长链非编码RNA HOTTIP参与小细胞肺癌耐药的分子机制研究

Small cell lung cancer (SCLC) is characterised by high relapse rates and a ubsequent poor prognosis because of chemoresistance. Our previous study showed that HOTTIP was upregulated in SCLC multidrug resistance cells (H69AR) as compared to parental H69 cells using lncRNA microarray. Down-expression of HOTTIP in resistant H69AR cells led to increased chemosensitivity to Cisplatin through increasing cell apoptosis. To further investigate the molecular mechanism of HOTTIP regulating chemoresistance of SCLC, we intends to use two different cell models of SCLC resistant cells to carry out the following studies: (1) Up or down regulation of HOTTIP by transfection of overexpressed plasmid or siRNA, cell sensitivity to chemotherapeutic drugs is measured by MTT and flow cytometry. (2) The clinical significance of HOTTIP expression is examined in SCLC tissues or blood samples. (3) The relationship between HOTTIP expression and tumor growth is investigated in nude mice bearing SCLC. (4) cDNA microarray and proteomics techniques will be performed to analyze the molecular network of HOTTIP regulation of drug resistance in small cell lung cancer at mRNA and protein levels. Meanwhile, methylation analysis is also applied by microarray. Through this research project, the molecular mechanism of chemoresistance of SCLC will be further enriched and provide the evidence for the next step to carry out reverse resistance in small cell lung cancer based on HOTTIP signaling pathway.

小细胞肺癌患者因对化疗药物易产生耐药性而预后差。课题组先期利用人lncRNA芯片发现HOTTIP在小细胞肺癌耐药细胞H69AR中显著上调，降低HOTTIP表达，细胞对顺铂等化疗药物的敏感性显著增加。为进一步明确HOTTIP在小细胞肺癌耐药中的作用及分子机制，本课题拟利用两株小细胞肺癌耐药细胞模型H69AR和H446AR开展以下研究：（1）RNA干扰和基因转染技术降低或增加细胞中HOTTIP表达，分析细胞对化疗药物敏感性的改变；（2）分析小细胞肺癌患者临床标本中HOTTIP表达与化疗效果的关系；（3）利用裸鼠动物模型，分析HOTTIP表达与肿瘤生长的关系；（4）RNA干扰技术降低细胞中HOTTIP，cDNA芯片和蛋白质组学分析其作用的分子网络，甲基化芯片分析其相关基因的甲基化状态。通过本项目研究，进一步丰富小细胞肺癌的耐药机制，为下一步开展基于HOTTIP逆转小细胞肺癌耐药的研究提供依据。

小细胞肺癌患者对化疗药物易产生耐药性而预后很差。因此，阐明小细胞肺癌化疗抗药性的分子机制，已成为当今肺癌临床治疗学的重要研究课题之一。课题组前期发现长链非编码RNA HOTTIP与小细胞肺癌化疗耐药有关。本课题利用小细胞肺癌耐药细胞模型H69AR和H446AR，采用细胞生物学和分子生物学技术，进一步明确HOTTIP在小细胞肺癌耐药中的作用及其机制。主要研究发现（1）HOTTIP表达与小细胞肺癌细胞耐药、凋亡、增殖、细胞周期、克隆形成、裸鼠成瘤等密切相关。沉默HOTTIP可显著增加细胞对化疗药物ADM、DDP和VP-16的敏感性和细胞凋亡率、细胞周期发生S期阻滞、克隆形成能力下降、以及体内成瘤能力降低；反之，增加HOTTIP表达，显著降低细胞对化疗药物ADM、DDP和VP-16的敏感性、细胞凋亡率、克隆形成能力增强、以及体内成瘤能力增强。（2）生物信息学分析发现miR-574-5p和EZH1启动子区存在结合位点，通过双荧光素酶报告基因实验，进一步证实HOTTIP以ceRNA角色吸附miR-574-5p促进EZH1的表达。（3）生物信息学分析发现miR-216a与Bcl-2启动子区存在结合位点，通过双荧光素酶报告基因实验，进一步证实HOTTIP以ceRNA同样吸附miR-216a促进Bcl-2表达。（4）RNA pull-down实验和质谱分析结果显示，HOTTIP拉下来的蛋白包含RNA沉默复合体RISC重要蛋白Ago2，RIP实验进一步证实了Ago2蛋白与HOTTIP及miRNAs的直接结合作用，结果提示HOTTIP与两种miRNAs的相互作用是通过RISC复合体来完成的。通过本项目研究，进一步丰富小细胞肺癌耐药的分子机制，为下一步开展基于HOTTIP逆转小细胞肺癌耐药的研究提供依据。