PTP4A3: A potential therapeutic target in Acute Myeloid Leukemia Free

Protein tyrosine phosphatase 4A3 (PTP4A3), a member of the protein tyrosine phosphatase family, regulates intracellular signaling by modulating protein phosphorylation. Previous studies have shown its aberrant overexpression in multiple solid tumors (e.g., breast, liver, and colorectal cancers) and correlation with tumorigenesis, progression, invasion, metastasis, and poor prognosis, with oncogenic effects mainly via promoting cell proliferation, inhibiting apoptosis, and enhancing tumor angiogenesis. However, its expression pattern, biological functions, and mechanistic roles in acute myeloid leukemia (AML) are poorly defined. This study comprehensively investigates these aspects and potential targeted inhibitors, aiming to provide novel insights for AML clinical therapy.

Analyses of TCGA PanCancer database transcriptomic data showed PTP4A3 expression in AML was markedly higher than in most solid tumors and normal hematopoietic tissues, with high expression across AML subtypes. RT-qPCR in multiple AML cell lines (NOMO-1, THP-1, Molm-13, EOL-1, MV411, HEL) and normal bone marrow mononuclear cells (BMNCs) validated this, with significantly higher levels in AML cell lines. Single-cell sequencing of AML patient samples revealed PTP4A3 overexpression specifically in malignant leukemia cells, with low expression in normal hematopoietic subsets. Survival analyses using TCGA-AML data and clinical follow-up indicated high PTP4A3 expression associated with shorter overall survival and disease-free survival, making it a potential poor prognostic biomarker in AML.

To explore PTP4A3's effects on AML cell biology, siRNA was used to knock down PTP4A3 in MV411 and HEL cells. CellTiter-Glo and EdU incorporation assays showed reduced proliferation and slower growth rates; flow cytometric analysis with Annexin V/PI dual staining revealed increased apoptosis. In vivo experiments also demonstrated slower tumorigenic rates in PTP4A3-knockdown AML cells.

Transcriptome sequencing identified enrichment of AKT/mTOR pathway-related genes in differentially expressed genes between PTP4A3-silenced and control cells. Western blot analyses showed PTP4A3 knockdown significantly reduced phosphorylation of AKT (p-AKT) and mTOR (p-mTOR), with no change in total AKT or mTOR levels, indicating PTP4A3 promotes AML cell proliferation and inhibits apoptosis by activating the AKT/mTOR pathway.

Virtual screening of small molecules via molecular docking against the PTP4A3 crystal structure (PDB ID: 5TSR) identified sorafenib, which showed high affinity for the PTP4A3 active site, forming stable interactions with GLN-145. Protein-drug binding assays (DARTs and CETSA) confirmed sorafenib protects PTP4A3 from degradation; phosphatase activity assays demonstrated it dose-dependently inhibited recombinant PTP4A3 activity with a low IC50. In cell-based assays, sorafenib treatment of AML cells (HEL, MV411 and primary AML) reduced p-AKT and p-mTOR levels, inhibited proliferation, and induced apoptosis—phenotypes consistent with PTP4A3 knockdown. Notably, PTP4A3 overexpression attenuated sorafenib's inhibitory effects, confirming sorafenib acts partially via specific PTP4A3 inhibition in AML cells.

In summary, PTP4A3 is aberrantly overexpressed in AML and associated with poor prognosis. It drives AML progression as an oncogene by activating AKT/mTOR signaling to promote proliferation and suppress apoptosis. Sorafenib is identified as a potential PTP4A3-targeting inhibitor that suppresses AML malignancy via this mechanism. These findings highlight PTP4A3 as a novel therapeutic target in AML and suggest sorafenib's potential utility, offering new insights for targeted therapy development.