Targeting mitochondrial calcium homeostasis via novel S100A9 inhibitor B2 as a promising agent against AML.

BACKGROUND

Relapsed/refractory (R/R) acute myeloid leukemia (AML) remains difficult to treat due to limited actionable targets and frequent drug resistance. Integrated analyses of multiple AML cohorts identified S100A9 as a candidate factor associated with disease aggressiveness and suboptimal therapeutic response in R/R AML.

METHODS

We combined genetic perturbation of S100A9 with mitochondrial Ca2+ measurements to define its functional role in AML cells. A structure-guided virtual screening strategy was then used to identify small molecules with direct affinity for S100A9, followed by biochemical validation and anti-leukemic profiling in AML cell lines, primary patient samples, normal hematopoietic cells, and xenograft models. Transcriptomic (RNA-seq) and protein assays were performed to characterize pathway changes induced by the lead compound.

RESULTS

S100A9 modulation altered mitochondrial Ca2+ homeostasis and AML cell fitness. We identified B2, a novel S100A9-binding small molecule that reduces S100A9 abundance and is associated with increased mitochondrial Ca2+ accumulation. RNA-seq and immunoblotting demonstrated concomitant attenuation of survival signaling, including reduced STAT5 and AKT activation. B2 preferentially impaired S100A9-high AML cell lines and primary samples with minimal toxicity to normal hematopoietic cells, and significantly reduced leukemia burden in xenograft models.

CONCLUSIONS

These findings establish S100A9 as a regulator of mitochondrial Ca2+ homeostasis in AML and support B2 as a translational candidate that targets mitochondrial vulnerabilities and downstream survival pathways in R/R AML.