Abstract A043: A novel role for Mitochondrial Rho GTPase 2 in tumor cell invasion and metastasis

Abstract

Abstract Metastasis of cancer cells to secondary sites remains the leading cause of cancer related deaths, emphasizing a strong need for actionable targets in advanced stage cancer. To address this, we study novel dysregulated signaling mechanisms that cells utilize to metastasize to distal sites. Here, we focus on how outer mitochondrial membrane protein—Mitochondrial Rho GTPase 2 (MIRO2)—promotes tumor cell invasion and metastasis through a negative regulation of RhoA. Our previous work identified higher MIRO2 mRNA expression in cancer vs. normal patient samples, which correlated with worse patient outcomes. Furthermore, in the context of prostate cancer we demonstrated that MIRO2 was critical for 2D cell growth, anchorage-dependent and -independent colony formation, and tumor growth in vivo. However, it remains completely unknown if MIRO2 affects primary tumor growth or if this protein is important throughout tumor progression. Using siRNA mediated knockdown (KD) of MIRO2 we clearly show that MIRO2 KD ubiquitously reduces tumor cell invasion in breast, melanoma, pancreatic, and prostate cancer cell lines. Preliminary experiments modeling late-stage metastasis showed that tail vein injection of PC3 cells stably expressing MIRO2 targeting shRNA had reduced kidney and liver metastatic burden in comparison to PC3 cells with control shRNA. In further mechanistic studies, we identified novel MIRO2 binding partners and used siRNA to KD the top hits and observe changes in invasive capacity. We found that atypical myosin IX B (MYO9B) reduced the invasion of cells to the largest extent. MYO9B is a plus-end direct atypical myosin known to control cell motility through spatially inactivating RhoA at the leading edge of migrating cells. Excitingly, MIRO2 KD showed an increase in active RhoA phenocopying MYO9B KD. Lastly, in pilot experiments we found that dual KD of MIRO2 and RhoA rescued invasive capacity in comparison to MIRO2 KD alone. Taken together, we propose a novel signaling mechanism by which MIRO2 broadly promotes invasion and metastasis through MYO9B dependent inactivation of RhoA. Citation Format: Dillon P. Boulton, Madison Furnish, M. Cecilia Caino. A novel role for Mitochondrial Rho GTPase 2 in tumor cell invasion and metastasis [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr A043.