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)

Uveal melanoma is the most common primary intraocular malignancy, with an annual incidence of 6 per million. The environmental factors known to increase the risk of cutaneous melanoma appear to be less important in ocular melanoma and it is conceivable that host factors have a greater impact. The coexistence of ocular and cutaneous melanoma in some patients suggests a predisposition to both types and implicates mutations in the CDKN2A gene in a proportion of these cases. An association between ocular melanoma and breast and/or ovarian cancer has also been reported and recent studies of breast cancer families strongly implicate BRCA2 as a predisposition gene. Other more common genes predisposing to ocular melanoma may be of low penetrance. An example of a gene in this class is MC1R, which affects host response to ultraviolet radiation. Identification of genes conferring an increased risk of ocular melanoma should provide insights into the pathogenesis of this tumour. Furthermore, it offers an opportunity to identify individuals at a high risk who may benefit from targeted surveillance. At present the identification of such individuals is restricted to the small number belonging to BRCA2 families and those with the atypical mole syndrome.
 ...
PMID:Genetic predisposition to ocular melanoma. 1069 48

The alpha-melanocyte-stimulating hormone (alphaMSH) receptor (MC1R) is a major determinant of mammalian skin and hair pigmentation. Binding of alphaMSH to MC1R in human melanocytes stimulates cell proliferation and synthesis of photoprotective eumelanin pigments. Certain MC1R alleles have been associated with increased risk of melanoma. This can be theoretically considered on two grounds. First, gain-of-function mutations may stimulate proliferation, thus promoting dysplastic lesions. Second, and opposite, loss-of-function mutations may decrease eumelanin contents, and impair protection against the carcinogenic effects of UV light, thus predisposing to skin cancers. To test these possibilities, we sequenced the MC1R gene from seven human melanoma cell (HMC) lines and three giant congenital nevus cell (GCNC) cultures. Four HMC lines and two GCNC cultures contained MC1R allelic variants. These were the known loss-of-function Arg142His and Arg151Cys alleles and a new variant, Leu93Arg. Moreover, impaired response to a superpotent alphaMSH analog was demonstrated for the cell line carrying the Leu93Arg allele and for a HMC line homozygous for wild-type MC1R. Functional analysis in heterologous cells stably or transiently expressing this variant demonstrated that Leu93Arg is a loss-of-function mutation abolishing agonist binding. These results, together with site-directed mutagenesis of the vicinal Glu94, demonstrate that the MC1R second transmembrane fragment is critical for agonist binding and maintenance of a resting conformation, whereas the second intracellular loop is essential for coupling to the cAMP system. Therefore, loss-of-function, but not activating MC1R mutations are common in HMC. Their study provides important clues to understand MC1R structure-function relationships.
 ...
PMID:Loss-of-function variants of the human melanocortin-1 receptor gene in melanoma cells define structural determinants of receptor function. 1247 9

We have examined MC1R variant allele frequencies in the general population of South East Queensland and in a collection of adolescent dizygotic and monozygotic twins and family members to define statistical associations with hair and skin color, freckling, and mole count. Results of these studies are consistent with a linear recessive allelic model with multiplicative penetrance in the inheritance of red hair. Four alleles, D84E, R151C, R160W, and D294H, are strongly associated with red hair and fair skin with multinomial regression analysis showing odds ratios of 63, 118, 50, and 94, respectively. An additional three low-penetrance alleles V60L, V92M, and R163Q have odds ratios 6, 5, and 2 relative to the wild-type allele. To address the cellular effects of MC1R variant alleles in signal transduction, we expressed these receptors in permanently transfected HEK293 cells. Measurement of receptor activity via induction of a cAMP-responsive luciferase reporter gene found that the R151C and R160W receptors were active in the presence of NDP-MSH ligand, but at much reduced levels compared with that seen with the wild-type receptor. The ability to stimulate phosphorylation of the cAMP response element binding protein (CREB) transcription factor was also apparent in all stimulated MC1R variant allele-expressing HEK293 cell extracts as assessed by immunoblotting. In contrast, human melanoma cell lines showed wide variation in the their ability to undergo cAMP-mediated CREB phosphorylation. Culture of human melanocytes of known MC1R genotype may provide the best experimental approach to examine the functional consequences for each MC1R variant allele. With this objective, we have established more than 300 melanocyte cell strains of defined MC1R genotype.
 ...
PMID:Genetic association and cellular function of MC1R variant alleles in human pigmentation. 1285 35

The relationships between MC1R gene variants and red hair, skin reflectance, degree of freckling and nevus count were investigated in 2331 adolescent twins, their sibs and parents in 645 twin families. Penetrance of each MC1R variant allele was consistent with an allelic model where effects were multiplicative for red hair but additive for skin reflectance. Of nine MC1R variant alleles assayed, four common alleles were strongly associated with red hair and fair skin (Asp84Glu, Arg151Cys, Arg160Trp and Asp294His), with a further three alleles having low penetrance (Val60Leu, Val92Met and Arg163Gln). These variants were separately combined for the purposes of this analysis and designated as strong 'R' (OR=63.3; 95% CI 31.9-139.6) and weak 'r ' (OR=5.1; 95% CI 2.5-11.3) red hair alleles. Red-haired individuals are predominantly seen in the R/R and R/r groups with 67.1 and 10.8%, respectively. To assess the interaction of the brown eye color gene OCA2 on the phenotypic effects of variant MC1R alleles we included eye color as a covariate, and also genotyped two OCA2 SNPs (Arg305Trp and Arg419Gln), which were confirmed as modifying eye color. MC1R genotype effects on constitutive skin color, freckling and mole count were modified by eye color, but not genotype for these two OCA2 SNPs. This is probably due to the association of these OCA2 SNPs with brown/green not blue eye color. Amongst individuals with a R/R genotype (but not R/r), those who also had brown eyes had a mole count twice that of those with blue eyes. This suggests that other OCA2 polymorphisms influence mole count and remain to be described.
 ...
PMID:Interactive effects of MC1R and OCA2 on melanoma risk phenotypes. 1470 92

Major risk factors for melanoma include many nevi, especially dysplastic nevi, fair pigmentation, freckling, poor tanning ability, and germ line mutations in the CDKN2A, CDK4, or MC1R genes. We evaluated the relationship between MC1R and melanoma risk in CDKN2A melanoma-prone families with extensive clinical and epidemiologic data. We studied 395 subjects from 16 American CDKN2A families. Major melanoma risk factors were assessed by clinical examination or questionnaire; MC1R was sequenced. Odds ratios were estimated by unconditional and conditional logistic regression models. We examined the distribution of MC1R variants and median ages at melanoma diagnosis in multiple primary melanoma (MPM) and single primary melanoma (SPM) patients. Presence of multiple MC1R variants was significantly associated with melanoma, even after adjustment for major melanoma risk factors. All 40 MPM patients had at least one MC1R variant; 65% of MPM patients versus only 17% of SPM patients had at least two MC1R variants (P < 0.0001). For all 69 melanoma patients combined, as well as the 40 MPM patients, there was a statistically significant decrease in median age at diagnosis as numbers of MC1R variants increased (P = 0.010 and P = 0.008, respectively). In contrast, no significant reduction in age at melanoma diagnosis was observed for SPM patients (P = 0.91). The current study suggests that the presence of multiple MC1R variants is associated with the development of multiple melanoma tumors in patients with CDKN2A mutations. Additional studies are needed to confirm these findings and to explore the mechanisms that may contribute to this relationship.
 ...
PMID:Association of MC1R variants and risk of melanoma in melanoma-prone families with CDKN2A mutations. 1628 65

Germline mutations in CDKN2A gene predispose to melanoma with high but incomplete penetrance. Penetrance of CDKN2A gene was found to be significantly influenced by host factors (nevus phenotypes and sunburn) on one hand and by variants of MC1R gene (RHC variants consistently associated with red hair and fair skin) on the other hand. Our goal was to examine the joint effects of MC1R variants and other potential risk factors [total nevi, dysplastic nevi, pigmentary traits (skin, hair and eye color), skin reactions to sunlight, and degree of sun exposure] on CDKN2A penetrance. Clinical, genetic, and covariate data were recorded in 20 French melanoma-prone families with cosegregating CDKN2A mutations. Analysis of the cotransmission of melanoma and CDKN2A mutations was conducted by likelihood-based methods using the regressive logistic models, which can account for a variation of disease risk with age and can include the aforementioned risk factors as covariates. RHC variants, considered either alone or in the presence of pigmentation and nevus phenotypes, were found to increase significantly CDKN2A penetrance. Multivariate analysis, using a stepwise selection procedure, showed significant effects of two factors on melanoma risk in CDKN2A mutations carriers: RHC variants [odds ratio of hazard function (OR), 2.21; P = 0.03] and dysplastic nevi (OR, 2.93; P < 0.01). Such results may have important consequences to improve the prediction of melanoma risk in families.
 ...
PMID:Melanocortin-1 receptor (MC1R) gene variants and dysplastic nevi modify penetrance of CDKN2A mutations in French melanoma-prone pedigrees. 1621 21

The G101W founder mutation is the most common CDKN2A mutation in Italy, Spain, and France. As the background of modifying genes, environmental exposures, and sun behavior vary across countries, studying G101W carriers from distinct countries offers a unique opportunity to evaluate possible modifying factors in melanoma development. We evaluated 76 G101W cases and 59 carrier controls from France, Italy, Spain, and the United States. Hair color and dysplastic nevi distributions differed significantly in cases and controls across the 4 study groups. Cases also varied significantly for eye color, freckling, and nevi. The distribution of MC1R variants in cases differed significantly across study groups because 12% of Italian melanoma patients had > or =2 MC1R variants vs. >50% for the other case groups. Several MC1R covariates showed significant associations with melanoma risk in all groups combined and in the American, French, and Spanish samples; no significant findings were observed in the Italian sample. In multiple-case families, the number and type of MC1R variants varied significantly between multiple-primary-melanoma and single-primary-melanoma patients from the 4 groups; there was also a significant decrease in median age at melanoma diagnosis as the number or type of MC1R variants increased. The variation in the effects of the cutaneous phenotypic and MC1R factors across the study sample suggests that these factors differentially contribute to development of melanoma even on a common genetic background of a germline CDKN2A mutation. Differences in melanoma risk across geographic regions justify the need for individual studies in each country before counseling should be considered.
 ...
PMID:Cutaneous phenotype and MC1R variants as modifying factors for the development of melanoma in CDKN2A G101W mutation carriers from 4 countries. 1739 31

A significantly increased susceptibility to melanoma may manifest as a family history of melanoma (plus or minus pancreatic cancer), the development of multiple primary tumors, or melanoma in the context of numerous and clinically atypical moles (the atypical mole syndrome). In families, increased susceptibility may occur as a result of the inheritance of mutations at the CDKN2A locus or in the CDK4 gene. We describe what is known about these genes and discuss the implications for genetic counseling and gene testing. Lower levels of risk are associated with genetically determined pigmentary variation within populations. This variation is attributable to inheritance of variants in the MC1R gene and putatively other genes such as OCA2, which is discussed. Melanoma is causally related to sun exposure in the majority of patients, although the patterns of sun exposure, which are most important, remain controversial. The role of risk estimation for individuals in giving advice about sun exposure is considered.
 ...
PMID:Genetics: what advice for patients who present with a family history of melanoma? 1808 68

Oculocutaneous albinism type 2 (OCA2) is a human autosomal-recessive hypopigmentation disorder associated with pathological mutations of the OCA2 gene. In this study, we investigated a form of OCA in a Polynesian population with an observed phenotype characterized by fair skin, some brown nevi present in the sun-exposed areas and green or blue eyes. Hair presented with a unique red coloration since birth, with tones ranging across individuals from Yellow-Red to Brown-Red, or Auburn. We genetically screened for mutations in the OCA2 and MC1R genes as their products have previously been shown to be associated with red hair/fair skin and OCA2. The SLC45A2 gene was also screened to identify any possible relation to skin color variation. We have identified a novel missense substitution in the OCA2 gene (Gly775Asp) responsible for OCA2 in individuals of Polynesian heritage from Tuvalu. The estimated incidence of this form of OCA2 in the primary study community is believed to occur at one of the highest recorded rates of albinism at approximately 1 per 669 individuals. In addition, we have analyzed four unrelated individuals with albinism who have Polynesian heritage from three other separate communities and found they carry the same OCA2 mutation. We also analyzed an out-group comprising three unrelated individuals with albinism of Melanesian ancestries from two separate communities, one Australian Aboriginal and three Australian Caucasians, and did not detect this mutation. We hypothesize that this mutation may be Polynesian specific and that it originated from a common founder.
 ...
PMID:Inheritance of a novel mutated allele of the OCA2 gene associated with high incidence of oculocutaneous albinism in a Polynesian community. 2001 52

Malignant melanoma, a potentially lethal skin neoplasm, is characterized by a complex and heterogeneous etiology. Both incidences and deaths associated with melanoma are increasing in Caucasian populations. While exposure to ultraviolet radiation through sun-exposure is the major risk factor; the host factors including skin type and number of moles are critical in predisposition. The CDKN2A is a high penetrance melanoma susceptibility gene as carriers of the mutations are predisposed to the disease within familial settings. The gene is also somatically altered to varying degrees in sporadic melanoma. The CDK4 gene due to occurrence of activation mutations in a few families worldwide represents another melanoma susceptibility locus. The variants within the melanocortin receptor 1 (MC1R) gene, which encodes a melanocyte specific surface receptor with a key role in pigmentation, are associated with high risk phenotypes and increased risk of melanoma. Melanoma tumors are characterized by activation of the RAS-RAF-MEK-ERK pathway through either autocrine growth factor stimulation or oncogenic mutations in the B-RAF or N-RAS genes. Somatic mutations in the B-RAF gene are complemented by those in the N-RAS gene and represent the major genetic alterations. The mutations in the B-RAF gene in melanoma due to occurrence in melanocytic nevi represent early events that additionally require loss of cell cycle inhibitors like CDKN2A for melanoma progression and development. The sequence of events points to the cooperative collaboration between different genetic pathways in tumor development that can be and are being used as targets for developing specific therapeutic agents.
 ...
PMID:Malignant melanoma--a genetic overview. 2009 96


1 2 3 Next >>