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CD44-Associated Tn Antigen as a New Biomarker of Tumor Cells with Aberrant Glycosylation

M. L. Shuvalova1, A. T. Kopylov2, D. V. Mazurov1, A. V. Pichugin1, N. V. Bovin3, and A. V. Filatov1,4,a*

1Institute of Immunology National Research Center, Federal Medical and Biological Agency of Russia, 115522 Moscow, Russia

2 Orekhovich Institute of Biomedical Chemistry, 119121 Moscow, Russia

3Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia

4Department of Immunology, Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia

* To whom correspondence should be addressed.

Received June 30, 2020; Revised July 8, 2020; Accepted July 30, 2020
Tn antigen is a tumor-associated antigen that appears on cancer cells as a result of aberrant O-glycosylation. The most studied form of Tn antigen is found in mucins, in particular, in mucin 1 (MUC1). Antibodies against this form of Tn antigen are used to diagnose tumors, as well as to generate T-killers with a chimeric receptor. Some carcinomas do not carry MUC1 and antibodies of a different specificity are required to detect Tn antigen on these cells. In our work, we searched for anti-Tn antibodies without preliminary assumptions about the proteins that may be carriers of the Tn antigen. For this purpose, we obtained several pairs of isogenic cell lines with the wild type and knockout of the Cosmc gene, which is essential for correct protein O-glycosylation. Using the created lines as immunogens, we generated a monoclonal antibody AKC3, which reacted with the Cosmc-deficient A549 lung adenocarcinoma cells and did not bind to the wild-type cells. Using mass spectrometry, as well as co-immunoprecipitation, it was shown that the AKC3 antibody recognized the Tn antigen in the context of CD44 protein – a protein important for tumor growth. The AKC3 antibody can be used for tumor diagnosis, and to generate T cells with a chimeric receptor for treatment of tumors that do not express mucins.
KEY WORDS: Tn antigen, O-glycosylation, neoantigens, CD44, human lung adenocarcinoma

DOI: 10.1134/S0006297920090060