MMP-9 Knockdown Inhibits Oral Squamous Cell CarcinomaLymph Node Metastasis in the Nude Mouse Tongue-XenograftedModel through the RhoC/Src Pathway

Oral squamous cell carcinoma (OSCC) is one of the most common types of cancers in developing countries. A major contributor tothe high mortality rate of OSCC is the tendency of oral cancer cells to metastasize to lymph nodes around the head and neck duringthe early stages of cancer development. Matrix metall oproteinase 9 (MMP-9), an end opeptidase, can degrade the extracellularmatrix and basement membrane and plays a key role in tumor invasion and metastasis.In vitro, cell migration ability wasconducted by scratching assays. We also investigated the interaction abilities between OSCC cells and vascular endothelial cells(ECs) by an adhesion assay and transendothelial migration assay. an‎d we established a BALB/c nude mouse tongue-xenograftedmetastasis model to investigate the role of MMP-9 and explore its potential underlying mechanism in OSCC growth, lymphnode metastasis, and angiogenesisin vivo. The results showed that knockdown of MMP-9 could significantly suppress OSCCcell migration, proliferation, interactions between endothelial cells, xenografted tumor growth, and angiogenesis and simultaneously markedly inhibited OSCC cell metastasis to mouse lymphonodi cervicales superficiales, axillary lymph nodes,and even distant inguinal lymph nodes. Mechanistic studies revealed that knockdown of MMP-9 also led to a decreased expression of RhoC, Src, and F-actin by RT-PCR, western blotting, and immuno histochemistry. an‎d the bioinformatic analysisshowed that MMP-9, RhoC, and Src mRNA expression was positively and linearly correlated in OSCC on TCGA database.Together, ourfindings indicated that MMP-9 plays a very important role in OSCC growth, migration, angiogenesis, and lymphnode metastasis, and its potential mechanism may be mediated by RhoC and Src gene expression