Sancy A. Leachman

Melanocytes as instigators and victims of oxidative stress

Epidermal melanocytes are particularly vulnerable to oxidative stress due to the pro-oxidant state generated during melanin synthesis, and to intrinsic antioxidant defences that are compromised in pathologic conditions. Melanoma is thought to be oxidative stress-driven, and melanocyte death in vitiligo is thought to be instigated by a highly pro-oxidant state in the epidermis. We review the current knowledge about melanin and the redox state of melanocytes, how paracrine factors help counteract oxidative stress, the role of oxidative stress in melanoma initiation and progression and in melanocyte death in vitiligo, and how this knowledge can be harnessed for melanoma and vitiligo treatment.

Clinical validation of a gene expression signature that differentiates benign nevi from malignant melanoma

Histopathologic examination is sometimes inadequate for accurate and reproducible diagnosis of certain melanocytic neoplasms. As a result, more sophisticated and objective methods have been sought. The goal of this study was to identify a gene expression signature that reliably differentiated benign and malignant melanocytic lesions and evaluate its potential clinical applicability. Herein, we describe the development of a gene expression signature and its clinical validation using multiple independent cohorts of melanocytic lesions representing a broad spectrum of histopathologic subtypes.

Detection of Exosomal miRNAs in the Plasma of Melanoma Patients.

MicroRNAs (miRNAs) are a class of 22–25 nucleotide RNAs that control gene expression at the post-transcriptional level. MiRNAs have potential as cancer biomarkers. Melanoma is a highly aggressive form of skin cancer accounting for almost 4% of cancers among men and women, and ~80% of skin cancer-related deaths in the US. In the present study we analyzed plasma-derived exosomal miRNAs from clinically affected and unaffected familial melanoma patients (CDKN2A/p16 gene carriers) and compared them with affected (nonfamilial melanoma) and unaffected control subjects in order to identify novel risk biomarkers for melanoma. Intact miRNAs can be isolated from the circulation because of their presence in exosomes. A number of differentially regulated miRNAs identified by NanoString human V2 miRNA array were validated by quantitative PCR. Significantly, miR-17, miR-19a, miR-21, miR-126, and miR-149 were expressed at higher levels in patients with metastatic sporadic melanoma as compared with familial melanoma patients or unaffected control subjects. Surprisingly, no substantial differences in miRNA expression were detected between familial melanoma patients (all inclusive) and unaffected control subjects. The miRNAs differentially expressed in the different patient cohorts, especially in patients with metastatic melanoma, may play important roles in tumor progression and metastasis, and may be used as predictive biomarkers to monitor remission as well as relapse following therapeutic intervention.

Pediatric Melanoma: Analysis of an International Registry

The management of pediatric melanoma (PM) has largely been extrapolated from adult data. However, the behavior of PM appears to differ from its adult counterparts. Therefore, an international PM registry was created and analyzed.

Melanocortins and the melanocortin 1 receptor, moving translationally towards melanoma prevention.

Beginning in the last decade of the twentieth century, the fields of pigment cell research and melanoma have witnessed major breakthroughs in the understanding of the role of melanocortins in human pigmentation and the DNA damage response of human melanocytes to solar ultraviolet radiation (UV). This began with the cloning of the melanocortin 1 receptor (MC1R) gene from human melanocytes and the demonstration that the encoded receptor is functional. Subsequently, population studies found that the MC1R gene is highly polymorphic, and that some of its variants are associated with red hair phenotype, fair skin and poor tanning ability. Using human melanocytes cultured from donors with different MC1R genotypes revealed that the alleles associated with red hair color encode for a non-functional receptor. Epidemiological studies linked the MC1R red hair color variants to increased melanoma risk. Investigating the impact of different MC1R variants on the response of human melanocytes to UV led to the important discovery that the MC1R signaling activates antioxidant, DNA repair and survival pathways, in addition to stimulation of eumelanin synthesis. These effects of MC1R were absent in melanocytes expressing 2 MC1R red hair color variants that result in loss of function of the receptor. The importance of the MC1R in reducing UV-induced genotoxicity in melanocytes led us to design small peptide analogs of the physiological MC1R agonist α-melanocortin (α-melanocyte stimulating hormone; α-MSH) for the goal of utilizing them for melanoma chemoprevention.

Lymphatic Vessels, Inflammation, and Immunity in Skin Cancer

UNLABELLEDnSkin is a highly ordered immune organ that coordinates rapid responses to external insult while maintaining self-tolerance. In healthy tissue, lymphatic vessels drain fluid and coordinate local immune responses; however, environmental factors induce lymphatic vessel dysfunction, leading to lymph stasis and perturbed regional immunity. These same environmental factors drive the formation of local malignancies, which are also influenced by local inflammation. Herein, we discuss clinical and experimental evidence supporting the tenet that lymphatic vessels participate in regulation of cutaneous inflammation and immunity, and are important contributors to malignancy and potential biomarkers and targets for immunotherapy.nnnSIGNIFICANCEnThe tumor microenvironment and tumor-associated inflammation are now appreciated not only for their role in cancer progression but also for their response to therapy. The lymphatic vasculature is a less-appreciated component of this microenvironment that coordinates local inflammation and immunity and thereby critically shapes local responses. A mechanistic understanding of the complexities of lymphatic vessel function in the unique context of skin provides a model to understand how regional immune dysfunction drives cutaneous malignancies, and as such lymphatic vessels represent a biomarker of cutaneous immunity that may provide insight into cancer prognosis and effective therapy.

The state of melanoma: challenges and opportunities

The Melanoma Research Foundation (MRF) has charted a comprehensive assessment of the current state of melanoma research and care. Intensive discussions among members of the MRF Scientific Advisory Council and Breakthrough Consortium, a group that included clinicians and scientists, focused on four thematic areas – diagnosis/early detection, prevention, tumor cell dormancy (including metastasis), and therapy (response and resistance). These discussions extended over the course of 2015 and culminated at the Society of Melanoma Research 2015 International Congress in November. Each of the four groups has outlined their thoughts as per the current status, challenges, and opportunities in the four respective areas. The current state and immediate and long‐term needs of the melanoma field, from basic research to clinical management, are presented in the following report.

Epistatic and Combinatorial Effects of Pigmentary Gene Mutations in the Domestic Pigeon

Understanding the molecular basis of phenotypic diversity is a critical challenge in biology, yet we know little about the mechanistic effects of different mutations and epistatic relationships among loci that contribute to complex traits. Pigmentation genetics offers a powerful model for identifying mutations underlying diversity and for determining how additional complexity emerges from interactions among loci. Centuries of artificial selection in domestic rock pigeons (Columba livia) have cultivated tremendous variation in plumage pigmentation through the combined effects of dozens of loci. The dominance and epistatic hierarchies of key loci governing this diversity are known through classical genetic studies, but their molecular identities and the mechanisms of their genetic interactions remain unknown. Here we identify protein-coding and cis-regulatory mutations in Tyrp1, Sox10, and Slc45a2 that underlie classical color phenotypes of pigeons and present a mechanistic explanation of their dominance and epistatic relationships. We also find unanticipated allelic heterogeneity at Tyrp1 and Sox10, indicating that color variants evolved repeatedly though mutations in the same genes. These results demonstrate how a spectrum of coding and regulatory mutations in a small number of genes can interact to generate substantial phenotypic diversity in a classic Darwinian model of evolution.

Isolation of circulating microRNAs from microvesicles found in human plasma

Intact miRNAs can be isolated from the circulation in significant quantities despite the presence of extremely high levels of RNase activity. The remarkable stability of circulating miRNAs makes them excellent candidates for biomarkers in diagnostic applications as well as therapeutic targets in a variety of disease states including melanoma. Circulating RNA molecules are resistant to degradation by RNases because they are encapsulated in membrane-bound microvesicles. We describe a convenient method for the use of ExoQuick, a proprietary resin developed by Systems Biosciences (Mountain View, CA), whereby microvesicles can be purified under gentle conditions using readily available laboratory equipment. This protocol allows for isolation all microvesicles, regardless of their origin, and provides a convenient method for identifying potential cancer-specific biomarkers from biological fluids including serum and plasma.

Addressing the knowledge gap in clinical recommendations for management and complete excision of clinically atypical nevi/dysplastic nevi: Pigmented Lesion Subcommittee consensus statement.

IMPORTANCEnThe management of clinically atypical nevi/dysplastic nevi (CAN/DN) is controversial, with few data to guide the process. Management recommendations for DN with positive histologic margins were developed by the Delphi method to achieve consensus among members of the Pigmented Lesion Subcommittee (PLS) of the Melanoma Prevention Working Group (MPWG) after reviewing the current evidence.nnnOBJECTIVESnTo outline key issues related to the management of CAN/DN: (1) biopsies of CAN and how positive margins arise, (2) whether incompletely excised DN evolve into melanoma, (3) current data on the outcomes of DN with positive histologic margins, (4) consensus recommendations, and (5) a proposal for future studies, including a large-scale study to help guide the management of DN with positive margins.nnnEVIDENCE REVIEWnThe literature, including recent studies examining management and outcomes of DN with positive margins between 2009 to 2014, was reviewed.nnnFINDINGSnA consensus statement by the PLS of the MPWG following review of the literature, group discussions, and a structured Delphi method consensus.nnnCONCLUSIONS AND RELEVANCEnThis consensus statement reviews the complexities of management of CAN/DN. A review of the literature and 2 rounds of a structured Delphi consensus resulted in the following recommendations: (1) mildly and moderately DN with clear margins do not need to be reexcised, (2) mildly DN biopsied with positive histologic margins without clinical residual pigmentation may be safely observed rather than reexcised, and (3) observation may be a reasonable option for management of moderately DN with positive histologic margins without clinically apparent residual pigmentation; however, more data are needed to make definitive recommendations in this clinical scenario.