Abstract: Objective To investigate and evaluate the curative effect of radioimmunological targeting drug on nude mice bearing breast cancer. Methods The anti-CEA monoclonal antibody C50 was combined with ¹³¹I to produce radioimmunological targeting drug. 16 nude mice inoculated subcutaneously with breast cancer cell MCF-7 with tumor diameter about 0.5 cm were randomly into 4 groups(n=4): group Ⅰ, injected in part with ¹³¹I-C50 18.5 MBq; group Ⅱ, injected in part with ¹³¹I-C50 3.7 MBq; group Ⅲ, injected in part with¹³¹I-mIgG 18.5 MBq; group Ⅳ, injected in part with C50 0.75 μg. The size of tumor volume and inhibitory rate (IR) after treatment for six weeks were calculated and compared with the control group. Results The tumor volume and curves for tumor growth and tumor weight had significant differences between group Ⅰ and the group Ⅲ as well as group Ⅱ (P<0.01); and there was significant difference between group Ⅰ and group Ⅱ (P<0.05), there was no significant difference between group Ⅲ and group Ⅳ (P>0.05). Conclusion Anti-CEA monoclonal antibody C50 labeled with radionuclide ¹³¹I could inhibit the growth of the tumor when given locally. ¹³¹I-C50 has a potential value of clinical application .

Key words: CEA monoclonal antibody C50, ^131<, sup>I, radioimmunotherapy