TGF-β upregulates miR-181a expression to promote breast cancer metastasis
Molly A. Taylor, … , David Danielpour, William P. Schiemann
Molly A. Taylor, … , David Danielpour, William P. Schiemann
Published December 17, 2012
Citation Information: J Clin Invest. 2013;123(1):150-163. https://doi.org/10.1172/JCI64946.
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Research Article Oncology

TGF-β upregulates miR-181a expression to promote breast cancer metastasis

Abstract

Late-stage breast cancer metastasis is driven by dysregulated TGF-β signaling, but the underlying molecular mechanisms have not been fully elucidated. We attempted to recapitulate tumor and metastatic microenvironments via the use of biomechanically compliant or rigid 3D organotypic cultures and combined them with global microRNA (miR) profiling analyses to identify miRs that were upregulated in metastatic breast cancer cells by TGF-β. Here we establish miR-181a as a TGF-β–regulated “metastamir” that enhanced the metastatic potential of breast cancers by promoting epithelial-mesenchymal transition, migratory, and invasive phenotypes. Mechanistically, inactivation of miR-181a elevated the expression of the proapoptotic molecule Bim, which sensitized metastatic cells to anoikis. Along these lines, miR-181a expression was essential in driving pulmonary micrometastatic outgrowth and enhancing the lethality of late-stage mammary tumors in mice. Finally, miR-181a expression was dramatically and selectively upregulated in metastatic breast tumors, particularly triple-negative breast cancers, and was highly predictive for decreased overall survival in human breast cancer patients. Collectively, our findings strongly implicate miR-181a as a predictive biomarker for breast cancer metastasis and patient survival, and consequently, as a potential therapeutic target in metastatic breast cancer.

Authors

Molly A. Taylor, Khalid Sossey-Alaoui, Cheryl L. Thompson, David Danielpour, William P. Schiemann

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Figure 2

Inhibition of miR-181a attenuates TGF-β–mediated EMT in normal MECs.

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Inhibition of miR-181a attenuates TGF-β–mediated EMT in normal MECs. (A)...
(A) NMuMG cells were stimulated to undergo EMT with TGF-β1 (5 ng/ml), which upregulated miR-181a expression as determined by semiquantitative real-time PCR, where individual miR signals were normalized to U6. Data are the mean ± SEM fold expression relative to basal cells. n = 3. *P < 0.05, Student’s t test. (B and C) Transient transfection of miR-181a Mimics (B) or Hairpin inhibitors (C) resulted in elevated or diminished miR-181a expression in NMuMG cells. Data are the mean ± SEM fold expression relative to corresponding controls. n = 3. *P < 0.05, Student’s t test. (D–F) miR-181a expression levels were manipulated in NMuMG cells as above and subsequently stimulated with TGF-β1 (5 ng/ml) for 48 hours to induce an EMT program, which was monitored by phalloidin staining to visual alterations in the actin cytoskeleton (D) or by immunoblotting to monitor E-cadherin expression (E and F). Inactivation of miR-181a (Anti miR-181a) blunted TGF-β stimulation of EMT programs in NMuMG cells. Original magnification, ×20; insets, ×10 magnification of the original. All are representative findings observed in 3 independent experiments.