PT  - JOURNAL ARTICLE
AU  - John S. Lazo
AU  - Elizabeth R. Sharlow
AU  - Michael W. Epperly
AU  - Ana Lira
AU  - Stephanie Leimgruber
AU  - Erin M. Skoda
AU  - Peter Wipf
AU  - Joel S. Greenberger
TI  - Pharmacologic Profiling of Phosphoinositide 3-Kinase Inhibitors as Mitigators of Ionizing Radiation–Induced Cell Death
AID  - 10.1124/jpet.113.208421
DP  - 2013 Dec 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 669--680
VI  - 347
IP  - 3
4099  - http://jpet.aspetjournals.org/content/347/3/669.short
4100  - http://jpet.aspetjournals.org/content/347/3/669.full
SO  - J Pharmacol Exp Ther2013 Dec 01; 347
AB  - Ionizing radiation (IR) induces genotoxic stress that triggers adaptive cellular responses, such as activation of the phosphoinositide 3-kinase (PI3K)/Akt signaling cascade. Pluripotent cells are the most important population affected by IR because they are required for cellular replenishment. Despite the clear danger to large population centers, we still lack safe and effective therapies to abrogate the life-threatening effects of any accidental or intentional IR exposure. Therefore, we computationally analyzed the chemical structural similarity of previously published small molecules that, when given after IR, mitigate cell death and found a chemical cluster that was populated with PI3K inhibitors. Subsequently, we evaluated structurally diverse PI3K inhibitors. It is remarkable that 9 of 14 PI3K inhibitors mitigated γIR-induced death in pluripotent NCCIT cells as measured by caspase 3/7 activation. A single intraperitoneal dose of LY294002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one], administered to mice at 4 or 24 hours, or PX-867 [(4S,4aR,5R,6aS,9aR,Z)-11-hydroxy-4-(methoxymethyl)-4a,6a-dimethyl-2,7,10-trioxo-1-(pyrrolidin-1-ylmethylene)-1,2,4,4a,5,6,6a,7,8,9,9a,10-dodecahydroindeno[4,5-H]isochromen-5-yl acetate (CID24798773)], administered 4 hours after a lethal dose of γIR, statistically significantly (P < 0.02) enhanced in vivo survival. Because cell cycle checkpoints are important regulators of cell survival after IR, we examined cell cycle distribution in NCCIT cells after γIR and PI3K inhibitor treatment. LY294002 and PX-867 treatment of nonirradiated cells produced a marked decrease in S phase cells with a concomitant increase in the G1 population. In irradiated cells, LY294002 and PX-867 treatment also decreased S phase and increased the G1 and G2 populations. Treatment with LY294002 or PX-867 decreased γIR-induced DNA damage as measured by γH2AX, suggesting reduced DNA damage. These results indicate pharmacologic inhibition of PI3K after IR abrogated cell death.