Increased MAPK reactivation in early resistance to dabrafenib/trametinib combination therapy of BRAF-mutant metastatic melanoma (original) (raw)
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Cancer discovery, 2014
Treatment of BRAF-mutant melanoma with combined dabrafenib and trametinib, which target RAF and the downstream MAP-ERK kinase (MEK)1 and MEK2 kinases, respectively, improves progression-free survival and response rates compared with dabrafenib monotherapy. Mechanisms of clinical resistance to combined RAF/MEK inhibition are unknown. We performed whole-exome sequencing (WES) and whole-transcriptome sequencing (RNA-seq) on pretreatment and drug-resistant tumors from five patients with acquired resistance to dabrafenib/trametinib. In three of these patients, we identified additional mitogen-activated protein kinase (MAPK) pathway alterations in the resistant tumor that were not detected in the pretreatment tumor, including a novel activating mutation in MEK2 (MEK2(Q60P)). MEK2(Q60P) conferred resistance to combined RAF/MEK inhibition in vitro, but remained sensitive to inhibition of the downstream kinase extracellular signal-regulated kinase (ERK). The continued MAPK signaling-based re...
2013
Although BRAF and MEK inhibitors have proven clinical benefits in melanoma, most patients develop resistance. We report a de novo MEK2-Q60P mutation and BRAF gain in a melanoma from a patient who progressed on the MEK inhibitor trametinib and did not respond to the BRAF inhibitor dabrafenib. We also identified the same MEK2-Q60P mutation along with BRAF amplification in a xenograft tumor derived from a second melanoma patient resistant to the combination of dabrafenib and trametinib. Melanoma cells chronically exposed to trametinib acquired concurrent MEK2-Q60P mutation and BRAF-V600E amplification, which conferred resistance to MEK and BRAF inhibitors. The resistant cells had sustained MAPK activation and persistent phosphorylation of S6K. A triple combination of dabrafenib, trametinib, and the PI3K/mTOR inhibitor GSK2126458 led to sustained tumor growth inhibition. Hence, concurrent genetic events that sustain MAPK signaling can underlie resistance to both BRAF and MEK inhibitors, requiring novel therapeutic strategies to overcome it.
MAPK pathway in melanoma part II-secondary and adaptive resistance mechanisms to BRAF inhibition
European journal of cancer (Oxford, England : 1990), 2017
BRAF mutation can be identified in about 45% of the patients with metastatic melanoma. In these patients, BRAF and MEK inhibitors are able to induce rapid responses and to prolong survival. However, a significant percentage of patients will develop resistance to targeted therapy and will have progressive disease. MAPK pathway is the most important pathway involved in BRAF/MEK inhibition resistance, particularly MAPK pathway reactivation. Resistance mechanisms can be classified as 1) primary or intrinsic characterised by no response to therapy, 2) secondary or acquired with MAPK pathway reactivation after a time of tumour regression and 3) as adaptive with initial response and early resistance. BRAF inhibition also alters the immune response. Several publications have described immune effects of BRAF inhibition in melanoma tumours, showing that combining targeted and immunotherapy can improve response, despite a possible cross-resistance. Here, we continue the review on resistance me...
Preexisting MEK1P124 mutations diminish response to BRAF inhibitors in metastatic melanoma patients
Clinical cancer research : an official journal of the American Association for Cancer Research, 2015
MEK1 mutations in melanoma can confer resistance to BRAF inhibitors, although preexisting MEK1(P124) mutations do not preclude clinical responses. We sought to determine whether recurrent, preexisting MEK1(P124) mutations affected clinical outcome in BRAF inhibitor-treated patients with melanoma. Data from four published datasets were analyzed to determine whether preexisting MEK1(P124) mutations affect radiologic response or progression-free survival (PFS) in patients with BRAF(V600)-mutant metastatic melanoma treated with vemurafenib or dabrafenib. The effects of MEK1(P124) mutations on MAPK pathway activity and response to BRAF inhibition were also investigated in a series of cell models. In a pooled analysis of 123 patients, the presence of a pretreatment MEK1(P124) mutation (N = 12, 10%) was associated with a poorer RECIST response (33% vs. 72% in MEK1(P124Q/S) vs. MEK1(P124) wild-type, P = 0.018), and a shorter PFS (median 3.1 vs. 4.8 months, P = 0.004). Furthermore, MEK1(P124...
Background: MEK1 mutations in melanoma can confer resistance to BRAF inhibitors, although preexisting MEK1P124 mutations do not preclude clinical responses. We sought to determine whether recurrent, preexisting MEK1P124 mutations affected clinical outcome in BRAF inhibitor–treated patients with melanoma.Methods: Data from four published datasets were analyzed to determine whether preexisting MEK1P124 mutations affect radiologic response or progression-free survival (PFS) in patients with BRAFV600-mutant metastatic melanoma treated with vemurafenib or dabrafenib. The effects of MEK1P124 mutations on MAPK pathway activity and response to BRAF inhibition were also investigated in a series of cell models.Results: In a pooled analysis of 123 patients, the presence of a pretreatment MEK1P124 mutation (N = 12, 10%) was associated with a poorer RECIST response (33% vs. 72% in MEK1P124Q/S vs. MEK1P124 wild-type, P = 0.018), and a shorter PFS (median 3.1 vs. 4.8 months, P = 0.004). Furthermor...
BRAFL597 Mutations in Melanoma Are Associated with Sensitivity to MEK Inhibitors
Cancer Discovery, 2012
Kinase inhibitors are accepted treatment for metastatic melanomas that harbor specifi c driver mutations in BRAF or KIT, but only 40% to 50% of cases are positive. To uncover other potential targetable mutations, we conducted whole-genome sequencing of a highly aggressive BRAF (V600) and KIT (W557, V559, L576, K642, and D816) wild-type melanoma. Surprisingly, we found a somatic BRAF L597R mutation in exon 15. Analysis of BRAF exon 15 in 49 tumors negative for BRAF V600 mutations as well as driver mutations in KIT, NRAS, GNAQ, and GNA11, showed that two (4%) harbored L597 mutations and another two involved BRAF D594 and K601 mutations. In vitro signaling induced by L597R/S/Q mutants was suppressed by mitogenactivated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibition. A patient with BRAF L597S mutant metastatic melanoma responded signifi cantly to treatment with the MEK inhibitor, TAK-733. Collectively, these data show clinical signifi cance to BRAF L597 mutations in melanoma. SIGNIFICANCE: This study shows that cells harboring BRAF L597 mutants are sensitive to MEK inhibitor treatment, providing a rationale for routine screening and therapy of BRAF L597-mutant melanoma.
2023
Background: MEK1 mutations in melanoma can confer resistance to BRAF inhibitors, although preexisting MEK1 P124 mutations do not preclude clinical responses. We sought to determine whether recurrent, preexisting MEK1 P124 mutations affected clinical outcome in BRAF inhibitor-treated patients with melanoma. Methods: Data from four published datasets were analyzed to determine whether preexisting MEK1 P124 mutations affect radiologic response or progression-free survival (PFS) in patients with BRAF V600-mutant metastatic melanoma treated with vemurafenib or dabrafenib. The effects of MEK1 P124 mutations on MAPK pathway activity and response to BRAF inhibition were also investigated in a series of cell models. Results: In a pooled analysis of 123 patients, the presence of a pretreatment MEK1 P124 mutation (N ¼ 12, 10%) was associated with a poorer RECIST response (33% vs. 72% in MEK1 P124Q/S vs. MEK1 P124 wild-type, P ¼ 0.018), and a shorter PFS (median 3.1 vs. 4.8 months, P ¼ 0.004). Furthermore, MEK1 P124Q/S mutations were shown to have independent kinase activity and introduction of these mutations into a BRAF-mutant melanoma cell line diminished inhibition of ERK phosphorylation by dabrafenib and enhanced clonogenic survival in the presence of dabrafenib compared with cells ectopically expressing wild-type MEK1. Consistent with these data, two BRAF-mutant cell lines with endogenous MEK1 P124 mutations showed intermediate sensitivity to dabrafenib, but were highly sensitive to downstream inhibition of MEK or ERK. Conclusion: Taken together, our data indicate that preexisting MEK1 P124 mutations are associated with a reduced response to BRAF inhibitor therapy and identify a subset of patients with BRAF-mutant melanoma likely to benefit from combination therapies involving MEK or ERK inhibitors. Clin Cancer Res; 21(1); 98-105. Ó2014 AACR.
Cancer Discovery, 2012
BRAF inhibitors (BRAFi) induce antitumor responses in nearly 60% of patients with advanced V600E/K BRAF melanomas. Somatic activating MEK1 mutations are thought to be rare in melanomas, but their potential concurrence with V600E/K BRAF may be selected for by BRAFi. We sequenced MEK1/2 exon 3 in melanomas at baseline and upon disease progression. Of 31 baseline V600E/K BRAF melanomas, 5 (16%) carried concurrent somatic BRAF/MEK1 activating mutations. Three of 5 patients with BRAF/MEK1 double-mutant baseline melanomas showed objective tumor responses, consistent with the overall 60% frequency. No MEK1 mutation was found in disease progression melanomas, except when it was already identified at baseline. MEK1-mutant expression in V600E/K BRAF melanoma cell lines resulted in no significant alterations in p-ERK1/2 levels or growth-inhibitory sensitivities to BRAFi, MEK1/2 inhibitor (MEKi), or their combination. Thus, activating MEK1 exon 3 mutations identified herein and concurrent with V600E/K BRAF do not cause BRAFi resistance in melanoma.
Improved Survival with MEK Inhibition in BRAF-Mutated Melanoma
New England Journal of Medicine, 2012
Background Activating mutations in serine-threonine protein kinase B-RAF (BRAF) are found in 50% of patients with advanced melanoma. Selective BRAF-inhibitor therapy improves survival, as compared with chemotherapy, but responses are often short-lived. In previous trials, MEK inhibition appeared to be promising in this population. Methods In this phase 3 open-label trial, we randomly assigned 322 patients who had metastatic melanoma with a V600E or V600K BRAF mutation to receive either trametinib, an oral selective MEK inhibitor, or chemotherapy in a 2:1 ratio. Patients received trametinib (2 mg orally) once daily or intravenous dacarbazine (1000 mg per square meter of body-surface area) or paclitaxel (175 mg per square meter) every 3 weeks. Patients in the chemotherapy group who had disease progression were permitted to cross over to receive trametinib. Progression-free survival was the primary end point, and overall survival was a secondary end point. Results Median progression-free survival was 4.8 months in the trametinib group and 1.5 months in the chemotherapy group (hazard ratio for disease progression or death in the trametinib group, 0.45; 95% confidence interval [CI], 0.33 to 0.63; P<0.001). At 6 months, the rate of overall survival was 81% in the trametinib group and 67% in the chemotherapy group despite crossover (hazard ratio for death, 0.54; 95% CI, 0.32 to 0.92; P = 0.01). Rash, diarrhea, and peripheral edema were the most common toxic effects in the trametinib group and were managed with dose interruption and dose reduction; asymptomatic and reversible reduction in the cardiac ejection fraction and ocular toxic effects occurred infrequently. Secondary skin neoplasms were not observed. Conclusions Trametinib, as compared with chemotherapy, improved rates of progression-free and overall survival among patients who had metastatic melanoma with a BRAF V600E or V600K mutation. (Funded by GlaxoSmithKline; METRIC ClinicalTrials .gov number, NCT01245062.
Systems Analysis of Adaptive Responses to MAP Kinase Pathway Blockade in BRAF Mutant Melanoma
PloS one, 2015
Fifty percent of cutaneous melanomas are driven by activated BRAFV600E, but tumors treated with RAF inhibitors, even when they respond dramatically, rapidly adapt and develop resistance. Thus, there is a pressing need to identify the major mechanisms of intrinsic and adaptive resistance and develop drug combinations that target these resistance mechanisms. In a combinatorial drug screen on a panel of 12 treatment-naïve BRAFV600E mutant melanoma cell lines of varying levels of resistance to mitogen-activated protein kinase (MAPK) pathway inhibition, we identified the combination of PLX4720, a targeted inhibitor of mutated BRaf, and lapatinib, an inhibitor of the ErbB family of receptor tyrosine kinases, as synergistically cytotoxic in the subset of cell lines that displayed the most resistance to PLX4720. To identify potential mechanisms of resistance to PLX4720 treatment and synergy with lapatinib treatment, we performed a multi-platform functional genomics analysis to profile the g...