Colorectal tissue biopsies were obtained from 110 patients diagnosed with primary
colorectal carcinoma (
tumor and normal colonic mucosa samples), 20 patients diagnosed with benign colorectal disease, and 31 healthy donors. The level of expression of
tumor-associated
glycoprotein 72 (TAG-72) was quantitatively measured in each sample using a double-determinant RIA with
monoclonal antibodies B72.3 and CC49 and detecting the sialyl-Tn
epitope; this assay was termed CA 72-4. Statistical analysis revealed a significant (approximately 10-fold) increase of
TAG-72 expression in the colon
tumor biopsies when compared with the expression in normal colonic mucosa from the same patients. A regression analysis revealed a significant correlation (r = 0.459; P < 0.001) between
TAG-72 levels measured in biopsies from the
tumor lesions and those found in the corresponding normal colonic mucosa. Furthermore, regression analysis showed a significant positive correlation between
TAG-72 levels in the
tumors and sera of the same patients (r = 0.491; P < 0.001).
TAG-72 levels in normal colonic mucosa from healthy donors and patients diagnosed with
colorectal cancer were compared.
TAG-72 expression was 5-fold higher in the normal mucosa from the
colorectal carcinoma patients. No relationship between
TAG-72 tumor tissue content and stage of disease was found. Moreover, the correlation between
TAG-72 distribution and degree of
tumor differentiation observed (P < 0.05) was not any more evident when
mucinous carcinomas were excluded. Finally, the results provide further evidence that
TAG-72 may be considered an important early marker for
colorectal cancer and/or other dysplastic
colonic diseases. The statistical correlation between
TAG-72 levels in
tumors and circulating
TAG-72 indicates that patients with elevated levels of serum
TAG-72, as measured by the CA 72-4 assay, would be most suited for diagnostic and/or therapeutic intervention with the anti-TAG-72
monoclonal antibodies B72.3 or CC49 or
vaccine trials using the sialyl-Tn
epitope.