[Immunohistochemical detection of the gene p53 and p21 expression in cells of the malignant melanoma of the uvea]

AIM

To examine by means of immunohistochemistry the expression of the tumor suppressing gene p53 and gene p21 in cells of malignant melanoma of the uvea from formalin-paraffin material from patients, who were during the period 2000 - 2006 surgically treated due to malignant melanoma of the uvea at the Department of Ophthalmology in the University Hospital in Brno (Brunn), Czech Republic, E.U., and to correlate the results of the immunohistochemical detection with clinical signs of the tumor of each patient.

METHODS

Twenty-nine malignant melanomas of the uvea were examined by means of monoclonal antibody DO-1 (Novocastra company) and all 29 samples of malignant melanoma of the uvea were immunohistochemically examined for the p21 gene expression by means of the monoclonal antibody SX 118 (DAKO company). We evaluated the percentage of positive nuclei and the intensity of the staining in immunohistochemically detected p53 and p21 genes expression.

RESULTS

Results suitable for evaluation we obtained in 28 samples of malignant melanomas, one sample was not suitable for evaluation due to extremely high presence of melanin pigment. In 3 patients, weak nuclear p53 gene expression was detected in 5-15% of cells, in 1 patient, the very weak intensity of staining in 5-15% of cells was found. In three patients, in 5-15% of cells, weak expression of p21 gene, and in one patient, very weak expression of p21 gene in 5-15% of cells (in all 4 cases, the p53 expression was established) were found. In one of those 4 patients with p53 gene expression it was the malignant melanoma of the iris, in one of them it was malignant melanoma of the ciliary body, and in 2 of them it was malignant melanoma of the choroid.

CONCLUSION

The expression of the p53 gene and the expression of the gene p21 were established in 4 out of 28 patients (14.3%). From the above-mentioned results we can assume that stabilizing mutations of p53 gene are rare in the melanoma of the uvea. The proved expression p53 in 4 patients is probably result of the expression of the standard (wild-type) p53 gene, especially according to the ability to induce the expression of p21 gene. In our group, there were not proved marked nuclear accumulation of p53, which would suggest the presence of p53 gene mutation.

Expression and distribution of MMPs and TIMPs in human uveal melanoma

Matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) are involved in tumour invasion, metastasis and angiogenesis, and have been implicated as progression markers in uveal melanoma, although their topographical expression has not been fully described. In this study we compared the distribution and specificity of several classes of MMPs (MMP-1, -2, -9, -19, and MT1-MMP) and physiological MMP inhibitors (TIMP-2 and -3) in different regions of the tumour microenvironment and adjacent choroid in a series of primary uveal melanomas. Paraffin sections of untreated uveal melanomas (n=18, 3/18 spindle; 11/18 mixed, and 4/18 epithelioid) were examined for MMP-1 (collagenase 1), MMP-2 and MMP-9 (gelatinases A and B), MT1-MMP (membrane-type 1-MMP), MMP-19, TIMP-2 and TIMP-3 (tissue inhibitors of MMPs), using indirect peroxidase immunohistochemistry. The distribution and intensity of immunolabelling was graded semi-quantitatively (0-3) by 2 independent observers. Non-parametric analyses were used to test for associations between tumour cell type, and the average grade of MMP or TIMP expression. Immunostaining for MMP-1, -9, -19 and MT1-MMP was > or =Grade 2 in more than 70% of specimens, and a heterogeneous pattern of MMP-1, -9, MT1-MMP and TIMP-3 expression was observed. At the tumour-scleral interface (TSI), melanoma cells had a flattened morphology and a much reduced MMP and TIMP expression, with a high expression in tumour areas adjacent to the TSI. Tumour vasculature and stromal cells strongly expressed MMP-2. We also observed heterogeneous immunostaining of the vasculature by MMP-1, -9, MT1-MMP and TIMP-2 antibodies, and of the extravascular matrix by MMP-9 antibody. The distinct immunostaining patterns observed for MMPs and TIMPs within uveal melanoma are consistent with their involvement in tumour growth and angiogenesis. In particular, the heterogeneous expression within regions of the tumours, and the localized expression in vasculature and stromal cells emphasises the importance of the tumour microenvironment in the pathogenesis of uveal melanoma (and other tumours).

Multinodular goiter and primary hyperparathyroidism: a circuitous route to diagnosing metastatic uveal melanoma

Uveal melanoma spreads exclusively via a hematogenous route and is notable for its latency. Liver metastases are common; however, metastatic spread to unusual sites has been encountered. We report the case of metastatic uveal melanoma in a woman with multinodular goiter and primary hyperparathyroidism. The patient presented with hypercalcemia and an elevated intact parathyroid hormone level, in conjunction with a follicular neoplasm in the setting of goiter. She underwent an uneventful total thyroidectomy and parathyroidectomy. Postoperatively, she became normocalcemic. Histopathologic analyses revealed metastatic uveal melanoma cells within both the multinodular goiter and parathyroid adenoma. At present, she is enrolled in a phase II trial for disseminated uveal melanoma. This is a report of uveal melanoma metastatic to both a parathyroid adenoma and a nodular hyperplastic thyroid. Additionally, this case serves to display the unusual metastatic potential of uveal melanoma.

A role for EZH2 in silencing of IFN-gamma inducible MHC2TA transcription in uveal melanoma

We investigated the contribution of epigenetic mechanisms in MHC2TA transcriptional silencing in uveal melanoma. Although no correlation was observed between impaired CIITA transcript levels after IFN-gamma induction and DNA methylation of MHC2TA promoter IV (CIITA-PIV), an association was found with high levels of trimethylated histone H3-lysine 27 (3Me-K27-H3) in CIITA-PIV chromatin. The 3Me-K27-H3 modification correlated with a strong reduction in RNA polymerase II-recruitment to CIITA-PIV. Interestingly, we observed that none of these epigenetic modifications affected recruitment of activating transcription factors to this promoter. Subsequently, we demonstrated the presence of the histone methyltransferase EZH2 in CIITA-PIV chromatin, which is known to be a component of the Polycomb repressive complex 2 and able to triple methylate histone H3-lysine 27. RNA interference-mediated down-regulation of EZH2 expression resulted in an increase in CIITA transcript levels after IFN-gamma induction. Our data therefore reveal that EZH2 contributes to silencing of IFN-gamma-inducible transcription of MHC2TA in uveal melanoma cells.

Expression of nm23-H1 in uveal melanoma

Uveal melanoma (UM) is the most common malignant intraocular tumor in adults. Despite the high accuracy of clinical diagnosis and advances in local treatment, more than 50% of UM patients develop metastasis within 10 years of initial diagnosis. NM23 is one of the human metastasis suppressor genes. Reduced nm23-H1 expression is correlated with high metastatic potential in many different cancers. The purpose of this study is to investigate the expression of nm23-H1 in UM and its potential value as a prognostic marker. Immunostaining of nm23-H1 was verified in five human UM cell lines with different metastatic potentials. The expression level of nm23-H1 mRNA was evaluated with one-step quantitative real-time PCR. The invasion ability of the cell lines was assessed before and after silencing nm23-H1 with small interference RNA. Thirty-two cases of paraffin-embedded specimens of human UM were immunostained with nm23-H1 monoclonal antibody. The immunostaining was evaluated in a semiquantitative fashion based on extent and intensity. The real-time PCR results of five human UM cell lines showed that expression of nm23-H1 was higher in cell lines with low metastatic potential compared with those with high metastatic potential (P<0.05). The invasive ability of the UM cell lines increased after silencing nm23-H1 expression with small interference RNA (P<0.05). The immunostaining of nm23-H1 was cytoplasmic in all cell lines and UM patients samples. The increased immunostaining intensity of nm23-H1 in patients' samples was associated with better survival rate (Kaplan-Meier test P=0.0097). The expression of nm23-H1 was not correlated with other prognostic factors. It can be concluded that nm23-H1 may be a prognostic marker to predict the survival rate of UM patients and it has the potential to identify high-risk patients.

Expression of melanin-related genes in cultured adult human retinal pigment epithelium and uveal melanoma cells

PURPOSE

Controversy exists over melanogenesis of adult human RPE cells in vitro. This study investigated melanin content and production and expression of tyrosinase (TYR), tyrosinase-related-protein-1 (TRP1), tyrosinase-related-protein-2 (TRP2), and P gene in cultured human RPE cells and uveal melanoma cells.

METHODS

RPE cells were isolated and cultured from three adult donor eyes. A continuous human uveal melanoma cell line was established from primary choroidal melanoma. Melanin content and production were measured, and the expression of TYR, TRP1, TRP2, and P gene at the mRNA and protein levels were detected by RT-PCR and western blot, respectively.

RESULTS

Melanin content per cell of cultured RPE decreased rapidly and in proportion to cell division. No melanin production could be demonstrated in any passages. In cultured RPE cells, mRNA expression of TYR, TRP1, TRP2, and P-gene and protein expression of TYR, TRP1, and TRP2 could not be detected. In uveal melanoma cells, melanin content per cell remained stable, and melanin production could be detected in each passage. Expression of mRNA of TYR, TRP1, TRP2, and P-gene and protein of TYR, TRP1, and TRP2 could be detected in melanoma cells.

CONCLUSIONS

Human RPE cells under standard culture circumstances do not produce melanin and do not express the four key genes required in melanin biosynthesis pathway. In contrast, human uveal melanoma cells produce melanin and express all of these melanogenic genes in vitro.

Decitabine up-regulates S100A2 expression and synergizes with IFN-gamma to kill uveal melanoma cells

PURPOSE

Metastatic uveal melanoma is resistant to conventional chemotherapy and immunotherapy. In this study, we investigated the responsiveness of uveal melanoma cell lines to IFNs and the hypomethylating agent decitabine.

EXPERIMENTAL DESIGN

The uveal melanoma cell lines 92-1, UW-1, OCM-1, and MKT-BR were exposed to varying concentrations of IFN-alpha, IFN-gamma, and decitabine, alone and in combination. The effects of decitabine on gene expression were examined using DNA microarray analysis.

RESULTS

We found that IFN-gamma and decitabine induced cell death in uveal melanoma. Whereas a high concentration of IFN-gamma (1,000 units/mL) was required to induce cell death, we observed a dose-related increase in cell death when decitabine was used at a range of 0.1 to 10 micromol/L. Strikingly, 1 micromol/L decitabine synergized with 10 to 1,000 units/mL IFN-gamma to induce massive cell death. In contrast, decitabine had no effect on three cutaneous melanoma cell lines and exhibited no synergy with either IFN. In uveal melanoma, decitabine up-regulated the expression of genes involved in growth control and apoptosis and down-regulated genes that have been implicated in the malignant phenotype of cutaneous melanoma. The gene up-regulated to the greatest degree by decitabine and whose expression showed a dose-effect across the three concentrations of decitabine was S100A2, a putative tumor suppressor. The genes modulated by decitabine in uveal melanoma were largely unaffected in cutaneous melanoma.

CONCLUSIONS

These findings form a basis for testing the decitabine/IFN-gamma combination in metastatic uveal melanoma and for exploring the role of S100A2 in the susceptibility of uveal melanoma to IFN-mediated cell death.

Expression and distribution of MUC18 in human uveal melanoma

The immunoglobulin superfamily protein MUC18 is involved in transendothelial migration and signal transduction, and is expressed in malignancies including cutaneous melanoma. Recent in vitro studies showed evidence of increased MUC18 protein in some uveal melanoma cell lines with an increased potential for invasion. We assessed seven uveal and three metastasis-derived melanoma cell lines for the expression of MUC18 mRNA and protein by RT-PCR, and immunoblotting and immunocytochemistry, respectively. We also examined the expression and distribution of MUC18 in paraffin sections of primary uveal melanomas (n = 23; 5/23 spindle; 18/23 mixed and epithelioid) and normal eyes (n = 3) using a polyclonal goat anti-human antibody to MUC18 visualized with peroxidase and Vector NovaRED. Distribution and intensity of immunostaining was graded semi-quantitatively (grade 0 to 3) by 2 independent observers. All cell lines expressed MUC18 mRNA and protein ( approximately 130 kDa), and showed punctate cell membrane MUC18 immunostaining. Primary melanomas displayed heterogeneous cell membrane and cytoplasmic MUC18, with moderate to strong immunolabelling (> or =grade 2) in approximately 70% of tumours. Vasculature in tumours and in retina and choroid of all melanoma-affected and normal eyes showed intense MUC18 immunostaining. These observations further suggest a role for MUC18 in uveal melanoma growth; moreover, interactions between MUC18-positive melanoma cells and vasculature may be important for the hematogenous spread of cells during metastases.

[Study of a role of the expression of a transmembranous CD117/C-Kit receptor in the progression of uveal melanomas]

The authors studied the expression of the protooncogen receptor involved in the regulation of major cell cycle processes in uveal melanoma. The studies performed by a highly sensitive immunohistochemical technique. The findings have allowed the authors to state that the membranous CD117/C-Kit receptor plays an important role in the progression of uveal melanomas. It is suggested that the use of the new drug Glivec is promising in treating uveal melanoma.

Modeling the behavior of uveal melanoma in the liver

PURPOSE

To model the behavior of uveal melanoma in the liver.

METHODS

A 15-muL suspension of metastatic MUM2B or either primary OCM1 or M619 uveal melanoma cells was injected into the liver parenchyma of 105 CB17 SCID mice through a 1-cm abdominal incision. Animals were killed at 2, 4, 6, or 8 weeks after injection. Before euthanatization, 3% FITC-BSA buffer was injected into the retro-orbital plexus of one eye of three mice. Liver tissues were examined by light and fluorescence microscopy, and were stained with human anti-laminin. Vasculogenic mimicry patterns were reconstructed from serial laser scanning confocal microscopic stacks.

RESULTS

OCM1a cells formed microscopic nodules in the mouse liver within 2 weeks after injection and metastasized to the lung 6 weeks later. By contrast, M619 and MUM2B cells formed expansile nodules in the liver within 2 weeks and gave rise to pulmonary metastases within 4 weeks after injection. Vasculogenic mimicry patterns, composed of human laminin and identical with those in human primary and metastatic uveal melanomas, were detected in the animal model. The detection of human rather than mouse laminin in the vasculogenic mimicry patterns in this model demonstrates that these patterns were of tumor cell origin and were not co-opted from the mouse liver microenvironment.

CONCLUSIONS

There are currently no effective treatments for metastatic uveal melanoma. This direct-injection model focuses on critical interactions between the tumor cell and the liver. It provides for translationally relevant approaches to the development of new modalities to detect small tumor burdens in patients, to study the biology of clinical dormancy of metastatic disease in uveal melanoma, to design and test novel treatments to prevent the emergence of clinically manifest liver metastases after dormancy, and to treat established uveal melanoma metastases.

Expression of epidermal growth factor receptor, ezrin, hepatocyte growth factor, and c-Met in uveal melanoma: an immunohistochemical study

The immunoreactivity of epidermal growth factor receptor (EGFR) ezrin, hepatocyte growth factor receptor (HGF), and c-Met was studied in 60 uveal melanomas and was correlated with clinicopathologic parameters. Metastases were diagnosed in the patients with uveal melanoma between 5 years and 8 years (median, 6.5 years) after enucleation. Using Kaplan-Meier statistical analysis, we found a significant association between high c-Met expression and death due to uveal melanoma (p < 0.03). EGFR was expressed in 18 of 60 (30%) tumors; ezrin was expressed in 30 of 60 (50%) tumors. Tumors with liver metastasis (n = 6) showed higher expression of c-Met (p = 0.0009) compared with the tumors with no extension/extrascleral extension without liver metastasis (groups A-45 and B-9). HGF was negative in all the six tumors that had liver metastasis. Further studies are required to understand the possible mechanism of ligand-independent c-Met activation in patients with uveal melanoma.

Transcriptional profiling of human uveal melanoma from cell lines to intraocular tumors to metastasis

Uveal melanoma is the most common primary intraocular tumor in adults and exclusively disseminates haematogenously in order to form metastases. The aim of this study was to measure the transcriptional profiles of human uveal melanoma cells isolated from a primary intraocular tumor, circulating malignant cells (CMCs), and metastases in order to elucidate the changes in gene expression associated with this progression. Human EST microarrays and universal reference RNA were used to measure the differences between tissue samples isolated from an immunosuppressed xenograft rabbit model of uveal melanoma. Cells were isolated from a single rabbit at the time of sacrifice from an intraocular tumor, peripheral blood, and metastasis. RNA was extracted from each sample and subjected to transcriptional profiling analysis. Results were compared to the transcriptional profiles previously obtained from the original cell line used for intraocular injections. Changes were verified using real-time PCR analysis. A total of 314 significant changes in gene expression were seen from the intraocular tumor to metastasis, as determined by transcript abundance. Principle Components Analysis was used to cluster these changes into four distinct groups. An additional 61 statistically significant changes were observed between the recultured and CMCs, with the latter believed to represent an intermediate step in the progression from intraocular tumor to metastasis. In conclusion, we have produced a detailed analysis of the transcriptional changes that take place as human uveal melanoma cells evolve from a primary tumor to metastasis in a xenograft animal model, including the decrease in expression of specific melanoma markers.

Melanocortin 1 Receptor Is Expressed by Uveal Malignant Melanoma and Can Be Considered a New Target for Diagnosis and Immunotherapy

PURPOSE

Uveal melanoma is the most common primary malignant ocular cancer in adults. This tumor has a distinct expression pattern of markers compared with cutaneous melanoma. MC1R is under study as a potential target for antitumor immunity. Because of the potential immunogenicity of MC1R, it is important to evaluate its expression on uveal melanomas.

METHODS

Two novel monoclonal antibodies (MP1.1C11 and MP1.1B7) were used to examine the expression of MC1R in uveal melanomas. Tissue samples obtained from 17 patients were analyzed for expression of MC1R by immunohistochemistry. Additionally, uveal melanoma cell lines were treated with proinflammatory cytokines, after which MC1R cell surface expression was analyzed by flow cytometry.

RESULTS

Results demonstrated that MC1R is expressed by uveal melanoma to a significantly greater extent than other melanoma markers. With the use of MP1.1C11 or MP1.1B7, MC1R was detected in 95% of the tested melanoma tissues, including one liver metastasis. In contrast, MART-1, S100-specific protein, and gp-100 were only expressed by 66%, 33%, and 67% of the analyzed samples, respectively. Results also demonstrated that even though MC1R is mainly located intracellularly, its cell surface expression can be promoted by cytokines such as IFN-gamma, TNF-alpha, IL-4, and IL-10.

CONCLUSIONS

These observations support the inclusion of MC1R in the panel of markers for the diagnosis of uveal melanoma. Therapeutic use of MC1R-specific antibodies targeting cytokine-induced MC1R potentially requires expression of the target molecule on the surfaces of tumor cells. Data presented here support MC1R as a new marker and a putative therapeutic target for uveal melanoma.

Cripto-1 expression in uveal melanoma: an immunohistochemical study

Human Cripto, the founder member of the epidermal growth factor-Cripto-FRL1-Cryptic (EGF-CFC) family, plays an important role during early embryonic development and in particular in carcinogenesis and the development of cancer metastases. Cripto-1 is over-expressed in most cancers, but is absent or only weakly expressed in normal cells. For this reason, Cripto-1 could be of potential value in the targeted treatment. There is no information on the expression of Cripto-1 in human uveal melanoma. Cripto-1 reactivity was evaluated by immunohistochemistry on 36 archival uveal melanomas using the polyclonal antibody to Cripto-1. The tumors were divided in to 2 groups. There were 18 uveal melanomas with no intrascleral or extrascleral extension and 18 uveal melanomas with intrascleral/extrascleral extension/liver metastasis. Cripto-1 reactivity was correlated with tumor aggressiveness and cell type. Furthermore, we studied the immunolocalization of Cripto-1 in 4 uveal melanoma cell lines OCM-1, OCM-8, and 92-1, and OMM-1 and in 2 primary uveal melanocyte cultures. Cripto-1 was expressed in both the non-invasive and aggressive uveal melanomas. Cripto-1 was positive in the 4 uveal melanoma cell lines and absent in the primary uveal melanocyte cultures. Retinal tissue did not express Cripto-1. The results suggest that Cripto-1 is expressed in uveal melanoma, negative in the non-neoplastic ocular tissue and point to its use as a target for therapy.

Prognostic testing in uveal melanoma by transcriptomic profiling of fine needle biopsy specimens

Many uveal melanoma patients die of metastasis despite ocular treatment. Transcriptomic profiling of enucleated tumors can identify patients at high metastatic risk. Because most uveal melanomas do not require enucleation, a biopsy would be required for this analysis. Here, we establish the feasibility of transcriptomic analysis of uveal melanomas from fine needle aspirates. Transcriptomic profiles were analyzed from postenucleation "mock" needle biopsies and matching tumors from eight enucleated eyes and from fine needle aspirates in 17 uveal melanomas before radiotherapy. Predictive accuracy was assessed using a weighted voting classifier optimized for probe set selection using a minimal redundancy/maximum relevance algorithm. Transcriptomic profiles from mock biopsies were highly similar to those from their matching tumor samples (P < 0.0001). Transcriptomic profiles from fine needle aspirates clustered into two classes with discriminating probe sets that overlapped significantly with those for our published classification (P < 0.00001). No loss of predictive accuracy was identified among eight needle aspirates obtained from a distant location. Thus, it is feasible to obtain RNA of adequate quality and quantity to perform transcriptomic analysis on uveal melanoma samples obtained by fine needle biopsy. This method can be applied to specimens obtained from distant geographic locations and can stratify uveal melanoma patients based on metastatic risk.

Expression of vascular endothelial growth factor a, matrix metalloproteinase 9 and extravascular matrix patterns in iris and ciliary body melanomas

PURPOSE

It was the aim of this study to assess the expression of vascular endothelial growth factor (VEGF)-A, matrix metalloproteinase (MMP)-9 and extravascular matrix patterns (EMPs) in iris and ciliary body melanomas and their correlations with histopathologic parameters.

METHODS

The study was conducted on 3 iris and 15 ciliary body melanomas. All tumors were subjected to immunohistochemical techniques for VEGF-A and MMP-9 expressions, the presence of EMPs was assessed, and routine paraffin sections were stained with hematoxylin-eosin. Cell type, tumor localization, degree of pigmentation, necrosis, mitotic index, lymphocytic infiltration and sclera invasion were analyzed using light microscopy.

RESULTS

The mean patient age at the time of treatment was 43 years (range 19-69, median 39.5); 10 (55.6%) patients were males and 8 (44.4%) females. Histopathological cell types were spindle cells in 55.6%, mixed cells in 16.7%, and epithelioid cell types in 27.8% of tumors. Positive reaction for VEGF-A and MMP-9 was present in 66.7 and 72.3% of the tumors, respectively. Microvascular loops and/or networks were seen in 33.4% of the tumors, with the remaining 66.7% of tumors displaying one or more of the other patterns. Metastatic disease developed in only 1 patient during follow-up. Tumor cell type, tumor size, mitotic rate, degree of pigmentation and EMPs were not correlated with metastasis.

CONCLUSIONS

This study suggests that VEGF-A and MMP-9 were positive in the majority of iris and ciliary body melanomas. No correlation was found between VEGF-A and MMP-9 immunoreactivity and EMPs and occurrence of metastases in cases of anterior uveal melanoma.

Report of two cases of ciliary body mesectodermal leiomyoma: unique expression of neural markers

OBJECTIVE

Mesectodermal leiomyoma of the ciliary body is a rare tumor with, to our knowledge, only 15 cases reported in the literature. It has a neural histopathologic appearance and a presumed origin from neural crest.

DESIGN

Case report.

RESULTS

Two cases of mesectodermal leiomyoma with histopathologic and immunohistochemical confirmation are reported.

CONCLUSIONS

For the second time, we were able to demonstrate expression of neural immunohistochemical markers in this tumor.

Vascular endothelial growth factor a in eyes with uveal melanoma

OBJECTIVES

To determine the presence of vascular endothelial growth factor A (VEGF-A) in the aqueous humor of eyes with uveal melanoma and to identify its source.

METHODS

The VEGF-A concentrations were determined in aqueous humor samples obtained after enucleation from 74 eyes with untreated uveal melanoma and from 8 eyes with treated uveal melanoma. Patient survival and clinical and histopathological tumor variables were compared. In situ hybridization, Western blot analysis, and enzyme-linked immunosorbent assay were used to determine expression of VEGF-A in tumor tissue and in overlying retina.

RESULTS

Aqueous VEGF-A concentrations ranged from 18 to 826 pg/mL in 74 untreated eyes, while concentrations in 30 control eyes were significantly lower (median, 50.1 pg/mL) (P<.001). Concentrations in 8 treated eyes were much higher (median, 364 pg/mL). In situ hybridization on tissue sections and Western blot analysis and enzyme-linked immunosorbent assay on tissue extracts revealed VEGF-A in uveal melanoma tissue and in retinal tissue.

CONCLUSIONS

Uveal melanoma is associated with increased concentrations of VEGF-A in aqueous humor. Aqueous VEGF-A concentration correlates with largest basal tumor diameter and with the tumor height. In eyes with uveal melanoma, tumor and retinal tissues are sources of VEGF-A.

Neoplastic transformation of ciliary body epithelium is associated with loss of opticin expression

BACKGROUND

Opticin is a recently discovered glycoprotein present predominantly in the vitreous humour. It is synthesised and secreted by the ciliary body epithelium (CBE) from the initiation of CBE development in the embryo, and production continues throughout life.

AIM

To determine whether a variety of ciliary body tumours synthesise opticin to characterise further its role in ciliary body health and disease.

METHODS

Immunohistochemistry was used to determine the distribution of opticin in normal human CBE, and in hyperplastic and neoplastic CBE lesions.

RESULTS

Opticin was immunolocalised to the basal cell surface and basement membrane material of the non-pigmented CBE in nine donor eyes as well as four hyperplastic lesions of the CBE (Fuchs's adenoma). By contrast, none of eight neoplastic lesions (two adenoma and six adenocarcinoma) of CBE stained for opticin.

CONCLUSION

The present series supports the theory that opticin is produced by the non-pigmented CBE throughout adult life. Loss of opticin expression by this tissue is associated with and could contribute towards neoplastic transformation.

Increased chondroitin sulphate proteoglycan expression (B5 immunoreactivity) in metastases of uveal melanoma

BACKGROUND

Metastatic uveal melanoma has a poor prognosis and limited therapeutic options. Proteoglycans are involved in tumor cell invasion and metastatic behavior. The mAbB5 stains a chondroitin sulphate proteoglycan (CSPG) on cutaneous melanoma cells. Here, we compare the B5-staining of CSPG in primaries and metastases of uveal melanoma.

MATERIAL AND METHODS

Immunohistopathological staining was performed in 15 cutaneous and 39 uveal melanoma samples. A score for intracellular and surface staining was established. B5 staining was compared in primaries and metastases of uveal melanoma using Student's t-test.

RESULTS

Eight of 11 (73%) uveal melanoma metastases were positive for B5-staining whereas only 5 of 28 (18%) primary uveal melanoma samples were B5-positive (P < 0.001). Nine of 15 cutaneous melanoma samples (60%) were B5-positive without significant difference between primary and metastatic lesions. Surface staining was found both on uveal melanoma metastases and cutaneous melanomas.

CONCLUSIONS

CSPG was expressed significantly more often in metastases than in primaries of uveal melanoma. It potentially may be one factor associated with metastatic spread. Further studies are needed to determine its use as prognostic factor. The mAbB5 may also be a promising tool for immunotherapy due to its strong staining of CSPG on the surface of cutaneous and metastatic uveal melanoma cells.

Targeting pericytes diminishes neovascularization in orthotopic uveal melanoma in nerve/glial antigen 2 proteoglycan knockout mouse

In this investigation, we explored whether knockout of nerve/glial antigen 2 (NG2), a pericyte component, inhibited neovascularization and growth of uveal melanoma xenografts. For this, we used multichannel laser scanning confocal microscopy and quantitative image analysis. Orthotopic human uveal melanoma (OCM-1A) xenografts were induced in NG2 knockout and wild-type mice, which were immunosuppressed with cyclosporin A. Inhibition of pericytes through NG2 proteoglycan decreased neovascularization and tumor end volume, rendering pericytes and NG2 proteoglycan potential cellular and molecular therapeutic targets in uveal melanoma.

Functional gene expression analysis uncovers phenotypic switch in aggressive uveal melanomas

Microarray gene expression profiling is a powerful tool for generating molecular cancer classifications. However, elucidating biological insights from these large data sets has been challenging. Previously, we identified a gene expression-based classification of primary uveal melanomas that accurately predicts metastatic death. Class 1 tumors have a low risk and class 2 tumors a high risk for metastatic death. Here, we used genes that discriminate these tumor classes to identify biological correlates of the aggressive class 2 signature. A search for Gene Ontology categories enriched in our class-discriminating gene list revealed a global down-regulation of neural crest and melanocyte-specific genes and an up-regulation of epithelial genes in class 2 tumors. Correspondingly, class 2 tumors exhibited epithelial features, such as polygonal cell morphology, up-regulation of the epithelial adhesion molecule E-cadherin, colocalization of E-cadherin and beta-catenin to the plasma membrane, and formation of cell-cell adhesions and acinar structures. One of our top class-discriminating genes was the helix-loop-helix inhibitor ID2, which was strongly down-regulated in class 2 tumors. The class 2 phenotype could be recapitulated by eliminating Id2 in cultured class 1 human uveal melanoma cells and in a mouse ocular melanoma model. Id2 seemed to suppress the epithelial-like class 2 phenotype by inhibiting an activator of the E-cadherin promoter. Consequently, Id2 loss triggered up-regulation of E-cadherin, which in turn promoted anchorage-independent cell growth, a likely antecedent to metastasis. These findings reveal new roles for Id2 and E-cadherin in uveal melanoma progression, and they identify potential targets for therapeutic intervention.

Expression of p53-induced apoptosis effector PERP in primary uveal melanomas: downregulation is associated with aggressive type

Expression of PERP (p53 apoptosis effector related to PMP-22) was investigated in primary uveal melanomas and its variation was analyzed in relation to clinico-pathological and cytogenetical characteristics of these tumors. The transcriptional level of PERP gene was measured by quantitative real-time RT-PCR in 26 uveal melanomas with known chromosomes 3 and 8 status. PERP protein levels were assessed by Western blot analysis of 22 fresh-frozen tumors and by immunohistochemical analysis of 16 paraffin-embedded tumor specimens. Differential expression of PERP was identified in primary choroidal melanoma specimens, both at transcriptional and protein level. Reduced PERP mRNA level was significantly associated with monosomy 3 (two-way ANOVA and t-test, p=0.004) but not with gains in chromosome 8. Transcriptional downregulation of PERP did not present a statistically significant association with ciliary body involvement, size, PAS-positive loops or cell type. Immunoblotting and immunohistochemistry further demonstrated significantly reduced PERP protein level in monosomy 3 melanomas, as compared with disomy 3 tumors. The altered expression of PERP highlighted this apoptosis-specific target of p53 as a possible contributor to apoptosis in uveal melanoma with PERP downregulation being particularly relevant to the aggressive (monosomy 3) type of uveal melanoma. As PERP is a novel type of p53 effector that is likely to stimulate apoptosis through a mechanism distinct from that of Bcl-2-related mitochondrial effectors, further elucidation of its role in uveal melanoma pathogenesis will assist in the design of novel therapeutic approaches aimed at increasing the rate of apoptosis in this tumor.