Activated RAS promotes dimerization of members of the RAF kinase family. ATP-competitive RAF inhibitors activate ERK signalling by transactivating RAF dimers. In melanomas with mutant BRAF(V600E), ...levels of RAS activation are low and these drugs bind to BRAF(V600E) monomers and inhibit their activity. This tumour-specific inhibition of ERK signalling results in a broad therapeutic index and RAF inhibitors have remarkable clinical activity in patients with melanomas that harbour mutant BRAF(V600E). However, resistance invariably develops. Here, we identify a new resistance mechanism. We find that a subset of cells resistant to vemurafenib (PLX4032, RG7204) express a 61-kDa variant form of BRAF(V600E), p61BRAF(V600E), which lacks exons 4-8, a region that encompasses the RAS-binding domain. p61BRAF(V600E) shows enhanced dimerization in cells with low levels of RAS activation, as compared to full-length BRAF(V600E). In cells in which p61BRAF(V600E) is expressed endogenously or ectopically, ERK signalling is resistant to the RAF inhibitor. Moreover, a mutation that abolishes the dimerization of p61BRAF(V600E) restores its sensitivity to vemurafenib. Finally, we identified BRAF(V600E) splicing variants lacking the RAS-binding domain in the tumours of six of nineteen patients with acquired resistance to vemurafenib. These data support the model that inhibition of ERK signalling by RAF inhibitors is dependent on levels of RAS-GTP too low to support RAF dimerization and identify a novel mechanism of acquired resistance in patients: expression of splicing isoforms of BRAF(V600E) that dimerize in a RAS-independent manner.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Many melanomas contain an activating mutation in BRAF: a substitution of glutamic acid for valine at amino acid 600 (the V600E mutation). The authors conducted a two-phase study to describe the ...activity of a new agent, PLX4032, that inhibits mutated BRAF. A total of 26 of 32 patients (81%) who received 960 mg of PLX4032 orally, twice daily, had a partial or complete response lasting for at least 19 months. Side effects included rash, arthralgia, fatigue, and keratoacanthoma.
Metastatic melanoma is an aggressive disease for which there are few effective therapies. The two therapies approved by the Food and Drug Administration, high-dose interleukin-2 and dacarbazine, are each associated with response rates of only 10 to 20% and a small percentage of complete responses; neither is thought to improve overall survival.
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In randomized trials, the median survival among patients treated with dacarbazine was less than 8 months.
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A search for mutations in a component of the mitogen-activated protein (MAP) kinase pathway in a large panel of common cancers revealed that 40 to 60% of melanomas, and 7 . . .
The aim of the current study was to report the efficacy of topical and systemic treatments for immune-related cutaneous adverse events (ircAEs) attributed to checkpoint inhibitors in an uncontrolled ...cohort of patients referred to oncodermatology clinics.
A retrospective analysis of patients with ircAEs evaluated by dermatologists from January 1, 2014, to December 31, 2017, at three tertiary care hospitals and cancer centers were identified through electronic medical records. Clinicopathologic characteristics, dermatologic therapy outcome, and laboratory data were analyzed.
A total of 285 patients (median age, 65 years range, 17 to 89 years) with 427 ircAEs were included: pruritus (n = 138; 32%), maculopapular rash (n = 120; 28%), psoriasiform rash (n = 22; 5%), and others (n = 147; 34%). Immune checkpoint inhibitor class was associated with ircAE phenotype (
= .007), where maculopapular rash was predominant in patients who received combination therapy. Severity of ircAEs was significantly reduced (mean Common Terminology Criteria for Adverse Events grade: 1.74
0.71;
< .001) with dermatologic interventions, including topical corticosteroids, oral antipruritics, and systemic immunomodulators. A total of 88 ircAEs (20%) were managed with systemic immunomodulators. Of these, 22 (25%) of 88 persisted or worsened. In seven patients with corticosteroid-refractory ircAEs, improvement resulted from targeted biologic immunomodulatory therapies that included rituximab and dupilumab. Serum interleukin-6 (IL-6) was elevated in 34 (52%) of 65 patients; grade 3 or greater ircAEs were associated with increased absolute eosinophils (odds ratio, 4.1; 95% CI, 1.3 to 13.4) and IL-10 (odds ratio, 23.8; 95% CI, 2.1 to 262.5); mean immunoglobulin E serum levels were greater in higher-grade ircAEs: 1,093 kU/L (grade 3), 245 kU/L (grade 2), and 112 kU/L (grade 1;
= .043).
Most ircAEs responded to symptom- and phenotype-directed dermatologic therapies, whereas biologic therapies were effective in patients with corticosteroid-refractory disease. Increased eosinophils, IL-6, IL-10, and immunoglobulin E were associated with ircAEs, and they may represent actionable therapeutic targets for immune-related skin toxicities.
B-RAF is the most frequently mutated protein kinase in human cancers. The finding that oncogenic mutations in BRAF are common in melanoma, followed by the demonstration that these tumours are ...dependent on the RAF/MEK/ERK pathway, offered hope that inhibition of B-RAF kinase activity could benefit melanoma patients. Herein, we describe the structure-guided discovery of PLX4032 (RG7204), a potent inhibitor of oncogenic B-RAF kinase activity. Preclinical experiments demonstrated that PLX4032 selectively blocked the RAF/MEK/ERK pathway in BRAF mutant cells and caused regression of BRAF mutant xenografts. Toxicology studies confirmed a wide safety margin consistent with the high degree of selectivity, enabling Phase 1 clinical trials using a crystalline formulation of PLX4032 (ref. 5). In a subset of melanoma patients, pathway inhibition was monitored in paired biopsy specimens collected before treatment initiation and following two weeks of treatment. This analysis revealed substantial inhibition of ERK phosphorylation, yet clinical evaluation did not show tumour regressions. At higher drug exposures afforded by a new amorphous drug formulation, greater than 80% inhibition of ERK phosphorylation in the tumours of patients correlated with clinical response. Indeed, the Phase 1 clinical data revealed a remarkably high 81% response rate in metastatic melanoma patients treated at an oral dose of 960 mg twice daily. These data demonstrate that BRAF-mutant melanomas are highly dependent on B-RAF kinase activity.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Tumor-derived exosomes are emerging mediators of tumorigenesis. We explored the function of melanoma-derived exosomes in the formation of primary tumors and metastases in mice and human subjects. ...Exosomes from highly metastatic melanomas increased the metastatic behavior of primary tumors by permanently 'educating' bone marrow progenitors through the receptor tyrosine kinase MET. Melanoma-derived exosomes also induced vascular leakiness at pre-metastatic sites and reprogrammed bone marrow progenitors toward a pro-vasculogenic phenotype that was positive for c-Kit, the receptor tyrosine kinase Tie2 and Met. Reducing Met expression in exosomes diminished the pro-metastatic behavior of bone marrow cells. Notably, MET expression was elevated in circulating CD45(-)C-KIT(low/+)TIE2(+) bone marrow progenitors from individuals with metastatic melanoma. RAB1A, RAB5B, RAB7 and RAB27A, regulators of membrane trafficking and exosome formation, were highly expressed in melanoma cells. Rab27A RNA interference decreased exosome production, preventing bone marrow education and reducing, tumor growth and metastasis. In addition, we identified an exosome-specific melanoma signature with prognostic and therapeutic potential comprised of TYRP2, VLA-4, HSP70, an HSP90 isoform and the MET oncoprotein. Our data show that exosome production, transfer and education of bone marrow cells supports tumor growth and metastasis, has prognostic value and offers promise for new therapeutic directions in the metastatic process.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
In BRAF V600E melanoma patients, RAF inhibitor treatment causes a MEK-inhibitor-sensitive, RAF-inhibitor-resistant adaptive reactivation of ERK signaling. In clinical trials combining MEK and RAF ...inhibitors, therapeutic efficacy was modestly enhanced, suggesting the utility of inhibiting feedback-reactivated pathways. Strategies for optimally inhibiting ERK signaling should be explored.
In BRAF V600E melanoma patients, RAF inhibitor treatment causes a MEK-inhibitor-sensitive, RAF-inhibitor-resistant adaptive reactivation of ERK signaling. In clinical trials combining MEK and RAF inhibitors, therapeutic efficacy was modestly enhanced, suggesting the utility of inhibiting feedback-reactivated pathways. Strategies for optimally inhibiting ERK signaling should be explored.
Summary Background Brain metastases are common in patients with metastatic melanoma and median overall survival from their diagnosis is typically 17–22 weeks. We assessed dabrafenib in patients with ...Val600Glu or Val600Lys BRAF-mutant melanoma metastatic to the brain. Methods We undertook a multicentre, open-label, phase 2 trial in 24 centres in six countries. We enrolled patients with histologically confirmed Val600Glu or Val600Lys BRAF-mutant melanoma and at least one asymptomatic brain metastasis (≥5 mm and ≤40 mm in diameter). Eligible patients were aged 18 years or older, had an Eastern Cooperative Oncology Group performance status of 0 or 1, and had adequate organ function. Patients were split into two cohorts: those in cohort A had not received previous local treatment for brain metastases and those in cohort B had progressive brain metastases after previous local treatments. Patients received 150 mg oral dabrafenib twice a day until disease progression, death, or unacceptable adverse events. The primary endpoint was the proportion of patients with Val600Glu BRAF-mutant melanoma who achieved an overall intracranial response, which was defined as a complete response or partial response assessed with a modified form of Response Evaluation Criteria in Solid Tumors (RECIST 1.1). We included patients who received at least one dose of dabrafenib in efficacy and safety analyses. This study is registered with ClinicalTrials.gov , number NCT01266967. Findings Between Feb 2, 2011, and Aug 5, 2011, we enrolled 172 patients: 89 (52%) in cohort A and 83 (48%) in cohort B. 139 (81%) had Val600Glu BRAF-mutant melanoma. 29 (39·2%, 95% CI 28·0–51·2) of 74 patients with Val600Glu BRAF-mutant melanoma in cohort A achieved an overall intracranial response, as did 20 (30·8%, 19·9–43·4) of 65 in cohort B. One (6·7%, 0·2–31·9) of 15 patients with Val600Lys BRAF-mutant melanoma achieved an overall intracranial response in cohort A, as did four (22·2%, 6·4–47·6) of 18 such patients in cohort B. Treatment-related adverse events of grade 3 or worse occurred in 38 (22%) patients. Eleven (6%) patients developed squamous-cell carcinoma (five 6% patients in cohort A, of whom one also had keratoacanthoma; six 7% in cohort B). Four grade 4 treatment-related adverse events occurred in cohort A: one blood amylase increase, one convulsion, one lipase increase, and one neutropenia. Two grade 4 events occurred in cohort B: one agranulocytosis and one intracranial haemorrhage. 51 (30%) patients had a serious adverse event. The three most frequent serious adverse events were pyrexia (ten 6% patients), intracranial haemorrhage (ten 6%; one treatment-related), and squamous-cell carcinoma (11 6%). Interpretation Dabrafenib has activity and an acceptable safety profile in patients with Val600Glu BRAF-mutant melanoma and brain metastases irrespective of whether they are untreated or have been previously treated but have progressed. Funding GlaxoSmithKline.
Summary Background Dabrafenib, an inhibitor of mutated BRAF, has clinical activity with a manageable safety profile in studies of phase 1 and 2 in patients with BRAFV600 -mutated metastatic melanoma. ...We studied the efficacy of dabrafenib in patients with BRAFV600E -mutated metastatic melanoma. Methods We enrolled patients in this open-label phase 3 trial between Dec 23, 2010, and Sept 1, 2011. This report is based on a data cutoff date of Dec 19, 2011. Patients aged 18 years or older with previously untreated, stage IV or unresectable stage III BRAFV600E mutation-positive melanoma were randomly assigned (3:1) to receive dabrafenib (150 mg twice daily, orally) or dacarbazine (1000 mg/m2 intravenously every 3 weeks). Patients were stratified according to American Joint Committee on Cancer stage (unresectable III+IVM1a+IVM1b vs IVM1c). The primary endpoint was investigator-assessed progression-free survival and was analysed by intention to treat; safety was assessed per protocol. This study is registered with ClinicalTrials.gov , number NCT01227889. Findings Of the 733 patients screened, 250 were randomly assigned to receive either dabrafenib (187 patients) or dacarbazine (63 patients). Median progression-free survival was 5·1 months for dabrafenib and 2·7 months for dacarbazine, with a hazard ratio (HR) of 0·30 (95% CI 0·18–0·51; p<0·0001). At data cutoff, 107 (57%) patients in the dabrafenib group and 14 (22%) in the dacarbazine group remained on randomised treatment. Treatment-related adverse events (grade 2 or higher) occurred in 100 (53%) of the 187 patients who received dabrafenib and in 26 (44%) of the 59 patients who received dacarbazine. The most common adverse events with dabrafenib were skin-related toxic effects, fever, fatigue, arthralgia, and headache. The most common adverse events with dacarbazine were nausea, vomiting, neutropenia, fatigue, and asthenia. Grade 3–4 adverse events were uncommon in both groups. Interpretation Dabrafenib significantly improved progression-free survival compared with dacarbazine. Funding GlaxoSmithKline.
The widespread adoption of immune checkpoint inhibitors and small molecule inhibitors of the MAP kinase pathway has transformed the management of locally advanced and metastatic melanoma. Here, we ...provide a broad overview on the use of these agents in the first-line setting, incorporating a review of the clinical literature as well as the practice patterns of our respective melanoma groups. Throughout, we highlight areas of uncertainty that provide opportunities for future clinical investigation and additional improvement in outcomes for patients with melanoma.
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