title: The microvesicle as a vehicle for EMMPRIN in tumor-stromal interactions.
abstract: EMMPRIN is a transmembrane glycoprotein expressed at high levels by tumor cells. It has been identified as a tumor-derived factor that can stimulate matrix metalloproteinase expression in fibroblasts and hence facilitate tumor invasion and metastasis. Recent studies have shown that full-length EMMPRIN is released by tumor cells, but the mechanism of release remains unclear. Here, we show that EMMPRIN is released from the surface of NCI-H460 cells via microvesicle shedding. However, these vesicles are unstable and rapidly break down to release bioactive EMMPRIN. Although microvesicle shedding has been considered a constitutive process in tumor cells, our data show that it can be amplified upon cell exposure to PMA, elucidating at least one signalling cascade responsible for EMMPRIN release. This pathway is dependent on protein kinase C, calcium mobilization and mitogen-activated protein kinase kinase (MEK 1/2). Thus, the results outline a novel form of tumor-stromal interaction in which extracellular matrix degradation by fibroblasts is controlled through the microvesicular release of EMMPRIN from tumor cells.
authors.affiliation: Biomolecular Sciences Program, Cardiovascular Research Institute and Department of Anatomy, UCSF, San Francisco, CA 94143, USA.
authors.forename: Sukhvinder S
authors.initials: SS
authors.lastname: Sidhu
authors.forename: Aklilu T
authors.initials: AT
authors.lastname: Mengistab
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Tauscher
authors.forename: Jennifer
authors.initials: J
authors.lastname: LaVail
authors.forename: Carol
authors.initials: C
authors.lastname: Basbaum
mesh_terms: D015703:Antigens, CD; D000951:Antigens, Neoplasm; D051926:Basigin; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned; D006801:Humans; D007150:Immunohistochemistry; D020781:Matrix Metalloproteinase 1 / Q000235:genetics; D008562:Membrane Glycoproteins / Q000502:physiology*; D008854:Microscopy, Electron; D017154:Stromal Cells / Q000166:cytology*; D014158:Transcription, Genetic
chemical_list: D015703:Antigens, CD; D000951:Antigens, Neoplasm; C497886:BSG protein, human; D017077:Culture Media, Conditioned; D008562:Membrane Glycoproteins; D051926:Basigin; D020781:Matrix Metalloproteinase 1