Sialic Acid Blockade Suppresses Tumor Growth by Enhancing T-cell-Mediated Tumor Immunity

• Published in: Cancer research (Chicago, Ill.) Vol. 78; no. 13; pp. 3574 - 3588
• Main Authors: Büll, Christian, Boltje, Thomas J, Balneger, Natasja, Weischer, Sarah M, Wassink, Melissa, van Gemst, Jasper J, Bloemendal, Victor R, Boon, Louis, van der Vlag, Johan, Heise, Torben, den Brok, Martijn H, Adema, Gosse J
• Format: Journal Article
• Language: English
• Published: United States American Association for Cancer Research, Inc 01-07-2018
• Subjects: Acids; Adoptive transfer; CD8 antigen; Cell activation; CpG islands; Cytotoxicity; Dendritic cells; Immunity; Immunomodulation; Immunosuppression; Lymphocytes; Lymphocytes T; Natural killer cells; Sialic acids; Sugar; T cell receptors; Tumor cells
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.CAN-17-3376

Sialic acid sugars on the surface of cancer cells have emerged as potent immune modulators that contribute to the immunosuppressive microenvironment and tumor immune evasion. However, the mechanisms by which these sugars modulate antitumor immunity as well as therapeutic strategies directed against them are limited. Here we report that intratumoral injections with a sialic acid mimetic Ac
3F
Neu5Ac block tumor sialic acid expression
and suppress tumor growth in multiple tumor models. Sialic acid blockade had a major impact on the immune cell composition of the tumor, enhancing tumor-infiltrating natural killer cell and CD8
T-cell numbers while reducing regulatory T-cell and myeloid regulatory cell numbers. Sialic acid blockade enhanced cytotoxic CD8
T-cell-mediated killing of tumor cells in part by facilitating antigen-specific T-cell-tumor cell clustering. Sialic acid blockade also synergized with adoptive transfer of tumor-specific CD8
T cells
and enhanced CpG immune adjuvant therapy by increasing dendritic cell activation and subsequent CD8
T-cell responses. Collectively, these data emphasize the crucial role of sialic acids in tumor immune evasion and provide proof of concept that sialic acid blockade creates an immune-permissive tumor microenvironment for CD8
T-cell-mediated tumor immunity, either as single treatment or in combination with other immune-based intervention strategies.
Sialic acid sugars function as important modulators of the immunosuppressive tumor microenvironment that limit potent antitumor immunity.
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