A novel approach to production of antitumor monoclonal antibodies: antibody to a cell surface glycoprotein associated with transformation by a human oncogene

Transfection is a technique for inducing transformation of normal fibroblasts (NIH 3T3) with DNA (oncogenes) from human tumors. Our goal was to determine if these transformed cells expressed antigens associated with malignancy. NIH 3T3 cells were transfected with DNA fragments from a human acute lymphocytic leukemia (ALL 1-69), and transformed colonies were selected for growth in soft agar. Transfected cells containing human DNA sequences demonstrated by Southern blot analysis were used to immunize Balb/C mice. Monoclonal antibodies were produced and screened for binding to the parental leukemia (ALL 1-69), transfectant (17(2], and 3T3 cells in an enzyme-linked assay. A monoclonal antibody (IgM kappa) designated 17-9H3 bound to ALL 1-69 and secondary transfectant 17(2) but not to NIH 3T3 plasma membranes. Immunoperoxidase staining confirmed this binding pattern and demonstrated that the antigen was expressed on the cell surface. Expression of the antigen by transfectants directly correlated with the presence of a single 6.1 kilobase human DNA sequence. The antibody binding site of the antigen was inactivated by trypsin, glucosidase, and hyaluronidase. Binding of the 17-9H3 antibody was selective for acute lymphocytic leukemias (5/8) and osteogenic sarcomas (33/36), although other tumor types did demonstrate significant binding by immunoperoxidase staining. The majority of normal tissues did not bind 17-9H3 with the exception of some metabolically active cells (renal tubular epithelium, secretory epithelial cells, and cardiac smooth muscle), germ cells, Leydig cells of the testes, and some lymphoid cells. Monoclonal antibodies to oncogene-associated antigens may be potentially useful for cancer diagnosis and therapy and as probes for oncogene isolation.