title: The outgrowth of micrometastases is enabled by the formation of filopodium-like protrusions.
abstract: Disseminated cancer cells that have extravasated into the tissue parenchyma must interact productively with its extracellular matrix components to survive, proliferate, and form macroscopic metastases. The biochemical and cell biologic mechanisms enabling this interaction remain poorly understood. We find that the formation of elongated integrin β(1)-containing adhesion plaques by cancer cells that have extravasated into the lung parenchyma enables the proliferation of these cells via activation of focal adhesion kinase. These plaques originate in and appear only after the formation of filopodium-like protrusions (FLP) that harbor integrin β(1) along their shafts. The cytoskeleton-regulating proteins Rif and mDia2 contribute critically to the formation of these protrusions and thereby enable the proliferation of extravasated cancer cells. Hence, the formation of FLPs represents a critical rate-limiting step for the subsequent development of macroscopic metastases.
  
  
  CONCLUSIONS
  Although the mechanisms of metastatic dissemination have begun to be uncovered, those involved in the establishment of extravasated cancer cells in foreign tissue microenvironments remained largely obscure. We have studied the behavior of recently extravasated cancer cells in the lungs and identified a series of cell biologic processes involving the formation of filopodium-like protrusions and the subsequent development of elongated, mature adhesion plaques, which contribute critically to the rapid proliferation of the micrometastatic cells and thus are prerequisites to the eventual lung colonization by these cells.
authors.affiliation: Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Shibue
authors.forename: Mary W
authors.initials: MW
authors.lastname: Brooks
authors.forename: M Fatih
authors.initials: MF
authors.lastname: Inan
authors.forename: Ferenc
authors.initials: F
authors.lastname: Reinhardt
authors.forename: Robert A
authors.initials: RA
authors.lastname: Weinberg
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D048708:Cell Growth Processes / Q000502:physiology; D045744:Cell Line, Tumor; D005109:Extracellular Matrix / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D022001:Focal Adhesions / Q000201:enzymology / Q000473:pathology / Q000648:ultrastructure; D006801:Humans; D061986:MCF-7 Cells; D051379:Mice; D061206:Neoplasm Micrometastasis / Q000473:pathology / Q000648:ultrastructure*; D009369:Neoplasms / Q000201:enzymology / Q000473:pathology / Q000648:ultrastructure*; D011554:Pseudopodia / Q000201:enzymology / Q000473:pathology / Q000648:ultrastructure
chemical_list: D051416:Focal Adhesion Protein-Tyrosine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases