Association between metalloproteinases 2 and 9 activity and ERK1/2 phosphorylation status in head and neck cancers: an ex vivo study

Advances in clinical treatment of head and neck squamous cell carcinoma (HNSCC) are hampered by its high infiltrative potential leading to distal metastasis. Since their ability to degrade the basal lamina and extracellular matrix, matrix metalloproteinases (MMP) have a pivotal role in tumor invasion. The overexpression and the aberrant activity of MMPs especially of MMP2 and MMP9, during HNSCC development and progression have been reported. However, up to now little is known about the mechanism of their regulation in HNSCC. It has been demonstrated that MMP2/9 expression is negative regulated by extracellular signal regulated kinase 1 and 2 (ERK1/2) in HNSCC cell lines. ERKs are protein kinases belonging to the mitogen-activated protein kinases family, and they are involved in the regulation of different cellular aspects, from apoptosis to cell proliferation and differentiation. In the present study we evaluated MMP2 and MMP9 activity by gelatine zymography in 16 tissue samples of HNSCC and their paired normal mucosa from patients undergoing surgical treatment. Moreover, ERK1/2 activation was analyzed by immunoblotting. A statistically significant decrease in the levels of activated ERK2 in cancer specimens in comparison with paired normal tissues was observed, whereas a significant increase in the activity of MMP2 was found in cancer specimens. However, the statistical analysis failed to demonstrate a correlation between the increase in MMP2 activity and the reduction of ERK1/2 activation levels. The results obtained, therefore, rule out, for the first time in an ex vivo study, the existence of a negative correlation between ERK1/2 activation and MMP2 activity.