SOX18 and SOX30 in NSCLC: The Epigenetic Landscape of Methylation, miRNA Regulation, and Network Crosstalk in Tumor Progression

SOX (SRY-related HMG-box) transcription factors are key regulators of embryogenesis and vascular development, with emerging roles in cancer biology. In non-small-cell lung cancer (NSCLC), the contributions of SOX18 and SOX30 remain insufficiently understood, particularly regarding their epigenetic regulation and network interactions with angiogenic and immune-modulatory pathways. We examined 800 NSCLC specimens (400 lung adenocarcinomas, 400 squamous cell carcinomas) using immunohistochemistry, RT-qPCR, Western blotting, and spatial transcriptomics to profile SOX18, SOX30, and related signaling partners (SOX7, SOX17, MEF2C-Myocyte Enhancer Factor 2C, VCAM1-Vascular Cell Adhesion Molecule 1, p-STAT3-Signal Transducer and Activator of Transcription 3). Epigenetic regulation was assessed via droplet digital methylation-specific PCR of promoter CpG islands, while functional validation employed adenoviral delivery of hsa-miR-24-3p in NSCLC cell lines and 3D spheroid cultures. SOX18 protein was markedly overexpressed in both NSCLC subtypes, despite reduced transcript levels and consistent promoter hypermethylation, suggesting post-transcriptional regulation. In contrast, SOX30 expression was uniformly downregulated at both mRNA and protein levels, frequently linked to promoter hypermethylation, especially in squamous carcinoma. Spatial transcriptomics revealed SOX18 enrichment at tumor cores and invasive borders, co-localizing with MEF2C, VCAM1, and p-STAT3 in vascular and stromal niches, while SOX30 expression remained low across all tumor regions. Functional assays demonstrated that hsa-miR-24-3p suppressed SOX18 expression and partially modulated SOX30 and MEF2C, reinforcing a miRNA-driven regulatory axis. In summary, SOX18 and SOX30 play divergent roles in NSCLC progression: SOX18 functions as a pro-oncogenic factor driving angiogenesis and tumor-stroma interactions, while SOX30 acts as an epigenetically silenced tumor suppressor. Regulation of SOX18 by miR-24-3p highlights a potential therapeutic vulnerability. These findings underscore the significance of SOX transcription factors as biomarkers and potential targets for novel treatment strategies in NSCLC.