Nanometers matter in immune evasion mediated by the cellular glycocalyx

Cancer cells construct a glycocalyx with biochemical and physical attributes that protect against immune surveillance. While it has been proposed that the glycocalyx may form a nanoscale-thick barrier against immune cell attack, testing this possibility has proven difficult due to the challenges associated with imaging the ultrathin glycocalyx structure, particularly in live cells. In this talk, I will discuss how an imaging technique called Scanning Angle Interference Microscopy (SAIM) can be applied to accurately measure the nanoscale thickness of the cellular glycocalyx. Using SAIM and glycoengineering strategies, 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. Natural Killer (NK) cell-mediated cytotoxicity exhibits a near perfect inverse correlation with the glycocalyx thickness of target cells regardless of the specific glycan structures present. Changes in glycocalyx thickness as small as 10 nanometers can significantly alter susceptibility to immune cell attack. Finally, I will discuss strategies for overcoming the glycocalyx barrier through 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.