MMP9 and nasopharyngeal carcinoma: A single C > T nucleotide polymorphism at position −1562 within the gelatinase B/MMP-9 promoter, originally associated with coronary atherosclerosis [19], deregulates gelatinase B/MMP-9 expression and associates with gastric tumour progression [20], susceptibility to oral squamous cell carcinoma [21,22,23], nasopharyngeal carcinoma [24], squamous cell carcinoma of the lung [25] and oesophageal squamous cell carcinoma [26], and also associates with a higher risk of metastasis in the Asian, but not the European population [27].