Plasma sialyl transferase total and isoenzyme activity in the diagnosis of cancer of the colon.

Total plasma sialyltransferase (ST) activity was elevated in patients with colonic adenocarcinoma; the incidence of abnormal values ranged from 33% in patients with no evidence of metastases (T2N0M0) to 86% in patients with advanced metastatic disease (T2-5N1M1). Isoenzyme analysis revealed that normal serum contains a major band (ST2) probably derived from red cells, and a minor band (ST1) thought to be derived from platelets. An additional band, designated STN, intermediate in mobility between the two other bands, was found in patients with colonic adenocarcinoma, ranging in incidence from 50% to 86% in patients free of metastases and those with widespread metastases. Histological studies suggested that this abnormal isoenzyme was more likely to occur in the serum of patients whose tumor was well differentiated.