Comparative studies on the expression of gastrointestinal-cancer-associated antigen, PA8-15, CA19-9 and the blood-group antigens in non-malignant and malignant human pancreatic tissues.

The expression of PA8-15 antigen and the blood-group-related antigens A, B, O, Le(a), Le(b), Le(x), and Le(y), as well as CA19-9, were examined in the normal pancreas and in specimens from benign and malignant pancreatic tissue by the avidin-biotin-immunoperoxidase technique. A correlation was found between the expression of PA8-15, Le(a), and CA19-9 in some cases. However, in the cancer tissues in which neither Le(a) nor CA19-9 could be demonstrated, strong expression of PA8-15 was observed. The reactivity of monoclonal antibody (mAb) PA8-15 with pancreatic cancer tissue was not inhibited by the preincubation of the sections with the mAb anti-Le(a) (CO514) and mAb CA19-9 (CO19-9) indicating that the epitope recognized by PA8-15 is different from that detected by the other two antibodies. Moreover, unlike Le(a) and CA19-9, PA8-15 was also expressed in cancer cells of patients of the Le(a-b-) type. The results suggest that mAb PA8-15 recognizes a sialylated molecule related to Le(a) but different from CA19-9, and seems to be an additional useful marker for pancreatic cancer.