Abstract A55: A novel mediator of brain metastasis from breast cancer

Abstracts: AACR Special Conference on Tumor Metastasis; November 30-December 3, 2015; Austin, TX 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 identify molecular mediators of brain metastasis from breast cancer using novel preclinical brain metastasis models we developed recently. Methods: GFP-labeled cells were injected via tail vein into SCID/beige mice and metastatic colonization to the brain and lung was evaluated by fluorescent stereomicroscope and histology 8-weeks after injection. miRNA microarray was performed with miRNA 3.0 Array. Stable knockdown and overexpression of miR-141 was achieved with lentiviral vectors. miR-141 serum levels in patients with metastatic breast cancer was measured using quantitative PCR and was associated with outcome data. Results: We developed novel brain metastasis models in which tail-vein injection of parental 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 brain metastases (BrMS) or lung metastases (LuMS) tissues were morphologically and molecularly distinct. The BrMS showed epithelial morphology and overexpressed epithelial markers and miR-141 while the LuMS showed mesenchymal morphology and overexpressed mesenchymal markers. Knockdown of miR-141 significantly inhibited metastatic colonization to the brain compared to parental controls in both cell lines (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). Further, ectopic expression of miR-141 in non-expressing MDA-MB-231 significantly enhanced brain metastatic colonization via tail-vein injection (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<0.001] and overall survival [HR 7.0 (95%CI 3.5-15.1), P<0.001] in patients with metastatic breast cancer. Importantly, it is associated with shorter brain metastasis free survival (P=0.03). Conclusion: We have generated novel brain metastasis models that can be utilized to develop therapies. Further, we demonstrated miR-141 as a key regulator of brain metastasis and provided clinical evidence supporting the prognostic relevance of miR-141 in patients with brain metastasis. Our work could lead to novel targets for the prevention and treatment of brain metastasis that could improve patient survival in addition to fundamentally advancing the field of brain metastasis research. We propose that miR-141 should be examined as a biomarker and potential target to prevent or treat brain metastases. Citation Format: Bisrat G. Debeb, Lara Lacerda, Simone Anfossi, Parmeswaran Diagaradjane, Richard Larson, Khoi Chu, Lei Huo, Daniel Smith, Li Li, Cristina Ivan, Pamela Allen, Xiang Zhang, George Calin, Savitri Krishanmurthy, Thomas Buchholz, Naoto Ueno, James Reuben, Wendy A. Woodward. A novel mediator of brain metastasis from breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr A55.