MetaboLights
A L-threonine derivative that is N-acetyl-alpha-D-galactosamine linked via an alpha glycosidic bond to the O at position 3 of L-threonine.
Identification
O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-L-threonine
3-O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-L-threonine
alpha-D-GalNAc-Thr
GalNAc(alpha1->O)Thr
GalNac-alpha-1-O-threonine
GalNAcalpha-O-Thr
N-acetyl-alpha-D-galactosaminyl-1-O-threonine
O-[2-(acetylamino)-2-deoxy-alpha-D-galactopyranosyl]-L-threonine
Tn antigen
Species
Europe PubMed Central results
Synthesis of a single-molecule L-rhamnose-containing three-component vaccine and evaluation of antigenicity in the presence of anti-L-rhamnose antibodies.
Author: Sarkar S, Lombardo SA, Herner DN, Talan RS, Wall KA, Sucheck SJ.
Abstract: Carbohydrates are generally considered to be poorly immunogenic. Therefore, new approaches for enhancing their immunogenicity are important for the development of carbohydrates as vaccine components. We hypothesized that conjugation of an l-rhamnose (Rha) moiety to a carbohydrate antigen would enhance the antigenicity of the antigen in mice possessing anti-Rha antibodies via an antibody-dependent antigen uptake mechanism. To explore this hypothesis, we synthesized a single-molecule three-component vaccine containing the GalNAc-O-Thr (Tn) tumor-specific antigen, a 20 amino acid helper T-cell epitope (YAF) derived from an outer-membrane protein of Neisseria meningitides, and a Rha moiety. The vaccine was synthesized by automated Fmoc-based solid-phase peptide synthesis and deacetylated by brief treatment with NaOMe. Groups of female BALB/c mice were immunized and boosted with Rha-ovalbumin (Rha-OVA) formulated with either TiterMax Gold or Sigma Adjuvant System for a period of 35 days in order to determine optimal conditions for generating anti-Rha titers in mice. Anti-Rha antibody titers were >100 fold higher in groups of mice immunized with Rha-OVA than in the control groups. Mice producing anti-Rha were challenged with Rha-YAF-Tn or YAF-Tn. Sera collected from the groups initially immunized with Rha-OVA and later challenged with Rha-YAF-Tn showed a 2-fold increase in anti-Tn titer at 1/100 serum dilution relative to mice not immunized with Rha-OVA. An in vitro T-cell proliferation study using cells primed with either Rha-YAF-Tn or YAF-Tn was done to examine possible differences in antigen uptake and presentation due to anti-Rha antibody and chemical modification. Proliferation of T cells was stimulated by a 10-fold lower antigen concentration in the presence of Rha antibodies. The results strongly suggest that T cells present in the spleen were presented with higher concentrations of Rha-YAF-Tn as a result of the presence of the anti-Rha antibodies.
DOI: 10.1021/ja107029z
Tn Antigen Expression Contributes to an Immune Suppressive Microenvironment and Drives Tumor Growth in Colorectal Cancer.
Author: Cornelissen LAM, Blanas A, Zaal A, van der Horst JC, Kruijssen LJW, O'Toole T, van Kooyk Y, van Vliet SJ.
Abstract: Expression of the tumor-associated glycan Tn antigen (αGalNAc-Ser/Thr) has been correlated to poor prognosis and metastasis in multiple cancer types. However, the exact mechanisms exerted by Tn antigen to support tumor growth are still lacking. One emerging hallmark of cancer is evasion of immune destruction. Although tumor cells often exploit the glycosylation machinery to interact with the immune system, the contribution of Tn antigen to an immunosuppressive tumor microenvironment has scarcely been studied. Here, we explored how Tn antigen influences the tumor immune cell composition in a colorectal cancer (CRC) mouse model. CRISPR/Cas9-mediated knock out of the <i>C1galt1c1</i> gene resulted in elevated Tn antigen levels on the cell surface of the CRC cell line MC38 (MC38-Tn<sup>high</sup>). RNA sequencing and subsequent GO term enrichment analysis of our Tn<sup>high</sup> glycovariant not only revealed differences in MAPK signaling and cell migration, but also in antigen processing and presentation as well as in cytotoxic T cell responses. Indeed, MC38-Tn<sup>high</sup> tumors displayed increased tumor growth <i>in vivo</i>, which was correlated with an altered tumor immune cell infiltration, characterized by reduced levels of cytotoxic CD8<sup>+</sup> T cells and enhanced accumulation of myeloid-derived suppressor cells. Interestingly, no systemic differences in T cell subsets were observed. Together, our data demonstrate for the first time that Tn antigen expression in the CRC tumor microenvironment affects the tumor-associated immune cell repertoire.
Tn Antigen Expression Defines an Immune Cold Subset of Mismatch-Repair Deficient Colorectal Cancer.
Author: Matsumoto T, Okayama H, Nakajima S, Saito K, Nakano H, Endo E, Kase K, Ito M, Yamauchi N, Yamada L, Kanke Y, Onozawa H, Fujita S, Sakamoto W, Saito M, Saze Z, Momma T, Mimura K, Kono K.
Abstract: Colorectal cancer (CRC) cells often express Tn antigen, a tumor-associated truncated immature O-glycan (GalNAcα-O-Ser/Thr) that can promote tumor progression. Immunotherapies against Tn antigen have been developed and are being evaluated in clinical trials. Tn antigen can also be considered a novel immune checkpoint that induces immunosuppressive signaling through glycan-biding lectins to lead effector T cell apoptosis. We evaluated the correlation of Tn antigen expression by immunohistochemistry with mismatch-repair (MMR) status, tumor-infiltrating lymphocytes, tumor cell PD-L1 expression, and clinicopathological characteristics in 507 CRC patients. Although 91.9% of CRCs showed negative or weak Tn antigen staining (Tn-negative/weak), we identified a small subset of CRCs (8.1%) that displayed particularly intense and diffuse distribution of Tn antigen immunoreactivity (Tn-strong) that closely related to deficient MMR (dMMR). Moreover, 40 dMMR CRCs were stratified into 24 Tn-negative/weak dMMR tumors (60.0%) exhibiting dense CD8+ lymphocyte infiltrate concomitant with a high rate of PD-L1 positivity, and 16 Tn-strong dMMR tumors (40.0%) that demonstrated CD8+ T cell exclusion and a lack of PD-L1 expression, which was comparable to those of proficient MMR. Our finding suggests that the immune cold subset of patients with Tn-strong dMMR CRC may be effectively treated with immune checkpoint blockade therapy or cellular immunotherapy targeting Tn antigen.
DOI: 10.3390/ijms21239081
Development of α-Selective Glycosylation for the Synthesis of Deoxyfluorinated T<sub>N</sub> Antigen Analogues.
Author: Kurfiřt M, Lucie ČŠ, Cuřínová P, Hamala V, Karban J.
Abstract: The Tn antigen (GalNAcα1-Thr/Ser) is abundantly expressed in many tumors but rarely found in healthy tissues, which makes it an attractive epitope for antitumor immunotherapy. The use of the Tn antigen in the development of therapeutic antitumor vaccines is hampered by its low immunogenicity, which may be enhanced by deoxyfluorination of the GalNAc moiety. Here, we report the synthesis of protected 3- and 4-fluoro analogues of the threonine-containing Tn antigen. As the stereoselective synthesis of α-linked fluorinated GalNAc is difficult, we prepared a panel of C3 and C4 deoxyfluorinated galactosazide thiodonors and evaluated their stereoselectivity in the glycosylation of carbohydrate acceptors and threonine derivatives. Glycosylation of threonine derivatives with <i>O</i>-benzylated C4 fluoro donors gave only modest but usable α-selectivity of α/β = 2.5-3/1. The use of acyl and silyl protection at the 3- and 6-positions of the C4 fluoro donors did not enhance the selectivity. Installing a 4,6-di-<i>tert</i>-butylsilylene-protecting group in C3 fluoro donors resulted in exclusive α-selectivity and reaffirmed the strong α-directing effect of this protective group in glycosylation with galacto-configured glycosyl donors.
Structure-based Design of Anti-cancer Vaccines: The Significance of Antigen Presentation to Boost the Immune Response.
Author: Asín A, García-Martín F, Busto JH, Avenoza A, Peregrina JM, Corzana F.
Abstract: Immunotherapy, alone or in combination with other therapies, is widely used against cancer. Glycoprotein Mucin 1 (MUC1), which is overexpressed and aberrantly glycosylated in tumor cells, is one of the most promising candidates to engineer new cancer vaccines. In this context, the development of stable antigens that can elicit a robust immune response is mandatory. Here, we describe the design and in vivo biological evaluation of three vaccine candidates based on MUC1 glycopeptides that comprise unnatural elements in their structure. By placing the Tn antigen (GalNAcα-O-Ser/Thr) at the center of the design, the chemical modifications include changes to the peptide backbone, glycosidic linkage, and carbohydrate level. Significantly, the three vaccines elicit robust immune responses in mice and produce antibodies that can be recognized by several human cancer cells. In all cases, a link was established between the conformational changes induced by the new elements in the antigen presentation and the immune response induced in mice. According to our data, the development of effective MUC1-based vaccines should use surrogates that mimic the conformational space of aberrantly glycosylated MUC1 glycopeptides found in tumors.