Abstract 2984: ARHGAP17, a Cdc42-specific GAP, localizes to invadopodia and regulates their turnover as part of an ARHGAP17/Cdc42/CIP4 complex

Abstract One of the hallmarks of aggressive cancer is its ability to invade into surrounding tissues and metastasize. Many invasive cancers form invadopodia, which are protrusive, degradative structures that are regulated by the Rho family of GTPases. Rho GTPases commonly have aberrant activity in invasive cancers caused by changes in their upstream regulators: RhoGEFs and RhoGAPs. We have identified the RhoGAP ARHGAP17 (RICH1/NADRIN) as a negative regulator of invadopodia in triple negative breast cancer. Using confocal and STORM super-resolution microscopy techniques, we show that ARHGAP17 localizes to the regulatory ring surrounding invadopodia where it acts to promote disassembly by decreasing invadopodia lifetime through the inactivation of the Rho GTPase Cdc42. We further support these results in live cells by using a new localization-based Cdc42 biosensor, which reveals that ARHGAP17 suppresses Cdc42 activity specifically at the invadopodia ring. We have also identified the Cdc42 effector CIP4 as part of a complex with ARHGAP17 and Cdc42 that we propose is key in the regulation of invadopodia. Finally, using spheroid and inverse invasion assays, we show that the invadopodia phenotype correlates with increased invasive properties. In conclusion, we have identified ARHGAP17 as a key regulator of invadopodia and invasion in triple negative breast cancer by localizing to invadopodia and inactivating Cdc42 as part of a complex with CIP4. In future studies, we will further characterize the molecular mechanisms that regulate the ARHGAP17/Cdc42/CIP4 complex and their function during invadopodia formation. Citation Format: Gabriel Kreider-Letterman, Abel Castillo, Agustin Rabino, Eike K. Mahlandt, Joachim Goedhart, Silvia Goicoechea, Rafael Garcia-Mata. ARHGAP17, a Cdc42-specific GAP, localizes to invadopodia and regulates their turnover as part of an ARHGAP17/Cdc42/CIP4 complex [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2984.