Integrated Bioinformatics Identification and Multi-Dimensional Characterization of Diagnostic Hub Genes in Colorectal Cancer.

Colorectal cancer (CRC) motivates the investigation of complementary molecular markers, although tissue-transcriptomic discrimination does not by itself establish early-detection performance. We identified differentially expressed genes in 98 paired CRC and adjacent-normal samples from GSE44076 using gene-level limma analysis (|log2FC| > 1; Benjamini-Hochberg-adjusted p < 0.05), screened candidates through a STRING protein-protein interaction network, and evaluated diagnostic performance with independent validation in GSE9348. Functional characterization included MSigDB KEGG_LEGACY over-representation analysis and preranked GSEA, immune-marker correlations, mRNA stemness index analysis, exploratory topology-filtered cysteine assessment, exploratory TCGA-COAD prognostic modelling, and literature-curated single-cell contextualization. Seven candidates-AQP8, CA7, GUCA2A, GUCA2B, BEST4, TMIGD1, and OTOP2-showed AUC values of 0.986-0.995 in the discovery cohort; five genes showed AUC values of 0.999-1.000 in the retrospective GSE9348 tissue cohort. AQP8 and GUCA2B showed weak nominal inverse correlations with mRNAsi that did not remain significant after correction across six tests (BH-FDR = 0.078), and the genes were predominantly associated with differentiated colonic epithelial lineages. The exploratory prognostic model was non-significant. These results identify seven tissue-transcriptomic candidates with strong dataset-specific discriminative performance and provide a multidimensional biological framework warranting experimental validation and prospective clinical evaluation.