Abstract 945: Gab2 deficiency protects against Flt3-ITD driven acute myeloid leukemia in vivo

Abstract

Abstract Internal tandem duplications (ITD) of the FMS-like tyrosine kinase 3 (FLT3) frequently co-exist with inactivating DNMT3A mutations and predict poor prognosis in acute myeloid leukemia (AML). In vitro studies implicated the docking protein Grb2-associated binder 2 (GAB2) as FLT3-ITD effector. By utilizing a Flt3-ITD knock-in, Dnmt3a haploinsufficient mouse model, we demonstrate that Gab2 is essential for the development of Flt3-ITD driven AML in vivo, as Gab2 deficient mice survived significantly longer, had reduced blast counts and exhibited an attenuated spleen and liver pathology as compared to their Gab2-proficient littermates. Further, leukemic bone marrow isolated from Gab2 deficient mice displayed a reduced colony forming unit capacity and an increased sensitivity towards the Flt3 inhibitor quizartinib. Using RNA sequencing, we identify the genes encoding for Axl and the Ret co-receptor Gfra2 as targets of the Flt3-ITD/Gab2/Stat5 axis. We propose a pathomechanism in which Gab2 increases signaling of these receptors as it induces their expression and additionally serves as a downstream effector. Consequently, Gab2 promotes AML aggressiveness as well as drug resistance by incorporating the receptor tyrosine kinases Axl and Ret into the Flt3-ITD signaling network. Therefore, our data identify GAB2 as a promising biomarker as well as a therapeutic target in human AML. Citation Format: Corinna Spohr, Teresa Poggio, Geoffroy Andrieux, Katharina Schönberger, Nina Cabezas-Wallscheid, Melanie Börries, Sebastian Halbach, Anna L. Illert, Tilman Brummer. Gab2 deficiency protects against Flt3-ITD driven acute myeloid leukemia in vivo [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 945.