New insights into pigmentary pathways and skin cancer

A UV-related risk analysis in ophthalmic malignancies: Increased UV exposure may cause ocular malignancies

Purpose

To explore the role of ultraviolet radiation (UVR) in the occurrence and development of various ocular malignancies.

Methods

In this article, we retrieved ocular malignancy data from the Global Cancer Observatory (GCO) and performed correlation analysis with the global UV index and sunshine duration. We searched for associated studies using the following databases: Embase, Pubmed, Cochrane Library, and Google Scholar. We conducted the literature by searching the Mesh terms denoting an exposure of interest ("UV radiation", "ultraviolet rays", and "ocular malignancies", All studies included are published until December 30, 2023 without language restrictions.

Results

The mechanisms and epidemiological statistics of UVR on the onset and progression of eyelid malignancies are the most studied and clear. The role of UVR in conjunctival melanoma is similar to that in eyelid melanoma. The relationship between uveal melanoma and UVR is controversial, however, it may have at least a certain impact on its prognosis. UVR causes ocular surface squamous neoplasia by further activating HPV infection.

Conclusions

UVR is a decisive risk factor for ocular malignancies, but the incidence of ultraviolet-induced tumors is also affected by many other factors. A correct and comprehensive understanding of the mechanisms of UVR in the pathogenesis of ocular malignant tumors can provide patients with more effective and selective immune regulation strategies.

Analysing the causal relationship between potentially protective and risk factors and cutaneous melanoma: A Mendelian randomization study

BACKGROUND

Previous observational studies reported altered melanoma risks in relation to many potential factors, such as coffee intake, smoking habits and photodamage-related conditions. Considering the susceptibility of epidemiological studies to residual confounders, there remains uncertainty about the actual causal roles of these reported factors in melanoma aetiology.

OBJECTIVES

This study aims to investigate the causal association between cutaneous melanoma (CM) and previously reported factors: coffee intake, alcohol consumption, lifetime smoking, socioeconomic status (SES), ease of skin tanning, childhood sunburn and facial ageing, providing insight into its underlying aetiology and preventative strategies.

METHODS

We utilized a two-sample MR analysis on data from the largest meta-analysis summary statistics of confirmed cutaneous melanoma including 30,134 patients. Genetic instrumental variables were constructed by identifying single nucleotide polymorphisms (SNPs) that associate with corresponding factors. Inverse variance weighted (IVW) was the primary MR method. For sensitivity and heterogeneity, MR Egger, weighted median, simple mode, weighted mode and MR Egger intercept tests were examined.

RESULTS

Cutaneous melanoma risks were found to be elevated in association with a predisposition towards ease of skin tanning (IVW: OR = 2.842, 95% CI 2.468-3.274, p < 0.001) and with childhood sunburn history (IVW: OR = 6.317, 95% CI 4.479-8.909, p < 0.001). Repeated MR after removing potential confounders and outliers demonstrated resolved horizontal pleiotropy and statistically significant results that closely mirrored the initial findings. Other potential factors, such as coffee intake, alcohol consumption, smoking and socioeconomic status (SES), indicated insignificant effects on melanoma risk in the analysis, and therefore, our Mendelian randomization study does not support their roles in modifying melanoma risks.

CONCLUSIONS

Our extensive MR analysis provides strong evidence of the causative role of ease of skin tanning and childhood sunburn history in elevating melanoma risk. Curtailing ultraviolet radiation (UVR) exposure may be the single best preventative strategy to reduce melanoma risk.

Opsin 5 is a key regulator of ultraviolet radiation-induced melanogenesis in human epidermal melanocytes

Background

Human skin, which is constantly exposed to solar ultraviolet radiation (UVR), has a unique ability to respond by increasing its pigmentation in a protective process driven by melanogenesis in human epidermal melanocytes (HEMs). However, the molecular mechanisms used by HEMs to detect and respond to UVR remain unclear.

Objectives

To investigate the function and potential mechanism of opsin 5 (OPN5), a photoreceptor responsive to UVR wavelengths, in melanogenesis in HEMs.

Methods

Melanin content in HEMs was determined using the NaOH method, and activity of tyrosinase (TYR) (a key enzyme in melanin synthesis) was determined by the l‐DOPA method. OPN5 expression in UVR‐treated vs. untreated HEMs and explant tissues was detected by reverse‐transcription quantitative polymerase chain reaction (RT‐qPCR), Western blotting and immunofluorescence. Short interfering RNA‐mediated OPN5 knockdown and a lentivirus OPN5 overexpression model were used to examine their respective effects on TYR, tyrosinase‐related protein 1 (TRP1), TRP2 and microphthalmia‐associated transcription factor (MITF) expression, under UVR. Changes in expression of TYR, TRP1 and TRP2 caused by changes in OPN5 expression level were detected by RT‐qPCR and Western blot. Furthermore, changes in signalling pathway proteins were assayed.

Results

We found that OPN5 is the key sensor in HEMs responsible for UVR‐induced melanogenesis. OPN5‐induced melanogenesis required Ca²⁺‐dependent G protein‐coupled receptor‐ and protein kinase C signal transduction, thus contributing to the UVR‐induced MITF response to mediate downstream cellular effects, and providing evidence of OPN5 function in mammalian phototransduction. Remarkably, OPN5 activation was necessary for UVR‐induced increase in cellular melanin and has an inherent function in melanocyte melanogenesis.

Conclusions

Our results provide insight into the molecular mechanisms of UVR sensing and phototransduction in melanocytes, and may reveal molecular targets for preventing pigmentation or pigment diseases.

What is already known about this topic?

Ultraviolet radiation (UVR) induces a protective response to DNA damage mediated by melanin synthesis in human epidermal melanocytes (HEMs).

Tyrosinase (TYR), with tyrosinase‐related proteins (TRP1, TRP2), are the key enzymes for melanin synthesis.

Microphthalmia‐associated transcription factor regulates key genes for melanocyte development and differentiation, and can stimulate melanogenesis by activating transcription of TYR and other pigmentation genes, including TRP1.

Opsin 5 (OPN5) is known to function as a photoreceptor responsive to wavelengths in the near UV spectrum.

What does this study add?

UVR induces melanogenesis in HEMs via OPN5.

OPN5 regulates expression of TYR, TRP1 and TRP2 through the calcium‐dependent G protein‐coupled and protein kinase C signalling pathways.

OPN5 has an inherent role in HEMs in mediating melanogenesis.

What is the translational message?

OPN5 was discovered as a key sensor for UVR‐induced melanogenesis in human skin melanocytes.

It could be a target for early treatment of pigmentation or pigment diseases, to provide a more personalized and economically feasible method.

Linked Comment: L.V.M. de Assis and A.M. de Lauro Castrucci. Br J Dermatol 2021; 185:249–250.

Plain language summary available online

Oncogenic BRAF, endoplasmic reticulum stress, and autophagy: Crosstalk and therapeutic targets in cutaneous melanoma

BRAF is a member of the RAF family of serine/threonine-specific protein kinases. Oncogenic BRAF, in particular, BRAF V600E, can disturb the normal protein folding machinery in the endoplasmic reticulum (ER) leading to accumulation of unfolded/misfolded proteins in the ER lumen, a condition known as endoplasmic reticulum (ER) stress. To alleviate such conditions, ER-stressed cells have developed a highly robust and adaptable signaling network known as unfolded protein response (UPR). UPR is ordinarily a cytoprotective response and usually operates through the induction of autophagy, an intracellular lysosomal degradation pathway that directs damaged proteins, protein aggregates, and damaged organelles for bulk degradation and recycling. Both ER stress and autophagy are involved in the progression and chemoresistance of melanoma. Melanoma, which arises as a result of malignant transformation of melanocytes, exhibits exceptionally high therapeutic resistance. Many mechanisms of therapeutic resistance have been identified in individual melanoma patients and in preclinical BRAF-driven melanoma models. Recently, it has been recognized that oncogenic BRAF interacts with GRP78 and removes its inhibitory influence on the three fundamental ER stress sensors of UPR, PERK, IRE1α, and ATF6. Dissociation of GRP78 from these ER stress sensors prompts UPR that subsequently activates cytoprotective autophagy. Thus, pharmacological inhibition of BRAF-induced ER stress-mediated autophagy can potentially resensitize BRAF mutant melanoma tumors to apoptosis. However, the underlying molecular mechanism of how oncogenic BRAF elevates the basal level of ER stress-mediated autophagy in melanoma tumors is not well characterized. A better understanding of the crosstalk between oncogenic BRAF, ER stress and autophagy may provide a rationale for improving existing cancer therapies and identify novel targets for therapeutic intervention of melanoma.

Modulation of Diacylglycerol-Induced Melanogenesis in Human Melanoma and Primary Melanocytes: Role of Stress Chaperone Mortalin

Skin color/pigmentation is regulated through melanogenesis process in specialized melanin-producing cells, melanocytes, involving multiple signaling pathways. It is highly influenced by intrinsic and extrinsic factors such as oxidative, ultraviolet radiations and other environmental stress conditions. Besides determining the color, it governs response and tolerance of skin to a variety of environmental stresses and pathological conditions including photodamage, hyperpigmentation, and skin cancer. Depigmenting reagents have been deemed useful not only for cosmetics but also for pigmentation-related pathologies. In the present study, we attempted modulation of 1-oleoyl-2-acetyl-glycerol- (OAG-) induced melanogenesis in human melanoma and primary melanocytes. In both cell types, OAG-induced melanogenesis was associated with increase in enhanced expression of melanin, tyrosinase, as well as stress chaperones (mortalin and HSP60) and Reactive Oxygen Species (ROS). Treatment with TXC (trans-4-(Aminomethyl) cyclohexanecarboxylic acid hexadecyl ester hydrochloride) and 5/40 natural compounds resulted in their reduction. The data proposed an important role of mortalin and oxidative stress in skin pigmentation and the use of TXC and natural extracts for modulation of pigmentation pathways in normal and pathological conditions.

Amelioration of UV radiation-induced photoaging by a combinational sunscreen formulation via aversion of oxidative collagen degradation and promotion of TGF-β-Smad-mediated collagen production

The presence of 40-50% more UV radiation in high altitude areas renders the plethora of sunscreen products available in the market virtually ineffective. In this light of event, four US FDA approved UV filters were combined with melatonin and pumpkin seed oil to produce a broad spectrum sunscreen cream, which is envisaged to provide optimum sunprotection along with enhanced antioxidant activity. The objective of this study is to evaluate the protective effect of the sunscreen cream against UV radiation-induced skin photoaging in adult Wistar albino rats and identify its possible underlying mechanism. Wistar rats were exposed to broad spectrum UV radiation for 28 days. The test group received the sunscreen formulation dermally every day prior to UV radiation. The effects of the formulation against UV induced symptoms; viz. skin thickness and edema, in vivo antioxidant activities, inflammatory cytokines, collagen content, histopathological examination and expression of specific genes established the protective activity of the formulation. The test formulation was able to mitigate the harmful effects of UV radiation by increasing in vivo SOD, GSH-Px, CAT and collagen levels; decreasing skin edema, skin thickness and cytokines like IL-6, IL-1β, TNF-α and TGF-β1. UV radiation induced changes in histological architecture and arrangement of collagen and elastin fibers were also prevented by the test formulation. Finally, the formulation was able to regulate the expression of COL3A1, COX-2, bFGF, VEGF-C, Smad2, Smad4, Smad7 genes which induced significant photoprotective activity. The sunscreen formulation ameliorated UV induced photoaging by preventing oxidative collagen degradation and augmentation of TGF-β-Smad-mediated collagen production.

3-O-Glyceryl-2-O-hexyl ascorbate suppresses melanogenesis by interfering with intracellular melanosome transport and suppressing tyrosinase protein synthesis

BACKGROUND

Ascorbic acid (AsA) has multifunctional benefits on skin beauty, such as the reduction in oxidative stress and the induction of collagen production. Among them, the prevention and improvement of skin pigmentation by AsA is a most important benefit for people. However, it is well known that AsA not only is quite unstable in formulations but it also has a low capability of skin penetration due to its hydrophilic property. In addition, existing water-soluble AsA derivatives that were developed to improve its stability also have low skin penetration.

AIM

To investigate the potential of a newly synthesized amphiphilic derivative of AsA, 3-O-Glyceryl-2-O-hexyl ascorbate (VC-HG), which has an added glyceryl group and a hexyl group, on skin beauty focusing on its skin lightening/whitening effects.

METHODS

DNA microarray analysis and real-time PCR were used to clarify the effects of VC-HG on melanogenesis using B16 mouse melanoma cells. The effects of VC-HG on melanin synthesis, tyrosinase protein levels, and the inhibition of tyrosinase activity were evaluated.

RESULTS

DNA microarray analysis revealed that treatment with VC-HG downregulated the expression of genes encoding tyrosinase and MyosinVa. Further, real-time PCR analysis showed the downregulation of tyrosinase, MyosinVa, Rab27a, and Kinesin mRNAs following VC-HG treatment. In addition, VC-HG caused decreases in tyrosinase protein levels and melanin synthesis.

CONCLUSION

We conclude that VC-HG has an impact on skin lightening/whitening by inhibiting tyrosinase protein synthesis and interfering with intracellular melanosome transport.

CK1α ablation in keratinocytes induces p53-dependent, sunburn-protective skin hyperpigmentation

Casein kinase 1α (CK1α), a component of the β-catenin destruction complex, is a critical regulator of Wnt signaling; its ablation induces both Wnt and p53 activation. To characterize the role of CK1α (encoded by Csnk1a1) in skin physiology, we crossed mice harboring floxed Csnk1a1 with mice expressing K14-Cre-ER^T2 to generate mice in which tamoxifen induces the deletion of Csnk1a1 exclusively in keratinocytes [single-knockout (SKO) mice]. As expected, CK1α loss was accompanied by β-catenin and p53 stabilization, with the preferential induction of p53 target genes, but phenotypically most striking was hyperpigmentation of the skin, importantly without tumorigenesis, for at least 9 mo after Csnk1a1 ablation. The number of epidermal melanocytes and eumelanin levels were dramatically increased in SKO mice. To clarify the putative role of p53 in epidermal hyperpigmentation, we established K14-Cre-ER^T2 CK1α/p53 double-knockout (DKO) mice and found that coablation failed to induce epidermal hyperpigmentation, demonstrating that it was p53-dependent. Transcriptome analysis of the epidermis revealed p53-dependent up-regulation of Kit ligand (KitL). SKO mice treated with ACK2 (a Kit-neutralizing antibody) or imatinib (a Kit inhibitor) abrogated the CK1α ablation-induced hyperpigmentation, demonstrating that it requires the KitL/Kit pathway. Pro-opiomelanocortin (POMC), a precursor of α-melanocyte-stimulating hormone (α-MSH), was not activated in the CK1α ablation-induced hyperpigmentation, which is in contrast to the mechanism of p53-dependent UV tanning. Nevertheless, acute sunburn effects were successfully prevented in the hyperpigmented skin of SKO mice. CK1α inhibition induces skin-protective eumelanin but no carcinogenic pheomelanin and may therefore constitute an effective strategy for safely increasing eumelanin via UV-independent pathways, protecting against acute sunburn.

Stress chaperone mortalin regulates human melanogenesis

In order to identify the cellular factors involved in human melanogenesis, we carried out shRNA-mediated loss-of-function screening in conjunction with induction of melanogenesis by 1-oleoyl-2-acetyl-glycerol (OAG) in human melanoma cells using biochemical and visual assays. Gene targets of the shRNAs (that caused loss of OAG-induced melanogenesis) and their pathways, as determined by bioinformatics, revealed involvement of proteins that regulate cell stress response, mitochondrial functions, proliferation, and apoptosis. We demonstrate, for the first time, that the mitochondrial stress chaperone mortalin is crucial for melanogenesis. Upregulation of mortalin was closely associated with melanogenesis in in vitro cell-based assays and clinical samples of keloids with hyperpigmentation. Furthermore, its knockdown resulted in compromised melanogenesis. The data proposed mortalin as an important protein that may be targeted to manipulate pigmentation for cosmetic and related disease therapeutics.

[Updates on prevention and treatment of melanoma: Pharmacist involvements and challenges]

Melanoma is a skin cancer that represents an actual public health problem. Its incidence is increasing every year. Environmental risk factors have been clearly identified. Early diagnosis of a suspicious skin lesion should be possible by any health professionals because the prognosis is correlated with the evolution of the disease and the presence of metastases. The advent of new therapies in metastatic forms with the development of immunotherapies and kinases inhibitors has significantly changed the management of this disease. New therapies are available in retail pharmacies and involve health professionals out of the hospital. This article is intended for community and hospital pharmacists and summarizes recommendations for primary and secondary prevention. It updates on new targeted therapies. It wants to give advices to the community pharmacists about the effective use of those treatments for melanoma.

Skin Cancer Prevention, Tanning and Vitamin D: A Content Analysis of Print Media in Germany and Switzerland

BACKGROUND

Print media are a major source of health information.

OBJECTIVES

To analyse press coverage related to skin cancer prevention.

METHODS

We conducted a content analysis of print media articles pertaining to skin cancer prevention, solaria and vitamin D published in Germany and Switzerland over a 1-year period between 2012 and 2013.

RESULTS

Overall, 2,103 articles were analysed. Applying sunscreen was by far the most common sun protection recommendation. A considerable number of articles on solaria and vitamin D advocated exposure to ultraviolet radiation to enhance physical appearance and vitamin D photosynthesis, often without mentioning any precaution measures. In total, 26.8% of the articles contained misleading or erroneous statements mostly related to sunscreen use and vitamin D issues.

CONCLUSIONS

Print media can serve as powerful education tools to foster skin cancer prevention. However, misleading or erroneous reports may negatively impact sun-safe behaviour.

UV signaling pathways within the skin

The effects of UVR on the skin include tanning, carcinogenesis, immunomodulation, and synthesis of vitamin D, among others. Melanocortin 1 receptor polymorphisms correlate with skin pigmentation, UV sensitivity, and skin cancer risk. This article reviews pathways through which UVR induces cutaneous stress and the pigmentation response. Modulators of the UV tanning pathway include sunscreen agents, MC1R activators, adenylate cyclase activators, phosphodiesterase 4D3 inhibitors, T oligos, and MITF regulators such as histone deacetylase (HDAC)-inhibitors. UVR, as one of the most ubiquitous carcinogens, represents both a challenge and enormous opportunity in skin cancer prevention.

The role of melanocortin 1 receptor in cutaneous malignant melanoma: along the mitogen-activated protein kinase pathway

Cutaneous malignant melanoma (CMM) is an epidemic cancer in the United States. Survival rates for invasive CMM have not increased in past decades despite numerous clinical trials and the effective use of various combinations of chemotherapy agents to treat other cancers. Recent research has investigated the role of melanocortin 1 receptor (MC1R), a gene associated with red-hair phenotype in White individuals and with increased risk for developing CMM, in the mitogen-activated protein kinase (MAPK) pathway. This limited narrative review discusses the incidence, history, and risk factors for CMM. It explores familial CMM and provides a brief review of melanocyte development and melanogenesis. Histology of CMM and cytogenetic techniques used to identify CMM mutations is also discussed. The structure and function of MC1R is described, with particular attention to MC1R's role in the MAPK pathway. Finally, the review touches on individualized therapy for CMM using genetic biomarkers and explores the promise of genomic research for finding effective treatments.

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.

microRNA regulation of skin pigmentation in fish

MicroRNAs (miRNAs) are endogenous small non-coding RNAs that play crucial roles in numerous biological processes. However, the role of miRNAs in skin color determination in fish has not been completely determined. Here, we identified that 13 miRNAs are differentially expressed between red and white skin. The analysis of miRNA spatial and temporal expression patterns suggests that miR-429 is potential regulator of skin pigmentation. miR-429 silencing results in a obvious change in skin pigmentation. Bioinformatics analysis and luciferase reporter assay shows that miR-429 directly regulates Foxd3 expression by targeting its 3′ untranslated (3′-UTR) region. miR-429 silencing leads to a significant increase in Foxd3 expression in vivo, thereby repressing the transcription of MITF and its downstream genes such as TYR, TYRP1, or TYRP2. These findings would provide a novel insight into the determination of skin color in fish.

The role of alpha-synuclein in melanin synthesis in melanoma and dopaminergic neuronal cells

The relatively high co-occurrence of Parkinson's disease (PD) and melanoma has been established by a large number of epidemiological studies. However, a clear biological explanation for this finding is still lacking. Ultra-violet radiation (UVR)-induced skin melanin synthesis is a defense mechanism against UVR-induced damage relevant to the initiation of melanoma, whereas, increased neuromelanin (NM), the melanin synthesized in dopaminergic neurons, may enhance the susceptibility to oxidative stress-induced neuronal injury relevant to PD. SNCA is a PD-causing gene coding for alpha-Synuclein (α-Syn) that expresses not only in brain, but also in skin as well as in tumors, such as melanoma. The findings that α-Syn can interact with tyrosinase (TYR) and inhibit tyrosine hydroxylase (TH), both of which are enzymes involved in the biosynthesis of melanin and dopamine (DA), led us to propose that α-Syn may participate in the regulation of melanin synthesis. In this study, by applying ultraviolet B (UVB) light, a physiologically relevant stimulus of melanogenesis, we detected melanin synthesis in A375 and SK-MEL-28 melanoma cells and in SH-SY5Y and PC12 dopaminergic neuronal cells and determined effects of α-Syn on melanin synthesis. Our results showed that UVB light exposure increased melanin synthesis in all 4 cell lines. However, we found that α-Syn expression reduced UVB light-induced increase of melanin synthesis and that melanin content was lower when melanoma cells were expressed with α-Syn, indicating that α-Syn may have inhibitory effects on melanin synthesis in melanoma cells. Different from melanoma cells, the melanin content was higher in α-Syn-over-expressed dopaminergic neuronal SH-SY5Y and PC12 cells, cellular models of PD, than that in non-α-Syn-expressed control cells. We concluded that α-Syn could be one of the points responsible for the positive association between PD and melanoma via its differential roles in melanin synthesis in melanoma cells and in dopaminergic neuronal cells.

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.

A germline variant in the TP53 polyadenylation signal confers cancer susceptibility

To identify new risk variants for cutaneous basal cell carcinoma, we performed a genome-wide association study of 16 million SNPs identified through whole-genome sequencing of 457 Icelanders. We imputed genotypes for 41,675 Illumina SNP chip-typed Icelanders and their relatives. In the discovery phase, the strongest signal came from rs78378222[C] (odds ratio (OR) = 2.36, P = 5.2 × 10(-17)), which has a frequency of 0.0192 in the Icelandic population. We then confirmed this association in non-Icelandic samples (OR = 1.75, P = 0.0060; overall OR = 2.16, P = 2.2 × 10(-20)). rs78378222 is in the 3' untranslated region of TP53 and changes the AATAAA polyadenylation signal to AATACA, resulting in impaired 3'-end processing of TP53 mRNA. Investigation of other tumor types identified associations of this SNP with prostate cancer (OR = 1.44, P = 2.4 × 10(-6)), glioma (OR = 2.35, P = 1.0 × 10(-5)) and colorectal adenoma (OR = 1.39, P = 1.6 × 10(-4)). However, we observed no effect for breast cancer, a common Li-Fraumeni syndrome tumor (OR = 1.06, P = 0.57, 95% confidence interval 0.88-1.27).

Making sense of the latest advice on vitamin D therapy

The Institute of Medicine recently published recommendations for the daily intake and optimal serum levels of vitamin D based on an extensive review of the existing literature. Here we examine the issue and put levels of vitamin D in context for the general population and in patients with chronic kidney disease. Large randomized controlled trials are necessary to ensure that current recommendations are appropriate.

Melanotropic peptides: more than just 'Barbie drugs' and 'sun-tan jabs'?

While ultraviolet radiation (UVR) is a major cause of skin ageing and carcinogenesis, public pursuit of a novel tanning strategy circumventing the need for UVR is increasingly reported in the media and scientific press. This involves the subcutaneous self-administration of unregulated products labelled as melanotan I and/or II, synthetic analogues of α-melanocyte stimulating hormone (α-MSH), as obtained via the internet, tanning salons and gyms. The Medicines and Healthcare products Regulatory Authority has recently raised awareness of the public health risk of transmission of blood-borne viruses from the needle sharing that may occur, and of the potential impurity of these products. Dermatologists should also be aware that these agents can complicate the clinical presentation of patients with pigmented lesions; their use may be suspected in unexpectedly tanned individuals with rapidly pigmenting naevi. Meanwhile, the regulated α-MSH analogue afamelanotide (Clinuvel Pharmaceuticals Ltd, Melbourne, Australia) is showing promise for its photoprotective potential, and is undergoing phase II and III clinical trials in people with photosensitivity disorders and those prone to nonmelanoma skin cancer. The photoprotective and other biological effects of α-MSH analogues await full determination.

Colloquium paper: human skin pigmentation as an adaptation to UV radiation

Human skin pigmentation is the product of two clines produced by natural selection to adjust levels of constitutive pigmentation to levels of UV radiation (UVR). One cline was generated by high UVR near the equator and led to the evolution of dark, photoprotective, eumelanin-rich pigmentation. The other was produced by the requirement for UVB photons to sustain cutaneous photosynthesis of vitamin D(3) in low-UVB environments, and resulted in the evolution of depigmented skin. As hominins dispersed outside of the tropics, they experienced different intensities and seasonal mixtures of UVA and UVB. Extreme UVA throughout the year and two equinoctial peaks of UVB prevail within the tropics. Under these conditions, the primary selective pressure was to protect folate by maintaining dark pigmentation. Photolysis of folate and its main serum form of 5-methylhydrofolate is caused by UVR and by reactive oxygen species generated by UVA. Competition for folate between the needs for cell division, DNA repair, and melanogenesis is severe under stressful, high-UVR conditions and is exacerbated by dietary insufficiency. Outside of tropical latitudes, UVB levels are generally low and peak only once during the year. The populations exhibiting maximally depigmented skin are those inhabiting environments with the lowest annual and summer peak levels of UVB. Development of facultative pigmentation (tanning) was important to populations settling between roughly 23 degrees and 46 degrees , where levels of UVB varied strongly according to season. Depigmented and tannable skin evolved numerous times in hominin evolution via independent genetic pathways under positive selection.