MEK/MELK inhibition and blood–brain barrier deficiencies in atypical teratoid/rhabdoid tumors
Michaël H. MeelMíriam Guillén NavarroMark C. de GooijerDennis S. MetselaarPiotr WaraneckiMarjolein BreurTonny LagerweijLaurine E. WedekindJan KösterMarianne D. van de WeteringNetteke Schouten-van MeeterenEleonora AronicaOlaf van TellingenMarianna BugianiTimothy N. PhoenixGertjan J.L. KaspersEsther Hulleman
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Abstract:
Atypical teratoid/rhabdoid tumors (AT/RT) are rare, but highly aggressive. These entities are of embryonal origin occurring in the central nervous system (CNS) of young children. Molecularly these tumors are driven by a single hallmark mutation, resulting in inactivation of SMARCB1 or SMARCA4. Additionally, activation of the MAPK signaling axis and preclinical antitumor efficacy of its inhibition have been described in AT/RT.We established and validated a patient-derived neurosphere culture and xenograft model of sonic hedgehog (SHH) subtype AT/RT, at diagnosis and relapse from the same patient. We set out to study the vascular phenotype of these tumors to evaluate the integrity of the blood-brain barrier (BBB) in AT/RT. We also used the model to study combined mitogen-activated protein kinase kinase (MEK) and maternal embryonic leucine zipper kinase (MELK) inhibition as a therapeutic strategy for AT/RT.We found MELK to be highly overexpressed in both patient samples of AT/RT and our primary cultures and xenografts. We identified a potent antitumor efficacy of the MELK inhibitor OTSSP167, as well as strong synergy with the MEK inhibitor trametinib, against primary AT/RT neurospheres. Additionally, vascular phenotyping of AT/RT patient material and xenografts revealed significant BBB aberrancies in these tumors. Finally, we show in vivo efficacy of the non-BBB penetrable drugs OTSSP167 and trametinib in AT/RT xenografts, demonstrating the therapeutic implications of the observed BBB deficiencies and validating MEK/MELK inhibition as a potential treatment.Altogether, we developed a combination treatment strategy for AT/RT based on MEK/MELK inhibition and identify therapeutically exploitable BBB deficiencies in these tumors.Keywords:
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Abstract Erdheim-Chester disease (ECD) and Rosai-Dorfman disease (RDD) are rare non-Langerhans cell histiocytoses (non-LCHs), for which therapeutic options are limited. MAPK pathway activation through BRAFV600E mutation or other genomic alterations is a histiocytosis hallmark and correlates with a favorable response to BRAF inhibitors and the MEK inhibitor cobimetinib. However, there has been no systematic evaluation of alternative MEK inhibitors. To assess the efficacy and safety of the MEK inhibitor trametinib, we retrospectively analyzed the outcomes of 26 adult patients (17 with ECD, 5 with ECD/RDD, 3 with RDD, and 1 with ECD/LCH) treated with orally administered trametinib at 4 major US care centers. The most common treatment-related toxicity was rash (27% of patients). In most patients, the disease was effectively managed at low doses (0.5-1.0 mg trametinib daily). The response rate of the 17 evaluable patients was 71% (73% [8/11] without a detectable BRAFV600E achieving response). At a median follow-up of 23 months, treatment effects were durable, with a median time-to-treatment failure of 37 months, whereas the median progression-free and overall survival were not reached (at 3 years, 90.1% of patients were alive). Most patients harbored mutations in BRAF (either classic BRAFV600E or other BRAF alterations) or alterations in other genes involved in the MAPK pathway, eg, MAP2K, NF1, GNAS, or RAS. Most patients required lower than standard doses of trametinib but were responsive to lower doses. Our data suggest that the MEK inhibitor trametinib is an effective treatment for ECD and RDD, including those without the BRAFV600E mutation.
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Introduction: Aberrant MAPK pathway signaling is a hallmark of melanoma. Mitogen/extracellular signal-regulated kinase (MEK) 1/2 are integral components of MAPK signaling. Several MEK inhibitors have demonstrated activity as single agents and in combination with other therapies. Trametinib was the first MEK inhibitor approved for use in treatment of advanced BRAFV600 mutant melanoma as a single agent and in combination with BRAF inhibitor, dabrafenib.Areas covered: In this article, we discuss the underlying biology of MEK inhibition and its rationale in melanoma treatment with special emphasis on the clinical development of trametinib, from initial Phase I studies to randomized Phase II and III studies, both as monotherapy and in combination with other therapeutics. Furthermore, we briefly comment on trametinib for NRAS mutant and other non-BRAF mutant subsets of melanoma.Expert opinion: Trametinib is a novel oral MEK inhibitor with clinical activity in BRAFV600 mutant metastatic melanoma alone and in combination with dabrafenib. Trametinib is currently being explored in other genetic subsets as well, particularly those with NRAS mutations or atypical BRAF alterations. Furthermore, to maximize efficacy and overcome acquired resistance, studies evaluating the combination of trametinib with other targeted agents and immunotherapy are underway.
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Introduction: Melanoma is the most aggressive of the cutaneous malignancies and caused over 35,000 deaths worldwide in 2013. Treatment options have been greatly expanded by the development of effective small-molecule inhibitors which target recurrent somatic mutations in melanoma (e.g., in BRAF and NRAS). Trametinib (GSK1120212) is an inhibitor of MEK1/2 which has received regulatory approval for the treatment of advanced BRAFV600-mutant melanoma. Trametinib has also demonstrated preclinical and early clinical activities as a single agent and in combination with other targeted therapies for melanoma with NRAS mutations in BRAF/NRAS wild-type melanoma.Areas covered: This article reviews melanoma genetics with a focus on MAPK signaling, and the preclinical and clinical evidence for treatment of melanoma with trametinib. The focus will be on a Phase III study of trametinib in BRAFV600-mutant melanoma, a Phase I/II study combining this agent with dabrafenib (a BRAF inhibitor) and most recently on a Phase III placebo-controlled trial assessing this combination. Finally, we will explore the role of trametinib in other, non-BRAF mutant subsets of this disease (e.g., NRAS mutations and atypical BRAF alterations) and in other malignancies.Expert opinion: Trametinib is a promising therapy which is playing a major role in combination with a BRAF inhibitor for the treatment of advanced BRAF-mutant melanoma. Increasing evidence suggests that trametinib will also play an expanding role in other genetically defined cohorts of this disease.
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Trametinib is a new anti-cancer drug that was developed by a cell-based phenotypic screening for the accumulation of CDK inhibitor p15INK4b and the growth inhibition in human colorectal cancer cell line HT-29 cells. Therefore, its molecular mechanism remained unknown at the beginning of the development process. To address this issue, we used a chemical biology approach. As a result, we identified MEK1/2 kinase as a molecular target by compound-immobilized affinity chromatography. Trametinib directly binds to MEK1 and MEK2, and allosterically inhibits their kinase activities. It was also shown that trametinib suppresses the phosphorylation status of MEK and ERK in HT-29 cells. We further confirmed that trametinib preferentially inhibits the growth of cancer cell lines harboring BRAF mutation and observed significant antitumor activity in a tumor xenograft model. In 2013, trametinib was approved as a first-in-class MEK inhibitor by the U.S. Food and Drug Administration for the treatment of metastatic melanoma with BRAF V600E or V600K mutations.
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Abstract: This review presents the current data on the efficacy and safety of the selective mitogen-activated extracellular signal-regulated kinase (MEK) inhibitor trametinib in patients with metastatic BRAF V600-positive melanoma. The pharmacological, safety, and efficacy data come from the Phase I, II, and III studies of trametinib monotherapy, as well as those in combination with the BRAF inhibitor dabrafenib. The most common adverse effects of trametinib therapy are rash, dermatitis, diarrhea, and fatigue. The Phase III METRIC study showed significant improvement in overall survival and progression-free survival in favor of trametinib over standard dacarbazine or paclitaxel chemotherapy. Therefore, trametinib was approved by the US Food and Drug Administration and European Medicines Agency as a single agent for the treatment of patients with V600E -mutated metastatic melanoma. Progression-free survival and response rates for trametinib monotherapy were lower than those noted with BRAF inhibitors. The second step in developing trametinib was to use the combination of trametinib with the BRAF inhibitor, eg, dabrafenib, to postpone the progression on MEK or BRAF inhibitors. The recently published data showed significant improvement in overall survival and progression-free survival in favor of the combination of trametinib and dabrafenib over vemurafenib therapy or dabrafenib alone, with good tolerance. The US Food and Drug Administration has approved the combination of dabrafenib (150 mg orally twice daily) and trametinib (2 mg orally once daily) for the treatment of patients with BRAF V600E/K -mutant metastatic melanoma, and their use seems to be currently the best approach. While BRAF-MEK inhibition is a standard, molecular targeted therapy in BRAF -mutated melanomas, its future utility has to be established in the rapidly changing landscape of immunotherapeutics. Keywords: trametinib, MEK inhibitor, dabrafenib, melanoma, BRAF mutation
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Molecularly targeted therapy with MEK inhibitors has been increasingly incorporated into the treatment of pediatric low-grade gliomas, but this promising therapy is associated with distinctive and specific toxicities. Understanding life-threatening MEK inhibitor toxicities and their management is critical to MEK inhibitor safety, especially among young children. This report describes severe hyponatremia associated with trametinib in an infant with progressive low-grade glioma without underlying endocrine dysfunction, which recurred despite significant dose reduction. Therapy with an alternative MEK inhibitor, binimetinib, provided excellent tumor response without hyponatremia, suggesting that some toxicities may be avoided by changing MEK inhibitor agents within the same class.
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Abstract Introduction: Mutant KRAS is feature of more than 25% of non-small cell lung cancers (NSCLC) and exemplifies one of the most popular oncogenic drivers. Ras-driven tumors are often hard to cure with conventional therapies and are necessary novel treatment strategies. Experiment: Using the HSP90 inhibitor NVP-AUY922, we investigated the potential of HSP90 inhibition to overcome the resistance to Trametinib, MEK inhibitor, in lung cancers harboring K-RAS mutant cell lines (H23, H358, H647, H1944, and A549). The synergistic effect of AUY-922 and trametinib was determined by analysis of the combination index (CI). After performing western blotting, we underwent following xenograft study with 6-week-old Balb/c-nu/nu female using H649 and H1944 cell lines. The mice were randomized into groups of 5, and NVP-AUY922 (5 mg/kg) was administered 3 days/week and GSK1120212 (300 μg/kg) was administered 5 days/week for up to 21 days in total. Result: NSCLC cells harboring G13D KRAS mutation showed intrinsic MEK inhibitor resistance via PI3K activation by highly expressed AKT as a bypass pathway. And then, HSP90 inhibitor AUY-922 suppresses both PI3K-AKT-mTOR and RAF-MEK-ERK reactivated by MEK inhibitor GSK1120212 and finally AUY-922 renders intrinsic MEK inhibitor resistant NSCLC cells sensitive to GSK1120212 with significant synergy. Furthermore, we showed this synergistic effect is occurred on sub-effective dose of either drug. Conclusion: The dual inhibition of HSP90 and MEK signaling pathways on sub-effective dose may constitute a potent therapeutic strategy to treat intrinsic MEK inhibitor resistant G13DKRAS mutant NSCLCs for resolving toxicity problem of dual inhibition of AKT and MEK in clinical trials. Citation Format: Dae Ho Lee, Kang-Seo Park, Bora Oh, Mi-Hee Lee, Hannah Yang. HSP90 inhibitor NVP-AUY922 sensitizes intrinsic MEK inhibitor Trametinib-resistant NSCLC cells harboring KRAS mutation. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B90.
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The retinoblastoma gene (RB) was discovered as the first tumor-suppressor gene. It was subsequently shown to be inactivated in most malignant tumors, particularly at the protein level. Therefore, many activated oncogenes as well as inactivated tumor-suppressor genes inactivate the function of the RB protein. I hypothesized that most of the molecular-targeting agents against activated oncogenes may reactivate the function of RB, and proposed screening systems for agents up-regulating the expression of cyclin-dependent kinase inhibitors, such as p15, p27, and p21, which convert the phosphorylated inactive form of the RB protein to the unphosphorylated active form. I termed this screening as "RB-reactivator screening". Using the screening systems for agents that up-regulate the expression of p15, p27, and p21, we discovered the novel MEK inhibitor trametinib, the novel RAF/MEK inhibitor CH5126766/RO5126766/VS-6766, and the histone deacetylase inhibitor YM753/OBP-801, respectively. Trametinib exerted remarkable effects in patients with advanced BRAF mutant melanoma, and was approved in the USA as the first-in-class MEK inhibitor (trade name: Mekinist) in 2013. The British Pharmacological Society selected trametinib as the Drug Discovery of the Year in 2013. The combination of trametinib and the BRAF inhibitor dabrafenib was approved for advanced BRAF mutant melanoma in the USA, EU, Japan, and many other countries. Additionally, the US Food and Drug Administration (FDA) granted Breakthrough Therapy Designation for the combination of trametinib and dabrafenib in the treatment of patients with advanced BRAF mutant non-small cell lung cancer in 2015, and this combination was subsequently approved in the EU, USA, and Japan. In 2018, this combination was also approved for locally advanced or metastatic BRAF V600-mutant anaplastic thyroid cancer in the USA after it had been granted Breakthrough Therapy Designation by the FDA. I describe here the characterization of our original screening system, RB-reactivator screening, by which these three molecular-targeting agents that advanced into clinical trials were identified.
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Abstract Mitogen-activated protein kinase/ERK signaling pathway has been one of the major mechanisms underlying melanoma haboring BRAF mutation. Of these, K601E mutation belongs to a rare mutation sub-type, comprising only 3% of the BRAF mutations in melanoma. Although patients with BRAF V600E/K mutation respond to MEK inhibitor, whether it also applies to those with BRAF K601E mutation remains elusive. Here, we examined the effects of MEK and BRAF/MEK inhibition on BRAFK601E-expressing melanoma cells. Melanoma cell line (MeWo) was transfected with doxycycline-inducible vector encoding wild-type or K601E-mutant BRAF. Subsequently, cells or xenograft-bearing mice were treated with trametinib, dabrafenib plus trametinib or sorafenib plus trametinib. Compared with BRAFWT, MTT assay demonstrated that BRAFK601E cells were more sensitive towards drug treatment. The effects of combined treatment were more profound. Tumorigenicity assay showed that trametinib treatment inhibited tumor growth of BRAFK601E xenografts. Our preliminary results demonstrated the therapeutic values of MEK and BRAF/MEK inhibitors against BRAFK601E-mutated melanoma. As previous studies report the superior therapeutic effects of BRAF/MEK inhibitors over MEK inhibitor alone, phenotype characterization of the cells, as well as underlying mechanisms behind such response, worth further investigation. Citation Format: Sze Man Chan, Sin Ting Chow, Sai Fung Yeung, Kwok Wing Stephen Tsui. Targeting MEK, alone and in combination with BRAF, in metastatic BRAFK601E-mutated melanoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5348.
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