Non-irradiated tumors revealed an iodide accumulation of 7.0% ID/g with a tumor-absorbed dose of 52.37 mGy/MBq for 131I, while tumors pre-treated with a radiation dose of 5 Gy 24 h before MSC application showed an iodide uptake of 9.8% ID/g and a tumor-absorbed dose of 56.72 mGy/MBq for 131I. In the therapy study, the therapy group (5 Gy + SMAD-NIS-MSC 131I) showed a pronounced reduction in tumor growth leading to a complete tumor remission in a subset of mice and a dramatically prolonged survival of animals as compared to 5 Gy + CMV-NIS-MSC + 131I treated mice or untreated controls. The gene discussed is SLC5A5; the disease is neoplasm.