Recovery of phospho-ERK activity allows melanoma cells to escape from BRAF inhibitor therapy.
BACKGROUND
Resistance to BRAF inhibitors is an emerging problem in the melanoma field. Strategies to prevent and overcome resistance are urgently required.


METHODS
The dynamics of cell signalling, BrdU incorporation and cell-cycle entry after BRAF inhibition was measured using flow cytometry and western blot. The ability of combined BRAF/MEK inhibition to prevent the emergence of resistance was demonstrated by apoptosis and colony formation assays and in 3D organotypic cell culture.


RESULTS
BRAF inhibition led to a rapid recovery of phospho-ERK (pERK) signalling. Although most of the cells remained growth arrested in the presence of drug, a minor population of cells retained their proliferative potential and escaped from BRAF inhibitor therapy. A function for the rebound pERK signalling in therapy escape was demonstrated by the ability of combined BRAF/MEK inhibition to enhance the levels of apoptosis and abrogate the onset of resistance.


CONCLUSIONS
Combined BRAF/MEK inhibition may be one strategy to prevent the emergence of drug resistance in BRAF-V600E-mutated melanomas.
Department of Molecular Oncology, The Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA.
K H T
KH
Paraiso
I V
IV
Fedorenko
L P
LP
Cantini
A C
AC
Munko
M
M
Hall
V K
VK
Sondak
J L
JL
Messina
K T
KT
Flaherty
K S M
KS
Smalley
D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D020935:MAP Kinase Signaling System; D008545:Melanoma / Q000188:drug therapy*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009154:Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors*; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors
D007211:Indoles; C528407:PLX 4720; D013449:Sulfonamides; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases