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 3

The mesenchymal phenotype of cancer cell lines is associated with the IL-6R/STAT3/miR-34a loop.

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The mesenchymal phenotype of cancer cell lines is associated with the IL...
(A) Expression of the indicated proteins and primary miRNAs in CRC, breast cancer (BC), and prostate cancer (PCa) cell lines exhibiting epithelial (E) or mesenchymal (M) phenotypes was determined by Western blot (upper panel) and qPCR analysis (lower panel). Relative densitometric quantifications of m–IL-6R protein normalized to α-tubulin are indicated. (B) Detection of protein and RNA expression 48 hours after transfection with the indicated siRNAs. (C, D, and E) Expression of miR-34a (C), invasion (D), and expression of indicated proteins (E) in SW480 cells transfected with control or pre–miR-34a oligonucleotides for 48 hours. (F) Relative invasion of SW620-luc2 cells transfected with STAT3- or IL-6R–specific siRNAs and miR-34a–specific antagomirs. (G) qPCR analysis of mature miR-34a in cells treated as in F. (H and I) SW620-luc2 cells were transfected with control, STAT3-, or IL-6R–specific siRNAs for 48 hours, subsequently injected into the tail vein of NOD/SCID mice, and followed by noninvasive bioluminescence imaging for 9 weeks. In H, the left panels show representative images and the graph shows the photon flux (right). Quantification of metastatic tumor nodules in the lung per mouse 9 weeks after tail-vein injection are shown (I). Mean values ± SD (n = 3) are provided. *P < 0.05; **P < 0.01; ***P < 0.001.