MicroRNA-185通过靶向调节DNMT1/PTEN/Akt通路抑制肝细胞癌的生长
近来研究表明miRNAs与肝癌的发生密切相关，然而单个miRNAs的具体作用机制仍未完全阐明。我们对miR-185在肝细胞癌生物学功能和分子机制方面做了一些研究。我们发现和非肿瘤性的肝脏实质相比，miR-185在人肝细胞癌组织中的表达减少；定量RT-PCR显示，和原代肝细胞相比，miR-185在人肝细胞癌细胞中的表达下降；在体外人肝细胞癌细胞中miR-185的过表达会抑制细胞的增殖和侵袭，并且阻止SCID小鼠体内肿瘤的生长。miR-185的过表达能够抑制肝细胞癌细胞中DNMT1 3’端非翻译区域荧光素酶的活性，当miR-185结合位点发生突变时，就不存在此效应；miR-185的复制或过表达会减少肝细胞癌细胞中DNMT1蛋白的表达。这些结果表明DNMT1是miR-185在肝细胞癌细胞中的靶向作用蛋白。DNMT1在miR-185诱导抑制肝细胞癌的增殖中所起的作用，可进一步通过DNMT1的过表达阻止miR-185诱导抑制肝细胞癌细胞的增殖和侵袭这一事实所证实。miR-185的复制或过表达能够减少PTEN启动子DNA甲基化并且提高PTEN的表达，从而抑制Akt 磷酸化；如果DNMT1过表达，这些效应刚好相反。以上结果表明：miR-185靶向作用于DNMT1，通过诱导PTEN和抑制Akt，从而抑制肝细胞癌细胞的增殖，活化或激活miR-185可能成为肝细胞癌新的治疗策略之一。 Am J Pathol. 2014, 184(8): 1 -10.

miRNAs have recently been implicated in hepatocarcinogenesis, although the actions and mechanisms of individual miRNAs remain incompletely understood. We examined the biological functions and molecular mechanisms of miR-185 in hepatocellular carcinoma (HCC). The expression of miR-185 is decreased in human HCC tissues compared with the nonneoplastic liver parenchyma. Quantitative RT-PCR showed a reduction of miR-185 in human HCC cells compared with primary hepatocytes. miR-185 overexpression in human HCC cells inhibited cell proliferation and invasion in vitro and prevented tumor growth in SCID mice. miR-185 overexpression inhibited DNMT1 3 0 untranslated region luciferase re-porter activity in HCC cells; this effect was abolished when the miR-185 binding site was mutated. miR-185 mimic or overexpression decreased the level of DNMT1 protein in HCC cells. Thesefindings establish DN MT1 a s a bona fide targe t of mi R- 185 i n HCC c ells . T he role of DNMT1 in m iR-185 e induced inhibition of H CC g row th w as furth er s upported by the f act t h at D NMT1 overexpres si on prevented mi R-185e inducedi nh ibiti on of HCC ce ll proli feration/nv as io n. m iR -18 5 m imi c or ov erexpres si on reduced PTEN prom ot er DNA methylation and enhanced PTEN expression, leading to the inhibition of Akt phosphorylation; these effects were partially reversed by DNMT1 overexpression. These results provide novel evidence that miR-185 in-h ibits HC C ce ll g rowth by t a rgeti ng DNMT1, leadin g t o P TEN in duc tion a nd A kt in hibi tion. T hus , reacti vation or i nduc tion o f mi R-185 may r epres ent a novel thera peutic str at egy f or HCC t reatm ent. (Am J Pa th ol 2014,184: 1 e10; http ://dx.do i. org/10 .1016/j .a jpa th .2014.05.00 4 )