Iodine-125 seed inhibits proliferation and promotes apoptosis of cholangiocarcinoma cells by inducing the ROS/p53 axis

With advances in radioactive particle implantation in clinical practice, Iodine-125 (¹²⁵I) seed brachytherapy has emerged as a promising treatment for cholangiocarcinoma (CCA), showing good prognosis; however, the underlying molecular mechanism of the therapeutic effect of ¹²⁵I seed is unclear. To study the effects of ¹²⁵I seed on the proliferation and apoptosis of CCA cells. CCA cell lines, RBE and HCCC-9810, were treated with reactive oxygen species (ROS) scavenger acetylcysteine (NAC) or the p53 functional inhibitor, pifithrin-α hydrobromide (PFTα). Cell counting kit-8 (CCK-8) assay, 5-bromo-2-deoxy-uridine (BrdU) staining, and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay and flow cytometry assay were performed to test the radiation-sensitivity of ¹²⁵I seed toward CCA cells at different radiation doses (0.4 mCi and 0.8 mCi). 2,7-dichlorofluorescein diacetate (DCF-DA) assay, real-time quantitative polymerase chain reaction (RT-qPCR), and western blot analysis were performed to assess the effect of ¹²⁵I seed on the ROS/p53 axis. A dose-dependent inhibitory effect of ¹²⁵I seeds on the proliferation of CCA cells was observed. The ¹²⁵I seed promoted apoptosis of CCA cells and induced the activation of the ROS/p53 pathway in a dose-dependent manner. NAC or PFTα treatment effectively reversed the stimulatory effect of ¹²⁵I seed on the proliferation of CCA cells. NAC or PFTα suppressed apoptosis and p53 protein expression induced by the ¹²⁵I seed. ¹²⁵I seed can inhibit cell growth mainly through the apoptotic pathway. The mechanism may involve the activation of p53 and its downstream apoptotic pathway by up-regulating the level of ROS in cells.