Inhibition of human umbilical vein endothelial cell proliferation by the CXC chemokine, platelet factor 4 (PF4), is associated with impaired downregulation of p21(Cip1/WAF1).
Human PF4 is a heparin-binding chemokine known to be capable of inhibiting endothelial cell proliferation and angiogenesis. To explore the biological mechanisms responsible for this action, we investigated the effect of PF4 on epidermal growth factor (EGF)-stimulated human umbilical vein endothelial cells (HUVEC), a model system in which stimulation is essentially independent of interaction with cell-surface glycosaminoglycans. Based on previous findings that PF4 blocks endothelial cell cycle entry and progression into S phase, we studied the molecular mechanism(s) of PF4 interference with cell cycle machinery. PF4 treatment of EGF-stimulated HUVEC caused a decrease in cyclin E-cyclin-dependent kinase 2 (cdk2) activity with resulting attenuation of retinoblastoma protein phosphorylation. PF4-dependent downregulation of cyclin E-cdk2 activity was associated with increased binding of the cyclin-dependent kinase inhibitor, p21(Cip1/WAF1), to the cyclin E-cdk2 complex. Analysis of total cellular p21(Cip1/WAF1) showed that in the presence of PF4, p21(Cip1/WAF1) levels were sustained at time points when p21(Cip1/WAF1) was no longer detectable in cells stimulated by EGF in the absence of PF4. These findings indicate that PF4 inhibition of HUVEC proliferation in response to EGF is associated with impaired downregulation of p21(Cip1/WAF1) and provide the first evidence for interference with cell cycle mechanisms by a chemokine.
Gentilini
G
G
Blood Research Institute, The Blood Center of Southeastern Wisconsin and the Departments of Medicine and Pathology, Medical College of Wisconsin, Milwaukee 53226-3548, USA.
Kirschbaum
N E
NE
Augustine
J A
JA
Aster
R H
RH
Visentin
G P
GP
D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000187:drug effects; D002478:Cells, Cultured; D019743:Chemokines, CXC / Q000502:physiology*; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D004730:Endothelium, Vascular / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006025:Glycosaminoglycans / Q000378:metabolism; D006131:Growth Inhibitors / Q000502:physiology*; D006801:Humans; D010766:Phosphorylation / Q000187:drug effects; D010978:Platelet Factor 4 / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D014471:Umbilical Veins
C493956:CDKN1A protein, human; D019743:Chemokines, CXC; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D006025:Glycosaminoglycans; D006131:Growth Inhibitors; D016160:Retinoblastoma Protein; D016222:Fibroblast Growth Factor 2; D010978:Platelet Factor 4; D004815:Epidermal Growth Factor; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases