Radiolabeled monoclonal antibodies appear to be gaining a role in the management of cancer by means of imaging methods to detect sites of increased radioactivity, and several products have been developed and tested clinically. In the area of radioimmunotherapy, the radiolabeled monoclonal antibodies have shown the potentials in the treatment of the microtumors and metastases due to its inherited benefit from bystander effect of the ionizing radiation delivered with radioimmunoconjugates. We have evaluated the antitumor effects of I-131 labeled P2AE12 antibody, prepared against glycopratein of gp52 MMTV-induced murine mammary tumor cell, in allogeneic model of pulmonary metastatic cancer. The BALB/c normal mice were injected intravenously with 5 x 10(5) murine breast cancer cells and pulmonary metastases were acauired in all mice. Three days and ten days after tumor cell injection, each set of 250uCi of I-131 labeled antibody was injected in 15-20 mice for one or two treatment group. Survival of treatment group was compared with that of control group. One-treatment resulted in prolonged median survival of mice bearing metastases from 14(range: 13-16 days) to 16 days(range: 1422days), and two-treatments to 22(range: 20 to more than 40 days) days. Treatment with I-131 labeled P2AE12, antibody resulted in marked reduction of tumor burden in lung sections taken on days 7 and 14 days. Our results showed that radiolabeled monoclonal antibody can inhibit the growth of allogeneic solid tumor metastases in mice. Although it did not cure these kinds of aggressive metastatic tumors, these findings encourage the further evaluation of the radioimmunotherapy in pulmonary metastases with different schemes to enhance tumor uptake of radiolabeled antibody, as well as lessen the uptake in normal tissue.
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