Importance of the stress kinase p38alpha in mediating the direct cytotoxic effects of the thalidomide analogue, CPS49, in cancer cells and endothelial cells.
OBJECTIVE
Thalidomide has gained renewed interest as a cancer therapeutic due to its potential antiangiogenic effects. The thalidomide analogues CPS11 and CPS49 are active in preclinical angiogenesis assays and xenograft model systems, but the biochemical basis for these observations is unclear.


METHODS
To address this question, we assessed the toxicity of these thalidomide analogues in cancer cells, endothelial cells, and genetically modified cells using assays that measure apoptotic and nonapoptotic cell death. Phosphospecific and native antibodies were used in immunoblotting and immunohistochemical experiments to assess the activation states of kinases that control cellular survival in vitro and in vivo.


RESULTS
CPS49 predominantly induced nonapoptotic cell death in lung cancer cells, prostate cancer cells, and endothelial cells in a dose-dependent manner, whereas CPS11 was not cytotoxic. CPS49 did not inhibit kinases that promote survival, such as Akt or extracellular signal-regulated kinase, but rather rapidly activated the stress kinase p38 pathway in both cancer cells and endothelial cells. CPS49 activated p38 in tumor xenografts. Using p38alpha-/- cells or an inhibitor of p38, we show that the presence and activation of p38alpha is important for cytotoxicity in all cell types examined.


CONCLUSIONS
Our studies identify a unifying mechanism of action for cytotoxicity of the tetraflourinated thalidomide analogue, CPS49, and suggest that activation of p38 could serve as a biomarker in clinical trials with CPS49.
Warfel
Noel A
NA
Medical Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20889, USA.
Lepper
Erin R
ER
Zhang
Chunyu
C
Figg
William D
WD
Dennis
Phillip A
PA
D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004354:Drug Screening Assays, Antitumor; D042783:Endothelial Cells / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D051379:Mice; D016513:Mice, SCID; D048308:Mitogen-Activated Protein Kinase 14 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology; D009570:Nitriles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013792:Thalidomide / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D023041:Xenograft Model Antitumor Assays
D002070:Butadienes; C494622:CPS 49; D004791:Enzyme Inhibitors; D007093:Imidazoles; D009570:Nitriles; D011725:Pyridines; C113580:U 0126; D013792:Thalidomide; D048049:Extracellular Signal-Regulated MAP Kinases; D048308:Mitogen-Activated Protein Kinase 14; C093642:SB 203580