MICA/B ceRNAs调控NKG2D介导的抗肿瘤免疫应答机制的研究

Cancer immune surveillance is considered to be an important host protection process to inhibit carcinogenesis and to maintain cellular homeostasis. The major histocompatibility complex class I-related molecules A and B (MICA and MICB) are NKG2D ligands that play important roles in tumor immune surveillance. Mounting evidence has shown that the expression of MICA and MICB is regulated by a variety of miRNAs. Pandolfi and colleagues have shown that RNAs regulate each other using miRNA response elements (MREs) and this mechanism is known as "competing endogenous RNA" (ceRNA). And the ceRNAs activity forms a large-scale regulatory network across the transcriptome, greatly expanding the functional genetic information in the human genome and playing important roles in pathological conditions, such as cancer. Dysregulation of ceRNAs network possibly causes diseases. Our preliminary study showed that MICA/B might be regulated by the ceRNAs network. In the current study, we aim to identify the ceRNAs of MICA and MICB and address the molecular mechanisms on how ceRNAs regulate NKG2D-mediated immune elimination of tumor cells via MICA/B. Therefore, we will (1) identify the ceRNAs of MICA /B by bioinformatics and experimental methods; (2) investigate how MICA /B ceRNAs regulate the expression of MICA/B, and whether the ceRNAs regulate the MICA/B via a miRNA-dependant manner; (3) study how miRNAs target MICA/B ceRNAs; (4) clarify whether MICA/B ceRNAs affect the NKG2D-mediated immune response; and (5) perform the correlation analysis among the expression of ceRNAs, miRNAs and MICA/B in tumor specimens. Our study will shed light on understanding the roles of "ceRNAs-miRNAs-MICA/B" network in tumor immunity, and tumor cell escape mechanisms during tumor progression; and may provide new ideas for identification of targets for anti-tumor immunotherapy.

在肿瘤免疫监视过程中，主要组织相容性复合物I类相关分子A和B（MICA和MICB）作为NKG2D的配体，起着非常重要的作用。研究表明，多种miRNAs能够通过miRNA 应答元件（MREs）调控MICA/B的表达。竞争性内源RNA（ceRNA）理论，即转录物可通过MREs竞争结合相同的miRNAs来调控各自的表达水平，已在多种疾病模型中得到证实，且ceRNAs网络的失调可能导致肿瘤的发生。我们的前期研究发现PHLPP2可能是MICA/B的候选ceRNA，暗示MICA/B可能受到ceRNAs网络的调节。本项目拟进一步鉴定参与调节MICA/B表达的ceRNAs分子；并通过研究它们对MICA/B的调控机制，构建"ceRNAs-miRNAs-MICA/B"的作用网络；同时，阐明ceRNAs通过MICA/B调控NKG2D介导的抗肿瘤免疫应答的分子机理。本研究可能为探讨肿瘤免疫治疗提供新思路。

癌症免疫监视是一种的重要保护机制，它可以抑制癌症的发生，并维持细胞稳态。主要组织相容性复合物I类相关分子A和B（MICA和MICB）作为NKG2D的配体，在肿瘤免疫监视过程中起着非常重要的作用。本项目中，我们通过生物信息学方法预测了MICA和MICB的ceRNAs，利用TCGA数据库分析了六类肿瘤样本中MICA/B ceRNAs与MICA/B表达的相关性；进一步利用实验方法，在多种细胞系中研究BCL11B对MICA和MICB表达的影响；研究BCL11B对MICA和MICB的调节是否依赖于miRNA的表达；研究靶向MICA/B的miRNAs对BCL11B的调节；在体内和体外研究BCL11B对NKG2D介导的细胞免疫应答的影响；研究BCL11B对结直肠癌细胞增殖的影响，及其与结直肠癌患者的预后关系。结果发现，BCL11B作为ceRNA调节细胞的MICA和MICB；并且，BCL11B介导的MICA和MICB调节依赖于miRNA的表达；我们建立了“BCL11B-miRNA-MICA/B”的调控网络，阐明了BCL11B通过MICA/B调控NKG2D介导的免疫应答机制，为探讨肿瘤免疫治疗提供新思路。另外，我们也对miR-340在卵巢癌发生发展中的分子机制进行了研究。我们发现miR-340在卵巢癌组织中的表达明显下调，过表达miR-340能抑制卵巢癌细胞的增殖和转移。进一步的机制研究揭示miR-340/FHL2可以通过调控Wnt/β-catenin信号通路，抑制卵巢癌增殖和转移，这可能为卵巢癌治疗提供新的干预靶点。