Synergistic Targeting of DNA-PK and KIT Signaling Pathways in KIT Mutant Acute Myeloid Leukemia

by Selleckchem | Aug 12 2023

Acute myeloid leukemia (AML) is the most common and aggressive form of acute leukemia, with a 5-year survival rate of just 24%. Over a third of all AML patients harbor activating mutations in kinases, such as the receptor tyrosine kinases FLT3 (receptor-type tyrosine-protein kinase FLT3) and KIT (mast/stem cell growth factor receptor kit). FLT3 and KIT mutations are associated with poor clinical outcomes and lower remission rates in response to standard-of-care chemotherapy. We have recently identified that the core kinase of the non-homologous end joining DNA repair pathway, DNA-PK (DNA-dependent protein kinase), is activated downstream of FLT3; and targeting DNA-PK sensitized FLT3-mutant AML cells to standard-of-care therapies. Herein, we investigated DNA-PK as a possible therapeutic vulnerability in KIT mutant AML, using isogenic FDC-P1 mouse myeloid progenitor cell lines transduced with oncogenic mutant KIT (V560G and D816V) or vector control. Targeted quantitative phosphoproteomic profiling identified phosphorylation of DNA-PK in the T2599/T2605/S2608/S2610 cluster in KIT mutant cells, indicative of DNA-PK activation. Accordingly, proliferation assays revealed that KIT mutant FDC-P1 cells were more sensitive to the DNA-PK inhibitors M3814 or NU7441, compared with empty vector controls. DNA-PK inhibition combined with inhibition of KIT signaling using the kinase inhibitors dasatinib or ibrutinib, or the protein phosphatase 2A activators FTY720 or AAL(S), led to synergistic cell death. Global phosphoproteomic analysis of KIT-D816V cells revealed that dasatinib and M3814 single-agent treatments inhibited extracellular signal-regulated kinase and AKT (RAC-alpha serine/threonine-protein kinase)/MTOR (serine/threonine-protein kinase mTOR) activity, with greater inhibition of both pathways when used in combination. Combined dasatinib and M3814 treatment also synergistically inhibited phosphorylation of the transcriptional regulators MYC and MYB. This study provides insight into the oncogenic pathways regulated by DNA-PK beyond its canonical role in DNA repair and demonstrates that DNA-PK is a promising therapeutic target for KIT mutant cancers.

Comments:

The provided information describes a research study that investigated the role of DNA-PK (DNA-dependent protein kinase) as a therapeutic target in acute myeloid leukemia (AML) with KIT mutations. AML is a type of leukemia characterized by the rapid growth of abnormal myeloid cells in the bone marrow. Activating mutations in kinases like FLT3 and KIT are found in a significant proportion of AML patients and are associated with poor clinical outcomes.

The study focused on the activation of DNA-PK downstream of FLT3 and aimed to determine if DNA-PK could be targeted in AML with KIT mutations. The researchers used isogenic mouse myeloid progenitor cell lines expressing oncogenic mutant KIT (V560G and D816V) or a control vector. They performed targeted phosphoproteomic profiling and identified phosphorylation of DNA-PK at specific sites in the KIT mutant cells, indicating activation of DNA-PK.

To assess the therapeutic potential of DNA-PK inhibition, the researchers conducted proliferation assays using DNA-PK inhibitors (M3814 or NU7441) in the KIT mutant cells. They found that the KIT mutant cells were more sensitive to DNA-PK inhibitors compared to the control cells expressing the vector alone. Additionally, they investigated the combination of DNA-PK inhibition with inhibitors targeting KIT signaling (dasatinib or ibrutinib) or protein phosphatase 2A activators (FTY720 or AAL(S)). The combined treatments resulted in synergistic cell death, indicating enhanced therapeutic efficacy.

Phosphoproteomic analysis of KIT-D816V cells treated with dasatinib and M3814 revealed inhibition of extracellular signal-regulated kinase (ERK) and AKT/MTOR pathways. The combination treatment showed greater inhibition of these pathways compared to single-agent treatments. Furthermore, the combined treatment led to synergistic inhibition of phosphorylation of the transcriptional regulators MYC and MYB, which play important roles in cancer development.

Overall, this study suggests that DNA-PK, beyond its traditional role in DNA repair, is a promising therapeutic target for AML with KIT mutations. Inhibition of DNA-PK, in combination with inhibitors targeting KIT signaling, showed synergistic effects and inhibited key oncogenic pathways involved in AML development. These findings provide insights into potential treatment strategies for KIT mutant cancers and highlight the importance of further investigating the therapeutic potential of DNA-PK inhibition in AML.