Matrix metalloproteinases (MMPs) play a crucial role in tumor invasion and metastasis. There have been only a few studies on the MMP expression in thyroid carcinomas. Therefore, we investigated the MMP9 expression in 66 papillary thyroid carcinomas (PTC) using immunohistochemistry and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) on protein level and mRNA level, respectively. We also examined the correlations between the immunohistochemical scores and several

more »

... ological parameters. The results demonstrated that MMP9 was significantly up-regulated in cancer tissue in comparison to begnin thyoid tumor tissue on mRNA level (P < 0.05). On protein level, MMP9 was also highly increased in cancer tissue in comparison to begnin thyoid tumor. It is found that high expression MMP9 proteins significantly correlated with large tumor size, presence of lymph node metastasis, Union Internationale Control Cancer (UICC) stage. These data suggest that MMP9 proteins are increased in tumors cells of PTC and that it plays an important role in the invasion and metastasis of PTC. Key words: Thyroid carcinomas, matrix metalloproteinase 9 (MMP9), quantitative reverse transcriptionpolymerase chain reaction (qRT-PCR), immunohistochemistry, papillary thyroid carcinomas.