title: Cucurbitacin-I inhibits Aurora kinase A, Aurora kinase B and survivin, induces defects in cell cycle progression and promotes ABT-737-induced cell death in a caspase-independent manner in malignant human glioma cells.
abstract: Because STAT signaling is commonly activated in malignant gliomas as a result of constitutive EGFR activation, strategies for inhibiting the EGFR/JAK/STAT cascade are of significant interest. We, therefore, treated a panel of established glioma cell lines, including EGFR overexpressors, and primary cultures derived from patients diagnosed with glioblastoma with the JAK/STAT inhibitor cucurbitacin-I. Treatment with cucurbitacin-I depleted p-STAT3, p-STAT5, p-JAK1 and p-JAK2 levels, inhibited cell proliferation, and induced G2/M accumulation, DNA endoreduplication, and multipolar mitotic spindles. Longer exposure to cucurbitacin-I significantly reduced the number of viable cells and this decrease in viability was associated with cell death, as confirmed by an increase in the subG1 fraction. Our data also demonstrated that cucurbitacin-I strikingly downregulated Aurora kinase A, Aurora kinase B and survivin. We then searched for agents that exhibited a synergistic effect on cell death in combination with cucurbitacin-I. We found that cotreatment with cucurbitacin-I significantly increased Bcl(-)2/Bcl(-)xL family member antagonist ABT-737-induced cell death regardless of EGFR/PTEN/p53 status of malignant human glioma cell lines. Although >50% of the cucurbitacin-I plus ABT-737 treated cells were annexin V and propidium iodide positive, PARP cleavage or caspase activation was not observed. Pretreatment of z-VAD-fmk, a pan caspase inhibitor did not inhibit cell death, suggesting a caspase-independent mechanism of cell death. Genetic inhibition of Aurora kinase A or Aurora kinase B or survivin by RNA interference also sensitized glioma cells to ABT-737, suggesting a link between STAT activation and Aurora kinases in malignant gliomas.
authors.affiliation: a Department of Neurosurgery ; University of Pittsburgh School of Medicine ; Pittsburgh , PA USA.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Premkumar
authors.forename: Esther P
authors.initials: EP
authors.lastname: Jane
authors.forename: Ian F
authors.initials: IF
authors.lastname: Pollack
mesh_terms: D001253:Astrocytes / Q000378:metabolism; D064096:Aurora Kinase A / Q000037:antagonists & inhibitors*; D064107:Aurora Kinase B / Q000037:antagonists & inhibitors*; D001713:Biphenyl Compounds / Q000494:pharmacology*; D020169:Caspases / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects*; D059447:Cell Cycle Checkpoints / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D005838:Genotype; D005910:Glioma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000037:antagonists & inhibitors*; D009596:Nitrophenols / Q000494:pharmacology*; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology*; D000077022:Survivin; D014315:Triterpenes / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: C501332:ABT-737; C107489:BIRC5 protein, human; D001713:Biphenyl Compounds; D051034:Inhibitor of Apoptosis Proteins; D009596:Nitrophenols; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D013449:Sulfonamides; D000077022:Survivin; D014315:Triterpenes; D016159:Tumor Suppressor Protein p53; D066246:ErbB Receptors; D064096:Aurora Kinase A; D064107:Aurora Kinase B; D051059:PTEN Phosphohydrolase; D020169:Caspases; C038106:cucurbitacin I
keywords: Aurora kinases; BSA, bovine serum albumin; DMSO, dimethyl sulfoxide; EGFR, epidermal growth factor receptor; FITC, fluorescein isothiocyanate; Glioma; MTS, 3-[4, 5-dimethylthiazol- 2yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H, tetrazolium; NF-кB, nuclear factor кB; PAGE, polyacrylamide gel electrophoresis; PBS, phosphate-buffered saline; PDGFR, platelet derived growth factor receptor; PI, propidium iodide; PI3K, Phosphatidylinositol 3-Kinase; TBS, Tris-buffered saline; TRAIL, tumor necrosis factor–related apoptosis inducing ligand; caspase-independent cell death; cell cycle arrest