CD147 promotes invasion and MMP-9 expression through MEK signaling and predicts poor prognosis in hypopharyngeal squamous cell carcinoma

Hypopharyngeal cancer is one of the most frequent head and neck cancers and is associated with a poor prognosis because of recurrence and metastases. Therefore, there is a need to improve the prognosis, which requires the identification of prognostic factors and elucidation of the mechanisms involved in tumor progression. Accumulated evidence has demonstrated that cluster of differentiation 147 (CD147) is strongly expressed in malignant tumors, including head and neck squamous cell carcinoma (HNSCC), and contributes to tumor progression. To investigate CD147-induced signaling pathways in HNSCC cells to evaluate the mechanisms of tumor progression mediated by CD147, and the association between CD147 expression in tumors and the survival rate of hypopharyngeal cancer patients. To determine the downstream signaling of CD147 in HNSCC, expression levels of phosphorylated AKT1, MEK1, p38 MAPK, STAT3, and NF-κB were evaluated using enzyme-linked immunosorbent assay (ELISA) in FaDu, a hypopharyngeal cell line, exposed to cyclophilin A, a CD147 ligand. We found that hypopharyngeal cancer patients expressing CD147 showed a poor five-year overall survival (OS) of 11.1% compared with those without CD147 expression (43.0%) (p = 0.02). We confirmed that the expression of phosphorylated MEK and matrix metalloproteinase-9 (MMP-9), as well as cell invasion ability, were enhanced in hypopharyngeal cancer cells. In addition, this increased cell infiltration and enhancement of MMP-9 expression induced by CD147 were abolished by a MEK inhibitor. These results suggest that CD147 can be a predictor of a poor prognosis, and that a CD147-induced MEK-mediated intracellular signaling pathway plays a crucial role in tumor progression in hypopharyngeal carcinoma.