To confirm the radiosensitizing effect of OBP-301 in tumor tissues, we assessed the level of Ki67-positive (proliferation marker), TUNEL-positive (apoptosis marker), and γH2AX-positive staining (DNA damage marker) in subcutaneous xenograft tumors grown from highly radiosensitive SK-ES-1 and moderately radiosensitive HT1080 cells (Figs 4 and 5). Here, MKI67 is linked to neoplasm.