Increased expression of MMP9 is correlated with poor prognosis of nasopharyngeal carcinoma

Introduction: The aim of the present study was to analyze the expression of matrix metalloproteinase 9 (MMP9) in nasopharyngeal carcinoma (NPC) and its correlation with clinicopathologic features, including the survival of patients with NPC. Methods: Using real-time PCR, we detected the mRNA expression of MMP9 in normal nasopharyngeal tissues and nasopharyngeal carcinoma (NPC) tissues. Using immunohistochemistry analysis, we analyzed MMP9 protein expression in clinicopathologically characterized 164 NPC cases (116 male and 48 female) with age ranging from 17 to 80 years (median = 48.4 years) and 32 normal nasopharyngeal tissues. Cases with greater than or equal to 6 and less than 6 of the score value of cytoplasmic MMP9 immunostaining were regarded as high expression and low expression, respectively. The relationship between the expression levels of MMP9 and clinical features was analyzed. Results: The expression level of MMP9 mRNA was markedly greater in NPC tissues than that in the nasopharyngeal tissues. Immunohistochemical analysis revealed that the protein expression of MMP9 detected in NPC tissues was higher than that in the nasopharyngeal tissues (P = 0.004). In addition, high levels of MMP9 protein were positively correlated with the status of lymph node metastasis (N classification) (P = 0.002) and clinical stage (P < 0.001) of NPC patients. Patients with higher MMP9 expression had a significantly shorter overall survival time than did patients with low MMP9 expression. Multivariate analysis suggested that the level of MMP9 expression was an independent prognostic indicator (P = 0.008) for the survival of patients with NPC. Conclusion: High level of MMP9 expression is a potential unfavorable prognostic factor for patients with NPC.