Phenotypic heterogeneity of a tumor-associated antigen in adenocarcinomas of the colon and their metastases as demonstrated by monoclonal antibody B72.3.

To determine the potential antigenic heterogeneity which might exist between a primary colon carcinoma lesion and its metastases, we stained the formalin and Zenker's fixed paraffin-embedded tissues from the resection specimens of 12 patients with Duke's Stage C adenocarcinoma of the colon with monoclonal antibody (MAb) B72.3. This MAb previously has been shown to react with a high molecular weight tumor-associated glycoprotein (termed TAG-72), which is selectively expressed in adenocarcinomas versus normal adult tissue. Five to 90% of malignant cells from all primary lesions stained with MAb B72.3 in paraffin-embedded tissue. A significantly diminished percentage of cells stained from the metastases in lymph nodes and distant sites. Pearson correlation coefficients showed that the antigenic expression of the metastasis in the lymph node was a better indicator of the antigenic expression of the metastasis in the distal site than was the primary lesion in the colon. These findings suggest that the effective use of monoclonal antibodies for diagnostic imaging or therapeutic purposes may require the evaluation of the antigenic expression in regional node metastases rather than that of the primary lesion.