Dysfunction of core clock genes regulates malignant phenotype and gemcitabine sensitivity of cholangiocarcinoma cells.

The circadian clock governs daily rhythms in numerous physiological processes through precise regulation of gene expression and biochemical functions. Dysregulation of the circadian rhythm has been implicated in carcinogenesis and cancer progression. However, the mechanisms by which the circadian clock influences cancer phenotype and chemotherapy resistance, particularly in cholangiocarcinoma (CCA), remain poorly understood. Using cell lines established from primary CCA and metastatic ascites of two male patients, we manipulated core clock genes ( BMAL1 , PER2 , and NR1D1 ) to evaluate their effects on circadian rhythms. We analyzed alterations in circadian phenotypes at dynamic and single time points and assessed their impact on cancer-related phenotypic changes, including proliferation, apoptosis, cell cycle regulation, migration, invasion, and the expression of epithelial-to-mesenchymal transition (EMT) and cancer stem cell markers. Additionally, we examined the impact of circadian disruption on gemcitabine sensitivity. Genetic deletion of BMAL1 , PER2 , and NR1D1 disrupted circadian rhythm and significantly altered cancer phenotypes. Notably, BMAL1 and NR1D1 impairment exacerbated cell migration, invasion, and EMT activation in CCA cells. BMAL1 loss also induced gemcitabine resistance. In contrast, PER2 repression enhanced chemosensitivity and inhibited metastasis. The modulation of the circadian gene triggered phenotypic changes in CCA cells, indicating a crucial involvement of core-clock components in the pathological mechanisms hastening bile duct cancer malignancy. Our findings advance the understanding of regulating CCA malignancy and may offer a novel target for its treatment.