Secretion of hepatocyte growth factor and vascular endothelial growth factor during uveal melanoma-monocyte in vitro interactions

Host-tumour interactions in uveal melanoma, and their involvement in the biological events leading to metastasis and eventually mortality, are not well understood. It is known that uveal melanoma disseminates predominantly via a haematogenous route with metastasis developing primarily in the liver. Therefore, cytokines involved in angiogenesis, such as vascular endothelial growth factor (VEGF), and those expressed in large quantities within the liver, such as hepatocyte growth factor (HGF), are of particular interest in uveal melanoma research. This study investigated the levels of HGF and VEGF in monocyte and uveal melanoma-conditioned medium. Five human uveal melanoma cell lines and one monocyte cell line were seeded in six-well plates. After 18 h, melanoma-conditioned medium (MCM) was placed on the monocyte cell line and monocyte-conditioned medium (MoCM) was placed on each uveal melanoma cell line. Tumour cells and monocytes incubated in fresh, as opposed to conditioned, medium after 18 h were used as controls. VEGF and HGF levels were determined by immunoassay prior to media transfer and 6, 12, 24 and 36 h thereafter. Both cytokines showed an upregulation of expression from all cells after incubation in conditioned medium. 28SC incubated in MCM expressed higher levels of the given cytokines than did uveal melanoma cells incubated in MoCM. In addition, each cell line exhibited a distinct pattern of expression, with individual cell lines exhibiting different peak levels of cytokine production at different time points. These results offer insight into the upregulation of VEGF and HGF, which may play a role in tumour-host cell interactions.     

Tamoxifen, 17beta-oestradiol and the calmodulin antagonist J8 inhibit human melanoma cell invasion through fibronectin.

Invasion through stromal extracellular matrix (ECM) is part of the complex, multistep process of tumour cell invasion and metastasis. Our group has previously demonstrated that calcium and calmodulin are important in another step in the metastatic cascade - that of attachment of cells to ECM. Interestingly, the non-steroidal anti-oestrogen tamoxifen (which also has calmodulin antagonist activity), used in the treatment of breast cancer and now in metastatic cutaneous melanoma, can inhibit the attachment of normal and neoplastic cells to ECM. In this study, we investigated whether such drugs, known to inhibit cell attachment, could also subsequently reduce their invasion through a layer of human fibronectin. We examined the ability of the specific calmodulin antagonist J8, tamoxifen and its two major metabolites, N-desmethyltamoxifen (N-des) and 4-hydroxytamoxifen (4-OH), as well as the pure anti-oestrogen ICI 182,780 and 17beta-oestradiol to inhibit invasion of the human cutaneous melanoma cell line, A375-SM, uveal melanoma cells and uveal melanocytes. A375-SM cells and uveal melanoma cells showed a high level of invasion (15.2% and 33.7% respectively) compared with melanocytes (around 5%) under the experimental conditions used. Submicromolar concentrations of N-des, tamoxifen, J8 and 17beta-oestradiol significantly reduced the invasiveness of the A375-SM cell line. The uveal melanoma cells also showed similar inhibition, although at higher concentrations of these agents. 4-OH and ICI 182, 780 had little or no effect on invasion of A375-SM cells (these were not tested on uveal melanoma cells). All cells used in this study were found to be negative for type I nuclear oestrogen receptors, reinforcing the possibility that tamoxifen and 17beta-oestradiol can act via mechanisms unrelated to binding to classical oestrogen receptors to inhibit tumour cell invasion.     

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.     

Effect of an anti-CD54 (ICAM-1) monoclonal antibody (UV3) on the growth of human uveal melanoma cells transplanted heterotopically and orthotopically in SCID mice

We have shown that administration of a novel anti-CD54 monoclonal antibody (UV3) results in long-term survival of SCID mice bearing human myeloma xenografts. Previous studies have demonstrated a link between the expression of CD54 and the progression of uveal melanoma. Our study assessed the expression of CD54 on 7 human uveal melanoma cell lines and 3 cell lines established from uveal melanoma metastases. In vivo studies examined the efficacy of systemic and local administration of UV3 antibody on the progression of uveal melanoma cells transplanted either heterotopically or orthotopically into SCID mice. Five of the 7 primary uveal melanoma cell lines and all 3 of the metastases cell lines expressed CD54. Intraperitoneal injection of either IgG or F(ab')2 fragments of UV3 significantly inhibited the growth of subcutaneous and intraocular melanomas. Subconjunctival injection of either IgG or F(ab')2 fragments of UV3 produced a significant reduction in the growth of intraocular melanomas, even if the antibody was administered after the appearance of intraocular tumors. The results indicate that both primary and metastatic human uveal melanoma cells express CD54. The marked inhibition of intraocular and subcutaneous uveal melanoma progression suggests that UV3 antibody is a promising therapeutic agent for further evaluation in patients with uveal melanoma. This is especially noteworthy, as no existing therapeutic modality prevents metastasis of uveal melanoma or prolongs the survival of patients with uveal melanoma.     

High PTP4A3 phosphatase expression correlates with metastatic risk in uveal melanoma patients

A high percentage of uveal melanoma patients develop metastatic tumors predominantly in the liver. We studied the molecular profiles derived from gene expression microarrays and comparative genomic hybridization microarrays, to identify genes associated with metastasis in this aggressive cancer. We compared 28 uveal melanomas from patients who developed liver metastases within three years of enucleation with 35 tumors from patients without metastases or who developed metastases more than 3 years after enucleation. Protein tyrosine phosphatase type IV A member 3 (PTP4A3/PRL3), was identified as a strong predictor of metastasis occurrence. We demonstrated that the differential expression of this gene, which maps to 8q24.3, was not merely a consequence of 8q chromosome overrepresentation. PTP4A3 overexpression in uveal melanoma cell lines significantly increased cell migration and invasiveness in vivo, suggesting a direct role for this protein in metastasis. Our findings suggest that PTP4A3 or its cellular substrates could constitute attractive therapeutic targets to treat metastatic uveal melanomas.     

Expression of integrins, degradative enzymes and their inhibitors in uveal melanoma: differences between in vitro and in vivo expression

Posterior uveal melanoma is the most common intraocular malignancy in adults. Metastasis occurs in approximately 40% of all cases and spread is primarily to the liver. Once secondary hepatic disease has developed the prognosis is poor. Metastasis involves a series of adhesion and de-adhesion events, coupled with regulated tissue degradation to facilitate tumour cell invasion and spread to both local and distant sites. These processes are assisted by the expression of integrins and degradative enzymes by both tumour and host cells. Using a series of 10 uveal melanomas, we investigated the expression of a panel of integrins, degradative enzymes and their inhibitors that have been shown to be associated with metastasis. In addition, we undertook to establish if there might be differential expression in response to growth under artificial conditions. All the tumours expressed matrix metalloproteinases (MMP)-2 and-9, tissue inhibitor of metalloproteases (TIMP)-2, urokinase plasminogen activator (u-PA), plasminogen activator inhibitor (PAI)-1 and PAI-2. Differences in the expression of the integrins alpha1beta1, alpha2beta1 and alpha6beta1 were observed; in particular, these differences appeared to relate to expression as a consequence of growth in culture. In summary, uveal melanoma cells express both degradative enzymes and their respective inhibitors, which are important in metastasis. It would appear that differential expression of integrins is present, probably as a response to in vitro stimulation.     

Focal adhesion kinase promotes the aggressive melanoma phenotype

Malignant melanoma continues to remain a significant health threat, with death often occurring as a result of metastasis. The metastatic phenotype typically is characterized by augmented tumor cell invasion and migration in addition to tumor cell plasticity as shown by vasculogenic mimicry. Therefore, understanding the molecular mechanisms that promote an aggressive phenotype is essential to predicting the likelihood of metastasis at a stage when intervention may be possible. This study focuses on the role of focal adhesion kinase (FAK), a cytoplasmic tyrosine kinase important for many cellular processes, including cell survival, invasion, and migration. We found FAK to be phosphorylated on its key tyrosine residues, Tyr397 and Tyr576, in only aggressive uveal and cutaneous melanoma cells, which correlates with their increased invasion, migration, and vasculogenic mimicry plasticity. Additionally, we confirmed the presence of FAK phosphorylated on Tyr397 and Tyr576 in both cutaneous and uveal melanoma tumors in situ. Examination of a functional role for FAK in aggressive melanoma revealed that disruption of FAK-mediated signal transduction pathways, through the expression of FAK-related nonkinase (FRNK), results in a decrease in melanoma cell invasion, migration, and inhibition of vasculogenic mimicry. Moreover, we found that FRNK expression resulted in a down-regulation of Erk1/2 phosphorylation resulting in a decrease in urokinase activity. Collectively, these data suggest a new mechanism involved in promoting the aggressive melanoma phenotype through FAK-mediated signal transduction pathways, thus providing new insights into possible therapeutic intervention strategies.     

Molecular pathways mediating liver metastasis in patients with uveal melanoma

Uveal melanoma arises from melanocytes located in the uveal tract of the eye and is the most common primary intraocular tumor in adults. Metastatic liver disease is the overwhelming cause of death in uveal melanoma patients, with almost 50% of patients developing liver metastases up to 15 years after diagnosis. Most of these patients do not present with any evidence of overt metastasis at the time of initial diagnosis although it is assumed that they have undetectable micrometastases. Currently, there are no therapeutic modalities to prevent or efficiently treat the metastatic disease in uveal melanoma patients. Recent discoveries have shed light on the molecular pathways that may contribute to the progression of liver metastasis. The aim of this review is to describe new insights into the genetic and molecular pathways that may play a role in the development of liver metastases in uveal melanoma patients.     

A metastasis modifier locus on human chromosome 8p in uveal melanoma identified by integrative genomic analysis.

PURPOSE: To identify genes that modify metastatic risk in uveal melanoma, a type of cancer that is valuable for studying metastasis because of its remarkably consistent metastatic pattern and well-characterized gene expression signature associated with metastasis. EXPERIMENTAL DESIGN: We analyzed 53 primary uveal melanomas by gene expression profiling, array-based comparative genomic hybridization, array-based global DNA methylation profiling, and single nucleotide polymorphism-based detection of loss of heterozygosity to identify modifiers of metastatic risk. A candidate gene, leucine zipper tumor suppressor-1 (LZTS1), was examined for its effect on proliferation, migration, and motility in cultured uveal melanoma cells. RESULTS: In metastasizing primary uveal melanomas, deletion of chromosome 8p12-22 and DNA hypermethylation of the corresponding region of the retained hemizygous 8p allele were associated with more rapid metastasis. Among the 11 genes located within the deleted region, LZTS1 was most strongly linked to rapid metastasis. LZTS1 was silenced in rapidly metastasizing and metastatic uveal melanomas but not in slowly metastasizing and nonmetastasizing uveal melanomas. Forced expression of LZTS1 in metastasizing uveal melanoma cells inhibited their motility and invasion, whereas depletion of LZTS1 increased their motility. CONCLUSIONS: We have described a metastatic modifier locus on chromosome 8p and identified LZTS1 as a potential metastasis suppressor within this region. This study shows the utility of integrative genomic methods for identifying modifiers of metastatic risk in human cancers and may suggest new therapeutic targets in metastasizing tumor cells.     

MicroRNA-9 suppresses uveal melanoma cell migration and invasion through the NF-κB1 pathway

The aggressive course of uveal melanoma is believed to reflect its unusually invasive and metastatic nature, which is associated with the nuclear factor kappaB (NF-κB) pathway. MicroRNAs (miRNAs) have been implicated in the regulation of various biological and pathological processes in cancer, however, the special role of miR-9 in uveal melanoma metastasis is largely unknown. In the present study, we showed that miR-9 is significantly reduced in highly invasive uveal melanoma cell lines, and suppressed migration and invasion of highly invasive cells. Furthermore, miR-9 negatively modulated NF-κB1 expression by direct targeting at its 3'-UTRs. Additionally, downstream targets of NF-κB1, such as MMP-2, MMP-9 and VEGFA, were regulated by miR-9 in the same pattern as NF-κB1. Therefore, miR-9 suppresses uveal melanoma cell migration and invasion partly through downregulation of the NF-κB1 signaling pathway.     

RNA interference inhibition of matrix metalloproteinase-1 prevents melanoma metastasis by reducing tumor collagenase activity and angiogenesis

Melanoma incidence is increasing worldwide, and metastatic melanoma is almost completely resistant to every known therapy. New approaches to treating melanoma are urgently needed, and a greater understanding of the biology of melanoma invasion and metastasis will aid in their creation. A high proportion of invasive melanomas have a constitutively active Raf/mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK) signaling cascade; however, the downstream effectors of ERK signaling that contribute to melanoma invasion and metastasis are unknown. ERK signaling drives the production of the interstitial collagenase matrix metalloproteinase-1 (MMP-1), which is expressed specifically by invasive melanomas. Using short hairpin RNAs (shRNA) to knock down MMP-1 expression in a human melanoma cell line, we investigated the role of MMP-1 in melanoma metastasis in a xenograft model. Knockdown of MMP-1 had no effect on primary tumor growth, but reduction of MMP-1 expression significantly decreased the ability of the melanoma to metastasize from the orthotopic site in the dermis to the lung. Mechanistically, tumor cells expressing MMP-1 shRNAs had diminished collagenase activity, which is required for tumor cell invasion. Additionally, attenuation of MMP-1 expression reduced angiogenesis. These results show, for the first time, that targeted inhibition of MMP-1, a single effector of the Raf/MEK/ERK signaling cascade, prevents the progression of melanoma from a primary to metastatic tumor and, as such, may represent a useful therapeutic tool in controlling this disease.     

Immune expression and inhibition of heat shock protein 90 in uveal melanoma.

PURPOSE: To examine the immunohistochemical profile of heat shock protein 90 (Hsp90) in uveal melanoma and the cytotoxicity of an Hsp90 inhibitor, 17-allylamino-17-demethoxygeldanamycin (17-AAG), in uveal melanoma cell lines. EXPERIMENTAL DESIGN: Hsp90 expression was determined by immunohistochemistry in 44 paraffin-embedded sections of primary human uveal melanoma and in five uveal melanoma cell lines (92.1, OCM-1, MKT-BR, SP6.5, and UW-1). Sulforhodamine B-based proliferation assay was used to compare uveal melanoma cell growth with a range of concentrations of 17-AAG. Changes in cell migration, invasion, cell cycle fractions, and apoptotic activity were also evaluated. Expression of intracellular proteins was determined by Western blot analysis after 17-AAG exposure. RESULTS: Immunohistochemical expression of Hsp90 was identified in 68% of the paraffin-embedded sections and significantly associated with largest tumor dimension (P = 0.03). 17-AAG significantly reduced the proliferation rates of uveal melanoma cell lines, with concentrations of 100 to 0.1 micromol/L. 17-AAG also significantly reduced the migratory and invasive capabilities of uveal melanoma cell lines. Cell cycle analysis showed that 17-AAG induced accumulations of cells in G(1). Caspase-3 protease activity analysis, a marker for apoptosis, showed a significant increase after drug exposure. The cytotoxic effect of 17-AAG was associated with decreased levels of phosphorylated Akt and cyclin-dependent kinase 4. CONCLUSIONS: The immunohistochemical expression of Hsp90 in uveal melanoma indicates worse prognosis. To the best of our knowledge, this is the first report showing the inhibitory effect on uveal melanoma cells using 17-AAG to target Hsp90. Therefore, Hsp90 may be used as a potential target for treatment of patients with uveal melanoma.     

Variates of survival in metastatic uveal melanoma.

PURPOSE: The course and outcome of metastatic uveal melanoma are not well described. We evaluated the survival of our patients with metastatic uveal melanoma, described factors that correlated with survival, and evaluated the influence of screening tests on time of detection and survival. PATIENTS AND METHODS: All patients with metastatic uveal melanoma seen at Memorial Sloan-Kettering Cancer Center between 1994 and 2004 were identified from our database. We recorded date of initial diagnosis, date of metastatic disease, date of last follow-up, site of the first metastasis, how the first metastasis was discovered, treatment, and outcome of therapy. RESULTS: The estimated median survival of the 119 patients analyzed was 12.5 months; 22% of patients were alive at 4 years. Five variates correlated independently with prolonged survival: Lung/soft tissue as only site of first metastasis, treatment with surgery or intrahepatic therapy, female sex, age younger than 60, and a longer interval from initial diagnosis to metastatic disease. Discovering metastatic disease in asymptomatic patients did not correlate with overall survival; 89% of patients had a single organ as the site of first metastasis. Although liver was the most common site, 39.5% of patients had nonliver sites, most commonly lung, as the first site of metastasis. CONCLUSION: A substantial subset of patients with metastatic uveal melanoma survive more than 4 years with metastatic disease. Data on variates of survival and site of first metastasis may guide strategies for screening patients, although our data failed to show a survival advantage in discovering asymptomatic metastatic disease.     

Insulin-like growth factor binding protein 3 as an anticancer molecule in Ewing's sarcoma

The IGF/IGF-IR system plays a major role in the pathogenesis and progression of Ewing's sarcoma. In this article, the authors evaluated whether the insulin-like growth factor binding protein-3 (IGFBP-3), a molecule with growth-inhibitory and proapoptotic activities, may be exploited for therapeutic applications in the treatment of Ewing's sarcoma (EWS). Expression of IGFBP-3 was analyzed in a panel of EWS cell lines and clinical samples. Parameters related to malignancy (growth in anchorage-independent conditions, migration, invasion and angiogenesis properties) were studied to establish the potential in vitro anticancer effects of exogenous IGFBP-3. The activity of the molecule against metastasis was analyzed by taking advantage of selected clones in which IGFBP-3 endogenous production was induced by gene transfection. The authors observed a generally low expression of IGFBP-3 either in a panel of EWS cell lines or clinical samples. Exogenous IGFBP-3 remarkably inhibits EWS growth, both in monolayer and anchorage-independent conditions, and significantly reduces cell motility. Forced expression of IGFBP-3 in TC-71 EWS cells confirms the growth and migratory effects observed with the exogenous protein, decreases the production or activity of the matrixmetalloprotease MMP-9 and vascular endothelial factor (VEGF)-A and abrogates EWS metastasis ability. IGFBP-3 acts mainly through IGF-dependent mechanisms and the protein may therefore represent an alternative strategy to inhibit IGF-IR functions. The data indicate IGFBP-3 as a molecule of therapeutic potential in EWS.     

Monoclonal antibody 4C5 immunostains human melanomas and inhibits melanoma cell invasion and metastasis.

PURPOSE: Tumor cell metastasis constitutes a major problem in the treatment of cancer. Because the cure rate of metastatic tumors is very low, new therapeutic approaches are needed. Heat shock protein 90 (HSP90) is a molecular chaperone that is recognized as a new target for the treatment of cancer. Here, we examine the value of a monoclonal antibody (mAb) against HSP90, mAb 4C5, as a potential marker in malignant melanomas. Moreover, we investigate the possibility to use mAb 4C5 as an inhibitor of melanoma cell invasion and metastasis. EXPERIMENTAL DESIGN: Paraffin blocks of formalin-fixed human melanoma tumor tissues were used to prepare tissue microarrays. The B16 F10 melanoma cell line was used in all the in vitro experiments. To assess melanoma cell invasion, the wound-healing assay and the Matrigel invasion assay were applied. To evaluate the effect of mAb 4C5 on tumor metastasis, we used an experimental model of metastatic melanoma. RESULTS: Immunohistochemical studies done on a panel of malignant melanomas showed positive immunostaining with mAb 4C5 in all cases. mAb 4C5 inhibits B16 F10 cell invasion by binding to surface HSP90 because it is not internalized. mAb 4C5 significantly inhibits melanoma metastasis in C57BL/6 mice inoculated with B16 F10 cells. CONCLUSIONS: mAb 4C5 could be potentially used as a novel specific marker for malignant melanomas. mAb 4C5 inhibits melanoma cell invasion in vitro by binding to cell surface HSP90 expressed on B16 F10 melanoma cells. Finally, this antibody significantly inhibits melanoma metastasis, thus rendering it a potential therapeutic agent for the treatment of cancer metastasis.     

Characterization of gangliosides in human uveal melanoma cells

We have evaluated the ganglioside composition of 20 primary uveal melanomas, of 2 cell lines derived from 2 uveal melanomas, of a liver metastasis from an uveal melanoma, and of 8 normal choroids. The results show that normal choroid tissue has a ganglioside content similar to the primary tumors of uveal melanoma except for GD1a, GD1b, and GT1b, which are present only on normal choroid tissues. On the other hand, the uveal melanomas have similarities with cutaneous melanomas, since GM3 (74%) and GD3 (25%) are found in both tissues and are present in about the same amounts. However, GM1 was found in 50%, GM2 in 20% and GD2 in none of the uveal melanomas. According to data published by others, cutaneous melanoma biopsies have no GM1, whereas GM2 is present in 100% and GD2 in 71% of tumor tissues. Transplantation of the 2 cell lines subcutaneously into nude mice resulted in the growth of tumors which had a ganglioside profile larger than that of the primary tumors. GM3 was significantly diminished and GD3 significantly increased in the primary uveal melanoma from patients who had received radiotherapy before enucleation compared with those who did not have radiotherapy. These results show that uveal melanomas contain gangliosides that could be used as targets for monoclonal antibody therapy.     

Uveal melanoma

Uveal melanoma, which arises from melanocytes residing in the stroma, is the most common primary intraocular tumor in adults. Up to 50% of patients with primary uveal melanoma will ultimately develop distant metastasis, the liver being involved in up to 90% of individuals and the median survival reported to be 4-5 months. The current treatment of metastatic uveal melanoma is limited by the lack of effective systemic therapy. The intrinsic resistance of uveal melanoma to conventional systemic chemotherapy has led researchers to evaluate new approaches. Molecular biology and a better knowledge of cancer cells allowed the development of target therapies: these refer to drugs designed to interact with a specific molecular pathway known to have a critical role in tumor growth or progression. Several drugs, such as bevacizumab, imatinib and MEK-inhibitors, are currently under investigation as single agents or in combination with chemotherapeutic drugs for the treatment of metastatic uveal melanoma. Finally, ipilimumab, which targets the immune compartment, was reported to increase overall survival in cutaneous melanoma patients, with preliminary evidence of similar activity in ocular melanoma.     

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.     

Major cytogenetic aberrations and typical multidrug resistance phenotype of uveal melanoma: current views and new therapeutic prospects

Uveal melanoma is the most frequent intra-ocular cancer. The recent development of new chromosome-related technologies have permitted the elucidation of both the cytogenetics and the natural history of this disease. Fifty to 60% of uveal melanomas are linked to a monosomy 3, which appears as an early and determinant event in tumor progression. Tumors with this anomaly have a very poor prognosis. Recent work suggests that this category of uveal melanoma represents a distinct pathologic entity from that associated with normal disomy 3. Chromosome 6 aberrations probably constitute a second entry point into the process of cancerogenesis, while gains in 8q seem to appear later in the natural history of uveal melanomas due to their higher frequency in larger tumors. Other anomalies will be reviewed. In spite of significant improvements in the local treatment of uveal melanoma, many patients die due to tumor metastasis. This disease is characterized by a constitutive chemoresistance whose typical multidrug resistance phenotype (MDR) is particularly complex since different combinations of several resistance proteins are simultaneously produced. Regulation of the expression of these proteins is a research priority, increasingly so as gene therapy-dependent chemosensitization strategies expand. Therefore, the development and improvement of methods to determine the chemoresistance profile become a crucial objective today in the therapeutic strategies against uveal melanoma.     

Circulating tumor cells in uveal melanoma

Despite advances in the diagnosis and local tumor control, the overall mortality rate for uveal melanoma remains high because of the development of metastatic disease. The clinical and histopathological systems currently being used to classify patients are not sufficiently accurate to predict metastasis. Tumor genotyping has demonstrated significant promise but obtaining tumor tissue can be problematic. Furthermore, assessment of tumor tissue does not indicate whether tumor cells have actually been shed and cannot indicate whether treatment is reducing metastasis. The detection of circulating tumor cells in blood has been shown to be a prognostic biomarker that can be used to monitor the effectiveness of therapy in patients with metastatic carcinoma. Uveal melanoma disseminates hematogenously, and the detection of circulating melanoma cells may potentially be useful for diagnosis, risk stratification, and the monitoring of disease progression and treatment efficacy. PCR-based and immunomagnetic cell isolation techniques, derived from studies in patients with cutaneous melanoma, have been tested. For various biological and technical reasons, they have not demonstrated the accuracy and reproducibility required for an effective prognostic assay in patients with uveal melanoma. Assessments have been confounded by false positives and negatives and thus, correlations between circulating melanoma cells and survival have not yet been established. Circulating melanoma cell detection is a valuable tool for investigating metastasis in uveal melanoma and also has the potential to become a standard part of uveal melanoma management. However, more research on the biology of uveal melanoma as well as improvements upon the current technologies are needed.