title: Pigment epithelium-derived factor blocks tumor extravasation by suppressing amoeboid morphology and mesenchymal proteolysis.
abstract: Metastatic melanoma cells are highly adaptable to their in vivo microenvironment and can switch between protease-dependent mesenchymal and protease-independent amoeboid invasion to facilitate metastasis. Such adaptability can be visualized in vitro, when cells are cultured in conditions that recapitulate three-dimensional microenvironments. Using thick collagen layers in cell culture and in vivo extravasation assays, we found that pigment epithelium-derived factor (PEDF) suppressed lung extravasation of aggressive melanoma by coordinated regulation of cell shape and proteolysis. In cells grown on a thick collagen bed, PEDF overexpression and exogenous PEDF blocked the rapidly invasive, rounded morphology, and promoted an elongated, mesenchymal-like phenotype associated with reduced invasion. These changes in cell shape depended on decreased RhoA and increased Rac1 activation and were mediated by the up-regulation of Rac1-GEF, DOCK3 and down-regulation of Rac1-GAP, ARHGAP22. Surprisingly, we found that PEDF overexpression also blocked the trafficking of membrane-tethered, MT1-MMP to the cell surface through RhoA inhibition and Rac1 activation. In vivo, knockdown of Rac1 and DOCK3 or overexpression of MT1-MMP was sufficient to reverse the inhibitory effect of PEDF on extravasation. Using functional studies, we demonstrated that PEDF suppressed the rounded morphology and MT1-MMP surface localization through its antiangiongenic, 34-mer epitope and the recently identified PEDF receptor candidate, PNPLA2. Our findings unveil the coordinated regulation of cell shape and proteolysis and identify an unknown mechanism for PEDF's antimetastatic activity.
authors.affiliation: Department of Urology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA. o-ladhani@northwestern.edu
authors.forename: Omar
authors.initials: O
authors.lastname: Ladhani
authors.forename: Cristina
authors.initials: C
authors.lastname: Sánchez-Martinez
authors.forename: Jose L
authors.initials: JL
authors.lastname: Orgaz
authors.forename: Benilde
authors.initials: B
authors.lastname: Jimenez
authors.forename: Olga V
authors.initials: OV
authors.lastname: Volpert
mesh_terms: D000656:Amoeba / Q000166:cytology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D048430:Cell Shape / Q000187:drug effects; D002478:Cells, Cultured; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects; D005136:Eye Proteins / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D008648:Mesoderm / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009361:Neoplasm Invasiveness / Q000517:prevention & control*; D009369:Neoplasms / Q000188:drug therapy / Q000473:pathology*; D009414:Nerve Growth Factors / Q000494:pharmacology* / Q000627:therapeutic use; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D011554:Pseudopodia / Q000187:drug effects* / Q000473:pathology; D015843:Serpins / Q000494:pharmacology* / Q000627:therapeutic use; D023041:Xenograft Model Antitumor Assays; D000099174:Pigment Epithelium-Derived Factor
chemical_list: D000970:Antineoplastic Agents; D005136:Eye Proteins; D009414:Nerve Growth Factors; D015843:Serpins; D000099174:Pigment Epithelium-Derived Factor