Systematic analysis of BRAFV600E melanomas reveals a role for JNK/c‐Jun pathway in adaptive resistance to drug‐induced apoptosis

摘要

AbstractDrugs that inhibit RAF/MEK signaling, such as vemurafenib, elicit profound but often temporary anti-tumor responses in patients with BRAFV600E melanoma. Adaptive responses to RAF/MEK inhibition occur on a timescale of hours to days, involve homeostatic responses that reactivate MAP kinase signaling and compensatory mitogenic pathways, and attenuate the anti-tumor effects of RAF/MEK inhibitors. We profile adaptive responses across a panel of melanoma cell lines using multiplex biochemical measurement, single-cell assays, and statistical modeling and show that adaptation involves at least six signaling cascades that act to reduce drug potency (IC₅₀) and maximal effect (i.e., E_max ≪ 1). Among these cascades, we identify a role for JNK/c-Jun signaling in vemurafenib adaptation and show that RAF and JNK inhibitors synergize in cell killing. This arises because JNK inhibition prevents a subset of cells in a cycling population from becoming quiescent upon vemurafenib treatment, thereby reducing drug E_max. Our findings demonstrate the breadth and diversity of adaptive responses to RAF/MEK inhibition and a means to identify which steps in a signaling cascade are most predictive of phenotypic response.SynopsisAdaptive responses to RAF/MEK inhibitors are analyzed systematically across a panel of BRAFV600E melanoma lines to reveal a role for cell-to-cell variability induced by the JNK/c-Jun pathway and other factors in adaptive drug resistance.Adaptive responses are profiled using a combination of multiplex measurements across time, dose, cell line and drug type, statistical modeling and single-cell analysis.BRAFV600E melanoma lines differ in sensitivity to RAF/MEK inhibition with respect to both IC₅₀ and maximal effect (E_max), reflecting cell-to-cell variability in drug response.Adaptive responses to RAF/MEK inhibition are diverse and involve multiple signaling pathways.The JNK/c-Jun pathway is a common adaptive response that decreases drug maximum effect.JNK inhibition prevents induction of quiescence by RAF inhibition and promotes apoptosis.