title: Matrix rigidity regulates the transition of tumor cells to a bone-destructive phenotype through integrin β3 and TGF-β receptor type II.
abstract: Cancer patients frequently develop skeletal metastases that significantly impact quality of life. Since bone metastases remain incurable, a clearer understanding of molecular mechanisms regulating skeletal metastases is required to develop new therapeutics that block establishment of tumors in bone. While many studies have suggested that the microenvironment contributes to bone metastases, the factors mediating tumors to progress from a quiescent to a bone-destructive state remain unclear. In this study, we hypothesized that the "soil" of the bone microenvironment, specifically the rigid mineralized extracellular matrix, stimulates the transition of the tumor cells to a bone-destructive phenotype. To test this hypothesis, we synthesized 2D polyurethane (PUR) films with elastic moduli ranging from the basement membrane (70 MPa) to cortical bone (3800 MPa) and measured expression of genes associated with mechanotransduction and bone metastases. We found that expression of Integrin β3 (Iβ3), as well as tumor-produced factors associated with bone destruction (Gli2 and parathyroid hormone related protein (PTHrP)), significantly increased with matrix rigidity, and that blocking Iβ3 reduced Gli2 and PTHrP expression. To identify the mechanism by which Iβ3 regulates Gli2 and PTHrP (both are also known to be regulated by TGF-β), we performed Förster resonance energy transfer (FRET) and immunoprecipitation, which indicated that Iβ3 co-localized with TGF-β Receptor Type II (TGF-β RII) on rigid but not compliant films. Finally, transplantation of tumor cells expressing Iβ3 shRNA into the tibiae of athymic nude mice significantly reduced PTHrP and Gli2 expression, as well as bone destruction, suggesting a crucial role for tumor-produced Iβ3 in disease progression. This study demonstrates that the rigid mineralized bone matrix can alter gene expression and bone destruction in an Iβ3/TGF-β-dependent manner, and suggests that Iβ3 inhibitors are a potential therapeutic approach for blocking tumor transition to a bone destructive phenotype.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, 37235, USA.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Page
authors.affiliation: Department of Veterans Affairs: Tennessee Valley Healthcare System, Nashville, TN, 37212, USA.|Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.|Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.
authors.forename: Alyssa R
authors.initials: AR
authors.lastname: Merkel
authors.affiliation: Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, 37235, USA.
authors.forename: Nazanin S
authors.initials: NS
authors.lastname: Ruppender
authors.affiliation: Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, 37235, USA.
authors.forename: Ruijing
authors.initials: R
authors.lastname: Guo
authors.affiliation: Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, 37235, USA.|Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.
authors.forename: Ushashi C
authors.initials: UC
authors.lastname: Dadwal
authors.affiliation: Department of Veterans Affairs: Tennessee Valley Healthcare System, Nashville, TN, 37212, USA.|Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.|Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.
authors.forename: Shellese
authors.initials: S
authors.lastname: Cannonier
authors.affiliation: Agilent Technologies, Chandler, AZ, 85226.
authors.forename: Sandip
authors.initials: S
authors.lastname: Basu
authors.affiliation: Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, 37235, USA.|Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.|Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, 37235, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Guelcher
authors.affiliation: Department of Veterans Affairs: Tennessee Valley Healthcare System, Nashville, TN, 37212, USA.|Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.|Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.|Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Sterling
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology / Q000556:secondary; D000818:Animals; D001859:Bone Neoplasms / Q000150:complications / Q000556:secondary; D001943:Breast Neoplasms / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000556:secondary; D045744:Cell Line, Tumor; D055119:Elastic Modulus; D005109:Extracellular Matrix / Q000502:physiology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D039661:Integrin beta3 / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D051741:Kruppel-Like Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D008175:Lung Neoplasms / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics; D010014:Osteolysis / Q000209:etiology*; D018583:Pliability; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000502:physiology*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000502:physiology*; D059016:Tumor Microenvironment / Q000502:physiology*; D023041:Xenograft Model Antitumor Assays; D000075746:Zinc Finger Protein Gli2
chemical_list: C082593:GLI2 protein, human; D039661:Integrin beta3; D051741:Kruppel-Like Transcription Factors; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D000075746:Zinc Finger Protein Gli2; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II
keywords: Bone metastasis; Integrins; Matrix rigidity; Mechanotransduction; Parathyroid hormone-related protein; Polyurethane; TGF-β