The levels of
carbohydrate antigens having
epitopes consisting of type 1 chain (R----Gal beta 1----GlcNAc beta 1----3Gal beta 1----R) in the sera of patients with various malignant and nonmalignant disorders have been investigated with the use of three
monoclonal antibodies, N-19-9, FH-7, and FH-9. Serum levels of 2----3 sialylated Lea
antigen and 2----6 sialylated Lea
antigen, defined respectively by
antibodies N-19-9 and FH-7, were found to be frequently high in patients with
cancer of the digestive system, particularly
pancreatic cancer. High levels of 2----3,2----6 disialylated Lc4
antigen, defined by antibody FH-9, were less frequent in
cancer patients when compared with the other two
antigens. In patients with nonmalignant disorders, especially renal and
autoimmune diseases, serum levels of the two type 1 chain
antigens defined by FH-7 and FH-9 were more frequently high than that defined by N-19-9. Molecular weights and other general biochemical characteristics of serum
mucin carrying the type 1 chain determinants were not significantly different in
cancer patients as compared with patients with nonmalignant disorders. However, the degree of glycosylation of the
antigen, as assessed by its solubility in
perchloric acid, showed significant differences; i.e., the
mucin antigen carrying 2----6 sialylated Lea determinant in the sera of patients with nonmalignant disorders had the highest
carbohydrate/
protein ratio, followed by the
mucin carrying the same determinant in the sera of
cancer patients.
Mucin antigen carrying 2----3 sialylated Lea
antigen or 2----3, 2----6 disialylated Lc4
antigen in
cancer patients had the lowest
carbohydrate/
protein ratio among the four groups tested. Thus, the
carbohydrate/
protein ratio in the type 1 chain
mucin antigens in sera of normal subjects is higher than that in sera of
cancer patients (P less than 0.05). This finding is in contrast to previous findings on the
mucin antigens carrying the type 2 chain determinant (R. Kannagi et al.,
Cancer Res., 46: 2619-2626, 1986), in which the
mucin antigen in
cancer patients was found to have a much higher
carbohydrate/
protein ratio than that carrying the same
antigenic determinants in patients with nonmalignant disorders.