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 3

Inhibition of miR-181a attenuates TGF-β–mediated EMT, invasion, and migration.

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Inhibition of miR-181a attenuates TGF-β–mediated EMT, invasion, and migr...
(A and B) An antagomir against miR-181a (anti–miR-181a) was transiently transfected into 67NR or 4T1 cells, resulting in decreased expression of miR-181a, as determined by semiquantitative real-time PCR. (C and D) The invasiveness of miR-181a–manipulated 67NR and 4T1 cells in response to TGF-β1 (5 ng/ml) treatment was significantly reduced by miR-181a inactivation. (E and F) The proliferation of miR-181a–manipulated 67NR and 4T1 cells in response to TGF-β1 (5 ng/ml) treatment was unaffected by miR-181a inactivation. (G and H) 4T1 cells engineered to stably express miR-181a (G) or a miR-181a sponge (H) were transiently transfected with a renilla luciferase miR-181a biosensor and CMV–β-gal, which was used to control for differences in transfection efficiency. miR-181a was shown to significantly elevate miR-181a activity, while miR-181a antagonists were shown to significantly reduce miR-181a activity. (I and J) The ability of TGF-β1 (5 ng/ml) to induce the migration of 4T1 cells with elevated (I) or reduced (J) miR-181a activity was significantly stimulated by miR-181a activation (I) or was significantly inhibited by miR-181a inactivation (J). Original magnification, ×20. All data are the mean ± SEM. n = 3. *P < 0.05, Student’s t test.