XBP1 induces MMP-9 expression to promote proliferation and invasion in human esophageal squamous cell carcinoma.

X-box binding protein 1 (XBP1) was found to be overexpressed in glioma and breast cancers, suggesting that XBP1 might act as a potent oncogenic protein. However, the clinical significance and biological role of XBP1 in esophageal squamous cell carcinoma (ESCC) remain unknown. In this study, we report that XBP1 is markedly overexpressed in ESCC cell lines and clinical samples. XBP1 overexpression was significantly correlated with ESCC tumor stage, lymph node metastasis and poor outcome. A functional study demonstrated that XBP1 promoted cell growth and cell invasion both in vitro and in vivo. Further study found that the XBP1-mediated invasion and proliferation of cancer cells requires the up-regulation of matrix metalloproteinase-9 (MMP-9). Importantly, a significant correlation between XBP1 and MMP-9 levels was observed in ESCC clinical samples. Our findings demonstrate that XBP1 is an oncogene that plays an important role in the development of ESCC by activating MMP-9 expression.