Uptake of 5-iododeoxyuridine as a measure of tumor growth and tumor inhibition.

The DNA synthesis of tumor cells in spleen, lung and liver of mice bearing spontaneous or transplanted lymphomas or Lewis lung carcinoma was determined by measuring the uptake of 5-iododeoxyuridine labeled with iodine-125 (125IUdR). An in vitro uptake method was also developed to assess 125IUdR uptake of peripheral blood of leukemic animals. A direct relationship was found between isotope uptake values and the extent of neoplastic growth. The 125IUdR uptake method was found to be applicable to determination of inhibition of tumor growth in drug-treated animals and in pre-sensitized allogeneic hosts and to measurement of regression in non-sensitized allogeneic mice.