Toosendanin suppresses acute myeloid leukemia by targeting DDX5/c-Myc axis to inhibit protein synthesis

Acute myeloid leukemia (AML) remains a therapeutic challenge due to relapse and resistance, driving the need for novel therapeutic strategies. While the natural compound toosendanin (TSN) has shown anti-tumor activity in solid cancers, its mechanism of action and direct molecular targets in AML are unknown.

We utilized an integrated chemical biology approach (affinity pull-down, cellular thermal shift assay (CETSA), drug affinity responsive target stability (DARTS) assay, molecular docking) for target deconvolution. Downstream mechanisms were dissected using transcriptomic (RNA-seq), functional assays and genetic rescue experiments. Efficacy and toxicity were evaluated in an MLL-AF9-driven AML mouse model.

TSN exhibited potent anti-AML activity at nanomolar concentrations, inhibiting cell proliferation, inducing dual G0/G1 and G2/M phase arrest, and triggering caspase-dependent apoptosis. To uncover the mechanism, we identified the RNA helicase DDX5 as a novel, direct cellular target of TSN. TSN binding promoted DDX5 degradation via both proteasomal and lysosomal pathways, a dual mechanism ensuring its efficient depletion. Subsequent transcriptomic analyses revealed that TSN, via targeting DDX5, impaired the oncogenic c-Myc transcriptional network, leading to suppressed ribosome biogenesis and global protein synthesis. Genetic rescue experiments linked DDX5 to these effects. Importantly, in preclinical AML model, TSN treatment significantly prolonged survival without observable toxicity, confirming its therapeutic potential.

Our study delineates a coherent and novel anti-leukemic pathway: TSN suppresses AML by directly targeting DDX5 for degradation, thereby inhibiting the pro-survival c-Myc axis. These findings elucidate the pharmacology of TSN and validate the DDX5/c-Myc axis as a promising therapeutic candidate in AML.