COT drives resistance to RAF inhibition through MAP kinase pathway reactivation.
Oncogenic mutations in the serine/threonine kinase B-RAF (also known as BRAF) are found in 50-70% of malignant melanomas. Pre-clinical studies have demonstrated that the B-RAF(V600E) mutation predicts a dependency on the mitogen-activated protein kinase (MAPK) signalling cascade in melanoma-an observation that has been validated by the success of RAF and MEK inhibitors in clinical trials. However, clinical responses to targeted anticancer therapeutics are frequently confounded by de novo or acquired resistance. Identification of resistance mechanisms in a manner that elucidates alternative 'druggable' targets may inform effective long-term treatment strategies. Here we expressed ∼600 kinase and kinase-related open reading frames (ORFs) in parallel to interrogate resistance to a selective RAF kinase inhibitor. We identified MAP3K8 (the gene encoding COT/Tpl2) as a MAPK pathway agonist that drives resistance to RAF inhibition in B-RAF(V600E) cell lines. COT activates ERK primarily through MEK-dependent mechanisms that do not require RAF signalling. Moreover, COT expression is associated with de novo resistance in B-RAF(V600E) cultured cell lines and acquired resistance in melanoma cells and tissue obtained from relapsing patients following treatment with MEK or RAF inhibitors. We further identify combinatorial MAPK pathway inhibition or targeting of COT kinase activity as possible therapeutic strategies for reducing MAPK pathway activation in this setting. Together, these results provide new insights into resistance mechanisms involving the MAPK pathway and articulate an integrative approach through which high-throughput functional screens may inform the development of novel therapeutic strategies.
Broad Institute of Harvard and Massachusetts Institute of Technology, 7 Cambridge Center, Cambridge, Massachusetts 02142, USA.
Cory M
CM
Johannessen
Jesse S
JS
Boehm
So Young
SY
Kim
Sapana R
SR
Thomas
Leslie
L
Wardwell
Laura A
LA
Johnson
Caroline M
CM
Emery
Nicolas
N
Stransky
Alexandria P
AP
Cogdill
Jordi
J
Barretina
Giordano
G
Caponigro
Haley
H
Hieronymus
Ryan R
RR
Murray
Kourosh
K
Salehi-Ashtiani
David E
DE
Hill
Marc
M
Vidal
Jean J
JJ
Zhao
Xiaoping
X
Yang
Ozan
O
Alkan
Sungjoon
S
Kim
Jennifer L
JL
Harris
Christopher J
CJ
Wilson
Vic E
VE
Myer
Peter M
PM
Finan
David E
DE
Root
Thomas M
TM
Roberts
Todd
T
Golub
Keith T
KT
Flaherty
Reinhard
R
Dummer
Barbara L
BL
Weber
William R
WR
Sellers
Robert
R
Schlegel
Jennifer A
JA
Wargo
William C
WC
Hahn
Levi A
LA
Garraway
D000494:Allosteric Regulation; D045744:Cell Line, Tumor; D002986:Clinical Trials as Topic; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D015723:Gene Library; D006801:Humans; D007211:Indoles / Q000494:pharmacology / Q000627:therapeutic use; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008545:Melanoma / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016366:Open Reading Frames / Q000235:genetics; D047428:Protein Kinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology / Q000627:therapeutic use; D000077484:Vemurafenib
D007211:Indoles; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D013449:Sulfonamides; D000077484:Vemurafenib; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C069937:MAP3K8 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases