Integrated molecular drivers coordinate biological and clinical states in melanoma

Somatic structural variants drive distinct modes of oncogenesis in melanoma

The diversity of structural variants (SVs) in melanoma and how they impact oncogenesis are incompletely known. We performed harmonized analysis of SVs across melanoma histologic and genomic subtypes, and we identified distinct global properties between subtypes. These included the frequency and size of SVs and SV classes, their relation to chromothripsis events, and the impact on cancer-related genes of SVs that alter topologically associated domain (TAD) boundaries. Following our prior identification of double-stranded break repair deficiency in a subset of triple-wild-type cutaneous melanoma, we identified MRE11 and NBN loss-of-function SVs in melanomas with this mutational signature. Experimental knockouts of MRE11 and NBN, followed by olaparib cell viability assays in melanoma cells, indicated that dysregulation of each of these genes may cause sensitivity to PARP inhibitors in cutaneous melanomas. Broadly, harmonized analysis of melanoma SVs revealed distinct global genomic properties and molecular drivers, which may have biological and therapeutic impact.

Chromatin Remodelers Are Regulators of the Tumor Immune Microenvironment

Immune checkpoint inhibitors show remarkable responses in a wide range of cancers, yet patients develop adaptive resistance. This necessitates the identification of alternate therapies that synergize with immunotherapies. Epigenetic modifiers are potent mediators of tumor-intrinsic mechanisms and have been shown to regulate immune response genes, making them prime targets for therapeutic combinations with immune checkpoint inhibitors. Some success has been observed in early clinical studies that combined immunotherapy with agents targeting DNA methylation and histone modification; however, less is known about chromatin remodeler-targeted therapies. Here, we provide a discussion on the regulation of tumor immunogenicity by the chromatin remodeling SWI/SNF complex through multiple mechanisms associated with immunotherapy response that broadly include IFN signaling, DNA damage, mismatch repair, regulation of oncogenic programs, and polycomb-repressive complex antagonism. Context-dependent targeting of SWI/SNF subunits can elicit opportunities for synthetic lethality and reduce T-cell exhaustion. In summary, alongside the significance of SWI/SNF subunits in predicting immunotherapy outcomes, their ability to modulate the tumor immune landscape offers opportunities for therapeutic intervention.

Current and Emerging Radiotherapy Options for Uveal Melanoma

What treatment options are there for patients having uveal melanoma? A randomized, prospective, multi-institutional clinical trial (COMS) showed no difference in survival between brachytherapy and enucleation for medium-sized lesions. With the obvious benefit of retaining the eye, brachytherapy has flourished and many different approaches have been developed such as low-dose-rate sources using alternate low-energy photon-emitting radionuclides, different plaque designs and seed-loading techniques, high-dose-rate brachytherapy sources and applicators, and low- and high-dose-rate beta-emitting sources and applicators. There also have been developments of other radiation modalities like external-beam radiotherapy using linear accelerators with high-energy photons, particle accelerators for protons, and gamma stereotactic radiosurgery. This article examines the dosimetric properties, targeting capabilities, and outcomes of these approaches. The several modalities examined herein have differing attributes and it may be that no single approach would be considered optimal for all patients and all lesion characteristics.

A Fucose-Containing Sulfated Polysaccharide from Spatoglossum schröederi Potentially Targets Tumor Growth Rather Than Cytotoxicity: Distinguishing Action on Human Melanoma Cell Lines

Natural substances are strategic candidates for drug development in cancer research. Marine-derived molecules are of special interest due to their wide range of biological activities and sustainable large-scale production. Melanoma is a type of skin cancer that originates from genetic mutations in melanocytes. BRAF, RAS, and NF1 mutations are described as the major melanoma drivers, but approximately 20% of patients lack these mutations and are included in the triple wild-type (tripleWT) classification. Recent advances in targeted therapy directed at driver mutations along with immunotherapy have only partially improved patients' overall survival, and consequently, melanoma remains deadly when in advanced stages. Fucose-containing sulfated polysaccharides (FCSP) are potential candidates to treat melanoma; therefore, we investigated Fucan A, a FCSP from Spatoglossum schröederi brown seaweed, in vitro in human melanoma cell lines presenting different mutations. Up to 72 h Fucan A treatment was not cytotoxic either to normal melanocytes or melanoma cell lines. Interestingly, it was able to impair the tripleWT CHL-1 cell proliferation (57%), comparable to the chemotherapeutic cytotoxic drug cisplatin results, with the advantage of not causing cytotoxicity. Fucan A increased CHL-1 doubling time, an effect attributed to cell cycle arrest. Vascular mimicry, a close related angiogenesis process, was also impaired (73%). Fucan A mode of action could be related to gene expression modulation, in special β-catenin downregulation, a molecule with protagonist roles in important signaling pathways. Taken together, results indicate that Fucan A is a potential anticancer molecule and, therefore, deserves further investigation.

Desmosome mutations impact the tumor microenvironment to promote melanoma proliferation

Desmosomes are transmembrane protein complexes that contribute to cell-cell adhesion in epithelia and other tissues. Here, we report the discovery of frequent genetic alterations in the desmosome in human cancers, with the strongest signal seen in cutaneous melanoma where desmosomes are mutated in over 70% of cases. In primary but not metastatic melanoma biopsies, the burden of coding mutations on desmosome genes associates with a strong reduction in desmosome gene expression. Analysis by spatial transcriptomics suggests that these expression decreases occur in keratinocytes in the microenvironment rather than in primary melanoma tumor cells. In further support of a microenvironmental origin, we find that loss-of-function knockdowns of the desmosome in keratinocytes yield markedly increased proliferation of adjacent melanocytes in keratinocyte/melanocyte co-cultures. Thus, gradual accumulation of desmosome mutations in neighboring cells may prime melanocytes for neoplastic transformation.

Autoimmune alleles at the major histocompatibility locus modify melanoma susceptibility

Autoimmunity and cancer represent two different aspects of immune dysfunction. Autoimmunity is characterized by breakdowns in immune self-tolerance, while impaired immune surveillance can allow for tumorigenesis. The class I major histocompatibility complex (MHC-I), which displays derivatives of the cellular peptidome for immune surveillance by CD8+ T cells, serves as a common genetic link between these conditions. As melanoma-specific CD8+ T cells have been shown to target melanocyte-specific peptide antigens more often than melanoma-specific antigens, we investigated whether vitiligo- and psoriasis-predisposing MHC-I alleles conferred a melanoma-protective effect. In individuals with cutaneous melanoma from both The Cancer Genome Atlas (n = 451) and an independent validation set (n = 586), MHC-I autoimmune-allele carrier status was significantly associated with a later age of melanoma diagnosis. Furthermore, MHC-I autoimmune-allele carriers were significantly associated with decreased risk of developing melanoma in the Million Veteran Program (OR = 0.962, p = 0.024). Existing melanoma polygenic risk scores (PRSs) did not predict autoimmune-allele carrier status, suggesting these alleles provide orthogonal risk-relevant information. Mechanisms of autoimmune protection were neither associated with improved melanoma-driver mutation association nor improved gene-level conserved antigen presentation relative to common alleles. However, autoimmune alleles showed higher affinity relative to common alleles for particular windows of melanocyte-conserved antigens and loss of heterozygosity of autoimmune alleles caused the greatest reduction in presentation for several conserved antigens across individuals with loss of HLA alleles. Overall, this study presents evidence that MHC-I autoimmune-risk alleles modulate melanoma risk unaccounted for by current PRSs.

Gene expression networks involved in multiple cellular programs coexist in individual hepatocellular cancer cells

The gene expression networks of a single cell can be used to reveal cell type- and condition-specific patterns that account for cell states, cell identity, and its responses to environmental changes. We applied single cell sequencing datasets to define mRNA patterns and visualized potential cellular capacities among hepatocellular cancer cells. The expressing numbers and levels of genes were highly heterogenous among the cancer cells. The cellular characteristics were dependent strongly on the expressing numbers and levels of genes, especially oncogenes and anti-oncogenes, in an individual cancer cell. The transcriptional activations of oncogenes and anti-oncogenes were strongly linked to inherent multiple cellular programs, some of which oppose and contend against other processes, in a cancer cell. The gene expression networks of multiple cellular programs proliferation, differentiation, apoptosis, autophagy, epithelial-mesenchymal transition, ATP production, and neurogenesis coexisted in an individual cancer cell. The findings give rise a hypothesis that a cancer cell expresses balanced combinations of genes and undergoes a given biological process by rapidly transmuting gene expressing networks.

SWI/SNF-deficient Malignancies: Optimal Candidates for Immune-oncological Therapy?

Inactivation of different subunits of the SWItch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complex has emerged as one of the most frequent genetic pathways driving a variety of neoplasms of diverse histogenesis, originating in different organs. With few exceptions, most SWI/SNF-deficient malignancies pursue a highly aggressive clinical course resulting in widespread disease dissemination either at or soon after diagnosis, ultimately causing patients' death soon after diagnosis, despite the apparently curative treatment intention. To date, no satisfactorily effective systemic chemotherapy has been established for treating these diseases. This disappointing finding underlines the urgent need for an effective systemic therapy that would enable sufficient intermediate to long-term disease control. Recently, SWI/SNF-deficiency has increasingly emerged as pivotal in cancer immunogenicity and hence a promising biomarker predicting response to immune-checkpoint inhibition therapy utilizing several recently established drugs. This review summarizes the most recent literature on this topic with emphasis on the entities that most likely represent suitable candidates for immune therapy.

The Driverless Triple-Wild-Type (BRAF, RAS, KIT) Cutaneous Melanoma: Whole Genome Sequencing Discoveries

The genetic makeup of the triple-wild-type melanoma (BRAF, NRAS and NF1) has been known for some time, but those studies grouped together rare histopathological versions with common ones, as well as mucosal and even uveal ones. Here we used whole genome sequencing to genetically characterize the triple-wild-type melanoma (TWM), termed here as BRAF, RAS and KIT wild type (the most frequent oncogenic drivers of skin melanoma), using the most common histological forms and excluding rare ones. All these tumors except one were clearly induced by UV based on the mutational signature. The tumor mutational burden was low in TWM, except in the NF1 mutant forms, and a relatively high frequency of elevated LOH scores suggested frequent homologue recombination deficiency, but this was only confirmed by the mutation signature in one case. Furthermore, all these TWMs were microsatellite-stabile. In this driverless setting, we revealed rare oncogenic drivers known from melanoma or other cancer types and identified rare actionable tyrosine kinase mutations in NTRK1, RET and VEGFR1. Mutations of TWM identified genes involved in antitumor immunity (negative and positive predictors of immunotherapy), Ca++ and BMP signaling. The two regressed melanomas of this cohort shared a 17-gene mutation signature, containing genes involved in antitumor immunity and several cell surface receptors. Even with this comprehensive genomic approach, a few cases remained driverless, suggesting that unrecognized drivers are hiding among passenger mutations.

Combined Kdm6a and Trp53 Deficiency Drives the Development of Squamous Cell Skin Cancer in Mice

Cutaneous squamous cell carcinoma (cSCC) has among the highest mutation burdens of all cancers, reflecting its pathogenic association with the mutagenic effects of UV light exposure. Although mutations in cancer-relevant genes such as TP53 and NOTCH1 are common in cSCC, they are also tolerated in normal skin and suggest that other events are required for transformation; it is not yet clear whether epigenetic regulators cooperate in the pathogenesis of cSCC. KDM6A encodes a histone H3K27me2/me3 demethylase that is frequently mutated in cSCC and other cancers. Previous sequencing studies indicate that roughly 7% of cSCC samples harbor KDM6A mutations, including frequent truncating mutations, suggesting a role for this gene as a tumor suppressor in cSCC. Mice with epidermal deficiency of both Kdm6a and Trp53 exhibited 100% penetrant, spontaneous cSCC development within a year, and exome sequencing of resulting tumors reveals recurrent mutations in Ncstn and Vcan. Four of 16 tumors exhibited deletions in large portions of chromosome 1 involving Ncstn, whereas another 25% of tumors harbored deletions in chromosome 19 involving Pten, implicating the loss of other tumor suppressors as cooperating events for combined KDM6A- and TRP53-dependent tumorigenesis. This study suggests that KDM6A acts as an important tumor suppressor for cSCC pathogenesis.

Molecular underpinnings of exceptional response in primary malignant melanoma of the esophagus to anti-PD-1 monotherapy

BACKGROUND

Accumulating data suggest that mucosal melanoma, well known for its poor response to immune checkpoint blockade (ICB) and abysmal prognosis, is a heterogeneous subtype of melanoma with distinct genomic and clinical characteristics between different anatomic locations of the primary lesions. Primary malignant melanoma of the esophagus (PMME) is a rare, highly aggressive disease with a poorer prognosis compared with that of non-esophageal mucosal melanoma (NEMM). In this study, we retrospectively analyzed the efficacy of anti-programmed death (PD)-1 in patients with PMME and explored its molecular basis.

METHODS

The response and survival of patients with PMME and NEMM under anti-PD-1 monotherapy were retrospectively analyzed. To explore the molecular mechanisms of the difference in therapeutic efficacy between PMME and NEMM, we performed genomic analysis, bulk RNA sequencing, and multiplex immunohistochemistry staining.

RESULTS

We found that PMME (n=28) responded better to anti-PD-1 treatment than NEMM (n=64), with a significantly higher objective response rate (33.3% (95% CI 14.3% to 52.3%) vs 6.6% (95% CI 0.2% to 12.9%)) and disease control rate (74.1% (95% CI 56.4% to 91.7%) vs 37.7% (95% CI 25.2% to 50.2%)). Genomic sequencing analysis revealed that the genomic aberration landscape of PMME predominated in classical cancer driver genes, with approximately half of PMME cases harboring mutations in BRAF, N/KRAS, and NF1. In contrast, most NEMM cases were triple wild-type. Transcriptome analysis revealed that, compared with NEMM, PMME displayed more significant proliferation and inflammatory features with higher expression of genes related to antigen presentation and differentiation, and a less immunosuppressive signature with lower expression of inhibitory immune checkpoints and dedifferentiation-related genes. The multiplex immunohistochemical analysis also demonstrated higher CD8⁺ T-cell infiltration in PMME than in NEMM.

CONCLUSIONS

PMME is an outlier of mucosal melanoma showing a malicious phenotype but a particularly high response rate to ICB because of its distinct molecular characteristics. Patient stratification based on anatomic origin can facilitate clinical decision-making in patients with mucosal melanoma following the verification of our results in future prospective studies.

Objective response to immune checkpoint inhibitor therapy in NRAS-mutant melanoma: A systematic review and meta-analysis

Introduction

NRAS mutations are common in melanoma and confer a worse prognosis. Although most patients with metastatic melanoma receive immune checkpoint inhibitors (ICIs), the impact of NRAS mutational status on their efficacy remains under debate.

Methods

We performed a comprehensive literature search across several large databases. Inclusion criteria were trials, cohorts, and large case series that analyzed the primary outcome of objective response rate by NRAS mutational status in patients with melanoma treated with any line of ICI. At least two reviewers independently screened studies using Covidence software, extracted data, and assessed risk of bias. Standard meta-analysis was performed in R with sensitivity analysis and tests for bias.

Results

Data on 1770 patients from ten articles were pooled for meta-analysis, and the objective response rate to ICIs was calculated to compare NRAS-mutant and NRAS-wildtype melanoma. The objective response rate was 1.28 (95% confidence interval: 1.01-1.64). Sensitivity analysis identified the study by Dupuis et al. with influential impact on the pooled effect size and heterogeneity, favoring NRAS-mutant melanoma.

Discussion

In this meta-analysis evaluating the impact of NRAS mutational status on objective response to ICIs in metastatic melanoma, NRAS-mutant cutaneous melanoma demonstrated an increased likelihood of partial or complete tumor response, relative to NRAS-wildtype cutaneous melanoma. Genomic screening for NRAS mutations in patients with metastatic melanoma may improve predictive ability when initiating ICIs.

Comparative Genomics Provides Etiologic and Biological Insight into Melanoma Subtypes

Melanoma is a cancer of melanocytes, with multiple subtypes based on body site location. Cutaneous melanoma is associated with skin exposed to ultraviolet radiation; uveal melanoma occurs in the eyes; mucosal melanoma occurs in internal mucous membranes; and acral melanoma occurs on the palms, soles, and nail beds. Here, we present the largest whole-genome sequencing study of melanoma to date, with 570 tumors profiled, as well as methylation and RNA sequencing for subsets of tumors. Uveal melanoma is genomically distinct from other melanoma subtypes, harboring the lowest tumor mutation burden and with significantly mutated genes in the G-protein signaling pathway. Most cutaneous, acral, and mucosal melanomas share alterations in components of the MAPK, PI3K, p53, p16, and telomere pathways. However, the mechanism by which these pathways are activated or inactivated varies between melanoma subtypes. Additionally, we identify potential novel germline predisposition genes for some of the less common melanoma subtypes.

SIGNIFICANCE

This is the largest whole-genome analysis of melanoma to date, comprehensively comparing the genomics of the four major melanoma subtypes. This study highlights both similarities and differences between the subtypes, providing insights into the etiology and biology of melanoma. This article is highlighted in the In This Issue feature, p. 2711.

Melanoma 2.0. Skin cancer as a paradigm for emerging diagnostic technologies, computational modelling and artificial intelligence

We live in an unprecedented time in oncology. We have accumulated samples and cases in cohorts larger and more complex than ever before. New technologies are available for quantifying solid or liquid samples at the molecular level. At the same time, we are now equipped with the computational power necessary to handle this enormous amount of quantitative data. Computational models are widely used helping us to substantiate and interpret data. Under the label of systems and precision medicine, we are putting all these developments together to improve and personalize the therapy of cancer. In this review, we use melanoma as a paradigm to present the successful application of these technologies but also to discuss possible future developments in patient care linked to them. Melanoma is a paradigmatic case for disruptive improvements in therapies, with a considerable number of metastatic melanoma patients benefiting from novel therapies. Nevertheless, a large proportion of patients does not respond to therapy or suffers from adverse events. Melanoma is an ideal case study to deploy advanced technologies not only due to the medical need but also to some intrinsic features of melanoma as a disease and the skin as an organ. From the perspective of data acquisition, the skin is the ideal organ due to its accessibility and suitability for many kinds of advanced imaging techniques. We put special emphasis on the necessity of computational strategies to integrate multiple sources of quantitative data describing the tumour at different scales and levels.

Proteasomal down-regulation of the proapoptotic MST2 pathway contributes to BRAF inhibitor resistance in melanoma

The loss of MST2 pathway protein expression in BRAF inhibitor resistant melanoma cells is due to ubiquitination and subsequent proteasomal degradation and prevents MST2-mediated apoptosis.

The RAS-RAF-MEK-ERK pathway is hyperactivated in most malignant melanomas, and mutations in BRAF or NRAS account for most of these cases. BRAF inhibitors (BRAFi) are highly efficient for treating patients with BRAF^V600E mutations, but tumours frequently acquire resistance within a few months. Multiple resistance mechanisms have been identified, due to mutations or network adaptations that revive ERK signalling. We have previously shown that RAF proteins inhibit the MST2 proapoptotic pathway in a kinase-independent fashion. Here, we have investigated the role of the MST2 pathway in mediating resistance to BRAFi. We show that the BRAF^V600E mutant protein, but not the wild-type BRAF protein, binds to MST2 inhibiting its proapoptotic signalling. Down-regulation of MST2 reduces BRAFi-induced apoptosis. In BRAFi-resistant cell lines, MST2 pathway proteins are down-regulated by ubiquitination and subsequent proteasomal degradation rendering cells refractory to MST2 pathway–induced apoptosis. Restoration of apoptosis can be achieved by increasing MST2 pathway protein expression using proteasome inhibitors. In summary, we show that the MST2 pathway plays a role in the acquisition of BRAFi resistance in melanoma.

Developing Bottom-Up Induced Pluripotent Stem Cell Derived Solid Tumor Models Using Precision Genome Editing Technologies

Advances in genome and tissue engineering have spurred significant progress and opportunity for innovation in cancer modeling. Human induced pluripotent stem cells (iPSCs) are an established and powerful tool to study cellular processes in the context of disease-specific genetic backgrounds; however, their application to cancer has been limited by the resistance of many transformed cells to undergo successful reprogramming. Here, we review the status of human iPSC modeling of solid tumors in the context of genetic engineering, including how base and prime editing can be incorporated into "bottom-up" cancer modeling, a term we coined for iPSC-based cancer models using genetic engineering to induce transformation. This approach circumvents the need to reprogram cancer cells while allowing for dissection of the genetic mechanisms underlying transformation, progression, and metastasis with a high degree of precision and control. We also discuss the strengths and limitations of respective engineering approaches and outline experimental considerations for establishing future models.

Cutaneous and acral melanoma cross-OMICs reveals prognostic cancer drivers associated with pathobiology and ultraviolet exposure

Ultraviolet radiation (UV) is causally linked to cutaneous melanoma, yet the underlying epigenetic mechanisms, known as molecular sensors of exposure, have not been characterized in clinical biospecimens. Here, we integrate clinical, epigenome (DNA methylome), genome and transcriptome profiling of 112 cutaneous melanoma from two multi-ethnic cohorts. We identify UV-related alterations in regulatory regions and immunological pathways, with multi-OMICs cancer driver potential affecting patient survival. TAPBP, the top gene, is critically involved in immune function and encompasses several UV-altered methylation sites that were validated by targeted sequencing, providing cost-effective opportunities for clinical application. The DNA methylome also reveals non UV-related aberrations underlying pathological differences between the cutaneous and 17 acral melanomas. Unsupervised epigenomic mapping demonstrated that non UV-mutant cutaneous melanoma more closely resembles acral rather than UV-exposed cutaneous melanoma, with the latter showing better patient prognosis than the other two forms. These gene-environment interactions reveal translationally impactful mechanisms in melanomagenesis.

Integrated genomic analyses of acral and mucosal melanomas nominate novel driver genes

BACKGROUND

Acral and mucosal melanomas are aggressive subtypes of melanoma, which have a significantly lower burden of somatic mutations than cutaneous melanomas, but more frequent copy number variations, focused gene amplifications, and structural alterations. The landscapes of their genomic alterations remain to be fully characterized.

METHODS

We compiled sequencing data of 240 human acral and mucosal melanoma samples from 11 previously published studies and applied a uniform pipeline to call tumor cell content, ploidy, somatic and germline mutations, as well as CNVs, LOH, and SVs. We identified genes that are significantly mutated or recurrently affected by CNVs and implicated in oncogenesis. We further examined the difference in the frequency of recurrent pathogenic alterations between the two melanoma subtypes, correlation between pathogenic alterations, and their association with clinical features.

RESULTS

We nominated PTPRJ, mutated and homozygously deleted in 3.8% (9/240) and 0.8% (2/240) of samples, respectively, as a probable tumor suppressor gene, and FER and SKP2, amplified in 3.8% and 11.7% of samples, respectively, as probable oncogenes. We further identified a long tail of infrequent pathogenic alterations, involving genes such as CIC and LZTR1. Pathogenic germline mutations were observed on MITF, PTEN, ATM, and PRKN. We found BRAF V600E mutations in acral melanomas with fewer structural variations, suggesting that they are distinct and related to cutaneous melanomas. Amplifications of PAK1 and GAB2 were more commonly observed in acral melanomas, whereas SF3B1 R625 codon mutations were unique to mucosal melanomas (12.9%). Amplifications at 11q13-14 were frequently accompanied by fusion to a region on chromosome 6q12, revealing a recurrent novel structural rearrangement whose role remains to be elucidated.

CONCLUSIONS

Our meta-analysis expands the catalog of driver mutations in acral and mucosal melanomas, sheds new light on their pathogenesis and broadens the catalog of therapeutic targets for these difficult-to-treat cancers.

Integrative Genomic Profiling Uncovers Therapeutic Targets of Acral Melanoma in Asian Populations

PURPOSE

Acral melanoma is the major subtype of melanoma seen in Asian patients with melanoma and is featured by its insidious onset and poor prognosis. The genomic study that elucidates driving mutational events is fundamental to the development of gene-targeted therapy. However, research on genomic profiles of acral melanoma in Asian patients is still sparse.

EXPERIMENTAL DESIGN

We carried out whole-exome sequencing (WES) on 60 acral melanoma lesions (with 55 primary samples involved), targeted deep sequencing in a validation cohort of 48 cases, RNA sequencing in 37 acral melanoma samples (all from the 60 undergoing WES), and FISH in 233 acral melanoma specimens (54 of the 60 undergoing WES included). All the specimens were derived from Asian populations.

RESULTS

BRAF, NRAS, and KIT were discerned as significantly mutated genes (SMG) in acral melanoma. The detected COSMIC signature 3 related to DNA damage repair, along with the high genomic instability score, implied corresponding pathogenesis of acral melanoma. Moreover, the copy number gains of EP300 were associated with the response of acral melanoma to targeted therapy of A485 (a p300 inhibitor) and immune checkpoint blockade treatment. In addition, the temporal order in mutational processes of the samples was reconstructed, and copy-number alterations were identified as early mutational events.

CONCLUSIONS

Our study provided a detailed view of genomic instability, potential therapeutic targets, and intratumoral heterogeneity of acral melanoma, which might fuel the development of personalized strategies for treating acral melanoma in Asian populations.

Candidate therapeutic agents in a newly established triple wild‐type mucosal melanoma cell line

Background

Mucosal melanoma has characteristically distinct genetic features and typically poor prognosis. The lack of representative mucosal melanoma models, especially cell lines, has hindered translational research on this melanoma subtype. In this study, we aimed to establish and provide the biological properties, genomic features and the pharmacological profiles of a mucosal melanoma cell line that would contribute to the understanding and treatment optimization of molecularly‐defined mucosal melanoma subtype.

Methods

The sample was collected from a 67‐year‐old mucosal melanoma patient and processed into pieces for the establishment of cell line and patient‐derived xenograft (PDX) model. The proliferation and tumorigenic property of cancer cells from different passages were evaluated, and whole‐genome sequencing (WGS) was performed on the original tumor, PDX, established cell line, and the matched blood to confirm the establishment and define the genomic features of this cell line. AmpliconArchitect was conducted to depict the architecture of amplified regions detected by WGS. High‐throughput drug screening (HTDS) assay including a total of 103 therapeutic agents was implemented on the established cell line, and selected candidate agents were validated in the corresponding PDX model.

Results

A mucosal melanoma cell line, MM9H‐1, was established which exhibited robust proliferation and tumorigenicity after more than 100 serial passages. Genomic analysis of MM9H‐1, corresponding PDX, and the original tumor showed genetic fidelity across genomes, and MM9H‐1 was defined as a triple wild‐type (TWT) melanoma subtype lacking well‐characterized “driver mutations”. Instead, the amplification of several oncogenes, telomerase reverse transcriptase (TERT), v‐Raf murine sarcoma viral oncogene homolog B1 (BRAF), melanocyte Inducing transcription factor (MITF) and INO80 complex ATPase subunit (INO80), via large‐scale genomic rearrangement potentially contributed to oncogenesis of MM9H‐1. Moreover, HTDS identified proteasome inhibitors, especially bortezomib, as promising therapeutic candidates for MM9H‐1, which was verified in the corresponding PDX model in vivo.

Conclusions

We established and characterized a new mucosal melanoma cell line, MM9H‐1, and defined this cell line as a TWT melanoma subtype lacking well‐characterized “driver mutations”. The MM9H‐1 cell line could be adopted as a unique model for the preclinical investigation of mucosal melanoma.

Targeting TGF-β signal transduction for fibrosis and cancer therapy

Transforming growth factor β (TGF-β) has long been identified with its intensive involvement in early embryonic development and organogenesis, immune supervision, tissue repair, and adult homeostasis. The role of TGF-β in fibrosis and cancer is complex and sometimes even contradictory, exhibiting either inhibitory or promoting effects depending on the stage of the disease. Under pathological conditions, overexpressed TGF-β causes epithelial-mesenchymal transition (EMT), extracellular matrix (ECM) deposition, cancer-associated fibroblast (CAF) formation, which leads to fibrotic disease, and cancer. Given the critical role of TGF-β and its downstream molecules in the progression of fibrosis and cancers, therapeutics targeting TGF-β signaling appears to be a promising strategy. However, due to potential systemic cytotoxicity, the development of TGF-β therapeutics has lagged. In this review, we summarized the biological process of TGF-β, with its dual role in fibrosis and tumorigenesis, and the clinical application of TGF-β-targeting therapies.

Altered BAF occupancy and transcription factor dynamics in PBAF-deficient melanoma

ARID2 is the most recurrently mutated SWI/SNF complex member in melanoma; however, its tumor-suppressive mechanisms in the context of the chromatin landscape remain to be elucidated. Here, we model ARID2 deficiency in melanoma cells, which results in defective PBAF complex assembly with a concomitant genomic redistribution of the BAF complex. Upon ARID2 depletion, a subset of PBAF and shared BAF-PBAF-occupied regions displays diminished chromatin accessibility and associated gene expression, while BAF-occupied enhancers gain chromatin accessibility and expression of genes linked to the process of invasion. As a function of altered accessibility, the genomic occupancy of melanoma-relevant transcription factors is affected and significantly correlates with the observed transcriptional changes. We further demonstrate that ARID2-deficient cells acquire the ability to colonize distal organs in multiple animal models. Taken together, our results reveal a role for ARID2 in mediating BAF and PBAF subcomplex chromatin dynamics with consequences for melanoma metastasis.

PBRM1 inactivation promotes upregulation of human endogenous retroviruses in a HIF-dependent manner

Clear cell renal cell carcinoma (ccRCC) is considered an immunotherapy-responsive disease; however, the reasons for this remain unclear. Studies have variably implicated PBRM1 mutations as a predictive biomarker of immune checkpoint blockade (ICB) response, and separate studies demonstrate that expression of human endogenous retroviruses (hERVs) might be an important class of tumor-associated antigens. We sought to understand if specific mutations were associated with hERV expression. Two large, annotated genomic datasets, TCGA KIRC and IMmotion150, were used to correlate mutations and hERV expression. PBRM1 mutations were consistently associated with increased hERV expression in primary tumors. In vitro silencing of PBRM1, HIF1A and HIF2A followed by RNA-seq was performed in UMRC2 cells, confirming that PBRM1 regulates hERVs in a HIF1α- and HIF2α- dependent manner and that hERVs of the HERVERI superfamily are enriched in PBRM1-regulated hERVs. Our results uncover a role of PBRM1 in the negative regulation of hERVs in ccRCC. Moreover, the HIF-dependent nature of hERV expression explains the previously reported ccRCC-specific clinical associations of PBRM1 mutant ccRCC with both a good prognosis as well as improved clinical outcomes to ICB.

Individualized Treatment Strategy for Cutaneous Melanoma: Where Are We Now and Where Are We Going?

In the past several decades, innovative research in cancer biology and immunology has contributed to novel therapeutics, such as targeted therapy and immunotherapy, which have transformed the management of patients with melanoma. Despite the remarkable therapeutic outcomes of targeted treatments targeting MAPK signaling and immunotherapy that suppresses immune checkpoints, some individuals acquire therapeutic resistance and disease recurrence. This review summarizes the current understanding of melanoma genetic variations and discusses individualized melanoma therapy options, particularly for advanced or metastatic melanoma, as well as potential drug resistance mechanisms. A deeper understanding of individualized treatment will assist in improving clinical outcomes for patients with cutaneous melanoma.

Intragenic NF1 deletions in sinonasal mucosal malignant melanoma

Mucosal malignant melanoma (MMM) is a rare and aggressive tumor. Despite effective local therapies, tumor recurrence and metastasis remain frequent. The genetics of MMM remain incompletely understood. This study is aimed to identify actionable genetic alterations by next-generation sequencing. Fifteen MMM samples were analyzed by next-generation and Sanger sequencing. Gene copy number alterations were analyzed by MLPA. Mutation status was correlated with pERK, pAKT, and Ki-67 expression and follow-up data. Inactivating mutations and intragenic deletions in neurofibromatosis type-1 (NF1) were identified in 3 and 2 cases, respectively, (in total 5/15, 33%) and activating mutations in NRAS and KRAS (3/15, 20%) cases. Other mutated genes included CDKN2A, APC, ATM, MITF, FGFR1, and FGFR2. BRAF and KIT mutations were not observed. Cases with NF1 alterations tended to have worse overall survival. The mutational status was not associated with pERK, pAKT, or Ki-67 immunostaining. MMM carries frequent gene mutations activating the MAPK pathway, similar to cutaneous melanoma. In contrast, NF1 is the most frequently affected gene. Intragenic NF1 deletions have not been described before and may go undetected by sequencing studies. This finding is clinically relevant as NF1-mutated melanomas have worse survival and could benefit from therapy with immune checkpoint and MEK inhibitors.

UVB mutagenesis differs in Nras- and Braf-mutant mouse models of melanoma

BRAF-mutant melanomas are more likely than NRAS-mutant melanomas to arise in anatomical locations protected from chronic sun damage. We hypothesized that this discrepancy in tumor location is a consequence of the differential sensitivity of BRAF and NRAS-mutant melanocytes to ultraviolet light (UV)-mediated carcinogenesis. We tested this hypothesis by comparing the mutagenic consequences of a single neonatal, ultraviolet-AI (UVA; 340-400 nm) or ultraviolet-B (UVB; 280-390 nm) exposure in mouse models heterozygous for mutant Braf or homozygous for mutant Nras Tumor onset was accelerated by UVB, but not UVA, and the resulting melanomas contained recurrent mutations affecting the RING domain of MAP3K1 and Actin-binding domain of Filamin A. Melanomas from UVB-irradiated, Braf-mutant mice averaged twice as many single-nucleotide variants and five times as many dipyrimidine variants than tumors from similarly irradiated Nras-mutant mice. A mutational signature discovered in UVB-accelerated tumors mirrored COSMIC signatures associated with human skin cancer and was more prominent in Braf- than Nras-mutant murine melanomas. These data show that a single UVB exposure yields a greater burden of mutations in murine tumors driven by oncogenic Braf.

Prediction of Immunotherapy Response in Melanoma through Combined Modeling of Neoantigen Burden and Immune-Related Resistance Mechanisms

PURPOSE

While immune checkpoint blockade (ICB) has become a pillar of cancer treatment, biomarkers that consistently predict patient response remain elusive due to the complex mechanisms driving immune response to tumors. We hypothesized that a multi-dimensional approach modeling both tumor and immune-related molecular mechanisms would better predict ICB response than simpler mutation-focused biomarkers, such as tumor mutational burden (TMB).

EXPERIMENTAL DESIGN

Tumors from a cohort of patients with late-stage melanoma (n = 51) were profiled using an immune-enhanced exome and transcriptome platform. We demonstrate increasing predictive power with deeper modeling of neoantigens and immune-related resistance mechanisms to ICB.

RESULTS

Our neoantigen burden score, which integrates both exome and transcriptome features, more significantly stratified responders and nonresponders (P = 0.016) than TMB alone (P = 0.049). Extension of this model to include immune-related resistance mechanisms affecting the antigen presentation machinery, such as HLA allele-specific LOH, resulted in a composite neoantigen presentation score (NEOPS) that demonstrated further increased association with therapy response (P = 0.002).

CONCLUSIONS

NEOPS proved the statistically strongest biomarker compared with all single-gene biomarkers, expression signatures, and TMB biomarkers evaluated in this cohort. Subsequent confirmation of these findings in an independent cohort of patients (n = 110) suggests that NEOPS is a robust, novel biomarker of ICB response in melanoma.

Mucosal Melanoma: Pathological Evolution, Pathway Dependency and Targeted Therapy

Mucosal melanoma (MM) is a rare melanoma subtype that originates from melanocytes within sun-protected mucous membranes. Compared with cutaneous melanoma (CM), MM has worse prognosis and lacks effective treatment options. Moreover, the endogenous or exogenous risk factors that influence mucosal melanocyte transformation, as well as the identity of MM precursor lesions, are ambiguous. Consequently, there remains a lack of molecular markers that can be used for early diagnosis, and therefore better management, of MM. In this review, we first summarize the main functions of mucosal melanocytes. Then, using oral mucosal melanoma (OMM) as a model, we discuss the distinct pathologic stages from benign mucosal melanocytes to metastatic MM, mapping the possible evolutionary trajectories that correspond to MM initiation and progression. We highlight key areas of ambiguity during the genetic evolution of MM from its benign lesions, and the resolution of which could aid in the discovery of new biomarkers for MM detection and diagnosis. We outline the key pathways that are altered in MM, including the MAPK pathway, the PI3K/AKT pathway, cell cycle regulation, telomere maintenance, and the RNA maturation process, and discuss targeted therapy strategies for MM currently in use or under investigation.

Large-Scale Transcriptome Analysis Identified a Novel Cancer Driver Genes Signature for Predicting the Prognostic of Patients With Hepatocellular Carcinoma

Background: Hepatocellular carcinoma (HCC) is a common malignant tumor with high mortality and heterogeneity. Genetic mutations caused by driver genes are important contributors to the formation of the tumor microenvironment. The purpose of this study is to discuss the expression of cancer driver genes in tumor tissues and their clinical value in predicting the prognosis of HCC.

Methods: All data were sourced from The Cancer Genome Atlas (TCGA), International Cancer Genome Consortium (ICGC), and Gene Expression Omnibus (GEO) public databases. Differentially expressed and prognostic genes were screened by the expression distribution of the cancer driver genes and their relationship with survival. Candidate genes were subjected to functional enrichment and transcription factor regulatory network. We further constructed a prognostic signature and analyzed the survival outcomes and immune status between different risk groups.

Results: Most cancer driver genes are specifically expressed in cancer tissues. Driver genes may influence HCC progression through processes such as transcription, cell cycle, and T-cell receptor-related pathways. Patients in different risk groups had significant survival differences (p < 0.05), and risk scores showed high predictive efficacy (AUC>0.69). Besides, risk subgroups were also associated with multiple immune functions and immune cell content.

Conclusion: We confirmed the critical role of cancer driver genes in mediating HCC progression and the immune microenvironment. Risk subgroups contribute to the assessment of prognostic value in different patients and explain the heterogeneity of HCC.

Targeting Genome Stability in Melanoma-A New Approach to an Old Field

Despite recent groundbreaking advances in the treatment of cutaneous melanoma, it remains one of the most treatment-resistant malignancies. Due to resistance to conventional chemotherapy, the therapeutic focus has shifted away from aiming at melanoma genome stability in favor of molecularly targeted therapies. Inhibitors of the RAS/RAF/MEK/ERK (MAPK) pathway significantly slow disease progression. However, long-term clinical benefit is rare due to rapid development of drug resistance. In contrast, immune checkpoint inhibitors provide exceptionally durable responses, but only in a limited number of patients. It has been increasingly recognized that melanoma cells rely on efficient DNA repair for survival upon drug treatment, and that genome instability increases the efficacy of both MAPK inhibitors and immunotherapy. In this review, we discuss recent developments in the field of melanoma research which indicate that targeting genome stability of melanoma cells may serve as a powerful strategy to maximize the efficacy of currently available therapeutics.