CD44-mediated adhesion to hyaluronic acid contributes to mechanosensing and invasive motility.

UNLABELLED: The high-molecular-weight glycosaminoglycan, hyaluronic acid (HA), makes up a significant portion of the brain extracellular matrix. Glioblastoma multiforme (GBM), a highly invasive brain tumor, is associated with aberrant HA secretion, tissue stiffening, and overexpression of the HA receptor CD44. Here, transcriptomic analysis, engineered materials, and measurements of adhesion, migration, and invasion were used to investigate how HA/CD44 ligation contributes to the mechanosensing and invasive motility of GBM tumor cells, both intrinsically and in the context of Arg-Gly-Asp (RGD) peptide/integrin adhesion. Analysis of transcriptomic data from The Cancer Genome Atlas reveals upregulation of transcripts associated with HA/CD44 adhesion. CD44 suppression in culture reduces cell adhesion to HA on short time scales (0.5-hour postincubation) even if RGD is present, whereas maximal adhesion on longer time scales (3 hours) requires both CD44 and integrins. Moreover, time-lapse imaging demonstrates that cell adhesive structures formed during migration on bare HA matrices are more short lived than cellular protrusions formed on surfaces containing RGD. Interestingly, adhesion and migration speed were dependent on HA hydrogel stiffness, implying that CD44-based signaling is intrinsically mechanosensitive. Finally, CD44 expression paired with an HA-rich microenvironment maximized three-dimensional invasion, whereas CD44 suppression or abundant integrin-based adhesion limited it. These findings demonstrate that CD44 transduces HA-based stiffness cues, temporally precedes integrin-based adhesion maturation, and facilitates invasion. IMPLICATIONS: This study reveals that the CD44 receptor, which is commonly overexpressed in GBM tumors, is critical for cell adhesion, invasion, and mechanosensing of an HA-based matrix. ©2014 American Association for Cancer Research.