Abstract 4761: Defining the adaptive kinome response to BRAF and MEK inhibition in melanoma
Authors: Angus Steven P. , Stuhlmiller Timothy J. , Reuther Rachel , Pham Trang T. , Granger Deborah A. , Darr David B. , Jordan Jamie L. , Moschos Stergios J. , Johnson Gary L. , Sharpless Norman E. 
Published: May 2015

Abstract
Early clinical studies have shown that concurrent administration of BRAF and MEK inhibitors, dabrafenib and trametinib, is more active in patients with BRAFV600E/K melanoma than either single agent alone. Even though the combination of BRAF/MEK inhibitors is initially highly effective in treating melanoma in a subset of patients, progression to resistance ultimately occurs–commonly via reactivation of the BRAF/MEK/ERK pathway. Therefore, therapeutic strategies to counter primary resistance and prevent the emergence of secondary resistance are needed. Following pharmacological or progressive genetic perturbations, dynamic and system-wide adaptive changes (“reprogramming”) in the expression and activity of multiple kinases (collectively termed the kinome) clearly occur in tumor cells. Rich networks of serine/threonine and tyrosine kinases, many of which are understudied, are integrated into the signaling systems controlled by oncogenes known to drive melanoma. Thus, a comprehensive understanding of the kinome at baseline, during the adaptive response to kinase inhibitor treatment, and in the context of acquired resistance is critical. We use Multiplexed Inhibitor Beads (MIBs), mixtures of covalently immobilized, linker-adapted kinase inhibitors coupled with mass spectrometry (MS), to assess changes in activation of kinases in untreated samples, during acute inhibition of BRAF and/or MEK and in the context of acquired resistance. Our enhanced MIB/MS technology allows us to study over 75-80% of the expressed kinome (and numerous lipid and metabolic kinases) simultaneously using lysates from cell lines, genetically engineered mouse model (GEMM) tumors, patient-derived xenografts or human melanoma. We have identified several kinases (e.g. PDGFRβ, DDR1, MAP3K1) that are activated upon acute treatment with dabrafenib, trametinib, or dabrafenib/trametinib as well as in drug-resistant human melanoma cells and BRAFV600E/PTEN-/- GEMM-derived tumors and cell lines. Thus, studies using MIB/MS to measure dynamic kinome responses have identified kinases that have not been previously shown to be involved in the adaptive response to BRAF and/or MEK inhibition. We are currently targeting kinases involved in adaptive kiome reprogramming, pharmacologically or by RNAi, to determine whether their activation leads to vulnerability. This work will lead to the identification of novel and rationally predicted therapies for patients with advanced melanoma.
Citation Format: Steven P. Angus, Timothy J. Stuhlmiller, Rachel Reuther, Trang T. Pham, Deborah A. Granger, David B. Darr, Jamie L. Jordan, Stergios J. Moschos, Gary L. Johnson, Norman E. Sharpless. Defining the adaptive kinome response to BRAF and MEK inhibition in melanoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4761. doi:10.1158/1538-7445.AM2014-4761