Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.12.2 (MEK)
18,161 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Desmoglein 2 (Dsg2), a component of the desmosomal cell-cell adhesion structure, has been linked to invasion and metastasis in squamous cell carcinomas. However, it is unknown whether--and if so how--Dsg2 contributes to the malignant phenotype of keratinocytes. In this study, we addressed the consequences of Dsg2 overexpression under control of the involucrin promoter (Inv-Dsg2) in the epidermis of transgenic mice. These mice exhibited epidermal hyperkeratosis with slightly disrupted early and late differentiation markers, but intact epidermal barrier function. However, Inv-Dsg2 transgene expression was associated with extensive epidermal hyperplasia and increased keratinocyte proliferation in basal and suprabasal epidermal strata. Cultured Inv-Dsg2 keratinocytes showed enhanced cell survival in the anchorage-independent state that was critically dependent on EGF receptor activation and NF-kappaB activity. Consistent with the hyperproliferative and apoptosis-resistant phenotype of Inv-Dsg2 transgenic keratinocytes, we observed enhanced activation of multiple growth and survival pathways, including PI 3-kinase/AKT, MEK-MAPK, STAT3 and NF-kappaB, in the transgenic skin in situ. Finally, Inv-Dsg2 transgenic mice developed intraepidermal skin lesions resembling precancerous papillomas and were more susceptible to chemically induced carcinogenesis. In summary, overexpression of Dsg2 in epidermal keratinocytes deregulates multiple signaling pathways associated with increased growth rate, anchorage-independent cell survival, and the development of skin tumors in vivo.
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PMID:Suprabasal Dsg2 expression in transgenic mouse skin confers a hyperproliferative and apoptosis-resistant phenotype to keratinocytes. 1728 15

Mutations in genes encoding for proteins along the RAS-RAF-MEK-ERK pathway have been detected in a variety of tumor entities, including malignant melanoma, thyroid, colonic and ovarian carcinomas, and some sarcomas. Thus, a number of inhibitors of this pathway have been developed, whose antitumor potential is currently being assessed in different clinical trials. Up to now one drug of this category (vemurafenib) has been approved by the FDA and the European Commission for late-stage melanoma. Although these new targeted anticancer therapies are generally considered to be safe and well tolerated, certain toxicities have been attributed to them, with cutaneous side effects being perhaps the most frequent amongst them. Based on results of clinical trials and on case series, a distinct profile of cutaneous toxicity has been observed, which is similar to that of EGFR and multikinase inhibitors. As exanthema, palmar-plantar erythrodysesthesia syndrome, hyperkeratosis, xerosis, pruritus, photosensitivity, and paronychia, can be controlled in most cases with common conservative modalities, special attention should be given to the early detection of epithelial skin tumors (mainly keratoakanthomas) that can be induced during therapy with these agents. This report reviews all current published data on cutaneous side effects of RAS-RAF-MEK-ERK pathway inhibitors, and attempts to provide the clinician with clear hints for their management.
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PMID:Cutaneous side effects of inhibitors of the RAS/RAF/MEK/ERK signalling pathway and their management. 2254 Jan 51

Nonmalignant cutaneous findings associated with the use of vemurafenib have only recently been described in the literature. Patients receiving vemurafenib have exhibited cutaneous reactions including prominent follicular plugging, hand-foot skin reaction, exuberant seborrheic dermatitis-like hyperkeratosis of the face, keratosis pilaris, and diffuse spiny follicular hyperkeratosis. Many of these nonmalignant cutaneous findings are associated with abnormal follicular keratinization thought to be secondary to abnormal signaling of the mitogen-activated protein kinase pathway that occurs with the use of BRAF inhibitors. Whether underlying Ras mutations affect this abnormal signaling as in malignant lesions is still unknown. Different therapeutic options exist for these patients that may result in significant improvement in some of these nonmalignant cutaneous findings. Conservative treatment should focus on topical therapies such as topical retinoids or topical steroids. However, systemic therapies such as concomitant oral retinoids or MEK inhibitors should be considered for more severe or refractory cutaneous findings.
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PMID:Nonmalignant cutaneous findings associated with vemurafenib use in patients with metastatic melanoma. 2294 Apr 5

The development of targeted therapies has ushered in a new era in the management of melanoma. Inhibitors of the RAS-RAF-MEK-ERK pathway have taken the center stage with development at a rapid pace. Vemurafenib was recently approved by regulatory agencies, and other agents (e.g. dabrafenib) are in various stages of clinical testing. These agents are producing remarkable results for patients, but are also presenting new challenges. Clinical toxicities and drug resistance are topmost issues. Some of the most common and vivid representations of adverse events to these agents are the dermatologic manifestations. Published trials and initial observations reflect a toxicity profile (e.g. squamous cell carcinomas/keratoacanthomas, maculopapular rashes, hyperkeratosis) that is distinct from cutaneous toxicities from EGFR and mTOR inhibitors (acneiform rash, paronychia, xerosis). Their management extends beyond conservative treatment and includes specific physical and surgical treatment modalities, skill sets unique to dermatologists. All these pose significant challenges to clinicians, and sound knowledge of such toxicities and their management will likely result in improved patient outcomes and quality of life. In this manuscript, we provide an overview of the emerging scientific literature on dermatological adverse events arising out of BRAF inhibition.
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PMID:Dermatological adverse events from BRAF inhibitors: a growing problem. 2346 15

Epidermal naevi are common cutaneous mosaic disorders that occur in 0.1-0.3% of live births. They are subdivided into keratinocytic and organoid naevi, the latter including naevus sebaceus (NS). Typically, NS develops as a yellowish-orange plaque on the scalp, and represents a hamartoma containing epidermal, sebaceous and apocrine elements. The histological features of NS sampled in childhood include hyperkeratosis, acanthosis, increased sebaceous lobules, and primitive hair follicles. During puberty, most lesions develop more prominent sebaceous and apocrine components. Subsequently, secondary tumours may occur in around 25% of NS; most lesions are benign (e.g. trichoblastomas, syringocystadenoma papilliferum or other basaloid proliferations), although malignant tumours arising within NS can occur (< 1%). Recently, somatic mosaicism has been shown, with activating Ras mutations in HRAS or KRAS in NS lesional keratinocytes (but not in adjacent nonlesional skin or dermal fibroblasts). These mutations lead to constitutive activation of the RAF-MEK-ERK and phosphoinositide 3-kinase signalling pathways, and result in increased cellular proliferation. Similar but more extensive mosaicism underlies Schimmelpenning-Feuerstein-Mims syndrome. The most common mutation is c.37G>C (p.Gly13Arg) in HRAS, which is present in > 90% of NS. This mutation also seems to be present in NS cases that develop secondary tumours, although no additional mutations (second hit) or other genetic events have yet been identified. Treatment of NS often involves prophylactic surgical excision, but the recent identification of key epidermal signalling abnormalities underlying the cell proliferation means that future development of new medical treatments for NS that target the aberrant signalling pathways may also be feasible.
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PMID:Naevus sebaceus: a mosaic RASopathy. 2434 74

The clinical development of selective BRAF inhibitors for metastatic BRAF V600 mutant melanoma patients has been a major breakthrough in targeted therapeutics. Objective response rates of approximately 50% have been observed in the Phase III studies of the BRAF inhibitors vemurafenib and dabrafenib. The side effects can be relatively common, including proliferative skin toxicities. The latter range from hyperkeratosis and keratoacanthomas (KAs) to squamous cell carcinomas (SCCs) and new primary melanomas. In addition, case reports on the emergence of gastric/colonic polyps and RAS mutant malignancies have been described during BRAF inhibitor therapy. These events have been attributed to paradoxical activation of the MAPK pathway in BRAF wild-type cells exposed to selective BRAF inhibitors in addition to increased RAS activity. Combined BRAF and MEK inhibition appears to improve clinical outcomes and reduce cutaneous proliferation events as fewer KAs and SCCs have been observed with combination therapy. Next-generation pan-RAF inhibitors ('paradox breakers') and ERK inhibitors may further enhance clinical activity in metastatic BRAF-mutant melanoma patients and mitigate this paradoxical oncogenesis. Further investigation into the potential long-term effects of selective BRAF inhibitors is warranted as expanded use of these agents is expected in patients with BRAF-mutant melanoma and other malignancies.
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PMID:Long-term effects of BRAF inhibitors in melanoma treatment: friend or foe? 2445 13

Cardiofaciocutaneous (CFC) syndrome is a rare genetic disorder belonging to the group of RASopathies. It is typically characterized by congenital heart defects, short stature, dysmorphic craniofacial features, intellectual disability, failure to thrive, and ectodermal abnormalities such as hyperkeratosis and sparse, brittle, curly hair. CFC syndrome is caused by dominant mutations in one of the four genes BRAF, MEK1, MEK2, and KRAS. Only three familial cases of CFC syndrome have been reported to date, whereas the vast majorities are sporadic cases due to de novo mutations. We report on a fourth familial case with transmission of CFC syndrome from father to son due to a novel heterozygous sequence change c.376A>G (p.N126D) in exon 3 of MEK2 gene. This observation further documents the possibility of vertical transmission of CFC syndrome, which appears to be associated with rare mutations and relatively mild intellectual disability in affected individual. The hypomorphic effect of specific mutations particularly regarding neurocognitive issues may be related to the variable fertility of affected individuals.
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PMID:Familial cardiofaciocutaneous syndrome in a father and a son with a novel MEK2 mutation. 2548 61

A retrospective observational study was conducted on patients diagnosed with serine/threonine-protein kinase B-Raf (BRAF)-mutated metastatic melanoma, who underwent first-line therapy with BRAF and mitogen-activated protein kinase kinase (MEK) inhibitors (vemurafenib, dabrafenib or a combination of dabrafenib and trametinib) at the Miguel Servet University Hospital (Zaragoza, Spain) between November, 2011 and August, 2015. The aim of this study was to analyse the toxicity produced by BRAF and MEK inhibitors. The most common toxicities were similar to those published in clinical trials, particularly arthralgia, alopecia and photosensitivity in the vemurafenib group; asthenia, hyperkeratosis and dry skin in the dabrafenib group; and diarrhoea and dry skin in the dabrafenib plus trametinib group. Toxicities that had not been described in clinical trials were also identified. Thus, the present study confirmed that the results obtained in clinical trials are similar to those obtained in clinical practice.
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PMID:Comparative safety of BRAF and MEK inhibitors (vemurafenib, dabrafenib and trametinib) in first-line therapy for BRAF-mutated metastatic melanoma. 2769 43

The combination of MEK inhibitor (cobimetinib, trametinib) and BRAF inhibitor (vemurafenib, dabrafenib) is now the first-line treatment in patients with BRAF V600-mutated metastatic melanoma. This association reduces cutaneous adverse events induced by BRAF inhibitors alone, including photosensitivity, hand-foot syndrome, hyperkeratosis, alopecia, skin papillomas, keratoacanthomas, and squamous-cell carcinomas. While panniculitis has exceptionally been reported with BRAF inhibitors, this rare side effect has never been described with the use of MEK inhibitors. We present here the first observation of panniculitis strictly induced by MEK inhibitors. Indeed, 10 days after the initiation of combined treatment with cobimetinib and vemurafenib for metastatic melanoma, our patient developed panniculitis predominantly on the upper and lower extremities. These cutaneous nodules disappeared during cobimetinib intermissions and recurred while the molecule was resumed. Recurrence of cutaneous nodules was observed after initiation of trametinib combined with dabrafenib, and resolved once again with trametinib discontinuation. We believe that clinicians should be aware of this cutaneous adverse event in patients treated with combined therapy, which can lead to unfounded BRAF inhibitor treatment discontinuation and compromise the antitumor response. Our case suggests a class effect linked with the MEK inhibition pharmacodynamic activity. Finally, laboratory investigation and histopathological examination are mandatory to exclude other panniculitis etiologies and subcutaneous metastasis of melanoma.
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PMID:Panniculitis Associated with MEK Inhibitor Therapy: An Uncommon Adverse Effect. 2861 27

Germline mutations in BRAF are a major cause of cardio-facio-cutaneous (CFC) syndrome, which is characterized by heart defects, characteristic craniofacial dysmorphology and dermatologic abnormalities. Patients with CFC syndrome also commonly show gastrointestinal dysfunction, including feeding and swallowing difficulties and gastroesophageal reflux. We have previously found that knock-in mice expressing a Braf Q241R mutation exhibit CFC syndrome-related phenotypes, such as growth retardation, craniofacial dysmorphisms, congenital heart defects and learning deficits. However, it remains unclear whether BrafQ241R/+ mice exhibit gastrointestinal dysfunction. Here, we report that BrafQ241R/+ mice have neonatal feeding difficulties and esophageal dilation. The esophagus tissues from BrafQ241R/+ mice displayed incomplete replacement of smooth muscle with skeletal muscle and decreased contraction. Furthermore, the BrafQ241R/+ mice showed hyperkeratosis and a thickened muscle layer in the forestomach. Treatment with MEK inhibitors ameliorated the growth retardation, esophageal dilation, hyperkeratosis and thickened muscle layer in the forestomach in BrafQ241R/+ mice. The esophageal dilation with aberrant skeletal-smooth muscle boundary in BrafQ241R/+ mice were recovered after treatment with the histone H3K27 demethylase inhibitor GSK-J4. Our results provide clues to elucidate the pathogenesis and possible treatment of gastrointestinal dysfunction and failure to thrive in patients with CFC syndrome.
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PMID:Activated Braf induces esophageal dilation and gastric epithelial hyperplasia in mice. 2897 66


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