Upregulation of miR-23a∼27a∼24 decreases transforming growth factor-beta-induced tumor-suppressive activities in human hepatocellular carcinoma cells

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Transforming growth factor-beta (TGF-beta) plays a dual and complex role in human cancer. In this report, we observe a specific set of MicroRNAs (miRNAs) changed in response to TGF-beta in human hepatocellular carcinoma (HCC) cells by miRNA microarray screening. A cluster of miRNA, miR-23a∼27a∼24, is induced in an early stage by TGF-beta in Huh-7 cells. Knockdown of Smad4, Smad2 or Smad3 expression by RNA interference can attenuate the response of miR-23a∼27a∼24 to TGF-beta addition, indicating that this induction is dependent on Smad pathway. We also explore that miR-23a∼27a∼24 can function as an antiapoptotic and proliferation-promoting factor in liver cancer cells. In addition, expression of this miRNA cluster is found to be remarkably upregulated in HCC tissuesversusnormal liver tissues. These findings suggest a novel, alternative mechanism through which TGF-beta could induce specific miRNA expression to escape from tumor-suppressive response in HCC cells. © 2008 Wiley-Liss, Inc.

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