Institute of Biochemistry and Molecular Biology, School of Medicine, Ningbo University, 818 Fenghua Road, Ningbo 315211, China.
Mol Cell Biochem. 2011 Sep;355(1-2):257-63. doi: 10.1007/s11010-011-0862-x. Epub 2011 May 7.
The let-7 family of microRNAs (miRNAs) are known to act as tumor suppressors and down-regulated in lung cancer. Recently, the RNA-binding protein Lin-28 was demonstrated to inhibit biogenesis of let-7 miRNAs by blocking both Drosha- and Dicer-mediated cleavage and accelerating decay of let-7 precursors. We selected NCI-H446 lung small cell lung cancer cell to determine whether it is broadly representative that Lin-28 can promote cell proliferation and affect cell cycle through negatively regulating let-7 biogenesis. Here, we showed that Lin-28 mRNA was up-regulated in NCI-H446 cell with a high c-Myc state. The result of real-time RT-PCR further indicated that pri-let-7a-1/7g and mature let-7g were remarkably down-regulated. The expression of lin-28 was down-regulated while the mature let-7g transcript was up-regulated inversely. The MTT assay indicated that the proliferation of lung cancer cells with lin-28 inhibition was signally impaired. The cells with lin-28 knockdown revealed a higher proportion of cells at G1/G0 phase and less at S phase. The results presented here demonstrate that induction of Lin-28 could mediate repression of let-7 family members, promote cell cycle progression and suppress cell proliferation.
miRNA 家族中的 let-7 被认为是抑癌基因，在肺癌中表达下调。最近，RNA 结合蛋白 Lin-28 被证明通过阻断 Drosha 和 Dicer 介导的切割以及加速 let-7 前体的降解来抑制 let-7 miRNA 的生物发生。我们选择 NCI-H446 肺小细胞肺癌细胞来确定 Lin-28 是否能够通过负调控 let-7 生物发生来广泛促进细胞增殖并影响细胞周期。在这里，我们表明 NCI-H446 细胞中 Lin-28 mRNA 呈上调状态，且 c-Myc 状态较高。实时 RT-PCR 的结果进一步表明，pri-let-7a-1/7g 和成熟的 let-7g 明显下调。Lin-28 的表达下调，而成熟的 let-7g 转录物则呈相反的上调。MTT 分析表明，Lin-28 抑制后肺癌细胞的增殖明显受损。Lin-28 敲低的细胞处于 G1/G0 期的比例更高，而处于 S 期的比例更低。这里呈现的结果表明，Lin-28 的诱导可以介导 let-7 家族成员的抑制，促进细胞周期进程并抑制细胞增殖。
