Functional role of fatty acid synthase for signal transduction in Core binding factor-AML with activating c-Kit mutation

Background AML is a rare hematological malignancy still associated with poor prognosis. 5% of de novo AML and 30% of core binding factor (CBF) AML (translocation t(8;21)(q22;q22) or invasion (16)(p13;q22)), respectively, harbor activating c-Kit (CD117) mutations leading to an adverse clinical outcome. Posttranslational protein modifications, especially by myristolic and palmitic acid, are known to be important for diverse cell functions such as membrane organization, transduction signaling or regulation of apoptosis. However, most data come from solid tumor studies while its role in AML is still poorly understood. Fatty acid synthase (FASN) is one of the key palmitoyl-acyltransferases which controls subcellular localization, trafficking and degradation of various target proteins. H-Ras, N-Ras or FLT3-ITDmut receptors are known to be important target proteins for FASN in AML. Methods In this study, we investigated the role of FASN in two c-Kit-N822K mutated AML cell lines. Using FASN knockdown via shRNA and the FASN inhibitor TVB-3166. Functional implications including cell viability and proliferation were tracked in a combined approach integrating western blotting, mass spectrometry PamGene. Results In FASN-knockdown cells, we observed an increase in phosphorylation of c-Kit (p-c-Kit), Lyn kinase (pLyn) as well as of S6 kinase (pS6). Moreover, a downregulation of cathepsin Z (CTSZ), which belongs to endo-lysosomal proteases and is hence essential for degradation of cellular proteins within lysosomes was found. Conclusion Recent studies have suggested potential roles for palmitoylation in lysosomal function indirectly through its effects on proteins involved in lysosomal trafficking, membrane fusion, and signaling pathways. Therefore, our observation of the reduced expression of CTSZ due to the inhibition of FASN offers an explanation for the increased c-Kit, Lyn, and S6 kinase activity in CBF-AML with activating c-Kit mutation.