Halofuginone exerts broad-spectrum cytotoxic effects by regulating p-eIF2a-S100A8/A9-calcium signaling, inhibiting global protein synthesis, and reversing the resistance of idarubicin in acute myeloid leukemia

NOP2/Sun RNA methyltransferase family member 2 (NSUN2) catalyzes 5-methylcytosine (m5C) modifications in tRNA, rRNA, and mRNA, playing critical roles in various malignancies. However, its expression and functional relevance in B-acute lymphoblastic leukemia (B-ALL) remain largely undefined. Lineage-negative progenitor cells from Nsun2 knockout (?/?) and wild-type (fl/fl) mice were used to generate BCR-ABL (P190)-driven murine B-ALL model. Furthermore, RNA sequencing (RNA-seq) was performed to identify NSUN2 targets. Here, we found that NSUN2 expression was significantly higher in bone marrow (BM) cells from B-ALL patients than normal controls (NCs). Knockdown of NSUN2 reduced m5C amounts, induced apoptosis and ferroptosis in B-ALL cells. Moreover, Nsun2 knockout significantly suppressed the leukemic burden and extended the OS in murine B-ALL model in vivo. RNA-seq and subsequent studies identified ferritin heavy chain 1 (FTH1) as a downstream target of NSUN2. Mechanistically, NSUN2 knockdown reduced m5C modifications on 3'UTR of FTH1 mRNA, impairing its stability and reducing FTH1 expression. Overexpression of wild-type (WT) NSUN2, but not its mutants, blocked NSUN2 knockdown-induced cytotoxic effects, indicating that NSUN2 enhances leukemogenesis in an m5C-dependent manner. In addition, NSUN2 facilitated global protein synthesis and ribosome biogenesis by enhancing fibrillarin (FBL) translation efficiency. In contrast, Nsun2 depletion was dispensable for hematopoiesis and exerted minimal impact on ferroptosis and protein synthesis in murine pre-B (B220+) cells, suggesting selective leukemic dependency. Our results demonstrate that NSUN2 facilitates leukemogenesis by increasing FTH1 expression and enhancing FBL-mediated ribosome biogenesis in an m5C-dependent manner. Targeting NSUN2 might provide a promising therapeutic strategy for B-ALL. Overall design: Ethnopharmacological relevance: Alkaloid febrifugine., an herbal medicine in China, is prescribed routinely for malaria treatment. Halofuginone (HF), a natural product isolated from alkaloid febrifugine, exhibits anti-tumor and anti-inflammatory ability. Aim of the study: Acute myeloid leukemia (AML) is a heterogeneous hematological malignancy with low overall survival (OS). Resistance to chemotherapeutic drugs such as idarubicin (IDA) results in treatment failure. This study investigated the role of HF in anti-AML ability and in overcoming IDA resistance in AML cells. Materials and methods: Apoptosis, proliferation, cell cycle, and colony were assessed in AML cells treated with HF. RNA sequencing (RNA-seq) was performed to identify the potential targets of HF. Human relapsed and refractory (R/R) AML samples were xenografted into mice to assess the anti-leukemic effects of HF in vivo.