铬通过抑制miR-218/497在肿瘤形成和转移中的作用及分子机制

Human chromium exposure is associated with lung cancer development. However, the molecular mechanisms of chromium-induced malignant transformation and carcinogenesis remain to be elucidated. Our preliminary studies showed that miR-218 and miR-497 were dramatically down-regulated in chromium-transformed cells（CrT）compared with their parental bronchial epithelial BEAS-2B cells（B2B）. Moreover, CrT showed higher activity of aerobic glycolysis, overexpression of miR-218 and miR-497 in CrT attenuated the abilities of aerobic glycolysis, cell proliferation and colony formation. We hypothesize that chromium inhibits miR-218 and miR-497 expression for inducing aerobic glycolysis, malignant transformation of epithelial cells, tumor growth and metastasis through overexpression of HK2 and LDHA. To test this hypothesis, we will perform three aims as follows: 1.to investigate the molecular mechanism of chromium-induced down-regulation of miR-218 and miR-497 expression ; 2.to elucidate whether chromium induces aerobic glycolysis, tumor growth and metastasis through regulation of miR-218, miR-497 and influences HK2 and LDHA; 3.to recruit human subjects who have occupational exposure to chromium and to determine the.correlations among levels of miR-218, miR-497, HK2 and LDHA using the subject blood samples or serum, which will help to test the translational application of our new findings, and identify new biomarkers for the purpose of malignant transformation of epithelial cells and occupational health surveillance.

铬职业暴露与肺癌的发生发展密切相关，其分子机制仍未完全阐明。我们的前期实验结果发现：相比正常的支气管上皮细胞（B2B），铬转化的上皮细胞（CrT）中miR-218和miR-497的表达水平下调，CrT细胞的有氧糖酵解水平高于B2B细胞，过表达miR-218和miR-497降低CrT的有氧糖酵解水平、细胞增殖和克隆形成能力。因此我们提出假说：铬诱导上皮细胞中miR-218和miR-497表达水平的降低，上调HK2和LDHA的表达水平从而调节细胞能量代谢等，促进上皮细胞恶性转化及肿瘤的生长和转移。我们将从三个方面验证假说：1.阐明铬下调miR-218和miR-497表达的分子机制；2.阐明铬是否通过miR-218和miR-497影响HK2和LDHA调节能量代谢和肿瘤的生长与转移；3.收集铬暴露职业人群外周血，在人群中加以验证。本项目的完成将为上皮细胞恶性转化及铬职业病的防治提供新的生物标记物。

铬(Chromium, Cr)是应用极为广泛的金属，铬暴露与肺癌的发生发展密切相关，其分子机制仍未完全阐明。基因组的表观遗传修饰在导致肿瘤发生发展过程中起着重要作用， 近年来的研究表明,调控肿瘤发生发展的表观遗传修饰主要包括DNA甲基化或乙酰化，组蛋白修饰和蛋白质磷酸化以及微小RNA（microRNAs, miRNAs）的转录后修饰等。但是，miRNAs在环境致癌过程中作用及分子机制的相关研究还处于起步阶段。我们的研究发现：相比正常的支气管上皮细胞（B2B），铬转化的上皮细胞（Cr-T）中miR-218的表达水平下调，Cr-T细胞的葡萄糖消耗和乳酸产生能力高于B2B细胞，过表达miR-218降低Cr-T的有氧糖酵解水平、细胞增殖和微管形成能力。此外，我们的研究证实HK2和LDHA是miR-218的靶基因，下调HK2和LDHA的表达水平可以明显抑制细胞生长和微管形成等。最后，我们通过动物实验阐明铬通过miR-218影响HK2和LDHA的表达，参与调控上皮细胞恶性转化及肿瘤的生长等，并且收集了铬暴露职业人群外周血，在人群中加以验证miR-218、HK2和LDHA在铬暴露致癌过程中的作用。本研究将为铬致癌提供新的分子机制，项目的完成将为上皮细胞恶性转化及铬职业病的防治提供新的生物标记物。