To investigate whether hyaluronan (HA), a ligand for the transmembrane receptor CD44, and CD44, which acts through multiple signaling pathways to influence cellular behavior, promote Rho kinase– and phosphatidylinositol 3 (PI-3) kinase–mediated oncogenic signaling to alter cisplatin sensitivity and stimulate tumor cell proliferation, migration, and matrix metalloproteinase secretion in head and neck squamous cell carcinoma (HNSCC).
Laboratory investigation using the HNSCC cell line HSC-3.
Main Outcome Measures
Rho kinase and PI-3 kinase activity, myosin phosphatase and AKT phosphorylation, tumor cell growth, migration, and matrix metalloproteinase secretion were measured in the presence or absence of HA, cisplatin, and inhibitors of Rho kinase and PI-3 kinase.
The addition of HA, but not HA plus anti-CD44 antibody, resulted in increased Rho kinase and PI-3 kinase activity. Results of immunoblotting studies demonstrated that HA promotes Rho kinase–mediated myosin phosphatase phosphorylation and PI-3 kinase–mediated AKT phosphorylation. Hyaluronan was shown to promote migration and increased matrix metalloproteinase secretion through Rho kinase–mediated signaling. Hyaluronan treatment promoted increased tumor proliferation and resulted in a 12-fold reduced ability of cisplatin to cause HNSCC cell death. On the other hand, the presence of Y-27632, a Rho kinase inhibitor, and LY-294002, a PI-3 kinase inhibitor, blocked HA-mediated cisplatin resistance by HNSCC.
Our results suggest that HA and CD44 promote Rho kinase– and PI-3 kinase–mediated oncogenic signaling and cisplatin resistance. Perturbation of HA-CD44–mediated Rho kinase and PI-3 kinase signaling pathways may be a novel strategy to treat HNSCC.