The MIR4435-2HG/miR-26a-5p/COL1A2 ceRNA axis drives gastric cancer progression via PI3K/AKT pathway activation

Gastric cancer (GC) remains a leading cause of cancer mortality worldwide, yet functionally validated competitive endogenous RNA (ceRNA) axes with clear mechanistic significance in GC are scarce. This study aimed to construct a GC-specific ceRNA network, identify a high-priority regulatory axis, and elucidate its role in GC progression. A GC-specific ceRNA network was constructed using multi-omic data from the TCGA-STAD cohort. The MIR4435-2HG/miR-26a-5p/COL1A2 axis was nominated through integrated differential expression, network topology, and survival analyses. Stable MIR4435-2HG overexpression and knockdown AGS and MKN-45 cell lines were established via lentiviral transduction and subjected to proliferation, apoptosis, migration, and invasion assays. Dual-luciferase reporter assays validated molecular interactions, and Western blotting assessed PI3K/AKT pathway activity. Rescue experiments with miR-26a-5p mimics/inhibitor and COL1A2 overexpression constructs interrogated the mediating mechanisms. MIR4435-2HG and COL1A2 were significantly upregulated in GC tissues while miR-26a-5p was downregulated ( p < 0.001), yielding AUC values of 0.982, 0.654, and 0.874, respectively. Elevated MIR4435-2HG and COL1A2 correlated with poor prognosis (HR = 1.42 and 1.48), whereas high miR-26a-5p associated with favorable outcomes (HR = 0.62). MIR4435-2HG overexpression promoted proliferation, migration, and invasion while suppressing apoptosis; knockdown produced opposite effects. Dual-luciferase assays confirmed direct MIR4435-2HG–miR-26a-5p binding and miR-26a-5p–COL1A2 3''UTR interaction. Rescue experiments established miR-26a-5p and COL1A2 as essential mediators of MIR4435-2HG oncogenic activity. MIR4435-2HG overexpression significantly elevated p-PI3K/PI3K and p-AKT/AKT ratios, effects reversible by miR-26a-5p mimics or COL1A2 depletion. MIR4435-2HG competitively sequesters miR-26a-5p to derepress COL1A2, thereby activating PI3K/AKT signaling and driving GC malignant progression. This axis represents a potential candidate for GC diagnosis, prognosis assessment, and targeted intervention, pending further in vivo and clinical validation.