NPM1-Mutated Patient-Derived AML Cells Are More Vulnerable to Rac1 Inhibition

Abstract

The prognosis of acute myeloid leukemia (AML) is poor, especially for the elderly population. Targeted therapy with small molecules may be a potential strategy to overcome chemoresistance and improve survival in AML. We investigated the inhibition of the signaling molecule ras-related C3 botulinum toxin substrate 1 (Rac1) in leukemia cells derived from 79 consecutive AML patients, using five Rac1 inhibitors: ZINC69391, ITX3, EHOP-016, 1A-116, and NSC23766. In vitro cell proliferation and apoptosis assays and the assessment of cytokine profiles in culture media were conducted. All five inhibitors had an antiproliferative effect; IC50 ranged from 3–24 µM. They induced significant apoptosis and necrosis compared to the untreated controls (p < 0.0001) at concentrations around IC40 and IC80. A high versus an intermediate or low antiproliferative effect was more common in NPM1-mutated (p = 0.002) and CD34-negative (p = 0.008) samples, and when NPM1 and FLT3 (p = 0.027) were combined. Presence of NPM1 mutation was associated with reduced viability after treatment with EHOP-016 (p = 0.014), ITX3 (p = 0.047), and NSC23766 (p = 0.003). Several cytokines crucial for leukemogenesis were reduced after culture, with the strongest effects observed for 1A-116 and NSC23766. Our findings suggest potent effects of Rac1 inhibition in primary AML cells and, interestingly, samples harboring NPM1 mutation seem more vulnerable.