title: Enhanced self-association of mucins possessing the T and Tn carbohydrate cancer antigens at the single-molecule level.
abstract: Mucins are linear O-glycosylated glycoproteins involved in inflammation, cell adhesion, and tumorigenesis. Cancer-associated mucins often possess increased expression of the T (Galβ1,3GalNAcαThr/Ser) and Tn (GalNAcαThr/Ser) cancer antigens, which are diagnostic markers for several cancers, including colon cancer. We have used AFM based single-molecule forced unbinding under near physiological conditions to investigate the self-interactions between porcine submaxillary mucin (PSM) as well as between PSM analogs possessing various carbohydrates including the T- and Tn-antigen. Distributions of unbinding forces and corresponding force loading rates were determined for force loading rates from 0.18 nN/s to 39 nN/s, and processed to yield most probable unbinding forces f* and lifetimes of the interactions. Parameter f* varied in the range 27 to 50 pN at force loading rates of about 2 nN/s among the various mucins. All mucin samples investigated showed self-interaction, but the tendency was greatest for PSM displaying only the Tn-antigen (Tn-PSM) or a mixture of Tn-, T-antigen, and the trisaccharide Fucα1,2Galβ1,3GalNAc (Tri-PSM). Weaker self-interactions were observed for native PSM (Fd-PSM), which consists of a nearly equal mixture of the longer core 1 blood group A tetrasaccharide (GalNAcα1,3(Fucα1,2)Galβ1,3GalNAcαSer/Thr) and Tn-antigen. The data are consistent with the truncated Tn and T glycans enhancing self-interaction of the mucins. These carbohydrate cancer antigens may, thus, play an active role in the disease by constitutively activating mucin and mucin-type receptors by self-association on cells.
authors.affiliation: Biophysics and Medical Technology, Department of Physics, The Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
authors.forename: Kristin E
authors.initials: KE
authors.lastname: Haugstad
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Gerken
authors.forename: Bjørn T
authors.initials: BT
authors.lastname: Stokke
authors.forename: Tarun K
authors.initials: TK
authors.lastname: Dam
authors.forename: C Fred
authors.initials: CF
authors.lastname: Brewer
authors.forename: Marit
authors.initials: M
authors.lastname: Sletmoen
mesh_terms: D000818:Animals; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000737:chemistry*; D014408:Biomarkers, Tumor / Q000737:chemistry; D018625:Microscopy, Atomic Force; D009077:Mucins / Q000737:chemistry*; D013363:Submandibular Gland / Q000737:chemistry*; D013552:Swine
chemical_list: D015295:Antigens, Tumor-Associated, Carbohydrate; D014408:Biomarkers, Tumor; D009077:Mucins; C040286:Tn antigen; C016467:Thomsen-Friedenreich antigen