Expression of metastasis-associated mts1 gene is co-induced with membrane type-1 matrix metalloproteinase (MT1-MMP) during oncogenic transformation and tubular formation of Madin Darby canine kidney (MDCK) epithelial cells

Madin-Darby canine kidney (MDCK) epithelial cells form branching tubules in three-dimensional collagen gel in the presence of hepatocyte growth factor (HGF). Membrane type-1 matrix metalloproteinase (MT1-MMP), expression of which was induced by collagen-gel culture, was demonstrated to play an essential role in tubular formation (Y. Kadono et al. Biochem Biophys Res Commun 1998; 251: 681-7 [13]). Oncogenic transformation of MDCK cells by erbB2 and v-src induced expression of MT1-MMP, loss of cell-cell adhesion and scattered invasion into collagen gel. mRNA differential display and Northern hybridization identified metastasis-associated mts1 as one of the genes co-induced with MT1-MMP by oncogenic transformation or collagen-gel culture of MDCK cells. Expression of antisense RNA to mts1 in MDCK cells interfered with the extension of tubules into the collagen gel, however, it did not affect the morphological changes induced by HGF in culture on plastic dishes. ErbB2-transformant transfected with mts1 antisense construct, which showed unaltered morphology in culture on plastic dishes, did not scatter into collagen gel but formed aggregates. These results suggested that Mts1 contributes not only to tumor invasion but also to kidney tubulogenesis in cooperation with MT1-MMP. The coordinated action of MT1-MMP and Mts1, which is responsible for the highly invasive properties of mesenchymal cells, may be involved in epithelial tubulogenesis and invasion of malignant carcinoma cells.