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). Here, DNTT is linked to cholangiocarcinoma.