Knockdown of Matrix Metallopeptidase 9 Inhibits Metastasis of Oral Squamous Cell Carcinoma Cells in a Zebrafish Xenograft Model

Abstract

Destruction of extracellular matrix (ECM) is one of the basic steps of tumor invasion and metastasis. Matrix metalloproteinase (MMP) 9, a kind of zinc-ion-dependent endopeptidase, can degrade almost all protein components in the ECM, destroy the histological barrier of tumor cell invasion, and play a key role in tumor invasion and metastasis. The role of MMP-9 in tumor invasion and metastasis has attracted increasing attention and is considered the main proteolytic enzyme in this process. Although the overexpression of MMP-9 was detected in Oral squamous cell carcinoma (OSCC) tissues, further basic studies <i>in vivo</i> and <i>in vitro</i> are needed to investigate the role of MMP-9 in OSCCs and provide scientific validation. In this research, we developed a novel OSCC zebrafish xenograft model to study the role of the MMP-9 gene in oral carcinogenesis. Firstly, the MMP-9/shRNA lentiviral clone and control virus were constructed and transfected into OSCC cells. Then, the decreasing expression of MMP-9 was verified by RT-PCR and immunocytochemistry. Cell proliferation was detected by MTT assay. Colony formation was evaluated by colony formation assay. Cell invasion was evaluated using transwell invasion assay <i>in vitro</i>. In addition, OSCC cells with MMP-9/shRNA knockdown and control vector were injected into zebrafish and an OSCC tumor model in zebrafish was established to evaluate invasion and metastasis <i>in vivo</i>. Knockdown of MMP-9 gene by shRNA could inhibit OSCC cell growth and clone formation and markedly suppress cell invasion <i>in vitro</i>. And the knockdown of the MMP-9 gene could also significantly decrease the metastatic distance and number of metastatic tumor cells or lesions <i>in vivo</i> and suppress the metastasis rate in xenografted zebrafish. Taken together, these evidences indicated that the knockdown of MMP-9 might suppress OSCC cell invasion and metastasis <i>in vivo</i> and <i>in vitro</i>. The MMP-9 gene may be a promising therapeutic target for OSCCs in the future.