Abstract 847: Role of RHOA in diffuse gastric cancer tumors

Abstract Gastric cancer constitutes the third leading cause of cancer mortality worldwide and tumors with diffuse histology have poor prognosis and low response rates to therapy. Missense mutations in the RHOA (Ras homolog family member A) GTPase have recently been identified in 24% of patients with diffuse gastric cancer. RHOA mutations are not randomly distributed along the coding sequence, but enriched in specific and recurrent hotspots. Substitution in codon 42 (Y42C) occurs in approximately 50% of the patients in which RHOA is mutated. RHOA orchestrates cellular processes such as proliferation, differentiation, migration and invasion, whose deregulation is essential for the onset, maintenance and progression of tumors. However, the functional role of wild type RHOA and RHOA mutants remains poorly characterized in gastric cancer. We used isogenic cell lines systems and animal models to study the impact of RHOA in the gastric tumorigenesis. RHOA loss strongly increased the proliferation, migration and invasion of diffuse gastric cancer cells in vitro, but also when growing as subcutaneous xenografts in immunodeficient mice, and in experimental mouse models of peritoneal and lung metastasis. Stomach tumor burden was also increased in transgenic mice conditionally expressing a dominant negative form of RHOA in the gastrointestinal tract (RHOA T19N). Moreover, cells overexpressing wild-type RHOA or G14V RHOA (a constitutive active form of the GTPase) exhibited reduced tumorigenic features both in vitro and in vivo. Conversely, diffuse gastric cancer cells engineered for overexpressing RHOA Y42C mutant, displayed enhanced growth and invasion in vitro. Importantly, stomach cancer tumors formed more efficiently in a transgenic mouse model in which we targeted the expression of Y42C RHOA mutant to the gastric epithelium. Collectively, these results demonstrate that RHOA has tumor-suppressive activity in diffuse gastric cancer, while the recurrent Y42C hotspot RHOA mutation found in these tumors is oncogenic. Citation Format: Agueda Martinez-Barriocanal, Higinio Dopeso, Lizbeth M. Jiménez-Flores, Juliana C. Santos, Estefania Anguita, Josipa Bilic, Rocio Nieto, Elia García-Vidal, Manuel Sánchez Martín, Stefania Landolfi, Kazuto Kobayashi, Javier Hernandez-Losa, Simo Schwartz, Santiago Ramón y Cajal, Diego Arango. Role of RHOA in diffuse gastric cancer tumors [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 847.