title: Inhibition of ILK in PTEN-mutant human glioblastomas inhibits PKB/Akt activation, induces apoptosis, and delays tumor growth.
abstract: The tumor suppressor gene phosphatase and tensin homologue (PTEN) regulates the phosphatidylinositol-3'-kinase (PI3K) signaling pathway and has been shown to correlate with poor prognosis in high-grade astrocytomas when mutational inactivation or loss of the PTEN gene occurs. PTEN mutation leads to constitutive activation of protein kinase B (PKB)/Akt with phosphorylation at the PKB/Akt sites Thr-308 and Ser-473. Integrin-linked kinase (ILK) has been shown to regulate PKB/Akt activity with the loss of PTEN in prostate cancer. We now demonstrate that ILK activity regulates PKB/Akt activity in glioblastoma cells. The activity of ILK is constitutively elevated in a serum-independent manner in PTEN mutant cells, and transfection of wild-type PTEN under the control of an inducible promoter into mutant PTEN cells inhibits ILK activity. Transfection of ILK antisense (ILKAS) or exposure to a small-molecule ILK inhibitor suppresses the constitutive phosphorylation of PKB/Akt on Ser-473 in PTEN-mutant glioblastoma cell lines. In addition, the delivery of ILKAS to PTEN-negative glioblastoma cells resulted in apoptosis. Rag-2M mice bearing established ( approximately 100 mg) human U87MG glioblastoma tumors, treated QD x 5 for 3 consecutive weeks with ILKAS (i.p. 5 mg/kg), exhibited stable disease with < or =7% increase in tumor volume over the 3-week course of treatment. In contrast, animals treated with an oligonucleotide control or saline exhibited a >100% increase in tumor volume over the same time period. Our initial results indicate that therapeutic strategies targeting ILK may be beneficial in the treatment of glioblastomas.
authors.affiliation: Department of Advanced Therapeutics, BC Cancer Agency, Vancouver, BC, Canada. ledwards@bccrc.ca
authors.forename: Lincoln A
authors.initials: LA
authors.lastname: Edwards
authors.forename: B
authors.initials: B
authors.lastname: Thiessen
authors.forename: Wieslawa H
authors.initials: WH
authors.lastname: Dragowska
authors.forename: Tim
authors.initials: T
authors.lastname: Daynard
authors.forename: Marcel B
authors.initials: MB
authors.lastname: Bally
authors.forename: Shoukat
authors.initials: S
authors.lastname: Dedhar
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000201:enzymology* / Q000473:pathology; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000502:physiology; D005434:Flow Cytometry; D005909:Glioblastoma / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D009154:Mutation; D051059:PTEN Phosphohydrolase; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D025521:Tumor Suppressor Proteins / Q000235:genetics; D000099200:Scaffold Protein ILK
chemical_list: D064413:3-Phosphoinositide-Dependent Protein Kinases; D051059:PTEN Phosphohydrolase; D010744:Phosphoric Monoester Hydrolases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D025521:Tumor Suppressor Proteins; D000099200:Scaffold Protein ILK; C494918:AKT1 protein, human; C494929:PTEN protein, human