Dimeric Le(a) (Le(a)-on-Le(a)) status of beta-haptoglobin in sera of colon cancer, chronic inflammatory disease and normal subjects.

The glycosyl epitope dimeric Lea (Lea-on-Lea), defined by mouse monoclonal antibody NCC-ST-421, was identified previously as tumor-associated antigen, expressed highly in various human cancer tissues and cell lines derived therefrom, but with minimal expression in various normal tissues. In the present study, we observed clearly higher expression of this epitope, defined by ST421, in beta-haptoglobin (beta-Hap) from sera of patients with colorectal cancer, compared to normal, healthy subjects or patients with chronic inflammatory processes (Crohn's disease, ulcerative colitis). We focused, therefore, on biochemical characterization of glycosyl epitope status expressed in beta-Hap. We concluded that the dimeric Lea epitope is carried by O-linked but not by N-linked structure, based on the following observations: i) Treatment of beta-Hap with alpha-L-fucosidase reduced its reactivity with ST421, but did not affect its reactivity with anti-Hap antibody. In contrast, treatment of purified beta-Hap with PNGase F, which releases N-linked glycans, had no effect on reactivity with ST421, but changed molecular mass from 40 kDa to 30 kDa. ii) Strong reactivity of Colo205 supernatant with ST421 was reduced clearly by pre-incubation of cells with benzyl-alpha-GalNAc.

N-glycosylation status of beta-haptoglobin in sera of patients with colon cancer, chronic inflammatory diseases and normal subjects.

N-glycosylation status of purified beta-haptoglobin from sera of 17 patients, and from sera of 14 healthy volunteer subjects, was compared by blotting with various lectins and antibodies. Patients in this study were diagnosed as having colon cancer through histological examination of each tumor tissue by biopsy. Blotting index of serum beta-haptoglobin with Aleuria aurantia lectin (AAL) was clearly higher for cancer patients than for healthy subjects. No such distinction was observed for blotting with three other lectins and two monoclonal antibodies. To determine tumor-associated reactivity of AAL binding as compared to inflammatory processes in colonic tissues, beta-haptoglobin separated from sera of 5 patients with Crohn's disease (CD), and 4 patients with ulcerative colitis (UC), was studied. All these cases, except one case of UC, showed AAL index lower than that in cancer cases, similarly to healthy subjects. The higher AAL binding of beta-haptoglobin in colon cancer patients than in healthy subjects appeared to be due to alpha-L-fucosyl residue, since it was eliminated by bovine kidney alpha-fucosidase treatment. N-linked glycans of serum haptoglobin from colon cancer patients vs. healthy subjects were released by N-glycanase, fluorescence-labeled, and subjected to normal-phase high performance liquid chromatography (NP-HPLC). Glycan structures were determined based on glucose unit (GU) values and their changes upon sequential treatment with various exoglycosidases. Glycosyl sequences and their branching status of glycans from 14 cases of serum beta-haptoglobin were characterized. The identified glycans were sialylated or nonsialylated, bi-antennary or tri-antennary structures, with or without terminal fucosylation.