Hsa-let-7g inhibits proliferation of hepatocellular carcinoma cells by downregulation of c-Myc and upregulation of p16INK4A
Hsa-let-7g inhibits proliferation of hepatocellular carcinoma cells by downregulation of c-Myc and upregulation of p16INK4A
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DOI：
10.1002/ijc.25336
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发表时间：
2011-01-15
影响因子：
6.4
通讯作者：
Kung, Hsiang-Fu
中科院分区：
文献类型：
--
作者：
Lan, Fei-Fei;Wang, Hua;Kung, Hsiang-Fu
zMicroRNA（miRNAs）是一类内源性表达的小分子非编码RNA，在转录后水平调控约1/3的人类基因。研究表明，miRNAs参与了多种细胞过程，并参与了包括肝细胞癌（HCC）在内的多种肿瘤的发生、发展。在所有的miRNAs中，let-7家族是公认的在肿瘤发生中发挥关键作用的潜在的生长抑制剂。本研究旨在探讨let-7家族，特别是hsa-let-7 g在肝癌分子发病机制中的作用。通过MTT、qPCR、Western blotting和双向电泳分析，发现hsa-let-7 g过表达可抑制肝癌细胞系的增殖，其作用机制分别是通过对c-Myc和p16（INK 4A）的负性和正性调节。hsa-let-7 g在HepG 2、Hep 3B和Huh 7细胞中的表达显著降低，而在Bel-7404肝癌细胞系中的表达较高。hsa-let-7 g模拟物转染肝癌细胞后，肝癌细胞的增殖明显受到抑制，而hsa-let-7 g抑制剂转染则产生相反的效果。同时，转染hsa-let-7 g模拟物后，HepG 2细胞c-Myc mRNA和蛋白水平明显降低，而转染hsa-let-7 g抑制剂后，Bel-7404细胞c-Myc mRNA和蛋白水平明显升高。如2-DE所示，在使用hsa-let-7 g的功能获得性研究后，p16（INK 4A）显著上调。因此，我们认为hsa-let-7 g可能作为一种抑癌基因，通过下调癌基因c-Myc和上调抑癌基因p16（INK 4A）来抑制HCC细胞增殖。
zMicroRNAs (miRNAs) are endogenously expressed small noncoding RNAs that regulate approximately one-third of human genes at post-transcription level. Previous studies have shown that miRNAs were implicated in many cellular processes and participated in the progress of various tumors including hepatocellular carcinoma (HCC). Among all miRNAs, the let-7 family is well recognized to play pivotal roles in tumorigenesis by functioning as potential growth suppressor. In the present study, we aimed to investigate the role of let-7 family, particularly the hsa-let-7g, in the molecular pathogenesis of HCC. By use of MTT, qPCR, Western blotting and 2-dimensional electrophoresis (2-DE), over-expression of hsa-let-7g was found to inhibit the proliferation of HCC cell line via negative and positive regulations of c-Myc and p16(INK4A), respectively. The expression of hsa-let-7g was noted to be markedly lowered in the HepG2, Hep3B and Huh7 cells, yet higher in the Bel-7404 HCC cell line. Proliferation of HCC cell line was significantly inhibited after the transfection of hsa-let-7g mimics, while hsa-let-7g inhibitor transfection exerted an opposite effect. Concurrently, the mRNA and protein levels of c-Myc were found significantly decreased in HepG2 cells after transfection of hsa-let-7g mimics, but obviously increased in Bel-7404 cells after transfection of hsa-let-7g inhibitor. As revealed by 2-DE, a significant upregulation of p16(INK4A) was revealed after the gain-of-function study using hsa-let-7g. Therefore, we suggest that hsa-let-7g may act as a tumor suppressor gene that inhibits HCC cell proliferation by downregulating the oncogene, c-Myc, and upregulating the tumor suppressor gene, p16(INK4A).