We found that pharmaco logic and genetic inhibition of PI3K activity, Ganetespib cancer as well as direct pharmacological Inhibitors,Modulators,Libraries inhibition of EGFR and Akt led to increased radiosensitivity of human GBM cells. Methods Cell culture and reagents U87MG, MO59J, LN18, H4, A172, DBTRG 05MG, LN229, and HS683 cells were obtained from the Ameri can Type Culture Collection, and were cultured in Dul beccos modified Eagles medium supplemented with 10% FBS and 1% penicillinstrepto mycin. U87MG cells containing transgenes for inducible wild type PTEN, or the phosphatase inactive mutant form of PTEN, PTEN C124S, were gifts from Dr. Georgescu, and were grown in Dulbeccos modified Eagles medium containing 0. 5 mgmL G418, 10gmL blastici din, 10% FBS, and 1% penicillinstreptomy cin. All cells were incubated at 37 C in 5% CO2.

LY294002 and doxycycline Inhibitors,Modulators,Libraries were purchased from Sigma, AG1478 from Biosource, SH 5 from Calbiochem, and MK 2206 from Selleck Chemicals. Irradiation Sub confluent cell monolayers were irradiated using a J. L. Shepard Mark I 137Cs irradiator at 2 Gymin. Western blot analysis Cells were Inhibitors,Modulators,Libraries lysed in lysis buffer containing 20 mM Tris HCl, 150 mM NaCl, 1 mM EDTA, 1 mM EGTA, 1% Triton X 100, 2. 5 mM sodium pyrophos phate, 1 mM glycerophosphate, 1 mM Na3VO4, 1gml leupeptin supplemented with proteinase inhibitor cock tails and phosphatase inhibitor cocktails. Cell lysates were separated by SDS PAGE and transferred to PVDF membranes. After probing with pri mary antibodies, the membranes were incubated with horseradish peroxidase conjugated secondary antibody, and visualized by ECL.

Antibodies specific for total Akt and phospho Akt were obtained from Cell Signaling Technologies. Antibodies Inhibitors,Modulators,Libraries specific for PTEN was from Cascade Bioscience, and that for tubulin was from Neomarkers. Clonogenic Survival Assay Cells in exponential growth phase were irradiated as described above. Prior to irradiation, cells were treated with LY294002, Inhibitors,Modulators,Libraries AG1478, SH 5, or doxycycline as described in the Figure legends. At 4 24 hr post radia tion, the cells were detached from the culture dish with trypsin, and were seeded at various dilutions into 25 cm2 tissue culture flasks in normal medium. 17-AAG mechanism Colonies were allowed to grow for 14 days before staining with a 0. 2% crystal violetformalin solution, and counted under stere omicroscopy. Colonies were defined as clusters of 50 cells. Colony forming efficiency is reported as the survival fraction, which is defined as the total number of clones in irradiated cells divided by total number of clones in oth erwise identical unirradiated cells. Each point on the sur vival curve represents the mean surviving fraction from at least three replicates. Cell survival measurements were fit ted to a linear quadratic mathematical model using the GraphPad Prism 4 program.