MicroRNA-21 promotes cell transformation by targeting the programmed cell death 4 gene

Z. Lu, M. Liu, V. Stribinskis, C. M. Klinge, K. S. Ramos, N. H. Colburn, Y. Li

Research output: Contribution to journalArticlepeer-review

651 Scopus citations


MicroRNAs (miRNAs) are small noncoding RNA molecules that negatively control expression of target genes in animals and plants. The microRNA-21 gene (mir-21) has been identified as the only miRNA commonly overexpressed in solid tumors of the lung, breast, stomach, prostate, colon, brain, head and neck, esophagus and pancreas. We initiated a screen to identify miR-21 target genes using a reporter assay and identified a potential miR-21 target in the 3′-UTR of the programmed cell death 4 (PDCD4) gene. We cloned the full-length 3′-UTR of human PDCD4 downstream of a reporter and found that mir-21 downregulated, whereas a modified antisense RNA to miR-21 upregulated reporter activity. Moreover, deletion of the putative miR-21-binding site (miRNA regulatory element, MRE) from the 3′-UTR of PDCD4, or mutations in the MRE abolished the ability of miR-21 to inhibit reporter activity, indicating that this MRE is a critical regulatory region. Western blotting showed that Pdcd4 protein levels were reduced by miR-21 in human and mouse cells, whereas quantitative real-time PCR revealed little difference at the mRNA level, suggesting translational regulation. Finally, overexpression of mir-21 in MCF-7 human breast cancer cells and mouse epidermal JB6 cells promoted soft agar colony formation by downregulating Pdcd4 protein levels. The demonstration that miR-21 promotes cell transformation supports the concept that mir-21 functions as an oncogene by a mechanism that involves translational repression of the tumor suppressor Pdcd4.

Original languageEnglish (US)
Pages (from-to)4373-4379
Number of pages7
Issue number31
StatePublished - Jul 17 2008


  • Cell transformation
  • MicroRNA
  • PDCD4
  • Tumor suppressor
  • miR-21

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cancer Research


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