American Association for Cancer Research
21598290cd130279-sup-supp_figs.pdf (1.13 MB)

Supplementary Figures from A Novel AKT1 Mutant Amplifies an Adaptive Melanoma Response to BRAF Inhibition

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journal contribution
posted on 2023-04-03, 20:46 authored by Hubing Shi, Aayoung Hong, Xiangju Kong, Richard C. Koya, Chunying Song, Gatien Moriceau, Willy Hugo, Clarissa C. Yu, Charles Ng, Thinle Chodon, Richard A. Scolyer, Richard F. Kefford, Antoni Ribas, Georgina V. Long, Roger S. Lo

PDF file 1160K, This file contains all supplementary data including key controls experiments for IHC, IHC data quantification, PDGFRbeta IHCs, Western blots of a large melanoma cell line panel, presentation of DTP and DTPP concepts, PDGFRbeta expression analysis of live vs. dead sub-populations, and additional clonogenic assays and drug titrations



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 (PIP3), 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, AKT1Q79K conferred BRAFi resistance via amplification 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. Cancer Discov; 4(1); 69–79. ©2013 AACR.See related commentary by Solit and Rosen, p. 27This article is highlighted in the In This Issue feature, p. 1