Melanoma
Molecular Genomic Profiling of Melanocytic Nevi
The benign melanocytic nevus is the most common tumor in humans and rarely transforms into cutaneous melanoma. Elucidation of the nevus genome is required to better understand the molecular steps of progression to melanoma. We performed whole genome sequencing on a series of 14 benign melanocytic nevi consisting of both congenital and acquired types. All nevi had driver mutations in the MAPK signaling pathway, either BRAF V600E or NRAS Q61R/L. No additional definite driver mutations were identified.Collagen Prolyl Hydroxylases Are Bifunctional Growth Regulators in Melanoma
Appropriate post-translational processing of collagen requires prolyl hydroxylation, catalyzed by collagen prolyl 3-hydroxylase and collagen prolyl 4-hydroxylase, and is essential for normal cell function. Here we have investigated the expression, transcriptional regulation, and function of the collagen prolyl 3-hydroxylase and collagen prolyl 4-hydroxylase families in melanoma. We show that the collagen prolyl 3-hydroxylase family exemplified by Leprel1 and Leprel2 is subject to methylation-dependent transcriptional silencing in primary and metastatic melanoma consistent with a tumor suppressor function.Support for the Safe Use of Zinc Oxide Nanoparticle Sunscreens: Lack of Skin Penetration or Cellular Toxicity after Repeated Application in Volunteers
Zinc oxide is a widely used broad-spectrum sunscreen, but concerns have been raised about the safety of its nanoparticle (NP) form. We studied the safety of repeated application of agglomerated zinc oxide (ZnO) NPs applied to human volunteers over 5 days by assessing the skin penetration of intact ZnO-NPs and zinc ions and measuring local skin toxicity. Multiphoton tomography with fluorescence lifetime imaging microscopy was used to directly visualize ZnO-NP skin penetration and viable epidermal metabolic changes in human volunteers.Resident Memory and Recirculating Memory T Cells Cooperate to Maintain Disease in a Mouse Model of Vitiligo
Tissue resident memory T cells (Trm) form in the skin in vitiligo and persist to maintain disease, as white spots often recur rapidly after discontinuing therapy. We and others have recently described melanocyte-specific autoreactive Trm in vitiligo lesions. Here, we characterize the functional relationship between Trm and recirculating memory T cells (Tcm) in our vitiligo mouse model. We found that both Trm and Tcm sensed autoantigen in the skin long after stabilization of disease, producing IFN-γ, CXCL9, and CXCL10.Genetic Abnormalities in Large to Giant Congenital Nevi: Beyond NRAS Mutations
Large and giant congenital melanocytic nevi (CMN) are rare melanocytic lesions mostly caused by postzygotic NRAS alteration. Molecular characterization is usually focused on NRAS and BRAF genes in a unique biopsy sample of the CMN. However, large/giant CMN may exhibit phenotypic differences among distinct areas, and patients differ in features such as presence of multiple CMN or spilus-like lesions. Herein, we have characterized a series of 21 large/giant CMN including patients with spilus-type nevi (9/21 patients, 42.8%).Assessing the Incremental Contribution of Common Genomic Variants to Melanoma Risk Prediction in Two Population-Based Studies
It is unclear to what degree genomic and traditional (phenotypic and environmental) risk factors overlap in their prediction of melanoma risk. We evaluated the incremental contribution of common genomic variants (in pigmentation, nevus, and other pathways) and their overlap with traditional risk factors, using data from two population-based case-control studies from Australia (n = 1,035) and the United Kingdom (n = 1,460) that used the same questionnaires. Polygenic risk scores were derived from 21 gene regions associated with melanoma and odds ratios from published meta-analyses.Automated Dermatological Diagnosis: Hype or Reality?
In this issue of the Journal of Investigative Dermatology, Han et al. (2018) have made a landmark contribution to the application of artificial intelligence (AI) in dermatologic diagnosis. Although previous studies have reported that computer algorithms can successfully diagnose skin cancer from medical images with human equivalency (Esteva et al., 2017; Ferris et al., 2015; Marchetti et al., 2018; Menzies et al., 2005), Han et al. have made their computer algorithm publicly available for external testing.Fractional Sunburn Threshold UVR Doses Generate Equivalent Vitamin D and DNA Damage in Skin Types I–VI but with Epidermal DNA Damage Gradient Correlated to Skin Darkness
Public health guidance recommends limiting sun exposure to sub-sunburn levels, but it is unknown whether these can gain vitamin D (for musculoskeletal health) while avoiding epidermal DNA damage (initiates skin cancer). Well-characterized healthy humans of all skin types (I–VI, lightest to darkest skin) were exposed to a low-dose series of solar simulated UVR of 20%–80% their individual sunburn threshold dose (minimal erythema dose). Significant UVR dose responses were seen for serum 25-hydroxyvitamin D and whole epidermal cyclobutane pyrimidine dimers (CPDs), with as little as 0.2 minimal erythema dose concurrently producing 25-hydroxyvitamin D and CPD.Lysosomes Support the Degradation, Signaling, and Mitochondrial Metabolism Necessary for Human Epidermal Differentiation
Keratinocytes undergo significant structural remodeling during epidermal differentiation, including a broad transformation of the proteome coupled with a reduction in total cellular biomass. This suggests that intracellular digestion of proteins and organelles is necessary for keratinocyte differentiation. Here, we use both genetic and pharmacologic approaches to demonstrate that autophagy and lysosomal functions are required for keratinocyte differentiation in organotypic human skin. Lysosomal activity was required for mechanistic target of rapamycin signaling and mitochondrial oxidative metabolism.CCR4 Is Critically Involved in Skin Allergic Inflammation of BALB/c Mice
Atopic dermatitis is a chronic inflammatory skin disease involving T-helper (Th) 2 cells, eosinophils, and mast cells. Although CCR4 is a major chemokine receptor expressed on Th2 cells and regarded as a potential therapeutic target for allergic diseases, its role in atopic dermatitis remains unclear. Here, by using a hydrogel patch as a transcutaneous delivery device for ovalbumin (an antigen) and Staphylococcus aureus δ-toxin (a mast cell activator), we efficiently induced acute atopic dermatitis–like skin lesions in BALB/c mice, a strain prone to Th2 responses, which were characterized by increased numbers of eosinophils, mast cells, and CCR4-expressing Th2 cells in the skin lesions; elevated levels of total and ovalbumin-specific IgE in the sera; and increased expression of IL-4, IL-17A, IL-22, CCL17, CCL22, and CCR4 in the skin lesions.SATB1 Defines a Subtype of Cutaneous CD30+ Lymphoproliferative Disorders Associated with a T-Helper 17 Cytokine Profile
Cutaneous CD30+ lymphoproliferative disorders (LPDs), including lymphomatoid papulosis (LyP) and primary cutaneous anaplastic large-cell lymphoma, comprise the second most common group of cutaneous T-cell lymphomas. Previously, we reported that special SATB1, a thymocyte-specific chromatin organizer, was overexpressed and promoted malignant T-cell proliferation in a portion of CD30+ LPDs. Here, we investigated the expression pattern of SATB1 in CD30+ LPDs with a large cohort of patient samples, and examined the potential of SATB1 as a molecular marker to classify CD30+ LPDs with differential clinicopathological behaviors.Whole-Exome Sequencing of Acquired Nevi Identifies Mechanisms for Development and Maintenance of Benign Neoplasms
The melanoma transformation rate of an individual nevus is very low despite the detection of oncogenic BRAF or NRAS mutations in 100% of nevi. Acquired melanocytic nevi do, however, mimic melanoma, and approximately 30% of all melanomas arise within pre-existing nevi. Using whole-exome sequencing of 30 matched nevi, adjacent normal skin, and saliva we sought to identify the underlying genetic mechanisms for nevus development. All nevi were clinically, dermoscopically, and histopathologically documented.CXCL5 Facilitates Melanoma Cell–Neutrophil Interaction and Lymph Node Metastasis
Chemokines influence tumor metastasis by targeting tumor, stromal, and hematopoietic cells. Characterizing the chemokine mRNA expression profile of human primary melanoma samples, we found CXCL5 significantly up-regulated in stage T4 primary melanomas when compared to thin melanomas (T1 stage). To characterize the role of CXCL5 in melanoma progression, we established a metastasizing murine xenograft model using CXCL5-overexpressing human melanoma cells. CXCL5 had no effect on melanoma proliferation in vitro and on primary tumor growth in vivo, but CXCL5-overexpressing tumors recruited high amounts of neutrophils and exhibited significantly increased lymphangiogenesis in our severe combined immune-deficient mouse model.Classification of the Clinical Images for Benign and Malignant Cutaneous Tumors Using a Deep Learning Algorithm
We tested the use of a deep learning algorithm to classify the clinical images of 12 skin diseases—basal cell carcinoma, squamous cell carcinoma, intraepithelial carcinoma, actinic keratosis, seborrheic keratosis, malignant melanoma, melanocytic nevus, lentigo, pyogenic granuloma, hemangioma, dermatofibroma, and wart. The convolutional neural network (Microsoft ResNet-152 model; Microsoft Research Asia, Beijing, China) was fine-tuned with images from the training portion of the Asan dataset, MED-NODE dataset, and atlas site images (19,398 images in total).Dissecting Wnt Signaling for Melanocyte Regulation during Wound Healing
Abnormal pigmentation is commonly seen in the wound scar. Despite advancements in the research of wound healing, little is known about the repopulation of melanocytes in the healed skin. Previous studies have shown the capacity of melanocyte stem cells in the hair follicle to contribute skin epidermal melanocytes after injury in mice and humans. Here, we focused on the Wnt pathway, known to be a vital regulator of melanocyte stem cells in efforts to better understand the regulation of follicle-derived epidermal melanocytes during wound healing.Inhibition of Human Tyrosinase Requires Molecular Motifs Distinctively Different from Mushroom Tyrosinase
Tyrosinase is the rate-limiting enzyme of melanin production and, accordingly, is the most prominent target for inhibiting hyperpigmentation. Numerous tyrosinase inhibitors have been identified, but most of those lack clinical efficacy because they were identified using mushroom tyrosinase as the target. Therefore, we used recombinant human tyrosinase to screen a library of 50,000 compounds and compared the active screening hits with well-known whitening ingredients. Hydroquinone and its derivative arbutin only weakly inhibited human tyrosinase with a half-maximal inhibitory concentration (IC50) in the millimolar range, and kojic acid showed a weak efficacy (IC50 > 500 μmol/L).High MITF Expression Is Associated with Super-Enhancers and Suppressed by CDK7 Inhibition in Melanoma
Cutaneous melanoma is an aggressive tumor that accounts for most skin cancer deaths. Among the physiological barriers against therapeutic success is a strong survival program driven by genes such as MITF that specify melanocyte identity, a phenomenon known in melanoma biology as lineage dependency. MITF overexpression is occasionally explained by gene amplification, but here we show that super-enhancers are also important determinants of MITF overexpression in some melanoma cell lines and tumors.
