title: Tumor cell cycle arrest induced by shear stress: Roles of integrins and Smad.
abstract: Interstitial flow in and around tumor tissue affects the mechanical microenvironment to modulate tumor cell growth and metastasis. We investigated the roles of flow-induced shear stress in modulating cell cycle distribution in four tumor cell lines and the underlying mechanisms. In all four cell lines, incubation under static conditions for 24 or 48 h led to G(0)/G(1) arrest; in contrast, shear stress (12 dynes/cm(2)) induced G(2)/M arrest. The molecular basis of the shear effect was analyzed, and the presentation on molecular mechanism is focused on human MG63 osteosarcoma cells. Shear stress induced increased expressions of cyclin B1 and p21(CIP1) and decreased expressions of cyclins A, D1, and E, cyclin-dependent protein kinases (Cdk)-1, -2, -4, and -6, and p27(KIP1) as well as a decrease in Cdk1 activity. Using specific antibodies and small interfering RNA, we found that the shear-induced G(2)/M arrest and corresponding changes in G(2)/M regulatory protein expression and activity were mediated by alpha(v)beta(3) and beta(1) integrins through bone morphogenetic protein receptor type IA-specific Smad1 and Smad5. Shear stress also down-regulated runt-related transcription factor 2 (Runx2) binding activity and osteocalcin and alkaline phosphatase expressions in MG63 cells; these responses were mediated by alpha(v)beta(3) and beta(1) integrins through Smad5. Our findings provide insights into the mechanism by which shear stress induces G(2)/M arrest in tumor cells and inhibits cell differentiation and demonstrate the importance of mechanical microenvironment in modulating molecular signaling, gene expression, cell cycle, and functions in tumor cells.
authors.affiliation: Department of Biological Science and Technology, National Chiao Tung University, Hsinchu 300, Taiwan.
authors.forename: Shun-Fu
authors.initials: SF
authors.lastname: Chang
authors.forename: Cheng Allen
authors.initials: CA
authors.lastname: Chang
authors.forename: Ding-Yu
authors.initials: DY
authors.lastname: Lee
authors.forename: Pei-Ling
authors.initials: PL
authors.lastname: Lee
authors.forename: Yu-Ming
authors.initials: YM
authors.lastname: Yeh
authors.forename: Chiuan-Ren
authors.initials: CR
authors.lastname: Yeh
authors.forename: Cheng-Kung
authors.initials: CK
authors.lastname: Cheng
authors.forename: Shu
authors.initials: S
authors.lastname: Chien
authors.forename: Jeng-Jiann
authors.initials: JJ
authors.lastname: Chiu
mesh_terms: D052005:Bone Morphogenetic Protein Receptors, Type I / Q000378:metabolism; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism; D016195:G2 Phase; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000378:metabolism; D019012:Integrin beta1 / Q000378:metabolism; D016023:Integrins / Q000378:metabolism*; D008938:Mitosis; D008954:Models, Biological; D009369:Neoplasms / Q000473:pathology*; D010766:Phosphorylation; D011485:Protein Binding; D051785:Smad Proteins / Q000378:metabolism*; D051898:Smad1 Protein / Q000378:metabolism; D051902:Smad5 Protein / Q000378:metabolism; D013314:Stress, Mechanical
chemical_list: D018797:Cell Cycle Proteins; D050659:Core Binding Factor Alpha 1 Subunit; D039302:Integrin alphaVbeta3; D019012:Integrin beta1; D016023:Integrins; C493709:RUNX2 protein, human; D051785:Smad Proteins; D051898:Smad1 Protein; D051902:Smad5 Protein; D052005:Bone Morphogenetic Protein Receptors, Type I