Abstract 87: The role of miro1-mediated mitochondrial positioning in the development and metastasis of breast cancer

Abstract Miro1 is an outer mitochondrial membrane protein that links mitochondria to motor protein complexes to support subcellular mitochondrial trafficking. Preliminary observations and published work has established that metastatic breast cancer cells have increased expression of Miro1 in comparison to breast cancer cells with low metastatic potential. Furthermore, tumors from breast cancer patients with high Miro1 expression have poorer survival rates compared to patients harboring tumors with low Miro1 expression. This data suggests that Miro1 has a functional role in aggressive breast cancers although this has not been widely studied or confirmed in advanced preclinical models. The objective of our research is to investigate the role of Miro1 in breast cancer tumorigenesis and metastasis. We hypothesize that that Miro1-mediated mitochondrial dynamics support subcellular signaling events driving cell migration, invasion, and tumorigenesis. To examine the function of Miro1 in promoting metastatic phenotypes in vitro, we generated human breast cancer cell lines (MDA-MB-231, MDA-MB-468, T-47d, and MCF7) with Miro1 knockdown using adenoviral shRNA. Knockdown of Miro1 to levels greater than 50% of that in control cells resulted in mitochondria sequestered around the nucleus and reduced cell migration. Additionally, MDA-MB-231 cells with ≥50% Miro1 knockdown resulted in a significant decrease in cell invasion through Matrigel coated membranes in transwell invasion assays. Our research has also uncovered altered phosphorylation of key cell migration and stress-response proteins including vinculin, focal adhesion kinase and ERK ½ when Miro1 is knocked down. To investigate the role of Miro1 in vivo, we generated a novel transgenic mouse model with inducible, tissue specific Miro1 deletion in mammary epithelial cells with concurrent polyomavirus middle T-antigen oncogene activation. We found that when breast cancer formation is induced utilizing the transgenic middle-T antigen system, our control mice form tumors at all mammary gland sites and have metastasis to the lungs. Conversely, mice with concurrent Miro1 deletion and middle T- antigen activation fail to develop tumors. This data suggests that Miro1 has a functional role in both mammary tumor onset and tumor cell migration and invasion, providing a possible new biomarker of tumor status and pathway for therapeutic intervention. Citation Format: Randi Gravelle, Margaret McCoy, Nathaniel Shannon, Martin Chang, Brian Cunniff. The role of miro1-mediated mitochondrial positioning in the development and metastasis of breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 87.