Ovarian Cancer Cell Detachment and Multicellular Aggregate Formation Are Regulated by MT1-MMP: A Potential Role in Intra-Peritoneal Metastatic Dissemination

摘要

An early event in the metastasis of epithelial ovarian carcinoma is shedding of cells from the primary tumor into the peritoneal cavity, followed by diffuse intra-peritoneal (i.p.) seeding of secondary lesions. Anchorage-independent metastatic cells are present as both single cells and multi-cellular aggregates (MCAs), the latter of which adhere to and disaggregate on human mesothelial cell monolayers, subsequently forming invasive foci. While this unique metastatic mechanism presents a distinct set of therapeutic challenges, factors that regulate MCA formation and dissemination have not been extensively evaluated. Proteolytic activity is important at multiple stages in i.p. metastasis, catalyzing migration through the mesothelial monolayer and invasion of the collagen-rich sub-mesothelial matrix to anchor secondary lesions, and acquisition of membrane type 1 matrix metalloproteinase (MT1-MMP; MMP-14) expression promotes a collagen-invasive phenotype in ovarian carcinoma. MT1-MMP is regulated post-translationally through multiple mechanisms including phosphorylation of its cytoplasmic tail, and the current data using ovarian cancer cells expressing wild type, phospho-mimetic (T567E-MT1-MMP) and phospho-defective (T567A-MT1-MMP) MT1-MMP show that MT1-MMP promotes MCA formation. Confluent T567E-MT1-MMP-expressing cells exhibit rapid detachment kinetics, spontaneous release as cell-cell adherent sheets concomitant with MT1-MMP-catalyzed α3 integrin ectodomain shedding, and robust MCA formation. Expansive growth within 3-dimensional collagen gels is also MT1-MMP dependent, with T567E-MT1-MMP-expressing cells exhibiting multiple collagen invasive foci. Analysis of human ovarian tumors demonstrates elevated MT1-MMP in metastases relative to paired primary tumors. These data suggest that MT1-MMP activity may be key to ovarian carcinoma metastatic success by promoting both formation and dissemination of MCAs.