Toosendanin Suppresses Acute Myeloid Leukemia by Targeting DDX5/c-Myc Axis to inhibit Protein Synthesis

The treatment of acute myeloid leukemia (AML) continues to be challenged by relapse and resistance, necessitating the development of novel therapeutic strategies. Toosendanin (TSN), a natural product derived from traditional Chinese medicine, exhibits antitumor activity in solid tumors; however, its mechanism of action and direct molecular targets in AML remain undefined. Here, we demonstrate that TSN potently inhibits AML cell proliferation, induces dual G0/G1 and G2/M phase arrest, and triggers caspase-dependent apoptosis at nanomolar concentrations. Using an integrated approach, including affinity pull-down, cellular thermal shift assay (CETSA), and molecular docking, we identified RNA helicase DDX5 as a direct target of TSN. TSN binding promotes DDX5 degradation via both proteasomal and lysosomal pathways. Transcriptomic and functional analyses revealed that TSN downregulates the c-Myc transcriptional network via DDX5 targeting, leading to the suppression of ribosome biogenesis. Rescue experiments confirmed that DDX5 is the central mediator of this pathway. In an MLL-AF9-driven AML mouse model, TSN treatment significantly prolonged survival, without observable toxicity. Collectively, our study delineates a novel anti-leukemic mechanism wherein TSN targets DDX5 for degradation and consequently inhibits c-Myc signaling, providing a rationale for therapeutic targeting of the DDX5/c-Myc axis and further development of TSN in AML. Overall design: MOLM-13 cells were treated with 20 nM TSN or DMSO for 48 h (n=3 biological replicates). Total RNA was extracted, and libraries were constructed and sequenced using the NovaSeq™ X Plus platform. Differential gene expression analysis was performed using DESeq2 v1.26.0 (FDR < 0.05, |log2FC| > 0.584). Gene Set Enrichment Analysis (GSEA) was conducted using the MSigDB Hallmark 2023 gene set (FDR < 0.25), and the analysis was performed on the OmicShare platform v6.2.