Verification of EZH2 as a druggable target in metastatic uveal melanoma

BACKGROUND

Hepatic metastasis develops in ~ 50% of uveal melanoma (UM) patients with no effective treatments. Although GNAQ/GNA11 mutations are believed to confer pathogenesis of UM, the underlying mechanism of liver metastasis remains poorly understood. Given that profound epigenetic evolution may occur in the long journey of circulating tumor cells (CTCs) to distant organs, we hypothesized that EZH2 endowed tumor cells with enhanced malignant features (e.g., stemness and motility) during hepatic metastasis in UM. We aimed to test this hypothesis and explore whether EZH2 was a therapeutic target for hepatic metastatic UM patients.

METHODS

Expression of EZH2 in UM was detected by qRT-PCR, Western blotting and immunohistochemistry staining. Proliferation, apoptosis, cancer stem-like cells (CSCs) properties, migration and invasion were evaluated under circumstances of treatment with either EZH2 shRNA or EZH2 inhibitor GSK126. Antitumor activity and frequency of CSCs were determined by xenografted and PDX models with NOD/SCID mice. Hepatic metastasis was evaluated with NOG mice.

RESULTS

We found that EZH2 overexpressed in UM promoted the growth of UM; EZH2 increased the percentage and self-renewal of CSCs by miR-29c-DVL2-β-catenin signaling; EZH2 facilitates migration and invasion of UM cells via RhoGDIγ-Rac1 axis. Targeting EZH2 either by genetics or small molecule inhibitor GSK126 decreased CSCs and motility and abrogated the liver metastasis of UM.

CONCLUSIONS

These findings validate EZH2 as a druggable target in metastatic UM patients, and may shed light on the understanding and interfering the complicated metastatic process.

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.

Targeting Bcl-2/Bcl-XL induces antitumor activity in uveal melanoma patient-derived xenografts

PURPOSE

Uveal melanoma (UM) is associated with a high risk of metastases and lack of efficient therapies. Reduced capacity for apoptosis induction by chemotherapies is one obstacle to efficient treatments. Human UM is characterized by high expression of the anti-apoptotic protein Bcl-2. Consequently, regulators of apoptosis such as Bcl-2 family inhibitors may constitute an attractive approach to UM therapeutics. In this aim, we have investigated the efficacy of the Bcl-2/Bcl-XL inhibitor S44563 on 4 UM Patient-Derived Xenografts (PDXs) and derived-cell lines.

EXPERIMENTAL DESIGN

Four well characterized UM PDXs were used for in vivo experiments. S44563 was administered alone or combined with fotemustine either concomitantly or after the alkylating agent. Bcl-2, Bcl-XL, and Mcl-1 expressions after S44563 administration were evaluated by immunohistochemistry (IHC).

RESULTS

S44563 administered alone by at 50 and 100 mg/kg i.p. induced a significant tumour growth inhibition in only one xenograft model with a clear dose effect. However, when S44563 was concomitantly administered with fotemustine, we observed a synergistic activity in 3 out of the 4 tested models. In addition, S44563 administered after fotemustine induced a tumour growth delay in 2 out of 3 tested xenografts. Finally, IHC analyses showed that Bcl-2, Bcl-XL, and Mcl-1 expression were not modified after S44563 administration.

CONCLUSION

The novel anti-apoptotic experimental compound S44563, despite a relative low efficacy when administered alone, increased the efficacy of fotemustine in either concomitant or sequential combinations or indeed subsequent to fotemustine. These data support further exploration of potential therapeutic effect of Bcl-2/Bcl-xl inhibition in human UM.

CANT1 lncRNA Triggers Efficient Therapeutic Efficacy by Correcting Aberrant lncing Cascade in Malignant Uveal Melanoma

Uveal melanoma (UM) is an intraocular malignant tumor with a high mortality rate. Recent studies have shown the functions of long non-coding RNAs (lncRNAs) in tumorigenesis; thus, targeting tumor-specific lncRNA abnormalities has become an attractive approach for developing therapeutics to treat uveal melanoma. In this study, we identified a novel nuclear CANT1 lncRNA (CASC15-New-Transcript 1) that acts as a necessary UM suppressor. CANT1 significantly reduced tumor metastatic capacity and tumor formation, either in cell culture or in animals harboring tumor xenograft. Intriguingly, XIST lncRNA serves as a potential target of CANT1, and JPX or FTX lncRNA subsequently serves as a contextual hinge to activate a novel CANT1-JPX/FTX-XIST long non-coding (lncing) pathway in UM. Moreover, CANT1 triggers the expression of JPX and FTX by directly binding to their promoters and promoting H3K4 methylation. These observations delineate a novel lncing cascade in which lncRNAs directly build a lncing cascade without coding genes that aims to modulate UM tumorigenesis, thereby specifying a novel "lncing-cascade renewal" anti-tumor therapeutic strategy by correcting aberrant lncing cascade in uveal melanoma.

The RAS-BRAF kinase pathway is not involved in uveal melanoma

An activating mutation has been recently observed in cutaneous melanoma in a downstream component of RAS-BRAF. The most common mutation, occurring in 80% of cutaneous melanoma samples, is a T-to-A transition resulting in a single amino acid substitution (V599E). Since cutaneous and uveal melanoma (UM) have a common origin, we aimed to establish whether activation of the BRAF proto-oncogene is also an important factor in the development of UM. Exons 11 through 18 of the BRAF gene were screened from 33 primary UMs and 11 UM cell lines. Genomic polymerase chain reaction products were evaluated using single-strand conformation polymorphism analysis, followed by sequencing of aberrant products. The most common mutation, T1796A in the kinase domain of BRAF, was not observed in any of the primary UM samples. This mutation was also absent in 10 of the 11 UM cell lines. In one of the UM cell lines, OCM1, the T1796A mutation was present. We conclude that, in contrast to cutaneous melanoma, BRAF does not appear to be involved in the pathogenesis of UM.

Anatomic site-specific patterns of gene copy number gains in skin, mucosal, and uveal melanomas detected by fluorescence in situ hybridization

To assess the differences between melanomas of different location and different etiology, 372 malignant melanomas were brought in a tissue microarray format. The collection included 23 acral and 118 non-acral skin melanomas, 9 mucosal melanomas, 100 uveal melanomas, and 122 melanoma metastases. Fluorescence in situ hybridization (FISH) was used to assess copy number changes of the cyclin D1 (CCND1), MDM2, c-myc (MYC), and HER2 genes. FISH analysis revealed distinct differences between melanomas from different locations. CCND1 amplifications were detected in skin melanomas from sites with chronic sun exposure (6 of 32 cases), acral melanomas (4 of 17 cases), and mucosal melanomas (one of ten cases) but not in uveal melanomas. High-level MDM2 amplifications were exclusively present in acral melanomas (2 of 19 cases). MYC copy number gains were detected in 32 of 71 uveal melanomas, five of eight mucosal melanomas, and 6 of 67 melanomas from sites with intermittent sun exposure but not in acral melanomas nor melanomas from sites with chronic sun exposure. Alterations of the MYC gene were associated with advanced tumor stage. There were no high-level HER2 amplifications. Site-specific genetic and epigenetic features may impact the response of melanomas to various anti-cancer drugs and should be considered in future studies on the molecular pathogenesis of malignant melanomas.

Tissue-specific expression of beta-catenin in normal mesenchyme and uveal melanomas and its effect on invasiveness

This paper is the first in a series aimed at understanding the role of beta-catenin in epithelial-mesenchymal transformation (EMT) and acquisition of mesenchymal invasive motility. Here, we compare the expression of this and related molecules in the two major tissue phenotypes, epithelial and mesenchymal, the latter including normal avian and mammalian fibroblasts and malignant human uveal melanoma cells. Previously, it was proposed that src initiates EMT by tyrosine phosphorylation of the cadherin/catenin complex resulting in a negative effect on epithelial gene expression. On the contrary, we found that although beta-catenin becomes diffuse in the cytoplasm during embryonic EMT, the cytoplasmic beta-catenin of the embryonic and adult mesenchymal cells we examined is not tyrosine phosphorylated. Pervanadate experiments indicate that cytoplasmic PTPases maintain this dephosphorylation. GSK-3beta is present, but little or no APC occurs in normal and neoplastic mesenchymal cells. The function of the nonphosphorylated cytoplasmic beta-catenin in mesenchyme may be related to invasive motility. Indeed, in order to invade extracellular matrix, transitional (Mel 252) melanoma cells transform from an epithelial to a mesenchymal phenotype with increased cytoplasmic beta-catenin. Moreover, antisense beta-catenin and plakoglobin ODNs inhibit Mel 252 and corneal fibroblast invasion of collagen. All fibroblastic, transitional, and spindle melanoma cells contain nuclear as well as cytoplasmic beta-catenin, but they are not significantly more invasive than normal fibroblasts that contain only cytoplasmic beta-catenin.

Recurrent medulloepithelioma of the ciliary body. Immunohistochemical characteristics

A predominantly benign medulloepithelioma of the ciliary body was diagnosed in an 8-year-old girl and resected by iridocyclectomy. It recurred twice during 30 months. Highly malignant histopathologic features developed, and the eye finally perforated and had to be enucleated. No recurrence or metastases have subsequently developed. Histologically, the tumor was a nonteratoid medulloepithelioma consisting of elements resembling embryonic retina, nonpigmented ciliary epithelium, and neuroblasts, but had also areas of obvious glial and neuronal differentiation as judged by immunohistochemistry. The neuroepithelial tumor cells were positive for neuron-specific enolase, vimentin, and often for S-100 protein. The neuroblastic cells were generally positive for neuron-specific enolase and synaptophysin, but were intermixed with glia-like tumor cells positive for vimentin, glial fibrillary acidic protein, and S-100 protein. The results suggest that even a nonteratoid medulloepithelioma may be, unlike retinoblastoma, a truly multipotential tumor.

TGF-beta in uveal melanoma

Uveal melanoma is the most common primary ocular cancer among adults and patients with distant metastases seldom survive longer than a year. Melanomas of the eye have the advantage of growing in the special environment of an immune privileged site and it has long been shown, that the special immunosuppressive properties of the intraocular microenvironment are strongly mediated by cytokines, especially transforming growth factor-beta (TGF-beta). Here, we sought to investigate the presence of TGF-beta in surgically removed uveal melanoma specimens using immunohistochemical methods to verify possible autocrine mechanisms. Immunocytochemistry for pan-TGF-beta and TGF-beta(2) was performed on 13 melanoma specimens using an alkaline phosphatase labeling procedure. Melanocytic origin of the tumors was confirmed by HMB-45 staining. All tissue samples exhibited positive staining using either pan-TGF-beta or TGF-beta(2) antibody regardless of cell-type, size of the tumor, or tumor location. The intensity of staining did not vary significantly within a given tumor. All tumors stained positive against the HMB-45 antibody. Many cytokines have been found to act on melanoma tumors. The presence of the TGF-beta(2) isoform in all specimens points to progressive tumor-growth as has been shown for melanomas of the skin. Based on our immunohistochemical findings and the immunosuppressive properties of TGF-beta, we suppose that ocular melanomas should be able to create their own immunosuppressive environment even in the uvea, which might be a non-privileged site.

Immunohistochemical assessment of mitotic count in uveal melanoma

BACKGROUND/AIMS

The mitotic count of uveal melanomas correlates with the risk of metastatic death, but with haematoxylin and eosin (H&E)-stained sections, it can be difficult to identify mitotic figures (MF) reliably. We investigated whether this measurement could be enhanced by immunohistochemistry, using the mitosis-specific marker Phospho-Histone H3 Ser10 (PHH3).

METHODS

Formalin-fixed, paraffin-embedded choroidal melanomas from patients treated by enucleation or trans-scleral local resection between 2006 and 2008 were used in this study. Sections from 132 tumours were stained with H&E and PHH3. Mitotic count was defined as the sum of MF counted in 40 high-power fields (HPF). In both H&E and PHH3-stained sections, mitotic count was determined independently by an experienced pathologist (SEC) and by a trainee ophthalmologist (MA). Data were assessed using the Kolmogorov-Smirnov (KS) statistical test and the Bland-Altman (BA) analysis.

RESULTS

The mitotic count determined by SEC in H&E and PHH3-stained sections had median values of 4/40 HPF and 8/40 HPF, respectively (KS, Z = 2.585 p < 0.001; BA, mean difference -5.95 [CI -22.15-10.22]), indicating poor reproducibility between these two methods. Similarly, the mean difference between the H&E and the PHH3 methods for calculating the mitotic count by MA was -7.03 (BA) [CI -23.38-9.31]. In contrast, the median mitotic counts determined by SEC & MA using PHH3 were 8/40 HPF and 9/40 HPF, respectively (KS, Z = 0.308 p = 1; BA, mean difference -0.29 [CI -2.65-2.06]), indicating good reproducibility between examiners.

CONCLUSIONS

MF were more easily identified following immunohistochemical staining with anti-PHH3. This resulted in higher mitotic counts than obtained with H&E sections. For PHH3, the mitotic count determined by a MA was virtually the same as those obtained by an experienced pathologist. PHH3 is now routinely used in our centre, and new prognostic thresholds for uveal melanoma will be defined in further studies.

Copper ionophore elesclomol selectively targets GNAQ/11-mutant uveal melanoma

Unlike cutaneous melanoma, uveal melanoma (UM) is characterized by mutations in GNAQ and GNA11 and remains a fatal disease because there is essentially no effective targeted therapy or immunotherapy available. We report the discovery of the copper ionophore elesclomol as a GNAQ/11-specific UM inhibitor. Elesclomol was identified in a differential cytotoxicity screen of an in-house tool compound library, and its in vivo pharmacological efficacy was further confirmed in zebrafish and mouse UM models. Mechanistically, elesclomol transports copper to mitochondria and produces a large amount of reactive oxygen species (ROS) as Cu(II) is reduced to Cu(I) in GNAQ/11-mutant UM cells, which selectively activates LATS1 kinase in the Hippo signaling pathway and consequently promotes YAP phosphorylation and inhibits its nuclear accumulation. The inactivation of YAP downregulates the expression of SNAI2, which in turn suppresses the migration of UM cells. These findings were cross validated by our clinical observation that YAP activation was found specifically in UM samples with a GNAQ/11 mutation. Furthermore, addition of binimetinib, a MEK inhibitor, to elesclomol increased its synthetic lethality to GNAQ/11-mutant UM cells, thereby overriding drug resistance. This effect was confirmed in an orthotopic xenograft model and in a patient-derived xenograft model of UM. These studies reveal a novel mechanistic basis for repurposing elesclomol by showing that copper homeostasis is a GNAQ/11-specific vulnerability in UM. Elesclomol may provide a new therapeutic path for selectively targeting malignant GNAQ/11-mutant UM.

Heat shock protein expression in the eye and in uveal melanoma

PURPOSE

Expression of heat shock proteins (HSPs) is of prognostic significance in several tumor types, whereas HSPs may also have clinical use as stimulators in tumor vaccination. HSP expression levels were determined in normal eyes and in uveal melanoma and tested whether HSPs expression was associated with prognostic parameters in the uveal melanoma.

METHODS

Expression of HSP27, HSP70, HSP90, and glycoprotein96 (GP96) were determined on paraffin-embedded and frozen sections from seven healthy eyes, 20 primary uveal melanomas without prior treatment, and 18 uveal melanomas after prior treatment. HSP expression was determined by alkaline phosphatase-anti-alkaline phosphatase (APAAP) immunohistochemistry, using appropriate monoclonal antibodies and scored semiquantitatively. Expression of HSPs was validated on retinal tissue of a normal eye and in two uveal melanoma cell lines by Western blot analysis.

RESULTS

Expression of HSPs was observed in epithelial and pigment cells of the normal eyes. In uveal melanoma, the level of expression of HSPs varied. Expression of HSP27 and GP96 was noted in more than 30 of 38 uveal melanomas (with, respectively, a mean of 66% and 53% positive cells). HSP70 and HSP90 were expressed in 6% of tumor cells. The amount of expression of any of the HSP types was not significantly associated with known prognostic factors. There was not a significant difference in expression of the HSPs between uveal melanomas with or without any type of prior treatment.

CONCLUSIONS

In this study, expression of HSPs in uveal melanoma is not correlated with known histopathologic prognostic factors. The high expression of GP96 indicates that this protein is a potential vector in tumor vaccination in patients with large uveal melanomas.

C-myc oncogene expression in ocular melanomas

We have investigated the expression of c-myc in 24 ocular melanomas by immunohistochemistry, using two monoclonal antibodies raised against a mid-sequence portion of the c-myc product (6E10) and against the C-terminus (9E10). The results were compared with other putative prognostic factors, including tumour size, cell type, proliferation index (determined by flow cytometry), and ploidy, as well as immunohistochemical staining for HMB-45 and S-100 antigens. Staining, often focal, for c-myc was found in both the nucleus and the cytoplasm of a proportion of the cells in most tumours studied. Total cell staining for myc protein correlated with proliferative index in diploid tumours; seven out of nine aneuploid and mixed aneuploid/diploid cells showed strong staining in at least one cellular compartment. A positive correlation with myc expression was also found for HMB-45 staining, but not for cell type or staining for S-100. The results support the hypothesis that myc protein is involved in cellular proliferation in uveal melanomas and indicate that immunohistochemistry for myc antigen may be a useful prognostic marker in these tumours.

Ca2+ binding to EF hands 1 and 3 is essential for the interaction of apoptosis-linked gene-2 with Alix/AIP1 in ocular melanoma

Apoptosis-linked gene-2 (ALG-2) encodes a 22 kDa Ca(2+)-binding protein of the penta EF-hand family that is required for programmed cell death in response to various apoptotic agents. Here, we demonstrate that ALG-2 mRNA and protein are down-regulated in human uveal melanoma cells compared to their progenitor cells, normal melanocytes. The down regulation of ALG-2 may provide melanoma cells with a selective advantage. ALG-2 and its putative target molecule, Alix/AIP1, are localized primarily in the cytoplasm of melanocytes and melanoma cells independent of the intracellular Ca(2+) concentration or the activation of apoptosis. Cross-linking and analytical centrifugation studies support a single-species dimer conformation of ALG-2, also independent of Ca(2+) concentration. However, binding of Ca(2+) to both EF-1 and EF-3 is necessary for ALG-2 interaction with Alix/AIP1 as demonstrated using surface plasmon resonance spectroscopy. Mutations in EF-5 result in reduced target interaction without alteration in Ca(2+) affinity. The addition of N-terminal ALG-2 peptides, residues 1-22 or residues 7-17, does not alter the interaction of ALG-2 or an N-terminal deletion mutant of ALG-2 with Alix/AIP1, as might be expected from a model derived from the crystal structure of ALG-2. Fluorescence studies of ALG-2 demonstrate that an increase in surface hydrophobicity is primarily due to Ca(2+) binding to EF-3, while Ca(2+) binding to EF-1 has little effect on surface exposure of hydrophobic residues. Together, these data indicate that gross surface hydrophobicity changes are insufficient for target recognition.

Leiomyoma of the ciliary body extending to the anterior chamber: clinicopathologic and ultrasound biomicroscopic correlation

Leiomyoma of the ciliary body is a rare tumor that often causes a diagnostic dilemma. Sclerouvectomy has been found to be beneficial in the management of iris and ciliary body leiomyoma. We treated a case of leiomyoma of the ciliary body presenting as a fleshy mass in the anterior chamber, removed by partial lamellar sclerouvectomy. Ultrasound biomicroscopic and histopathologic features, including light microscopic, immunohistochemistry, and transmission electron microscopic features, were studied and the literature was reviewed.

Insulin-like growth factor system and sporadic malignant melanoma

Insulin and insulin-like growth factors (IGFs) are important regulators of energy metabolism and growth. Several findings have outlined an important role played by this family of molecules in both tumor maintenance and development. Despite the established contribution of the IGF system in carcinogenesis, little and contrasting data have been reported concerning the intertwined relationships between melanoma and this family of molecules. The present minireview aims to summarize the main topics and evidence concerning this malignant skin cancer, with a focus on the following: i) melanoma and cell proliferation effects induced by the IGF system, ii) in vitro and in vivo experimental data, and iii) targeting studies. Because of consistent findings regarding the role of the IGF-1 receptor in the modulation of IGF-1 activity, possible therapeutic strategies combining the use of antisense oligonucleotides against IGF-1 receptor mRNA could be applied in the future.

ALKBH5-mediated m6A demethylation of FOXM1 mRNA promotes progression of uveal melanoma

In this study, we found that ALKBH5, a key component of the N⁶-methyladenosine (m⁶A) methyltransferase complex, was significantly elevated in uveal melanoma (UM) cell lines and that ALKBH5 downregulation inhibited tumor growth in vivo. High ALKBH5 expression predicted worse outcome in patients with UM. EP300-induced H3K27 acetylation activation increased ALKBH5 expression. Downregulation of ALKBH5 inhibited UM cell proliferation, migration, and invasion and increased apoptosis in vitro. Besides, ALKBH5 may promote UM metastasis by inducing epithelial-to-mesenchymal transition (EMT) via demethylation of FOXM1 mRNA, which increases its expression and stability. In sum, our study indicates that AKLBH5-induced m⁶A demethylation of FOXM1 mRNA promotes UM progression. Therefore, AKLBH5 is a potential prognostic biomarker and therapeutic target in UM.

Chromosome 3 status in uveal melanoma: a comparison of fluorescence in situ hybridization and single-nucleotide polymorphism array

PURPOSE

To compare fluorescence in situ hybridization (FISH) using a centromeric probe for chromosome 3 (CEP3) and 3p26 locus-specific probe with single-nucleotide polymorphism array (SNP-A) analysis in the detection of high-risk uveal melanoma.

METHODS

Fifty cases of uveal melanoma (28 males, 22 females) treated by enucleation between 2004 and 2010 were analyzed. Fresh tissue was used for FISH and SNP-A analysis. FISH was performed using a CEP3 and a 3p26 locus-specific probe. Tumor size, location, and clinical outcome were recorded during the 7-year study period (median follow-up: 35.5 months; mean: 38.5 months). The sensitivity, specificity, positive predictive value, and negative predictive value were calculated.

RESULTS

Monosomy 3 was detected by FISH-CEP3 in 27 tumors (54%), FISH-3p26 deletion was found in 30 (60%), and SNP-A analysis identified 31 (62%) of the tumors with monosomy 3. Due to technical failures, FISH and SNP-A were noninterpretable in one case (2%) and two cases (4%), respectively. In both cases of SNP-A failure, tumors were positive for FISH 3p26 deletion and in a single case of FISH failure, monosomy 3 was found using SNP-A. No statistically significant differences were observed in any of the sensitivity or specificity measures.

CONCLUSIONS

For prediction of survival at 36 months, FISH CEP3, FISH 3p26, and SNP-A were comparable. A combination of prognostication techniques should be used in an unlikely event of technical failure (2%-4%).

BAP1 mutant uveal melanoma is stratified by metabolic phenotypes with distinct vulnerability to metabolic inhibitors

Cancer cell metabolism is a targetable vulnerability; however, a precise understanding of metabolic heterogeneity is required. Inactivating mutations in BRCA1-associated protein 1 (BAP1) are associated with metastasis in uveal melanoma (UM), the deadliest adult eye cancer. BAP1 functions in UM remain unclear. UM patient sample analysis divided BAP1 mutant UM tumors into two subgroups based on oxidative phosphorylation (OXPHOS) gene expression suggesting metabolic heterogeneity. Consistent with patient data, transcriptomic analysis of BAP1 mutant UM cell lines also showed OXPHOShigh or OXPHOSlow subgroups. Integrated RNA sequencing, metabolomics, and molecular analyses showed that OXPHOShigh BAP1 mutant UM cells utilize glycolytic and nucleotide biosynthesis pathways, whereas OXPHOSlow BAP1 mutant UM cells employ fatty acid oxidation. Furthermore, the two subgroups responded to different classes of metabolic suppressors. Our findings indicate that targeting cancer metabolism is a promising therapeutic option for BAP1 mutant UM; however, tailored approaches may be required due to metabolic heterogeneities.

Expression of MAGE, gp100 and tyrosinase genes in uveal melanoma cell lines

In order to determine the possible use of uveal melanoma cell lines as stimulators in immunotherapy, we evaluated the expression of the human genes for MAGE-1, -2 and -3, gp100 and tyrosinase in uveal melanoma cell lines. mRNA expression of the MAGE-1, -2 and -3, gp100 and tyrosinase genes and the HLA class I specificity were determined in five primary and three metastatic uveal melanoma cell lines. Expression of the examined genes was heterogeneous in the primary and metastatic cell lines. The cell lines OCM-1 and OMM-1 expressed MAGE-1, -2 and -3, whereas EOM-3, MEL202, 92-1 and OMM-3 were negative for these antigens. gp100 was expressed in all cell lines, and tyrosinase in all but three (EOM-29, OMM-2 and OMM-3). Except for EOM-3, the HLA-A type of all the cell lines could be determined by complement-dependent microlymphocytotoxicity assay. Since at least two melanoma-associated antigens can be found in uveal melanoma cell lines, as well as the HLA class I molecules, these cell lines may be applicable as immunogens for specific immunotherapy against metastatic uveal melanoma.

PC-10 immunostaining of proliferating cell nuclear antigen in posterior uveal melanoma. Enucleation versus enucleation postirradiation groups

PURPOSE

It is difficult to assess the viability of uveal melanoma after radiotherapy treatment. The purpose of the current study is to investigate PC-10 monoclonal antibody of proliferating cell nuclear antigen as a possible marker for cell proliferation and tumor viability in conventionally processed histologic preparations of uveal melanoma irradiated by brachytherapy as well as in nonirradiated melanomas.

METHODS

Thirteen enucleated eyes with posterior uveal melanoma that were treated by brachytherapy (cobalt 60 or ruthenium 106 radioactive plaques) were included in this study. Thirteen enucleated eyes of the same size with nonirradiated posterior uveal melanoma served as controls. The tumors were stained with PC-10 monoclonal antibody to proliferating cell nuclear antigen. All clinical and histologic data of the tumors were recorded and analyzed.

RESULTS

Five of the irradiated tumors showed positive staining with PC-10, although with a low score. Four of these tumors showed regrowth, and the fifth tumor was treated with a low-irradiation dose (5500 rad). In the nonirradiated tumor group, nine were positive for PC-10 staining, with a higher score. Significant correlation was found in this group between the PC-10 score and the mitotic figure count, but not with other prognostic factors. In three of four tumors that caused metastatic death, the PC-10 staining was positive and had a high score.

CONCLUSIONS

PC-10 immunostaining is a simple, reproducible method that can be applicable to conventionally processed histologic preparations. It clearly shows that cellular proliferation activity in nonirradiated and irradiated uveal melanomas. Based on the small number of cases reported herein, it seems that the PC-10 score can correlate with prognosis, but further studies should be performed.

Elevated Endogenous SDHA Drives Pathological Metabolism in Highly Metastatic Uveal Melanoma

Purpose

Metastatic uveal melanoma (UM) has a very poor prognosis and no effective therapy. Despite remarkable advances in treatment of cutaneous melanoma, UM remains recalcitrant to chemotherapy, small-molecule kinase inhibitors, and immune-based therapy.

Methods

We assessed two sets of oxidative phosphorylation (OxPhos) genes within 9858 tumors across 31 cancer types. An OxPhos inhibitor was used to characterize differential metabolic programming of highly metastatic monosomy 3 (M3) UM. Seahorse analysis and global metabolomics profiling were done to identify metabolic vulnerabilities. Analyses of UM TCGA data set were performed to determine expressions of key OxPhos effectors in M3 and non-M3 UM. We used targeted knockdown of succinate dehydrogenase A (SDHA) to determine the role of SDHA in M3 UM in conferring resistance to OxPhos inhibition.

Results

We identified UM to have among the highest median OxPhos levels and showed that M3 UM exhibits a distinct metabolic profile. M3 UM shows markedly low succinate levels and has highly increased levels of SDHA, the enzyme that couples the tricarboxylic acid cycle with OxPhos by oxidizing (lowering) succinate. We showed that SDHA-high M3 UM have elevated expression of key OxPhos molecules, exhibit abundant mitochondrial reserve respiratory capacity, and are resistant to OxPhos antagonism, which can be reversed by SDHA knockdown.

Conclusions

Our study has identified a critical metabolic program within poor prognostic M3 UM. In addition to the heightened mitochondrial functional capacity due to elevated SDHA, M3 UM SDHA-high mediate resistance to therapy that is reversible with targeted treatment.

ALCAM regulates motility, invasiveness, and adherens junction formation in uveal melanoma cells

ALCAM, a member of the immunoglobulin superfamily, has been implicated in numerous developmental events and has been repeatedly identified as a marker for cancer metastasis. Previous studies addressing ALCAM's role in cancer have, however, yielded conflicting results. Depending on the tumor cell type, ALCAM expression has been reported to be both positively and negatively correlated with cancer progression and metastasis in the literature. To better understand how ALCAM might regulate cancer cell behavior, we utilized a panel of defined uveal melanoma cell lines with high or low ALCAM levels, and directly tested the effects of manipulating these levels on cell motility, invasiveness, and adhesion using multiple assays. ALCAM expression was stably silenced by shRNA knockdown in a high-ALCAM cell line (MUM-2B); the resulting cells displayed reduced motility in gap-closure assays and a reduction in invasiveness as measured by a transwell migration assay. Immunostaining revealed that the silenced cells were defective in the formation of adherens junctions, at which ALCAM colocalizes with N-cadherin and ß-catenin in native cells. Additionally, we stably overexpressed ALCAM in a low-ALCAM cell line (MUM-2C); intriguingly, these cells did not exhibit any increase in motility or invasiveness, indicating that ALCAM is necessary but not sufficient to promote metastasis-associated cell behaviors. In these ALCAM-overexpressing cells, however, recruitment of ß-catenin and N-cadherin to adherens junctions was enhanced. These data confirm a previously suggested role for ALCAM in the regulation of adherens junctions, and also suggest a mechanism by which ALCAM might differentially enhance or decrease invasiveness, depending on the type of cadherin adhesion complexes present in tissues surrounding the primary tumor, and on the cadherin status of the tumor cells themselves.

Receptors for the liver synthesized growth factors IGF-1 and HGF/SF in uveal melanoma: intercorrelation and prognostic implications

PURPOSE

Uveal melanoma disseminates preferentially to the liver. The mechanism for this homing is largely unknown, but growth factors synthesized in the liver may be involved. The present study was undertaken to investigate the possible relationship between cell surface receptors for two such growth factors: the c-Met proto-oncogene, which constitutes the receptor for hepatocyte growth factor/scatter factor (HGF/SF), and the insulin-like growth factor 1 receptor (IGF-1R). Their role as a prognostic factor was also clarified.

METHODS

Paraffin-embedded tumor specimens from 132 patients with primary uveal melanoma were analyzed by using well-established specific antibodies against c-Met and IGF-1R. The intercorrelation of receptor expression and association with melanoma-related survival of patients were determined by univariate and multivariate analyses.

RESULTS

Whereas the expression of both IGF-1R and c-Met was significantly associated with melanoma-specific mortality by univariate analysis (p = 0.004 and p = 0.007, respectively) only IGF-1R showed independent prognostic value by multivariate analysis, p = 0.004. The prognostic value of IGF-1R was stronger than such currently used prognostic parameters as tumor cell type and tumor diameter (p = 0.021 and p = 0.026, respectively). The expression patterns of the two growth factors receptors were weakly intercorrelated.

CONCLUSIONS

In conclusion, the data suggest that the receptors for IGF-1 and HGF/SF may play a role in the spread of uveal melanoma and its affinity to the liver. The strong correlation between IGF-1R expression and melanoma-specific mortality points to the use of IGF-1R as a prognostic tool [Economou MA, All-Ericsson C, Bykov V, Girnita L, Bartolazzi A, Larsson O & Seregard S (2005): Receptors for the liver synthesized growth factors IGF-1 and HGF/SF in uveal melanoma: intercorrelation and prognostic implications.