MicroRNA21 targets tumor suppressor genes in invasion

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MicroRNA-21 targets tumor suppressor genes in
invasion and metastasis Shuomin Zhu1, Hailong
Wu1, Fangting Wu1, Daotai Nie1, Shijie Sheng2,
Yin-Yuan Mo1 1Department of Medical Microbiology,
Immunology and Cell Biology, Southern Illinois
University School of Medicine, 825 N.
Rutledge, PO Box 19626, Springfield, IL 62794,
USA 2Department of Pathology, The Proteases and
Cancer Program, Karmanos Cancer Institute, Wayne
State University School of Medicine, Detroit, MI
48202, USA
Cell Research (2008) 18350-359.
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MicroRNA

• Small non-coding RNA
• Approximately 22 nucleotides
• Repress translation or cause mRNA degradation
• Target a cluster of genes (1 miRNA may target
  more than 100 genes)

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MicroRNA processing pathway
http//www.ambion.com/figs/f01266.gif
MicroRNAs can function as tumor suppressors or
oncogenes, depending on whether they target
oncogenes or tumor suppressor genes. Tumor
suppressor microRNA is usually downregulated in
human tumors, whereas oncogenic microRNA are
overexpressed.
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Searchable databases available to search for
microRNA targets

• MirBase- microrna.sanger.ac.uk
• Miranda- microrna.org
• TargetScan- targetscan.org
• PicTar- pictar.bio.nyu.edu

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microrna.sanger.ac.uk
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Experimental Goals

• Analyze the post-transcriptional miRNA regulation
  of tumor suppressor genes TPM1,PDCD4, and maspin
  and the effect on invasion and metastasis in
  MDA-MB-231 breast cancer cell line.

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MDA-MB-231 cells express a high level of mature
mir-21, which can be suppressed by anti-mir-21
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Effect of anti-mir-21 on MDA-MB-231 cell growth
in vitro and in vivo
MTT
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In vitro cell invasion is suppressed by
anti-mir-21
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Anti-mir-21 suppresses tumor metastasis in vivo

• These data suggest that mir-21 plays an important
  role in cell metastasis.
• A genetic screening identified TPM1, PDCD4, and
  maspin as candidate targets for mir-21

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Mir-21 targets

• Tropomyosin1 (TPM1) is an actin-binding protein
  and functions to stabilize microfilaments. TPM1
  overexpression suppresses cell invasion.
• Programmed cell death 4 (PDCD4) is a tumor
  suppressor protein which interacts with EIF4A and
  inhibits protein synthesis.
• Maspin is a member of the serpin family of
  proteases and has tumor-suppressive activity.
  Maspin is downregulated in mammary carcinoma.

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Exogenous overexpression of TPM1, PDCD4 or Maspin
suppresses cell invasion

• These results suggest that mir-21 affects cell
  invasion and metastasis by regulating multiple
  target genes.

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PDCD4 and maspin are direct mir-21 targets
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Breast tumors have lower levels of PDCD4 and
Maspin than normal breast tissue

• There is an inverse correlation between PDCD4
  protein and mir-21 in breast tumors.

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Conclusions

• Mir-21 directly interacts with and
  post-transcriptionally regulates PDCD4, and
  maspin.
• Inhibition of mir-21 suppresses invasion and
  metastasis in MDA-MB-231 cells.
• There is an inverse correlation between the
  expression of PDCD4 and mir-21 in breast tumor
  samples.
• Mir-21 may promote tumor invasion and metastasis
  by simultaneously downregulating multiple
  metastasis-related tumor suppressor genes.