G3BP1 knockdown sensitizes the acute myeloid leukemia cell line HL60 to venetoclax by inducing apoptosis

Background: G3BP1 is an RNA-binding protein that acts as the primary nucleation factor for the assembly of stress granules (SG). Its functions are central to the cellular stress response, survival, and fate decisions. G3BP1 is located on the long arm of chromosome 5 and deletion of this region is a recognized poor prognostic factor in acute myeloid leukemia. Given that G3BP1 is highly expressed in hematopoietic stem cells and functions to stabilize p53, its deficiency is hypothesized to be implicated in the tumorigenesis and therapeutic resistance of leukemic cells. Methods: To investigate the role of G3BP1, a G3BP1 knockdown cell line was generated by introducing shRNA into the HL60 AML cell line. We performed analyses of expression changes and drug sensitivity, using cell lines in which the expression level was reduced to 15% by knockdown . Results: Expression profiling via RNA sequencing demonstrated an upregulation of WT1, SAMD9L, and BCL2 expression in HL60/shG3BP1 cells (G3BP1-knockdown cells). Confirmation by Western blot analysis revealed increased protein levels of WT1 and SAMD9L. We also observed upregulation of both mTOR and its phosphorylated mTOR. HL60/shG3BP1 cells exhibited reduced sensitivity to Ara-C compared to control cells (IC50 value: 7 µM, 0.5 µM, respectively), while conversely demonstrating increased sensitivity to venetoclax (IC50 value: 4nM, 900nM, respectively). Sensitivity to other tested agents, including daunorubicin, etoposide, and Decitabine, remained unchanged. In HL60/shG3BP1 cells, venetoclax treatment led to an increased induction of apoptosis, which was accompanied by an increase in cleaved caspase-3 levels. Conclusion: Knockdown of G3BP1 in HL60 cells resulted in enhanced sensitivity to venetoclax. This enhanced sensitivity might be explained by the impairment of G3BP1-mediated SG formation.