Abstract P6-16-01: The microRNA miR-141 is a key regulator of brain metastasis from breast cancer

Purpose: Brain metastasis poses a major treatment challenge and remains an unmet clinical need. Finding novel therapies to prevent and treat brain metastases requires an understanding of the biology and molecular basis of the process, which currently is constrained by a dearth of experimental models and specific therapeutic targets. The purpose of this study was to develop preclinical models and identify molecular mediators of brain metastasis from breast cancer. Methods: We used MDA-MB-IBC3 (ER-/HER2+), SUM149 (ER-/HER2-), MCF7 (ER+/HER2-), SUM159 (ER-/HER2-) and MDA-MB-231 (ER-/HER2-) cell lines for this study. GFP-labeled cells were injected via tail vein into SCID/beige mice and metastatic colonization to the brain and lung evaluated by fluorescent stereomicroscope and histology 8-weeks after injection. miRNA microarray was performed with miRNA 3.0 Array. Stable knockdown of miR-141 was achieved with the lentiviral miRZip system. MiR-141 serum levels in 105 breast cancer patients were measured using quantitative PCR. Results: We developed novel brain metastasis models in which tail-vein injection of both triple-negative and a HER2-overexpressing inflammatory breast cancer lines led to a high rate of brain metastases (67%) in SCID/Beige mice (SUM149, 6 of 9 mice; MDA-MB-IBC3, 10 of 15 mice). Sub-lines derived from lung or brain metastases in these models were morphologically and molecularly distinct. The brain metastasis-derived sublines showed epithelial morphology and overexpressed epithelial markers and miR-141 while sublines from lung metastases showed mesenchymal morphology and overexpressed mesenchymal markers. Knockdown of miR-141 significantly inhibited metastatic colonization to the brain compared to controls (miR-141 knockdown vs. control: SUM149, 0 of 8 mice vs. 6 of 9 mice, p=0.009; MDA-MB-IBC3, 2 of 14 mice vs. 10 of 15 mice, p=0.007) but it did not affect colonization to the lung. Importantly, ectopic expression of miR-141 in non-expressing MDA-MB-231 significantly enhanced brain metastatic colonization (5 of 9 mice vs. 0 of 10 mice, P=0.02). On multivariate analyses high serum level of miR-141 was an independent predictor of progression free survival [HR 4.8 (95%CI, 2.6-8.7), P Conclusion: We demonstrated high rates of brain metastases from a heterogeneous group of cell lines that have not previously been associated with brain metastases, demonstrated miR-141 as a key regulator of brain metastasis and provided clinical evidence supporting the prognostic relevance of miR-141. We propose that miR-141 should be examined as a biomarker and potential target in the prevention and treatment of brain metastases from breast cancer. Citation Format: Bisrat G Debeb, Lara Lacerda, Simone Anfossi, Parmeswaran Diagaradjane, Khoi Chu, Lei Huo, Caimiao Wei, Richard A Larson, Adam R Wolfe, Wei Xu, Daniel L Smith, Li Li, Cristina Ivan, Pamela K Allen, Xiang H Zhang, George A Calin, Savitri Krishnamurthy, Naoto T Ueno, Thomas A Buchholz, James M Reuben, Wendy A Woodward. The microRNA miR-141 is a key regulator of brain metastasis from breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-16-01.