Localization of radiolabeled SM1 monoclonal antibody to small-cell lung cancer tumors in mice

Small-cell carcinoma (SCCL) is an aggressive type of lung cancer. Though it is usually responsive to therapy, be it chemotherapy or radiation, the majority of patients eventually relapse and overall prognosis is dismal. New forms of therapy are, therefore, needed. SM1 monoclonal antibody (MAb) was developed in our laboratory and demonstrated to be highly reactive against SCCL. I-125 radiolabeled SM1 antibody was administered intravenously to nude mice bearing SCCL tumor xenografts. The mice were sacrificed, different tissues sampled and tested for uptake of radioactivity five days following antibody injection. There was over a 30 fold increase in localization of labeled antibody to the tumor as compared to muscle tissue. All organs tested showed an insignificant amount of MAb (p = 0.01) including the spleen, which had the highest normal tissue uptake in these experiments. These results demonstrate that SM1 MAb can be successfully targeted to SCCL xenografts. Its potential applications for imaging and therapy of SCCL in man are currently under investigation