[Cancer-associated carbohydrate antigens available for serum diagnosis]

Many of the recently developed tumor antigens detected by monoclonal antibodies are sugar chains and frequently associated with blood group substance. By immunohistological studies, we evaluated mainly the clinical usefulness and significance of the serum assay of CA-50 classified as a type 1 sugar chain, sialyl SSEA-1 classified as a type 2 sugar chain, and ST-439 with an undetermined structure, as well as their clinicopathological significance. In addition, the value of measurement of CA 19-9 and ST-439 in pancreatic juice was studied. The incidence of serum CA-50 was highest in pancreatic cancer (86%) and biliary tract cancer (66%), but relatively low in benign diseases. Moreover, the positivity and specificity of CA-50 as a tumor marker were no less useful than those of CA 19-9. However, comparison of serum levels of CA-50 with those of CA 19-9 in the same samples revealed a highly positive correlation in malignant diseases. Thus, improvement of the diagnostic rate through a combination assay of CA-50 and CA 19-9 seems unlikely. Both serodiagnostic and immunohistological studies showed that sialyl SSEA-1 and ST-439 were highly specific for tumor, whereas their appearances in serum or tumor were lower than CA 19-9 or CA-50 carrying the type 1 sugar chain. In addition, an appreciable number of sialyl SSEA-1 or ST-439 positive patients were found among those negative for CA 19-9 or CA-50. These results indicate that assay of sialyl SSEA-1 or ST-439 improves the diagnostic rate in combination with CA 19-9 or CA-50. Although the concentration of CA 19-9 in pancreatic juice from pancreatic cancer patients was highest, it was also significantly higher in patients with chronic pancreatitis than in controls. Furthermore, the overlap between the values in patients with cancer and those with chronic pancreatitis was great. On the other hand, the concentration of ST-439 in pancreatic juice was significantly higher only in patients with pancreatic cancer. These results indicate that the measurement of ST-439 in pancreatic juice is more useful as a tumor marker than measurement of CA 19-9, and that moreover, the assay of CA 19-9 in pancreatic juice could be used as a sensitive marker for nonspecific pancreatic injury.