(82c) Glycosylation Dynamically Tunes the Biophysical Properties of the Cancer Cell Glycocalyx

Muc1 is a large, heavily O-glycosylated membrane protein that is overexpressed in the majority of cancers and constitutes the major structural element of the cancer cell glycocalyx. While the biophysical properties of the glycocalyx directly regulate cell-ECM adhesion, cell-cell interactions, and receptor spatial organization, how these properties change dynamically during acquisition of a metastatic phenotype is largely unknown. To dissect the relationship among glycan biosynthesis, mucin rigidity, and the bulk properties of the cancer-specific glycocalyx, we isolated sub-populations of Muc1-expressing breast epithelial cells that present with distinct mucin glycophenotypes. Remarkably, alterations in glycosylation were associated with profound differences in glycocalyx structure, even in isogenic cell lines. In one stable glycophenotype, cellular mucins were highly rigid and mechanically disrupted integrin adhesion, resulting in complete dissociation of cells from the substrate. The cells exhibit striking and rapid 3D motility compared to wild-type cells without Muc1. On the other extreme, we isolated a stable population of cells that expresses high levels of Muc1, but these mucins were apparently flexible and had no observable effect on cell adhesion. In motility assays, the phenotype of the wild-type cells is recovered and, despite expressing similar protein levels of Muc1, cells show limited 3D motility. Based on lectin profiling, we identified specific patterns of Muc1 O-glycosylation associated with the two extremes in glycocalyx structures. Of notable significance, we discovered that metabolic reprogramming by the HRas oncogene could induce a glycophenotype consistent with mechanically rigid mucins. Future studies will identify the specific glycosylation machinery associated with the different glycophenotypes, with the hope of identifying new avenues of therapeutic intervention based on normalizing the mechano-phenotype of the cancer cell glycocalyx.