Exposure assessment of N-Nitroso-compound levels in GC patients and explored the potential core genes of Nitrosamine-induced GC carcinogenesis

Background: Exposure to N-nitroso compounds (NNCs) is closely correlated with the pathogenesis of gastric cancer (GC). This study aimed to investigate the internal levels of N-nitrosamines in GC patients and further explore the potential key triggers underlying NNCs-induced GC carcinogenesis by combining network toxicology approaches with experimental verification.

Methods: Solid-phase extraction coupled with gas chromatography-mass spectrometry (SPE-GC-MS) was applied to determine the concentrations of nine N-nitrosamines in 24 pairs of urine samples from GC patients and healthy controls. Potential N-nitrosamine-associated target genes related to GC were retrieved from the Comparative Toxicogenomics Database (CTD) and GeneCards database. Core hub genes were screened via topological analysis and functional enrichment analysis. Molecular docking simulations were performed to evaluate the binding interactions between N-nitrosamines and target proteins. RT-qPCR was used to validate the expression levels of key genes.

Results: Nine N-nitrosamines were successfully detected in urine samples. Among them, the levels of NMor (18.67±14.94 ng/mL), NPyr (7.03±12.49 ng/mL), NDPA (6.11±6.50 ng/mL), and NDphA (5.52±2.86 ng/mL) were significantly elevated in urine samples from 24 paired GC patients. Six genes, including BUB1B, FANCI, PLK1, TOP2A, CDK1, and CCNB1, were identified as the core genes involved in N-nitrosamine-induced GC tumorigenesis. Functional enrichment results revealed that the apoptotic process, G2/M transition were the vital biological mechanisms mediating the carcinogenic effect of N-nitrosamines. Furthermore, RT-qPCR validation confirmed that BUB1B, FANCI, PLK1, TOP2A, and CCNB1 were significantly upregulated in GC tissues and cell samples.

Conclusion: A total of nine were detected in urine samples of GC patients. BUB1B, FANCI, PLK1, TOP2A, CDK1, and CCNB1 are key regulatory genes involved in N-nitrosamine-induced gastric cancer, suggesting their potential value as biomarkers for gastric cancer. Limitations: The sample size for gastric cancer patients is relatively small; we will continue to expand the study population for further validation.