线粒体miRNA调控化疗诱导舌鳞癌上皮间质转化的机制研究

Recent studies indicate inhibition of mitochondrial oxidative phosphorylation (OXPHOS) could promote cancer cell metastasis. miRNAs, predominantly localized to the mitochondria, could target and regulate mitochondrial genome expression with a inhibition of OXPHOS in rat ventricular myocytes. Hitherto，it is not yet clear whether mitochondrial miRNAs are equipped with similar functions and regulate cancer cell metastasis. Our previous study demonstrated cisplatin could induce epithelial mesenchymal transition (EMT ) in tongue squamous cell carcinoma(TSCC). In our preliminary experiments, we found that OXPHOS significantly decreased in cisplatin-induced EMT cell lines. miRNA microarray screening revealed overexpression of miRNAs in mitochondria of EMT cell line than that in parent cell. Meanwhile, miR-513b，one of overexpression of mitochondrial miRNAs in EMT cell line，was found regulating OXPHOS and EMT in EMT cell lines. Accordingly, we propose mitochondrial miRNA could target and regulate mitochondrial genome expression, ultimately inhibiting OXPHOS and activating EMT. In follow-up in vivo and in vitro studies, we will identify distinct mitochondrial miRNA target regulation of mitochondrial genome expression and mechanism of activation of chemotherapy-induced EMT in TSCC. Finally, clinical significance will be justified through specimens of TSCC patients. This project intends to clarify mitochondrial miRNA target regulation of mitochondrial genome expression and mechanism of chemotherapy-induced EMT, which will develop new thinking on detection caner metabolism regulating metastasis.

新近研究表明抑制癌细胞线粒体氧化磷酸化可促进其转移，大鼠心肌细胞线粒体富集的miRNA可靶向调控线粒体基因组并抑制氧化磷酸化，而癌细胞中线粒体miRNA是否具有类似功能并影响其转移能力目前尚不清楚。我们前期研究发现顺铂可诱导舌鳞癌发生上皮间质转化(EMT)；我们预实验发现顺铂诱导的EMT细胞氧化磷酸化明显减弱；miRNA芯片发现EMT细胞线粒体较亲本细胞具有高表达的miRNA, 其中miR-513b可调控氧化磷酸化和EMT。据此，我们推测舌鳞癌线粒体miRNA可靶向调控线粒体基因组并抑制氧化磷酸化继而激活化疗压力下细胞EMT。后续研究我们将通过体内外实验明确舌鳞癌线粒体miRNA与线粒体基因组的靶向调控关系及其对EMT的调控机制，最后依据临床样本验证其临床意义。本课题通过阐明线粒体miRNA与线粒体基因组的靶向调控关系及其对化疗诱导EMT的调控机制，将为研究肿瘤代谢对转移的调控提供新思路。

最近发现在细胞线粒体中存在miRNA，尤其在心肌细胞和肌细胞中更为常见，这类miRNA被定义为线粒体miRNA （mitomiR）。由于线粒体的特殊性，mitomiR的功能较胞浆miRNA存在一定的差异。在本课题的研究中，我们发现舌鳞癌细胞中也存在mitomiR。在这些mitomiR中，miR-193b-5p在舌鳞癌细胞Cal27 和Scc9均表达升高，而且它通过上调线粒体基因组中MT-ND4的表达从而增强肿瘤细胞氧化磷酸化功能。在耐药细胞株Cal27-re和 Scc9-re中，miR-193b-5p 的表达下调，氧化磷酸化功能相应减弱，而有氧糖酵解的功能则增强。因此，在耐药细胞中乳酸生成增加，使细胞外的pH值较细胞内降低，并促进舌鳞癌细胞的耐药。而在动物实验中，我们也发现在亲本细胞中低表达miR-193b-5p 能够引起细胞耐药，而在耐药细胞中高表达miR-193b-5p 则增强舌鳞癌细胞的化疗敏感性。临床分析提示miR-193b-5p和MT-ND4的表达升高则病人的预后较好。我们的研究提示增强miR-193b-5p的表达，可能成为克服舌鳞癌耐药的新策略。