Role of DDX39A in modulating the tumor progression and radiosensitivity in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is an aggressive malignancy with limited treatment options. Although radiotherapy remains a cornerstone of curative treatment, intrinsic and acquired radioresistance frequently lead to locoregional recurrence and disease progression. DDX39A, a DEAD-box RNA helicase, regulates RNA metabolism in diverse cellular contexts; however, its role in ESCC pathogenesis and therapeutic resistance remains unclear. Bioinformatics analyses, immunohistochemistry, and functional assays were performed to characterize the role of DDX39A in ESCC. Tandem mass tag-based proteomics was used to identify downstream effectors. Mechanistic studies included RIP-qPCR, ChIP-qPCR, and dual-luciferase reporter assays. The therapeutic relevance was further validated using murine xenograft models. DDX39A was significantly upregulated in ESCC tissues and cell lines, and its high expression correlating with increased tumor proliferation. DDX39A knockdown suppressed malignant phenotypes and markedly enhanced radiosensitivity. Mechanistically, SP1 was prioritized from proteomic screening owing to its central role as a transcription factor regulating DNA repair gene expression. DDX39A directly binds to SP1 mRNA, stabilizing it and enhancing its translation efficiency without affecting transcription. The resulting increase in SP1 protein promotes binding to the − 223/−214 bp region of the Ku70 promoter, thereby transcriptionally activating this key component of the non-homologous end joining pathway and contributing to radioresistance. Rescue experiments confirmed that the DDX39A–SP1–Ku70 axis is both necessary and sufficient to mediate radioresistance. In vivo, DDX39A silencing enhanced radiosensitivity and improved tumor control in ESCC models. These findings identify DDX39A as a promising therapeutic target in ESCC radioresistance. The DDX39A–SP1–Ku70 axis provides a mechanistic rationale for the development of novel radiosensitization strategies.