Detection of tumor-associated antigens in sera of canine cancer patients by monoclonal antibodies generated against canine mammary carcinoma cells

Two murine monoclonal antibodies (MAbs), 1A10 and SB2, generated against a canine mammary carcinoma cell line, were used in a competitive enzyme-linked immunosorbent assay (ELISA) to measure tumor-associated antigens (TAAs) in canine serum samples. Sera were tested from disease-free dogs and from dogs diagnosed with mammary carcinoma, non-mammary carcinoma, sarcoma, benign mammary tumor, benign non-mammary tumor, or non-neoplastic disease. Serum antigen concentrations measured by ELISA were expressed as inhibitory units (IU). The upper limit of normal, defined as the mean plus 2 SD of the TAA concentration in disease-free dogs, was 20 IU with antibody 1A10 and 22 IU with antibody SB2. Compared with disease-free dogs, the frequency of TAA-positive sera was significantly greater (P < 0.05) among dogs with mammary or non-mammary carcinoma when tested with MAbs 1A10 or SB2, and also with sarcoma when tested with MAb SB2. Testing a serum sample with both antibodies rather than just one increased the sensitivity of the competitive ELISA for TAA detection. The presence of TAA in serum might serve as a useful marker for certain types of carcinomas or sarcomas in canine cancer patients.