Tobacco Carcinogen Induces Persistent DNA Damage and Homologous Recombination Dysregulation in Pancreatic Ductal Carcinogenesis
The tobacco carcinogen NNK produces a biphasic DNA damage response in human pancreatic ductal epithelial cells: 5 days of exposure induced double-strand breaks with ATM-γH2AX activation and RAD51/BRCA2 recruitment, while 50 days caused persistent damage signaling, upregulation of HR genes (RAD51, BRCA1, BRCA2, FANCD2, PLK1), altered RAD51 localization, and chromosomal instability. In human PDAC tissue microarrays and TCGA-PAAD data, increased γH2AX correlated with tumor progression and poor overall survival, and elevated RAD51 with adverse outcomes, positioning γH2AX as a candidate prognostic biomarker in tobacco-associated PDAC.