Role and mechanism of the CBX4-HDAC5-CERS6 axis in disrupting sphingomyelin metabolism in acute myeloid leukemia.

OBJECTIVE: To investigate the mechanism by which the CBX4-HDAC5-CERS6 axis regulates sphingolipid metabolism in acute myeloid leukemia (AML), with the goal of providing new theoretical foundations for the targeted therapy of AML. METHODS: This prospective study involved 50 AML patients and 50 healthy controls. The expression levels of CBX4, CERS6, and free ceramide were detected. RNA sequencing, proteomics, and lipidomics were employed to analyze CBX4's regulatory effects on sphingolipid metabolism-related genes and pathways. Using THP-1 and KG-1 cell lines, we validated the molecular mechanisms of the CBX4-HDAC5-CERS6 axis through techniques including gene knockdown (siRNA), overexpression, chromatin immunoprecipitation (ChIP), and dual-luciferase reporter assays. CCK-8 assay, flow cytometry, and Western blot were used to analyze the effects of CBX4 on cell proliferation, cell cycle, and key signaling pathways. RESULTS: CBX4 was significantly overexpressed in AML cells, with its expression levels markedly higher in THP-1 and KG-1 cell lines compared with CD34+ normal hematopoietic stem cells (P<0.05). Analysis of clinical samples revealed that the mRNA expression levels of CBX4 and CERS6 as well as free ceramide content were significantly lower in the AML group than the control group (all P<0.05). Mechanistic studies demonstrated that CBX4 knockdown significantly downregulated both mRNA and protein expression of CERS6 (P<0.05) and activated the PI3K/AKT and MAPK signaling pathways. Furthermore, CBX4 indirectly regulated CERS6 transcription by suppressing HDAC5 expression, and dual-luciferase reporter assays confirmed that HDAC5 directly targets the CERS6 promoter region (P<0.05). Combined use of ceramide synthesis inhibitors synergistically enhanced the activation of p-AKT/p-PI3K and p-MEK1/2/p-Raf1 signaling pathway associated proteins induced by CBX4 knockdown. CONCLUSION: The CBX4-HDAC5-CERS6 axis influences AML malignant progression by regulating sphingolipid metabolism, and targeted intervention of this axis may represent a novel therapeutic strategy for AML.