Targeted disruption of the K-ras oncogene in an invasive colon cancer cell line down-regulates urokinase receptor expression and plasminogen-dependent proteolysis.
The urokinase receptor, overexpressed in invasive colon cancer, promotes tumour cell invasion. Since K-Ras is activated in many colon cancers, we determined if urokinase receptor overexpression is a consequence of this activated oncogene. Accordingly, urokinase receptor expression was compared in HCT 116 colon cancer cells containing either a mutation-activated K-Ras or disrupted for this oncogene (by homologous recombination). HCT 116 cells containing the disrupted K-Ras oncogene expressed between 50 and 85% less urokinase receptor protein compared with the parental HCT 116 cells. Reduced urokinase receptor expression in cells containing the disrupted mutated K-Ras was not due to a physical impairment of the urokinase receptor gene since phorbol ester treatment was inductive for its expression. Constitutive urokinase receptor expression in HCT 116 cells required an intact AP-1 motif in the promoter (at -184) and electrophoretic mobility shifting assays indicated less c-Jun, JunD, c-Fos and Fra-1 bound to this motif in the K-Ras-disrupted cells. Since the urokinase receptor accelerates proteolysis, laminin degradation was compared in cells containing the mutation-activated and disrupted K-Ras oncogene. The latter cells displaying fewer urokinase receptors, degraded 80% less laminin. This is the first study to demonstrate a role for K-Ras as a regulator of the constitutive expression of the urokinase receptor.
Allgayer
H
H
Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston 77030, USA.
Wang
H
H
Shirasawa
S
S
Sasazuki
T
T
Boyd
D
D
D002467:Cell Nucleus / Q000378:metabolism; D003110:Colonic Neoplasms / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D011905:Genes, ras; D006801:Humans; D007797:Laminin / Q000378:metabolism; D016296:Mutagenesis; D010958:Plasminogen / Q000378:metabolism*; D014176:Protein Biosynthesis; D011956:Receptors, Cell Surface / Q000032:analysis / Q000235:genetics*; D055293:Receptors, Urokinase Plasminogen Activator; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D007797:Laminin; C524898:PLAUR protein, human; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D010958:Plasminogen