MC1R variants, melanoma and red hair color phenotype: A meta-analysis

Next-generation sequencing of multiple individuals per barcoded library by deconvolution of sequenced amplicons using endonuclease fragment analysis

The simultaneous sequencing of samples from multiple individuals increases the efficiency of next-generation sequencing (NGS) while also reducing costs. Here we describe a novel and simple approach for sequencing DNA from multiple individuals per barcode. Our strategy relies on the endonuclease digestion of PCR amplicons prior to library preparation, creating a specific fragment pattern for each individual that can be resolved after sequencing. By using both barcodes and restriction fragment patterns, we demonstrate the ability to sequence the human melanocortin 1 receptor (MC1R) genes from 72 individuals using only 24 barcoded libraries.

Epidemiology, risk factors, prevention, and early detection of melanoma

The incidence of melanoma has increased over the past several decades. Despite improved case mortality, overall deaths from melanoma have increased because of the large increase in incidence. Although we have a better understanding of the pathogenesis of melanoma and improved early diagnostic capabilities, the burden of disease and societal costs remain high. This article provides an update on the epidemiology of cutaneous melanoma worldwide and the common risk factors including heritable and modifiable risks, emphasizing the importance of education, early detection, and prevention in reducing the disease burden.

Is MC1 dispensable for regulation of cutaneous inflammatory and immune responses?

The melanocortin-1 receptor (MC1 ) - being most abundantly expressed in the skin by melanocytes - has a physiological role for melanin pigmentation in many vertebrate species. MC1 has also been implicated in regulation of skin inflammation as this receptor is detectable in the majority of non-melanocytic cell types and its ligand α-melanocyte-stimulating hormone (α-MSH) exerts immunoregulatory and anti-inflammatory effects. However, in vivo studies on mice with targeted disruption of MC1 have been missing in the context of skin inflammation until recently. Wolnicka-Glubisz et al. now reported that the course of ultraviolet (UV)-induced inflammation, contact hypersensitivity, neonatal immune tolerance and UV-induced immunosuppression is similar in MC1 signal-deficient (C57BL/6-Mc1r(e/e)) and wild-type mice. These unexpected findings are supported by own observations in experimentally induced immune-complex-mediated vasculitis: Mc1r(e/e) mice exhibited a similar extent of the reverse passive cutaneous Arthus reaction compared with wild-type animals. Future studies are thus needed to clarify whether these findings are due to limitations in the chosen mouse model and/or point to additional MC subtypes that may regulate inflammatory and immune responses in the skin.

Development of a melanoma risk prediction model incorporating MC1R genotype and indoor tanning exposure: impact of mole phenotype on model performance

Background

Identifying individuals at increased risk for melanoma could potentially improve public health through targeted surveillance and early detection. Studies have separately demonstrated significant associations between melanoma risk, melanocortin receptor (MC1R) polymorphisms, and indoor ultraviolet light (UV) exposure. Existing melanoma risk prediction models do not include these factors; therefore, we investigated their potential to improve the performance of a risk model.

Methods

Using 875 melanoma cases and 765 controls from the population-based Minnesota Skin Health Study we compared the predictive ability of a clinical melanoma risk model (Model A) to an enhanced model (Model F) using receiver operating characteristic (ROC) curves. Model A used self-reported conventional risk factors including mole phenotype categorized as “none”, “few”, “some” or “many” moles. Model F added MC1R genotype and measures of indoor and outdoor UV exposure to Model A. We also assessed the predictive ability of these models in subgroups stratified by mole phenotype (e.g. nevus-resistant (“none” and “few” moles) and nevus-prone (“some” and “many” moles)).

Results

Model A (the reference model) yielded an area under the ROC curve (AUC) of 0.72 (95% CI = 0.69, 0.74). Model F was improved with an AUC = 0.74 (95% CI = 0.71–0.76, p<0.01). We also observed substantial variations in the AUCs of Models A & F when examined in the nevus-prone and nevus-resistant subgroups.

Conclusions

These results demonstrate that adding genotypic information and environmental exposure data can increase the predictive ability of a clinical melanoma risk model, especially among nevus-prone individuals.

Having children, social characteristics, smoking and the risk of uveal melanoma: a case-control study

PURPOSE

We analyzed data from the Risk Factors for Uveal Melanoma (RIFA) study to evaluate possible associations between uveal melanoma risk and having children, socioeconomic level and smoking.

METHODS

The RIFA study was a German case-control study conducted from September 2002 to March 2005. The study population consisted of 455 incident uveal melanoma patients (20-74 years of age) and 827 matched (age, sex, region of residence) population controls. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using conditional logistic regression.

RESULTS

Women with children showed an increased OR (1.59, 95% CI 0.95-2.66) for uveal melanoma development compared to women without children. We estimated decreased ORs for subjects with higher socioeconomic level compared to the lowest status (upper secondary school leaving certificate: OR 0.68, 95% CI 0.49-0.94; higher education: OR 0.60, 95% CI 0.38-0.96). Ever smokers showed an OR of 1.19 (95% CI 0.92-1.55) compared to never smokers.

CONCLUSION

The observed association between lower socioeconomic level and increased odds for uveal melanoma possibly represents a higher occupational uveal melanoma risk for occupational categories that are usually associated with lower socioeconomic status. Concerning having children and uveal melanoma development, we hypothesize that the observed association is mediated through alpha-melanocyte-stimulating hormone, a hormone that increases during pregnancy and is linked to pigmentation alterations in pregnant women.

Involvement of ANXA5 and ILKAP in susceptibility to malignant melanoma

Single nucleotide-polymorphisms (SNPs) are a source of diversity among human population, which may be responsible for the different individual susceptibility to diseases and/or response to drugs, among other phenotypic traits. Several low penetrance susceptibility genes associated with malignant melanoma (MM) have been described, including genes related to pigmentation, DNA damage repair and oxidative stress pathways. In the present work, we conducted a candidate gene association study based on proteins and genes whose expression we had detected altered in melanoma cell lines as compared to normal melanocytes. The result was the selection of 88 loci and 384 SNPs, of which 314 fulfilled our quality criteria for a case-control association study. The SNP rs6854854 in ANXA5 was statistically significant after conservative Bonferroni correction when 464 melanoma patients and 400 controls were analyzed in a discovery Phase I. However, this finding could not be replicated in the validation phase, perhaps because the minor allele frequency of SNP rs6854854 varies depending on the geographical region considered. Additionally, a second SNP (rs6431588) located on ILKAP was found to be associated with melanoma after considering a combined set of 1,883 MM cases and 1,358 disease-free controls. The OR was 1.29 (95% CI 1.12–1.48; p-value = 4×10⁻⁴). Both SNPs, rs6854854 in ANXA5 and rs6431588 in ILKAP, show population structure, which, assuming that the Spanish population is not significantly structured, suggests a role of these loci on a specific genetic adaptation to different environmental conditions. Furthermore, the biological relevance of these genes in MM is supported by in vitro experiments, which show a decrease in the transcription levels of ANXA5 and ILKAP in melanoma cells compared to normal melanocytes.

A large French case-control study emphasizes the role of rare Mc1R variants in melanoma risk

BACKGROUND

The MC1R gene implicated in melanogenesis and skin pigmentation is highly polymorphic. Several alleles are associated with red hair and fair skin phenotypes and contribute to melanoma risk.

OBJECTIVE

This work aims to assess the effect of different classes of MC1R variants, notably rare variants, on melanoma risk. Methods. MC1R coding region was sequenced in 1131 melanoma patients and 869 healthy controls. MC1R variants were classified as RHC (R) and non-RHC (r). Rare variants (frequency < 1%) were subdivided into two subgroups, predicted to be damaging (D) or not (nD).

RESULTS

Both R and r alleles were associated with melanoma (OR = 2.66 [2.20-3.23] and 1.51 [1.32-1.73]) and had similar population attributable risks (15.8% and 16.6%). We also identified 69 rare variants, of which 25 were novel. D variants were strongly associated with melanoma (OR = 2.38 [1.38-4.15]) and clustered in the same MC1R domains as R alleles (intracellular 2, transmembrane 2 and 7).

CONCLUSION

This work confirms the role of R and r alleles in melanoma risk in the French population and proposes a novel class of rare D variants as important melanoma risk factors. These findings may improve the definition of high-risk subjects that could be targeted for melanoma prevention and screening.

Genetic alterations and personalized medicine in melanoma: progress and future prospects

High-throughput sequencing technologies are providing new insights into the genetic alterations involved in melanomagenesis. It appears likely that most genetic events important in the pathogenesis of melanoma will be discovered over the next few years. Genetic analysis is also increasingly being used to direct patient care. In parallel with the discovery of new genes and the elucidation of molecular pathways important in the development of melanoma, therapies targeting these pathways are becoming available. In other words, the age of personalized medicine has arrived, characterized by molecular profiling of melanoma to identify the relevant genetic alterations and the abnormal signaling mechanisms involved, followed by selection of optimal, individualized therapies. In this review, we summarize the key genetic alterations in melanoma and the development of targeted agents against melanomas bearing specific mutations. These developments in melanoma serve as a model for the implementation of personalized medicine for patients with all cancers.

Actinic damage on the back is significantly determined by MC1R variants and previous sun exposure compared with other body sites in a multivariate analysis

BACKGROUND

Only recently, site-dependent associations of actinic damage with melanoma were identified in our study population.

OBJECTIVES

To elucidate the diverse aetiologies for actinic damage at different body sites.

METHODS

We performed multivariate logistic regression analyses to identify independent risk factors for actinic damage on the face, hands and the back in 2112 participants of central European origin.

RESULTS

For actinic damage on the face, age was the only risk factor that remained consistently significant in a multivariate analysis, whereas actinic damage on the back was predominantly associated with number of sunburns, freckles in childhood, holiday weeks and male sex. Moreover, we identified a particular significance of MC1R variants and dorsal actinic skin damage.

CONCLUSIONS

The particular effect of MC1R variants and sun exposure during recreational time on dorsal actinic damage indicates that actinic damage on the back is more informative regarding susceptibility to sunlight and past sun exposure associated with melanoma risk.

Dermoscopic features of cutaneous melanoma are associated with clinical characteristics of patients and tumours and with MC1R genotype

BACKGROUND

Several algorithms are available for the dermoscopic diagnosis of pigmented skin lesions. The MC1R gene is a key determinant of pigmentation characteristics that are established host-related melanoma risk factors.

OBJECTIVES

To investigate the association of dermoscopic features of sporadic cutaneous melanomas with clinical characteristics of patients and corresponding tumours and with genetic changes in the MC1R and BRAF genes.

METHODS

A total of 64 dermoscopic images of 62 patients were scored by ABCD rule and modified pattern analysis. Detailed patients' and melanomas' characteristics were collected. Patients were screened for germline MC1R variants and related melanomas for somatic V600 BRAF mutations.

RESULTS

A lower total dermoscopic score (TDS) was observed in melanomas of patients with red hair (P = 0.019), due to reduced dermoscopic structures (P < 0.0001). Thicker melanomas showed higher TDS values (P = 0.021) due to sharper borders (P < 0.0001) and higher number of colors (P = 0.004). An atypical pigment network was prevalent in superficial spreading melanomas (P = 0.010), in individuals with dark skin (P = 0.043) and hair color (P = 0.001). An atypical vascular pattern was more frequent in nodular (P < 0.0001) and thick (P < 0.0001) melanomas, in individuals with skin type I-II (P = 0.037), blond or red hair color (P = 0.032) and blue or green eyes (P = 0.014). Melanomas of MC1R R carriers showed lower TDS value (P = 0.037), reduced dermoscopic structures (P = 0.001) and lower prevalence of atypical pigment network (P = 0.001). No differences were identified between BRAF-mutated or wild-type melanomas.

CONCLUSIONS

We suggest a phenotypic/MC1R profile for melanoma patients and their tumours. Melanomas of MC1R R carriers show a significant lower TDS value, with reduced dermoscopic structures, and a lower prevalence of an atypical pigment network. Non-carriers of MC1R R variants develop melanomas dermoscopically characterized by an atypical pigment network which is prevalent in superficial spreading melanomas, in patients with dark complexion and less frequent in red-haired individuals.

Cutaneous melanoma

In the past decade, major advances have been made in the understanding of melanoma. New predisposition genes have been reported and key somatic events, such as BRAF mutation, directly translated into therapeutic management. Surgery for localised melanoma and regional lymph node metastases is the standard of care. Sentinel-node biopsy provides precise staging, but has not been reported to affect survival. The effect of lymph-node dissection on survival is a topic of investigation. Two distinct approaches have emerged to try to extend survival in patients with metastatic melanoma: immunomodulation with anti-CTLA4 monoclonal antibodies, and targeted therapy with BRAF inhibitors or MEK inhibitors for BRAF-mutated melanoma. The combination of BRAF inhibitors and MEK inhibitors might improve progression-free survival further and, possibly, increase overall survival. Response patterns differ substantially-anti-CTLA4 immunotherapy can induce long-term responses, but only in a few patients, whereas targeted drugs induce responses in most patients, but nearly all of them relapse because of pre-existing or acquired resistance. Thus, the long-term prognosis of metastatic melanoma remains poor. Anti-PD1 and anti-PDL1 antibodies have emerged as breakthrough drugs for melanoma that have high response rates and long durability. Biomarkers that have predictive value remain elusive in melanoma, although emerging data for adjuvant therapy indicate that interferon sensitivity is associated with ulceration of the primary melanoma. Intense investigation continues for clinical and biological markers that predict clinical benefit of immunotherapeutic drugs, such as interferon alfa or anti-CTLA4 antibodies, and the mechanisms that lead to resistance of targeted drugs.

Genetics and genomics of melanoma

The rapidly increasing incidence of melanoma, coupled with its highly aggressive metastatic nature, is of urgent concern. In order to design rational therapies, it is of critical importance to identify the genetic determinants that drive melanoma formation and progression. To date, signaling cascades emanating from the EGF receptor, c-MET and other receptors are known to be altered in melanoma. Important mutations in signaling molecules, such as BRAF and N-RAS, have been identified. In this review, some of the major genetic alterations and signaling pathways involved in melanoma will be discussed. Given the great deal of genetic heterogeneity observed in melanoma, it is likely that many more genetic determinants exist. Through the use of powerful genomic technologies, it is now possible to identify these additional genetic alterations in melanoma. A critical step in this analysis will be culling bystanders from functionally important drivers, as this will highlight genetic elements that will be promising therapeutic targets. Such technologies and the important points to consider in understanding the genetics of melanoma will be reviewed.

Melanoma susceptibility genes and risk assessment

Familial melanoma accounts for approximately a tenth of all melanoma cases. The most commonly known melanoma susceptibility gene is the highly penetrant CDKN2A (p16INK4a) locus, which is transmitted in an autosomal dominant fashion and accounts for approximately 20-50 % of familial melanoma cases. Mutated p16INK4a shows impaired capacity to inhibit the cyclin D1-CDK4 complex, allowing for unchecked cell cycle progression. Mutations in the second protein coded by CDKN2A, p14ARF, are much less common and result in proteasomal degradation of p53 with subsequent accumulation of DNA damage as the cell progresses through the cell cycle without a functional p53-mediated DNA damage response. Mutations in CDK4 that impair the inhibitory interaction with p16INK4a also increase melanoma risk but these mutations are extremely rare. Genes of the melanin biosynthetic pathway, including MC1R and MITF, have also been implicated in melanomagenesis. MC1R variants were traditionally thought to increase risk for melanoma secondary to intensified UV-mediated DNA damage in the setting of absent photoprotective eumelanin. Accumulation of pheomelanin, which appears to have a carcinogenic effect regardless of UV exposure, may be a more likely mechanism. Impaired SUMOylation of the E318K variant of MITF results in increased transcription of genes that confer melanocytes with a pro-malignant phenotype. Mutations in the tumor suppressor BAP1 enhance the metastatic potential of uveal melanoma and predispose to cutaneous/ocular melanoma, atypical melanocytic tumors, and other internal malignancies (COMMON syndrome). Genome-wide association studies have identified numerous low-risk alleles. Although several melanoma susceptibility genes have been identified, risk assessment tools have been developed only for the most common gene implicated with hereditary melanoma, CDKN2A. MelaPRO, a validated model that relies on Mendelian inheritance and Bayesian probability theories, estimates carrier probability for CDKN2A and future risk of melanoma taking into account a patient's family and past medical history of melanoma. Genetic testing for CDKN2A mutations is currently available but the Melanoma Genetics Consortium recommends offering such testing to patients only in the context of research protocols because clinical utility is uncertain.

Joint effect of multiple common SNPs predicts melanoma susceptibility

Single genetic variants discovered so far have been only weakly associated with melanoma. This study aims to use multiple single nucleotide polymorphisms (SNPs) jointly to obtain a larger genetic effect and to improve the predictive value of a conventional phenotypic model. We analyzed 11 SNPs that were associated with melanoma risk in previous studies and were genotyped in MD Anderson Cancer Center (MDACC) and Harvard Medical School investigations. Participants with ≥15 risk alleles were 5-fold more likely to have melanoma compared to those carrying ≤6. Compared to a model using the most significant single variant rs12913832, the increase in predictive value for the model using a polygenic risk score (PRS) comprised of 11 SNPs was 0.07(95% CI, 0.05-0.07). The overall predictive value of the PRS together with conventional phenotypic factors in the MDACC population was 0.69 (95% CI, 0.64-0.69). PRS significantly improved the risk prediction and reclassification in melanoma as compared with the conventional model. Our study suggests that a polygenic profile can improve the predictive value of an individual gene polymorphism and may be able to significantly improve the predictive value beyond conventional phenotypic melanoma risk factors.

MC1R is a potent regulator of PTEN after UV exposure in melanocytes

The individuals carrying melanocortin-1 receptor (MC1R) variants, especially those associated with red hair color, fair skin, and poor tanning ability (RHC trait), are more prone to melanoma; however, the underlying mechanism is poorly defined. Here, we report that UVB exposure triggers phosphatase and tensin homolog (PTEN) interaction with wild-type (WT), but not RHC-associated MC1R variants, which protects PTEN from WWP2-mediated degradation, leading to AKT inactivation. Strikingly, the biological consequences of the failure of MC1R variants to suppress PI3K/AKT signaling are highly context dependent. In primary melanocytes, hyperactivation of PI3K/AKT signaling leads to premature senescence; in the presence of BRAF(V600E), MC1R deficiency-induced elevated PI3K/AKT signaling drives oncogenic transformation. These studies establish the MC1R-PTEN axis as a central regulator for melanocytes' response to UVB exposure and reveal the molecular basis underlying the association between MC1R variants and melanomagenesis.

MC1R gene variants and sporadic malignant melanoma susceptibility in the Canary Islands population

Several MC1R variants are associated with increased risk of malignant melanoma (MM) in a variety of populations. We aim to examine the influence of the MC1R variants (RHC: D84E, R151C, R160W; NRHC: V60L, R163Q and the synonymous polymorphism T314T) on the MM risk in a population from the Canary Islands. Overall, 1,046 Caucasian individuals were included in the study. A thousand of them were genotyped for MC1R variants: 509 were sporadic MM patients and 491 were healthy control subjects from general population. The analysis was adjusted for age, sex, hair colour, eye colour, skin phototype and ancestry. We found that carriers of the R151C and R163Q variants were at an increased risk for melanoma OR 2.76 (1.59-4.78) and OR 5.62 (2.54-12.42), respectively. The risk of carrying RHC variants was 3.04 (1.90-4.86). Current study confirms the increased MM risk for R151C carriers. It also supports the association between R163Q variant and MM risk in the population on the Canary Islands, as opposed to reported on northern populations. These results highlight the importance of the sample population selection in this kind of studies.

Distribution of MC1R variants among melanoma subtypes: p.R163Q is associated with lentigo maligna melanoma in a Mediterranean population

BACKGROUND

Cutaneous melanoma tumour is classified into clinicohistopathological subtypes that may be associated with different genetic and host factors. Variation in the MC1R gene is one of the main factors of risk variation in sporadic melanoma. The relationship between MC1R variants and the risk of developing a specific subtype of melanoma has not been previously explored.

OBJECTIVES

To analyse whether certain MC1R variants are associated with particular melanoma subtypes with specific clinicohistopathological features.

METHODS

An association study was performed between MC1R gene variants and clinicopathological subtypes of primary melanoma derived from 1679 patients.

RESULTS

We detected 53 MC1R variants (11 synonymous and 42 nonsynonymous). Recurrent nonsynonymous variants were p.V60L (30·0%), p.V92M (11·7%), p.D294H (9·4%), p.R151C (8·8%), p.R160W (6·2%), p.R163Q (4·2%) p.R142H (3·3%), p.I155T (3·8%), p.V122M (1·5%) and p.D84E (1·0%). Melanoma subtypes showed differences in the total number of MC1R variants (P = 0·028) and the number of red hair colour variants (P = 0·035). Furthermore, an association between p.R163Q and lentigo maligna melanoma was detected under a dominant model of heritance (odds ratio 2·16, 95% confidence interval 1·07-4·37; P = 0·044). No association was found between p.R163Q and Fitzpatrick skin phototype, eye colour or skin colour, indicating that the association was independent of the role of MC1R in pigmentation. No association was observed between MC1R polymorphisms and other melanoma subtypes.

CONCLUSIONS

Our findings suggest that certain MC1R variants could increase melanoma risk due to their impact on pathways other than pigmentation, and may therefore be linked to specific melanoma subtypes.

The toxicity of nitrofuran compounds on melanoma and neuroblastoma cells is enhanced by Olaparib and ameliorated by melanin pigment

Nitrofurans are commonly used for the treatment of trypanosomal diseases including Chagas disease. More recently, following the fortuitous discovery that nifurtimox was clinically active against neuroblastoma, nitrofuran compounds are being investigated for activity against cancer. Herein, we show that nitrofuran compounds are similarly potent to human malignant melanoma and neuroblastoma cells. Furthermore, a recently discovered nitrofuran compound, NFN1, was 50- to 175-fold more potent than nifurtimox against human melanoma and neuroblastoma cell lines. As nitrofuran compounds are known to act as pro-drugs, producing DNA-damaging reactive intermediates upon activation, we investigated the DNA repair pathways involved. We show that, contrary to research in Escherichia coli, the Nucleotide Excision Repair pathway is not required to repair nitrofuran-induced DNA damage in mammalian cells. Instead, we show that inhibiting repair of single-strand DNA breaks with the poly(ADP-ribose) polymerase (PARP) inhibitor, Olaparib, enhances nitrofuran toxicity in melanoma and neuroblastoma cells. We propose that this is due to mammalian cells utilising Type 2 nitroreductases for nitrofuran activation producing Reactive Oxygen Species which cause DNA damage that is repaired by the Single Strand Break Repair and/or Base Excision Repair pathways, whereas in bacteria and trypanosomes, Type 1 nitroreductases are also utilised resulting in different DNA lesions. In addition we show that, consistent with Reactive Oxygen Species being formed upon nitrofuran activation and the ability of melanin to absorb Reactive Oxygen Species, production of melanin in melanoma cells offers some protection from NFN1- and hydrogen peroxide-induced toxicity. Our data suggest that combinations of Olaparib and nitrofuran compounds may be advantageous for the treatment of melanoma and neuroblastoma, but that the protection offered to melanoma cells by their melanin pigment must be taken into account.

Simultaneous purifying selection on the ancestral MC1R allele and positive selection on the melanoma-risk allele V60L in south Europeans

In humans, the geographical apportionment of the coding diversity of the pigmentary locus melanocortin-1 receptor (MC1R) is, unusually, higher in Eurasians than in Africans. This atypical observation has been interpreted as the result of purifying selection due to functional constraint on MC1R in high UV-B radiation environments. By analyzing 3,142 human MC1R alleles from different regions of Spain in the context of additional haplotypic information from the 1000 Genomes (1000G) Project data, we show that purifying selection is also strong in southern Europe, but not so in northern Europe. Furthermore, we show that purifying and positive selection act simultaneously on MC1R. Thus, at least in Spain, regions at opposite ends of the incident UV-B radiation distribution show significantly different frequencies for the melanoma-risk allele V60L (a mutation also associated to red hair and fair skin and even blonde hair), with higher frequency of V60L at those regions of lower incident UV-B radiation. Besides, using the 1000G south European data, we show that the V60L haplogroup is also characterized by an extended haplotype homozygosity (EHH) pattern indicative of positive selection. We, thus, provide evidence for an adaptive value of human skin depigmentation in Europe and illustrate how an adaptive process can simultaneously help to maintain a disease-risk allele. In addition, our data support the hypothesis proposed by Jablonski and Chaplin (Human skin pigmentation as an adaptation to UVB radiation. Proc Natl Acad Sci U S A. 2010;107:8962-8968), which posits that habitation of middle latitudes involved the evolution of partially depigmented phenotypes that are still capable of suitable tanning.

MC1R genotype as a predictor of early-onset melanoma, compared with self-reported and physician-measured traditional risk factors: an Australian case-control-family study

Background

Melanocortin-1 receptor (MC1R) gene variants are very common and are associated with melanoma risk, but their contribution to melanoma risk prediction compared with traditional risk factors is unknown. We aimed to 1) evaluate the separate and incremental contribution of MC1R genotype to prediction of early-onset melanoma, and compare this with the contributions of physician-measured and self-reported traditional risk factors, and 2) develop risk prediction models that include MC1R, and externally validate these models using an independent dataset from a genetically similar melanoma population.

Methods

Using data from an Australian population-based, case-control-family study, we included 413 case and 263 control participants with sequenced MC1R genotype, clinical skin examination and detailed questionnaire. We used unconditional logistic regression to estimate predicted probabilities of melanoma. Results were externally validated using data from a similar study in England.

Results

When added to a base multivariate model containing only demographic factors, MC1R genotype improved the area under the receiver operating characteristic curve (AUC) by 6% (from 0.67 to 0.73; P < 0.001) and improved the quartile classification by a net 26% of participants. In a more extensive multivariate model, the factors that contributed significantly to the AUC were MC1R genotype, number of nevi and previous non-melanoma skin cancer; the AUC was 0.78 (95% CI 0.75-0.82) for the model with self-reported nevi and 0.83 (95% CI 0.80-0.86) for the model with physician-counted nevi. Factors that did not further contribute were sun and sunbed exposure and pigmentation characteristics. Adding MC1R to a model containing pigmentation characteristics and other self-reported risk factors increased the AUC by 2.1% (P = 0.01) and improved the quartile classification by a net 10% (95% CI 1-18%, P = 0.03).

Conclusions

Although MC1R genotype is strongly associated with skin and hair phenotype, it was a better predictor of early-onset melanoma than was pigmentation characteristics. Physician-measured nevi and previous non-melanoma skin cancer were also strong predictors. There might be modest benefit to measuring MC1R genotype for risk prediction even if information about traditional self-reported or clinically measured pigmentation characteristics and nevi is already available.

Pigmentation-related phenotypes and risk of prostate cancer

BACKGROUND

Solar ultraviolet radiation exposure has been inversely related to prostate cancer incidence and mortality, possibly mediated through vitamin D status. Pigmentation-related traits influence endogenous vitamin D synthesis and may alter risk of prostate cancer.

METHODS

We examined prostate cancer in relation to hair and eye colour, and skin phototype in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study cohort. Incident cancer was diagnosed in 1982 out of 20 863 men. Multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated from Cox proportional hazards models.

RESULTS

Prostate cancer risk did not differ by eye colour or skin phototype. Men with naturally red hair were significantly less likely to develop prostate cancer (HR=0.46, 95% CI 0.24-0.89) than men with light brown hair (reference).

CONCLUSION

The red hair phenotype, which results from polymorphisms in the melanocortin-1-receptor (MC1R) gene, is associated with lower risk of prostate cancer. This pigmentation-related trait may influence prostate cancer development either directly, through genetic effects or regulatory mechanisms related to MC1R, another nearby gene, or other pigmentation genes, or indirectly, through associations with other exposures such as sunlight or vitamin D status.

Coat color genotypes and risk and severity of melanoma in gray quarter horses

BACKGROUND

Both graying and melanoma formation in horses have recently been linked to a duplication in the STX17 gene. This duplication, as well as a mutation in the ASIP gene that increases MC1R pathway signaling, affects melanoma risk and severity in gray horses.

OBJECTIVE

To determine if melanoma susceptibility in gray Quarter Horses (QH) is lower than gray horses from other breeds because of decreased MC1R signaling resulting from a high incidence of the MC1R chestnut coat color allele in the QH population.

ANIMALS

A total of 335 gray QH with and without dermal melanomas.

METHODS

Blood or hair root samples were collected from all horses for DNA extraction and genotyping for STX17, ASIP, and MC1R genotypes. Age, sex, and external melanoma presence and grade were recorded. The effect of age and genotype on melanoma presence and severity was evaluated by candidate gene association.

RESULTS

Melanoma prevalence (16%) and grade (0.35) in this QH cohort was lower than that reported in other breeds. Age was significantly associated with melanoma prevalence (P = 5.28 × 10(-11)) and severity (P = 2.2 × 10(-13)). No significant effect of MC1R genotype on melanoma prevalence or severity was identified. An effect of ASIP genotype on melanoma risk was not detected. Low STX17 homozygosity precluded evaluation of the gray allele effect.

CONCLUSION AND CLINICAL IMPORTANCE

Melanoma prevalence and severity is lower in this population of gray QH than what is reported in other breeds. This could be because of the infrequent STX17 homozygosity, a mitigating effect of the MC1R mutation on ASIP potentiation of melanoma, other genes in the MC1R signaling pathway, or differences in breed genetic background.

The genetics of melanoma: recent advances

Cutaneous malignant melanoma results from the interplay of genetic, host, and environmental factors. Genetic factors implicated in melanoma etiology include inherited high-, intermediate-, and low-risk susceptibility genes as well as numerous somatic mutations in melanoma tumors. CDKN2A is the major high-risk melanoma susceptibility gene identified to date. Recent identification of low-risk loci has been accomplished predominantly through genome-wide association studies. Whole-exome and whole-genome studies have identified numerous genes somatically altered in melanoma tumors and highlighted a higher mutation load in melanoma tumors compared with those in other cancers. This higher load is believed to be attributable to the preponderance of cytosine-to-thymine nucleotide substitutions as a result of UV radiation exposure. Technological advances, particularly next-generation sequencing, have increased the opportunities for germline and somatic gene discovery in melanoma and are opening up new avenues for understanding melanoma pathogenesis as well as leading to new opportunities for treatment.

Colorful DNA polymorphisms in humans

In this review article we summarize current knowledge on how variation on the DNA level influences human pigmentation including color variation of iris, hair, and skin. We review recent progress in the field of human pigmentation genetics by focusing on the genes and DNA polymorphisms discovered to be involved in determining human pigmentation traits, their association with diseases particularly skin cancers, and their power to predict human eye, hair, and skin colors with potential utilization in forensic investigations.

Melanoma m (zero): diagnosis and therapy

This paper reviews the epidemiology, diagnosis, and treatment of M zero cutaneous melanoma including the most recent developments. This review also examined the main risk factors for melanoma. Tumor thickness measured according to Breslow, mitotic rate, ulceration, and growth phase has the greatest predictive value for survival and metastasis. Wide excision of the primary tumor is the only potentially curative treatment for primary melanoma. The sentinel node biopsy must be performed on all patients who have a primary melanoma with a Breslow thickness > 1 mm, or if the melanoma is from 0,75 mm to 1 mm thick but it is ulcerated and/or the mitotic index is ≥1. Total lymph node dissection consists in removing the residual lymph nodes in patients with positive sentinel node biopsy, or found positive on needle aspiration biopsy, without radiological evidence of spread. Isolated limb perfusion and isolated limb infusion are employed in patients within transit metastases with a rate of complete remission in around 50% and 38% of cases. Electrochemotherapy is mainly indicated for palliation in cases of metastatic disease, though it may sometimes be useful to complete isolated limb perfusion. The only agent found to affect survival as an adjuvant treatment is interferon alpha-2. Adjuvant radiotherapy improves local control of melanoma in patients at a high risk of recurrence after lymph node dissection.

NRAS and BRAF mutations in cutaneous melanoma and the association with MC1R genotype: findings from Spanish and Austrian populations

There is increasing epidemiologic and molecular evidence that cutaneous melanomas arise through multiple causal pathways. To further define the pathways to melanoma, we explored the relationship between germline and somatic mutations in a series of melanomas collected from 134 Spanish and 241 Austrian patients. Tumor samples were analyzed for melanocortin-1 receptor (MC1R) variants and mutations in the BRAF and NRAS genes. Detailed clinical data were systematically collected from patients. We found that NRAS-mutant melanomas were significantly more likely from older patients and BRAF-mutant melanomas were more frequent in melanomas from the trunk. We observed a nonsignificant association between germline MC1R status and somatic BRAF mutations in melanomas from trunk sites (odds ratio (OR) 1.8 (0.8-4.1), P=0.1), whereas we observed a significant inverse association between MC1R and BRAF for melanomas of the head and neck (OR 0.3 (0.1-0.8), P=0.02). This trend was observed in both the Spanish and Austrian populations.

Genetic variants in PARP1 (rs3219090) and IRF4 (rs12203592) genes associated with melanoma susceptibility in a Spanish population

Background

Few high penetrance genes are known in Malignant Melanoma (MM), however, the involvement of low-penetrance genes such as MC1R, OCA2, ASIP, SLC45A2 and TYR has been observed. Lately, genome-wide association studies (GWAS) have been the ideal strategy to identify new common, low-penetrance susceptibility loci. In this case–control study, we try to validate in our population nine melanoma associated markers selected from published GWAS in melanoma predisposition.

Methods

We genotyped the 9 markers corresponding to 8 genes (PARP1, MX2, ATM, CCND1, NADSYN1, CASP8, IRF4 and CYP2R1) in 566 cases and 347 controls from a Spanish population using KASPar probes. Genotypes were analyzed by logistic regression and adjusted by phenotypic characteristics.

Results

We confirm the protective role in MM of the rs3219090 located on the PARP1 gene (p-value 0.027). Additionally, this SNP was also associated with eye color (p-value 0.002). A second polymorphism, rs12203592, located on the IRF4 gene was associated with protection to develop MM for the dominant model (p-value 0.037). We have also observed an association of this SNP with both lentigines (p-value 0.014) and light eye color (p-value 3.76 × 10^-4). Furthermore, we detected a novel association with rs1485993, located on the CCND1 gene, and dark eye color (p-value 4.96 × 10^-4). Finally, rs1801516, located on the ATM gene, showed a trend towards a protective role in MM similar to the one firstly described in a GWAS study.

Conclusions

To our knowledge, this is the first time that these SNPs have been associated with MM in a Spanish population. We confirmed the proposed role of rs3219090, located on the PARP1 gene, and rs12203592, located on the IRF4 gene, as protective to MM along the same lines as have previous genome-wide associated works. Finally, we have seen associations between IRF4, PARP1, and CCND1 and phenotypic characteristics, confirming previous results for the IRF4 gene and presenting novel data for the last two, suggesting that pigmentation characteristics correlated with eye color are potential mediators between PARP1 and MM protection.

Melanoma risk associated with MC1R gene variants in Latvia and the functional analysis of rare variants

To evaluate the association of melanocortin 1 receptor gene (MC1R) variants with melanoma risk in a Latvian population, the MC1R gene was sequenced in 200 melanoma patients and 200 control persons. A functional study of previously uncharacterized, rare MC1R variants was also performed. In total, 26 different MC1R variants, including two novel variants Val165Ile and Val188Ile, were detected. The highest risk of melanoma was associated with the Arg151Cys variant (odds ratio (OR) 4.47, 95% confidence interval (CI) 2.19-9.14, P<0.001). A gene dosage effect was observed, with melanoma risk for carriers of two variants being twice (OR 3.98, 95% CI 2.15-7.38, P<0.001) that of carriers of one variant (OR 1.98, 95% CI 1.26-3.11, P=0.003). After stratification according to the pigmentation phenotype, the risk of melanoma remained in groups with otherwise protective phenotypes. Functional analyses of eight previously uncharacterized MC1R variants revealed that a subset of them is functionally relevant. Our results support the contribution of MC1R variants to a genetic predisposition to melanoma in Latvia.

MC1R variation and melanoma risk in relation to host/clinical and environmental factors in CDKN2A positive and negative melanoma patients

Host, environmental and genetic factors differently modulate cutaneous melanoma (CM) risk across populations. Currently, the main genetic risk determinants are germline mutations in the major known high-risk susceptibility genes, CDKN2A and CDK4, and variants of the low-risk gene MC1R, which is key in the pigmentation process. This case-control study aimed at investigating the influence of the main host and environmental risk factors and of MC1R variation on CM risk in 390 CDKN2A-negative and 49 CDKN2A-positive Italian individuals. Multivariate analysis showed that MC1R variation, number of nevi and childhood sunburns doubled CM risk in CDKN2A-negative individuals. In CDKN2A-positive individuals, family history of CM and presence of atypical nevi, rather than MC1R status, modified risk (20.75- and 2.83-fold, respectively). Occupational sun exposure increased CM risk (three to sixfold) in both CDKN2A-negative and CDKN2A-positive individuals, reflecting the occupational habits of the Ligurian population and the geographical position of Liguria.

Melanoma genetic testing, counseling, and adherence to skin cancer prevention and detection behaviors

BACKGROUND

Little is known about the impact of knowledge of CDKN2A and MC1R genotype on melanoma prevention behaviors like sun avoidance and skin examination in the context of familial melanoma.

METHODS

Seventy-three adults with a family history of melanoma were randomly assigned to be offered individualized CDKN2A and MC1R genotyping results in the context of a genetic counseling session, or the standard practice of not being offered counseling or disclosure of genotyping results. Mixed effects or longitudinal logistic models were used to determine whether the intervention affected change in sun protection habits, skin examinations, and perception and beliefs related to melanoma risk, prevention, and genetic counseling.

RESULTS

All participants in the intervention group who attended genetic counseling sessions chose to receive their test results. From baseline to follow-up, participants in the intervention group reported an increase in the frequency of skin self-examinations compared with a slight decrease in the control group (P = 0.002). Participants in the intervention group reported a smaller decrease in frequency of wearing a shirt with long sleeves than did participants in the control group (P = 0.047). No effect of the intervention was noted for other outcomes.

CONCLUSIONS

Feedback of CDKN2A and MC1R genotype among families without known pathogenic CDKN2A mutations does not seem to decrease sun protection behaviors.

IMPACT

While disclosure of CDKN2A and MC1R genotype did not have negative effects on prevention, the benefits of communicating this information remain unclear. The small number of families who tested positive for CDKN2A mutations in this study is a limitation.

Replication and predictive value of SNPs associated with melanoma and pigmentation traits in a Southern European case-control study

Background

Genetic association studies have revealed numerous polymorphisms conferring susceptibility to melanoma. We aimed to replicate previously discovered melanoma-associated single-nucleotide polymorphisms (SNPs) in a Greek case-control population, and examine their predictive value.

Methods

Based on a field synopsis of genetic variants of melanoma (MelGene), we genotyped 284 patients and 284 controls at 34 melanoma-associated SNPs of which 19 derived from GWAS. We tested each one of the 33 SNPs passing quality control for association with melanoma both with and without accounting for the presence of well-established phenotypic risk factors. We compared the risk allele frequencies between the Greek population and the HapMap CEU sample. Finally, we evaluated the predictive ability of the replicated SNPs.

Results

Risk allele frequencies were significantly lower compared to the HapMap CEU for eight SNPs (rs16891982 – SLC45A2, rs12203592 – IRF4, rs258322 – CDK10, rs1805007 – MC1R, rs1805008 - MC1R, rs910873 - PIGU, rs17305573- PIGU, and rs1885120 - MTAP) and higher for one SNP (rs6001027 – PLA2G6) indicating a different profile of genetic susceptibility in the studied population. Previously identified effect estimates modestly correlated with those found in our population (r = 0.72, P<0.0001). The strongest associations were observed for rs401681-T in CLPTM1L (odds ratio [OR] 1.60, 95% CI 1.22–2.10; P = 0.001), rs16891982-C in SCL45A2 (OR 0.51, 95% CI 0.34–0.76; P = 0.001), and rs1805007-T in MC1R (OR 4.38, 95% CI 2.03–9.43; P = 2×10⁻⁵). Nominally statistically significant associations were seen also for another 5 variants (rs258322-T in CDK10, rs1805005-T in MC1R, rs1885120-C in MYH7B, rs2218220-T in MTAP and rs4911442-G in the ASIP region). The addition of all SNPs with nominal significance to a clinical non-genetic model did not substantially improve melanoma risk prediction (AUC for clinical model 83.3% versus 83.9%, p = 0.66).

Conclusion

Overall, our study has validated genetic variants that are likely to contribute to melanoma susceptibility in the Greek population.

Melanoma prone families with CDK4 germline mutation: phenotypic profile and associations with MC1R variants

Background

CDKN2A and CDK4 are high risk susceptibility genes for cutaneous malignant melanoma. Melanoma families with CDKN2A germline mutations have been extensively characterised, whereas CDK4 families are rare and lack a systematic investigation of their phenotype.

Methods

All known families with CDK4 germline mutations (n=17) were recruited for the study by contacting the authors of published papers or by requests via the Melanoma Genetics Consortium (GenoMEL). Phenotypic data related to primary melanoma and pigmentation characteristics were collected. The CDK4 exon 2 and the complete coding region of the MC1R gene were sequenced.

Results

Eleven families carried the CDK4 R24H mutation whereas six families had the R24C mutation. The total number of subjects with verified melanoma was 103, with a median age at first melanoma diagnosis of 39 years. Forty-three (41.7%) subjects had developed multiple primary melanomas (MPM). A CDK4 mutation was found in 89 (including 62 melanoma cases) of 209 tested subjects. CDK4 positive family members (both melanoma cases and unaffected subjects) were more likely to have clinically atypical nevi than CDK4 negative family members (p<0.001). MPM subjects had a higher frequency of MC1R red hair colour variants compared with subjects with one tumour (p=0.010).

Conclusion

Our study shows that families with CDK4 germline mutations cannot be distinguished phenotypically from CDKN2A melanoma families, which are characterised by early onset of disease, increased occurrence of clinically atypical nevi, and development of MPM. In a clinical setting, the CDK4 gene should therefore always be examined when a melanoma family tests negative for CDKN2A mutation.

Genetic testing by cancer site: skin

Many hereditary cancer predisposition syndromes are associated with cutaneous findings, both benign and malignant. Dermatological examination and histopathology, when combined with a thorough personal and family medical history, play an important role in the diagnosis of cancer predisposition syndromes. Skin findings are an important diagnostic tool for a variety of cancer syndromes, including Cowden syndrome, Birt-Hogg-Dubé, hereditary leiomyomatosis renal cell carcinoma, and others. This article focuses on the phenotype, medical management, and genetic testing for 4 hereditary cancer syndromes that include cutaneous findings: hereditary melanoma, basal cell nevus syndrome, neurofibromatosis type 1, and neurofibromatosis type 2.

Update on the Epidemiology of Melanoma

Cutaneous malignant melanoma (CMM) has been increasing steadily in incidence over the past 30 years. Recent studies have explored associations between CMM and varying physiologic risk factors, such as nevi or hair and eye color, in addition to historical features such as a personal history of nonmelanoma skin cancer (NMSC), childhood cancers, Parkinson's Disease, hormone exposure and family history of CMM. Genome-wide association studies have also uncovered many genetic determinants of CMM risk. Ultimately, ultraviolet (UV) radiation exposure remains the most important modifiable risk factor for CMM. Organ transplant recipients, and nonsteroidal anti-inflammatory usage may also play a role. While risk factors are important to identify, effective campaigns to reduce the burden of disease through early detection and prevention are essential. We present detailed data regarding these facets of care for the CMM patient, and provide an update on the epidemiology of CMM.

Genetic variation at KIT locus may predispose to melanoma

As loss of KIT frequently occurs in melanoma progression, we hypothesized that KIT is implicated in predisposition to melanoma (MM). Thus, we sequenced the KIT coding region in 112 familial MM cases and 143 matched controls and genotyped tag single-nucleotide polymorphisms (SNPs) in two cohorts of melanoma patients and matched controls. Five rare KIT substitutions, all predicted possibly or probably deleterious, were identified in five patients, but none in controls [RR = 2.26 (1.26-2.26)]. Expressed in melanocyte lines, three substitutions inhibited KIT signaling. Comparison with exomes database (7020 alleles) confirmed a significant excess of rare deleterious KIT substitutions in patients. Additionally, a common SNP, rs2237028, was associated with MM risk, and 6 KIT variants were associated with nevus count. Our data strongly suggest that rare KIT substitutions predispose to melanoma and that common variants at KIT locus may also impact nevus count and melanoma risk.

MC1R variants predisposing to concomitant primary cutaneous melanoma in a monozygotic twin pair

Background

Concomitant primary cutaneous melanoma in monozygotic twins has been reported in only two pairs but in neither of them genetic analysis was performed. Two high-penetrance susceptibility genes, CDKN2A and CDK4 and one low-penetrance gene, MC1R, are well-defined genetic risk factors for melanoma. MITF has been recently identified as a novel intermediate risk melanoma-predisposing gene.

Case presentation

We describe the extraordinary occurrence of a primary cutaneous invasive melanoma in two 44-year-old identical, female twins, on the same body site within 30 days of each other and report for the first time the genetic analysis of melanoma susceptibility genes in both twins. Data on characteristics of the twins were collected through a standardized questionnaire and skin examination. Exons 1α, 1β, 2 and 3 of CDKN2A, exon 2 of CDK4, the entire open reading frame of MC1R and the recently described MITF c.952 G > A (p.Glu318Lys) variant were investigated by direct sequencing. Sequencing analysis of the high-penetrance susceptibility genes showed no changes in CDKN2A and in exon 2 of the CDK4 gene. Both patients were heterozygous for the same CDKN2A UTR c.*29C > G variant. Interestingly, the same two heterozygous variants of the MC1R were identified in both twins: the c.451C > T (p.Arg151Cys) and the c.456C > A (p.Tyr152*) variants. Neither patient showed the c.952 G > A (p.Glu318Lys) substitution in the MITF gene.

Conclusions

Identification of two high-risk MC1R variants in our identical twins in the absence of CDKN2A and CDK4 mutations highlights the contribution of low penetrance genes, such as MC1R, in melanoma susceptibility.

The effect of hair colour on anaesthetic requirements and recovery time after surgery

Patients with red hair are much more likely to have a variant of the melanocortin-1 receptor gene and this may affect sensitivity to general anaesthetics and pain response. We did a prospective, matched cohort study of 468 healthy adult patients undergoing general anaesthesia for elective surgery. All patients received an inhalational general anaesthetic. Anaesthetic drugs and doses used, hypnotic depth, recovery times, pain scores and quality of recovery scores were recorded. More men than women had red hair, so we did subgroup and multivariable analyses to account for this imbalance. There was no significant difference in recovery times, pain scores or quality of recovery scores in those with red hair. After adjusting for age, sex, American Society of Anesthesiologists physical status and duration of surgery, the recovery ratio for time to eye-opening in redheads was comparable to those with black or brown hair, 0.82 (0.57-1.19), P=0.30. We found no evidence that patient hair colour affects anaesthetic requirements or recovery characteristics in a broad range of surgical procedures.

Interpretation of melanoma risk feedback in first-degree relatives of melanoma patients

Little is known about how individuals might interpret brief genetic risk feedback. We examined interpretation and behavioral intentions (sun protection, skin screening) in melanoma first-degree relatives (FDRs) after exposure to brief prototypic melanoma risk feedback. Using a 3 by 2 experimental pre-post design where feedback type (high-risk mutation, gene environment, and nongenetic) and risk level (positive versus negative findings) were systematically varied, 139 melanoma FDRs were randomized to receive one of the six scenarios. All scenarios included an explicit reminder that melanoma family history increased their risk regardless of their feedback. The findings indicate main effects by risk level but not feedback type; positive findings led to heightened anticipated melanoma risk perceptions and anticipated behavioral intentions. Yet those who received negative findings often discounted their family melanoma history. As such, 25%, 30%, and 32% of those who received negative mutation, gene-environment, and nongenetic feedback, respectively, reported that their risk was similar to the general population. Given the frequency with which those who pursue genetic testing may receive negative feedback, attention is needed to identify ideal strategies to present negative genetic findings in contexts such as direct to consumer channels where extensive genetic counseling is not required.

Melanocortin-1 receptor, skin cancer and phenotypic characteristics (M-SKIP) project: study design and methods for pooling results of genetic epidemiological studies

Background

For complex diseases like cancer, pooled-analysis of individual data represents a powerful tool to investigate the joint contribution of genetic, phenotypic and environmental factors to the development of a disease. Pooled-analysis of epidemiological studies has many advantages over meta-analysis, and preliminary results may be obtained faster and with lower costs than with prospective consortia.

Design and methods

Based on our experience with the study design of the Melanocortin-1 receptor (MC1R) gene, SKin cancer and Phenotypic characteristics (M-SKIP) project, we describe the most important steps in planning and conducting a pooled-analysis of genetic epidemiological studies. We then present the statistical analysis plan that we are going to apply, giving particular attention to methods of analysis recently proposed to account for between-study heterogeneity and to explore the joint contribution of genetic, phenotypic and environmental factors in the development of a disease. Within the M-SKIP project, data on 10,959 skin cancer cases and 14,785 controls from 31 international investigators were checked for quality and recoded for standardization. We first proposed to fit the aggregated data with random-effects logistic regression models. However, for the M-SKIP project, a two-stage analysis will be preferred to overcome the problem regarding the availability of different study covariates. The joint contribution of MC1R variants and phenotypic characteristics to skin cancer development will be studied via logic regression modeling.

Discussion

Methodological guidelines to correctly design and conduct pooled-analyses are needed to facilitate application of such methods, thus providing a better summary of the actual findings on specific fields.

Melanoma: from mutations to medicine

Melanoma is often considered one of the most aggressive and treatment-resistant human cancers. It is a disease that, due to the presence of melanin pigment, was accurately diagnosed earlier than most other malignancies and that has been subjected to countless therapeutic strategies. Aside from early surgical resection, no therapeutic modality has been found to afford a high likelihood of curative outcome. However, discoveries reported in recent years have revealed a near avalanche of breakthroughs in the melanoma field-breakthroughs that span fundamental understanding of the molecular basis of the disease all the way to new therapeutic strategies that produce unquestionable clinical benefit. These discoveries have been born from the successful fruits of numerous researchers working in many-sometimes-related, although also distinct-biomedical disciplines. Discoveries of frequent mutations involving BRAF(V600E), developmental and oncogenic roles for the microphthalmia-associated transcription factor (MITF) pathway, clinical efficacy of BRAF-targeted small molecules, and emerging mechanisms underlying resistance to targeted therapeutics represent just a sample of the findings that have created a striking inflection in the quest for clinically meaningful progress in the melanoma field.

Characterization of nonacral melanoma patients without typical risk factors

A divergent pathway model to cutaneous melanoma is commonly accepted: sun sensitivity/chronic sun exposure and melanocytic instability. Although this dual model explains the development of most melanomas, clinical experience suggests other possible routes. The aim of this study was to explore the characteristics of patients who do not fit with these two pathways. We selected 818 patients with nonacral cutaneous melanoma and defined three groups: nevus-prone individuals, sun-sensitive individuals, and non-nevus-prone and non-sun-sensitive individuals. This group included patients without identifiable melanoma risk factors and comprised 52 patients (5.5% of the overall nonacral melanoma population). These patients were more frequently women, were more likely to present melanoma at a very young age (13.5% before 25 years), to have less frequent personal history of melanoma and remnants of pre-existing nevi, and to present tumors on the trunk and legs. We have identified a group of patients with fewer risk factors for melanoma that needs further studies to increase our understanding of melanoma development.