Mucins form a nanoscale physical barrier against immune cell attack.

Abstract

Cancer cells construct a glycocalyx with biochemical and physical attributes that protect against immune surveillance. Whether the structural properties of the glycocalyx also physically shield cancer cells from immune recognition has not been fully resolved. Here, we utilize an interference-based imaging technique called Scanning Angle Interference Microscopy (SAIM) to accurately measure the nanoscale physical dimensions of the cellular glycocalyx. Using glycoengineering strategies and SAIM, we reveal how the surface density, glycosylation, and crosslinking of cancer-associated mucins contribute to the nanoscale material thickness of the glycocalyx, and further analyze the effect of the glycocalyx thickness on resistance to effector cell attack. We uncovered a strong reciprocal relationship between the thickness of the glycocalyx and immune cell killing. Natural Killer (NK) cell-mediated cytotoxicity exhibits a nearly perfect inverse correlation with the glycocalyx thickness of target cells regardless of the specific glycan structures present, suggesting that the physical properties of glycocalyx may be key determinants of cancer immune evasion. Changes in glycocalyx thickness as small as 10 nanometers can significantly alter susceptibility to immune cell attack. We further suggest strategies for overcoming the glycocalyx physical barrier through the cellular engineering of immune cells. These strategies include the surface display of glycocalyx-editing enzymes on the NK surface for improved penetration of the glycocalyx barrier.