BRD4-targeted therapy induces Myc-independent cytotoxicity in Gnaq/11-mutatant uveal melanoma cells

Updates in the Management of Uveal Melanoma

ABSTRACT

Uveal melanoma (UM), arising from intraocular melanocytes, poses a complex clinical challenge with a substantial risk of distant metastasis, often to the liver. Molecular profiling, encompassing genetic, cytogenetic, gene expression, and immunological subsets, plays a pivotal role in determining prognoses. The evolving landscape includes promising systemic treatments, such as tebentafusp, a novel immune-modulating bispecific fusion protein, and targeted therapies. Combined regional and systemic approaches, including immune checkpoint inhibitors and innovative liver-directed therapy, are also under investigation. Although recent progress has improved outcomes, ongoing research aims to address the unique challenges of UM and develop effective therapies, particularly for HLA-A*02:01-negative patients who represent a significant unmet medical need. This review comprehensively discusses the molecular characteristics of UM, risk stratification methods, and the current and future spectrum of regional and systemic therapeutic modalities.

Uveal melanoma modeling in mice and zebrafish

Despite extensive research and refined therapeutic options, the survival for metastasized uveal melanoma (UM) patients has not improved significantly. UM, a malignant tumor originating from melanocytes in the uveal tract, can be asymptomatic and small tumors may be detected only during routine ophthalmic exams; making early detection and treatment difficult. UM is the result of a number of characteristic somatic alterations which are associated with prognosis. Although UM morphology and biology have been extensively studied, there are significant gaps in our understanding of the early stages of UM tumor evolution and effective treatment to prevent metastatic disease remain elusive. A better understanding of the mechanisms that enable UM cells to thrive and successfully metastasize is crucial to improve treatment efficacy and survival rates. For more than forty years, animal models have been used to investigate the biology of UM. This has led to a number of essential mechanisms and pathways involved in UM aetiology. These models have also been used to evaluate the effectiveness of various drugs and treatment protocols. Here, we provide an overview of the molecular mechanisms and pharmacological studies using mouse and zebrafish UM models. Finally, we highlight promising therapeutics and discuss future considerations using UM models such as optimal inoculation sites, use of BAP1mut-cell lines and the rise of zebrafish models.

High-throughput chemogenetic drug screening reveals PKC-RhoA/PKN as a targetable signaling vulnerability in GNAQ-driven uveal melanoma

Uveal melanoma (UM) is the most prevalent cancer of the eye in adults, driven by activating mutation of GNAQ/GNA11; however, there are limited therapies against UM and metastatic UM (mUM). Here, we perform a high-throughput chemogenetic drug screen in GNAQ-mutant UM contrasted with BRAF-mutant cutaneous melanoma, defining the druggable landscape of these distinct melanoma subtypes. Across all compounds, darovasertib demonstrates the highest preferential activity against UM. Our investigation reveals that darovasertib potently inhibits PKC as well as PKN/PRK, an AGC kinase family that is part of the "dark kinome." We find that downstream of the Gαq-RhoA signaling axis, PKN converges with ROCK to control FAK, a mediator of non-canonical Gαq-driven signaling. Strikingly, darovasertib synergizes with FAK inhibitors to halt UM growth and promote cytotoxic cell death in vitro and in preclinical metastatic mouse models, thus exposing a signaling vulnerability that can be exploited as a multimodal precision therapy against mUM.

Reciprocal positive regulation between BRD4 and YAP in GNAQ-mutant uveal melanoma cells confers sensitivity to BET inhibitors

Uveal melanoma (UM) is the most common intraocular cancer in adults. UMs are usually initiated by a mutation in GNAQ or GNA11 (encoding Gq or G11, respectively), unlike cutaneous melanomas (CMs), which usually carry a BRAF or NRAS mutation. Currently, there are no clinically effective targeted therapies for UM carrying Gq/11 mutations. Here, we identified a causal link between Gq activating mutations and hypersensitivity to bromodomain and extra-terminal (BET) inhibitors. BET inhibitors transcriptionally repress YAP via BRD4 regardless of Gq mutation status, independently of Hippo core components LATS1/2. In contrast, YAP/TAZ downregulation reduces BRD4 transcription exclusively in Gq-mutant cells and LATS1/2 double knockout cells, both of which are featured by constitutively active YAP/TAZ. The transcriptional interdependency between BRD4 and YAP identified in Gq-mutated cells is responsible for the preferential inhibitory effect of BET inhibitors on the growth and dissemination of Gq-mutated UM cells compared to BRAF-mutated CM cells in both culture cells and animal models. Our findings suggest BRD4 as a viable therapeutic target for Gq-driven UMs that are addicted to unrestrained YAP function.

BMS-986158, a Small Molecule Inhibitor of the Bromodomain and Extraterminal Domain Proteins, in Patients with Selected Advanced Solid Tumors: Results from a Phase 1/2a Trial

This phase 1/2a, open-label study (NCT02419417) evaluated the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics of BMS-986158, a selective bromodomain and extraterminal domain (BET) inhibitor. Dose escalation was performed with 3 BMS-986158 dosing schedules: A (5 days on, 2 days off; range, 0.75–4.5 mg), B (14 days on, 7 days off; 2.0–3.0 mg), and C (7 days on, 14 days off; 2.0–4.5 mg). Eighty-three patients were enrolled and received ≥1 BMS-986158 dose. Diarrhea (43%) and thrombocytopenia (39%) were the most common treatment-related adverse events (TRAEs). A lower incidence of TRAEs was found with schedules A (72%) and C (72%) vs. B (100%). Stable disease was achieved in 12 (26.1%), 3 (37.5%), and 9 (31.0%) patients on schedules A, B, and C, respectively. Two patients on schedule A with a 4.5-mg starting dose (ovarian cancer, n = 1; nuclear protein in testis [NUT] carcinoma, n = 1) experienced a partial response. BMS-986158 demonstrated rapid-to-moderate absorption (median time to maximum observed plasma concentration, 1–4 h). As expected with an epigenetic modifier, expression changes in select BET-regulated genes occurred with BMS-986158 treatment. Schedule A dosing (5 days on, 2 days off) yielded tolerable safety, preliminary antitumor activity, and a dose-proportional PK profile.

Breaking boundaries: Pan BETi disrupt 3D chromatin structure, BD2-selective BETi are strictly epigenetic transcriptional regulators

BACKGROUND

Bromodomain and extraterminal proteins (BETs) are more than just epigenetic regulators of transcription. Here we highlight a new role for the BET protein BRD4 in the maintenance of higher order chromatin structure at Topologically Associating Domain Boundaries (TADBs). BD2-selective and pan (non-selective) BET inhibitors (BETi) differentially support chromatin structure, selectively affecting transcription and cell viability.

METHODS

Using RNA-seq and BRD4 ChIP-seq, the differential effect of BETi treatment on the transcriptome and BRD4 chromatin occupancy of human aortic endothelial cells from diabetic patients (dHAECs) stimulated with TNFα was evaluated. Chromatin decondensation and DNA fragmentation was assessed by immunofluorescence imaging and quantification. Key dHAEC findings were verified in proliferating monocyte-like THP-1 cells using real time-PCR, BRD4 co-immunoprecipitation studies, western blots, proliferation and apoptosis assays.

FINDINGS

We discovered that 1) BRD4 co-localizes with Ying-Yang 1 (YY1) at TADBs, critical chromatin structure complexes proximal to many DNA repair genes. 2) BD2-selective BETi enrich BRD4/YY1 associations, while pan-BETi do not. 3) Failure to support chromatin structures through BRD4/YY1 enrichment inhibits DNA repair gene transcription, which induces DNA damage responses, and causes widespread chromatin decondensation, DNA fragmentation, and apoptosis. 4) BD2-selective BETi maintain high order chromatin structure and cell viability, while reducing deleterious pro-inflammatory transcription.

INTERPRETATION

BRD4 plays a previously unrecognized role at TADBs. BETi differentially impact TADB stability. Our results provide translational insight for the development of BETi as therapeutics for a range of diseases including CVD, chronic kidney disease, cancer, and COVID-19.

BAP1 loss augments sensitivity to BET inhibitors in cancer cells

The tumor suppressor gene BAP1 encodes a widely expressed deubiquitinase for histone H2A. Both hereditary and acquired mutations are associated with multiple cancer types, including cutaneous melanoma (CM), uveal melanoma (UM), and clear cell renal cell carcinoma (ccRCC). However, there is no personalized therapy for BAP1-mutant cancers. Here, we describe an epigenetic drug library screening to identify small molecules that exert selective cytotoxicity against BAP1 knockout CM cells over their isogenic parental cells. Hit characterization reveals that BAP1 loss renders cells more vulnerable to bromodomain and extraterminal (BET) inhibitor-induced transcriptional alterations, G1/G0 cell cycle arrest and apoptosis. The association of BAP1 loss with sensitivity to BET inhibitors is observed in multiple BAP1-deficient cancer cell lines generated by gene editing or derived from patient tumors as well as immunodeficient xenograft and immunocompetent allograft murine models. We demonstrate that BAP1 deubiquitinase activity reduces sensitivity to BET inhibitors. Concordantly, ectopic expression of RING1A or RING1B (H2AK119 E3 ubiquitin ligases) enhances sensitivity to BET inhibitors. The mechanistic study shows that the BET inhibitor OTX015 exerts a more potent suppressive effect on the transcription of various proliferation-related genes, especially MYC, in BAP1 knockout cells than in their isogenic parental cells, primarily by targeting BRD4. Furthermore, ectopic expression of Myc rescues the BET inhibitor-sensitizing effect induced by BAP1 loss. Our study reveals new approaches to specifically suppress BAP1-deficient cancers, including CM, UM, and ccRCC.

Genetic Landscape and Emerging Therapies in Uveal Melanoma

Despite successful treatment of primary uveal melanoma, up to 50% of patients will develop systemic metastasis. Metastatic disease portends a poor outcome, and no adjuvant or metastatic therapy has been FDA approved. The genetic landscape of uveal melanoma is unique, providing prognostic and potentially therapeutic insight. In this review, we discuss our current understanding of the molecular and cytogenetic mutations in uveal melanoma, and the importance of obtaining such information. Most of our knowledge is based on primary uveal melanoma and a better understanding of the mutational landscape in metastatic uveal melanoma is needed. Clinical trials targeting certain mutations such as GNAQ/GNA11, BAP1, and SF3B1 are ongoing and promising. We also discuss the role of liquid biopsies in uveal melanoma in this review.

Metastatic disease to the liver: Locoregional therapy strategies and outcomes

Secondary cancers of the liver are more than twenty times more common than primary tumors and are incurable in most cases. While surgical resection and systemic chemotherapy are often the first-line therapy for metastatic liver disease, a majority of patients present with bilobar disease not amenable to curative local resection. Furthermore, by the time metastasis to the liver has developed, many tumors demonstrate a degree of resistance to systemic chemotherapy. Fortunately, catheter-directed and percutaneous locoregional approaches have evolved as major treatment modalities for unresectable metastatic disease. These novel techniques can be used for diverse applications ranging from curative intent for small localized tumors, downstaging of large tumors for resection, or locoregional control and palliation of advanced disease. Their use has been associated with increased tumor response, increased disease-free and overall survival, and decreased morbidity and mortality in a broad range of metastatic disease. This review explores recent advances in liver-directed therapies for metastatic liver disease from primary colorectal, neuroendocrine, breast, and lung cancer, as well as uveal melanoma, cholangiocarcinoma, and sarcoma. Therapies discussed include bland transarterial embolization, chemoembolization, radioembolization, and ablative therapies, with a focus on current treatment approaches, outcomes of locoregional therapy, and future directions in each type of metastatic disease.

Development of new therapeutic options for the treatment of uveal melanoma

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults. Important cytogenetic and genetic risk factors for the development of UM include chromosome 3 monosomy, mutations in the guanine nucleotide-binding proteins GNAQ/GNA11, and loss of the BRACA1-associated protein 1 (BAP 1). Most primary UMs are treated conservatively with radiotherapy, but enucleation is necessary for large tumours. Despite the effectiveness of local control, up to 50% of UM patients develop metastasis for which there are no effective therapies. Attempts to utilise the targeted therapies that have been developed for the treatment of other cancers, including a range of signal transduction pathway inhibitors, have rarely produced significant outcomes in UM. Similarly, the application of immunotherapies that are effective in cutaneous melanoma to treat UM have also been disappointing. Other approaches that have been initiated involve proteasomal inhibitors and histone deacetylase inhibitors which are approved for the treatment of other cancers. Nevertheless, there have been occasional positive outcomes from these treatments in UM. Moreover, combination approaches in UM have also yielded some positive developments. It would be valuable to identify how to apply such therapies efficiently in UM, potentially via individualised tumour profiling. It would also be important to characterise UM tumours to differentiate the potential drivers of progression from those in other types of cancers. The recent identification of novel kinases and metastatic genes in UM tumours makes the development of new UM-specific treatments feasible.

Clinical Trials in Metastatic Uveal Melanoma: Current Status

BACKGROUND

Uveal melanoma is a rare subtype of melanoma. Prognosis and survival rates for patients with metastatic uveal melanoma remain poor. No current FDA-approved standard of care therapy is available for patients with metastatic uveal melanoma. Thus, clinical trials are essential for the development of new therapies and to provide patients hope for improved survival and outcomes.

SUMMARY

In this article, we review clinical trials identified on the database https://clinicaltrials.gov that are open and enrolling patients with metastatic uveal melanoma as of November 26, 2019. This search produced 17 active trials involving liver-directed therapy, CNS-directed therapy, and systemic therapy with immunotherapy, targeted therapy, or oncolytic virus therapy. Here, we discuss liver and CNS-directed therapy as well as systemic targeted therapy and oncolytic virus therapy. Immunotherapy clinical trials are discussed in a companion review article by Dr. Marlana Orloff.

KEY MESSAGES

Various novel therapeutic targets and immunomodulatory approaches are on the horizon for patients with metastatic uveal melanoma and may yield incremental therapeutic benefit. Selecting a clinical trial must be individualized and made jointly with the patient and his/her oncologist.

Biomarker discovery by feature ranking: Evaluation on a case study of embryonal tumors

The task of biomarker discovery is best translated to the machine learning task of feature ranking. Namely, the goal of biomarker discovery is to identify a set of potentially viable targets for addressing a given biological status. This is aligned with the definition of feature ranking and its goal - to produce a list of features ordered by their importance for the target concept. This differs from the task of feature selection (typically used for biomarker discovery) in that it catches viable biomarkers that have redundant or overlapping information with often highly important biomarkers, while with feature selection this is not the case. We propose to use a methodology for evaluating feature rankings to assess the quality of a given feature ranking and to discover the best cut-off point. We demonstrate the effectiveness of the proposed methodology on 10 datasets containing data about embryonal tumors. We evaluate two most commonly used feature ranking algorithms (Random forests and RReliefF) and using the evaluation methodology identifies a set of viable biomarkers that have been confirmed to be related to cancer.

Uveal melanoma: progress in molecular biology and therapeutics

Uveal melanoma (UM) is the most common intraocular malignancy in adults. So far, no systemic therapy or standard treatment exists to reduce the risk of metastasis and improve overall survival of patients. With the increased knowledge regarding the molecular pathways that underlie the oncogenesis of UM, it is expected that novel therapeutic approaches will be available to conquer this disease. This review provides a summary of the current knowledge of, and progress made in understanding, the pathogenesis, genetic mutations, epigenetics, and immunology of UM. With the advent of the omics era, multi-dimensional big data are publicly available, providing an innovation platform to develop effective targeted and personalized therapeutics for UM patients. Indeed, recently, a great number of therapies have been reported specifically for UM caused by oncogenic mutations, as well as other etiologies. In this review, special attention is directed to advancements in targeted therapies. In particular, we discuss the possibilities of targeting: GNAQ/GNA11, PLCβ, and CYSLTR2 mutants; regulators of G-protein signaling; the secondary messenger adenosine diphosphate (ADP)-ribosylation factor 6 (ARF6); downstream pathways, such as those involving mitogen-activated protein kinase/MEK/extracellular signal-related kinase, protein kinase C (PKC), phosphoinositide 3-kinase/Akt/mammalian target of rapamycin (mTOR), Trio/Rho/Rac/Yes-associated protein, and inactivated BAP1; and immune-checkpoint proteins cytotoxic T-lymphocyte antigen 4 and programmed cell-death protein 1/programmed cell-death ligand 1. Furthermore, we conducted a survey of completed and ongoing clinical trials applying targeted and immune therapies for UM. Although drug combination therapy based on the signaling pathways involved in UM has made great progress, targeted therapy is still an unmet medical need.

The Latest on Uveal Melanoma Research and Clinical Trials: Updates from the Cure Ocular Melanoma (CURE OM) Science Meeting (2019)

Uveal melanoma is a rare cancer in adults, but its treatment is one of the clinical unmet needs in the melanoma field. Metastatic disease develops in approximately 50% of patients and is associated with poor survival due to the lack of effective treatment options. It provides a paradigm for cancers that show evidence of aberrant G protein-coupled receptor signaling, tumor dormancy, and liver-selective metastatic tropism and are associated with the loss of the BAP1 tumor suppressor. At the Melanoma Research Foundation CURE OM Science Meeting at the Society for Melanoma Research Meeting held in Utah on November 20, 2019, clinicians and researchers presented findings from their studies according to three themes within uveal melanoma: (i) ongoing clinical trials, (ii) molecular determinants, and (iii) novel targets that could be translated into clinical trials. This meeting underscored the high interest in the uveal melanoma research field and the unmet need for effective treatment strategies for late-stage disease. Findings from ongoing clinical trials are promising, and multiple studies show how novel combinatorial strategies increase response rates. Novel targets and tumor vulnerabilities identified bioinformatically or through high-throughput screens also reveal new opportunities to target uveal melanoma. The future directions pursued by the uveal melanoma research field will likely have an impact on other cancer types that harbor similar genetic alterations and/or show similar biological properties.

Novel Approaches to the Systemic Management of Uveal Melanoma

PURPOSE OF REVIEW

Uveal melanoma is a distinct subtype of melanoma characterized by a unique biology and divergent response to immune therapies. In this review, we will discuss our current understanding of the pathophysiology of uveal melanoma, systemic treatment options for advanced disease, and potential future therapeutic directions.

RECENT FINDINGS

Although treatment with single-agent checkpoint blockade has been generally disappointing, the results of combined checkpoint blockade are modestly more promising. Several alternative systemic therapeutic approaches have been or are currently being investigated, including two agents that have been taken into registration-intent clinical trials: tebentafusp, a T cell redirecting agent, and IDE196, an oral protein kinase C inhibitor. Treatment of advanced uveal melanoma remains challenging, however, encouraging results from novel agents offer hope for improvement in the near future.

Targeting Epigenetic Modifications in Uveal Melanoma

Uveal melanoma (UM), the most common intraocular malignancy in adults, is a rare subset of melanoma. Despite effective primary therapy, around 50% of patients will develop the metastatic disease. Several clinical trials have been evaluated for patients with advanced UM, though outcomes remain dismal due to the lack of efficient therapies. Epigenetic dysregulation consisting of aberrant DNA methylation, histone modifications, and small non-coding RNA expression, silencing tumor suppressor genes, or activating oncogenes, have been shown to play a significant role in UM initiation and progression. Given that there is no evidence any approach improves results so far, adopting combination therapies, incorporating a new generation of epigenetic drugs targeting these alterations, may pave the way for novel promising therapeutic options. Furthermore, the fusion of effector enzymes with nuclease-deficient Cas9 (dCas9) in clustered regularly interspaced short palindromic repeats (CRISPR) associated protein 9 (Cas9) system equips a potent tool for locus-specific erasure or establishment of DNA methylation as well as histone modifications and, therefore, transcriptional regulation of specific genes. Both, CRISPR-dCas9 potential for driver epigenetic alterations discovery, and possibilities for their targeting in UM are highlighted in this review.

Uveal melanoma

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults. UMs are usually initiated by a mutation in GNAQ or GNA11, unlike cutaneous melanomas, which usually harbour a BRAF or NRAS mutation. The annual incidence in Europe and the USA is ~6 per million population per year. Risk factors include fair skin, light-coloured eyes, congenital ocular melanocytosis, ocular melanocytoma and the BAP1-tumour predisposition syndrome. Ocular treatment aims at preserving the eye and useful vision and, if possible, preventing metastases. Enucleation has largely been superseded by various forms of radiotherapy, phototherapy and local tumour resection, often administered in combination. Ocular outcomes are best with small tumours not extending close to the optic disc and/or fovea. Almost 50% of patients develop metastatic disease, which usually involves the liver, and is usually fatal within 1 year. Although UM metastases are less responsive than cutaneous melanoma to chemotherapy or immune checkpoint inhibitors, encouraging results have been reported with partial hepatectomy for solitary metastases, with percutaneous hepatic perfusion with melphalan or with tebentafusp. Better insight into tumour immunology and metabolism may lead to new treatments.

Mouse models of uveal melanoma: Strengths, weaknesses, and future directions

Uveal melanoma is the most common primary malignancy of the eye, and a number of discoveries in the last decade have led to a more thorough molecular characterization of this cancer. However, the prognosis remains dismal for patients with metastases, and there is an urgent need to identify treatments that are effective for this stage of disease. Animal models are important tools for preclinical studies of uveal melanoma. A variety of models exist, and they have specific advantages, disadvantages, and applications. In this review article, these differences are explored in detail, and ideas for new models that might overcome current challenges are proposed.

Bromodomain and extraterminal domain inhibitor enhances the antitumor effect of imatinib in gastrointestinal stromal tumours

In gastrointestinal stromal tumours (GISTs), the function of bromodomain-containing 4 (BRD4) remains underexplored. BRD4 mRNA abundance was quantified in GISTs. In the current study, we investigated the role of BRD4 in GISTs. Our results show a significant enhancement in BRD4 mRNA and a shift from very low-risk/low-risk to high-risk levels as per NCCN specifications. Overexpression of BRD4 correlated with unfavourable genotype, nongastric location, enhanced risk and decreased disease-free survival, which were predicted independently. Knockout of BRD4 in vitro suppressed KIT expression, which led to inactivation of the KIT/PI3K/AKT/mTOR pathway, impeded migration and cell growth and made the resistant GIST cells sensitive to imatinib. The expression of KIT was repressed by a BRD4 inhibitor JQ1, which also induced myristoylated-AKT-suppressible caspases 3 and 9 activities, induced LC3-II, exhibited dose-dependent therapeutic synergy with imatinib and attenuated the activation of the PI3K/AKT/mTOR pathway. In comparison with their single therapy, the combination of JQ1/imatinib more efficiently suppressed the growth of xenografts and exhibited a reduction in KIT phosphorylation, a decrease in Ki-67 and in the levels of phosphorylated PI3K/AKT/mTOR and enhanced TUNEL staining. Thus, we characterized the biological, prognostic and therapeutic implications of overexpressed BRD4 in GIST and observed that JQ1 suppresses KIT transactivation and nullifies the activation of PI3K/AKT/mTOR, providing a potential strategy for treating imatinib-resistant GIST through dual blockade of KIT and BRD4.

Stromal fibroblast growth factor 2 reduces the efficacy of bromodomain inhibitors in uveal melanoma

Alterations in transcriptional programs promote tumor development and progression and are targetable by bromodomain and extraterminal (BET) protein inhibitors. However, in a multi‐site clinical trial testing the novel BET inhibitor, PLX51107, in solid cancer patients, liver metastases of uveal melanoma (UM) patients progressed rapidly following treatment. Mechanisms of resistance to BET inhibitors in UM are unknown. We show that fibroblast growth factor 2 (FGF2) rescued UM cells from growth inhibition by BET inhibitors, and FGF2 effects were reversible by FGF receptor (FGFR) inhibitors. BET inhibitors also increased FGFR protein expression in UM cell lines and in patient tumor samples. Hepatic stellate cells (HSCs) secrete FGF2, and HSC‐conditioned medium provided resistance of UM cells to BET inhibitors. PLX51107 was ineffective in vivo, but the combination of a FGFR inhibitor, AZD4547, and PLX51107 significantly suppressed the growth of xenograft UM tumors formed from subcutaneous inoculation of UM cells with HSCs and orthotopically in the liver. These results suggest that co‐targeting of FGFR signaling is required to increase the responses of metastatic UM to BET inhibitors.

Targeted Therapy of Uveal Melanoma: Recent Failures and New Perspectives

Among Uveal Melanoma (UM) driver mutations, those involving GNAQ or GNA11 genes are the most frequent, while a minor fraction of tumors bears mutations in the PLCB4 or CYSLTR2 genes. Direct inhibition of constitutively active oncoproteins deriving from these mutations is still in its infancy in UM, whereas BRAFV600E-targeted therapy has obtained relevant results in cutaneous melanoma. However, UM driver mutations converge on common downstream signaling pathways such as PKC/MAPK, PI3K/AKT, and YAP/TAZ, which are presently considered as actionable targets. In addition, BAP1 loss, which characterizes UM metastatic progression, affects chromatin structure via histone H2A deubiquitylation that may be counteracted by histone deacetylase inhibitors. Encouraging results of preclinical studies targeting signaling molecules such as MAPK and PKC were unfortunately not confirmed in early clinical studies. Indeed, a general survey of all clinical trials applying new targeted and immune therapy to UM displayed disappointing results. This paper summarizes the most recent studies of UM-targeted therapies, analyzing the possible origins of failures. We also focus on hyperexpressed molecules involved in UM aggressiveness as potential new targets for therapy.

The BET-bromodomain inhibitor JQ1 mitigates vemurafenib drug resistance in melanoma

Inhibition of BRAF improves therapeutic efficacy of BRAF-mutant melanoma. However, drug resistance to BRAF inhibitor is inevitable, and the drug resistance mechanisms still remain to be elucidated. Here, BRAF mutant cells A375 and SK-MEL-28 were chosen and treated with BRAF inhibitor vemurafenib, and the results showed that the ERK signaling pathway was blocked in these cells. Then, vemurafenib-resistant cells were constructed, and we found that drug resistance-related gene P-gp was overexpressed in the two cell lines. In addition, the histone acetylation was significantly increased on the P-gp promoter region, which suggested that the epigenetic modification participated in the P-gp overexpression. Furthermore, JQ1, a bromodomain inhibitor, was added to the vemurafenib-resistant cells and sensitizes the vemurafenib-induced melanoma cell apoptosis. In C57BL/6 mice intravenously injected with vemurafenib-resistant melanoma cells, cotreatment of vemurafenib and JQ1 also severely suppressed melanoma lung metastasis. Taken together, our findings may have important implications for the combined use of vemurafenib and JQ1 in the therapy for melanoma treatment.

Novel therapeutic strategies and targets in advanced uveal melanoma

PURPOSE OF REVIEW

Currently, there are no U.S. Food and Drug Administration-approved or effective treatment options for advanced-stage uveal melanoma. In this article, we focus on therapeutic targets in pathways/mechanisms associated with common mutations in uveal melanoma. We review the challenges associated with targeting of these pathways and novel treatment strategies.

RECENT FINDINGS

Common mutations that promote uveal melanoma initiation and progression include alterations in G protein subunit alpha q/11 (GNAQ/GNA11) and breast cancer gene 1-associated protein 1 (BAP1). Mutant GNAQ/GNA11 induces constitutive activation of tumorigenic pathways such as extracellular signal-regulated kinase (ERK)1/2 and yes-associated protein. Inhibition of mitogen-activated protein kinase kinase (MEK) downstream of ERK1/2, however, was shown in trials to have limited clinical benefit. Recent reports suggested that combination therapies of MEK inhibition and modulators of mechanisms of drug resistance may improve tumor responses to MEK inhibitors. BAP1 has been shown to be involved in modulating chromatin dynamics and deubiquitination of proteins. Hence, epigenetic inhibitors are being investigated in BAP1 mutant uveal melanoma. However, other functions of BAP1, such as in DNA damage repair and cell cycle regulation, indicate additional targets for treatment of BAP1 mutant uveal melanoma. In addition, the frequent delayed development of uveal melanoma macrometastases is likely due to cellular dormancy mechanisms. Nuclear receptor subfamily 2, group F, member 1 and transforming growth factor beta 2 were among factors that have been shown in other cancers to induce dormant phenotypes.

SUMMARY

Findings from studies in uveal melanoma and in other cancers provide evidence for potential strategies that may be tested preclinically and clinically in advanced-stage uveal melanoma to improve treatment outcome and overall survival of patients.

The BET Bromodomain Inhibitor I-BET-151 Induces Structural and Functional Alterations of the Heart Mitochondria in Healthy Male Mice and Rats

The bromodomain and extra-terminal domain family inhibitors (BETi) are a promising new class of anticancer agents. Since numerous anticancer drugs have been correlated to cardiomyopathy, and since BETi can affect non-cancerous tissues, we aimed to investigate in healthy animals any ultrastructural BETi-induced alterations of the heart as compared to skeletal muscle. Male Wistar rats were either treated during 3 weeks with I-BET-151 (2 or 10 mg/kg/day) (W3) or treated for 3 weeks then allowed to recover for another 3 weeks (W6) (3-weeks drug washout). Male C57Bl/6J mice were only treated during 5 days (50 mg/kg/day). We demonstrated the occurrence of ultrastructural alterations and progressive destruction of cardiomyocyte mitochondria after I-BET-151 exposure. Those mitochondrial alterations were cardiac muscle-specific, since the skeletal muscles of exposed animals were similar in ultrastructure presentation to the non-exposed animals. I-BET-151 decreased the respiration rate of heart mitochondria in a dose-dependent manner. At the higher dose, it also decreased mitochondrial mass, as evidenced by reduced right ventricular citrate synthase content. I-BET-151 reduced the right and left ventricular fractional shortening. The concomitant decrease in the velocity-time-integral in both the aorta and the pulmonary artery is also suggestive of an impaired heart function. The possible context-dependent cardiac side effects of these drugs have to be appreciated. Future studies should focus on the basic mechanisms of potential cardiovascular toxicities induced by BETi and strategies to minimize these unexpected complications.

Inhibition of NF-κB-Dependent Signaling Enhances Sensitivity and Overcomes Resistance to BET Inhibition in Uveal Melanoma

Bromodomain and extraterminal protein inhibitors (BETi) are epigenetic therapies aimed to target dysregulated gene expression in cancer cells. Despite early successes of BETi in a range of malignancies, the development of drug resistance may limit their clinical application. Here, we evaluated the mechanisms of BETi resistance in uveal melanoma, a disease with little treatment options, using two approaches: a high-throughput combinatorial drug screen with the clinical BET inhibitor PLX51107 and RNA sequencing of BETi-resistant cells. NF-κB inhibitors synergistically sensitized uveal melanoma cells to PLX51107 treatment. Furthermore, genes involved in NF-κB signaling were upregulated in BETi-resistant cells, and the transcription factor CEBPD contributed to the mechanism of resistance. These findings suggest that inhibitors of NF-κB signaling may improve the efficacy of BET inhibition in patients with advanced uveal melanoma. SIGNIFICANCE: These findings provide evidence that inhibitors of NF-κB signaling synergize with BET inhibition in in vitro and in vivo models, suggesting a clinical utility of these targeted therapies in patients with uveal melanoma.

SF2523 inhibits human chondrosarcoma cell growth in vitro and in vivo

Developing novel therapeutic agents against chondrosarcoma is important. SF2523 is a PI3K-Akt-mTOR and bromodomain-containing protein 4 (BRD4) dual inhibitor. Its activity in human chondrosarcoma cells is tested. Our results show that SF2523 potently inhibited survival, proliferation and migration, and induced apoptosis activation in SW1353 cells and primary human chondrosarcoma cells. The dual inhibitor was yet non-cytotoxic to the primary human osteoblasts and OB-6 osteoblastic cells. SF2523 blocked Akt-mTOR activation and downregulated BRD4-regulated genes (Bcl-2 and c-Myc) in chondrosarcoma cells. It was more efficient in killing chondrosarcoma cells than other established PI3K-Akt-mTOR and BRD4 inhibitors, including JQ1, perifosine and OSI-027. In vivo, intraperitoneal injection of SF2523 (30 mg/kg) potently inhibited subcutaneous SW1353 xenograft tumor growth in severe combined immunodeficient mice. Akt-mTOR inhibition as well as Bcl-2 and c-Myc downregulation were detected in SF2523-treated SW1353 tumor tissues. In conclusion, targeting PI3K-Akt-mTOR and BRD4 by SF2523 potently inhibited chondrosarcoma cell growth in vitro and in vivo.

Stromal fibroblast growth factor 2 reduces the efficacy of bromodomain inhibitors in uveal melanoma

Alterations in transcriptional programs promote tumor development and progression and are targetable by bromodomain and extraterminal (BET) protein inhibitors. However, in a multi-site clinical trial testing the novel BET inhibitor, PLX51107, in solid cancer patients, liver metastases of uveal melanoma (UM) patients progressed rapidly following treatment. Mechanisms of resistance to BET inhibitors in UM are unknown. We show that fibroblast growth factor 2 (FGF2) rescued UM cells from growth inhibition by BET inhibitors, and FGF2 effects were reversible by FGF receptor (FGFR) inhibitors. BET inhibitors also increased FGFR protein expression in UM cell lines and in patient tumor samples. Hepatic stellate cells (HSCs) secrete FGF2, and HSC-conditioned medium provided resistance of UM cells to BET inhibitors. PLX51107 was ineffective in vivo, but the combination of a FGFR inhibitor, AZD4547, and PLX51107 significantly suppressed the growth of xenograft UM tumors formed from subcutaneous inoculation of UM cells with HSCs and orthotopically in the liver. These results suggest that co-targeting of FGFR signaling is required to increase the responses of metastatic UM to BET inhibitors.

Proceedings of the Association for Research in Vision and Ophthalmology and Champalimaud Foundation Ocular Oncogenesis and Oncology Conference

The 2018 Ocular Oncogenesis and Oncology Conference was held through a partnership of the Association for Research in Vision and Ophthalmology (ARVO) and the Champalimaud Foundation. Twenty-one experts from international ocular oncology centers, from the Champalimaud Clinical Centre and the Champalimaud Foundation Cancer Research Program, and from patient advocacy organizations, delivered lectures on subjects that ranged from global ocular oncology, to basic research in mechanisms of ocular malignancy, to clinical research in ocular cancers, and to anticipated future developments in the area. The scientific program of the conference covered a broad range of ocular tumors-including uveal melanoma, retinoblastoma, ocular surface tumors, and adnexal and intraocular lymphomas-and pathogenesis and management were deliberated in the context of the broader systemic cancer discipline. In considering the latest basic and clinical research developments in ocular oncogenesis and oncology, and providing the opportunity for cross-talk between ocular cancer biologists, systemic cancer biologists, ocular oncologists, systemic oncologists, patients, and patient advocates, the forum generated new knowledge and novel insights for the field. This report summarizes the content of the invited talks at the 2018 ARVO-Champalimaud Foundation Ocular Oncogenesis and Oncology Conference.

BET proteins regulate homologous recombination-mediated DNA repair: BRCAness and implications for cancer therapy

Bromodomain and Extra-Terminal (BET) proteins are historically involved in regulating gene expression and BRD4 was recently found to be involved in DNA damage regulation. Aims of our study were to assess BRD4 regulation in homologous recombination-mediated DNA repair and to explore novel clinical strategies through the combinations of the pharmacological induction of epigenetic BRCAness in BRCA1 wild-type triple negative breast cancer (TNBC) cells by means of BET inhibitors and compounds already available in clinic. Performing a dual approach (chromatin immunoprecipitation and RNA interference), the direct relationship between BRD4 and BRCA1/RAD51 expression was confirmed in TNBC cells. Moreover, BRD4 pharmacological inhibition using two BET inhibitors (JQ1 and GSK525762A) induced a dose-dependent reduction in BRCA1 and RAD51 levels and is able to hinder homologous recombination-mediated DNA damage repair, generating a BRCAness phenotype in TNBC cells. Furthermore, BET inhibition impaired the ability of TNBC cells to overcome the increase in DNA damage after platinum salts (i.e., CDDP) exposure, leading to massive cell death, and triggered synthetic lethality when combined with PARP inhibitors (i.e., AZD2281). Altogether, the present study confirms that BET proteins directly regulate the homologous recombination pathway and their inhibition induced a BRCAness phenotype in BRCA1 wild-type TNBC cells. Noteworthy, being this strategy based on drugs already available for human use, it is rapidly transferable and could potentially enable clinicians to exploit platinum salts and PARP inhibitors-based treatments in a wider population of TNBC patients and not just in a specific subgroup, after validating clinical trials.

Isocitrate dehydrogenase 1 mutation sensitizes intrahepatic cholangiocarcinoma to the BET inhibitor JQ1

Cholangiocarcinoma is a life‐threatening disease with a poor prognosis. Although genome analysis unraveled some genetic mutation profiles in cholangiocarcinoma, it remains unknown whether such genetic abnormalities relate to the effects of anticancer drugs. Mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2) are exclusively found in almost 20% of intrahepatic cholangiocarcinoma (ICC). Recently, the anticancer effects of BET inhibitors including JQ1 have been shown in various tumors. In the present study, we report that the antigrowth effect of JQ1 differs among ICC cells and IDH1 mutation sensitizes ICC cells to JQ1. RBE cells harboring IDH1 mutation was more sensitive to JQ1 than HuCCT1 or HuH28 cells with wild‐type IDH1. JQ1 induced apoptosis only in RBE cells through the upregulation of proapoptotic genes BAX and BIM. We found that the antigrowth effect was not attributed to downregulation of the MYC gene as a well‐known target of JQ1 in various cancer cells. Notably, the forced expression of mutant IDH1 successfully sensitized HuCCT1 cells to JQ1. In addition, AGI‐5198, a selective inhibitor of mutant IDH1 partially reversed the decrease in viability after JQ1 treatment and also suppressed the JQ1‐induced apoptosis in RBE cells. These data suggest that IDH1 mutation contributed to the growth inhibitory effect of JQ1 in RBE cells. Furthermore, given that the effect of mutant IDH1 was not recapitulated in glioblastoma cells, the enhancement of JQ1 sensitivity by IDH1 mutation seems to be specific for ICC cells. Our findings propose a new stratified therapeutic strategy based on IDH1 mutation in ICC.

Investigations of Structural Requirements for BRD4 Inhibitors through Ligand- and Structure-Based 3D QSAR Approaches

The bromodomain containing protein 4 (BRD4) recognizes acetylated histone proteins and plays numerous roles in the progression of a wide range of cancers, due to which it is under intense investigation as a novel anti-cancer drug target. In the present study, we performed three-dimensional quantitative structure activity relationship (3D-QSAR) molecular modeling on a series of 60 inhibitors of BRD4 protein using ligand- and structure-based alignment and different partial charges assignment methods by employing comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) approaches. The developed models were validated using various statistical methods, including non-cross validated correlation coefficient (r²), leave-one-out (LOO) cross validated correlation coefficient (q²), bootstrapping, and Fisher’s randomization test. The highly reliable and predictive CoMFA (q² = 0.569, r² = 0.979) and CoMSIA (q² = 0.500, r² = 0.982) models were obtained from a structure-based 3D-QSAR approach using Merck molecular force field (MMFF94). The best models demonstrate that electrostatic and steric fields play an important role in the biological activities of these compounds. Hence, based on the contour maps information, new compounds were designed, and their binding modes were elucidated in BRD4 protein’s active site. Further, the activities and physicochemical properties of the designed molecules were also predicted using the best 3D-QSAR models. We believe that predicted models will help us to understand the structural requirements of BRD4 protein inhibitors that belong to quinolinone and quinazolinone classes for the designing of better active compounds.

BRD4 Inhibition Is Synthetic Lethal with PARP Inhibitors through the Induction of Homologous Recombination Deficiency

Poly(ADP-ribose) polymerase inhibitors (PARPi) are selectively active in cells with homologous recombination (HR) deficiency (HRD) caused by mutations in BRCA1, BRCA2, and other pathway members. We sought small molecules that induce HRD in HR-competent cells to induce synthetic lethality with PARPi and extend the utility of PARPi. We demonstrated that inhibition of bromodomain containing 4 (BRD4) induced HRD and sensitized cells across multiple tumor lineages to PARPi regardless of BRCA1/2, TP53, RAS, or BRAF mutation status through depletion of the DNA double-stand break resection protein CtIP (C-terminal binding protein interacting protein). Importantly, BRD4 inhibitor (BRD4i) treatment reversed multiple mechanisms of resistance to PARPi. Furthermore, PARPi and BRD4i are synergistic in multiple in vivo models.

Kinome-wide transcriptional profiling of uveal melanoma reveals new vulnerabilities to targeted therapeutics

Metastatic uveal melanoma (UM) is invariably fatal, usually within a year of diagnosis. There are currently no effective therapies, and clinical studies employing kinase inhibitors have so far demonstrated limited success. This is despite common activating mutations in GNAQ/11 genes, which trigger signalling pathways that might predispose tumours to a variety of targeted drugs. In this study, we have profiled kinome expression network dynamics in various human ocular melanomas. We uncovered a shared transcriptional profile in human primary UM samples and across a variety of experimental cell-based models. The poor overall response of UM cells to FDA-approved kinase inhibitors contrasted with much higher sensitivity to the bromodomain inhibitor JQ1, a broad transcriptional repressor. Mechanistically, we identified a repressed FOXM1-dependent kinase subnetwork in JQ1-exposed cells that contained multiple cell cycle-regulated protein kinases. Consistently, we demonstrated vulnerability of UM cells to inhibitors of mitotic protein kinases within this network, including the investigational PLK1 inhibitor BI6727. We conclude that analysis of kinome-wide signalling network dynamics has the potential to reveal actionable drug targets and inhibitors of potential therapeutic benefit for UM patients.

Treatment of uveal melanoma: where are we now?

Uveal melanoma, a rare subset of melanoma, is the most common primary intraocular malignancy in adults. Despite effective primary therapy, nearly 50% of patients will develop metastatic disease. Outcomes for those with metastatic disease remain dismal due to a lack of effective therapies. The unique biology and immunology of uveal melanoma necessitates the development of dedicated management and treatment approaches. Ongoing efforts seek to optimize the efficacy of targeted therapy and immunotherapy in both the adjuvant and metastatic setting. This review provides a comprehensive, updated overview of disease biology and risk stratification, the management of primary disease, options for adjuvant therapy, and the current status of treatment strategies for metastatic disease.

Dual inhibition of BRD4 and PI3K by SF2523 suppresses human prostate cancer cell growth in vitro and in vivo

Bromodomain-containing protein 4 (BRD4) and phosphatidylinositol 3-kinase (PI3K) are both key oncogenic proteins in human prostate cancer. In the current study, we examined the anti-prostate cancer cell activity by SF2523, a BRD4 and PI3K dual inhibitor. We showed that SF2523 potently inhibited survival and proliferation of the primary human prostate cancer cells. SF2523 induced profound apoptosis activation in prostate cancer cells. The dual inhibitor was yet non-cytotoxic to the prostate epithelial cells. At the molecular level, SF2523 downregulated BRD4-regulated genes (cyclin D1, c-Myc and androgen receptor) and almost blocked AKT-S6K1 activation in prostate cancer cells. In vivo, SF2523 intraperitoneal administration at the well-tolerated dose inhibited human prostate cancer xenograft growth in severe combined immunodeficient (SCID) mice. BRD4-regulated genes (cyclin D1, c-Myc and androgen receptor) and AKT-S6K1 activation were inhibited in SF2523-treated tumors. Together, dual inhibition of BRD4 and PI3K by SF2523 suppresses human prostate cancer cell growth in vitro and in vivo.

Uveal Melanoma Cell Seeding after Transretinal Tumor Biopsy?

BACKGROUND/AIMS

To report a case and the histopathology of uveal melanoma cell seeding following transretinal tumor biopsy for a suspected uveal lesion.

METHODS

Interventional case report.

RESULTS

A 66-year-old male presented with a pigmented perilimbal episcleral lesion overlying an intraocular mass at the pars plana, 3.5 years after transretinal biopsy and ruthenium plaque brachytherapy for a choroidal melanoma at the posterior pole. The patient underwent enucleation of the eye. Histopathology confirmed a recurrence of uveal melanoma with intra- and extrascleral tumor portions. Serial sections revealed the posterior border of this newfound pars plana melanoma separated from the radiation scar by a viable and tumor-free choroidal area, thus failing to establish a continuity between secondary and primary tumor.

CONCLUSION

Transretinal tumor biopsy is of high diagnostic and prognostic value in the management of uveal lesions, but also bears the potential risk for tumor cell seeding.

Dual inhibition of BRD4 and PI3K-AKT by SF2523 suppresses human renal cell carcinoma cell growth

Bromodomain-containing protein 4 (BRD4) and PI3K-AKT are both important for renal cell carcinoma (RCC) development and progression. SF2523 is a BRD4 and PI3K-AKT dual inhibitor. The present study demonstrated that SF2523 was cytotoxic and anti-proliferative to established RCC cell lines (786-O and A498) and primary human RCC cells. SF2523 induced activation of caspase and apoptosis in RCC cells. Further, SF2523 disrupted RCC cell cycle progression and inhibited cell migration in vitro. At the signaling level, SF2523 in-activated PI3K-AKT-mTOR, and downregulated BRD4-dependent proteins, Bcl-2 and Myc, in RCC cells. Remarkably, SF2523 was more efficient than Wortmannin (the PI3K inhibitor) and JQ1 (the BRD4 specific inhibitor) in killing RCC cells. In vivo, SF2523 administration at well-tolerated doses suppressed 786-O xenograft tumor growth in severe combined immunodeficient (SCID) mice. Together, our results suggest that concurrent blockage of BRD4 and PI3K-AKT signalings by SF2523 efficiently inhibits RCC cell growth in vitro and in vivo.

BRD4 inhibition suppresses cell growth, migration and invasion of salivary adenoid cystic carcinoma

Background

Bromodomain-containing protein 4 (BRD4) inhibition is a new therapeutic strategy for many malignancies. In this study, we aimed to explore the effect of BRD4 inhibition by JQ1 on in vitro cell growth, migration and invasion of salivary adenoid cystic carcinoma (SACC).

Methods

The human normal epithelial cells and SACC cells (ACC-LM and ACC-83) were treated with JQ1 at concentrations of 0, 0.1, 0.5 or 1 μM. Cell Counting Kit-8 (CCK-8) assay was performed to evaluate cell proliferation. Cell apoptosis and cell cycle distribution was evaluated by Flow cytometry. Immunofluorescence staining was used to examine the expression of BRD4 in SACC cells. The quantitative real-time polymerase chain reaction (qRT-PCR) assay and western blot assay were performed to examine messenger RNA (mRNA) and protein levels in SACC cells. Wound-healing assay and transwell assay were used to evaluate the activities of migration and invasion of SACC cells.

Results

JQ1 exhibits no adverse effects on proliferation, cell cycle and cell apoptosis of the normal human epithelial cells, while suppressed proliferation and cell cycle, and induced apoptosis of SACC cells, down-regulated the mRNA and protein levels of BRD4 in SACC cells, meanwhile reduced protein expressions of c-myc and BCL-2, two known target genes of BRD4. Moreover, JQ1 inhibited SACC cell migration and invasion by regulating key epithelial–mesenchymal transition (EMT) characteristics including E-cadherin, Vimentin and Twist.

Conclusions

BRD4 is an important transcription factor in SACC and BRD4 inhibition by JQ1 may be a new strategy for SACC treatment.

MYC-Master Regulator of the Cancer Epigenome and Transcriptome

Overexpression of MYC is a hallmark of many human cancers. The MYC oncogene has long been thought to execute its neoplastic functions by acting as a classic transcription factor, deregulating the expression of a large number of specific target genes. However, MYC’s influence on many of these target genes is rather modest and there is little overlap between MYC regulated genes in different cell types, leaving many mechanistic questions unanswered. Recent advances in the field challenge the dogma further, revealing a role for MYC that extends beyond the traditional concept of a sequence-specific transcription factor. In this article, we review MYC’s function as a regulator of the cancer epigenome and transcriptome. We outline our current understanding of how MYC regulates chromatin structure in both a site-specific and genome-wide fashion, and highlight the implications for therapeutic strategies for cancers with high MYC expression.

New concepts in the molecular understanding of uveal melanoma

PURPOSE OF REVIEW

Uveal melanoma is the most common primary intraocular malignancy, and its metastases are deadly. Significant work has been done to elucidate the molecular framework that causes uveal melanoma development and metastasis. This review is intended to highlight the most recent breakthroughs in the molecular understanding of uveal melanoma.

RECENT FINDINGS

Monosomy of chromosome 3 and class 2 gene-expression profile are well-known indicators of melanoma metastasis. However, some patients with disomy 3 and class 1 gene expression profiling (GEP) still develop metastasis. Disomy 3 tumors may be further classified based upon the presence of an SF3B1 mutation. The role of SF3B1 gene is unclear at this time but may be related to the development of late metastases among disomy 3 uveal melanoma. Class 1 GEP tumors have recently been subdivided into class 1a and class 1b, with class 1b tumors carrying a slightly higher risk of metastasis. Among patients with either class 1 or class 2 GEP, the expression of preferentially expressed antigen in melanoma (PRAME) is an independent risk factor for the development of metastasis. Mutation of GNAQ is the most commonly observed mutation in uveal melanoma, regardless of chromosome 3 status or GEP class. Inhibitors or GNAQ may be targets for therapeutic intervention in uveal melanoma. MicroRNA molecules are small noncoding RNA molecules that have been recently demonstrated to function in RNA silencing and posttranscriptional regulation of gene expression. These molecules may play a role in the development of uveal melanoma metastasis.

SUMMARY

New findings such as the presence or absence of PRAME, mutations in the SF3B1 gene and microRNA dysregulation have added new layers to our understanding of uveal melanoma. These new concepts will enhance our ability to prognosticate tumor metastasis and may provide targets for therapeutic intervention.

The biology of uveal melanoma

Uveal melanoma (UM), a rare cancer of the eye, is distinct from cutaneous melanoma by its etiology, the mutation frequency and profile, and its clinical behavior including resistance to targeted therapy and immune checkpoint blockers. Primary disease is efficiently controlled by surgery or radiation therapy, but about half of UMs develop distant metastasis mostly to the liver. Survival of patients with metastasis is below 1 year and has not improved in decades. Recent years have brought a deep understanding of UM biology characterized by initiating mutations in the G proteins GNAQ and GNA11. Cytogenetic alterations, in particular monosomy of chromosome 3 and amplification of the long arm of chromosome 8, and mutation of the BRCA1-associated protein 1, BAP1, a tumor suppressor gene, or the splicing factor SF3B1 determine UM metastasis. Cytogenetic and molecular profiling allow for a very precise prognostication that is still not matched by efficacious adjuvant therapies. G protein signaling has been shown to activate the YAP/TAZ pathway independent of HIPPO, and conventional signaling via the mitogen-activated kinase pathway probably also contributes to UM development and progression. Several lines of evidence indicate that inflammation and macrophages play a pro-tumor role in UM and in its hepatic metastases. UM cells benefit from the immune privilege in the eye and may adopt several mechanisms involved in this privilege for tumor escape that act even after leaving the niche. Here, we review the current knowledge of the biology of UM and discuss recent approaches to UM treatment.

Strategies to Inhibit Myc and Their Clinical Applicability

Myc is an oncogene deregulated in most-perhaps all-human cancers. Each Myc family member, c-, L-, and N-Myc, has been connected to tumor progression and maintenance. Myc is recognized as a "most wanted" target for cancer therapy, but has for many years been considered undruggable, mainly due to its nuclear localization, lack of a defined ligand binding site, and physiological function essential to the maintenance of normal tissues. The challenge of identifying a pharmacophore capable of overcoming these hurdles is reflected in the current absence of a clinically-viable Myc inhibitor. The first attempts to inhibit Myc used antisense technology some three decades ago, followed by small molecule inhibitors discovered through "classical" compound library screens. Notable breakthroughs proving the feasibility of systemic Myc inhibition were made with the Myc dominant negative mutant Omomyc, showing both the great promise in targeting this infamous oncogene for cancer treatment as well as allaying fears about the deleterious side effects that Myc inhibition might have on normal proliferating tissues. During this time many other strategies have appeared in an attempt to drug the undruggable, including direct and indirect targeting, knockdown, protein/protein and DNA interaction inhibitors, and translation and expression regulation. The inhibitors range from traditional small molecules to natural chemicals, to RNA and antisense, to peptides and miniproteins. Here, we briefly describe the many approaches taken so far, with a particular focus on their potential clinical applicability.

Advances in the Treatment of Advanced Extracutaneous Melanomas and Nonmelanoma Skin Cancers

Cutaneous malignancies make up the greatest proportion of all human cancers and include melanomas as well as nonmelanoma skin cancers (NMSCs) such as basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cSCC), as well as less common Merkel cell carcinoma (MCC), cutaneous lymphomas, cutaneous adnexal tumors, Kaposi sarcomas, and other sarcomas. Each of these NMSCs differ significantly in biology, clinical behavior, and optimal treatment recommendations from each other and from cutaneous melanoma. Similarly, less common extracutaneous melanomas, such as mucosal (MMs) and uveal (UMs), are unique biologic and clinical entities that require distinct diagnostic and management considerations. In this review, we summarize recent advances in biology and treatment of extracutaneous melanomas and NMSCs, including MMs, UMs, cSCC, BCC, and MCC.

Epigenetic modulators as therapeutic targets in prostate cancer

Prostate cancer is one of the most common non-cutaneous malignancies among men worldwide. Epigenetic aberrations, including changes in DNA methylation patterns and/or histone modifications, are key drivers of prostate carcinogenesis. These epigenetic defects might be due to deregulated function and/or expression of the epigenetic machinery, affecting the expression of several important genes. Remarkably, epigenetic modifications are reversible and numerous compounds that target the epigenetic enzymes and regulatory proteins were reported to be effective in cancer growth control. In fact, some of these drugs are already being tested in clinical trials. This review discusses the most important epigenetic alterations in prostate cancer, highlighting the role of epigenetic modulating compounds in pre-clinical and clinical trials as potential therapeutic agents for prostate cancer management.

Uveal Melanoma Cell Lines: Where do they come from? (An American Ophthalmological Society Thesis)

PURPOSE

To determine whether some of the most often used uveal melanoma cell lines resemble their original tumor.

METHODS

Analysis of the literature, patient charts, histopathology, mutations, chromosome status, HLA type, and expression of melanocyte markers on cell lines and their primary tumors. We examined five cell lines and the primary tumors from which they were derived.

RESULTS

Four of the five examined primary tumors were unusual: one occupied the orbit, two were recurrences after prior irradiation, and one developed in an eye with a nevus of Ota. One cell line did not contain the GNA11 mutation, but it was present in the primary tumor. Three of the primary tumors had monosomy 3 (two of these lacked BAP1 expression); however, all five cell lines showed disomy 3 and BAP1 expression. All of the cell lines had gain of 8q. Two cell lines lacked expression of melanocyte markers, although these were present in the corresponding primary tumor.

CONCLUSIONS

All cell lines could be traced back to their original uveal melanoma. Four of the five primary tumors were unusual. Cell lines often differed from their primary tumor in chromosome status and melanocyte markers. However, their specific chromosome aberrations and capacity to continue proliferation characterize them as uveal melanoma cell lines.