Upregulation of APOC1 Mediated by the Transcription Factor SOX4 Promotes the Malignant Biological Behaviors of Neuroblastoma Cells and Inhibits Ferroptosis

Abstract

Background: Neuroblastoma (NB) that arises from neuroblasts is recognized as the most frequently-occurring extracranial solid malignancy in infancy. We aimed to expound the impacts of apolipoprotein C1 (APOC1) on NB and the mechanisms related to Sry-related HMG-BOX-4 (SOX4). Methods: APOC1 expression in NB cells was analyzed by reverse transcription-quantitative PCR (RT-qPCR) and western blot. After APOC1 depletion, cell counting kit-8 (CCK-8) and colony formation assays separately appraised cell viability and proliferation. Cell cycle was also evaluated by flow cytometry analysis. Concurrently, wound healing and Transwell assays separately measured cell migration and invasion. Thiobarbituric acid reactive substance (TBARS) assay kit was adopted for the measurement of lipid peroxidation. Intracellular Fe²⁺ was detected by a FerroOrange fluorescent probe. Western blot tested the expression of proteins involved in epithelial-to-mesenchymal transition (EMT) and ferroptosis. JASPAR, luciferase reporter and Chromatin immunoprecipitation (ChIP) assays respectively predicated and confirmed that SOX4 could bind to APOC1 promoter region. Then, the aforementioned experiments were performed again when APOC1 was silenced and SOX4 was further overexpressed simultaneously. Results: Significantly elevated APOC1 expression was observed in NB cells (p < 0.01 or p < 0.001). APOC1 knockdown restrained NB cell proliferation (p < 0.01 or p < 0.001) and induce the cell cycle arrest (p < 0.001). The capacities of cell migration and invasion were inhibited following APOC1 silencing (p < 0.001). Moreover, APOC1 absence elevated the lipid peroxidation and induced ferroptosis (p < 0.001). Further, SOX4 was confirmed to bind to APOC1 promoter (p < 0.001). Rescue experiments revealed that SOX4 overexpression attenuated the impacts of APOC1 deletion on the malignant cellular behaviors in NB (p < 0.01 or p < 0.001). Conclusion: To conclude, APOC1 transcriptionally activated by SOX4 exerted oncogenic effects on NB, providing an underlying targeted therapy for NB treatment.