Hyaluronan and the interaction between CD44 and epidermal growth factor receptor in oncogenic signaling and chemotherapy resistance in head and neck cancer.

OBJECTIVES To investigate whether hyaluronan (HA) and CD44 (hereinafter HA-CD44) promotes head and neck squamous cell carcinoma (HNSCC) chemotherapy resistance and whether HA-CD44 promotes epidermal growth factor receptor (EGFR)-mediated oncogenic signaling to alter chemotherapy sensitivity in HNSCC. Hyaluronan, a glycosaminoglycan component of the extracellular matrix, is a ligand for the transmembrane receptor CD44, which acts through multiple signaling pathways to influence cellular behavior. We recently determined that HA-CD44 promotes phospholipase C-mediated calcium signaling and cisplatin resistance in HNSCC. DESIGN Cell line study. MAIN OUTCOME MEASURES Tumor cell growth with various chemotherapeutic drugs (methotrexate, doxorubicin hydrochloride, adriamycin, and cisplatin) was measured in the presence or absence of HA and other inhibitors of the EGFR-mediated signaling pathway. Immunoblotting was used to study EGFR signaling. Migration assays provided one measure of tumor progression. RESULTS The addition of HA, but not HA plus anti-CD44 antibody, resulted in a 2-fold reduced ability of methotrexate and an 8-fold reduced ability of adriamycin to cause HNSCC cell death. Immunoblotting studies demonstrated that HA can promote an association between CD44 and EGFR as well as CD44-dependent activation of EGFR-mediated signaling. Migration assays demonstrated that HA-CD44 can promote tumor migration with EGFR signaling. The presence of AG1478, an EGFR inhibitor, and U0126, an extracellular signal-regulated kinase inhibitor, inhibited HA-mediated tumor growth, migration, and chemotherapy resistance. CONCLUSIONS Our results indicate that HA promotes CD44/EGFR interaction, EGFR-mediated oncogenic signaling, and chemotherapy resistance in HNSCC. Perturbation of HA-CD44-mediated signaling may be a promising and novel strategy to treat HNSCC.