Our previous studies showed that expression of the GalNAcbeta1-->4GlcNAc group on N-linked
oligosaccharides is associated with functional differentiation of the bovine mammary gland. In the present study, the occurrence of the GalNAcbeta1-->4GlcNAc group was established in human milk
proteins and
membrane glycoproteins from a human
breast cancer cell line, MRK-nu-1, by structural analysis of
oligosaccharides released by hydrazinolysis. Whether the expression level of the
disaccharide group is affected upon malignant transformation was examined in human
breast cancer specimens using
Wistaria floribunda agglutinin (WFA) which interacts with
oligosaccharides with N-
acetylgalactosamine at their termini.
Lectin blot analysis of
membrane glycoprotein samples from human
breast cancer specimens showed that the number of
protein bands reacting with WFA, as well as their intensities, are lower in samples from primary
carcinoma lesions compared with samples from surrounding normal tissues. No
lectin binding was observed when the blots were treated with jack bean
beta-N-acetylhexosaminidase or
N-glycanase, indicating that WFA-reactive
oligosaccharides are N-linked. A histochemical study of tissue specimens from 92 patients with
breast cancer revealed that the reduced WFA staining levels in primary
carcinoma lesions correlate with advancing clinical stages and prognostic status (i.e., 58% of patients in a group showing reduced/negative staining died of disease recurrence, whereas more than 90% of those in the positive staining group survived for 5 years after surgery). These results indicate that reduced expression of beta-N-acetylgalactosaminylated N-linked
oligosaccharides on primary
carcinoma lesions predicts a poor prognosis for patients with
breast cancer.