EXPRESSION OF MEMBRANE-TYPE MATRIX METALLOPROTEINASE-1 IN HUMAN PANCREATIC ADENOCARCINOMAS

The expression of a new type of matrix metalloproteinase, membrane-typ e matrix metalloproteinase-1 (MT-MMP-1), was examined in 24 cases of p rimary pancreatic adenocarcinomas and 9 cases of secondary liver tumor s derived from pancreatic adenocarcinomas, using a non-radioactive in situ hybridization and immunohistochemical methods. Out of 24 cases of primary pancreatic adenocarcinomas, 18 showed positive expression of MT-MMP-1 transcripts in cancer cells and 20 of 24 showed positive expr ession in the tumor stromal cells. The immunoreactivity of the gene pr oducts for MT-MMP-1 was demonstrated to be almost the same, as shown b y in situ hybridization in these 24 cases. In particular, both the sta ining intensity for MT-MMP-1 transcripts and the immunoreactivity of t he gene products in the tumor stromal cells of mucinous cystadenocarci nomas were significantly weaker than those of common-type ductal adeno carcinomas among the 24 cases. All of the 9 cases of secondary liver t umors derived from pancreatic adenocarcinomas showed positive expressi on for MT-MMP-1 transcripts but less immunoreactivity for the gene pro ducts. These results suggest that MT-MMP-1 is transcribed and translat ed in both cancer cells and the tumor stromal cells in human pancreati c adenocarcinomas. Furthermore, considering that common-type ductal ad enocarcinoma of the pancreas usually shows a strong desmoplastic react ion, while mucinous cystadenocarcinoma typically does not, MT-MMP-1 ex pressed in the tumor stromal cells of common-type adenocarcinomas may be involved in processes leading to the desmoplastic reaction.