CASP3 and neoplasm: In addition, immunohistochemical analysis for Ki67 and caspase-3 showed significantly lower numbers of proliferating cells and increased levels of apoptosis after treatment with 131I in CNE-2Z-NIS tumors compared to CNE-2Z tumors treated with 131I, CNE-2Z-NIS and CNE-2Z tumors treated with PBS, suggesting that 131I uptake by CNE-2Z-NIS cells induced tumor cell damage in addition to tumor cell death.