IL-6R/STAT3/miR-34a feedback loop promotes EMT-mediated colorectal cancer invasion and metastasis
Matjaz Rokavec, … , Florian R. Greten, Heiko Hermeking
Matjaz Rokavec, … , Florian R. Greten, Heiko Hermeking
Published March 18, 2014
Citation Information: J Clin Invest. 2014;124(4):1853-1867. https://doi.org/10.1172/JCI73531.
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Research Article

IL-6R/STAT3/miR-34a feedback loop promotes EMT-mediated colorectal cancer invasion and metastasis

Abstract

Members of the miR-34 family are induced by the tumor suppressor p53 and are known to inhibit epithelial-to-mesenchymal transition (EMT) and therefore presumably suppress the early phases of metastasis. Here, we determined that exposure of human colorectal cancer (CRC) cells to the cytokine IL-6 activates the oncogenic STAT3 transcription factor, which directly represses the MIR34A gene via a conserved STAT3-binding site in the first intron. Repression of MIR34A was required for IL-6–induced EMT and invasion. Furthermore, we identified the IL-6 receptor (IL-6R), which mediates IL-6–dependent STAT3 activation, as a conserved, direct miR-34a target. The resulting IL-6R/STAT3/miR-34a feedback loop was present in primary colorectal tumors as well as CRC, breast, and prostate cancer cell lines and associated with a mesenchymal phenotype. An active IL-6R/STAT3/miR-34a loop was necessary for EMT, invasion, and metastasis of CRC cell lines and was associated with nodal and distant metastasis in CRC patient samples. p53 activation in CRC cells interfered with IL-6–induced invasion and migration via miR-34a–dependent downregulation of IL6R expression. In Mir34a-deficient mice, colitis-associated intestinal tumors displayed upregulation of p-STAT3, IL-6R, and SNAIL and progressed to invasive carcinomas, which was not observed in WT animals. Collectively, our data indicate that p53-dependent expression of miR-34a suppresses tumor progression by inhibiting a IL-6R/STAT3/miR-34a feedback loop.

Authors

Matjaz Rokavec, Meryem Gülfem Öner, Huihui Li, Rene Jackstadt, Longchang Jiang, Dmitri Lodygin, Markus Kaller, David Horst, Paul K. Ziegler, Sarah Schwitalla, Julia Slotta-Huspenina, Franz G. Bader, Florian R. Greten, Heiko Hermeking

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Figure 8

The tumors of Mir34a–/– mice show characteristics of EMT and enhanced IL-6R/STAT3 signaling.

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The tumors of Mir34a–/– mice show characteristics of EMT and enhanced IL...
(A) Expression of mature miR-34a and Stat3 in mouse rectal cancer cell line CMT93 transfected with control or STAT3 siRNA. (B and C) Immunohistochemical analysis of p-STAT3, IL-6R, and SNAIL in tumors of Mir34aF/F and Mir34a–/– mice. Yellow and green arrows indicate tumor and stromal cells, respectively. Scale bars: 50 μm; 20 μm (insets). Bar charts (C) show the percentage of positive tumor cells (index; p-STAT3 and SNAIL) or expression score (IL-6R) determined as described in Methods (n ≥10 tumors from each genotype). (D) Western blot analysis of indicated proteins in lysates prepared from tumors of Mir34aF/F and Mir34a–/– mice (n = 5 from each genotype). Relative densitometric quantifications of indicated proteins are shown in lower panel. (E) qPCR analysis of indicated mRNAs in tumors of Mir34aF/F and Mir34a–/– mice (n = 3 from each genotype). (F) Schematic representation of the proposed IL-6R/STAT3/miR-34a feedback loop and its potential involvement in cancer progression. The activation of the loop by IL-6 induces EMT and shifts the cellular phenotype toward a mesenchymal state that is advantageous for invasion, intravasation, and extravasation steps of the metastatic cascade. On the contrary, the inactivation of the loop by p53 induces MET and switches cells to an epithelial state, which allows colonization and outgrowth of metastases. Shown are mean values ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001.