PCNA and TUNEL analyses for tumor tissue. (A) Tumor sections immunostained with an antibody against PCNA revealed that there were many strongly positive nuclei in control tumor tissues, whereas such nuclei were rare in tumor tissues of 125I treatment group. (B) Quantification of PCNA staining showed mitotic index of 125I-implanted tumor was much lower than that of control group (☆: P < 0.05). (C) Apoptosis of tumor tissues in different groups were evaluated by TUNEL assays, which showed that 125I treatment induced a significant enhancement of apoptotic cells in contrast to control group. (D) Quantification of TUNEL assay showed that apoptosis index of 125I-implanted tumor was much higher than that of control group (☆: P < 0.05).