Different Forms of TFF2, A Lectin of the Human Gastric Mucus Barrier: In Vitro Binding Studies.

Trefoil factor family 2 (TFF2) and the mucin MUC6 are co-secreted from human gastric and duodenal glands. TFF2 binds MUC6 as a lectin and is a constituent of the gastric mucus. Herein, we investigated human gastric extracts by FPLC and identified mainly high- but also low-molecular-mass forms of TFF2. From the high-molecular-mass forms, TFF2 can be completely released by boiling in SDS or by harsh denaturing extraction. The low-molecular-mass form representing monomeric TFF2 can be washed out in part from gastric mucosa specimens with buffer. Overlay assays with radioactively labeled TFF2 revealed binding to the mucin MUC6 and not MUC5AC. This binding is modulated by Ca2+ and can be blocked by the lectin GSA-II and the monoclonal antibody HIK1083. TFF2 binding was also inhibited by Me-ß-Gal, but not the α anomer. Thus, both the α1,4GlcNAc as well as the juxtaperipheral ß-galactoside residues of the characteristic GlcNAcα1→4Galß1→R moiety of human MUC6 are essential for TFF2 binding. Furthermore, there are major differences in the TFF2 binding characteristics when human is compared with the porcine system. Taken together, TFF2 appears to fulfill an important role in stabilizing the inner insoluble gastric mucus barrier layer, particularly by its binding to the mucin MUC6.

GPER-1 expression decreases during breast cancer tumorigenesis.

GPER-1 protein expression was immunohistochemically examined in 164 primary breast cancer specimens and their matched normal breast epithelium. GPER-1 down-regulation correlated significantly with increased histological grading (p = .015), lymph node metastases (p = .032), and negative estrogen receptor status (p = .018). The decrease of GPER-1 expression in breast cancer tissue, relative to normal tissue, was associated with poor overall survival (p = .043) and disease-free survival (p = .037) and remained a significant unfavorable factor in multivariate analysis for DFS (HR = 1.569; 95% CI, 1.024-2.797; p = .041) and OS (HR = 2.082; 95% CI, 1.248-4.773; p = .039). Thus aberrant GPER-1 expression seems to be an important factor in breast cancer progression.