Expression of matrix metalloproteinases MMP-2, MMP-9 and their tissue inhibitors TIMP-1 and TIMP-2 in the epithelium and stroma of salivary gland pleomorphic adenomas.
The balance between matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) is involved in the morphogenesis of normal salivary gland as well as in the mechanisms of tumour invasion and metastasis. The role of MMPs and TIMPs in pleomorphic adenoma has not been elucidated sufficiently. Our aim was to analyse the mRNA and protein expression of MMP-2, MMP-9, TIMP-1 and TIMP-2 in the epithelium and stroma of pleomorphic adenoma and to evaluate their roles. In each sample from six patients, cells from the epithelium and stroma were obtained by laser microdissection. The mRNA expression of MMPs and TIMPs was determined by real-time quantitative reverse transcriptase-polymerase chain reaction and protein expression was confirmed by immunohistochemistry. Results showed that mRNA expression of MMPs and TIMPs was significantly higher in stroma than in epithelium in most patients. MMPs and TIMPs were immunoreactive mainly in epithelium rather than in stroma. Our results provide preliminary evidence that stromal myoepithelium may be the primary source of MMPs and that the stroma has the potential to play a more important role than ductal epithelium in biological behaviour of pleomorphic adenomas. These findings seem worthy of further investigation.