Differential response of neuroblastoma cells to TRAIL is independent of PI3K/AKT.
BACKGROUND
In many human tumor cells, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis through caspase activation, whereas activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway prevents apoptosis. We hypothesized that inhibition of PI3K/Akt would increase TRAIL-induced apoptosis in neuroblastoma cells.


METHODS
SK-N-AS, SH-SY5Y, and IMR-32 neuroblastoma cells were cultured with either standard media or media with PI3K/Akt inhibitor for 24 hours. These cells were then exposed to 100 ng/mL of TRAIL for 90 minutes and harvested. Cells either underwent flow cytometric analysis of apoptosis, had protein extracted for Western blot, had RNA extracted for reverse transcription-polymerase chain reaction, or had cell lysates analyzed for caspase-3, -8, and -9.


RESULTS
Baseline expression of TRAIL receptors and Akt varied among the cell lines. Inhibition of PI3K/Akt decreased caspase-3 activation in the AS and SY cells, but did not alter TRAIL-induced apoptosis in any of the cell lines. Activity of caspase-8 and -9 was also unaffected by PI3K/Akt attenuation.


CONCLUSIONS
Inhibition of the PI3K/Akt pathway does not increase the sensitivity of neuroblastoma cell lines to TRAIL-induced apoptosis. Neuroblastoma is unique in that activation of the PI3K/Akt pathway is either not essential to its TRAIL resistance or counteracted because of the multiple repetitive pathways of TRAIL resistance.
Efron
Philip A
PA
Division of Pediatric Surgery, Department of Surgery, University of Florida College of Medicine, Box 100286, JHMHSC, Gainesville, FL 32610-0286, USA.
Chen
Mike K
MK
Iyengar
Meera
M
Dai
Wei
W
Nagaram
Abhilasha
A
Beierle
Elizabeth A
EA
D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism / Q000494:pharmacology*; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000494:pharmacology*; D009025:Morpholines / Q000494:pharmacology; D009447:Neuroblastoma / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*
D051017:Apoptosis Regulatory Proteins; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D002867:Chromones; D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha; C505653:TNFSF10 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human