Repurposing Rosiglitazone Induces Apoptosis Accompanied by Impaired Antioxidant Defense in Cholangiocarcinoma Cells: Findings from Proteomic and Functional Analyses

<b>Objectives</b>: The repurposing of existing drugs as anticancer agents has attracted attention in cancer drug discovery. This study aimed to examine the anticancer efficacy of rosiglitazone (RSG) against cholangiocarcinoma (CCA) and its underlying mechanisms. <b>Methods</b>: The effect of RSG on the viability of KKU-100 CCA cells was examined. The possible molecular targets were identified using proteomic analysis and verified by a series of cell-based assays. Furthermore, the expression of PPARγ protein in CCA tissues was also assessed. <b>Results</b>: RSG exhibited a cytotoxic effect against KKU-100 cells. Proteomic analysis demonstrated a significant different expression protein pattern of the 100 μM RSG-treated group compared to the control group. Significant alteration of several proteins was found, including the up-regulation of calcium-binding, cytoskeletal, and metabolic proteins, concomitant with the down-regulation of antioxidant enzymes. Detailed analyses revealed that RSG induced apoptosis in CCA cells, accompanied by increased caspase 3/7 activities, reactive oxygen species (ROS) generation, and disruption of mitochondrial function. RSG altered the expressions of annexin A1 and antioxidant enzymes, according to Western blot analysis. GW9662, a PPARγ antagonist, did not affect the viability and apoptosis of KKU-100 cells caused by RSG. Immunohistochemistry analysis revealed that PPARγ expression in CCA patients was associated with sex, but not with other common clinicopathological parameters. Its expression did not correlate with patients' overall survival time. <b>Conclusions</b>: RSG induced apoptotic cell death in CCA cells, which was accompanied by increased ROS levels and impaired antioxidant defense. Its apoptosis-inducing effect is independent of PPARγ activation. These findings underscore the therapeutic potential of RSG for CCA treatment.