Abnormal expression of FAK and paxillin correlates with oral cancer invasion and metastasis

Globally, the tenth most common cancer is the oral squamous cell carcinoma (OSCC) and the treatment strategy for improving of OSCC patients survival rate still remains a challenging one. Aberrant regulation of cell to extracellular matrix protein interactions leads to progression of human cancers. The focal adhesion kinase (FAK) and its downstream target paxillin have been implicated in cancer growth, migration, invasion and metastasis of different cancers. However, the clinical significance of FAK and paxillin in OSCC is not well characterized so far. In the present work, we showed that relative mRNA and protein expressions of FAK and paxillin are significantly higher in side population (SP) cells of OSCC cell line SCC-55. Concomitantly, the matrix metalloproteinase-11 (MMP-11) level is also significantly elevated in SP cells. The enhanced expression of paxillin is strongly correlated with increased chemoresistance, proliferation rate, migration and invasion potential of SP cells. In addition, inhibition of paxillin expression by RNAi makes SP cells more sensitive to chemotherapy drugs. Therefore, our results suggest that paxillin over expression might play a significant role in cancer progression, invasion and chemoresistance of OSCC.