Molecular characterization of fast-growing melanomas.

BACKGROUND: The rate of growth of primary melanoma is a robust predictor of aggressiveness, but the mutational profile of fast-growing melanomas (FGMM) and the potential to stratify patients at high risk of death has not been comprehensively studied. OBJECTIVE: To investigate the epidemiologic, clinical, and mutational profile of primary cutaneous melanomas with a thickness ≥ 1 mm, stratified by rate of growth. METHODS: Observational prospective study. Deep-targeted sequencing of 40 melanoma driver genes on formalin fixed, paraffin-embedded primary melanoma samples. Comparison of FGMM (rate of growth > 0.5 mm/month) and nonFGMM (rate of growth ≤ 0.5 mm/month). RESULTS: Two hundred patients were enrolled, among wom 70 had FGMM. The relapse-free survival was lower in the FGMM group (P = .014). FGMM had a higher number of predicted deleterious mutations within the 40 genes than nonFGMM (P = .033). Ulceration (P = .032), thickness (P = .006), lower sun exposure (P = .049), and fibroblast growth factor receptor 2 (FGFR2) mutations (P = .037) were significantly associated with fast growth. LIMITATIONS: Single-center study, cohort size, potential memory bias, number of investigated genes. CONCLUSION: Fast growth is linked to specific tumor biology and environmental factors. Ulceration, thickness, and FGFR2 mutations are associated with fast growth. Screening for FGFR2 mutations might provide an additional tool to better identify FGMM, which are probably good candidates for adjuvant therapies.

Ultraviolet radiation accelerates BRAF-driven melanomagenesis by targeting TP53.

Cutaneous melanoma is epidemiologically linked to ultraviolet radiation (UVR), but the molecular mechanisms by which UVR drives melanomagenesis remain unclear. The most common somatic mutation in melanoma is a V600E substitution in BRAF, which is an early event. To investigate how UVR accelerates oncogenic BRAF-driven melanomagenesis, we used a BRAF(V600E) mouse model. In mice expressing BRAF(V600E) in their melanocytes, a single dose of UVR that mimicked mild sunburn in humans induced clonal expansion of the melanocytes, and repeated doses of UVR increased melanoma burden. Here we show that sunscreen (UVA superior, UVB sun protection factor (SPF) 50) delayed the onset of UVR-driven melanoma, but only provided partial protection. The UVR-exposed tumours showed increased numbers of single nucleotide variants and we observed mutations (H39Y, S124F, R245C, R270C, C272G) in the Trp53 tumour suppressor in approximately 40% of cases. TP53 is an accepted UVR target in human non-melanoma skin cancer, but is not thought to have a major role in melanoma. However, we show that, in mice, mutant Trp53 accelerated BRAF(V600E)-driven melanomagenesis, and that TP53 mutations are linked to evidence of UVR-induced DNA damage in human melanoma. Thus, we provide mechanistic insight into epidemiological data linking UVR to acquired naevi in humans. Furthermore, we identify TP53/Trp53 as a UVR-target gene that cooperates with BRAF(V600E) to induce melanoma, providing molecular insight into how UVR accelerates melanomagenesis. Our study validates public health campaigns that promote sunscreen protection for individuals at risk of melanoma.

Ultraviolet light and melanoma.

Melanoma is a clinically heterogeneous disease, and current strategies for treatment of the primary tumour are based on pathological criteria alone. In the recent past, several DNA-sequencing and RNA-sequencing studies of primary and advanced melanoma samples have identified unique relationships between somatic mutations, genomic aberrations, and the genetic fingerprint of ultraviolet radiation (UVR). The recurrent patterns of genomic alterations reveal different disease pathways, drug targets and mechanisms limiting drug response. Here, we examine the known associations between the molecular categories of melanoma and the multidimensional UVR damage. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Mechanisms of Drug Resistance in Melanoma.

Metastatic melanoma is associated with poor outcome and is largely refractory to the historic standard of care. In recent years, the development of targeted small-molecule inhibitors and immunotherapy has revolutionised the care and improved the overall survival of these patients. Therapies targeting BRAF and MEK to block the mitogen-activated protein kinase (MAPK) pathway were the first to show unprecedented clinical responses. Following these encouraging results, antibodies targeting immune checkpoint inhibition molecules cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), programmed cell death (PD)-1, and PD-ligand1(PD-L1) demonstrated sustained tumour regression in a significant subset of patients by enabling an anti-tumour immunologic response. Despite these landmark changes in practice, the majority of patients are either intrinsically resistant or rapidly acquire resistance to MAPK pathway inhibitors and immune checkpoint blockade treatment. The lack of response can be driven by mutations and non-mutational events in tumour cells, as well as by changes in the surrounding tumour microenvironment. Common resistance mechanisms bypass the dependence of tumour cells on initial MAPK pathway driver mutations during targeted therapy, and permit evasion of the host immune system to allow melanoma growth and survival following immunotherapy. This highlights the requirement for personalised treatment regimens that take into account patient-specific genetic and immunologic characteristics. Here we review the mechanisms by which melanomas display intrinsic resistance or acquire resistance to targeted therapy and immunotherapy.

New insights into naevoid melanomas: a clinicopathological reassessment.

AIMS: Because the term 'naevoid melanoma' has variable clinical and pathological interpretations, we aimed to clarify the features of melanomas referred to as naevoid. METHODS AND RESULTS: A review was undertaken of 102 melanomas diagnosed histopathologically as naevoid melanomas and ascertained by European Organization for Research and Treatment of Cancer Melanoma Group Subcommittee pathologists from their records. We found these could be classified morphologically into three groups. Thirteen melanomas were overlying genuine naevi and were therefore excluded. Of the 89 melanomas considered to be naevoid, 11 presented clinically as exophytic papillomatous nodules with little junctional component and composed of small atypical cells showing numerous mitoses and no change with depth; we termed these 'papillomatous naevoid' melanomas. The other 78 were flat or only slightly raised, and had a superficial spreading melanoma-like component with maturation to a small cell, but still an atypical, dermal component; we termed these 'maturing naevoid' melanomas. We showed that papillomatous and maturing naevoid melanomas also have differing immunochemical profiles. Preliminary clinical follow-up suggested different outcomes for these two naevoid melanoma types. CONCLUSIONS: Melanomas that have been classified as naevoid melanomas comprise two types with distinct clinical, histopathological and immunohistochemical features that may also be prognostically significant.

RAS mutations in cutaneous squamous-cell carcinomas in patients treated with BRAF inhibitors.

BACKGROUND: Cutaneous squamous-cell carcinomas and keratoacanthomas are common findings in patients treated with BRAF inhibitors. METHODS: We performed a molecular analysis to identify oncogenic mutations (HRAS, KRAS, NRAS, CDKN2A, and TP53) in the lesions from patients treated with the BRAF inhibitor vemurafenib. An analysis of an independent validation set and functional studies with BRAF inhibitors in the presence of the prevalent RAS mutation was also performed. RESULTS: Among 21 tumor samples, 13 had RAS mutations (12 in HRAS). In a validation set of 14 samples, 8 had RAS mutations (4 in HRAS). Thus, 60% (21 of 35) of the specimens harbored RAS mutations, the most prevalent being HRAS Q61L. Increased proliferation of HRAS Q61L-mutant cell lines exposed to vemurafenib was associated with mitogen-activated protein kinase (MAPK)-pathway signaling and activation of ERK-mediated transcription. In a mouse model of HRAS Q61L-mediated skin carcinogenesis, the vemurafenib analogue PLX4720 was not an initiator or a promoter of carcinogenesis but accelerated growth of the lesions harboring HRAS mutations, and this growth was blocked by concomitant treatment with a MEK inhibitor. CONCLUSIONS: Mutations in RAS, particularly HRAS, are frequent in cutaneous squamous-cell carcinomas and keratoacanthomas that develop in patients treated with vemurafenib. The molecular mechanism is consistent with the paradoxical activation of MAPK signaling and leads to accelerated growth of these lesions. (Funded by Hoffmann-La Roche and others; ClinicalTrials.gov numbers, NCT00405587, NCT00949702, NCT01001299, and NCT01006980.).

Clinical, histological, and molecular differences in melanoma due to different TERT promoter mutations subtypes. A retrospective cross-sectional study in 684 melanoma patients.

Differences in survival according to the pTERT mutation subtypes (-124C > T, -146C > T, and tandem -138_139CC > TT) have been observed. The present study aimed to describe the clinical as the histopathological and molecular cutaneous melanoma features according to the presence of the three most prevalent pTERT mutation subtypes (-124C > T, -146C > T, and tandem -138_139CC > TT). A retrospective cross-sectional study including 684 patients was designed, and a Partial Least-Squares Discriminant Analysis (PLS-DA) was performed. After the PSL-DA, it was observed that the tandem -138_139CC > TT subtype differs from the other subtypes. The model demonstrated that the -124C > T and the -138_139 CC > TT subtypes were associated with fast-growing melanomas (OR 0.5, CI 0.29-0.86, p = .012) and with Breslow >2 mm (OR 0.6, CI 0.37-0.97, p = .037), compared to the -146C > T mutation. Finally, the -124C > T appeared to be more associated with the presence of TILs (non-brisk) than the -146C > T (OR 0.6, CI 0.40-1.01, p = .05). These findings confirmed that the -124C > T and the tandem -138_139 CC > TT subtypes are both highly associated with the presence of features of aggressiveness; however, only the -124C > T was highly associated with TILs. This difference could explain the worse survival rate associated with the tandem -138_139CC > TT mutations.

Positive Attributes of Anti-TERT CD4 T-Helper Type 1 Immune Responses in Melanoma.

Nardin et al's (2021) study on melanoma reports anti-TERT CD4 T helper type (Th) 1 responses in more than half of patients. Besides indicating a trend for improved survival, increased anti-TERT CD4 Th1 responses predicted better outcomes for patients treated with immune checkpoint inhibitors. Thus, harnessing systemic anti-TERT CD4 Th1 responses together with tumor-specific elevation of telomerase can potentially open new avenues for biomarkers and treatment in melanoma.

3D Bioprinting: An Enabling Technology to Understand Melanoma.

Melanoma is a potentially fatal cancer with rising incidence over the last 50 years, associated with enhanced sun exposure and ultraviolet radiation. Its incidence is highest in people of European descent and the ageing population. There are multiple clinical and epidemiological variables affecting melanoma incidence and mortality, such as sex, ethnicity, UV exposure, anatomic site, and age. Although survival has improved in recent years due to advances in targeted and immunotherapies, new understanding of melanoma biology and disease progression is vital to improving clinical outcomes. Efforts to develop three-dimensional human skin equivalent models using biofabrication techniques, such as bioprinting, promise to deliver a better understanding of the complexity of melanoma and associated risk factors. These 3D skin models can be used as a platform for patient specific models and testing therapeutics.

Mutational Characterization of Cutaneous Melanoma Supports Divergent Pathways Model for Melanoma Development.

According to the divergent pathway model, cutaneous melanoma comprises a nevogenic group with a propensity to melanocyte proliferation and another one associated with cumulative solar damage (CSD). While characterized clinically and epidemiologically, the differences in the molecular profiles between the groups have remained primarily uninvestigated. This study has used a custom gene panel and bioinformatics tools to investigate the potential molecular differences in a thoroughly characterized cohort of 119 melanoma patients belonging to nevogenic and CSD groups. We found that the nevogenic melanomas had a restricted set of mutations, with the prominently mutated gene being BRAF. The CSD melanomas, in contrast, showed mutations in a diverse group of genes that included NF1, ROS1, GNA11, and RAC1. We thus provide evidence that nevogenic and CSD melanomas constitute different biological entities and highlight the need to explore new targeted therapies.

Distribution and clinical role of KIT gene mutations in melanoma according to subtype: a study of 492 Spanish patients.

BACKGROUND: KIT mutations are primarily associated with acral and mucosal melanoma, and have been reported to show higher prevalence in chronic sun-damaged (CSD) than non-CSD melanomas. OBJECTIVES: To investigate the prevalence of KIT mutations in melanoma according to subtype, and determine the clinical role of such mutations. MATERIALS & METHODS: We present results from a study of a Spanish population of 492 melanomas, classified according to the latest World Health Organization (WHO) guidelines. We analysed the mutational status of KIT and correlated with different clinical variables related to sun exposure and family history. RESULTS: KIT mutations were significantly more frequent in acral (3/36; 8.3%) and mucosal (4/8; 50%) melanomas than non-acral cutaneous melanomas. No significant difference was observed in KIT mutational status between CSD and non-CSD melanomas. CONCLUSION: Our results suggest that KIT mutations in melanoma tumours are unrelated to the development of nevi or chronic sun damage, but their presence is associated with aggressive melanomas which show ulceration, vascular invasiveness, and increased Breslow thickness. These findings are consistent with those reported by The Cancer Genome Atlas network.

Female Immunity Protects from Cutaneous Squamous Cell Carcinoma.

PURPOSE: Cancer susceptibility and mortality are higher in males, and the mutational and transcriptomic landscape of cancer differs by sex. The current assumption is that men are at higher risk of epithelial cancers as they expose more to carcinogens and accumulate more damage than women. We present data showing women present with less aggressive primary cutaneous squamous cell carcinoma (cSCC) and early strong immune activation. EXPERIMENTAL DESIGN: We explored clinical and molecular sexual disparity in immunocompetent and immunosuppressed patients with primary cSCC (N = 738, N = 160), advanced-stage cSCC (N = 63, N = 20) and FVB/N mice exposed to equal doses of DMBA, as well as in human keratinocytes by whole-exome, bulk, and single-cell RNA sequencing. RESULTS: We show cSCC is more aggressive in men, and immunocompetent women develop mild cSCC, later in life. To test whether sex drives disparity, we exposed male and female mice to equal doses of carcinogen, and found males present with more aggressive, metastatic cSCC than females. Critically, females activate cancer immune-related expression pathways and CD4 and CD8 T-cell infiltration independently of mutations, a response that is absent in prednisolone-treated animals. In contrast, males increase the rate of mitosis and proliferation in response to carcinogen. Women's skin and keratinocytes also activate immune-cancer fighting pathways and immune cells at UV radiation-damaged sites. Critically, a compromised immune system leads to high-risk, aggressive cSCC specifically in women. CONCLUSIONS: This work shows the immune response is sex biased in cSCC and highlights female immunity offers greater protection than male immunity.

Ultraviolet light-induced collagen degradation inhibits melanoma invasion.

Ultraviolet radiation (UVR) damages the dermis and fibroblasts; and increases melanoma incidence. Fibroblasts and their matrix contribute to cancer, so we studied how UVR modifies dermal fibroblast function, the extracellular matrix (ECM) and melanoma invasion. We confirmed UVR-damaged fibroblasts persistently upregulate collagen-cleaving matrix metalloprotein-1 (MMP1) expression, reducing local collagen (COL1A1), and COL1A1 degradation by MMP1 decreased melanoma invasion. Conversely, inhibiting ECM degradation and MMP1 expression restored melanoma invasion. Primary cutaneous melanomas of aged humans show more cancer cells invade as single cells at the invasive front of melanomas expressing and depositing more collagen, and collagen and single melanoma cell invasion are robust predictors of poor melanoma-specific survival. Thus, primary melanomas arising over collagen-degraded skin are less invasive, and reduced invasion improves survival. However, melanoma-associated fibroblasts can restore invasion by increasing collagen synthesis. Finally, high COL1A1 gene expression is a biomarker of poor outcome across a range of primary cancers.

Brain microenvironment-driven resistance to immune and targeted therapies in acral melanoma.

BACKGROUND: Combination treatments targeting the MEK-ERK pathway and checkpoint inhibitors have improved overall survival in melanoma. Resistance to treatment especially in the brain remains challenging, and rare disease subtypes such as acral melanoma are not typically included in trials. Here we present analyses from longitudinal sampling of a patient with metastatic acral melanoma that became resistant to successive immune and targeted therapies. METHODS: We performed whole-exome sequencing and RNA sequencing on an acral melanoma that progressed on successive immune (nivolumab) and targeted (dabrafenib) therapy in the brain to identify resistance mechanisms. In addition, we performed growth inhibition assays, reverse phase protein arrays and immunoblotting on patient-derived cell lines using dabrafenib in the presence or absence of cerebrospinal fluid (CSF) in vitro. Patient-derived xenografts were also developed to analyse response to dabrafenib. RESULTS: Immune escape following checkpoint blockade was not due to loss of tumour cell recognition by the immune system or low neoantigen burden, but was associated with distinct changes in the microenvironment. Similarly, resistance to targeted therapy was not associated with acquired mutations but upregulation of the AKT/phospho-inositide 3-kinase pathway in the presence of CSF. CONCLUSION: Heterogeneous tumour interactions within the brain microenvironment enable progression on immune and targeted therapies and should be targeted in salvage treatments.

Histologic Features Associated With an Invasive Component in Lentigo Maligna Lesions.

Importance: Lentigo maligna (LM) presents an invasive component in up to 20% of biopsied cases, but to date the histologic features useful in detecting this invasive component have not been described. Some histologic characteristics are hypothesized to contribute to the progression of LM invasion. Objective: To identify the histologic characteristics associated with lentigo maligna melanoma (LMM) in patients with LM diagnosed by a partial diagnostic biopsy. Design, Setting, and Participants: A retrospective cross-sectional study of patients treated between January 1, 2000, and December 31, 2017, was conducted in a referral oncology center in València, Spain. Data and specimens of patients (n = 96) with a diagnosis of primary cutaneous melanoma in the form of either LM or LMM who had undergone surgical treatment, a complete histologic examination of the whole tumor, and an initial diagnostic partial biopsy of LM were included in the study. Histologic assessment was blinded to the presence of an invasive component. Interventions: All biopsy specimens were evaluated for the presence of certain histologic characteristics. Main Outcomes and Measures: Comparisons between invasive samples and samples without an invasive component were performed. The differences in the distribution of variables between the groups were assessed using the χ2 and Fisher exact tests, and the degree of association of the relevant variables was quantified by logistic regression models. A classification and regression tree analysis was performed to rank the variables by importance. Results: In total, 96 patients had sufficient histologic material that could be evaluated. The patients were predominantly male (56 [58.3%]) and had a mean (SD) age at diagnosis of 72 (12) years. Of these patients, 63 (65.6%) had an LM diagnosis and 33 (34.4%) had an LMM diagnosis (an invasive component). The histologic variables associated with the presence of an invasive component were melanocytes forming rows (odds ratio [OR], 11.5; 95% CI, 1.4-94.1; P = .02), subepidermal clefts (OR, 2.8; 95% CI, 1.0-7.9; P = .049), nests (OR, 3.0; 95% CI, 1.1-8.6; P = .04), and a lesser degree of solar elastosis (OR, 0.4; 95% CI, 0.1-1.1; P = .07). A classification and regression tree analysis of the relevant histologic features was able to accurately identify lentigo maligna with an invasive component (LMM) in more than 60% of patients. Conclusions and Relevance: These findings may be useful in classifying early LM specimens at higher risk of invasion, which may eventually be relevant in identifying the most appropriate management for LM.

Author Correction: Lysyl oxidase drives tumour progression by trapping EGF receptors at the cell surface.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Ultraviolet radiation-induced DNA damage is prognostic for outcome in melanoma.

The melanoma genome is dominated by ultraviolet radiation (UVR)-induced mutations. Their relevance in disease progression is unknown. Here we classify melanomas by mutation signatures and identify ten recurrently mutated UVR signature genes that predict patient survival. We validate these findings in primary human melanomas; in mice we show that this signature is imprinted by short-wavelength UVR and that four exposures to UVR are sufficient to accelerate melanomagenesis.

Publisher Correction: Ultraviolet radiation-induced DNA damage is prognostic for outcome in melanoma.

In the version of this article originally published, Extended Data Fig. 3 was incorrect. A duplicate of Extended Data Fig. 4 was uploaded in place of Extended Data Fig. 3. Extended Data Fig. 3 has now been uploaded. The error has been fixed in the PDF and HTML versions of this article.

Improving melanoma classification by integrating genetic and morphologic features.

BACKGROUND: In melanoma, morphology-based classification systems have not been able to provide relevant information for selecting treatments for patients whose tumors have metastasized. The recent identification of causative genetic alterations has revealed mutations in signaling pathways that offer targets for therapy. Identifying morphologic surrogates that can identify patients whose tumors express such alterations (or functionally equivalent alterations) would be clinically useful for therapy stratification and for retrospective analysis of clinical trial data. METHODOLOGY/PRINCIPAL FINDINGS: We defined and assessed a panel of histomorphologic measures and correlated them with the mutation status of the oncogenes BRAF and NRAS in a cohort of 302 archival tissues of primary cutaneous melanomas from an academic comprehensive cancer center. Melanomas with BRAF mutations showed distinct morphological features such as increased upward migration and nest formation of intraepidermal melanocytes, thickening of the involved epidermis, and sharper demarcation to the surrounding skin; and they had larger, rounder, and more pigmented tumor cells (all p-values below 0.0001). By contrast, melanomas with NRAS mutations could not be distinguished based on these morphological features. Using simple combinations of features, BRAF mutation status could be predicted with up to 90.8% accuracy in the entire cohort as well as within the categories of the current World Health Organization (WHO) classification. Among the variables routinely recorded in cancer registries, we identified age < 55 y as the single most predictive factor of BRAF mutation in our cohort. Using age < 55 y as a surrogate for BRAF mutation in an independent cohort of 4,785 patients of the Southern German Tumor Registry, we found a significant survival benefit (p < 0.0001) for patients who, based on their age, were predicted to have BRAF mutant melanomas in 69% of the cases. This group also showed a different pattern of metastasis, more frequently involving regional lymph nodes, compared to the patients predicted to have no BRAF mutation and who more frequently displayed satellite, in-transit metastasis, and visceral metastasis (p < 0.0001). CONCLUSIONS: Refined morphological classification of primary melanomas can be used to improve existing melanoma classifications by forming subgroups that are genetically more homogeneous and likely to differ in important clinical variables such as outcome and pattern of metastasis. We expect this information to improve classification and facilitate stratification for therapy as well as retrospective analysis of existing trial data.