Investigation of the therapeutic effect of a novel small molecule inhibiting ybx1 in myeloid malignancies

The cold-inducible chaperone Y-Box binding protein 1 (YBX1) is a multifunctional protein essential for stabilizing mRNA molecules and maintaining their expression. YBX1 has been associated with tumor progression and treatment resistance. Overexpression of YBX1 has been reported in a substantial number of patients affected by Acute Myeloid Leukemia (AML), suggesting that therapeutic targeting of YBX1 may be effective. Recently, azopodophyllotoxin small molecule SU056 was reported to inhibit tumor growth in ovarian cancer cells by YBX1 protein degradation. Here, we investigate the mechanisms of cytotoxicity of this compound in AML. Our preliminary data show that multiple AML cell lines exhibit a dose-dependent inhibition of cell growth with an IC50 of 500-750 nM, resulting from an increased number of apoptotic cells and G1 cell cycle arrest. We also evaluated the effect of SU056 and kinase inhibitors (Gilteritinib) in primary AML patient samples with an oncogenic mutation in FMS-like tyrosine kinase 3 (FLT3). We observed a synergistic cell death across a broad range of drug concentrations, indicating the efficacy of SU056 in combination with kinase inhibitors. In order to evaluate the MYC drug response dependency of SU056, we performed a western blot on MOLM-13 AML cell lines treated with different doses of SU056. We observe a dose-dependent reduction in MYC expression, indicating that decreased MYC protein abundance may contribute to SU056-cytotoxicity. Collectively, our data shows that SU056 drives cell death via degradation of MYC protein resulting in apoptosis and cell cycle arrest. The combination of this drug with kinase inhibitors displays a synergetic effect. Ultimately these results will provide insight into the mechanistic basis of SU056 drug response, helping us to design and implement clinical trials for patients affected by AML to investigate its efficiency The cold-inducible chaperone Y-Box binding protein 1 (YBX1) is a multifunctional protein essential for stabilizing mRNA molecules and maintaining their expression. YBX1 has been associated with tumor progression and treatment resistance. Overexpression of YBX1 has been reported in a substantial number of patients affected by Acute Myeloid Leukemia (AML), suggesting that therapeutic targeting of YBX1 may be effective. Recently, azopodophyllotoxin small molecule SU056 was reported to inhibit tumor growth in ovarian cancer cells by YBX1 protein degradation. Here, we investigate the mechanisms of cytotoxicity of this compound in AML. Our preliminary data show that multiple AML cell lines exhibit a dose-dependent inhibition of cell growth with an IC50 of 500-750 nM, resulting from an increased number of apoptotic cells and G1 cell cycle arrest. We also evaluated the effect of SU056 and kinase inhibitors (Gilteritinib) in primary AML patient samples with an oncogenic mutation in FMS-like tyrosine kinase 3 (FLT3). We observed a synergistic cell death across a broad range of drug concentrations, indicating the efficacy of SU056 in combination with kinase inhibitors. In order to evaluate the MYC drug response dependency of SU056, we performed a western blot on MOLM-13 AML cell lines treated with different doses of SU056. We observe a dose-dependent reduction in MYC expression, indicating that decreased MYC protein abundance may contribute to SU056-cytotoxicity. Collectively, our data shows that SU056 drives cell death via degradation of MYC protein resulting in apoptosis and cell cycle arrest. The combination of this drug with kinase inhibitors displays a synergetic effect. Ultimately these results will provide insight into the mechanistic basis of SU056 drug response, helping us to design and implement clinical trials for patients affected by AML to investigate its efficiency