Basal and treatment-induced activation of AKT mediates resistance to cell death by AZD6244 (ARRY-142886) in Braf-mutant human cutaneous melanoma cells.
The majority of melanomas show constitutive activation of the RAS-RAF-MAP/ERK kinase (MEK)-mitogen-activated protein kinase (MAPK) pathway. AZD6244 is a selective MEK1/2 inhibitor that markedly reduces tumor P-MAPK levels, but it produces few clinical responses in melanoma patients. An improved understanding of the determinants of resistance to AZD6244 may lead to improved patient selection and effective combinatorial approaches. The effects of AZD6244 on cell growth and survival were tested in a total of 14 Braf-mutant and 3 wild-type human cutaneous melanoma cell lines. Quantitative assessment of phospho-protein levels in the Braf-mutant cell lines by reverse phase protein array (RPPA) analysis showed no significant association between P-MEK or P-MAPK levels and AZD6244 sensitivity, but activation-specific markers in the phosphoinositide 3-kinase (PI3K)-AKT pathway correlated with resistance. We also identified resistant cell lines without basal activation of the PI3K-AKT pathway. RPPA characterization of the time-dependent changes in signaling pathways revealed that AZD6244 produced durable and potent inhibition of P-MAPK in sensitive and resistant Braf-mutant cell lines, but several resistant lines showed AZD6244-induced activation of AKT. In contrast, sensitive cell lines showed AZD6244 treatment-induced upregulation of PTEN protein and mRNA expression. Inhibition of AKT, TORC1/2, or insulin-like growth factor I receptor blocked AZD6244-induced activation of AKT and resulted in synergistic cell killing with AZD6244. These findings identify basal and treatment-induced regulation of the PI3K-AKT pathway as a critical regulator of AZD6244 sensitivity in Braf-mutant cutaneous melanoma cells and the novel regulation of PTEN expression by AZD6244 in sensitive cells, and suggest new combinatorial approaches for patients.
Departments of Melanoma Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
Y N Vashisht
YN
Gopal
Wanleng
W
Deng
Scott E
SE
Woodman
Kakajan
K
Komurov
Prahlad
P
Ram
Paul D
PD
Smith
Michael A
MA
Davies
D017209:Apoptosis / Q000187:drug effects*; D001562:Benzimidazoles / Q000494:pharmacology*; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008545:Melanoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D009154:Mutation / Q000235:genetics; D051059:PTEN Phosphohydrolase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D058539:Phosphatidylinositol 3-Kinase / Q000235:genetics / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects*; D012878:Skin Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D014407:Tumor Cells, Cultured
C517975:AZD 6244; D001562:Benzimidazoles; D000081082:Phosphoinositide-3 Kinase Inhibitors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D058539:Phosphatidylinositol 3-Kinase; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human