Celastrol induces apoptosis of myelodysplastic syndrome cells through a ROS-dependent pro-apoptotic...

Myelodysplastic syndromes (MDS) represent clonal hematopoietic stem cell disorders with inherent propensity for leukemic transformation. Emerging evidence implicates dysregulated Endoplasmic-Reticulum stress (ER-stress) in sustaining malignant clones through adaptive suppression of pro-apoptotic PERK/CHOP signaling. Celastrol serves as a natural compound with documented ER-stress modulating activity in solid tumors. However, the beneficial effect and molecular mechanisms of celastrol on MDS are unknown.

This investigation aims to determine whether celastrol inhibits MDS tumor cell proliferation, and molecular mechanisms of celastrol on MDS involved in the terminal pro-apoptotic ER-stress branches PERK/CHOP axis.

Celastrol demonstrated cytotoxic effects against MDS cell lines (IC50 1.09 µM-2.02 µM) and primary patient-derived bone marrow mononuclear cells (n = 3, mean apoptosis rate: 42.6%). Flow cytometry results showed that celastrol can induced MDS-L and SKM-1 cell apoptosis. And celastrol treatment can elevate apoptotic protein expression, including cleaved PAPR1, rH2AX and cleaved caspase 3. Celastrol can induce ROS production, and the NAC pretreatment can eliminate the apoptosis-induced effect of celastrol. Our Bulk RNA-seq result of SKM-1 cell and the bone marrow sequencing results of patients with high-risk MDS (GSE19429) suggested that celastrol can activate the terminal pro-apoptotic ER-stress branches PERK/CHOP axis. In consistent, electron microscope screen found celastrol can induce ER Swelling and thickening in a ROS-dependent manner. In vitro experiments, celastrol can increase the eIF2α-ATF4-CHOP protein expression in a ROS-dependent manner. Molecular docking (ΔG -10.9 kcal/mol) and CETSA suggested celastrol might bind to BIP protein. In vivo, celastrol monotherapy can reduce tumor burden in xenograft models. Moreover, in MDS-L cell, celastrol can synergistically enhance the effect of venetoclax, as a BCL2 inhibitor inducing tumor cell apoptosis.

These results indicate that celastrol induces apoptosis in MDS cells and can activate the pro-apoptotic terminal ER-stress response in a ROS-dependent manner. Together, our findings suggest that ER stress activation plays a role in celastrol‑induced apoptosis in MDS cells, supporting further investigation of celastrol as a candidate for MDS therapy.