Integrated bioinformatics and tissue-based validation reveal the oncogenic role of hsa_circ_0043256 and hsa_circ_0004789 in gastric cancer.

Circular RNAs (circRNAs) play a key role in gastric cancer (GC) pathogenesis. This study hsa_circ_0043256 and hsa_circ_0004789, and their interactions with miR-28-5p/Cyclin B1 (CCNB1) and miR-5683/CCNB1, via bioinformatic and experimental methods. We retrieved expression data for circRNAs, miRNAs, and mRNAs in GC from Gene Expression Omnibus and The Cancer Genome Atlas. Using online databases and R tools, we identified downstream miRNAs and target mRNAs to build a competing endogenous RNA (ceRNA) network. After identification of hub genes and performing functional enrichment, we defined two regulatory axes: hsa_circ_0043256/miR-28-5p/CCNB1 and hsa_circ_0004789/miR-5683/CCNB1. We studied 32 paired tumor and adjacent tissues to assess all genes and CCNB1 protein expression, along with correlations, histopathological associations, ROC curves, and survival outcomes. We identified 58 circRNAs, 123 miRNAs, and 2126 mRNAs, and, further, by novelty checking and downstream RNA analysis, identified two axes. The expression of hsa_circ_0043256, hsa_circ_0004789, and CCNB1 mRNA and protein levels was elevated, while miR-28-5p and miR-5683 levels were reduced. Correlations observed among axis components supported the ceRNA hypothesis. The hsa_circ_0004789/miR-5683/ axis showed an AUC value for the combined ROC curve near 1, suggesting strong diagnostic potential. Lower and higher miR-5683 levels were correlated with better survival. Both circ_0043256 and circ_0004789 were associated with histological grade, lymphatic invasion, perineural invasion, and lymph node involvement. This study highlights circ_0043256/miR-28-5p/CCNB1 and circ_0004789/miR-5683/CCNB1 as promising axes for GC diagnosis and treatment strategies.