Melanocytic nevi and melanoma: unraveling a complex relationship. Oncogene. 2017;36:5771-5792. [PMID: 28604751 DOI: 10.1038/onc.2017.189]

Activated Hgf-Met Signaling Cooperates with Oncogenic BRAF to Drive Primary Cutaneous Melanomas and Angiotropic Lung Metastases in Mice

Oncogenic mutations in the BRAF kinase gene represent the most frequent genomic driver in acquired melanocytic nevi and in cutaneous melanomas. It is currently thought that oncogene-induced senescence and cell cycle arrest limit the ability of oncogenic BRAF to promote melanocyte proliferation in benign nevi. The molecular and cellular mechanisms that allow an oncogenic BRAF mutation to fully transform melanocytes into invasively growing melanoma cells that are able to metastasize systemically are only partially understood. In this study, we show in a genetic mouse model that constitutively enhanced Hgf-Met signaling cooperates with oncogenic BRAF to drive tumor development and metastatic spread. Activation of oncogenic BRAF in mice with transgenic Hgf overexpression and an oncogenic CDK4 germline mutation accelerated and increased the development of primary cutaneous melanomas. Primary melanomas showed considerable phenotypic heterogeneity with frequent signs of dedifferentiation. BRAF activation in Hgf-CDK4 mice also increased the number of lung metastases. Melanoma cells showed a pronounced angiotropic growth pattern both at the invasive front in primary tumors and in metastatic lesions of the lung. Taken together, our work supports the notion that activated Hgf-Met signaling and oncogenic BRAF can cooperate in melanoma pathogenesis.

The Complex Role of Autophagy in Melanoma Evolution: New Perspectives From Mouse Models

Despite tremendous efforts in the last decade to improve treatments, melanoma still represents a major therapeutic challenge and overall survival of patients remains poor. Therefore, identifying new targets to counteract melanoma is needed. In this scenario, autophagy, the “self-eating” process of the cell, has recently arisen as new potential candidate in melanoma. Alongside its role as a recycling mechanism for dysfunctional and damaged cell components, autophagy also clearly sits at a crossroad with metabolism, thereby orchestrating cell proliferation, bioenergetics and metabolic rewiring, all hallmarks of cancer cells. In this regard, autophagy, both in tumor and host, has been flagged as an essential player in melanomagenesis and progression. To pave the way to a better understanding of such a complex interplay, the use of genetically engineered mouse models (GEMMs), as well as syngeneic mouse models, has been undoubtedly crucial. Herein, we will explore the latest discoveries in the field, with particular focus on the potential of these models in unraveling the contribution of autophagy in melanoma, along with the therapeutic advantages that may arise.

Core‑shell type thermo‑nanoparticles loaded with temozolomide combined with photothermal therapy in melanoma cells

A novel core-shell type thermo-nanoparticle (CSTNP) co-loaded with temozolomide (TMZ) and the fluorescein new indocyanine green dye IR820 (termed IT-CSTNPs) was designed and combined with a near-infrared (NIR) laser to realize its photothermal conversion. The IT-CSTNPs were prepared using a two-step synthesis method and comprised a thermosensitive shell and a biodegradable core. IR820 and TMZ were entrapped in the shell and the core, respectively. Dynamic light scattering results demonstrated that the average hydrodynamic size of the IT-CSTNPs was 196.4±3.1 nm with a ζ potential of −24.9±1.3 mV. The encapsulation efficiencies of TMZ and IR820 were 6.1 and 16.6%, respectively. Temperature increase curves under NIR laser irradiation indicated that the IT-CSTNPs exhibited the desired photothermal conversion efficiency. The in vitro drug release curves revealed a suitable release capability of IT-CSTNP under physiological conditions, whereas NIR laser irradiation accelerated the drug release. Inverted fluorescence microscopy and flow cytometry results revealed that the uptake of IT-CSTNPs by A375 melanoma cells occurred in a concentration-dependent manner. Confocal laser scanning microscopy results indicated that IT-CSTNPs entered tumour cells via endocytosis and were located in intercellular lysosomes. In summary, the present study explored the photothermal conversion capability, cellular uptake, and intracellular localization of IT-CSTNPs.

Glucocorticoids delay RAF-induced senescence promoted by EGR1

Expression of hyperactive RAF kinases, such as the oncogenic B-RAF-V600E mutant, in normal human cells triggers a proliferative arrest that blocks tumor formation. We discovered that glucocorticoids delayed the entry into senescence induced by B-RAF-V600E in human fibroblasts, and allowed senescence bypass when the cells were regularly passaged, but that they did not allow proliferation of cells that were already senescent. Transcriptome and siRNA analyses revealed that the EGR1 gene is one target of glucocorticoid action. Transcription of the EGR1 gene is activated by the RAF-MEK-ERK MAPK pathway and acts as a sensor of hyper-mitogenic pathway activity. The EGR1 transcription factor regulates the expression of p15 and p21 (encoded by CDKN2B and CDKN1A, respectively) that are redundantly required for the proliferative arrest of BJ fibroblasts upon expression of B-RAF-V600E. Our results highlight the need to evaluate the action of glucocorticoid on cancer progression in melanoma, thyroid and colon carcinoma in which B-RAF-V600E is a frequent oncogene, and cancers in which evasion from senescence has been shown.

Autophagic Control of Skin Aging

The skin forms the barrier to the environment. Maintenance of this barrier during aging requires orchestrated responses to variable types of stress, the continuous renewal of the epithelial compartment, and the homeostasis of long-lived cell types. Recent experimental evidence suggests that autophagy is critically involved in skin homeostasis and skin aging is associated with and partially caused by defects of autophagy. In the outer skin epithelium, autophagy is constitutively active during cornification of keratinocytes and increases the resistance to environmental stress. Experimental suppression of autophagy in the absence of stress is tolerated by the rapidly renewing epidermal epithelium, whereas long-lived skin cells such as melanocytes, Merkel cells and secretory cells of sweat glands depend on autophagy for cellular homeostasis and normal execution of their functions during aging. Yet other important roles of autophagy have been identified in the dermis where senescence of mesenchymal cells and alterations of the extracellular matrix (ECM) are hallmarks of aging. Here, we review the evidence for cell type-specific roles of autophagy in the skin and their differential contributions to aging.

Black and Brown Oro-facial Mucocutaneous Neoplasms

Black and brown-colored mucocutaneous lesions present a differential diagnostic challenge, with malignant melanoma being the primary clinical concern. The vast majority of pigmented lesions in the head and neck region are the result of benign, reactive factors such as post-inflammatory melanosis. However, it is not uncommon to discover a range of muco-cutaneous black and brown neoplasms in the oro-facial area. The majority of black/brown pigmented neoplasms are melanocytic in origin; these are neoplasms of neural crest derivation. Melanocytic nevi are a diverse group of benign neoplasms that are the result of specific oncogenic mutations. They are common on cutaneous surfaces but can manifest in mucosal sites. Currently, nevi are classified based on clinical and histological criteria. The most common cutaneous and oral mucosal nevus is the acquired melanocytic nevus; nevi do not pose an increased risk for the development of malignant melanoma. Emerging information on specific genetic differences supports the notion of biologically distinct nevi. This article will review the classic clinical and microscopic features of nevi commonly found in the head and neck region, and discuss emerging concepts in nevus pathogenesis and taxonomy. Melanoma is a malignant melanocytic neoplasm and is a result of cumulative genetic deregulation. The etiology of malignant melanoma (MM) is multifactorial and includes underlying genetic susceptibility, UV radiation, skin-type, and race. The majority of MM occurs on cutaneous surfaces and less commonly on mucosal and extra-cutaneous visceral organs. Regardless of location, MM exhibits clinical-pathological features that relate to horizontal or vertical tumor spread. Cutaneous and mucosal MM typically present as asymmetrical, irregularly bordered, large (> 0.5 cm), heterogeneous brown-black lesions with foci of erythema, atrophy or ulceration. As with melanocytic nevi, advances in melanomagenesis research have revealed primary oncogenic BRAF and NRAS mutations associated with cutaneous MM. Unlike their cutaneous counterparts, mucosal melanomas exhibit primary oncogenic alterations in c-KIT and other genes. This article will discuss the role of specific primary oncogenic and secondary/tertiary genetic defects in differential clinical presentation, anatomic distribution, future classification changes, and targeted therapy of melanoma. The clinical and microscopic features of mucosal melanomas and a summary of management guidelines will be discussed. Additionally, this article will cover the salient features of melanocytic neuroectodermal tumor of infancy, a neoplastic entity that can involve the oro-facial region, and the clinical-pathological features of selected, commonly occurring pigmented ectodermally-derived neoplasms that are often part of the clinical differential diagnosis of black-brown pigmented lesions.

An Update Regarding the Molecular Genetics of Melanocytic Neoplasms and the Current Applications of Molecular Genetic Technologies in Their Diagnosis and Treatment

Molecular genetic technologies are used to aid in diagnosis and treatment of borderline melanocytic tumors as an adjuvant to the gold standard histopathologic evaluation. A specific set of fluorescence in situ hybridization probes is widely used to aid in diagnosing challenging melanocytic lesions. New melanoma probe cocktails have revealed increased sensitivity and specificity in ambiguous melanocytic cases. Array comparative genomic hybridization is a more complex technology used for the work-up of diagnostically problematic Spitzoid melanocytic proliferations. Cutting-edge technologies, including next-generation sequencing and cell-free nucleic acid analysis, are promising biomarker applications for mutation detection towards personalized patient management.

New Insights into the Runt Domain of RUNX2 in Melanoma Cell Proliferation and Migration

The mortality rate for malignant melanoma (MM) is very high, since it is highly invasive and resistant to chemotherapeutic treatments. The modulation of some transcription factors affects cellular processes in MM. In particular, a higher expression of the osteogenic master gene RUNX2 has been reported in melanoma cells, compared to normal melanocytes. By analyzing public databases for recurrent RUNX2 genetic and epigenetic modifications in melanoma, we found that the most common RUNX2 genetic alteration that exists in transcription upregulation is, followed by genomic amplification, nucleotide substitution and multiple changes. Additionally, altered RUNX2 is involved in unchecked pathways promoting tumor progression, Epithelial Mesenchymal Transition (EMT), and metastasis. In order to investigate further the role of RUNX2 in melanoma development and to identify a therapeutic target, we applied the CRISPR/Cas9 technique to explore the role of the RUNT domain of RUNX2 in a melanoma cell line. RUNT-deleted cells showed reduced proliferation, increased apoptosis, and reduced EMT features, suggesting the involvement of the RUNT domain in different pathways. In addition, del-RUNT cells showed a downregulation of genes involved in migration ability. In an in vivo zebrafish model, we observed that wild-type melanoma cells migrated in 81% of transplanted fishes, while del-RUNT cells migrated in 58%. All these findings strongly suggest the involvement of the RUNT domain in melanoma metastasis and cell migration and indicate RUNX2 as a prospective target in MM therapy.

Tumor suppression by the EGR1, DMP1, ARF, p53, and PTEN Network

Recent studies have indicated that EGR1 is a direct regulator of tumor suppressors including TGFβ1, PTEN, and p53. The Myb-like transcription factor Dmp1 is a physiological regulator of the Arf-p53 pathway through transactivation of the Arf promoter and physical interaction of p53. The Dmp1 promoter has binding sites for Egr proteins, and Egr1 is a target for Dmp1. Crosstalks between p53 and PTEN have been reported. The Egr1-Dmp1-Arf-p53-Pten pathway displays multiple modes of interaction with each other, suggesting the existence of a functional network of tumor suppressors that maintain normal cell growth and prevent the emergence of incipient cancer cells.

TERT promoter mutation subtypes and survival in stage I and II melanoma patients

Mutations within the promoter of gene encoding telomerase reverse transcriptase subunit are frequent in many cancers including melanoma. Previously, the TERT promoter mutations were shown to associate with markers of poor outcome and reduced survival in patients with primary melanoma. In this study, we investigated the impact of the subtypes of TERT mutations on disease-free and melanoma-specific survival in 287 patients with stage I/II nonacral melanoma. Our results showed that of the three TERT promoter mutation subtypes, in multivariate models, the -138/-139 CC > TT tandem mutation associated with worst disease-free and melanoma-specific survival. In particular, in combination with BRAF/NRAS mutations, the -138/-139 CC > TT TERT promoter mutation associated with statistically significant poor disease-free and melanoma-specific survival with hazard ratios of 6.04 (95% CI 2.03-17.94, p = 0.001) and 12.59 (95% CI 2.18-72.70, p = 0.005), respectively. In contrast to the survival data, luciferase assays showed that the highest activity was observed in experiments with a promoter construct with -124 C > T mutation followed by the -138/-139 CC > TT and -146 C > T mutations, which showed similar activity. Based on previous reports, we speculate that the tandem mutation probably leads to greater genomic instability than the common TERT promoter mutations, hence the association with worst survival. However, the results from the study are only preliminary with limited patient data, therefore, require a cautious interpretation. The observations in this study, if confirmed, could have implications for melanoma patients treated with MAP-kinase inhibitors.

The World of Melanoma: Epidemiologic, Genetic, and Anatomic Differences of Melanoma Across the Globe

PURPOSE OF REVIEW

As cancer remains an increasing problem in industrial countries, the incidence of melanoma has risen rapidly in many populations during the last decades and still continues to rise. Current strategies aiming to control the disease have largely focused on improving the understanding of the interplay of causal factors for this cancer.

RECENT FINDINGS

Cutaneous melanoma shows clear differences in incidence, mortality, genomic profile, and anatomic presentation, depending on the country of residence, ethnicity, and socioeconomic status. Known risk factors are multiple atypical nevi, positive family and/or personal history, immune suppressive diseases or treatments, and fair skin phenotype. Besides new adjuvant therapeutic options, changed attitude toward leisure and sun exposure, primary prevention, and early detection are major contributors to disease control. Melanoma is a disease of multifactorial causality and heterogeneous presentation. Its subtypes differ in origin, anatomical site, role of UV radiation, and mutational profile. Better understanding of these differences may improve prevention strategies and therapeutic developments.

Melanoma: What do all the mutations mean?

Melanoma is one of the most highly mutated malignancies, largely as a function of its generation through ultraviolet light and other mutational processes. The wide array of mutations in both "driver" and "passenger" genes can present a confusing array of data for practitioners, particularly within the context of the recent revolutions in targeted and immune therapy. Although mutations in BRAF V600 clearly confer sensitivity to BRAF and mitogen-activated protein kinase kinase (MEK) inhibitors, the clinical implications of most other mutations are less often discussed and understood. In this review, we provide an overview of the high-frequency genomic alterations and their prognostic and therapeutic relevance in melanoma.

Ectopic expression of the osteogenic master gene RUNX2 in melanoma Maria Teresa Valenti, Luca Dalle Carbonare, Monica Mottes

The transcription factor RUNX2 is the osteogenic master gene expressed in mesenchymal stem cells during osteogenic commitment as well as in pre-osteoblasts and early osteoblasts. However, RUNX2 is also ectopically expressed in melanoma and other cancers. Malignant melanoma (MM) is a highly metastatic skin cancer. The incidence of MM has increased considerably in the past half-century. The expression levels and mutation rates of genes such as BRAF, KIT, NRAS, PTEN, P53, TERT and MITF are higher in melanoma than in other solid malignancies. Additionally, transcription factors can affect cellular processes and induce cellular transformation since they control gene expression. Recently, several studies have identified alterations in RUNX2 expression. In particular, the regulation of KIT by RUNX2 and the increased expression of RUNX2 in melanoma specimens have been shown. Melanocytes, whose transformation results in melanoma, arise from the neural crest and therefore show “stemness” features. RUNX2 plays an important role in the re-activation of the MAPK and PI3K/AKT pathways, thus endowing melanoma cells with a high metastatic potential. In melanoma, the most frequent metastatic sites are the lung, liver, brain and lymph nodes. In addition, bone metastatic melanoma has been described. Notably, studies focusing on RUNX2 may contribute to the identification of an appropriate oncotarget in melanoma.

Genetic Alterations in Primary Acral Melanoma and Acral Melanocytic Nevus in Korea: Common Mutated Genes Show Distinct Cytomorphological Features

Acral melanoma occurring on the palms, soles, and nails is the most common subtype of cutaneous melanoma in Asians. Genetic alterations in acral melanoma and acral melanocytic nevus are not well known. We performed next-generation sequencing and evaluated the correlations between genetic information and the clinicopathologic characteristics from 85 Korean patients with acral melanocytic neoplasms. Of the 64 patients with acral melanoma, most had lesions at the T2 stage or higher, and the heel was the most common anatomical site of melanoma (n = 34 [53.1%]). The five most common mutations were BRAF (22 [34.4%]), NRAS (14, [21.9%]), NF1 (11, [17.2%]), GNAQ (12, [17.2%]), and KIT (7, [10.9%]). In the 21 acral melanocytic nevi, those five gene mutations were also common. Copy number variations were also frequently detected in 75% of acral melanomas and 47.6% of acral melanocytic nevi, and amplification was more common than deletion in both lesions. BRAF mutation was associated with round epithelioid cells and NRAS and NF1 mutations with bizarre cells. NF1 and GNAQ mutations showed elongated and spindle cells with prominent dendrites in acral melanomas. KIT mutations were common in amelanotic acral melanoma. This study suggests that common mutated genes are associated with distinct cytomorphological features in acral melanocytic lesions.

Unraveling the human protein atlas of metastatic melanoma in the course of ultraviolet radiation-derived photo-therapy

To explore the photo-therapeutic capacity of UV radiation in solid tumors, we herein employed an nLC-MS/MS technology to profile the proteomic landscape of irradiated WM-266-4 human metastatic-melanoma cells. Obtained data resulted in proteomic catalogues of 5982 and 7280 proteins for UVB- and UVC-radiation conditions, respectively, and indicated the ability of UVB/C-radiation forms to eliminate metastatic-melanoma cells through induction of synergistically operating programs of apoptosis and necroptosis. However, it seems that one or more WM-266-4 cell sub-populations may escape from UV-radiation's photo-damaging activity, acquiring, besides apoptosis tolerance, an EMT phenotype that likely offers them the advantage of developing resistance to certain chemotherapeutic drugs. Low levels of autophagy may also critically contribute to the selective survival and growth of UV-irradiated melanoma-cell escapers. These are the cells that must be systemically targeted with novel therapeutic schemes, like the one of UV radiation and Irinotecan herein suggested to be holding strong promise for the effective treatment of metastatic-melanoma patients. Given the dual nature of UV radiation to serve as both anti-tumorigenic and tumorigenic agent, all individuals being subjected to risk factors for melanoma development have to be appropriately informed and educated, in order to integrate the innovative PPPM concept in their healthcare-sector management.

SIGNIFICANCE

This study reports the application of nLC-MS/MS technology to deeply map the proteomic landscape of UV-irradiated human metastatic-melanoma cells. Data bioinformatics processing led to molecular-network reconstructions that unearthed the dual nature of UV radiation to serve as both anti-tumorigenic and tumorigenic factor in metastatic-melanoma cellular environments. Our UV radiation-derived "photo-proteomic" atlas may prove valuable for the identification of new biomarkers and development of novel therapies for the disease. Given that UV radiation represents a major risk factor causing melanoma, a PPPM-based life style and clinical practice must be embraced by all individuals being prone to disease's appearance and expansion.