ROLE OF PLASMINOGEN ACTIVATORS, METALLOPROTEINASES AND THE TISSUE INHIBITOR OF METALLOPROTEINASE-1 IN THE METASTATIC PROCESS OF HUMAN SALIVARY-GLAND ADENOCARCINOMA CELLS

An in vitro system has been established in which conversion from non-m etastasizing to metastasizing adenocarcinoma cells can be induced, and subsequently subjected to analysis of the expression of proteases and tissue inhibitor of metalloproteinases-I (TIMP-1). A human salivary-g land adenocarcinoma cell clone HSGc, with no metastatic ability, was e xposed to N-methyl-N-nitrosourea (MNU). Following exposure to MNU, cel ls with altered morphology were cloned. Upon s.c. inoculation into nud e mice, MNU-treated HSGc clones formed metastatic foci in various orga ns, and then 5 metastasizing clones were isolated. Evaluation of expre ssion of tissue-type plasminogen activator (tPA), urokinase-type plasm inogen activator (uPA), metalloproteinases and TIMP-1 was performed by means of enzyme immunoassay, zymogram, or immunoblot. MNU-treated HSG c and metastasizing clones were found to secrete high levels of tPA, w hile HSGc produced undetectable levels of this enzyme. Expression of u PA was not observed in any of the cell clones. When the secretion of g elatinolytic enzymes was examined, metastasizing clones produced highe r levels of S7- and 32-kDa, but not of 92- or 72-kDa gelatinases, as c ompared to HSGc cells. Although TIMP-1 was detected in all cell clones , metastasizing clones secreted less TIMP-1 than HSGc cells; in additi on, one metastasizing clone produced TIMP-1 with a molecular weight di stinct from that of 28-kDa TIMP-1. Our results suggest that the acquis ition of metastatic ability by human salivary-gland tumor cells is clo sely associated with increased secretion of several metalloproteinases as well as decreased or altered TIMP-1 expression. (C) 1993 Wiley-Lis s, Inc.