TY - JOUR
T1 - A novel AKT1 mutant amplifies an adaptive melanoma response to BRAF inhibition
AU - Shi, Hubing
AU - Hong, Aayoung
AU - Kong, Xiangju
AU - Koya, Richard C.
AU - Song, Chunying
AU - Moriceau, Gatien
AU - Hugo, Willy
AU - Yu, Clarissa C.
AU - Ng, Charles
AU - Chodon, Thinle
AU - Scolyer, Richard A.
AU - Kefford, Richard F.
AU - Ribas, Antoni
AU - Long, Georgina V.
AU - Lo, Roger S.
PY - 2014/1
Y1 - 2014/1
N2 - I BRAF inhibitor (BRAFi) therapy leads to remarkable anti melanoma responses, but the initial tumor shrinkage is commonly incomplete, providing a nidus for subsequent disease progression. Adaptive signaling may underlie early BRAFi resistance and influence the selection pattern for genetic variants, causing late, acquired resistance. We show here that BRAFi (or BRAFi + MEKi) therapy in patients frequently led to rebound phosphorylated AKT (p-AKT) levels in their melanomas early on-treatment. In cell lines, BRAFi treatment led to rebound levels of receptor tyrosine kinases (RTK; including PDGFRβ), phosphatidyl (3,4,5)-triphosphate (PIP 3), pleckstrin homology domain recruitment, and p-AKT. PTEN expression limited this BRAFi-elicited PI3K-AKT signaling, which could be rescued by the introduction of a mutant AKT1 (Q79K) known to confer acquired BRAFi resistance. Functionally, AKT1 Q79K conferred BRAFi resistance via amplifi cation of BRAFi-elicited PI3K-AKT signaling. In addition, mitogen-activated protein kinase pathway inhibition enhanced clonogenic growth dependency on PI3K or AKT. Thus, adaptive or genetic upregulation of AKT critically participates in melanoma survival during BRAFi therapy. SIGNIFICANCE: This study provides a mechanistic link between early, adaptive and late, acquired BRAF inhibitor resistance in melanoma, with early BRAFi-induced signaling alterations shaping the subsequent evolutionary selective pressure. These findings argue for upfront, combined targeting of the mutant BRAF genotype and a pervasive drug-adaptive, AKT-dependent tumor response.
AB - I BRAF inhibitor (BRAFi) therapy leads to remarkable anti melanoma responses, but the initial tumor shrinkage is commonly incomplete, providing a nidus for subsequent disease progression. Adaptive signaling may underlie early BRAFi resistance and influence the selection pattern for genetic variants, causing late, acquired resistance. We show here that BRAFi (or BRAFi + MEKi) therapy in patients frequently led to rebound phosphorylated AKT (p-AKT) levels in their melanomas early on-treatment. In cell lines, BRAFi treatment led to rebound levels of receptor tyrosine kinases (RTK; including PDGFRβ), phosphatidyl (3,4,5)-triphosphate (PIP 3), pleckstrin homology domain recruitment, and p-AKT. PTEN expression limited this BRAFi-elicited PI3K-AKT signaling, which could be rescued by the introduction of a mutant AKT1 (Q79K) known to confer acquired BRAFi resistance. Functionally, AKT1 Q79K conferred BRAFi resistance via amplifi cation of BRAFi-elicited PI3K-AKT signaling. In addition, mitogen-activated protein kinase pathway inhibition enhanced clonogenic growth dependency on PI3K or AKT. Thus, adaptive or genetic upregulation of AKT critically participates in melanoma survival during BRAFi therapy. SIGNIFICANCE: This study provides a mechanistic link between early, adaptive and late, acquired BRAF inhibitor resistance in melanoma, with early BRAFi-induced signaling alterations shaping the subsequent evolutionary selective pressure. These findings argue for upfront, combined targeting of the mutant BRAF genotype and a pervasive drug-adaptive, AKT-dependent tumor response.
UR - http://www.scopus.com/inward/record.url?scp=84891893623&partnerID=8YFLogxK
UR - http://purl.org/au-research/grants/nhmrc/633004
UR - http://purl.org/au-research/grants/nhmrc/1066735
U2 - 10.1158/2159-8290.CD-13-0279
DO - 10.1158/2159-8290.CD-13-0279
M3 - Article
VL - 4
SP - 69
EP - 79
JO - Cancer Discovery
JF - Cancer Discovery
SN - 2159-8274
IS - 1
ER -