Overexpression of the KIT/SCF in uveal melanoma does not translate into clinical efficacy of imatinib mesylate

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.

c-Kit Receptors as a Therapeutic Target in Cancer: Current Insights

c-Kit is a type III receptor tyrosine kinase (RTK) that has an essential role in various biological functions including gametogenesis, melanogenesis, hematopoiesis, cell survival, and apoptosis. c-KIT aberrations, either overexpression or loss-of-function mutations, have been implicated in the pathogenesis and development of many cancers, including gastrointestinal stromal tumors, mastocytosis, acute myeloid leukemia, breast, thyroid, and colorectal cancer, making c-KIT an attractive molecular target for the treatment of cancers. Therefore, a lot of effort has been put into investigating the utility of tyrosine kinase inhibitors for the management of c-KIT mutated tumors. This review of the literature illustrates the role of c-KIT mutations in many cancers, aiming to provide insights into the role of TKIs as a therapeutic option for cancer patients with c-KIT aberrations. In conclusion, c-KIT is implicated in different types of cancer, and it could be a successful molecular target; however, proper detection of the underlying mutation type is required before starting the appropriate personalized therapy.

The Genomic Landscape of Melanoma and Its Therapeutic Implications

Melanoma is one of the most aggressive malignancies of the skin. The genetic composition of melanoma is complex and varies among different subtypes. With the aid of recent technologies such as next generation sequencing and single-cell sequencing, our understanding of the genomic landscape of melanoma and its tumor microenvironment has become increasingly clear. These advances may provide explanation to the heterogenic treatment outcomes of melanoma patients under current therapeutic guidelines and provide further insights to the development of potential new therapeutic targets. Here, we provide a comprehensive review on the genetics related to melanoma tumorigenesis, metastasis, and prognosis. We also review the genetics affecting the melanoma tumor microenvironment and its relation to tumor progression and treatment.

Advances in the clinical management of uveal melanoma

Melanomas arising in the uveal tract of the eye are a rare form of the disease with a biology and clinical phenotype distinct from their more common cutaneous counterparts. Treatment of primary uveal melanoma with radiotherapy, enucleation or other modalities achieves local control in more than 90% of patients, although 40% or more ultimately develop distant metastases, most commonly in the liver. Until January 2022, no systemic therapy had received regulatory approval for patients with metastatic uveal melanoma, and these patients have historically had a dismal prognosis owing to the limited efficacy of the available treatments. A series of seminal studies over the past two decades have identified highly prevalent early, tumour-initiating oncogenic genomic aberrations, later recurring prognostic alterations and immunological features that characterize uveal melanoma. These advances have driven the development of a number of novel emerging treatments, including tebentafusp, the first systemic therapy to achieve regulatory approval for this disease. In this Review, our multidisciplinary and international group of authors summarize the biology of uveal melanoma, management of primary disease and surveillance strategies to detect recurrent disease, and then focus on the current standard and emerging regional and systemic treatment approaches for metastatic uveal melanoma.

Metastatic uveal melanoma: The final frontier

Treatment of primary intraocular uveal melanoma has developed considerably, its driver genes are largely unraveled, and the ways to assess its risk for metastases are very precise, being based on an international staging system and genetic data. Unfortunately, the risk of distant metastases, which emerge in approximately one half of all patients, is unaltered. Metastases are the leading single cause of death after uveal melanoma is diagnosed, yet no consensus exists regarding surveillance, staging, and treatment of disseminated disease, and survival has not improved until recently. The final frontier in conquering uveal melanoma lies in solving these issues to cure metastatic disease. Most studies on metastatic uveal melanoma are small, uncontrolled, retrospective, and do not report staging. Meta-analyses confirm a median overall survival of 10-13 months, and a cure rate that approaches nil, although survival exceeding 5 years is possible, estimated 2% either with first-line treatment or with best supportive care. Hepatic ultrasonography and magnetic resonance imaging as surveillance methods have a sensitivity of 95-100% and 83-100%, respectively, to detect metastases without radiation hazard according to prevailing evidence, but computed tomography is necessary for staging. No blood-based tests additional to liver function tests are generally accepted. Three validated staging systems predict, each in defined situations, overall survival after metastasis. Their essential components include measures of tumor burden, liver function, and performance status or metastasis free interval. Age and gender may additionally influence survival. Exceptional mutational events in metastases may make them susceptible to checkpoint inhibitors. In a large meta-analysis, surgical treatment was associated with 6 months longer median overall survival as compared to conventional chemotherapy and, recently, tebentafusp as first-line treatment at the first interim analysis of a randomized phase III trial likewise provided a 6 months longer median overall survival compared to investigator's choice, mostly pembrolizumab; these treatments currently apply to selected patients. Promoting dormancy of micrometastases, harmonizing surveillance protocols, promoting staging, identifying predictive factors, initiating controlled clinical trials, and standardizing reporting will be critical steppingstones in reaching the final frontier of curing metastatic uveal melanoma.

Supervised learning with word embeddings derived from PubMed captures latent knowledge about protein kinases and cancer

Inhibiting protein kinases (PKs) that cause cancers has been an important topic in cancer therapy for years. So far, almost 8% of >530 PKs have been targeted by FDA-approved medications, and around 150 protein kinase inhibitors (PKIs) have been tested in clinical trials. We present an approach based on natural language processing and machine learning to investigate the relations between PKs and cancers, predicting PKs whose inhibition would be efficacious to treat a certain cancer. Our approach represents PKs and cancers as semantically meaningful 100-dimensional vectors based on word and concept neighborhoods in PubMed abstracts. We use information about phase I-IV trials in ClinicalTrials.gov to construct a training set for random forest classification. Our results with historical data show that associations between PKs and specific cancers can be predicted years in advance with good accuracy. Our tool can be used to predict the relevance of inhibiting PKs for specific cancers and to support the design of well-focused clinical trials to discover novel PKIs for cancer therapy.

KIT Expression Is Regulated by DNA Methylation in Uveal Melanoma Tumors

Uveal melanoma (UM) is an ocular tumor with a dismal prognosis. Despite the availability of precise molecular and cytogenetic techniques, clinicopathologic features with limited accuracy are widely used to predict metastatic potential. In 51 UM tissues, we assessed a correlation between the expression of nine proteins evaluated by immunohistochemistry (IHC) (Melan-A, S100, HMB45, Cyclin D1, Ki-67, p53, KIT, BCL2, and AIFM1) and the presence of UM-specific chromosomal rearrangements measured by multiplex ligation-dependent probe amplification (MLPA), to find IHC markers with increased prognostic information. Furthermore, mRNA expression and DNA methylation values were extracted from the whole-genome data, achieved by analyzing 22 fresh frozen UM tissues. KIT positivity was associated with monosomy 3, increasing the risk of poor prognosis more than 17-fold (95% CI 1.53–198.69, p = 0.021). A strong negative correlation was identified between mRNA expression and DNA methylation values for 12 of 20 analyzed positions, five located in regulatory regions of the KIT gene (r = −0.658, p = 0.001; r = −0.662, p = 0.001; r = −0.816; p < 0.001; r = −0.689, p = 0.001; r = −0.809, p < 0.001, respectively). DNA methylation β values were also inversely associated with KIT protein expression (p = 0.001; p = 0.001; p = 0.015; p = 0.025; p = 0.002). Our findings, showing epigenetic deregulation of KIT expression, may contribute to understanding the past failure to therapeutically target KIT in UM.

New Therapeutic Perspectives in the Treatment of Uveal Melanoma: A Systematic Review

Uveal melanoma (UM) is a rare disease, but the most common primary intraocular cancer, mostly localized in the choroid. Currently, the first-line treatment options for UM are radiation therapy, resection, and enucleation. However, although these treatments could potentially be curative, half of all patients will develop metastatic disease, whose prognosis is still poor. Indeed, effective therapeutic options for patients with advanced or metastatic disease are still lacking. Recently, the development of new treatment modalities with a lower incidence of adverse events, a better disease control rate, and new therapeutic approaches, have merged as new potential and promising therapeutic strategies. Additionally, several clinical trials are ongoing to find new therapeutic options, mainly for those with metastatic disease. Many interventions are still in the preliminary phases of clinical development, being investigated in phase I trial or phase I/II. The success of these trials could be crucial for changing the prognosis of patients with advanced/metastatic UM. In this systematic review, we analyzed all emerging and available literature on the new perspectives in the treatment of UM and patient outcomes; furthermore, their current limitations and more common adverse events are summarized.

Systemic and liver-directed therapies in metastatic uveal melanoma: state-of-the-art and novel perspectives

Metastatic uveal melanoma (MUM) is the most common form of noncutaneous melanoma. It is different from its cutaneous counterpart and is characterized by a very poor prognosis. Despite groundbreaking improvements in the treatment of cutaneous melanoma, there have been few advances in the treatment of MUM, and standard treatments for MUM have not been defined. We performed a systematic review focusing our attention on all interventional studies, ongoing or already published, concerning the treatment of MUM. We present results from studies of chemotherapy, targeted therapy, immunotherapy and liver-directed therapies. Although the results in this setting have been disappointing until now, trials investigating novel immunotherapeutic strategies alone and in combination with targeted agents and liver-directed therapies are ongoing.

Hypoxia-dependent drivers of melanoma progression

Hypoxia, a condition of low oxygen availability, is a hallmark of tumour microenvironment and promotes cancer progression and resistance to therapy. Many studies reported the essential role of hypoxia in regulating invasiveness, angiogenesis, vasculogenic mimicry and response to therapy in melanoma. Melanoma is an aggressive cancer originating from melanocytes located in the skin (cutaneous melanoma), in the uveal tract of the eye (uveal melanoma) or in mucosal membranes (mucosal melanoma). These three subtypes of melanoma represent distinct neoplasms in terms of biology, epidemiology, aetiology, molecular profile and clinical features.In this review, the latest progress in hypoxia-regulated pathways involved in the development and progression of all melanoma subtypes were discussed. We also summarized current knowledge on preclinical studies with drugs targeting Hypoxia-Inducible Factor-1, angiogenesis or vasculogenic mimicry. Finally, we described available evidence on clinical studies investigating the use of Hypoxia-Inducible Factor-1 inhibitors or antiangiogenic drugs, alone or in combination with other strategies, in metastatic and adjuvant settings of cutaneous, uveal and mucosal melanoma.Hypoxia-Inducible Factor-independent pathways have been also reported to regulate melanoma progression, but this issue is beyond the scope of this review.As evident from the numerous studies discussed in this review, the increasing knowledge of hypoxia-regulated pathways in melanoma progression and the promising results obtained from novel antiangiogenic therapies, could offer new perspectives in clinical practice in order to improve survival outcomes of melanoma patients.

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.

Molecular Insights and Emerging Strategies for Treatment of Metastatic Uveal Melanoma

Uveal melanoma (UM) is the most common intraocular cancer. In recent decades, major advances have been achieved in the diagnosis and prognosis of UM allowing for tailored treatments. However, nearly 50% of patients still develop metastatic disease with survival rates of less than 1 year. There is currently no standard of adjuvant and metastatic treatment in UM, and available therapies are ineffective resulting from cutaneous melanoma protocols. Advances and novel treatment options including liver-directed therapies, immunotherapy, and targeted-therapy have been investigated in UM-dedicated clinical trials on single compounds or combinational therapies, with promising results. Therapies aimed at prolonging or targeting metastatic tumor dormancy provided encouraging results in other cancers, and need to be explored in UM. In this review, the latest progress in the diagnosis, prognosis, and treatment of UM in adjuvant and metastatic settings are discussed. In addition, novel insights into tumor genetics, biology and immunology, and the mechanisms underlying metastatic dormancy are discussed. As evident from the numerous studies discussed in this review, the increasing knowledge of this disease and the promising results from testing of novel individualized therapies could offer future perspectives for translating in clinical use.

Treatment of Metastatic Uveal Melanoma: Systematic Review

INTRODUCTION

More than 50% of patients with uveal melanoma end up developing metastases. Currently, there is no standard first-line treatment that facilitates proper management of the metastatic disease.

METHODS

A systematic review of the last 40 years in PubMed with an exhaustive and strict selection of studies was conducted, in which the unit of measurement was overall survival (OS) expressed in Kaplan-Meier curves or numerically.

RESULTS

After the selection process, 110 articles were included. Regional therapies, such as intra-arterial liver chemotherapy (OS: 2, 9-22 months), isolated liver perfusion (OS: 9, 6-27, 4 months), or selective internal radiation therapy (OS: 18 months in monotherapy and 26 months in combination with other therapies) showed some superiority when compared to systemic therapies, such as chemotherapy (OS: 4, 6-17 months), immunotherapy (OS: 5-19, 1 month), immunosuppression (OS: 11 months), or targeted therapy (OS: 6-12 months), without being significant.

CONCLUSIONS

The results of this review suggest that there are no important differences in OS when comparing the different current treatment modalities. Most of the differences found seem to be explained by the heterogenicity of the different studies and the presence of biases in their design, rather than actual extensions of patient survival.

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.

Chondroitin polymerizing factor (CHPF) promotes development of malignant melanoma through regulation of CDK1

Chondroitin polymerizing factor (CHPF) is an important member of glycosyltransferases involved in the biosynthesis of chondroitin sulfate (CS). However, the relationship between CHPF and malignant melanoma (MM) is still unknown. In this study, it was demonstrated that CHPF was up-regulated in MM tissues compared with the adjacent normal skin tissues and its high expression was correlated with more advanced T stage. Further investigations indicated that the over-expression/knockdown of CHPF could promote/inhibit proliferation, colony formation and migration of MM cells, while inhibiting/promoting cell apoptosis. Moreover, knockdown of CHPF could also suppress tumorigenicity of MM cells in vivo. RNA-sequencing followed by Ingenuity pathway analysis (IPA) was performed for exploring downstream of CHPF and identified CDK1 as the potential target. Furthermore, our study revealed that knockdown of CDK1 could inhibit development of MM in vitro, and alleviate the CHPF over-expression induced promotion of MM. In conclusion, our study showed, as the first time, CHPF as a tumor promotor for MM, whose function was carried out probably through the regulation of CDK1.

Uveal Melanoma, Angiogenesis and Immunotherapy, Is There Any Hope?

Uveal melanoma is considered a rare disease but it is the most common intraocular malignancy in adults. Local treatments are effective, but the systemic recurrence rate is unacceptably high. Moreover, once metastasis have developed the prognosis is poor, with a 5-year survival rate of less than 5%, and systemic therapies, including immunotherapy, have rendered poor results. The tumour biology is complex, but angiogenesis is a highly important pathway in these tumours. Vasculogenic mimicry, the ability of melanomas to generate vascular channels independently of endothelial cells, could play an important role, but no effective therapy targeting this process has been developed so far. Angiogenesis modulates the tumour microenvironment of melanomas, and a close interplay is established between them. Therefore, combining immune strategies with drugs targeting angiogenesis offers a new therapeutic paradigm. In preclinical studies, these approaches effectively target these tumours, and a phase I clinical study has shown encouraging results in cutaneous melanomas. In this review, we will discuss the importance of angiogenesis in uveal melanoma, with a special focus on vasculogenic mimicry, and describe the interplay between angiogenesis and the tumour microenvironment. In addition, we will suggest future therapeutic approaches based on these observations and mention ways in which to potentially enhance current treatments.

Targeting tyrosine kinases for treatment of ocular tumors

Uveal melanoma is the most common intraocular primary malignant tumor in adults, and retinoblastoma is the one in children. Current mainstay treatment options include chemotherapy using conventional drugs and enucleation, the total removal of the eyeball. Targeted therapies based on profound understanding of molecular mechanisms of ocular tumors may increase the possibility of preserving the eyeball and the vision. Tyrosine kinases, which modulate signaling pathways regarding various cellular functions including proliferation, differentiation, and attachment, are one of the attractive targets for targeted therapies against uveal melanoma and retinoblastoma. In this review, the roles of both types of tyrosine kinases, receptor tyrosine kinases and non-receptor tyrosine kinases, were summarized in relation with ocular tumors. Although the conventional treatment options for uveal melanoma and retinoblastoma are radiotherapy and chemotherapy, respectively, specific tyrosine kinase inhibitors will enhance our armamentarium against them by controlling cancer-associated signaling pathways related to tyrosine kinases. This review can be a stepping stone for widening treatment options and realizing targeted therapies against uveal melanoma and retinoblastoma.

Personalized Medicine in Malignant Melanoma: Towards Patient Tailored Treatment

Despite enormous international efforts, skin melanoma is still a major clinical challenge. Melanoma takes a top place among the most common cancer types and it has one of the most rapidly increasing incidences in many countries around the world. Until recent years, there have been limited options for effective systemic treatment of disseminated melanoma. However, lately, we have experienced a rapid advancement in the understanding of the biology and molecular background of the disease. This has led to new molecular classifications and the development of more effective targeted therapies adapted to distinct melanoma subtypes. Not only are these treatments more effective but they can be rationally prescribed to the patients standing to benefit. As such, melanoma management has now become one of the most developed for personalized medicine. The aim of the present paper is to summarize the current knowledge on melanoma molecular classification, predictive markers, combination therapies, as well as emerging new treatments.

Uveal Melanoma: A Review of the Literature

Melanomas affecting different components of the uvea occur with differing frequencies and clinical presentations. Uveal melanoma is diagnosed via funduscopic exam and ancillary tests. These lesions may present with visual findings or incidental findings on physical exam. Metastasis occurs in approximately half of all patients with primary uveal melanoma. The liver is the most common site of metastasis. Enucleation was at one time considered the definitive local treatment for primary uveal melanoma, but has been largely replaced by other therapeutic procedures that aim to prevent metastasis while preserving vision. Unfortunately, metastasis of uveal melanoma almost always proves to be fatal. The current treatment of metastatic uveal melanoma is limited by the intrinsic resistance of uveal melanoma to conventional systemic therapies. Advancements in molecular biology have resulted in the identification of a number of promising prognostic and therapeutic targets. Early detection and therapy are important factors in disease survival. It is imperative that the treating physician be familiar with the clinical features of uveal melanoma and distinguish it from mimickers in order to ensure effective and timely treatment.

Long-term survival in a patient with unresectable liver metastases from uveal melanoma treated with transarterial chemoembolization with irinotecan eluting beads - case report and review of literature

Introduction

Treatment of unresectable liver metastases (LM) from uveal melanoma (UM) remains a major clinical challenge. Systemic chemotherapy and chemoimmunotherapy regimens extrapolated from cutaneous melanoma are considered to be ineffective in therapy of metastases from uveal melanoma. Studies suggest that the progression of hepatic metastases rather than the primary tumor or metastases in other organs determines survival.

Case report

We report a case of transarterial chemoembolization of 57-year-old man diagnosed with unresectable liver metastases from uveal melanoma with irinotecan eluting beads. Therapy resulted in long progression free survival and overall survival, 41 months and 45 months after diagnosis of metastatic disease respectively. Patient did not experience any major side effects of the therapy. Follow-up CTs indicate stable disease in mRECIST criteria and partial response in CHOI criteria.

Conclusions

Transarterial chemoembolization with drug eluting beads loaded with irinotecan may be an effective treatment of unresectable liver metastases from uveal melanoma.

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.

Uveal melanoma: From diagnosis to treatment and the science in between

Melanomas of the choroid, ciliary body, and iris of the eye are collectively known as uveal melanomas. These cancers represent 5% of all melanoma diagnoses in the United States, and their age-adjusted risk is 5 per 1 million population. These less frequent melanomas are dissimilar to their more common cutaneous melanoma relative, with differing risk factors, primary treatment, anatomic spread, molecular changes, and responses to systemic therapy. Once uveal melanoma becomes metastatic, therapy options are limited and are often extrapolated from cutaneous melanoma therapies despite the routine exclusion of patients with uveal melanoma from clinical trials. Clinical trials directed at uveal melanoma have been completed or are in progress, and data from these well designed investigations will help guide future directions in this orphan disease. Cancer 2016;122:2299-2312. © 2016 American Cancer Society.

Upcoming translational challenges for uveal melanoma

The past few years have witnessed major advances in the understanding of the molecular landscape of uveal melanoma (UM). The discovery of a mutational background that is completely different from the one of skin melanoma has granted to UM a stand-alone status. The absence of effective therapy for metastatic disease offers now a chessboard for targeted therapy but at the same time urges preclinical science to develop accordingly, to guide the use of economical resources to the best profit of patients. This review describes the current knowledge on the biology of this disease and discusses the challenges that must be undertaken to translate this knowledge into real benefit for patients.

Treatment of metastatic uveal melanoma with intravenous fotemustine

The purpose of the present study was to retrospectively evaluate the safety and activity of intravenous fotemustine in patients with metastatic uveal melanoma. We report on a series of 25 consecutive patients diagnosed with metastatic uveal melanoma. Fotemustine was administered intravenously as a first-line treatment to all patients. Thrombocytopenia and leukopenia (any grade) were observed in 60 and 52% of patients, respectively. Only two patients discontinued treatment because of toxicity (G3 thrombocytopenia), whereas all other patients were discontinued for progressive disease. Two partial responses were observed. Nine patients had stable disease (disease control rate=44%). The median survival duration was 13.9 months, and the 1-year survival rate was 60%. Intravenous fotemustine is well tolerated and could improve the outcome of metastatic uveal melanoma patients with or without liver involvement, although a randomized prospective trial is required to confirm these results.

Pathways and therapeutic targets in melanoma

This review aims to summarize the current knowledge of molecular pathways and their clinical relevance in melanoma. Metastatic melanoma was a grim diagnosis, but in recent years tremendous advances have been made in treatments. Chemotherapy provided little benefit in these patients, but development of targeted and new immune approaches made radical changes in prognosis. This would not have happened without remarkable advances in understanding the biology of disease and tremendous progress in the genomic (and other "omics") scale analyses of tumors. The big problems facing the field are no longer focused exclusively on the development of new treatment modalities, though this is a very busy area of clinical research. The focus shifted now to understanding and overcoming resistance to targeted therapies, and understanding the underlying causes of the heterogeneous responses to immune therapy.

Mechanisms of resistance to imatinib mesylate in KIT-positive metastatic uveal melanoma

Imatinib mesylate is used in targeted therapy of cancer to inhibit type III tyrosine kinase receptors, such as KIT and platelet-derived growth factor receptors (PDGFRs). Expression of KIT in uveal melanoma (UM) suggests that this receptor may be the target of imatinib mesylate therapy. However, phase II multicenter clinical studies have shown no effect of imatinib mesylate in patients with unresectable liver metastases of UM. We therefore investigated which molecular mechanisms promote imatinib mesylate-resistance in metastatic UM. Expression of KIT, stem cell factor (SCF), PDGFRα and PDGFRβ, was analyzed by RT-PCR, immunostaining, and Western blot in twenty-four samples of UM liver metastases, as well as UM primary tumor and metastatic cell lines. Soluble SCF was quantified in UM cell lines using enzyme-linked immunosorbent assay. Cell viability of UM cell lines treated with imatinib mesylate and grown in SCF-supplemented medium or in microvascular endothelial cells-conditioned medium was studied by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assays. UM liver metastases and cell lines expressed KIT and SCF, but not the PDGFRs. Ninety-five percent of liver metastases expressed KIT at the protein level, but PDGFRs were not detected in these samples. Imatinib mesylate reduced the viability of UM metastatic cell lines in a concentration-dependent manner, but an increased resistance to this drug was observed when cells were incubated in SCF-supplemented or microvascular endothelial cells-conditioned medium. This study provides evidence that tumor microenvironment cytokines such as SCF may promote resistance to imatinib mesylate in metastatic UM.

Metastatic melanoma to the liver: a contemporary and comprehensive review of surgical, systemic, and regional therapeutic options

Effective management of hepatic metastases from ocular and cutaneous melanoma remains a major therapeutic challenge. Treatment options include hepatic resection, hepatic intra-arterial (HIA) chemotherapy, chemoembolization, and hepatic perfusions. Evaluating the efficacy of these interventions is limited by the retrospective nature of most of the data, although controlled phase 3 studies are starting to emerge. Studies of hepatic resection are strongly suggestive of a survival benefit following surgery in selected patients. Effective systemic agents for metastatic cutaneous melanoma are available and supported by randomized controlled phase 3 trials. In contrast, no active systemic treatment has yet been identified for metastatic ocular melanoma. HIA and intravenous delivery of fotemustine have been compared in a randomized phase 3 trial in patients with unresectable metastases from melanoma, but no differences between the 2 approaches were observed. Hepatic arterial chemoembolization appears only to be moderately effective according to uncontrolled studies; targeting patients with less liver involvement may improve outcomes. A recent phase 3 study showed a significant improvement in hepatic progression-free survival with percutaneous hepatic perfusion compared with best alternative care in patients with metastatic melanoma; however, the overall survival analysis was confounded by crossover of control patients to active treatment. In conclusion, hepatic resection offers the possibility of long-term survival in carefully selected patients with liver-limited metastases from melanoma. In patients with unresectable cutaneous melanoma, effective systemic therapy is the best treatment option. For patients with unresectable ocular melanoma, regional treatments are likely to assume a greater role until effective systemic treatments are identified.

Systemic treatment of metastatic uveal melanoma: review of literature and future perspectives

Up to 50% of patients with uveal melanoma develop metastatic disease with poor prognosis. Regional, mainly liver-directed, therapies may induce limited tumor responses but do not improve overall survival. Response rates of metastatic uveal melanoma (MUM) to systemic chemotherapy are poor. Insights into the molecular biology of MUM recently led to investigation of new drugs. In this study, to compare response rates of systemic treatment for MUM we searched Pubmed/Web of Knowledge databases and ASCO website (1980-2013) for "metastatic/uveal/melanoma" and "melanoma/eye." Forty studies (one case series, three phase I, five pilot, 22 nonrandomized, and two randomized phase II, one randomized phase III study, data of three expanded access programs, three retrospective studies) with 841 evaluable patients were included in the numeric outcome analysis. Complete or partial remissions were observed in 39/841 patients (overall response rate [ORR] 4.6%; 95% confidence intervals [CI] 3.3-6.3%), no responses were observed in 22/40 studies. Progression-free survival ranged from 1.8 to 7.2, median overall survival from 5.2 to 19.0 months as reported in 21/40 and 26/40 studies, respectively. Best responses were seen for chemoimmunotherapy (ORR 10.3%; 95% CI 4.8-18.7%) though mainly in first-line patients. Immunotherapy with ipilimumab, antiangiogenetic approaches, and kinase inhibitors have not yet proven to be superior to chemotherapy. MEK inhibitors are currently investigated in a phase II trial with promising preliminary data. Despite new insights into genetic and molecular background of MUM, satisfying systemic treatment approaches are currently lacking. Study results of innovative treatment strategies are urgently awaited.

Evidence of epidermal growth factor receptor expression in uveal melanoma: inhibition of epidermal growth factor-mediated signalling by Gefitinib and Cetuximab triggered antibody-dependent cellular cytotoxicity

Despite advances in surgery and radiotherapy of uveal melanoma (UM), many patients develop distant metastases that poorly respond to therapy. Improved therapies for the metastatic disease are therefore urgently needed. Expression of the epidermal growth factor receptor (EGFR), a target of kinase inhibitors and humanised antibodies in use for several cancers, had been reported. Forty-eight human UMs were analysed by expression profiling. Signalling was tested in three EGFR expressing UM cell lines by Western blotting using phosphorylation specific antibodies for EGFR and the downstream mediators AKT (v-akt murine thymoma viral oncogene homolog) and extracellular signal-regulated kinase (ERK). Evidence for signalling in tumours was obtained through the application of a UM-specific EGF-signature. The EGFR specific kinase inhibitor, Gefitinib and the humanised monoclonal antibody, Cetuximab, were tested for their effect on EGFR signalling. Natural killer cell mediated antibody-dependent cellular cytotoxicity (ADCC) and tumour necrosis factor α (TNF-α) release was analysed for Cetuximab. Fourteen of 48 UMs and three of 14 cell lines (over-)express EGFR, at least in part due to trisomy of the EGFR locus on chromosome 7p12. EGFR and the downstream mediator, AKT, are phosphorylated upon stimulation with EGF in EGFR expressing cell lines. EGFR over-expressing tumours but not EGFR negative tumours show an activated EGF-signature. Gefitinib inhibits EGFR and AKT phosphorylation and Cetuximab induces EGFR phosphorylation but inhibits signalling to AKT induced with EGF. Cetuximab triggers natural killer (NK) cells to lyse EGFR+ cell lines and to release TNF-α. EGFR appears suited as a novel molecular drug target for therapy of uveal melanoma.

A pilot study of sunitinib malate in patients with metastatic uveal melanoma

The prognosis of patients with metastatic uveal melanoma is poor and there are limited therapeutic options. C-kit is expressed in the majority of patients with metastatic uveal melanoma. In this pilot trial, we examined the toxicity and efficacy of sunitinib malate, a multitarget tyrosine kinase inhibitor, in patients with metastatic uveal melanoma. Twenty patients with metastatic uveal melanoma expressing c-kit, 17 of whom failed previous treatments, were included in this study. Patients received sunitinib malate 37.5 mg daily continuously in 4-week cycles. The evaluation of response was carried out every 8 weeks. The overall survival (OS) and progression-free survival (PFS) were evaluated using Kaplan-Meier survival curves and differences in survivals were tested using the log-rank test. There was one partial response and 12 stable disease (SD) after sunitinib treatment. The median OS and PFS were 8.2 and 4.2 months, respectively. Three patients had SD for more than 12 months with sunitinib after failing previous treatments. The most common adverse events were fatigue (90%), diarrhea (60%), hemorrhage (55%), anorexia (45%), hand-foot syndrome (25%), hypothyroidism (25%), and rash (25%). Eleven patients required a dose reduction to 25 mg daily secondary to grade 3 adverse events. The degree of c-kit expression in melanoma cells was not associated with longer PFS or OS. Patients who developed systemic metastases after more than 5 years of their initial diagnosis had better PFS (median PFS: 5.8 vs. 2.6 months, P=0.005). Sunitinib was safely administered and showed potential clinical benefit in patients with metastatic uveal melanoma. The lack of a correlation between c-kit expression and clinical outcomes requires further investigation on the mechanism of sunitinib in metastatic uveal melanoma.

Uveal melanoma dormancy: an acceptable clinical endpoint?

Uveal melanoma is a rare but life-threatening malignancy. Over the past decades, the morbidity of uveal melanoma has been markedly reduced as a result of advances in the diagnostic ability to detect smaller tumors at an earlier stage. This has allowed for the use of more conservative treatments, avoiding enucleation. Mortality, however, has remained unchanged. This indicates that life expectancy is independent of local tumor control. Metastatic disease, the leading cause of death, is usually diagnosed many years later, despite successful treatment of the primary tumor, and at a late stage, when no effective therapy is available. These observations suggest that the disease was already disseminated at the time of tumor diagnosis. The detection of circulating malignant cells in the bloodstream of patients at different time points in the course of the disease supports this observation. Tumor dormancy has been considered as the leading theory for this intriguing delayed appearance of metastasis. Recent knowledge gained about the biological behavior of uveal melanoma as well as novel potential therapeutic targets are presented in this review.

Expression of stem cell factor in gastrointestinal stromal tumors: Implications for proliferation and imatinib resistance

KIT autophosphorylation caused by mutation of KIT is considered to be a critical mechanism for the oncogenesis of gastrointestinal stromal tumors (GISTs). However, little is known regarding whether stem cell factor (SCF), the KIT ligand, is able to induce the proliferation of GIST cells by activating the wild-type KIT receptor in GISTs. Imatinib, a tyrosine kinase inhibitor, has been demonstrated to be effective as treatment for the majority of GISTs. However, primary resistance to imatinib in GISTs with wild-type KIT and acquired resistance in GISTs with mutant KIT are becoming increasingly significant problems. The aims of this study were to detect the expression and function of SCF in 68 GIST samples, and to explore the relationship between SCF activity and imatinib resistance using immunohistochemical staining and western blot analysis. Results showed abundant expression of SCF in GISTs and demonstrated that SCF is capable of enhancing GIST cell proliferation. Similar to its ineffectiveness in wild-type GISTs, imatinib also failed to inhibit SCF-induced KIT activation in GISTs with mutant KIT. We also found increased SCF expression in GIST cells treated with imatinib. Overall, our results indicated that SCF-induced KIT activation is a novel essential pathway for the proliferation of GISTs. Imatinib was not able to inhibit the activity of SCF, while it promoted the expression of SCF, which may have contributed to acquired imatinib resistance.

KIT gene mutations and patterns of protein expression in mucosal and acral melanoma

BACKGROUND

Recently characterized KIT (CD117) gene mutations have revealed new pathways involved in melanoma pathogenesis. In particular, certain subtypes harbor mutations similar to those observed in gastrointestinal stromal tumors, which are sensitive to treatment with tyrosine kinase inhibitors.

OBJECTIVE

The purpose of this study was to characterize KIT gene mutations and patterns of protein expression in mucosal and acral melanoma.

METHODS

Formalin-fixed, paraffin-embedded tissues were retrieved from our archives. Histologic assessment included routine hematoxylin-eosin stains and immunohistochemical staining for KIT. Genomic DNA was used for polymerase chain reaction-based amplification of exons 11 and 13.

RESULTS

We identified 59 acral and mucosal melanoma cases, of which 78% showed variable levels of KIT expression. Sequencing of exons 11 and 13 was completed on all cases, and 4 (6.8%) mutant cases were isolated.

CONCLUSION

We successfully optimized conditions for the detection of KIT mutations and showed that 8.6% of mucosal and 4.2% of acral melanoma cases at our institution harbor KIT mutations; all mutant cases showed strong, diffuse KIT protein expression. Our case series represents the first Canadian study to characterize KIT gene mutations and patterns of protein expression in acral and mucosal melanoma.

Mutation analysis of BRAF and KIT in circulating melanoma cells at the single cell level

Background:

The availability of molecular-targeted therapies for the treatment of melanoma has emphasised the need to identify mutations in target genes such as BRAF and KIT. Circulating tumour cells (CTC) are present in the peripheral blood of a significant proportion of cancer patients.

Methods:

High molecular weight melanoma-associated antigen (HMW-MAA) was used to isolate melanoma cells from peripheral blood as it is selectively expressed at high levels on melanomas. The HMW-MAA-positive cells were isolated using immunomagnetic beads. After removing CD45⁺ cells, CTC were identified by staining with MART-1- and gp100-specific antibodies (HMW-MAA⁺, CD45⁻, MART-1/gp100⁺). Single, isolated CTC were then subjected to BRAF and KIT mutational analysis.

Results:

CTC (HMW-MAA⁺, CD45⁻, MART-1/gp100⁺) were isolated from the blood of 11 patients and BRAF and KIT were sequenced in nine and four patients, respectively. The BRAF sequences identified in the CTC were inconsistent with those identified in autologous melanoma tumours in three patients and the KIT sequences were inconsistent in three patients. In addition, polyclonal BRAF mutations were identified in one patient and concomitant mutations in BRAF and KIT were identified in another patient.

Conclusion:

Melanoma cells show clonal heterogeneity. Therefore, CTC genotyping may be crucial for successful molecular-targeted therapy.

Targeting the RAS pathway in melanoma

Metastatic melanoma is a highly lethal type of skin cancer and is often refractory to all traditional chemotherapeutic agents. Key insights into the genetic makeup of melanoma tumors have led to the development of promising targeted agents. An activated RAS pathway, anchored by oncogenic BRAF, appears to be the central motor driving melanoma proliferation. Although recent clinical trials have brought enormous hope to patients with melanoma, adverse effects and novel escape mechanisms of these inhibitors have already emerged. Definition of the limits of the first successful targeted therapies will provide the basis for further advances in management of disseminated melanoma. In this review, the current state of targeted therapy for melanoma is discussed, including the potent BRAF(V600E) inhibitor vemurafenib.

Whole genome and exome sequencing of melanoma: a step toward personalized targeted therapy

Melanoma has historically been refractive to traditional therapeutic approaches. As such, the development of novel drug strategies has been needed to improve rates of overall survival in patients with melanoma, particularly those with late stage or disseminated disease. Recent success with molecularly based targeted drugs, such as Vemurafenib in BRAF-mutant melanomas, has now made "personalized medicine" a reality within some oncology clinics. In this sense, tailored drugs can be administered to patients according to their tumor "mutation profiles." The success of these drug strategies, in part, can be attributed to the identification of the genetic mechanisms responsible for the development and progression of metastatic melanoma. Recently, the advances in sequencing technology have allowed for comprehensive mutation analysis of tumors and have led to the identification of a number of genes involved in the etiology of metastatic melanoma. As the methodology and costs associated with next-generation sequencing continue to improve, this technology will be rapidly adopted into routine clinical oncology practices and will significantly impact on personalized therapy. This review summarizes current and emerging molecular targets in metastatic melanoma, discusses the potential application of next-generation sequencing within the paradigm of personalized medicine, and describes the current limitations for the adoption of this technology within the clinic.

Therapeutic opportunities in noncutaneous melanoma

Recent evidence suggests that the biology of noncutaneous melanoma differs significantly from cutaneous melanoma and may provide therapeutic opportunity. The most frequent sites of origin of noncutaneous melanoma are the eye and mucosal surfaces. Although noncutaneous melanomas are an uncommon group of cancers (representing less than 10% of all melanomas) a greater understanding of their genetic and molecular abnormalites is being translated into novel treatment strategies. These developments are important because there is currently no effective systemic therapy for noncutaneous melanoma. Significant attention has been focused on the role of c-kit (KIT, CD117), a transmembrane receptor with tyrosine kinase activity. In vitro and ex vivo evidence suggests that c-kit is frequently expressed/over expressed/mutated in noncutaneous melanoma. Anti-tumour effects with c-kit inhibitors are seen in pre-clinical models. A variety of multitargeted kinase inhibitors which have activity against c-kit are currently in early phase clinical trials in metastatic ocular, mucosal and acral melanoma. The few case reports of significant clinical activity with targeted therapies provides hope that greater understanding of the biology of noncutaneous melanoma can be translated into effective treatment.

Towards new therapeutic approaches for malignant melanoma

Recent progress in understanding the molecular mechanisms of the initiation and progression of melanoma has created new opportunities for developing novel therapeutic modalities to manage this potentially lethal disease. Although at first glance, melanoma carcinogenesis appears to be a chaotic system, it is indeed, arguably, a deterministic multistep process involving sequential alterations of proto-oncogenes, tumour suppressors and miRNA genes. The scope of this article is to discuss the most recent and significant advances in melanoma molecular therapeutics. It is apparent that using single agents targeting solely individual melanoma pathways might be insufficient for long-term survival. However, the outstanding results on melanoma survival observed with novel selective inhibitors of B-RAF, such as PLX4032 give hope that melanoma can be cured. The fact that melanoma develops acquired resistance to PLX4032 emphasises the importance of simultaneously targeting several pathways. Because the most striking feature of melanoma is its unsurpassed ability to metastasise, it is important to implement newer systems for drug delivery adapted from research on stem cells and nanotechnology.

c-Abl and Arg are activated in human primary melanomas, promote melanoma cell invasion via distinct pathways, and drive metastatic progression

Despite 35 years of clinical trials, there is little improvement in 1-year survival rates for patients with metastatic melanoma, and the disease is essentially untreatable if not cured surgically. The paucity of chemotherapeutic agents that are effective for treating metastatic melanoma indicates a dire need to develop new therapies. Here, we found a previously unrecognized role for c-Abl and Arg in melanoma progression. We demonstrate that the kinase activities of c-Abl and Arg are elevated in primary melanomas (60%), in a subset of benign nevi (33%) and in some human melanoma cell lines. Using siRNA and pharmacological approaches, we show that c-Abl/Arg activation is functionally relevant because it is requiredfor melanoma cell proliferation, survival and invasion. Significantly, we identify the mechanism by which activated c-Abl promotes melanoma invasion by showing that it transcriptionally upregulates matrix metalloproteinase-1 (MMP-1), and using rescue approaches we demonstrate that c-Abl promotes invasion through a STAT3 → MMP-1 pathway. Additionally, we show that c-Abl and Arg are not merely redundant, as active Arg drives invasion in a STAT3-independent manner, and upregulates MMP-3 and MT1-MMP, in addition to MMP-1. Most importantly, c-Abl and Arg not only promote in vitro processes important for melanoma progression, but also promote metastasis in vivo, as inhibition of c-Abl/Arg kinase activity with the c-Abl/Arg inhibitor, nilotinib, dramatically inhibits metastasis in a mouse model. Taken together, these data identify c-Abl and Arg as critical, novel, drug targets in metastatic melanoma, and indicate that nilotinib may be useful in preventing metastasis in patients with melanomas harboring active c-Abl and Arg.

KIT mutations in ocular melanoma: frequency and anatomic distribution

KIT mutations are known to occur in ~15% of chronic sun damaged cutaneous, mucosal, and acral melanomas. Melanomas with demonstrated activating mutations in KIT or platelet-derived growth factor receptor A (PDGFRA) may benefit from treatment with tyrosine kinase inhibitors. Currently, the limited data regarding KIT mutational status in ocular melanoma suggest that activating mutations are extremely rare. PDGFRA mutational status in ocular melanoma has not been determined. Seventy-five ocular melanomas (53 choroidal, 6 iris, 11 ciliary body, and 5 conjuctival) were selected from the files of the Department of Ophthalmology. High-resolution melting curve analysis and sequencing were performed to detect mutations in KIT exons 9, 11, 13, and 17 and PDGFRA exons 12 and 18. Results of mutational analysis were correlated with anatomical site and KIT (CD117) immunohistochemistry. Eight of 75 (11%) ocular melanomas contained mutations in either the KIT or PDGFRA gene. Five of 53 (9%) choroidal melanomas were associated with mutations (KIT exon 11=3; KIT exon 17=1; PDGFRA intron 18=1). Two of six (33%) iris melanomas and a single (9%) ciliary body melanoma harbored KIT exon 11 mutations. No mutations were identified in conjunctival melanomas. The distribution of KIT and PDGFRA mutations by ocular melanoma anatomical site did not reach statistical significance (P=0.393) CD117 positivity was not predictive of KIT mutational status as only 6 of 58 (10%) CD177-positive tumors harbored KIT mutations. In addition, a KIT exon 17 mutation was identified in one CD117-negative tumor. KIT and PDGFRA mutations do occur in ocular melanomas at a frequency (11%) that is similar to acral and mucosal melanomas. Limited correlation of CD117 positivity with mutational status suggests that all ocular melanomas should undergo mutational analysis to determine if imatinib therapy is appropriate.