Excess sugar in the blood may help cancer cells avoid detection by the immune system, according to a study by scientists at the Sanford Burnham Prebys Medical Discovery Institute in California. The research suggests that cancer cells can build a thick layer of sugar-rich molecules, acting as a shield that makes it harder for immune cells to recognize them. This protective layer, called the glycocalyx, becomes even stronger in conditions of high blood sugar, known as hyperglycemia. The findings were published in the journal Science Advances. To understand how the tumor environment affects these protective layers, the researchers recreated different conditions in the lab. They grew cancer cells in environments that either mimicked the rigid conditions around primary tumors or the softer conditions of healthy tissues. They also used different culture media—some standard and others with a nutrient composition similar to the human body—and varied the glucose levels to simulate normal or high blood sugar. The results showed that these environmental differences influenced the proteins the cells produced, the levels of certain metabolites inside the cells, and the thickness of the glycocalyx on their surfaces. The glycocalyx is made up of chains of sugar molecules attached to proteins or lipids, forming a protective layer on the surface of cells. These sugar-protein or sugar-lipid structures are known as glycoconjugates. Because glucose is a key building block for these compounds, the researchers hypothesized that changes in glucose levels or hyperglycemia could affect the glycocalyx's structure. Their experiments confirmed this, showing that the presence of a protein called heat shock factor 1 (HSF1)—linked to cancer progression and metastasis—altered the glycocalyx's composition. However, hyperglycemia only strengthened the glycocalyx when HSF1 was present and the cells were in a tumor-like environment. The study suggests that targeting HSF1 could reduce the glycocalyx's thickness, weakening the protection that allows cancer cells to escape immune detection. This research is especially relevant given the rising prevalence of metabolic syndrome and type 2 diabetes, conditions often associated with hyperglycemia. These conditions are increasingly recognized as risk factors for cancer, making the findings particularly important for understanding how diet and metabolic health might influence cancer progression.