Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phacomatosis pigmentokeratotica (PPK) is a rare epidermal nevus syndrome characterized by the co-occurrence of a sebaceous nevus and a speckled lentiginous nevus. The coexistence of an epidermal and a melanocytic nevus has been explained by two homozygous recessive mutations, according to the twin spot hypothesis, of which PPK has become a putative paradigm in humans. However, the underlying gene mutations remained unknown. Multiple tissues of six patients with PPK were analyzed for the presence of RAS, FGFR3, PIK3CA, and BRAF mutations using SNaPshot assays and Sanger sequencing. We identified a heterozygous HRAS c.37G>C (p.Gly13Arg) mutation in four patients and a heterozygous HRAS c.182A>G (p.Gln61Arg) mutation in two patients. In each case, the mutations were present in both the sebaceous and the melanocytic nevus. In the latter lesion, melanocytes were identified to carry the HRAS mutation. Analysis of various nonlesional tissues showed a wild-type sequence of HRAS, consistent with mosaicism. Our data provide no genetic evidence for the previously proposed twin spot hypothesis. In contrast, PPK is best explained by a postzygotic-activating HRAS mutation in a multipotent progenitor cell that gives rise to both a sebaceous and a melanocytic nevus. Therefore, PPK is a mosaic RASopathy.
...
PMID:Phacomatosis pigmentokeratotica is caused by a postzygotic HRAS mutation in a multipotent progenitor cell. 2385 30

The development of malignant melanoma is a highly complex process, which is still poorly understood. A majority of human melanomas are found to express a few oncogenic proteins, such as mutant RAS and BRAF variants. However, these oncogenes are also found in nevi, and it is now a well-accepted fact that their expression alone leads to senescence. This renders the understanding of senescence escape mechanisms an important point to understand tumor development. Here, we approached the question of senescence evasion by expressing the transcription factor v-myc myelocytomatosis viral oncogene homolog (c-MYC), which is known to act synergistically with many oncogenes, in melanocytes. We observed that MYC drives the evasion of reactive-oxygen stress-induced melanocyte senescence, caused by activated receptor tyrosine kinase signaling. Conversely, MIZ1, the growth suppressing interaction partner of MYC, is involved in mediating melanocyte senescence. Both, MYC overexpression and Miz1 knockdown led to a strong reduction of endogenous reactive-oxygen species (ROS), DNA damage and senescence. We identified the cystathionase (CTH) gene product as mediator of the ROS-related MYC and MIZ1 effects. Blocking CTH enzymatic activity in MYC-overexpressing and Miz1 knockdown cells increased intracellular stress and senescence. Importantly, pharmacological inhibition of CTH in human melanoma cells also reconstituted senescence in the majority of cell lines, and CTH knockdown reduced tumorigenic effects such as proliferation, H2O2 resistance and soft agar growth. Thus, we identified CTH as new MYC target gene with an important function in senescence evasion.
...
PMID:Cystathionase mediates senescence evasion in melanocytes and melanoma cells. 2335 21

Congenital melanocytic nevi (CMN) can be associated with neurological abnormalities and an increased risk of melanoma. Mutations in NRAS, BRAF, and Tp53 have been described in individual CMN samples; however, their role in the pathogenesis of multiple CMN within the same subject and development of associated features has not been clear. We hypothesized that a single postzygotic mutation in NRAS could be responsible for multiple CMN in the same individual, as well as for melanocytic and nonmelanocytic central nervous system (CNS) lesions. From 15 patients, 55 samples with multiple CMN were sequenced after site-directed mutagenesis and enzymatic digestion of the wild-type allele. Oncogenic missense mutations in codon 61 of NRAS were found in affected neurological and cutaneous tissues of 12 out of 15 patients, but were absent from unaffected tissues and blood, consistent with NRAS mutation mosaicism. In 10 patients, the mutation was consistently c.181C>A, p.Q61K, and in 2 patients c.182A>G, p.Q61R. All 11 non-melanocytic and melanocytic CNS samples from 5 patients were mutation positive, despite NRAS rarely being reported as mutated in CNS tumors. Loss of heterozygosity was associated with the onset of melanoma in two cases, implying a multistep progression to malignancy. These results suggest that single postzygotic NRAS mutations are responsible for multiple CMN and associated neurological lesions in the majority of cases.
...
PMID:Multiple congenital melanocytic nevi and neurocutaneous melanosis are caused by postzygotic mutations in codon 61 of NRAS. 2777 49

The discovery that some melanoma tumours harbour mutations in the BRAF gene (e.g. V600E) and the subsequent development of specific BRAF inhibitors have greatly improved the treatment of metastatic melanoma. Resistance of tumour cells to BRAF inhibitors is reduced by the addition of an MEK inhibitor; both BRAF and MEK inhibitors have been reported to produce a variety of dermatological toxic effects. Benign naevi often harbour BRAF mutations but few reports exist that document the response of naevus cells to BRAF inhibition. We report sarcoidal-type granulomatous inflammation in two patients with metastatic melanoma undergoing treatment with combination BRAF and MEK inhibitor therapy. This inflammation manifested in one patient as a nonspecific papular eruption; in the other, in association with clinical regression of multiple benign-appearing naevi during the course of therapy. The significance of sarcoidal-type inflammation occurring during treatment of metastatic melanoma with a combination of BRAF and MEK inhibitors is unclear. Its association with the clinical regression of benign-appearing naevi suggests a possible exaggerated inflammatory response to degenerating naevus cells in these lesions.
...
PMID:Novel cutaneous effects of combination chemotherapy with BRAF and MEK inhibitors: a report of two cases. 2341 75

Metastatic melanoma is one of the most aggressive forms of cutaneous cancers. Although recent therapeutic advances have prolonged patient survival, the prognosis remains dismal. C-MER proto-oncogene tyrosine kinase (MERTK) is a receptor tyrosine kinase with oncogenic properties that is often overexpressed or activated in various malignancies. Using both protein immunohistochemistry and microarray analyses, we demonstrate that MERTK expression correlates with disease progression. MERTK expression was highest in metastatic melanomas, followed by primary melanomas, while the lowest expression was observed in nevi. Additionally, over half of melanoma cell lines overexpressed MERTK compared with normal human melanocytes; however, overexpression did not correlate with mutations in BRAF or RAS. Stimulation of melanoma cells with the MERTK ligand GAS6 resulted in the activation of several downstream signaling pathways including MAPK/ERK, PI3K/AKT, and JAK/STAT. MERTK inhibition via shRNA reduced MERTK-mediated downstream signaling, reduced colony formation by up to 59%, and diminished tumor volume by 60% in a human melanoma murine xenograft model. Treatment of melanoma cells with UNC1062, a novel MERTK-selective small-molecule tyrosine kinase inhibitor, reduced activation of MERTK-mediated downstream signaling, induced apoptosis in culture, reduced colony formation in soft agar, and inhibited invasion of melanoma cells. This work establishes MERTK as a therapeutic target in melanoma and provides a rationale for the continued development of MERTK-targeted therapies.
 ...
PMID:MERTK receptor tyrosine kinase is a therapeutic target in melanoma. 2358 77

Pigment cells and neuronal cells both are derived from the neural crest. Here, we describe the Pit-Oct-Unc (POU) domain transcription factor Brn3a, normally involved in neuronal development, to be frequently expressed in melanoma, but not in melanocytes and nevi. RNAi-mediated silencing of Brn3a strongly reduced the viability of melanoma cell lines and decreased tumour growth in vivo. In melanoma cell lines, inhibition of Brn3a caused DNA double-strand breaks as evidenced by Mre11/Rad50-containing nuclear foci. Activated DNA damage signalling caused stabilization of the tumour suppressor p53, which resulted in cell cycle arrest and apoptosis. When Brn3a was ectopically expressed in primary melanocytes and fibroblasts, anchorage-independent growth was increased. In tumourigenic melanocytes and fibroblasts, Brn3a accelerated tumour growth in vivo. Furthermore, Brn3a cooperated with proliferation pathways such as oncogenic BRAF, by reducing oncogene-induced senescence in non-malignant melanocytes. Together, these results identify Brn3a as a new factor in melanoma that is essential for melanoma cell survival and that promotes melanocytic transformation and tumourigenesis.
 ...
PMID:The neural crest transcription factor Brn3a is expressed in melanoma and required for cell cycle progression and survival. 2366 55

BRAF(V600E) mutations are frequent in melanomas originating from intermittently sun-exposed skin and also in common acquired melanocytic nevi, suggesting that BRAF mutation is an early event in melanocytic neoplasia. All neoplastic melanocytes within such a nevus would be expected to carry the BRAF mutation, and thus we evaluated the frequency of cells with BRAF(V600E) mutations within acquired nevi by droplet digital polymerase chain reaction. In BRAF-mutant nevi the number of BRAF mutant alleles equaled the number of wild-type (WT) alleles in the neoplastic cell population, consistent with a fully clonal heterozygous BRAF mutation. The allelic ratio of BRAF(V600E) to BRAF(WT) in the eight VE1-positive nevi, adjusted for degree of stromal contamination, ranged from 0.84 to 1.12 with an average ratio of 1.01. This was confirmed by immunohistochemistry with an antibody specific for BRAF(V600E), which uniformly labeled the neoplastic cells without any evidence of heterogeneity. We found BRAF(V600E) mutations in the melanocytic nevi to be fully clonal, strongly suggesting that BRAF-activating mutations typically are early initiating events in melanocytic neoplasia.
 ...
PMID:Clonal BRAF mutations in melanocytic nevi and initiating role of BRAF in melanocytic neoplasia. 2369 May 27

BRAF mutation has been linked to the development of melanocytic tumors in homogeneous Caucasian cohorts. The role of solar UV radiation (UVR) in BRAF mutation status is poorly understood. We studied the epidemiology of BRAF mutation across a spectrum of melanocytic neoplasms in populations with differing UVR rates. Extended testing for 9 mutation types was attempted on 600 melanocytic neoplasms including banal nevi (n = 225), dysplastic nevi (n = 113), primary (n = 172), and metastatic melanomas (n = 90). Specimens were collected from 4 countries with increasing UVR rates (in kJ/m/yr): Syria (n = 45; UVR = 93.5), Lebanon (n = 225; UVR = 110), Pakistan (n = 122; UVR = 128), and Saudi Arabia (n = 208; UVR = 139). UVR was estimated from 21-year averages from The National Center for Atmospheric Research database. The overall BRAF mutation rate was 49% (268 of 545) and differed significantly by the geographic location [34% Pakistan, 49% Lebanon, 67% Syria, and 54% Saudi Arabia; P = 0.001], neoplasm type (P < 0.001), and anatomical location (P < 0.001) but not with age (P = 0.07) and gender (P = 1.0). V600E was the predominant mutation type, found in 96.3% of the cases. Incidence of melanoma was significantly greater in BRAF-negative (39%) versus BRAF-positive (17%) groups. For BRAF-positive cases, less severe lesions were systematically more frequent (P < 0.001). Multivariate analysis indicated that BRAF mutation is predicted by neoplasm type, anatomical site, and geographic location. In our Near East cohort, BRAF mutation rates varied by geographic location but not based on UVR. BRAF-positive status was associated with less severe lesions.
 ...
PMID:BRAF analysis on a spectrum of melanocytic neoplasms: an epidemiological study across differing UV regions. 2378 79

Approximately 10% of melanoma cases are familial, but only 25-40% of familial melanoma cases can be attributed to germ-line mutations in the CDKN2A - the most significant high-risk melanoma susceptibility locus identified to date. The pathogenic mutation(s) in most of the remaining familial melanoma pedigrees have not yet been identified. The most common mutations in nevi and sporadic melanoma are found in BRAF and NRAS, both of which result in constitutive activation of the MAPK pathway. However, these mutations are not found in uveal melanomas or the intradermal melanocytic proliferations known as blue nevi. Rather, multiple studies report a strong association between these lesions and somatic mutations in Guanine nucleotide-binding protein G(q) subunit alpha (GNAQ), Guanine nucleotide-binding protein G(q) subunit alpha-11 (GNA11), and BRCA1-associated protein-1 (BAP1). Recently, germ-line mutations in BAP1, the gene encoding a tumor suppressing deubiquitinating enzyme, have been associated with predisposition to a variety of cancers including uveal melanoma, but no studies have examined the association of germ-line mutations in GNAQ and GNA11 with uveal melanoma and blue nevi. We have now done so by sequencing exon 5 of both of these genes in 13 unique familial melanoma pedigrees, members of which have had either uveal or cutaneous melanoma and/or blue nevi. Germ-line DNA from a total of 22 individuals was used for sequencing; however no deleterious mutations were detected. Nevertheless, such candidate gene studies and the discovery of novel germ-line mutations associated with an increased MM susceptibility can lead to a better understanding of the pathways involved in melanocyte transformation, formulation of risk assessment, and the development of specific drug therapies.
...
PMID:Lack of GNAQ and GNA11 Germ-Line Mutations in Familial Melanoma Pedigrees with Uveal Melanoma or Blue Nevi. 2382 98

According to the prevailing multistep model of melanoma development, oncogenic BRAF or NRAS mutations are crucial initial events in melanoma development. It is not known whether melanocytic nevi that are found in association with a melanoma are more likely to carry BRAF or NRAS mutations than uninvolved nevi. By laser microdissection we were able to selectively dissect and genotype cells either from the nevus or from the melanoma part of 46 melanomas that developed in association with a nevus. In 25 cases we also genotyped a control nevus of the same patients. Available tissue was also immunostained using the BRAF(V600E)-mutation specific antibody VE1. The BRAF(V600E) mutation was found in 63.0% of melanomas, 65.2% of associated nevi and 50.0% of control nevi. No significant differences in the distribution of BRAF or NRAS mutations could be found between melanoma and associated nevi or between melanoma associated nevi and control nevi. In concordant cases immunohistochemistry showed a higher expression (intensity of immunohistochemistry) of the mutated BRAF(V600E)-protein in melanomas compared to their associated nevi. In this series the presence of a BRAF- or NRAS mutation in a nevus was not associated with the risk of malignant transformation. Our findings do not support the current traditional model of stepwise tumor progression.
...
PMID:NRAS and BRAF mutations in melanoma-associated nevi and uninvolved nevi. 2386 77


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>