RESUMEN
The clinical significance of BRAF alterations in well-differentiated (WD) metastatic pancreatic neuroendocrine tumor (panNET) is unknown, but BRAF-mutated panNET could represent a subset characterized by an identifiable and clinically actionable driver. Following the identification of two patients with WD metastatic panNET whose tumors harbored BRAF mutations, we queried the MSK-IMPACT series of 80 patients with WD metastatic panNET for additional mutations in BRAF, and in other genes involved in RAS/ RTK/ PI3K signaling pathways. BRAF mutations were identified in six samples (7.5%): two tumors harbored V600E mutations, one tumor each expressed K601E, T599K, and T310I mutations, and one tumor expressed both G596D and E451K BRAF. Few additional actionable driver alterations were identified. To determine the ERK activating capability of four BRAF mutations not previously characterized, mutant constructs were tested in model systems. Biochemical characterization of BRAF mutations revealed both high and low activity mutants. Engineered cells expressing BRAF K601E and V600E were used for in vitro drug testing of RAF and MEK inhibitors currently in clinical use. BRAF K601E demonstrated reduced sensitivity to dabrafenib compared to BRAF V600E, but the combination of RAF plus MEK inhibition was effective in cells expressing this mutation. Herein, we describe the clinical course of a patient with BRAF K601E and a patient with BRAF V600E WD metastatic panNET, and the identification of four mutations in BRAF not previously characterized. The combined clinical and biochemical data support a potential role for RAF and MEK inhibitors, or a combination of these, in a selected panNET population.
Asunto(s)
Imidazoles/farmacología , Quinasas Quinasa Quinasa PAM , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Mutación Missense , Tumores Neuroendocrinos , Oximas/farmacología , Neoplasias Pancreáticas , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Proto-Oncogénicas B-raf , Sustitución de Aminoácidos , Animales , Línea Celular Tumoral , Humanos , Quinasas Quinasa Quinasa PAM/antagonistas & inhibidores , Quinasas Quinasa Quinasa PAM/genética , Quinasas Quinasa Quinasa PAM/metabolismo , Ratones , Células 3T3 NIH , Metástasis de la Neoplasia , Tumores Neuroendocrinos/tratamiento farmacológico , Tumores Neuroendocrinos/enzimología , Tumores Neuroendocrinos/genética , Tumores Neuroendocrinos/patología , Neoplasias Pancreáticas/tratamiento farmacológico , Neoplasias Pancreáticas/enzimología , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/patología , Proteínas Proto-Oncogénicas B-raf/antagonistas & inhibidores , Proteínas Proto-Oncogénicas B-raf/genética , Proteínas Proto-Oncogénicas B-raf/metabolismoRESUMEN
BRAFV600E hyperactivates ERK and signals as a RAF inhibitor-sensitive monomer. Although RAF inhibitors can produce impressive clinical responses in patients with mutant BRAF tumors, the mechanisms of resistance to these drugs are incompletely characterized. Here, we report a complete response followed by clinical progression in a patient with a BRAFV600E-mutant brain tumor treated with dabrafenib. Whole-exome sequencing revealed a secondary BRAFL514V mutation at progression that was not present in the pretreatment tumor. Expressing BRAFV600E/L514V induces ERK signaling, promotes RAF dimer formation, and is sufficient to confer resistance to dabrafenib. Newer RAF dimer inhibitors and an ERK inhibitor are effective against BRAFL514V-mediated resistance. Collectively, our results validate a novel biochemical mechanism of RAF inhibitor resistance mediated by a secondary mutation, emphasizing that, like driver mutations in cancer, the spectrum of mutations that drive resistance to targeted therapy are heterogeneous and perhaps emerge with a lineage-specific prevalence.Significance: In contrast to receptor tyrosine kinases, in which secondary mutations are often responsible for acquired resistance, second-site mutations in BRAF have not been validated in clinically acquired resistance to RAF inhibitors. We demonstrate a secondary mutation in BRAF (V600E/L514V) following progression on dabrafenib and confirm functionally that this mutation is responsible for resistance. Cancer Discov; 8(9); 1130-41. ©2018 AACR.See related commentary by Romano and Kwong, p. 1064This article is highlighted in the In This Issue feature, p. 1047.
Asunto(s)
Neoplasias Encefálicas/genética , Resistencia a Antineoplásicos , Mutación , Proteínas Proto-Oncogénicas B-raf/genética , Adolescente , Neoplasias Encefálicas/tratamiento farmacológico , Progresión de la Enfermedad , Humanos , Imidazoles/uso terapéutico , Masculino , Oximas/uso terapéutico , Multimerización de Proteína/efectos de los fármacos , Proteínas Proto-Oncogénicas B-raf/química , Secuenciación del ExomaRESUMEN
FMS-like tyrosine kinase-3 (FLT3) tyrosine kinase inhibitors (TKI) have been tested extensively to limited benefit in acute myeloid leukemia (AML). We hypothesized that FLT3/internal tandem duplication (ITD) leukemia cells exhibit mechanisms of intrinsic signaling adaptation to TKI treatment that are associated with an incomplete response. Here, we identified reactivation of ERK signaling within hours following treatment of FLT3/ITD AML cells with selective inhibitors of FLT3. When these cells were treated with inhibitors of both FLT3 and MEK in combination, ERK reactivation was abrogated and anti-leukemia effects were more pronounced compared with either drug alone. ERK reactivation was also observed following inhibition of other tyrosine kinase-driven cancer cells, including EGFR-mutant lung cancer, HER2-amplified breast cancer, and BCR-ABL leukemia. These studies reveal an adaptive feedback mechanism in tyrosine kinase-driven cancers associated with reactivation of ERK signaling in response to targeted inhibition. Cancer Res; 77(20); 5554-63. ©2017 AACR.
Asunto(s)
Leucemia Mieloide Aguda/tratamiento farmacológico , Leucemia Mieloide Aguda/enzimología , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Inhibidores de Proteínas Quinasas/farmacología , Animales , Protocolos de Quimioterapia Combinada Antineoplásica/farmacología , Benzamidas/administración & dosificación , Benzamidas/farmacología , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Difenilamina/administración & dosificación , Difenilamina/análogos & derivados , Difenilamina/farmacología , Femenino , Células HL-60 , Humanos , Células K562 , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patología , Ratones , Ratones Endogámicos NOD , Ratones SCID , Neoplasias/tratamiento farmacológico , Neoplasias/enzimología , Neoplasias/genética , Neoplasias/patología , Niacinamida/administración & dosificación , Niacinamida/análogos & derivados , Niacinamida/farmacología , Compuestos de Fenilurea/administración & dosificación , Compuestos de Fenilurea/farmacología , Inhibidores de Proteínas Quinasas/administración & dosificación , Distribución Aleatoria , Sorafenib , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
The effects of selective phosphoinositide 3-kinase (PI3K) and AKT inhibitors were compared in human tumor cell lines in which the pathway is dysregulated. Both caused inhibition of AKT, relief of feedback inhibition of receptor tyrosine kinases, and growth arrest. However, only the PI3K inhibitors caused rapid induction of cell death. In seeking a mechanism for this phenomenon, we found that PI3K inhibition, but not AKT inhibition, causes rapid inhibition of wild-type RAS and of RAF-MEK-ERK signaling. Inhibition of RAS-ERK signaling is transient, rebounding a few hours after drug addition, and is required for rapid induction of apoptosis. Combined MEK and AKT inhibition also promotes cell death, and in murine models of HER2(+) cancer, either pulsatile PI3K inhibition or combined MEK and AKT inhibition causes tumor regression. We conclude that PI3K is upstream of RAS and AKT and that pulsatile inhibition of both pathways is sufficient for effective antitumor activity.