Killing cancer cells is tricky business, partly because they can be hard to find. Those tricky cells are good at hiding, but researchers are on to them. It seems their “invisibility cloak” is made up of a sugary coating that can now be detected.

The study, published in Science, shows that leukemia cells coat themselves in a slippery, sugar-coated protein called CD43. This shield makes it difficult for the body’s immune system to grab and destroy them.

When researchers removed the CD43, they found that immune cells were suddenly more adept at doing their job.

The sugar coating acts both as a barrier and a disguise — cancer cells are harder to reach, and the signals received by cells like macrophages, the body’s cleaning crew, says “don’t attack me.” This combination is what scientists are referring to as a glyco-immune barrier.

Notably, the barrier isn’t evading only one type of immune cell, it also interferes with natural killer cells and T cells, which are instrumental in fighting cancer.

The next step is for scientists is to figure out a way to strip away this sugary cloak at scale, which could make existing cancer treatments like immunotherapy more effective.

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