Combination of PTEN and gamma-ionizing radiation enhances cell death and G(2)/M arrest through regulation of AKT activity and p21 induction in non-small-cell lung cancer cells.
OBJECTIVE
To identify the role of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) during gamma-ionizing radiation (gamma-IR) treatment for non-small-cell lung cancer cells.


METHODS
Wild-type PTEN or mutant forms of PTEN plasmids were transfected to construct stable transfectants of the NCI-H1299 non-small-cell lung cancer cell line. Combined effects of PTEN expression and IR treatment were tested using immunoblot, clonogenic, and cell-counting assays. Related signaling pathways were studied with immunoblot and kinase assays.


RESULTS
At steady state, stable transfectants showed almost the same proliferation rate but had different AKT phosphorylation patterns. When treated with gamma-IR, wild-type PTEN transfectants showed higher levels of cell death compared with mock vector or mutant transfectants, and showed increased G(2)/M cell-cycle arrest accompanied by p21 induction and CDK1 inactivation. NCI-H1299 cells were treated with phosphosinositide-3 kinase (PI3K)/AKT pathway inhibitor (LY29002), resulting in reduced AKT phosphorylation levels. Treatment of NCI-H1299 cells with LY29002 and gamma-IR resulted in increased cell-cycle arrest and p21 induction. Endogenous wild-type PTEN-containing NCI-H460 cells were treated with PTEN-specific siRNA and then irradiated with gamma-IR: however reduced PTEN levels did not induce cell-cycle arrest or p21 expression.


CONCLUSIONS
Taken together, these findings indicate that PTEN may modulate cell death or the cell cycle via AKT inactivation by PTEN and gamma-IR treatment. We also propose that a PTEN-PI3K/AKT-p21-CDK1 pathway could regulate cell death and the cell cycle by gamma-IR treatment.
Park
Jong Kuk
JK
Laboratory of Radiation Tumor Physiology, Korea Institute of Radiological and Medical Sciences, Seoul, Republic of Korea.
Jung
Hae-Yun
HY
Park
Seon Ho
SH
Kang
Seung Yi
SY
Yi
Mi-Rang
MR
Um
Hong Duck
HD
Hong
Sung Hee
SH
D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism / Q000532:radiotherapy*; D002453:Cell Cycle / Q000528:radiation effects; D018797:Cell Cycle Proteins / Q000378:metabolism; D016923:Cell Death; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D002867:Chromones / Q000494:pharmacology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016195:G2 Phase / Q000502:physiology; D005720:Gamma Rays / Q000627:therapeutic use; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism / Q000532:radiotherapy*; D009025:Morpholines / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D014162:Transfection
D016203:CDC2 Protein Kinase; D018797:Cell Cycle Proteins; D002867:Chromones; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004791:Enzyme Inhibitors; D009025:Morpholines; D009363:Neoplasm Proteins; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; C493956:CDKN1A protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494929:PTEN protein, human