Overexpression of hyperactive integrin-linked kinase leads to increased cellular radiosensitivity.
Integrin-linked kinase (ILK), bound to the cytoplasmic tails of integrin beta1, beta2, and beta3, is thought to signal through AKT and glycogen synthase kinase-3beta (GSK-3beta) for survival and proliferation regulation. To determine the role of ILK in the cellular radiation response, stably transfected A549 lung cancer cells overexpressing either wild-type (ILK-wk) or hyperactive ILK (ILK-hk) were studied for survival, signaling, proliferation, and examined in immunofluorescence and adhesion assays. Strong radiosensitization was observed in ILK-hk in contrast to ILK-wk mutants and empty vector controls. ILK small interfering RNA transfections showed radioresistance similar to irradiation on fibronectin. AKT, GSK-3beta-cyclin D1, mitogen-activated protein kinase kinase 1/2-mitogen-activated protein kinase, and c-Jun NH2-terminal kinase signaling was dysregulated in irradiated ILK-hk mutants. Immunofluorescence stainings of ILK-hk cells indicated disturbed ILK and paxillin membrane localization with concomitant decrease in focal adhesions. Profound ILK-hk-dependent changes in morphology were characterized by spindle-like cell shape, cell size reduction, increased cell protrusions, strong formation of membranous f-actin rings, and significantly reduced adhesion to matrix proteins. Additionally, ILK-wk and ILK-hk overexpression impaired beta1-integrin clustering and protein Tyr-phosphorylation. Taken together, the data provide evidence that ILK signaling modulates the cellular radiation response involving diverse signaling pathways and through changes in f-actin-based processes such as focal adhesion formation, cell adhesion, and spreading. Identification of ILK and its signaling partners as potential targets for tumor radiosensitization might promote innovative anticancer strategies by providing insight into the mechanism of cell adhesion-mediated radioresistance, oncogenic transformation, and tumor growth and spread.
Bundeswehr Institute of Radiobiology, Munich, Germany. cordes@radiation-biology.de
Nils
N
Cordes
D000199:Actins / Q000378:metabolism; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D022001:Focal Adhesions / Q000502:physiology; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism / Q000502:physiology; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D008175:Lung Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000532:radiotherapy; D020935:MAP Kinase Signaling System / Q000235:genetics / Q000502:physiology; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D011836:Radiation Tolerance / Q000502:physiology*; D016160:Retinoblastoma Protein / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D000099200:Scaffold Protein ILK
D000199:Actins; D019938:Cyclin D1; D003598:Cytoskeletal Proteins; D016326:Extracellular Matrix Proteins; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D019012:Integrin beta1; D051419:Paxillin; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D016160:Retinoblastoma Protein; D014443:Tyrosine; D000099200:Scaffold Protein ILK; C496061:PXN protein, human; C494918:AKT1 protein, human; C000605506:GSK3B protein, human