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.     

The biology and management of uveal melanoma

Uveal melanoma is the most common primary intraocular malignancy in adults. Overall mortality rate remains high because of the frequent development of metastatic disease, especially hepatic metastasis. While traditional systemic chemotherapies provide only marginal benefit to patients, local treatments for hepatic metastases, such as immunoembolization, have improved patient prognoses. Progress has also been made in identifying potential targets in the pathways involved in apoptosis, proliferation, invasion, metastasis, and angiogenesis of uveal melanoma. Among these pathways, the c-Kit, c-Met, and IGF-1R signal pathways and the PTEN-related P13K-Akt pathway are the most important targets. Clinical trials using blockades of these pathways in conjunction with strategies to facilitate apoptosis is a direction for future clinical trials. Application of these approaches in the adjuvant setting after primary therapy for high-risk uveal melanoma patients is also a future consideration to improve the clinical outcome of this disease.     

Metastatic melanoma: chemotherapy

The incidence of cutaneous melanoma has been rapidly increasing, with an estimate of 47,700 new cases diagnosed in 2000 in the United States. In the early phase of its natural history, melanoma is cured in most cases by surgery, but once the metastatic phase develops, it is almost always fatal. The treatment of metastatic melanoma remains unsatisfactory. Systemic therapy has not been successful up to now, with very low response rates to single-agent chemotherapy. Polychemotherapy has increased the response rate (RR), without a significant improvement in overall survival. Immunotherapy alone is able to induce only a few durable complete responses (CRs). New chemotherapeutic and biologic agents are now available and promising combined approaches targeting the tumor by several different mechanisms are desirable and will probably represent the future modality of treatment.     

Proteomics in uveal melanoma

A new tool in the search for tumour markers is proteomic technology. Proteomics (or protein profiling) is the study of the proteome, the protein complement of the genome. The advantage of this technique in comparison with genomics is that the actual protein production can be measured. Gene microarrays determine levels of mRNA but do not necessarily predict the level of the corresponding proteins in a cell. In this study, we evaluated the use of proteomics in the aqueous humour of uveal melanoma patients compared with control patients using the surface-enhanced laser desorption ionization time-of-flight technique. The protein mass spectra of aqueous humours from 24 uveal melanoma eyes were compared with 24 control eyes using a strong anion exchange surface protein chip array. On the basis of two proteins (4543.43 and 6853.30 kDa), the aqueous humour of melanoma eyes and control eyes could be distinguished in 89% of cases. Therefore, proteomic evaluation might be helpful in finding diagnostic markers for uveal melanoma patients.     

Metastatic melanoma

Current treatment options in metastatic melanoma are of limited efficacy. Achievement of durable responses with biological agents, and the possibility to complement the higher response rate of chemotherapy and combined chemotherapy by prolonged duration of responses, led to development of biochemotherapy. Although a clear improvement in response rate (40–60% OR) resulted in some studies of the combined modality, several phase III studies had mixed results on the duration of survival. Various timeframes between the administration of chemotherapy and biologics have been tested, ranging between concurrent biochemotherapy, 1 d (immediately sequential), and up to 3 wk (long sequence or alternating). An analysis of the trend of responses and survival versus the duration of the chemobiotherapy sequence showed that, as the timeframe between chemo and bio components increases, the overall survival, survival of complete responders, and survival of partial responders appear to increase, but the effect is only present for the chemo-bio, and not for the bio-chemo sequence. Because there is no current explanation for this observation, it appears possible that the interaction between components of biochemotherapy results in a double effect: an increase in the immediate response reflected in the OR, CR, PR on one side, and an increase in survival on the other side. An analysis of mechanisms involved in the response leads us hypothesize that macrophage activation, as measured by the neopterin levels, may correlate with the survival of patients undergoing biochemotherapy, while the generation of nitric oxide, acting synergistically with chemotherapy in producing tumor cell killing, may be reflected in the overall response rate seen with the biochemotherapy combinations.     

Metastatic melanoma

Opinion statement The overall survival for patients with metastatic melanoma ranges from 4.7 to 11 months, with a median survival of 8.5 months. Standard treatment for patients with metastatic melanoma has not been defined. The range of treatment options includes close observation, surgical resection of isolated metastases, therapy with dacarbazine, combination chemotherapy, and participation in clinical trials. Numerous chemotherapeutic agents have shown activity in the treatment of malignant melanoma. Dacarbazine (DTIC-Dome; Bayer Corporation, West Haven, CT) has a response rate of 15% to 20% and remains the reference agent for the treatment of metastatic disease. Additional agents with single-agent activity include cisplatin, (Platinol-AQ; Bristol-Myers Oncology, Princeton, NJ); carmustine (BiCNU; Bristol-Myers Oncology, Princeton, NJ); paclitaxel (Taxol; Bristol-Myers Squibb, Princeton, NJ); and docetaxel (Taxotere; Rhone-Poulenc Rorer Pharmaceuticals, Collegeville, PA). Temozolomide (Temodar; Schering-Plough, Kenilworth, NJ), which is essentially an oral form of dacarbazine but with greater central nervous system penetrance, is associated with a response rate of 20%. Combination chemotherapy with or without tamoxifen has been extensively evaluated in patients with metastatic melanoma. Although the initial results with the Dartmouth regimen (dacarbazine, cisplatin, carmustine, and tamoxifen) were associated with overall response rates of 50% to 55% in single-institution studies, results from larger multicenter studies reveal responses rates ranging from 10% to 20%. Based on the results of several clinical trials, there is no evidence that the addition of tamoxifen improves the response rate. Another combination regimen is cisplatin, vinblastine, and dacarbazine (CVD), which is associated with a 20% to 25% response rate. There has been widespread interest in developing immunotherapies against metastatic melanoma. Interferon (IFN)-alfa and interleukin (IL)-2 as single agents have produced response rates in the 15% to 20% range. Biochemotherapy, which is a combination of immunotherapy and cytotoxic chemotherapy, has been studied in patients with metastatic melanoma. Multiple phase II studies have demonstrated high response rates but unclear impact on overall survival. Therapy is associated with significant toxicity. Ongoing randomized clinical trials will clarify the role of biochemotherapy in patients with metastatic melanoma. Ongoing new approaches to treatment include the therapeutic use of vaccines alone or in combination with cytokines.     

Animal models of uveal melanoma

Many attempts have been made to develop a suitable animal model to study more effectively the aetiology, pathogenesis, diagnosis and therapy of intraocular (uveal) melanoma. Uveal melanoma may spontaneously occur in some animals, including dogs, cats, horses, rats, mice, birds and fish. The histological features, metastatic behaviour and unpredictable nature of occurrence of these uncommon spontaneous tumours detract from their suitability as a model. Several methods have been developed to induce intraocular melanoma chemically or by radiation in laboratory animals. Some of these induced tumours resemble human uveal melanoma, although the majority originate from the retinal pigment epithelium. Uveal proliferations have been biologically induced by feline leukaemia/sarcoma virus and simian virus 40, although the presence of virus in tumour cells and extraocular tumours resulting from shed virus detract from the utility of this model. Inoculation of tissue culture hamster, murine or human melanoma cells into animal eyes has the advantage that the inoculation site and size of inoculum can be controlled. Disadvantages include the immune suppression necessary for tumour growth in some models as well as the fact that many of the melanoma cell lines are of cutaneous origin. Transgenic murine models have been developed using the promoter region of the tyrosinase gene to target expression of oncogenes in melanin-producing cells. Spontaneous intraocular pigmented tumours and distant metastases may occur, although many, if not all, of the intraocular tumours arise in the retinal pigment epithelium.     

Immunogenetic heterogeneity of uveal melanoma

Investigations have been performed to identify genetic markers in uveal melanoma (UM) patients. The immunogenetic heterogeneity of the histologically different forms of UM until now has been little analyzed. We subdivided our UM patients, all typed for class I and II HLA antigens and for Bf polymorphism, into two groups: 1) those with a high degree of malignancy (with nonspindle cells) and 2) those with a low degree of malignancy (with spindle cells). The deviated frequencies of class I HLA antigens (A32, B27) seem to be involved in the predisposition to spindle cell melanoma, while HLA class II (DR3, DR7) and class III (Bf F) strongly mark the worst form of UM. Different Gm allotype distributions between the two histological types of UM were also found.     

Prognostic factors in uveal melanoma

Uveal melanoma is the most common primary intraocular malignant tumour, with an annual incidence of approximately six cases per million per year. Approximately 40% of patients with posterior uveal melanoma develop metastatic melanoma to the liver within 10 years after initial diagnosis. Despite high accuracy of diagnosis and availability of various methods of treatment; the mortality due to uveal melanoma has remained unchanged. The prognosis in uveal melanoma depends on clinical, histopathological and cytological factors. Clinical factors that relate to prognosis include location, size, and configuration of the tumour. Uveal melanoma can arise in the iris, the ciliary body or the choroid. Iris melanomas have the best prognosis and ciliary body melanomas have the worst prognosis. Based on retrospective studies, the mortality rates for uveal melanoma for comparable sized tumours treated by enucleation or other globe conserving methods such as radiotherapy appear to be similar. Histopathological factors such as cell type, mitotic activity, microcirculation architecture, tumour-infiltrating lymphocytes and the presence of extrascleral extension are also significant predictors of survival. More recently, cytological factors such as cell proliferation, cytogenic, and molecular genetic prognostic markers have been identified with the hope of detecting high risk cases for adjuvant systemic immune therapy or chemotherapy. At present, the role of these therapeutic methods is not clearly established.     

Targeted therapy for uveal melanoma

Uveal melanoma is the most common primary intra-ocular malignancy in adults. Overall mortality rate remains high because of the development of metastatic disease, which is highly resistant to systemic therapy. Improved understanding of the molecular pathogenesis of cancers has led to a new generation of therapeutic agents that interfere with a specific pathway critical in tumor development or progression. Although no specific genes have been linked to the pathogenesis of uveal melanoma, which differs from that of cutaneous melanoma, progress has been made in identifying potential targets involved in uveal melanoma apoptosis, proliferation, invasion, metastasis, and angiogenesis. This review focuses on the prospects for improving the systemic therapy of uveal melanoma using molecularly targeted agents that are currently in clinical use as well as agents being tested in clinical trials. Preclinical studies suggest potential benefit of inhibitors of Bcl-2, ubiquitin-proteasome, histone deactylase, mitogen-activated protein kinase and phosphatidylinositol-3-kinase-AKT pathways, and receptor tyrosine kinases. Modifiers of adhesion molecules, matrix metalloproteinase, and angiogenic factors also have demonstrated potential benefit. Clinical trials of some of these approaches have been initiated in patients with metastatic uveal melanoma as well as in the adjuvant setting after primary therapy.     

Depsipeptide inhibits migration of primary and metastatic uveal melanoma cell lines in vitro: a potential strategy for uveal melanoma

Uveal melanoma (UM) is a highly malignant primary intraocular tumour in adults that has a high mortality rate due to haematogenous dissemination. The migration of UM cells through the basement membrane requires the presence of proteolytic enzymes, such as matrix metalloproteinases (MMPs). The expression of MMP-2, MMP-9 and membrane type-1/MMP (MT-1/MMP) in UM cells is a known risk factor for metastatic disease. We tested the effect of depsipeptide (DP) on UM cell migration and the level and activity of MMP-2, MMP-9, MT-1/MMP and tissue inhibitors of matrix metalloproteinases 1 and 2 (TIMP-1 and TIMP-2). Three primary and two metastatic (liver metastasis) UM cell lines were treated with DP (0, 1, 5 and 10 nmol/l) for 24 h. Migration of UM cells was studied in modified Boyden migration chambers for 24 h and only viable cells on both sides of the membrane were counted. Enzyme-linked immunosorbent assays (ELISAs) were used to quantify the level of MMP-2, MMP-9, MT-1/MMP, TIMP-1 and TIMP-2 after the cells had been exposed to DP (0, 1, 5 and 10 nmol/l) for 24 h. In addition, the activities of MMP-2, MMP-9 and MT-1/MMP were determined after DP treatment. A dose-dependent decrease in the migration of viable UM cells was observed for primary and metastatic cell lines (30-50% inhibition). We detected a dose-dependent: (1) decrease in the protein level of MMP-2, MMP-9 and MT-1/MMP; (2) decrease in the activity of MMP-2, MMP-9 and MT-1/MMP; and (3) increase in the protein level of TIMP-1 and TIMP-2. It can be concluded that DP is a potent inhibitor of primary and metastatic UM cell migration in vitro. Our data suggest that this inhibition is mediated by the downregulation of MMPs and the upregulation of TIMPs. DP may be a valuable adjunctive treatment modality for primary and metastatic UM in humans.     

Metastatic melanoma: an unusual presentation

In this report we describe a case of a malignant cutaneous melanoma metastasizing to the pleural surface and peritoneal cavity 5 years after surgical resection of the primary lesion. Malignant cutaneous melanoma is a very aggressive cancer able to metastasize anywhere in the body. Pleural secondary lesions represent a rare event described only in a small number of patients and the association with peritoneal localizations may suggest an uncommon pattern of spread that we discuss.     

Local environmental influences on uveal melanoma: vitreous humor promotes uveal melanoma invasion, whereas the aqueous can be inhibitory

BACKGROUND: Uveal melanomas of the choroid and ciliary body are aggressive tumors causing the death of approximately 50% of patients. In contrast, iris melanomas only infrequently metastasize; why these differences exist is not known. The local environment can regulate cancer growth and development, and it is probable the aqueous and vitreous humors have an important role in regulating uveal melanoma behavior. METHODS: To explore this possibility cultures of uveal melanoma were exposed to aqueous and vitreous and the effects investigated using invasion and proliferation assays. ChemiArrays (Chemicon International, Temecula, Calif) were performed to determine which regulatory factors might influence the process. RESULTS: The vitreous universally promoted uveal melanoma invasion, whereas the aqueous mainly had no effect or was inhibitory. Tumor location, and the baseline invasion of the melanoma, affected the ability of aqueous and vitreous from different patients to regulate invasive behavior. Proliferation was not significantly altered as a result of exposure to the aqueous or vitreous. The ability of the humors to regulate uveal melanomas may involve TIMP-2, TIMP-3, and TGF-beta2, as high expression was found by ChemiArray analysis and there were differences in the levels of the regulators in the aqueous compared with the vitreous. CONCLUSIONS: The findings suggest that in situ uveal melanoma development reflects an interaction between the tumor and the environment of the eye. Exposure to the aqueous would therefore contribute to the benign nature of iris melanomas, whereas potential interaction with the vitreous appears to promote the aggressive behavior of posterior uveal melanomas.     

New therapeutic agents in uveal melanoma

Uveal melanoma is the most common primary intraocular malignant tumour in adults. Five, ten and fifteen years after primary tumour treatment, up to 25%, 34% and 50% of patients may develop metastases, respectively. There are only a few systemic therapies that have been approved for uveal melanoma, all with doubtful efficacy. As the molecular knowledge over cancer has improved, new therapies are being developed. Several drugs, such as bortezomib, celecoxib, dacarbazine, anti-angiogenic agents (such as bevacizumab, sorafenib and sunitinib), temsirolimus, mitogen-activated protein kinase kinase (MEK) inhibitors, ipilimumab and AEB071 are candidate drugs, and studies are underway to determine the therapeutic effects of these drugs in uveal melanoma.     

Tumor cell markers in uveal melanoma

Monoclonal antibodies to the melanoma-associated antigens HMB-45 and NKI/C3, and for S-100 protein were applied to archival tissue of 43 intraocular melanomas. Tn addition, the expression of the oncoproteins ras-p21 (ras 10) and mutated Ha-ras (E 184) as well as neu/erb-B2 (p185) were immunohistochemically evaluated. Incubation with antibodies to HMB-45 and NKI/C3 revealed consistently moderate to strong staining in all cases. Comparable ras-p21 immunostaining with normal epithelium observed in infiltrating components with a pronounced heterogeneous pattern, was particulary evident in epitheloid tumor cells. In melanomas of the spindle cell type B there was a tendency for patients with neu/erb-B2 positivity to have a worse prognosis. Using the chi-squared test for trend a significant correlation was found between S-100 reactivity, neu/erb-B2 amplification and the clinical outcome.     

Lymphocytic infiltration in uveal malignant melanoma

A study relating the intralesional infiltration of lymphocytes and plasma cells to patient survival was performed on cases of uveal malignant melanoma accessed at the Armed Forces Institute of Pathology, Washington, DC (AFIP) between 1954 and 1971. The authors examined 1193 cases using light microscopy. Of the 1078 cases with technically acceptable histologic sections, 134 tumors contained 100 or more lymphocytes per 20 high-power (X400) microscopic fields (20 HPF). The prevalence was 12.4%. This was designated the "high lymphocytic" group. An equivalent number of cases with fewer lymphocytes comprised the "low lymphocytic" group. The survival rate at 15 years was 36.7% for patients in the high lymphocytic group and 69.6% for patients in the low lymphocytic group. Using the Cox model, the authors found that an increased number of lymphocytes per 20 HPF was significantly associated with decreased survival (chi-square = 21.2, P = less than 0.0001). A significant association was observed even when we controlled for other risk factors (chi-square = 6.98, P = 0.008).