MUC1 mucin core
protein contains an important
tumor-associated
peptide antigen that can induce cytotoxic T cells (CTLs) in vivo, although this
antigen is generally masked by
mucin-type
glycans. To reveal the precise expression pattern of MUC1
protein in normal and neoplastic gastric tissues, we performed immunohistochemical staining of
periodic acid-treated tissue sections with an anti-MUC1 core
protein monoclonal antibody (mAb), MUSE11. In non-cancerous tissues, the deep portion of fundic glands and the
luminal surface were predominantly immunostained in normal and metaplastic glands, respectively. In cancerous tissues, the incidence of positivity for MUC1
protein varied from 67% to 88%, depending on histological type. This frequent expression of MUC1
protein in
cancer tissues after
periodic acid treatment suggested that deglycosylation may be of use for exposing the target
antigen of anti-MUC1 CTLs. Accordingly, we then examined the effect of
benzyl-alpha-GalNAc, an inhibitor of O-
glycan biosynthesis, on the expression of MUC1
protein and sensitivity to an anti-MUC1 CTL line, designated TS, in
gastric cancer JRST cells. After incubation with
benzyl-alpha-GalNAc, the reactivity of mAb MUSE11 with JRST cells and their sensitivity of TS were clearly increased. These findings suggest that deglycosylation may offer an important strategy for enhancing anti-
tumor immunity in patients with
gastric cancer.