NES1 gene is thought to be a tumor-suppressor gene. Our previous study found that overexpression of NES1 gene in PC3 cell line could slow down the tumor proliferation rate, associated with a mild decrease in BCL-2 expression. The BCL-2 decrease could increase the sensitivity of radiotherapy to tumors. Thus, we supposed to have an "enhanced firepower" effect by combining overexpressed NES1 gene therapy and 131I radiation therapy uptake by overexpressed hNIS protein. We found a weak endogenous expression of hNIS protein in PC3 cells and demonstrated that the low expression of hNIS protein in PC3 cells might be the reason for the low iodine uptake. By overexpressing hNIS in PC3, the radioactive iodine uptake ability was significantly increased. Results of in vitro and in vivo tumor proliferation experiments and 18F-fluorothymidine (18F-FLT) micro-positron emission tomography/computed tomography (micro-PET/CT) imaging showed that the combined NES1 gene therapy and 131I radiation therapy mediated by overexpressed hNIS protein had the best tumor proliferative inhibition effect. Immunohistochemistry showed an obvious decrease of Ki-67 expression and the lowest BCL-2 expression. These data suggest that via inhibition of BCL-2 expression, overexpressed NES1 might enhance the effect of radiation therapy of 131I uptake in hNIS overexpressed PC3 cells.
Keywords: androgen-independent prostate cancer; normal epithelial cell-specific 1/kallikrein 10; proliferation; radiation therapy; sodium/iodide symporter.