Monoclonal antibodies NORM-1 and NORM-2 induce more normal behavior of tumor cells in vitro and reduce tumor growth in vivo

Abstract

In this study, large numbers of hybridomas (produced by syngeneic immunization with B16 mouse melanoma and fusion with NS-1 myeloma cells) were screened for the production of antibodies that affected morphology and growth of animal and human tumor cells in vitro. Two such antibodies, NORM-1 and NORM-2 (both IgG2a), inhibited the growth of B16 melanoma cells in soft agar and increased the serum requirements of tumor cells in tissue culture. Antibody NORM-2 also inhibited the growth of SV40-transformed 3T3 cells in agar and caused them to deposit more fibronectin into extracellular matrix. These antibodies thus seem to induce a more normal behavior of tumor cells in vitro. In vivo both antibodies reduced the number of growing lung tumors of B16 melanoma in C57BL/6 mice by 70%–90% when injected 3 days after the tumor cells. By immunoprecipitation of 35S-methionine-labeled cell extracts, NORM-2 antibody recognized a 59 kd protein in B16 mouse and in A375 human melanoma cells but not in 3T3 fibroblasts.