An integrated bioinformatics and cell line study of NTN1 expression and tumor microenvironment associations in stomach adenocarcinoma

NTN1 encodes netrin-1, a secreted protein implicated in tumor biology. We explored NTN1 expression and clinical and tumor microenvironment associations in stomach adenocarcinoma (STAD) using public datasets and gastric cancer cell lines. Portal-based analyses evaluated expression, isoform usage, methylation, alterations, survival, and immune- and stromal-related gene correlations. Patient-level Cox regression was performed in TCGA-STAD, and independent expression and overall survival analyses used the ACRG cohort (GSE66229). Protein expression was assessed by Western blotting. NTN1 transcript levels were lower in STAD tumors than in normal reference tissues; both ACRG probes supported this difference across 98 matched pairs. NTN1-001 was the predominant isoform. Expression was lower across tumor-stage and grade subgroups than in normal tissues, without a consistent monotonic trend, and was lower in TP53-mutant than nonmutant tumors. Higher NTN1 expression was associated with poorer overall survival in univariable TCGA analysis (388 patients; HR = 1.102, p = 0.026), but not after clinical adjustment (368 patients; HR = 1.090, p = 0.086) or additional subtype adjustment. Neither ACRG probe was significant in adjusted survival models. GEPIA2 disease-free survival was nonsignificant. Purity-adjusted correlations linked NTN1 with selected immune- and stromal-related transcripts, including TGFB1, while Western blotting showed heterogeneous protein expression between cell lines. These exploratory findings suggest variation in NTN1 expression and transcriptional associations in STAD, without establishing independent prognostic value or regulatory mechanisms. Further clinical and functional validation is warranted.