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Combination of RSK inhibitor LJH-685 and FLT3 inhibitor FF-10101 promoted apoptosis and proliferation inhibition of AML cell lines

Purpose: FLT3 mutations occurred in approximately one third of patients with acute myeloid leukemia (AML). FLT3-ITD mutations caused the constitutive activation of the RAS/MAPK signaling pathway. Ribosomal S6 Kinases (RSKs) were serine/threonine kinases that function downstream of the Ras/Raf/MEK/ERK signaling pathway. However, roles and mechanisms of RSKs inhibitor LJH-685, and combinational effects of LJH-685 and FLT3 inhibitor FF-10101 on AML cells were till unclear.

Methods: Cell viability assay, CFSE assay, RT-qPCR, Colony formation assay, PI stain, Annexin-V/7-AAD double stain, Western blot, and Xenogeneic transplantation methods were used to used to investigate roles and mechanisms of LJH-685 in the leukemogenesis of AML.

Results: LJH-685 inhibited the proliferation and clone formation of AML cells, caused cell cycle arrest and induced the apoptosis of AML cells via inhibiting the RSK-YB-1 signaling pathway. MV4-11 and MOLM-13 cells carrying FLT3-ITD mutations were more sensitive to LJH-685 than that of other AML cell lines. Further studies suggested that LJH-685 combined with Daunorubicin or FF- 10101 synergistically inhibited the cell viability, promoted the apoptosis and caused cycle arrest of AML cells carrying FLT3-ITD mutations. Moreover, in vivo experiments also indicated that LJH-685 combined with FF-10101 or Daunorubicin prolonged the survival time of NSG mice and reduced the leukemogenesis of AML.

Conclusion: Thus, these observations demonstrated combination of RSK inhibitor LJH-685 and FLT3 inhibitor FF-10101 showed synergism anti-leukemia effects in AML cell lines with FLT3-ITD mutations via inhibiting MAPK-RSKs-YB-1 pathway and provided new targets for therapeutic intervention especially for AML with FLT3-ITD mutations and Daunorubicin-resistant AML.

 

Comments:

The research findings you've provided demonstrate the potential therapeutic implications of targeting the RSK-YB-1 signaling pathway using the RSK inhibitor LJH-685 in acute myeloid leukemia (AML) cells, particularly those carrying FLT3-ITD mutations. Here's a breakdown of the key points from the study:

1. **FLT3 Mutations in AML:** FLT3 mutations are observed in around one-third of AML patients. FLT3-ITD mutations lead to constitutive activation of the RAS/MAPK signaling pathway, contributing to leukemogenesis.

2. **Role of RSKs:** Ribosomal S6 Kinases (RSKs) are downstream effectors of the RAS/Raf/MEK/ERK signaling pathway. In this study, RSK inhibition via LJH-685 was investigated for its impact on AML cells, particularly those with FLT3-ITD mutations.

3. **Effects of LJH-685 on AML Cells:**
   - LJH-685 inhibited proliferation and clone formation of AML cells.
   - It induced cell cycle arrest and apoptosis, primarily by targeting the RSK-YB-1 signaling pathway.
   - AML cells with FLT3-ITD mutations (such as MV4-11 and MOLM-13 cells) were more sensitive to LJH-685 compared to other AML cell lines.

4. **Synergistic Effects with FF-10101 and Daunorubicin:**
   - LJH-685 combined with FLT3 inhibitor FF-10101 or Daunorubicin showed synergistic effects:
   - It inhibited cell viability, promoted apoptosis, and induced cell cycle arrest in AML cells carrying FLT3-ITD mutations.

5. **In Vivo Efficacy:**
   - In vivo experiments using NSG mice corroborated the findings:
   - LJH-685 combined with FF-10101 or Daunorubicin extended survival and reduced leukemogenesis in AML models.

6. **Clinical Implications:**
   - The combination of RSK inhibitor LJH-685 and FLT3 inhibitor FF-10101 presents a promising avenue for therapeutic intervention in AML, especially for cases with FLT3-ITD mutations and Daunorubicin-resistant AML.
   - This combination therapy targets the MAPK-RSKs-YB-1 pathway, providing potential new targets for AML treatment.

In summary, the study suggests that the combination of LJH-685 with FLT3 inhibitors or conventional chemotherapeutic agents could be a novel and effective strategy for treating AML, particularly those cases associated with FLT3 mutations and drug resistance. These findings could potentially pave the way for future clinical trials exploring this combination therapy in AML patients.