Histologic and Phenotypic Factors and MC1R Status Associated with BRAF(V600E), BRAF(V600K), and NRAS Mutations in a Community-Based Sample of 414 Cutaneous Melanomas

PRAME Is an Effective Tool for the Diagnosis of Nevus-Associated Cutaneous Melanoma

(1) Background: Nevus-associated cutaneous melanoma (CM) is relatively common in the clinical practice of dermatopathologists. The correct diagnosis and staging of nevus-associated cutaneous melanoma (CM) mainly relies on the correct discrimination between benign and malignant cells. Recently, PRAME has emerged as a promising immunohistochemical marker of malignant melanocytes. (2) Methods: PRAME immunohistochemistry (IHC) was performed in 69 cases of nevus-associated CMs. Its expression was evaluated using a score ranging from 0 to 4+ based on the percentage of melanocytic cells with a nuclear expression. PRAME IHC sensitivity, specificity, positive predictive values, and negative predictive values were assessed. Furthermore, the agreement between morphological data and PRAME expression was evaluated for the diagnosis of melanoma components and nevus components. (3) Results: PRAME IHC showed a sensitivity of 59%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 71%. The diagnostic agreement between morphology and PRAME IHC was fair (Cohen's Kappa: 0.3); the diagnostic agreement regarding the benign nevus components associated with CM was perfect (Cohen's Kappa: 1.0). PRAME was significantly more expressed in thick invasive CMs than in thin cases (p = 0.02). (4) Conclusions: PRAME IHC should be considered for the diagnostic evaluation of nevus-associated CM and is most useful in cases of thick melanomas. Pathologists should carefully consider that a PRAME-positive cellular population within the context of a nevus could indicate a CM associated with the nevus. A negative result does not rule out this possibility.

A review of nevus-associated melanoma: What is the evidence?

Cutaneous melanoma may have an adjacent nevus remnant on histological examination in 30% of cases (nevus-associated melanoma, NAM), while it may appear de novo, without a precursor lesion, in the remaining 70% of cases. Nevus-associated melanoma and the concept of acquired melanocytic nevi serving as precursors of melanoma, has long been considered as a controversial topic. This controversy is, in part, due to their overall low rate of transformation to melanoma and scarce data on the natural history of progression. Another matter of debate regarded the possibility that the reported differences of NAM versus de novo melanoma, were due to an underestimation of NAM in thicker lesions due to obliteration of the nevus component by the tumour. During the last few years, several evidence has accumulated in order to address these controversies. In this review, we present a comprehensive synthesis of the epidemiological, clinical, dermoscopic and genetic findings in NAM, including thin NAM, compared to de novo melanoma. Answering the questions on nevus-associated melanoma may provide further insight on the classification of these tumours and disentangle their biology and route of development from that of de novo melanoma.

The BRAF V600E Mutation Detection by quasa Sensitive Real-Time PCR Assay in Northeast Romania Melanoma Patients

Background: The prevalence of melanoma in Romanian patients is underestimated. There is a need to identify the BRAF V600E mutation to accurately treat patients with the newest approved BRAF inhibitor therapy. This is a pilot study in which we first aimed to choose the optimal DNA purification method from formalin fixation and paraffin embedding (FFPE) malignant melanoma skin samples to assess the BRAF mutation prevalence and correlate it with clinical pathological parameters. Methods: 30 FFPE samples were purified in parallel with two DNA extraction kits, a manual and a semi-automated kit. The extracted DNA in pure and optimum quantity was tested for the BRAF V600E mutation using the quantitative allele-specific amplification (quasa) method. quasa is a method for the sensitive detection of mutations that may be present in clinical samples at low levels. Results: The BRAF V600E mutation was detected in 60% (18/30) samples in patients with primary cutaneous melanoma of the skin. BRAFV600E mutation was equally distributed by gender and was associated with age >60, nodular melanoma, and trunk localization. Conclusions: The high prevalence of BRAF V600E mutations in our study group raises awareness for improvements to the national reporting system and initiation of the target therapy for patients with malignant melanoma of the skin.

Behind the Scene: Exploiting MC1R in Skin Cancer Risk and Prevention

Melanoma and non-melanoma skin cancers (NMSCs) are the most frequent cancers of the skin in white populations. An increased risk in the development of skin cancers has been associated with the combination of several environmental factors (i.e., ultraviolet exposure) and genetic background, including melanocortin-1 receptor (MC1R) status. In the last few years, advances in the diagnosis of skin cancers provided a great impact on clinical practice. Despite these advances, NMSCs are still the most common malignancy in humans and melanoma still shows a rising incidence and a poor prognosis when diagnosed at an advanced stage. Efforts are required to underlie the genetic and clinical heterogeneity of melanoma and NMSCs, leading to an optimization of the management of affected patients. The clinical implications of the impact of germline MC1R variants in melanoma and NMSCs' risk, together with the additional risk conferred by somatic mutations in other peculiar genes, as well as the role of MC1R screening in skin cancers' prevention will be addressed in the current review.

Germline MC1R variants and frequency of somatic BRAF, NRAS, and TERT mutations in melanoma: Literature review and meta-analysis

Germline variants of the melanocortin-1-receptor (MC1R) gene are the most common genetic trait predisposing to cutaneous melanoma (CM). Here, we performed a literature review and meta-analysis of the association between MC1R gene variants and the frequency of somatic mutations of the BRAF, NRAS, and TERT genes in CM patients. We included studies published until January 2020 in MEDLINE, EMBASE, Ovid Medline, and two grey literature databases. Random effect models were used to pool study-specific estimates into summary odds ratio (SOR) and 95% confidence intervals (CIs). Subgroup and sensitivity analyses were conducted to identify potential sources of heterogeneity and assess the robustness of pooled estimates. Twelve studies published between 2006 and 2018 (encompassing 3566 CM, mostly on nonacral sites) were included. MC1R gene variants were not significantly associated with the frequency of somatic mutations of the BRAF and NRAS genes. Only three studies focused on somatic mutations of the TERT gene promoter, all of which reported moderate-to-strong positive associations with MC1R germline variants. MC1R gene variants appear to make only moderate changes, if any, to the risk of BRAF- or NRAS-mutant CM. The association with TERT promoter mutations is suggestive, yet it warrants confirmation as it is based on a still limited number of studies.

Evolution of approaches to identify melanoma missing heritability

Introduction: Around 10% of melanoma patients have a positive family history of melanoma and/or related cancers. Although a germline pathogenic variant in a high-risk gene can be identified in up to 40% of these patients, the remaining part of melanoma heritability remains largely unexplained.Areas covered: The aim of this review is to provide an overview of the impact that new technologies and new research approaches had and are having on finding more efficient ways to unravel the missing heritability in melanoma.Expert opinion: High-throughput sequencing technologies have been crucial in increasing the number of genes/loci that might be implicated in melanoma predisposition. However, results from these approaches may have been inferior to the expectations, due to an increase in quantitative information which hasn't been followed at the same speed by an improvement of the methods to correctly interpret these data. Optimal approaches for improving our knowledge on melanoma heritability are currently based on segregation analysis coupled with functional assessment of candidate genes. An improvement of computational methods to infer genotype-phenotype correlations could help address the issue of missing heritability.

Molecular evaluation of BRAF V600 mutation and its association with clinicopathological characteristics: First findings from Indian malignant melanoma patients

Mutations in the BRAF gene have been described to occur in two-third of melanomas. The objective of the study was to establish the frequency of BRAF V600E/K/R mutation in a series of melanomas from Indian origin and to correlate mutation status with clinicopathological features. Seventy melanoma cases were evaluated for BRAF V600 mutation by pyrosequencing. Overall, BRAF mutations were detected in 30% of the patients. All mutations observed were missense type (GTG > GAG) resulting in p.V600E, while none showed V600K/R mutation. The frequency of BRAF V600E mutations were more in patients with onset age of 50 years. BRAF mutations were significantly associated with tumor site wherein more mutations were seen in tumors from head and neck and extremities region. Acral and mucosal tumor subtype showed a mutation frequency of 31% and 20%, respectively. Epithelial cell morphology tends to harbor frequent BRAF V600E mutation (36%) than other morphological subtypes. Tumors with ulceration and necrosis showed increased BRAF mutation rate (32.5% and 33%) respectively. In conclusion, this is the first study to report a mutation frequency of 30% in this cohort. Our results demonstrated that the BRAF V600E mutation is a frequent event in Indian melanomas, and represents an important molecular target for novel therapeutic approaches.

Melanoma - role of the environment and genetics

Melanoma rates have increased in populations that are mainly European. The main etiologic factor is ultraviolet radiation, from the sun as well as artificial tanning devices. Host factors such as skin color, number of nevi, hair and eye color and tanning ability are critical factors in modifying an individual's response to the sun. Genetic factors interact with host factors and environmental factors to increase risk. This review summarizes our current knowledge of environment and genetics on melanoma risk and on gene-environment interaction.

Inherited Genetic Variants Associated with Melanoma BRAF/NRAS Subtypes

BRAF and NRAS mutations arise early in melanoma development, but their associations with low-penetrance melanoma susceptibility loci remain unknown. In the Genes, Environment and Melanoma Study, 1,223 European-origin participants had their incident invasive primary melanomas screened for BRAF/NRAS mutations and germline DNA genotyped for 47 single-nucleotide polymorphisms identified as low-penetrant melanoma-risk variants. We used multinomial logistic regression to simultaneously examine each single-nucleotide polymorphism's relationship to BRAF V600E, BRAF V600K, BRAF other, and NRAS+ relative to BRAF-/NRAS- melanoma adjusted for study features. IRF4 rs12203592*T was associated with BRAF V600E (odds ratio [OR] = 0.59, 95% confidence interval [CI] = 0.43-0.79) and V600K (OR = 0.65, 95% CI = 0.41-1.03), but not BRAF other or NRAS+ melanoma. A global test of etiologic heterogeneity (Pglobal = 0.001) passed false discovery (Pglobal = 0.0026). PLA2G6 rs132985*T was associated with BRAF V600E (OR = 1.32, 95% CI = 1.05-1.67) and BRAF other (OR = 1.82, 95% CI = 1.11-2.98), but not BRAF V600K or NRAS+ melanoma. The test for etiologic heterogeneity (Pglobal) was 0.005. The IRF4 rs12203592 associations were slightly attenuated after adjustment for melanoma-risk phenotypes. The PLA2G6 rs132985 associations were independent of phenotypes. IRF4 and PLA2G6 inherited genotypes may influence melanoma BRAF/NRAS subtype development.

Replacement of Arg with Nle and modified D-Phe in the core sequence of MSHs, Ac-His-D-Phe-Arg-Trp-NH2, leads to hMC1R selectivity and pigmentation

Melanoma skin cancer is the fastest growing cancer in the US [1]. A great need exists for improved formulations and mechanisms to prevent and protect human skin from cancers and other skin damage caused by sunlight exposure. Current efforts to prevent UV damage to human skin, which in many cases leads to melanoma and other skin cancers. The primordial melanocortin-1 receptor (MC1R) is involved in regulating skin pigmentation and hair color, which is a natural prevention from UV damage. The endogenous melanocortin agonists induce pigmentation and share a core pharmacophore sequence "His-Phe-Arg-Trp", and it was found that substitution of the Phe by D-Phe results in increasing melanocortin receptor potency. To improve the melanocortin 1 receptor (MC1R) selectivity a series of tetra-peptides with the moiety of Ac-Xaa-Yaa-Nle-Trp-NH2, and structural modifications to reduce electrostatic ligand-receptor interactions have been designed and synthesized. It is discovered that the tetrapeptide Ac-His-D-Phe(4-CF3)-Nle-Trp-NH2 resulted in a potent and selective hMC1R agonist at the hMC1R (EC50: 10 nM). Lizard anolis carolinensis pigmentation study shows very high potency in vivo. NMR studies revealed a reversed β turn structure which led to the potency and selectivity towards the hMC1R.

Factors Related to Nevus-Associated Cutaneous Melanoma: A Case-Case Study

A proportion of cutaneous melanomas display neval remnants on histologic examination. Converging lines of epidemiologic and molecular evidence suggest that melanomas arising from nevus precursors differ from melanomas arising de novo. In a large, population-based study comprising 636 cutaneous melanomas subjected to dermatopathology review, we explored the molecular, host, and environmental factors associated with the presence of neval remnants. We found that nevus-associated melanomas were significantly associated with younger age at presentation, non-brown eye color, trunk site, thickness of less than 0.5 mm, and BRAF^V600E mutation. Compared with patients with de novo melanomas, those with nevus-associated tumors were more likely to self-report many moles on their skin as a teenager (odds ratio = 1.94, 95% confidence interval = 1.01-3.72) but less likely to report many facial freckles (odds ratio = 0.49, 95% confidence interval = 0.25-0.96). They also had high total nevus counts (odds ratio = 2.18, 95% confidence interval = 1.26-3.78). On histologic examination, nevus-associated melanomas exhibited less dermal elastosis in adjacent skin compared with de novo melanomas (odds ratio = 0.55, 95% confidence interval = 0.30-1.01). These epidemiologic data accord with the emerging molecular paradigm that nevus-associated melanomas arise through a distinct sequence of causal events that differ from those leading to other cutaneous melanomas.

Combining molecular and immunohistochemical analyses of key drivers in primary melanomas: interplay between germline and somatic variations

Due to the high mutational somatic burden of Cutaneous Malignant Melanoma (CMM) a thorough profiling of the driver mutations and their interplay is necessary to explain the timing of tumorigenesis or for the identification of actionable genetic events. The aim of this study was to establish the mutation rate of some of the key drivers in melanoma tumorigenesis combining molecular analyses and/or immunohistochemistry in 93 primary CMMs from an Italian cohort also characterized for germline status, and to investigate an interplay between germline and somatic variants. BRAF mutations were present in 68% of cases, while CDKN2A germline mutations were found in 16 % and p16 loss in tissue was found in 63%. TERT promoter somatic mutations were detected in 38% of cases while the TERT -245T>C polymorphism was found in 51% of cases. NRAS mutations were found in 39% of BRAF negative or undetermined cases. NF1 was expressed in all cases analysed. MC1R variations were both considered as a dichotomous variable or scored. While a positive, although not significant association between CDKN2A germline mutations, but not MC1R variants, and BRAF somatic mutation was found, we did not observe other associations between germline and somatic events. A yet undescribed inverse correlation between TERT -245T>C polymorphism and the presence of BRAF mutation was found. It is possible to hypothesize that -245T>C polymorphism could be included in those genotypes which may influence the occurrence of BRAF mutations. Further studies are needed to investigate the role of -245T>C polymorphism as a germline predictor of BRAF somatic mutation status.

Associations of MC1R Genotype and Patient Phenotypes with BRAF and NRAS Mutations in Melanoma

Associations of MC1R with BRAF mutations in melanoma have been inconsistent between studies. We sought to determine for 1,227 participants in the international population-based Genes, Environment, and Melanoma (GEM) study whether MC1R and phenotypes were associated with melanoma BRAF/NRAS subtypes. We used logistic regression adjusted by age, sex, and study design features and examined effect modifications. BRAF+ were associated with younger age, blond/light brown hair, increased nevi, and less freckling, and NRAS+ with older age relative to the wild type (BRAF-/NRAS-) melanomas (all P < 0.05). Comparing specific BRAF subtypes to the wild type, BRAF V600E was associated with younger age, blond/light brown hair, and increased nevi and V600K with increased nevi and less freckling (all P < 0.05). MC1R was positively associated with BRAF V600E cases but only among individuals with darker phototypes or darker hair (Pinteraction < 0.05) but inversely associated with BRAF V600K (Ptrend = 0.006) with no significant effect modification by phenotypes. These results support distinct etiologies for BRAF V600E, BRAF V600K, NRAS+, and wild-type melanomas. MC1R's associations with BRAF V600E cases limited to individuals with darker phenotypes indicate that MC1R genotypes specifically provide information about BRAF V600E melanoma risk in those not considered high risk based on phenotype. Our results also suggest that melanin pathways deserve further study in BRAF V600E melanomagenesis.

Sun exposure and skin cancer, and the puzzle of cutaneous melanoma: A perspective on Fears et al. Mathematical models of age and ultraviolet effects on the incidence of skin cancer among whites in the United States. American Journal of Epidemiology 1977; 105: 420-427

Sunlight has been known as an important cause of skin cancer since around the turn of the 20th Century. A 1977 landmark paper of US scientists Fears, Scotto, and Schneiderman advanced a novel hypothesis whereby cutaneous melanoma was primarily caused by intermittent sun exposure (i.e. periodic, brief episodes of exposure to high-intensity ultraviolet radiation) while the keratinocyte cancers, squamous cell carcinoma and basal cell carcinoma, were primarily caused by progressive accumulation of sun exposure. With respect to cutaneous melanoma, this became known as the intermittent exposure hypothesis. The hypothesis stemmed from analysis of measured ambient ultraviolet radiation and age-specific incidence rates of melanoma and keratinocyte cancers collected as an extension to the US Third National Cancer Survey in several US States. In this perspective paper, we put this novel hypothesis into the context of knowledge at the time, and describe subsequent epidemiological and molecular research into melanoma that elaborated the intermittent exposure hypothesis and ultimately replaced it with a dual pathway hypothesis. Our present understanding is of two distinct biological pathways by which cutaneous melanoma might develop; a nevus prone pathway initiated by early sun exposure and promoted by intermittent sun exposure or possibly host factors; and a chronic sun exposure pathway in sun sensitive people who progressively accumulate sun exposure to the sites of future melanomas.

MC1R signaling. Intracellular partners and pathophysiological implications

The melanocortin-1 receptor (MC1R) preferentially expressed in melanocytes is best known as a key regulator of the synthesis of epidermal melanin pigments. Its paracrine stimulation by keratinocyte-derived melanocortins also activates DNA repair pathways and antioxidant defenses to build a complex, multifaceted photoprotective response. Many MC1R actions rely on cAMP-dependent activation of two transcription factors, MITF and PGC1α, but pleiotropic MC1R signaling also involves activation of mitogen-activated kinases and AKT. MC1R partners such as β-arrestins, PTEN and the E3 ubiquitin ligase MGRN1 differentially regulate these pathways. The MC1R gene is complex and polymorphic, with frequent variants associated with skin phenotypes and increased cancer risk. We review current knowledge of signaling from canonical MC1R, its splice isoforms and natural polymorphic variants. Recently discovered intracellular targets and partners are also discussed, to highlight the diversity of mechanisms that may contribute to normal and pathological variation of pigmentation and sensitivity to solar radiation-induced damage. This article is part of a Special Issue entitled: Melanocortin Receptors - edited by Ya-Xiong Tao.

Systemic BRAF/MEK Inhibitors as a Potential Treatment Option in Metastatic Conjunctival Melanoma

AIM

In this review, we outline similarities between conjunctival and skin melanoma as well as the effectiveness of combined BRAF/MEK inhibition in melanoma, and discuss the applicability of these agents in conjunctival melanoma.

METHODS

The study provides a PubMed literature review.

RESULTS

Conjunctival melanoma and skin melanoma are genetically and phenotypically related. Both tumors typically harbor BRAF mutations in more than 50% of cases. New targeted therapies in metastatic skin melanoma include selective inhibition of BRAF and MEK. Combined BRAF/MEK inhibition has revolutionized the treatment of metastatic skin melanoma, significantly improving patients' prognoses. While these new substances have been investigated extensively in the treatment of skin melanoma, comparable studies in conjunctival melanoma do not exist owing to the rarity of the malignancy.

CONCLUSIONS

The application of combined BRAF/MEK inhibition in metastatic or unresectable conjunctival melanoma shows great potential for improving patients' prognoses. Future studies are needed to investigate the assumed benefit.