及突变体 IGF2BP2在CRC细胞中的功能以及该基因参与CRC癌变的转录、表达调控的机制。

结肠癌是世界三大恶性肿瘤之一，也是中国四大高致死性癌症。近年来积累的数据表明转录后调控机制在肿瘤发生发展中起了非常关键的作用。肿瘤相关抗原基因IGF2BP2是一种重要的转录调控因子，其参与了mRNA的转移定位、稳定和转录调控。目前为止，有关IGF2BP2对结肠癌的调控机理并不清楚，本研究就此逐一展开深入研究。荧光定量PCR和免疫组化检测提示IGF2BP2在结肠癌组织中高表达，细胞学功能实验提示IGF2BP2过表达显著增强了结肠癌体外增殖活化的能力，而IGF2BP2干扰后结肠癌体外增殖活化的能力明显降低。分子功能研究表明IGF2BP2能够直接结合RAF1 mRNA的3’UTR, 从而阻止miR-195对RAF1的降解。以上结果提示mRNA转录后调控因子IGF2BP2通过IGF2BP2–miR-195–RAF1调控机制促进了结肠癌细胞的增殖。