Sphingomyelin phosphodiesterase 1 knockdown promotes exogenous dihomo-γ-linolenic acid-induced ferroptosis in acute myeloid leukemia cells

To identify the potential target genes involved in the regulation of dihomo-γ-linolenic acid (DGLA)-induced ferroptosis in acute myeloid leukemia (AML) cells and to investigate their functional role in this process.

BALB/c nude mouse models bearing subcutaneous THP-1 cell xenografts were treated with DGLA or an equal volume of vehicle by gavage (n=6). Tumor growth was monitored, and ferroptosis-related markers in the xenografts were detected. RNA-seq combined with FerrDb analysis was used to identify a target gene involved in DGLA-induced ferroptosis in AML cells, followed by qRT-PCR validation. A target gene-knockdown AML cell line was established to evaluate the effects of knockdown combined with DGLA treatment on AML cell phenotypes and ferroptosis in vitro and in vivo.

In the tumor-bearing mice, DGLA treatment markedly reduced the tumor volume and weight, and the tumor cells showed typical ultrastructural changes of ferroptosis with upregulated levels of ROS, MDA, and Fe²⁺ and increased mRNA and protein expression levels of TfR1 and PTGS2. RNA-seq combined with the FerrDb database analysis revealed significant upregulation of SMPD1 in AML cells with DGLA-induced ferroptosis. In THP-1 cells with SMPD1 knockdown, DGLA treatment significantly reduced the cell viability, aggravated mitochondrial ferroptotic injury, and increased intracellular ROS, MDA and Fe²⁺ levels, causing also significant reductions of protein levels of GPX4 and SLC7A11. In the mouse models bearing xenografts derived from THP-1 cells with SMPD1 knockdown, DGLA treatment significantly decreased tumor volume and weight and increased the expressions of the lipid peroxidation markers (MDA, ROS, and Fe²⁺) and the protein levels of TfR1 and PTGS2.

SMPD1 knockdown enhances DGLA-induced ferroptosis and represses cell viability in AML cells both in vitro and in vivo.