Enzyme Linked to Immune Suppression in Cancer

Many tumors exhibit increased incorporation of sialic acids into cell-surface glycans, which impact the tumor microenvironment. Sialic acid immunoglobulin-like lectins (Siglec) are receptors that recognize sialic acids and modulate immune responses, including responses to tumors. 

Tumors need to evade the immune system to grow and spread, causing cancer. One of the ways tumor cells hide is by displaying proteins that tell immune cells that all is well. New cancer treatments, called checkpoint blockade therapies, work by telling T cells to ignore those protein markers and attack the cells, but the therapy doesn’t always work. 

New Study Results

In a study published in the journal Cancer Immunology Research, researchers found a link between an enzyme and immunosuppression in cancer. 

“There are tumors that do not respond to these therapies, indicating that they must have additional mechanisms to inhibit the immune response,” says Virginia Shapiro, Ph.D., co-leader of the Mayo Clinic Cancer Center Immunology Program. In the study, published in Cancer Immunology Research, Dr. Shapiro and her team demonstrate one of those mechanisms. In tumors that overexpress the enzyme, ST8Sia6, a function of macrophages, is altered to inhibit immune response.

According to Dr. Shapiro, some cancers with overexpression of ST8Sia6 correlate with a poor outcome. This enzyme boosts the body’s natural chemical reactions related to the assembly of glycoproteins. 

They found using a genetically engineered murine model of colon cancer that ST8Sia6 accelerated tumor generation, decreasing survival from 6 months to 67 days and that the expression of ST8Sia6 on tumors inhibits antitumor responses to accelerate tumor growth. 

The results of this study add more insights into how tumor cells can escape immune responses, which could help in the development of future targeted therapies for individual tumors. 


Sara Tiner. (2022, Jan 8). Science Saturday: Scientists link enzyme to immune suppression in cancer. Mayo Clinic, News Network. Retrieved from: 


David J. Friedman, et al. ST8Sia6 Promotes Tumor Growth in Mice by Inhibiting Immune Responses. Can Immun Res. 2021. Vol 9, Issue 8. DOI: 10.1158/2326-6066.CIR-20-0834 

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