MMP13 and nasopharyngeal carcinoma: We further confirmed our microarray results using quantitative RT-PCR, and found that the mRNA levels of MMP1, MMP12, MMP13 and MMP28 were significantly reduced (to 0.77-, 0.28-, 0.46- and 0.09-fold, respectively; P < 0.05) in hnRNP K-knockdown cells compared with control siRNA-treated NPC-TW02 cells (Figure 1B).