p27Kip1 and cyclin D1 are necessary for focal adhesion kinase regulation of cell cycle progression in glioblastoma cells propagated in vitro and in vivo in the scid mouse brain.
We have reported previously that the expression of focal adhesion kinase (FAK) is elevated in glioblastomas and that expression of FAK promotes the proliferation of glioblastoma cells propagated in either soft agar or in the C.B.17 severe combined immunodeficiency (scid) mouse brain. We therefore determined the effect of FAK on cell cycle progression in these cells. We found that overexpression of wild-type FAK promoted exit from G(1) in monolayer cultures of glioblastoma cells, enhanced the expression of cyclins D1 and E while reducing the expression of p27(Kip1) and p21(Waf1), and enhanced the kinase activity of the cyclin D1-cyclin-dependent kinase-4 (cdk4) complex. Transfection of the monolayers with a FAK molecule in which the autophosphorylation site is mutated (FAK397F) inhibited exit from G(1) and reduced the expression of cyclins D1 and E while enhancing the expression of p27(Kip1) and p21(Waf1). Small interfering RNA (siRNA)-mediated down-regulation of cyclin D1 inhibited the enhancement of cell cycle progression observed on expression of wild-type FAK, whereas siRNA-mediated down-regulation of cyclin E had no effect. siRNA-mediated down-regulation of p27(Kip1) overcame the inhibition of cell cycle progression observed on expression of FAK397F, whereas down-regulation of p21(Waf1) had no effect. These results were confirmed in vivo in the scid mouse brain xenograft model in which propagation of glioblastoma cells expressing FAK397F resulted in a 50% inhibition of tumor growth and inhibited exit from G(1). Taken together, our results indicate that FAK promotes proliferation of glioblastoma cells by enhancing exit from G(1) through a mechanism that involves cyclin D1 and p27(Kip1).
Ding
Qiang
Q
Department of Pathology, the University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
Grammer
J Robert
JR
Nelson
Mark A
MA
Guan
Jun-Lin
JL
Stewart
Jerry E
JE
Gladson
Candece L
CL
D000818:Animals; D001921:Brain / Q000473:pathology*; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology*; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000235:genetics / Q000502:physiology*; D019927:Cyclin E / Q000235:genetics; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D016193:G1 Phase; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D005909:Glioblastoma / Q000235:genetics / Q000473:pathology*; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D009154:Mutation; D009374:Neoplasms, Experimental / Q000235:genetics; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000502:physiology*; D014183:Transplantation, Heterologous; D025521:Tumor Suppressor Proteins / Q000502:physiology*
C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C496051:Ptk2 protein, mouse