title: Matrix rigidity regulates cancer cell growth by modulating cellular metabolism and protein synthesis.
abstract: BACKGROUND
  Tumor cells in vivo encounter diverse types of microenvironments both at the site of the primary tumor and at sites of distant metastases. Understanding how the various mechanical properties of these microenvironments affect the biology of tumor cells during disease progression is critical in identifying molecular targets for cancer therapy.
  
  
  RESULTS
  This study uses flexible polyacrylamide gels as substrates for cell growth in conjunction with a novel proteomic approach to identify the properties of rigidity-dependent cancer cell lines that contribute to their differential growth on soft and rigid substrates. Compared to cells growing on more rigid/stiff substrates (>10,000 Pa), cells on soft substrates (150-300 Pa) exhibited a longer cell cycle, due predominantly to an extension of the G1 phase of the cell cycle, and were metabolically less active, showing decreased levels of intracellular ATP and a marked reduction in protein synthesis. Using stable isotope labeling of amino acids in culture (SILAC) and mass spectrometry, we measured the rates of protein synthesis of over 1200 cellular proteins under growth conditions on soft and rigid/stiff substrates. We identified cellular proteins whose syntheses were either preferentially inhibited or preserved on soft matrices. The former category included proteins that regulate cytoskeletal structures (e.g., tubulins) and glycolysis (e.g., phosphofructokinase-1), whereas the latter category included proteins that regulate key metabolic pathways required for survival, e.g., nicotinamide phosphoribosyltransferase, a regulator of the NAD salvage pathway.
  
  
  CONCLUSIONS
  The cellular properties of rigidity-dependent cancer cells growing on soft matrices are reminiscent of the properties of dormant cancer cells, e.g., slow growth rate and reduced metabolism. We suggest that the use of relatively soft gels as cell culture substrates would allow molecular pathways to be studied under conditions that reflect the different mechanical environments encountered by cancer cells upon metastasis to distant sites.
authors.affiliation: Department of Microbiology, Immunology and Cancer Biology, University of Virginia, Charlottesville, Virginia, United States of America. rt9c@virginia.edu
authors.forename: Robert W
authors.initials: RW
authors.lastname: Tilghman
authors.forename: Edik M
authors.initials: EM
authors.lastname: Blais
authors.forename: Catharine R
authors.initials: CR
authors.lastname: Cowan
authors.forename: Nicholas E
authors.initials: NE
authors.lastname: Sherman
authors.forename: Pablo R
authors.initials: PR
authors.lastname: Grigera
authors.forename: Erin D
authors.initials: ED
authors.lastname: Jeffery
authors.forename: Jay W
authors.initials: JW
authors.lastname: Fox
authors.forename: Brett R
authors.initials: BR
authors.lastname: Blackman
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Tschumperlin
authors.forename: Jason A
authors.initials: JA
authors.lastname: Papin
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Parsons
mesh_terms: D000180:Acrylic Resins; D000255:Adenosine Triphosphate / Q000378:metabolism; D001696:Biomechanical Phenomena; D001973:Bromodeoxyuridine; D045744:Cell Line, Tumor; D060833:Cellular Microenvironment / Q000502:physiology*; D019938:Cyclin D1 / Q000378:metabolism; D005109:Extracellular Matrix / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007553:Isotope Labeling; D013058:Mass Spectrometry; D009369:Neoplasms / Q000378:metabolism* / Q000503:physiopathology; D014176:Protein Biosynthesis / Q000502:physiology*; D040901:Proteomics / Q000379:methods
chemical_list: D000180:Acrylic Resins; C016680:polyacrylamide gels; D019938:Cyclin D1; D000255:Adenosine Triphosphate; D001973:Bromodeoxyuridine