Roles of membrane type 1 matrix metalloproteinase and tissue inhibitor of metalloproteinases 2 in invasion and dissemination of human malignant glioma

Object Acquisition of invasive and metastatic potentials through proteinase expression is an essential event in tumor progression. Among proteinases, matrix metalloproteinases (MMPs) are thought to play a key role in tumor pr ogression through the degradation of the extracellular matrix. In the prese nt study, the authors examined the role of MMP-2 (gelatinase A) and membran e type I MMP (MT1-MMP), an activator of the zymogen of MMP-2, proMMP-2, tog ether with tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) in t he invasion of astrocytic tumors in humans. Methods. Analyses performed using sandwich enzyme immunoassays demonstrated that the production levels of proMMP-2 and TIMP-1, but not TIMP-2, are sig nificantly higher in glioblastomas multiforme than in other grades of astro cytic tumors. Quantitative reverse transcription-polymerase chain reaction indicated that MT1-MMP is expressed predominantly in glioblastoma tissues, and its expression levels are significantly enhanced as tumor grade increas es. In addition, the expression levels and proMMP-2 activation ratio were r emarkably higher in glioblastomas associated with cerebrospinal fluid (CSF) dissemination than in those not associated with CSF dissemination. In cont rast, an examination of TIMP-2 levels showed a reverse correlation. Like MT 1-MMP, TIMP-1 and TIMP-2 were immunolocalized to neoplastic cells in gliobl astoma samples. To study the roles of these molecules in the invasion of as trocytic tumors more fully, stable transfectants expressing the MT1-MMP gen e were developed in a U251 human glioblastoma cell line. The MT1-MMP transf ectants displayed prominent activation of proMMP-2 and invasive growth in t hree-dimensional collagen gel; however, mock transfectants and parental cel ls displayed noninvasive growth without the activation. The invasion and ge latinolytic activity of the transfectants were completely inhibited by addi tion of recombinant TIMP-2, but not recombinant TIMP-1. Conclusions. These results indicate that MT1-MMP may contribute to tumor in vasion and CSF dissemination of glio-blastoma cells on the basis of an imba lance of TIMP-2.