Nevus senescence

Validity of Xiphophorus fish as models for human disease

Platyfish and swordtails of the genus Xiphophorus provide a well-established model for melanoma research and have become well known for this feature. Recently, modelling approaches for other human diseases in Xiphophorus have been developed or are emerging. This Review provides a comprehensive summary of these models and discusses how findings from basic biological and molecular studies and their translation to medical research demonstrate that Xiphophorus models have face, construct and predictive validity for studying a broad array of human diseases. These models can thus improve our understanding of disease mechanisms to benefit patients.

The long-term evolution of melanocytic nevi among high-risk adults

BACKGROUND

There is little understanding regarding the long-term natural history of melanocytic nevi among adults.

OBJECTIVE

The objective of the study was to describe the long-term natural history of individual nevi located on the torso of high-risk patients.

METHODS

All patients attending Memorial Sloan Kettering Cancer Center (MSKCC) who underwent two total body photography (TBP) sessions 15+ years apart were included ('retrospective' group). To account for a potential selection bias, we also included consecutive patients who had TBP 15+ years ago and consented to undergo follow-up TBP ('prospective' group). We compared baseline and follow-up torso images on the TBPs and evaluated the number of total, new and disappearing nevi; number of seborrheic keratoses and actinic keratoses; each nevus' diameter at both time points; each nevus' colour change; the presence of clinical atypia; and when dermoscopy was available, the dermoscopic features at each time point.

RESULTS

One hundred six patients were included in the study. Although the average age of the patients was 40 at baseline TBP, most patients developed new nevi between imaging sessions (median 16.4 years) with an average of 2.6 (SD = 4.8) nevi per participant. The average number of disappearing nevi was 0.3 (SD = 0.6). In addition, 62/106 (58%) patients had an absolute increase, and 9/106 (8%) patients had an absolute decrease in their total nevus count. Roughly half (49%: 1416/2890) of the nevi that could be evaluated at both time points increased in diameter by at least 25%. Only 6% (159/2890) of nevi shrunk in diameter by at least 25%. Patients with a history of melanoma had a higher rate of disappearing nevi, and their nevi were more likely to grow. Most nevi demonstrated no significant dermoscopic changes.

CONCLUSIONS

High-risk patients acquire new nevi throughout life with very few nevi disappearing over time. Contrary to prior reports, most nevi in adults increase in diameter, while few nevi shrink.

The spatiotemporal expression of NRAS and occurrence of giant congenital melanocytic nevi

The mechanism underlying giant congenital melanocytic nevus (GCMN) formation is not fully understood. According to recent research, NRAS gene mutation is the main driving factor in GCMN. Melanocytic precursor cells proliferate during the embryonic stage after acquiring NRAS mutations. However, why GCMN undergoes intense proliferation in the embryonic stage and then stops postnatally remains unknown. The current theory for this phenomenon is that the GCMN undergoes oncogene-induced senescence. However, there is not enough evidence to indicate that senescence induces growth arrest in GCMN. In this study, we hypothesized that the expression level of the NRAS gene changes dynamically during the development and differentiation of neural crest cells into melanocytes and that the NRAS expression level determines whether the cell proliferates or becomes quiescent.

Stem cell spreading dynamics intrinsically differentiate acral melanomas from nevi

Early differential diagnosis between malignant and benign tumors and their underlying intrinsic differences are the most critical issues for life-threatening cancers. To study whether human acral melanomas, deadly cancers that occur on non-hair-bearing skin, have distinct origins that underlie their invasive capability, we develop fate-tracing technologies of melanocyte stem cells in sweat glands (glandular McSCs) and in melanoma models in mice and compare the cellular dynamics with human melanoma. Herein, we report that glandular McSCs self-renew to expand their migratory progeny in response to genotoxic stress and trauma to generate invasive melanomas in mice that mimic human acral melanomas. The analysis of melanocytic lesions in human volar skin reveals that genetically unstable McSCs expand in sweat glands and in the surrounding epidermis in melanomas but not in nevi. The detection of such cell spreading dynamics provides an innovative method for an early differential diagnosis of acral melanomas from nevi.

The WHO 2018 Classification of Cutaneous Melanocytic Neoplasms: Suggestions From Routine Practice

The "multidimensional" World Health Organization (WHO) classification 2018 of melanocytic tumors encompasses nine melanoma pathways (seven of which for cutaneous melanoma) according to a progression model in which morphologically intermediate melanocytic tumors are cosidered as simulators and/or precursors to melanoma. These "intermediates" can be subclassified into: i) a "classical" subgroup (superficial/thin compound: dysplastic nevus), which is placed within the morphologic and molecular progression spectrum of classical (Clark's and McGovern's) melanoma subtypes (superficial spreading and, possibly, nodular); and ii) a "non-classical" subgroup (thick compound/dermal: "melanocytomas") whose genetic pathways diverge from classical melanoma subtypes. Such a progression model is aimed at giving a conceptual framework for a histopathological classification; however, routine clinicopathological practice strongly suggests that most melanomas arise de novo and that the vast majority of nevi are clinically stable or even involuting over time. Clinicopathological correlation can help identify some severely atypical but benign tumors (e.g.: sclerosing nevus with pseudomelanomatous features) as well as some deceptively bland melanomas (e.g.: lentiginous melanoma; nested melanoma), thereby addressing some ambiguous cases to a correct clinical management. The recently available adjuvant therapy regimens for melanoma raise the problem of a careful distinction between severely atypical (high grade) melanocytoma and "classical" melanoma: conventional morphology can guide an algorithmic approach based on an antibody panel (anti-mutated BRAF, BAP1, PRAME, ALK, TRKA, MET, HRAS-WT, ROS; beta catenin; R1alpha; p16; HMB45; Ki67), a first-line molecular study (identification of hot spot mutations of BRAF and NRAS) and an advanced molecular study (sequencing of NF1, KIT, BRAF, MAP2K1, GNAQ, GNA11, PLCB4, CYSLTR2, HRAS; fusions studies of BRAF, RET, MAP3K8, PRKCA); as a final step, next-generation sequencing can identify melanocytic tumors with rare genetic signatures and melanocytic tumors with a high tumor mutation burden which should be definitely ascribed to the category of classical melanoma with the respective therapeutic options.

A Review of Key Biological and Molecular Events Underpinning Transformation of Melanocytes to Primary and Metastatic Melanoma

Melanoma is a major public health concern that is responsible for significant morbidity and mortality, particularly in countries such as New Zealand and Australia where it is the commonest cause of cancer death in young adults. Until recently, there were no effective drug therapies for patients with advanced melanoma however significant advances in our understanding of the biological and molecular basis of melanoma in recent decades have led to the development of revolutionary treatments, including targeted molecular therapy and immunotherapy. This review summarizes our current understanding of the key events in the pathway of melanomagenesis and discusses the role of genomic analysis as a potential tool for improved diagnostic evaluation, prognostication and treatment strategies. Ultimately, it is hoped that a continued deeper understanding of the mechanisms of melanomagenesis will lead to the development of even more effective treatments that continue to provide better outcomes for patients with melanoma.

Treatment of melanoma with selected inhibitors of signaling kinases effectively reduces proliferation and induces expression of cell cycle inhibitors

Cancer treatment often tends to involve direct targeting enzymes essential for the growth and proliferation of cancer cells. The aim of this study was the recognition of the possible role of selected protein kinases: PI3K, ERK1/2, and mTOR in cell proliferation and cell cycle in malignant melanoma. We investigated the role of protein kinase inhibitors: U0126 (ERK1/2), LY294002 (PI3K), rapamycin (mTOR), everolimus (mTOR), GDC-0879 (B-RAF), and CHIR-99021 (GSK3beta) in cell proliferation and expression of crucial regulatory cell cycle proteins in human melanoma cells: WM793 (VGP) and Lu1205 (metastatic). They were used either individually or in various combinations. The study on the effect of signaling kinases inhibitors on proliferation—BrdU ELISA test after 48–72 h. Their effect on the expression of cell cycle regulatory proteins: cyclin D1 and D3, cyclin-dependent kinase CDK4 and CDK6, and cell cycle inhibitors: p16, p21, and p27, was studied at the protein level (western blot). Treatment of melanoma cells with protein kinase inhibitors led to significantly decreased cell proliferation except the use of a GSK-3β kinase inhibitors—CHIR-99021. The significant decrease in the expression of selected cyclins and cyclin-dependent kinases (CDKs) with parallel increase in the expression of some of cyclin-dependent kinases inhibitors and in consequence meaningful reduction in melanoma cell proliferation by the combinations of inhibitors of signaling kinases clearly showed the crucial role of AKT, ERK 1/2, and mTOR signal transduction in melanoma progression. The results unanimously indicate those pathways as an important target for treatment of melanoma.

UV radiation promotes melanoma dissemination mediated by the sequential reaction axis of cathepsins-TGF-β1-FAP-α

BACKGROUND

Ultraviolet radiation (UVR) is the major risk factor for development of malignant melanoma. Fibroblast activation protein (FAP)-α is a serine protease expressed on the surface of activated fibroblasts, promoting tumour invasion through extracellular matrix (ECM) degradation. The signalling mechanism behind the upregulation of FAP-α is not yet completely revealed.

METHODS

Expression of FAP-α was analysed after UVR exposure in in vitro co-culture systems, gene expression arrays and artificial skin constructs. Cell migration and invasion was studied in relation to cathepsin activity and secretion of transforming growth factor (TGF)-β1.

RESULTS

Fibroblast activation protein-α expression was induced by UVR in melanocytes of human skin. The FAP-α expression was regulated by UVR-induced release of TGF-β1 and cathepsin inhibitors prevented such secretion. In melanoma cell culture models and in a xenograft tumour model of zebrafish embryos, FAP-α mediated ECM degradation and facilitated tumour cell dissemination.

CONCLUSIONS

Our results provide evidence for a sequential reaction axis from UVR via cathepsins, TGF-β1 and FAP-α expression, promoting cancer cell dissemination and melanoma metastatic spread.

Senescence-Like Phenotypes in Human Nevi

Cellular senescence is an irreversible arrest of cell proliferation at the G1 stage of the cell cycle in which cells become refractory to growth stimuli. Senescence is a critical and potent defense mechanism that mammalian cells use to suppress tumors. While there are many ways to induce a senescence response, oncogene-induced senescence (OIS) remains the key to inhibiting progression of cells that have acquired oncogenic mutations. In primary cells in culture, OIS induces a set of measurable phenotypic and behavioral changes, in addition to cell cycle exit. Senescence-associated β-Galactosidase (SA-β-Gal) activity is a main hallmark of senescent cells, along with morphological changes that may depend on the oncogene that is activated, or on the primary cell type. Characteristic cellular changes of senescence include increased size, flattening, multinucleation, and extensive vacuolation. At the molecular level, tumor suppressor genes such as p53 and p16 ^INK4A may play a role in initiation or maintenance of OIS. Activation of a DNA damage response and a senescence-associated secretory phenotype could delineate the onset of senescence. Despite advances in our understanding of how OIS suppresses some tumor types, the in vivo role of OIS in melanocytic nevi and melanoma remains poorly understood and not validated. In an effort to stimulate research in this field, we review in this chapter the known markers of senescence and provide experimental protocols for their identification by immunofluorescent staining in melanocytic nevi and malignant melanoma.

Recurrence of Dysplastic Nevi Is Strongly Associated with Extension of the Lesions to the Lateral Margins and into the Deep Margins through the Hair Follicles in the Original Shave Removal Specimens

Melanocytic nevi, including dysplastic or atypical nevi (DN), can recur or persist following shave removal procedures, and recurrence may resemble melanoma, both clinically and histologically (pseudomelanoma). Recurrence may originate from proliferation of the remaining neoplastic melanocytes following incomplete removal. The present study determines the rate and etiology of this event. A cross-sectional analysis of 110 excision specimens showing histological recurrence was performed, and these specimens were compared to the slides of the original shave specimens showing mildly atypical DN. In the second portion of the study, a retrospective review of 167 cases with biopsy-proven mildly atypical DN which were followed up for at least two years was conducted to determine the rate of recurrence/persistence. When followed up for two years, DN, with positive shave margins, defined by extension or very close extension (≤0.2 mm) of the lesions to the lateral margins and into the deep margins through the hair follicles in the shave removal specimens, have a higher probability of recurrence than DN with negative (or clear) margins (odds ratio (OR) = 158; 95% confidence interval (CI) = 36.62–683; P < 0.001). The overall rate of histologically confirmed recurrence/persistence was approximately 10%.

Comparison of telomere length and insulin-like growth factor-binding protein 7 promoter methylation between breast cancer tissues and adjacent normal tissues in Turkish women

BACKGROUND

Both insulin-like growth factor-binding protein 7 (IGFBP7) and telomere length (TL) are associated with proliferation and senescence of human breast cancer. This study assessed the clinical significance of both TL and IGFBP7 methylation status in breast cancer tissues compared with adjacent normal tissues. We also investigated whether IGFBP7 methylation status could be affecting TL.

METHODS

Telomere length was measured by quantitative PCR to compare tumors with their adjacent normal tissues. The IGFBP7 promoter methylation status was evaluated by methylation-specific PCR and its expression levels were determined by western blotting.

RESULTS

Telomeres were shorter in tumor tissues compared to controls (P<.0001). The mean TL was higher in breast cancer with invasive ductal carcinoma (IDC; n=72; P=.014) compared with other histological type (n=29), and TL in IDC with HER2 negative (n=53; P=.017) was higher than TL in IDC with HER2 positive (n=19). However, telomeres were shortened in advanced stages and growing tumors. IGFBP7 methylation was observed in 90% of tumor tissues and 59% of controls (P=.0002). Its frequency was significantly higher in IDC compared with invasive mixed carcinoma (IMC; P=.002) and it was not correlated either with protein expression or the other clinicopathological parameters.

CONCLUSION

These results suggest that IGFBP7 promoter methylation and shorter TL in tumor compared with adjacent tissues may be predictive biomarkers for breast cancer. Telomere maintenance may be indicative of IDC and IDC with HER2 (-) of breast cancer. Further studies with larger number of cases are necessary to verify this association.

Growth-Curve Modeling of Nevi With a Peripheral Globular Pattern

Importance

Although nevi with a peripheral rim of globules (peripheral globular nevi [PGN]) observed with dermoscopy are associated with enlarging melanocytic nevi, their actual growth dynamics remain unknown. Because change is a sensitive but nonspecific marker for melanoma, beginning to understand the growth patterns of nevi may improve the ability of physicians to differentiate normal from abnormal growth and reduce unnecessary biopsies.

Objective

To study the growth dynamics and morphologic evolution of PGN on dermoscopy.

Design, Setting, and Participants

A total of 84 participants with 121 PGN from September 1, 1999, through May 1, 2013, were identified retrospectively. Cohorts were recruited from the Memorial Sloan Kettering Cancer Center; Melanoma Unit of the Hospital Clinic, University of Barcelona; and Study of Nevi in Children. All 3 cohorts underwent longitudinal monitoring with serial dermoscopic imaging of their PGN. Data analysis was performed from May 1, 2014, through April 1, 2015.

Main Outcomes and Measures

Establishment of the natural growth curve of PGN. The secondary aim was to establish the median time to growth cessation in those PGN for which the size eventually stabilized and/or had begun to decrease during the study period.

Results

The median duration of follow-up was 25.1 (range, 2.0-114.4) months. Most of the nevi (116 [95.9%]) enlarged at some point during sequential monitoring. The rate of increase in the surface area of PGN varied among cohorts and ranged from -0.47 to 2.26 mm2/mo (mean rate, 0.25 [95% CI, 0.14-0.36] mm2/mo). The median time to growth cessation in the 26 PGN that stabilized or decreased in size (21.5%) was 58.6 months. All lesions changed in a symmetric manner and 91 (75.2%) displayed a decrease in the density of peripheral globules over time.

Conclusions and Relevance

Nevi displaying a peripheral globular pattern enlarged symmetrically with apparent growth cessation occurring during a span of 4 to 5 years. Our results reiterate the important concept that not all growth is associated with malignancy.

Conceptual approach to early melanoma detection: models, tools, issues and challenges

Identification and removal of melanoma early in its development remains the most effective treatment. However, identification of early melanoma remains challenging and may result in unnecessary morbidity due to the excess excision of benign melanocytic nevi. Herein, we present a conceptual model of benign and malignant melanocytic growths. The potential differences in the location of the cell of origin as well as considerations for neoplasm progression are also reviewed. Several of the clinical tools currently available, the integration of information from those different sources, and approaches to set an optimum biopsy threshold are discussed. While early detection remains a challenge, significant progress has been made. Insight into melanoma growth processes and appropriate use of available tools can result in the detection of thinner melanomas while also decreasing overall biopsy rates.

Therapy for BRAFi-Resistant Melanomas: Is WNT5A the Answer?

In recent years, scientists have advocated the use of targeted therapies in the form of drugs that modulate genes and proteins that are directly associated with cancer progression and metastasis. Malignant melanoma is a dreadful cancer type that has been associated with the rapid dissemination of primary tumors to multiple sites, including bone, brain, liver and lungs. The discovery that approximately 40%–50% of malignant melanomas contain a mutation in BRAF at codon 600 gave scientists a new approach to tackle this disease. However, clinical studies on patients have shown that although BRAFi (BRAF inhibitors) trigger early anti-tumor responses, the majority of patients later develop resistance to the therapy. Recent studies have shown that WNT5A plays a key role in enhancing the resistance of melanoma cells to BRAFi. The focus of the current review will be on melanoma development, signaling pathways important to acquired resistance to BRAFi, and why WNT5A inhibitors are attractive candidates to be included in combinatorial therapies for melanoma.

A murine model for the development of melanocytic nevi and their progression to melanoma

Acquired melanocytic nevi are commonly found in sun exposed and unexposed human skin, but the potential for their transformation into invasive melanoma is not clear. Therefore, a mouse model of nevus initiation and progression was developed in C3H/HeN mice using a modified chemical carcinogenesis protocol. Nevi develop due to DNA damage initiated by dimethylbenz(a) anthracene (DMBA) followed by chronic promotion with 12‐O‐tetradecanoyl‐phorbol‐13‐acetate (TPA). Dysplastic pigmented skin lesions appeared in 7–9 wk with 100% penetrance. Nests of melanocytic cells appeared in a subset of skin draining lymph nodes (dLN) by 25 wk, but not in age matched controls. Immunohistochemistry, real‐time PCR, and flow cytometric analyses confirmed their melanocytic origin. Transformed cells were present in a subset of nevi and dLNs, which exhibited anchorage‐independent growth, tumor development, and metastasis in nude mice. Approximately 50% of the cell lines contained H‐Ras mutations and lost tumor suppressor p16^Ink4a expression. While most studies of melanoma focus on tumor progression in transgenic mouse models where the mutations are present from birth, our model permits investigation of acquired mutations at the earliest stages of nevus initiation and promotion of nevus cell transformation. This robust nevus/melanoma model may prove useful for identifying genetic loci associated with nevus formation, novel oncogenic pathways, tumor targets for immune‐prevention, screening therapeutics, and elucidating mechanisms of immune surveillance and immune evasion. © 2015 The Authors. Molecular Carcinogenesis, published by Wiley Periodicals, Inc.