title: Endothelial expression of TNF receptor-1 generates a proapoptotic signal inhibited by integrin α6β1 in glioblastoma.
abstract: Activation of TNF receptor 1 (TNF-R1) can generate signals that promote either apoptosis or survival. In this study, we show that these signals can be determined by the character of the extracellular matrix in the tumor microenvironment. Specifically, through studies of glioblastoma, we showed that TNFα stimulation induced apoptosis of primary brain endothelial cells (EC) attached to collagen or fibronectin (which engage integrins α2β1/α3β1 and α5β1, respectively), but did not induce apoptosis of ECs attached to laminin (which engages integrins α6β1 and α3β1). TNF-R1 expression was significantly higher in ECs in glioblastoma (GBM) tumors compared with ECs in normal brain specimens. TNFα was also expressed in GBM tumor-associated ECs, which was associated with longer patient survival. ECs plated on anti-integrin α2 or α3 antibody were susceptible to TNFα-induced apoptosis, whereas those plated on anti-integrin α6 antibody were not. Moreover, the ECs plated on laminin, but not collagen, expressed cellular FLICE inhibitory protein (cFLIP) and TNFα stimulation of laminin-attached cells in which cFLIP had been downregulated resulted in the induction of apoptosis. In contrast, attachment to laminin did not induce cFLIP expression in GBM tumor stem cells. Together, our findings indicate that the laminin receptor integrin α6β1 promotes the survival of brain ECs by inhibiting prodeath signaling by TNF-R1, in part by inducing cFLIP expression.
authors.affiliation: Department of Cancer Biology, Cleveland Clinic, Cleveland, Ohio, USA.
authors.forename: Ping
authors.initials: P
authors.lastname: Huang
authors.forename: M R Sandhya
authors.initials: MR
authors.lastname: Rani
authors.forename: Manmeet S
authors.initials: MS
authors.lastname: Ahluwalia
authors.forename: Eunnyung
authors.initials: E
authors.lastname: Bae
authors.forename: Richard A
authors.initials: RA
authors.lastname: Prayson
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Weil
authors.forename: Amy S
authors.initials: AS
authors.lastname: Nowacki
authors.forename: Hirad
authors.initials: H
authors.lastname: Hedayat
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Sloan
authors.forename: Justin D
authors.initials: JD
authors.lastname: Lathia
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Rich
authors.forename: Russell
authors.initials: R
authors.lastname: Tipps
authors.forename: Candece L
authors.initials: CL
authors.lastname: Gladson
mesh_terms: D017209:Apoptosis; D001921:Brain / Q000378:metabolism; D001932:Brain Neoplasms / Q000378:metabolism*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D015536:Down-Regulation; D004730:Endothelium, Vascular / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D005909:Glioblastoma / Q000378:metabolism*; D006801:Humans; D039121:Integrin alpha6beta1 / Q000378:metabolism*; D007797:Laminin / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D005353:Fibronectins; D039121:Integrin alpha6beta1; D007797:Laminin; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha; D003094:Collagen