Lack of BRAF mutations in uveal melanoma

RAF proteins are serine/threonine kinases that mediate cellular responses to growth signals by activating the mitogen-activated protein kinase pathway. Mutations in the BRAF gene causing a V599E amino acid substitution that enhance the kinase activity have been described in >60% of cutaneous melanomas and premalignant melanocytic lesions. We have investigated the frequency of BRAF mutations at the expression level in melanomas of the uveal tract. None of the 30 metastases and 10 primary uveal melanomas tested expressed the V599E mutation. In contrast, this mutation was expressed by 65% of cutaneous melanoma samples, confirming previous results. In addition, a double mutation resulting in V599K substitution was detected in two suspect ocular metastases of cutaneous melanoma. Analysis of exon 11, the second common site of BRAF mutations, revealed only wild-type sequences in uveal melanomas. Analysis of tumor lysates showed the presence of phosphorylated mitogen-activated protein kinase, kinase, and mitogen-activated protein kinase in 50% of uveal and 100% of cutaneous melanoma metastases. Taken together, these results suggest that although the common BRAF mutations found in cutaneous melanoma do not play a role in tumorigenesis of uveal tract melanocytes, activation of the RAF/mitogen-activated protein kinase pathway may nevertheless play an important role in uveal melanoma.

Localization and characterization of melanoma-associated glycosaminoglycans: differential expression of chondroitin and heparan sulfate epitopes in melanoma

Glycosaminoglycans (GAGs) are anionic polysaccharides present on cells and in the extracellular matrix (ECM). They likely play a role in tumor formation because of their capacity to bind and modulate a variety of proteins including growth factors, cytokines, and proteases. Using a panel of (human) phage display-derived anti-GAG antibodies, the location and expression of GAG epitopes in human cutaneous melanocytic lesions was studied. Antibodies EW4E1 and EW4G2 identified a melanoma-associated chondroitin sulfate/heparan sulfate epitope, whereas antibody EW4B7 recognized a melanoma-associated heparan sulfate epitope. These antibodies showed a high reactivity with blood vessels and ECM in cutaneous melanoma tumors, whereas their reactivity with nevi was very low. Using a set of defined oligosaccharides it was established that sulfate groups are of main importance in the binding to the antibodies and that glycomimetics can mimic natural oligosaccharides. In xenografts of melanoma cell line MeL57, a strong association of GAG epitopes with an injected fluorescent fluid flow tracer was observed. In uveal melanoma antibody, EW4E1 proved to be a sensitive probe for the detection of the geometry of ECM structures, known to have prognostic value. Taken together, data indicate that in melanoma a defined set and location of GAG epitopes are present with possible functional significance.

[Tumor angiogensis in uveal melanoma. Role of vascular endothelial growth factor (VEGF)]

Neoplastic angiogenesis, as a process of forming new blood vessels, plays an important role in progression of cancer tumors and dissemination of metastases. New vessels can be formed in cancer tissue due to mutations of certain genes and under the influence of hypoxia. The process is mediated by locally delivered specific angiogenetic factors. Vascular endothelial growth factor (VEGF) plays a crucial role in stimulation of the vascular endothelial cells to their proliferation and migration. Intensity of neoplastic angiogenesis determines the rate and extent of tumor expansion, thus may heavily influence the outcome.

Changes in MR of malignant melanomas induced by glucose and fructose. A clinical and experimental investigation

MR imaging has been performed on malignant melanomas in vitro and in vivo. Changes of the water content in an enucleated malignant melanoma in vitro were followed by significant changes of the T1 and T2 values. In mice with implanted subcutaneous melanoma similar changes could be obtained after injection of glucose and fructose intraperitoneally. Malignant melanoma of the eye could be influenced in the same way in 10 consecutive patients after oral intake of glucose and fructose. The present study shows that the MR images may be significantly changed after a few hours by altered metabolism induced by glucose and fructose. It is anticipated that this is due to changes within the tumor leading to different water distribution. The finding may be of importance as a further help for diagnosing malignant melanoma of the eye.

Integrin expression in uveal melanoma differs from cutaneous melanoma

PURPOSE

During the process of metastasis, changes in cell-cell and cell-matrix contacts occur; therefore, expression of integrins, a superfamily of adhesion molecules, may be important. Expression of integrins has been studied extensively in cutaneous melanoma. Because it is known that uveal melanoma has a metastatic behavior different from cutaneous melanoma, the authors investigated integrin expression in uveal melanoma.

METHODS

The authors used monoclonal antibodies recognizing integrin subunits alpha 1-6, alpha v, beta 1, and beta 4 and integrins alpha v beta 3 and alpha v beta 5 on frozen sections of 32 human primary uveal melanomas and 4 metastases, followed by an avidin-biotin-peroxidase complex-immunoperoxidase technique.

RESULTS

As in cutaneous melanoma, alpha 4 expression was rare, but most lesions expressed alpha 3 and alpha 6. In contrast to cutaneous melanoma, in which alpha 2 is well expressed in most lesions and alpha 5 is expressed only in a small percentage of lesions, alpha 2 expression was rare in uveal melanoma and alpha 5 expression was found in all lesions. A major difference was observed with regard to the alpha v beta 3 vitronectin receptor. In contrast to cutaneous melanoma, in which alpha v beta 3 is expressed in advanced primary melanomas and metastases, alpha v beta 3 was not detected in any of the primary uveal melanomas, but all lesions strongly expressed alpha v beta 5.

CONCLUSIONS

Integrin expression in uveal melanoma cannot be correlated with cell type or invasiveness. In contrast to cutaneous melanoma, it seems that determination of the integrin expression profile is not suitable for categorizing uveal melanomas as less malignant and highly malignant lesions.

Comparative Single Vesicle Analysis of Aqueous Humor Extracellular Vesicles before and after Radiation in Uveal Melanoma Eyes

Small extracellular vesicles (sEVs) have been shown to promote tumorigenesis, treatment resistance, and metastasis in multiple cancer types; however, sEVs in the aqueous humor (AH) of uveal melanoma (UM) patients have never previously been profiled. In this study, we used single particle analysis to characterize sEV subpopulations in the AH of UM patients by quantifying their size, concentration, and phenotypes based on cell surface markers, specifically the tetraspanin co-expression patterns of CD9, CD63, and CD81. sEVs were analyzed from paired pre- and post-treatment (brachytherapy, a form of radiation) AH samples collected from 19 UM patients. In post-brachytherapy samples, two subpopulations, CD63/81+ and CD9/63/81+ sEVs, were significantly increased. These trends existed even when stratified by tumor location and GEP class 1 and class 2 (albeit not significant for GEP class 2). In this initial report of single vesicle profiling of sEVs in the AH of UM patients, we demonstrated that sEVs can be detected in the AH. We further identified two subpopulations that were increased post-brachytherapy, which may suggest radiation-induced release of these particles, potentially from tumor cells. Further study of the cargo carried by these sEV subpopulations may uncover important biomarkers and insights into tumorigenesis for UM.

Activation of NFAT by HGF and IGF-1 via ARF6 and its effector ASAP1 promotes uveal melanoma metastasis

Preventing or effectively treating metastatic uveal melanoma (UM) is critical because it occurs in about half of patients and confers a very poor prognosis. There is emerging evidence that hepatocyte growth factor (HGF) and insulin-like growth factor 1 (IGF-1) promote metastasis and contribute to the striking metastatic hepatotropism observed in UM metastasis. However, the molecular mechanisms by which HGF and IGF-1 promote UM liver metastasis have not been elucidated. ASAP1, which acts as an effector for the small GTPase ARF6, is highly expressed in the subset of uveal melanomas most likely to metastasize. Here, we found that HGF and IGF-1 hyperactivate ARF6, leading to its interaction with ASAP1, which then acts as an effector to induce nuclear localization and transcriptional activity of NFAT1. Inhibition of any component of this pathway impairs cellular invasiveness. Additionally, knocking down ASAP1 or inhibiting NFAT signaling reduces metastasis in a xenograft mouse model of UM. The discovery of this signaling pathway represents not only an advancement in our understanding of the biology of uveal melanoma metastasis but also identifies a novel pathway that could be targeted to treat or prevent metastatic uveal melanoma.

Multicentre analysis of nucleic acid quantification using aqueous humour liquid biopsy in uveal melanoma: implications for clinical testing

OBJECTIVE

Uveal melanoma (UM) tumour biopsy is limited by size and intratumour heterogeneity. We explored the potential of aqueous humour (AH) liquid biopsy for UM by quantifying analytes in samples collected at diagnosis and after brachytherapy to look for clinical correlations with tumour features.

DESIGN

Case-series study.

PARTICIPANTS

Sixty-six UM patients and 16 control subjects from a tertiary care hospital.

METHODS

The study included 119 UM AH samples and 16 control samples analyzed for unprocessed analytes (i.e., dsDNA, miRNA, and protein) using Qubit fluorescence assays.

RESULTS

Analytes were widely quantifiable among available UM AH samples (dsDNA: 94.1%; miRNA: 88.0%; protein: 95.2%) at significantly higher concentrations than among control samples (dsDNA, p = 0.008; miRNA, p < 0.0001; protein, p = 0.007). In samples taken at diagnosis, concentrations were higher at more advanced American Joint Cancer Commission stages; when comparing most advanced stage III with least advanced stage I, median dsDNA was 4 times greater (p < 0.0001), miRNA was 2 times greater (p = 0.001), and protein was 3 times greater (p < 0.0001). Analytes were quantifiable in >70% of diagnostic samples from eyes with tumours <2 mm tall. Height had a positive association with diagnostic analyte concentrations (dsDNA: R = 0.43, p = 0.0007; miRNA: R = 0.35, p = 0.01; protein: R = 0.39, p = 0.005). Samples taken after brachytherapy showed significantly higher concentrations than diagnostic samples (p < 0.01 for all).

CONCLUSIONS

UM AH is a rich repository of analytes. Samples from eyes with more advanced stage and larger tumours had higher concentrations, though analytes also were quantifiable in eyes with smaller, less advanced tumours. Future analysis of AH analytes may be informative in the pursuit of personalized UM treatments.

Neuropeptide Precursor VGF Promotes Liver Metastatic Colonization of Gαq Mutant Uveal Melanoma by Facilitating Tumor Microenvironment via Paracrine Loops

Uveal melanoma (UM), the predominant primary ocular malignancy, often progresses to liver metastasis with limited therapeutic options. The interplay of the tumor microenvironment, encompassing secreted soluble factors, plays a crucial role in facilitating liver metastasis. In this study, the role is elucidated of the neural growth factor-inducible gene (VGF), a secreted neuropeptide precursor, in Gαq mutant UM. Employing a multiomics approach, encompassing transcriptomic and secretomic analyses, the intricate involvement of VGF in UM progression is unveiled. VGF is upregulated in Gαq mutant UM cells and associated with poor prognosis of UM patients. Targeting VGF significantly suppressed the growth of UM in vitro and in vivo. Further evidence shows that VGF is regulated by Gαq through MAPK/CREB pathway. Mechanistically, CREB modulates VGF expression by directly binding to consensus DNA response elements in the promoters of the VGF gene. Combined inhibition of Gαq and MEK remarkably reduces tumor burden in the UM xenograft model. Notably, VGF triggers liver metastatic colonization of UM and activates the fibrosis of hepatic stellate cells (HSCs), creating a favorable microenvironment, through an autocrine and paracrine loop. Furthermore, VGF directly binds to TGFBR2 and regulates TGF-β-SMAD signaling pathway, thereby regulating genes associated with endothelial-mesenchymal transition (EMT) to promote metastasis. Taken together, these findings identify VGF as a pivotal driver in the progression and metastasis of Gαq mutant UM and confers a promising therapeutic target and strategy for UM patients.

RBMS1 reflects a distinct microenvironment and promotes tumor progression in ocular melanoma

Ocular melanoma, including uveal melanoma (UM) and conjunctival melanoma (CM), is the most common ocular cancer among adults with a high rate of recurrence and poor prognosis. Loss of epigenetic homeostasis disturbed gene expression patterns, resulting in oncogenesis. Herein, we comprehensively analyzed the DNA methylation, transcriptome profiles, and corresponding clinical information of UM patients through multiple machine-learning algorithms, finding that a methylation-driven gene RBMS1 was correlated with poor clinical outcomes of UM patients. RNA-seq and single-cell RNA-seq analyses revealed that RBMS1 reflected diverse tumor microenvironments, where high RBMS1 expression marked an immune active TME. Furthermore, we found that tumor cells were identified to have the higher communication probability in RBMS1+ state. The functional enrichment analysis revealed that RBMS1 was associated with pigment granule and melanosome, participating in cell proliferation as well as apoptotic signaling pathway. Biological experiments were performed and demonstrated that the silencing of RBMS1 inhibited ocular melanoma proliferation and promoted apoptosis. Our study highlighted that RBMS1 reflects a distinct microenvironment and promotes tumor progression in ocular melanoma, contributing to the therapeutic customization and clinical decision-making.

Melatonin Receptor Expression in Primary Uveal Melanoma

Melatonin, noted for its anti-cancer properties in various malignancies, including cutaneous melanoma, shows promise in Uveal melanoma (UM) treatment. This study aimed to evaluate melatonin receptor expression in primary UM and its association with UM-related mortality and prognostic factors. Immunohistochemical analysis of 47 primary UM tissues showed low expression of melatonin receptor 1A (MTNR1A) and melatonin receptor 1B (MTNR1B), with MTNR1A significantly higher in patients who succumbed to UM. Analysis of TCGA data from 80 UM patients revealed RNA expression for MTNR1A, retinoic acid-related orphan receptor alpha (RORα), and N-ribosyldihydronicotinamide:quinone oxidoreductase (NQO2), but not MTNR1B or G protein-coupled receptor 50 (GPR50). Higher MTNR1A RNA levels were observed in patients with a BRCA1 Associated Protein 1 (BAP1) mutation, and higher NQO2 RNA levels were noted in patients with the epithelioid tumor cell type. However, Kaplan-Meier analysis did not show distinct survival probabilities based on receptor expression. This study concludes that UM clinical samples express melatonin receptors, suggesting a potential mechanism for melatonin's anti-cancer effects. Despite finding higher MTNR1A expression in patients who died of UM, no survival differences were observed.

Role of epidermal growth factor receptor in the metastasis of intraocular melanomas

PURPOSE

To explore the expression and function of epidermal growth factor receptor (EGFR) expression on human uveal melanoma cells.

METHODS

Five human uveal melanoma cell lines were examined by flow cytometry for the expression of EGFR. The correlation between EGFR expression and metastasis of uveal melanoma cells was tested in a nude mouse model of intraocular melanoma. The effect of EGFR on liver homing of blood-borne uveal melanoma cells was tested by tracing the fate of radiolabeled cells treated with anti-EGFR monoclonal antibody. The capacity of EGFR to inhibit the cytotoxic effects of tumor necrosis factor-alpha (TNF-alpha) was determined in vitro. The role of EGFR in promoting metastatic disease was studied by infusing intraocular melanoma-bearing mice using a neutralizing antibody against EGFR.

RESULTS

EGFR was expressed to varying degrees on all eight human uveal melanoma cell lines. Expression of EGFR correlated with metastatic potential and capacity of blood-borne uveal melanoma cells to localize in the liver. EGFR rendered uveal melanoma cells resistant to the cytolytic effects of TNF-alpha. Blocking EGFR with a neutralizing monoclonal antibody increased the susceptibility of uveal melanoma cells to TNF-mediated cytolysis, inhibited metastases, and prolonged host survival.

CONCLUSIONS

The expression of EGFR on five human uveal melanoma cell lines is correlated with an increased capacity to localize in the liver, an increased resistance to TNF-mediated lysis, and decreased survival. Targeting EGFR expression and function may be a fruitful strategy for managing patients with uveal melanoma.

SPARC is expressed in human uveal melanoma and its abrogation reduces tumor cell proliferation

BACKGROUND

Secreted protein acidic and rich in cysteine (SPARC) has been shown to play an integral role in the progression of numerous malignancies. The aim of this study was to investigate the expression of SPARC in uveal melanoma (UM).

MATERIALS AND METHODS

SPARC expression was assessed in UM cell lines using RT-PCR and immunocytochemistry. Small interfering RNA directed against SPARC was used to transfect each of the cell lines, which were subsequently run in proliferation assays. SPARC expression was further investigated in 19 cases of human UM and 11 primary and 8 metastatic tumors from a rabbit xenograft model.

RESULTS

The cell lines transfected with SPARC siRNA showed a significant decrease in proliferation compared to controls. All cases of human uveal melanoma demonstrated positive staining for SPARC as did all primary and metastatic tumors from the xenograft model.

CONCLUSION

SPARC may represent a novel target to inhibit growth of UM.

Cooperative interactions of laminin 5 gamma2 chain, matrix metalloproteinase-2, and membrane type-1-matrix/metalloproteinase are required for mimicry of embryonic vasculogenesis by aggressive melanoma

Vasculogenic mimicry describes a process where aggressive tumor cells in three-dimensional matrices mimic embryonic vasculogenesis by forming extracellular matrix (ECM)-rich, patterned tubular networks. Microarray gene chip analyses revealed significant increases in the expression of laminin 5 (Ln-5, gamma2 chain) and matrix metalloproteinases (MMP)-1, -2, -9, and MT1-MMP (MMP-14) in aggressive compared with poorly aggressive melanoma cells. These components colocalized with developing patterned networks and antisense oligonucleotides to the Ln-5 gamma2 chain (but not sense oligonucleotides), and antibodies to MMP-2 or MT1-MMP (but not MMP-9) inhibited the formation of these networks. Cultures which did not receive antibodies to either MMPs-2 or -14 contained the Ln-5 gamma2 chain promigratory cleavage fragments. Poorly aggressive melanoma cells seeded on collagen I matrices preconditioned by the aggressive cells formed tubular networks along the Ln-5 gamma2 chain-enriched tracks deposited by the aggressive cells. These results suggest that increased expression of MMP-2 and MT1-MMP, along with matrix deposition of the Ln-5 gamma2 chain and/or its cleavage fragments, are required for vasculogenic mimicry by aggressive melanoma cells. Furthermore, the apparent recapitulation of laminin-rich, patterned networks observed in aggressive melanoma patients' tissue sections by aggressive melanoma tumor cells in three-dimensional culture may also serve as a model to help identify specific molecular targets which could function as templates for the coordinated migration of aggressive tumor cells and their proteolytic remodeling of the ECM and may have profound implications for the development of novel therapies directed at the ECM to alter tumor progression.

Construction of oxidative phosphorylation-related prognostic risk score model in uveal melanoma

BACKGROUND

Uveal melanoma (UVM) is a malignant intraocular tumor in adults. Targeting genes related to oxidative phosphorylation (OXPHOS) may play a role in anti-tumor therapy. However, the clinical significance of oxidative phosphorylation in UVM is unclear.

METHOD

The 134 OXPHOS-related genes were obtained from the KEGG pathway, the TCGA UVM dataset contained 80 samples, served as the training set, while GSE22138 and GSE39717 was used as the validation set. LASSO regression was carried out to identify OXPHOS-related prognostic genes. The coefficients obtained from Cox multivariate regression analysis were used to calculate a risk score, which facilitated the construction of a prognostic model. Kaplan-Meier survival analysis, logrank test and ROC curve using the time "timeROC" package were conducted. The immune cell frequency in low- and high-risk group was analyzed through Cibersort tool. The specific genomic alterations were analyzed by "maftools" R package. The differential expressed genes between low- or high-risk group were analyzed and performed Gene Ontology (GO) and GSEA. Finally, we verified the function of CYC1 in UVM by gene silencing in vitro.

RESULTS

A total of 9 OXPHOS-related prognostic genes were identified, including NDUFB1, NDUFB8, ATP12A, NDUFA3, CYC1, COX6B1, ATP6V1G2, ATP4B and NDUFB4. The UVM prognostic risk model was constructed based on the 9 OXPHOS-related prognostic genes. The prognosis of patients in the high-risk group was poorer than low-risk group. Besides, the ROC curve demonstrated that the area under the curve of the model for predicting the 1 to 5-year survival rate of UVM patients were all more than 0.88. External validation in GSE22138 and GSE39717 dataset revealed that these 9 genes could also be utilized to evaluate and predict the overall survival of patients with UVM. The risk score levels related to immune cell frequency and specific genomic alterations. The DEGs between the low- and high- risk group were enriched in tumor OXPHOS and immune related pathway. In vitro experiments, CYC1 silencing significantly inhibited UVM cell proliferation and invasion, induced cell apoptosis.

CONCLUSION

In sum, a prognostic risk score model based on oxidative phosphorylation-related genes in UVM was developed to enhance understanding of the disease. This prognostic risk score model may help to find potential therapeutic targets for UVM patients. CYC1 acts as an oncogene role in UVM.

Death associated protein like 1 acts as a novel tumor suppressor in melanoma by increasing the stability of P21 protein

Melanoma is a primary malignant tumor with high lethality, which occurs in the skin and eye tissues, while the molecular mechanisms of melanomagenesis remain largely unknown. Here, we show that death-associated protein-like 1 (DAPL1) expression is lower in melanoma tissues than in paracancerous tissues or nevus tissues, and Uveal melanoma patients with lower DAPL1 expression have a poorer survival rate than those with higher expression of DAPL1. Overexpression of DAPL1 inhibits proliferation of cultured melanoma cells, whereas knockdown of DAPL1 increases cell proliferation. Tumor transplantation experiment results also demonstrate that DAPL1 inhibits tumorigenesis of melanoma cells both in subretinal and subcutaneous tissues of nude mice in vivo. Finally, DAPL1 inhibits proliferation of melanoma cells by increasing the protein level of P21 via decreasing the ubiquitin mediated degradation of P21 and promoting its stability. Conversely, knockdown of P21 neutralizes the effects of inhibition of DAPL1 on melanoma cell proliferation and enhances the severity of melanoma tumorigenesis. These results suggest that DAPL1 is a novel melanoma tumor suppressor gene and thus a potential therapeutic target for melanoma.

S100 immunophenotypes of uveal melanomas

To determine whether ocular melanomas are immunophenotypically identical to cutaneous melanomas, 34 primary and metastatic choroidal melanomas representing all major histotypes defined by the Callender's classification, plus one melanoma of the iris and one conjunctival melanoma, were subjected to a panel of immunostains designed to distinguish anaplastic biopsies of cutaneous melanomas from carcinomas and lymphomas. All ocular melanomas were found to express the intermediate filament vimentin but not keratin, and all but 2 were melanotic by immunostaining. Thirty-three of 34 (97%) choroidal melanomas were strongly stained with a rabbit polyclonal antibody (P-S100) developed against the S100 protein family. In contrast, none of 14 spindle cell type primary lesions was stained with a monoclonal antibody (MAB-079) specific for both S100 alpha and S100 beta, the best-characterized S100 polypeptides. Furthermore, only 2 of 5 epithelioid and 3 of 10 mixed-cell-type melanomas were weakly reactive. Overall, 14.7% (5 of 29) were stained. In comparison, MAB079 stained 85% of all cutaneous melanomas. Five metastases of choroidal melanomas (spindle B, epithelioid, and mixed cell types) from different organ sites also were stained by P-S100 but not by MAB079. These findings were corroborated by immunostaining with another monoclonal antibody (MAB4D4) specific for S100 beta. Differential staining by the polyclonal but not the monoclonal antibodies suggests the possible presence of a variant S100 polypeptide(s) in choroidal melanomas. Since S100 alpha, S100 beta, and related proteins appear to be physiologically important, additional studies of these S100 proteins may shed light on the etiology or pathology of choroidal melanomas.

Association of HLA class I and class II antigen expression and mortality in uveal melanoma

PURPOSE

Malignant transformation of cells is frequently associated with abnormalities in human leukocyte antigen (HLA) expression. These abnormalities may play a role in the clinical course of the disease, because HLA antigens mediate interactions of tumor cells with T cells and NK cells. Uveal melanoma is a highly malignant tumor of the eye and is characterized by a hematogenic spread to the liver. Little is known about the role of HLA expression in progression of this malignant disease.

METHODS

In the present study HLA class I antigen, beta(2)-microglobulin (beta(2)-m), and HLA class II antigen expression was analyzed in primary uveal melanoma lesions by immunoperoxidase staining with monoclonal antibodies of 65 archival clinical samples. The results were correlated with the clinical course of the disease.

RESULTS

HLA class I antigen expression and beta(2)-m expression were downregulated in 40 and 35 lesions, respectively. HLA class II antigens were expressed in 30 lesions. Patients with high HLA class I, including beta(2)-m, and HLA class II antigen expression in their primary melanoma lesions had a significantly decreased survival (P = 0.009, P < 0.001, and P = 0.006, respectively).

CONCLUSIONS

The findings argue against a major role of cytotoxic T-lymphocyte (CTL)-mediated control of tumor growth in the clinical course of uveal melanoma and are compatible with a potential role of NK-cell-mediated control of hematogenic metastatic spread.

Transgenic mice with pigmented intraocular tumors: tissue of origin and treatment

PURPOSE

To describe the cell of origin, tumor progression, light and electron microscopic appearance, immunohistochemical properties, and response to frequently used anticancer therapies in two transgenic models of intraocular melanoma.

METHODS

Two lines of transgenic mice that develop pigmented intraocular tumors were produced with the SV40 T and t antigens under the control of the mouse tyrosinase gene. Tumors were sequentially studied and characterized by light microscopy, electron microscopy, and immunohistochemistry stains. Tumor response to two cycles of dacarbazine was assessed on the basis of tumor size in one group of animals. Response to external beam irradiation was measured by survival time in other animals.

RESULTS

Two lines of transgenic mice developed bilateral intraocular tumors with complete penetrance and without primary cutaneous melanomas. Tumors developed first in the retinal pigment epithelial layer, with subsequent retinal and choroidal invasion, extraocular extension, and metastasis. Tumors stained positive for S-100, HMB-45, and Fas-ligand. Electron microscopy revealed polarization of tumor cells with basement membrane formation, microvilli, immature melanosomes, and abundant endoplasmic reticulum. Dacarbazine significantly reduced tumor size in these mice, and a trend toward dose-dependent decrease in survival was found with external beam irradiation.

CONCLUSIONS

Tumors developed from the retinal pigment epithelium. Their histology and growth, however, closely resembled that of human choroidal melanoma. This model may be a useful tool for future studies of endogenous primary pigmented tumors limited to the eye. Response to standard therapies suggests it can serve as a model with which to evaluate therapeutic modalities.

MicroRNA-137 targets EZH2 to exert suppressive functions in uveal melanoma via regulation of Wnt/β-catenin signaling and epithelial-to-mesenchymal transition

PURPOSE

Uveal melanoma (UM) is one of the primary intraocular malignancies. Emerging studies have confirmed dysregulation of microRNA (miRNA/miR) in UM. The present study focused on the biofunctions of miR-137 in UM.

METHODS

MiR-137 expressions in tissue samples were analyzed by qRT-PCR. MTT and transwell assays were applied to investigate the impacts of miR-137 on UM cell proliferation, invasion and migration. Luciferase assay was carried out to explore the downstream target of miR-137. Western blot was used to analyze the roles of miR-137 in UM cells, Wnt/β-catenin pathway and epithelial-mesenchymal transition (EMT).

RESULTS

qRT-PCR showed that miR-137 expressions were lower in UM tissue samples than para-carcinoma tissues, whereas EZH2 was simultaneously upregulated. MiR-137 overexpression evidently suppressed UM cell proliferation, invasion and migration. The findings also indicated that miR-137 restoration could block Wnt/β-catenin pathway and EMT in UM cells thus resulting in downregulation of malignant behaviors. EZH2 was a downstream target of miR-137 as demonstrated by luciferase assay.

CONCLUSION

The present study indicated that EZH2 participated in the anti-UM functions of miR-137. Taken together, the data in our study established miR-137/EZH2 axis in regulating UM progression, suggesting that miR-137 may function as a novel therapeutic biomarker for UM patients.

Evaluation of a Brown Seaweed Extract from Dictyosiphon foeniculaceus as a Potential Therapeutic Agent for the Treatment of Glioblastoma and Uveal Melanoma

Ingredients of brown seaweed like fucoidans are often described for their beneficial biological effects, that might be interesting for a medical application. In this study, we tested an extract from Dictyosiphon foeniculaceus (DF) to evaluate the effects in glioblastoma and uveal melanoma, looking for a possible anti-cancer treatment. We investigated toxicity, VEGF (vascular endothelial growth factor) secretion and gene expression of tumor and non-tumor cells. SVGA (human fetal astrocytes), the human RPE (retinal pigment epithelium) cell line ARPE-19, the tumor cell line OMM-1 (human uveal melanoma), and two different human primary glioblastoma cultures (116-14 and 118-14) were used. Tests for cell viability were conducted with MTS-Assay (3-(4,5-Dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium), and the proliferation rate was determined with cell counting. VEGF secretion was assessed with ELISA (enzyme-linked immunosorbent assay). The gene expression of VEGF receptor 1 (VEGFR1), VEGF receptor 2 (VEGFR2) and VEGF-A was determined with real-time qPCR (quantitative polymerase chain reaction). DF lowered the cell viability of OMM-1. Proliferation rates of ARPE-19 and OMM-1 were decreased. The VEGF secretion was inhibited in ARPE-19 and OMM-1, whereas it was increased in SVGA and 116-14. The expression of VEGFR1 was absent and not influenced in OMM-1 and ARPE-19. VEGFR2 expression was lowered in 116-14 after 24 h, whereas VEGF-A was increased in 118-14 after 72 h. The extract lowered cell viability slightly and was anti-proliferative depending on the cell type investigated. VEGF was heterogeneously affected. The results in glioblastoma were not promising, but the anti-tumor properties in OMM-1 could make them interesting for further research concerning cancer diseases in the human eye.

TREM2, a critical activator of pyroptosis, mediates the anti‑tumor effects of piceatannol in uveal melanoma cells via caspase 3/GSDME pathway

Uveal melanoma (UM) is the most prevalent type of primary intraocular malignancy and is prone to metastasize, particularly to the liver. However, due to the poor understanding of the pathogenesis of UM, effective therapeutic approaches are lacking. As a phenolic compound extracted from grapes, piceatannol (PIC) exhibits anti‑cancer properties. To the best of our knowledge, however, the effects of PIC on UM have not been well investigated. Therefore, in the present study, considering the impact of pyroptosis on modulating cell viability, the mechanism underlying the effects of PIC on UM cell proliferation was explored. The inhibitory effect of PIC on proliferation of UM cells was detected by cell counting kit‑8 assay. Wound healing was used to investigate the effects of PIC on the migration of UM cells. Activity detecting assays were performed to test the apoptosis and oxidant level in UM cells. Western blotting and RT‑qPCR were used to detect the inflammatory and pyroptotic levels of UM cell after PIC treatment. PIC‑treated UM cells were screened by high‑throughput sequencing to detect the differential expression of RNA and differential genes. Si‑TREM2 transfection was used to verify the important role of TREM2 in the effects of PIC. Immunohistochemical staining was used to observe the expressions of TREM2 and GSDMR of tumor in nude mice after PIC administration. PIC effectively inhibited proliferation ability of C918 and Mum‑2b UM cell lines via enhancing apoptosis, as evidenced by enhanced activities of caspase 3 and caspase 9. In addition, treatment of UM cells with PIC attenuated cell migration in a dose‑dependent manner. PIC increased reactive oxygen species levels and suppressed the activity of the antioxidant enzymes superoxide dismutase, glutathione‑S‑transferase, glutathione peroxidase and catalase. PIC inhibited inflammatory responses in C918 cells. PIC treatment upregulated IL‑1β, IL‑18 and Nod‑like receptor protein 3 and downregulated gasdermin D (GSDMD). RNA sequencing results revealed the activation of an unconventional pyroptosis‑associated signaling pathway, namely caspase 3/GSDME signaling, following PIC treatment, which was mediated by triggering receptor expressed on myeloid cells 2 (TREM2) upregulation. As an agonist of TREM2, COG1410‑mediated TREM2 upregulation inhibited proliferation of C918 cells, displaying similar effects to PIC. Furthermore, PIC inhibited tumor growth via regulating the TREM2/caspase 3/GSDME pathway in a mouse model. Collectively, the present study revealed a novel mechanism underlying the inhibitory effects of PIC on UM, providing a potential treatment approach for UM in clinic.

Antioxidant pattern in uveal melanocytes and melanoma cell cultures

PURPOSE

To investigate the antioxidant status of cultured uveal melanocytes from patients with uveal melanoma and uveal melanoma cells to characterize some of the biochemical properties of these cells in respect to the normal cutaneous melanocytes.

METHODS

The fatty acid pattern of membrane phospholipids, intracellular vitamin E level, and superoxide dismutase (SOD) and catalase activities were studied in uveal melanocytes (n = 10) and uveal melanoma cell (n = 10) cultures, by gas chromatography mass spectrometry or by spectrophotometer.

RESULTS

Among the uveal melanocyte cultures, two groups were differentiated, according to catalase activity: group A with catalase values comparable to those of cutaneous ones and higher SOD activity and group B with catalase values 2 SD lower (P<0.001) and lower SOD activity. Vitamin E concentration was not significantly different between melanoma cells and melanocytes, whereas a significantly higher percentage of polyunsaturated fatty acids was found in melanoma cells and the B group of melanocytes (P = 0.022). In uveal melanoma cells SOD activity was significantly lower than that detected in uveal melanocytes (P< 0.005).

CONCLUSIONS

These results show a different pattern of antioxidants in uveal melanocytes with respect to cutaneous ones, possibly related to the anatomic distribution. However, as in cutaneous melanocytes, two subgroups were identified on the basis of the antioxidant pattern that could be the expression of a constitutional increased susceptibility to oxidative stress in some subjects. Moreover, an imbalance of the antioxidants was observed in melanoma cells, possibly related to the disease status and progression.

[Expression of CD44 molecule and its significance in uveal and conjunctival melanomas]

The aim of this study was to evaluate the role of over expression of CD44 molecule in the development and progression of uveal and conjunctival melanomas. Flow cytometry (FCM) and immunofluorescence methods were used for detecting the CD44V expression in uveal malignant melanomas (UMM), conjunctival nevi (CN) and conjunctival malignant melanomas(CMM). The expression content of CD44 in 7 cases of CMM was significantly higher than that in 5 cases of CN (P < 0.05); the CD44V positive expression percentages in 7 cases of CMM and 40 cases of UMM were 71.43% and 62.50% respectively; the expression content of CD44V in UMM was related to scleral invasion (P = 0.0105); there was a negative correlation between the expression content of CD44V and proliferative index (PI), S-phase fraction (SPF) (P < 0.01; P < 0.05). The results suggested that the over expression of CD44V might be involved in the development of CMM and UMM and related to local infiltration ability of UMM and that the CD44V expression content detected by FCM might be helpful in discriminating CN From CMM, but this waited for further research confirmation.

Microvascular density in predicting survival of patients with choroidal and ciliary body melanoma

PURPOSE

Although malignant uveal melanoma disseminates predominantly hematogenously because of the absence of intraocular lymphatics, consensus about prognostic impact of microvascular density (MVD) has not been reached. This study was undertaken to investigate whether MVD, microvascular patterns, or both determine prognosis of uveal melanoma.

METHODS

A population-based retrospective cohort study of melanoma-specific and all-cause mortality of 167 consecutive patients who had an eye enucleated because of choroidal or ciliary body melanoma from 1972 through 1981 was conducted. MVD was determined by counting tumor vessels in a masked fashion from areas of highest vessel density after immunostaining for CD34 epitope, factor VIII-related antigen (FVIII-RAg), and alpha-smooth muscle actin (SMA). Kaplan-Meier and Cox regression analyses of survival were performed. The association between MVD and tumor size and location, cell type, and microvascular patterns was assessed.

RESULTS

MVD could be determined from 134 of 167 melanomas (80%). Based on globally highest count obtained with antibodies to CD34, MVD ranged from 5 to 121 vessels/0.313 mm2 (median, 40) and its association with presence of microvascular loops and networks (P = 0.0006), epithelioid cells (P = 0.028), and largest basal tumor diameter (P = 0.0029) was statistically significant. The 10-year melanoma-specific mortality increased with MVD (0.09, 0.29, 0.59, and 0.64, according to quartiles; P < 0.0001), as did all-cause mortality (P = 0.0022). Equivalent results were obtained with immunostaining for FVIII-RAg, whereas MVD obtained with antibodies to SMA was not associated with prognosis. Cox regression showed a hazard ratio of 2.45 (95% CI, 1.43-4.18) for presence of epithelioid cells, 1.11 (95% CI, 1.03-1.20) for largest basal diameter, 1.23 (95% CI, 1.06-1.43) for square root-transformed MVD, and 1.51 (95% CI, 1.09-2.10) for presence of loops and networks, all of which independently contributed to prognosis.

CONCLUSIONS

The findings support the theory that both MVD and microvascular patterns contribute independently to prognosis in uveal melanoma in addition to cell type and size of the tumor.