Divergent cGAS–STING–IRF3 signaling profiles mark the transition from precancerous biliary lesions to cholangiocarcinoma

Cholangiocarcinoma (CCA) is a highly lethal malignancy and often exhibits histological overlap with non-malignant bile duct lesions, including cholangitis and precancerous lesions. The lack of reliable markers to distinguish malignant from non-malignant biliary lesions underscores the need for improved diagnostic approaches. The cGAS-STING pathway, a key regulator of innate immune responses, may provide insight into inflammation-associated carcinogenesis. This study aimed to compare the expression of cGAS, STING, IRF3, and IFN-α among CCA, precancerous lesions, and cholangitis, and to evaluate their potential diagnostic relevance. A total of 198 formalin-fixed paraffin-embedded (FFPE) tissue samples were analyzed, including 164 cases of cholangiocarcinoma, 26 precancerous lesions, and 8 cases of cholangitis. Immunohistochemistry for cGAS, STING, IRF3, and IFN-α was performed, and protein expression was quantitatively assessed using H-scores. Diagnostic performance was evaluated using receiver operating characteristic (ROC) curve analysis. ROC-derived H-score cut-off values were applied in logistic regression models to assess association with CCA. IRF3 and IFN-α expression were markedly increased in precancerous lesions compared with cholangitis. High cGAS and IRF3 expression at ROC-derived cut-off values showed association with CCA. Logistic regression analysis demonstrated that elevated cGAS (H-score ≥ 202; p = 0.026) and IRF3 (H-score ≥ 201; p = 0.032) expression were associated with increased odds of CCA. Although cGAS and IRF3 showed limited standalone diagnostic accuracy, their ROC-derived H-score thresholds were modestly associated with CCA. This work could provide adjunctive diagnostic information when integrated with routine histopathological assessment.