Diversified β-2-adrenergic Receptor Expression and Action in Melanoma Cells

BACKGROUND/AIM

Growing evidence links stress hormones with development and progression of various cancer types. The aim of this study was to assess susceptibility of cutaneous and uveal melanoma cells to adrenaline (AD).

MATERIALS AND METHODS

The expression of β-2-adrenergic receptor in primary cutaneous (FM-55-P), primary uveal (92-1, Mel202) and metastatic cutaneous (A375) melanoma cells was estimated at mRNA, protein and cell surface levels. The impact of AD on cell proliferation and migration was also studied.

RESULTS

The expression of β-2-adrenergic receptor was cell line-dependent. Adrenaline treatment caused a slight stimulation of melanoma cell proliferation and activation of matrix metalloproteinases. Adrenaline-treated uveal melanoma cells showed an increased migration rate, whereas, in cutaneous melanoma cells, no changes or even lower migration speed were observed.

CONCLUSION

Melanoma cell susceptibility to AD varies depending on origin and progression stage. Metastatic cutaneous melanoma cells were found to be less responsive to AD than primary cutaneous and uveal melanoma cells.

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.

Co-targeting HGF/cMET Signaling with MEK Inhibitors in Metastatic Uveal Melanoma

Patients with metastatic uveal melanoma usually die within 1 year of diagnosis, emphasizing an urgent need to develop new treatment strategies. The liver is the most common site of metastasis. Mitogen-activated protein kinase kinase (MEK) inhibitors improve survival in V600 BRAF-mutated cutaneous melanoma patients but have limited efficacy in patients with uveal melanoma. Our previous work showed that hepatocyte growth factor (HGF) signaling elicits resistance to MEK inhibitors in metastatic uveal melanoma. In this study, we demonstrate that expression of two BH3-only family proteins, Bim-EL and Bmf, contributes to HGF-mediated resistance to MEK inhibitors. Targeting HGF/cMET signaling with LY2875358, a neutralizing and internalizing anti-cMET bivalent antibody, and LY2801653, a dual cMET/RON inhibitor, overcomes resistance to trametinib provided by exogenous HGF and by conditioned medium from primary hepatic stellate cells. We further determined that activation of PI3Kα/γ/δ isoforms mediates the resistance to MEK inhibitors by HGF. Combination of LY2801653 with trametinib decreases AKT phosphorylation and promotes proapoptotic PARP cleavage in metastatic uveal melanoma explants. Together, our data support the notion that selectively blocking cMET signaling or PI3K isoforms in metastatic uveal melanoma may break the intrinsic resistance to MEK inhibitors provided by factors from stromal cells in the liver. Mol Cancer Ther; 16(3); 516-28. ©2017 AACR.

The biology of uveal melanoma

Uveal melanoma (UM), a rare cancer of the eye, is distinct from cutaneous melanoma by its etiology, the mutation frequency and profile, and its clinical behavior including resistance to targeted therapy and immune checkpoint blockers. Primary disease is efficiently controlled by surgery or radiation therapy, but about half of UMs develop distant metastasis mostly to the liver. Survival of patients with metastasis is below 1 year and has not improved in decades. Recent years have brought a deep understanding of UM biology characterized by initiating mutations in the G proteins GNAQ and GNA11. Cytogenetic alterations, in particular monosomy of chromosome 3 and amplification of the long arm of chromosome 8, and mutation of the BRCA1-associated protein 1, BAP1, a tumor suppressor gene, or the splicing factor SF3B1 determine UM metastasis. Cytogenetic and molecular profiling allow for a very precise prognostication that is still not matched by efficacious adjuvant therapies. G protein signaling has been shown to activate the YAP/TAZ pathway independent of HIPPO, and conventional signaling via the mitogen-activated kinase pathway probably also contributes to UM development and progression. Several lines of evidence indicate that inflammation and macrophages play a pro-tumor role in UM and in its hepatic metastases. UM cells benefit from the immune privilege in the eye and may adopt several mechanisms involved in this privilege for tumor escape that act even after leaving the niche. Here, we review the current knowledge of the biology of UM and discuss recent approaches to UM treatment.

A phase I dose-escalation study of TAK-733, an investigational oral MEK inhibitor, in patients with advanced solid tumors

Purpose TAK-733, an investigational, selective, allosteric MEK1/2 inhibitor, has demonstrated antitumor effects against multiple cancer cell lines and xenograft models. This first-in-human study investigated TAK-733 in patients with solid tumors. Methods Patients received oral TAK-733 once daily on days 1–21 in 28-day treatment cycles. Adverse events (AEs) were graded using the Common Terminology Criteria for AEs version 3.0. Response was assessed using RECIST v1.1. Blood samples for TAK-733 pharmacokinetics and pharmacodynamics (inhibition of ERK phosphorylation) were collected during cycle 1. Results Fifty-one patients received TAK-733 0.2–22 mg. Primary diagnoses included uveal melanoma (24 %), colon cancer (22 %), and cutaneous melanoma (10 %). Four patients had dose-limiting toxicities of dermatitis acneiform, plus fatigue and pustular rash in one patient, and stomatitis in one patient. The maximum tolerated dose was 16 mg. Common drug-related AEs included dermatitis acneiform (51 %), diarrhea (29 %), and increased blood creatine phosphokinase (20 %); grade ≥ 3 AEs were reported in 27 (53 %) patients. Median T_max was 3 h; systemic exposure increased less than dose-proportionally over the dose range 0.2–22 mg. On day 21 maximum inhibition of ERK phosphorylation in peripheral blood mononuclear cells of 46–97 % was seen in patients receiving TAK-733 ≥ 8.4 mg. Among 41 response-evaluable patients, 2 (5 %) patients with cutaneous melanoma (one with BRAF L597R mutant melanoma) had partial responses. Conclusions TAK-733 had a generally manageable toxicity profile up to the maximum tolerated dose, and showed the anticipated pharmacodynamic effect of sustained inhibition of ERK phosphorylation. Limited antitumor activity was demonstrated. Further investigation is not currently planned.

ADAM 10 expression in primary uveal melanoma as prognostic factor for risk of metastasis

Uveal melanoma is the most frequent primary intraocular neoplasm in adults. Although malignant melanoma may be located at any point in the uveal tract, the choroid and ciliary body are more frequent locations than the iris. In the present study, we examined ADAM10 expression levels in primary uveal melanoma both with and without metastasis, and we evaluated their association with other high risk characteristics for metastasis in order to assess if ADAM10 can be used to predict metastasis. This study included a total of 52 patients, 23 men and 29 women, with uveal melanoma. A significantly high expression of ADAM-10 was seen in patients with metastasis (11/13, 84.6%), but not in patients without metastasis (15/39, 38.5%). In conclusion we found that ADAM10 expression was associated with a more rapid metastatic progression confirming its role in uveal melanoma metastasis.

Uveal Spindle Cell Tumor of Blue-Eyed Dogs: An Immunohistochemical Study

Immunohistochemical techniques were used to investigate the origin of a spindle cell tumor in the anterior uveal tract of dogs and the influence of ultraviolet radiation on the development of this tumor. Thirteen tumors were identified from the 4,007 canine ocular samples examined at the Comparative Ocular Pathology Laboratory of Wisconsin between 1978 and 2005. Siberian Husky and Siberian Husky mix dogs were overrepresented (10/13 dogs, overall median age 10 years). Light microscopic evaluation (all dogs) and electron microscopy (2 dogs) were performed. Immunohistochemical staining included alpha-smooth muscle actin (SMA), vimentin, S-100, desmin, glial fibrillary acidic protein (GFAP), Melan A, microphthalmic transcription factor (MITF-1), protein gene product 9.5 (PGP 9.5), laminin, gadd45, p53, proliferating cell nuclear antigen (PCNA), anti-UVssDNA (antibody for detection of (6–4)-dipyrimidine photoproducts), and telomerase reverse transcriptase (TERT). All tumors occurred in the iris with or without ciliary body involvement and were composed of spindle cells arranged in fascicles and whorls (variable Antoni A and B behavior). All tumors were positive when immunostained for vimentin and S-100. Nine of 13 tumors exhibited GFAP immunopositivity. All tumors were negative for SMA, desmin, Melan A, and MITF-1. Tumors were variably positive for PGP 9.5, laminin, gadd45, p53, PCNA, anti-UVssDNA, and TERT. Electron microscopy revealed intermittent basal laminae between cells. These tumors are morphologically and immunohistochemically most consistent with schwannoma. The relationship between spindle cell tumors of the anterior uvea of dogs, altered neural crest, blue iris color, and ultraviolet radiation has not yet been fully elucidated.

ARF6 Is an Actionable Node that Orchestrates Oncogenic GNAQ Signaling in Uveal Melanoma

Activating mutations in Gαq proteins, which form the α subunit of certain heterotrimeric G proteins, drive uveal melanoma oncogenesis by triggering multiple downstream signaling pathways, including PLC/PKC, Rho/Rac, and YAP. Here we show that the small GTPase ARF6 acts as a proximal node of oncogenic Gαq signaling to induce all of these downstream pathways as well as β-catenin signaling. ARF6 activates these diverse pathways through a common mechanism: the trafficking of GNAQ and β-catenin from the plasma membrane to cytoplasmic vesicles and the nucleus, respectively. Blocking ARF6 with a small-molecule inhibitor reduces uveal melanoma cell proliferation and tumorigenesis in a mouse model, confirming the functional relevance of this pathway and suggesting a therapeutic strategy for Gα-mediated diseases.

Uveal Melanomas Harbor Recurrent Activating Mutations in CYSLTR2

A mutation in the CYCLTR2 G-protein-coupled receptor promotes tumorigenesis in uveal melanomas.

Expression of Caveolin-1 in Human Cutaneous and Uveal Melanoma Cells

Caveolin-1 can act as a tumour promoter or suppressor depending on the cancer type and stage. In melanoma, information available concerning its expression is ambiguous. In this study, we investigated caveolin-1 mRNA and protein expression levels in human melanoma cell lines of different origin and progression stages. Metastatic cutaneous (WM-266-4, A375), primary cutaneous (WM- 115, IGR-39) and primary uveal (mel-202, 92-1) cells were used for quantitative RT-PCR, Western blotting and confocal microscopy. We observed significantly higher expression of caveolin-I mRNA in cutaneous than in uveal melanoma cells. In accordance, immunostaining of caveolin-I was stronger in cutaneous cell extracts, while protein bands of uveal origin displayed weak signals. Finally, we detected differences in the caveolin-I subcellular pattern of distribution between primary and metastatic cells. Overall, this is the first demonstration of caveolin-1 expression in human primary uveal melanoma cell lines and observation that the origin of cells (uveal/cutaneous) has an impact when considering the utility of caveolin-I as a melanoma cell marker.

[Progresses of DNA methylation in common ocular tumor]

DNA methylation is a major event of epigenetic modifications. In the presence of DNA methyltransferases (DNMT), the addition of methyl groups from cytosines can impact gene expression and alter cell and organism function. Methyl groups of CpG sites in the promoter can directly interfere with binding of transcription factors to their recognition cis elements or, on the other side, can facilitate interaction with a family of methyl-binding proteins and result in gene silencing. Analysis of DNA methylation includes genome-wide DNA methylation assessment, analysis of gene-specific DNA methylation and finding of new DNA methylation sites. The implication of DNA methylation has been suggested with the pathogenesis of retinoblastoma, uveal tract melanoma and ocular surface tumor. We focus on the progresses of DNA methylation on ocular tumors in this article.

The SDF-1/CXCR4 chemokine axis in uveal melanoma cell proliferation and migration

The stromal-cell-derived factor 1 (SDF-1)/chemokine receptor 4 (CXCR4) chemokine axis plays a key role in tumor migration. Here, we analyzed the axis in uveal melanoma (UM) proliferation and migration and investigated the effect of a chemical inhibitor of CXCR4, AMD3100, on UM. We found that CXCR4 was expressed in all five UM cell lines tested as well as the retinal pigment epithelium cell line ARPE-19 cells, while CXCR7 was only detected in OM290 and VUP cell lines. SDF-1 promotes the proliferation and migration of OCM-1 and OCM431 cell lines, while AMD3100 weakens this function. Taken together, our results show that the SDF-1/CXCR4 chemokine axis plays a key role in UM cell proliferation and migration and that AMD3100 can alleviate this function, which may offer a hint for UM treatment.

iTRAQ Quantitative Proteomic Comparison of Metastatic and Non-Metastatic Uveal Melanoma Tumors

BACKGROUND

Uveal melanoma is the most common malignancy of the adult eye. The overall mortality rate is high because this aggressive cancer often metastasizes before ophthalmic diagnosis. Quantitative proteomic analysis of primary metastasizing and non-metastasizing tumors was pursued for insights into mechanisms and biomarkers of uveal melanoma metastasis.

METHODS

Eight metastatic and 7 non-metastatic human primary uveal melanoma tumors were analyzed by LC MS/MS iTRAQ technology with Bruch's membrane/choroid complex from normal postmortem eyes as control tissue. Tryptic peptides from tumor and control proteins were labeled with iTRAQ tags, fractionated by cation exchange chromatography, and analyzed by LC MS/MS. Protein identification utilized the Mascot search engine and the human Uni-Prot/Swiss-Protein database with false discovery ≤ 1%; protein quantitation utilized the Mascot weighted average method. Proteins designated differentially expressed exhibited quantitative differences (p ≤ 0.05, t-test) in a training set of five metastatic and five non-metastatic tumors. Logistic regression models developed from the training set were used to classify the metastatic status of five independent tumors.

RESULTS

Of 1644 proteins identified and quantified in 5 metastatic and 5 non-metastatic tumors, 12 proteins were found uniquely in ≥ 3 metastatic tumors, 28 were found significantly elevated and 30 significantly decreased only in metastatic tumors, and 31 were designated differentially expressed between metastatic and non-metastatic tumors. Logistic regression modeling of differentially expressed collagen alpha-3(VI) and heat shock protein beta-1 allowed correct prediction of metastasis status for each of five independent tumor specimens.

CONCLUSIONS

The present data provide new clues to molecular differences in metastatic and non-metastatic uveal melanoma tumors. While sample size is limited and validation required, the results support collagen alpha-3(VI) and heat shock protein beta-1 as candidate biomarkers of uveal melanoma metastasis and establish a quantitative proteomic database for uveal melanoma primary tumors.

Intraocular Medulloepitheliomas and Embryonal Tumors With Multilayered Rosettes of the Brain: Comparative Roles of LIN28A and C19MC

PURPOSE

To compare immunohistochemical and genetic overlaps and differences between intraocular medulloepitheliomas and embryonal tumors with multilayered rosettes of the brain.

DESIGN

Retrospective histopathologic, immunohistochemical, and genetic analysis of 20 intraocular medulloepitheliomas.

METHODS

(1) Review of clinical data and hematoxylin-eosin-stained sections with (2) immunohistochemical staining of paraffin sections using a polyclonal antibody against the protein LIN28A, and (3) fluorescence in situ hybridization (FISH) testing for the amplification of the genetic locus 19q13.42 involving the C19MC cluster of miRNA. Ten retinoblastomas served as controls and to determine the specificity of these biomarkers for intraocular medulloepitheliomas.

RESULTS

Nineteen of the 20 intraocular medulloepitheliomas were either diffusely or focally LIN28A positive (weak, moderate, or strong). The most intense positivity correlated with aggressive behavior such as intraocular tissue invasion or extraocular extension. None of the cases studied by FISH harbored an amplicon for C19MC. The 10 retinoblastomas were LIN28A and C19MC negative.

CONCLUSION

LIN28A has a putative role in oncogenesis and is found only in embryonic cells and malignancies. Intraocular medulloepitheliomas and embryonal tumors with multilayered rosettes of the brain both display LIN28A positivity. Only the latter, however, display amplification of the 19q13.42 locus involving C19MC, implying that other causative factors are at play in intraocular medulloepitheliomas. More aggressive tumor behavior within the eye can be partially predicted by LIN28A staining intensity.

Detection of GNAQ mutations and reduction of cell viability in uveal melanoma cells with functionalized gold nanoparticles

BACKGROUND

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults. Early treatment may improve any chances of preventing metastatic disease, but diagnosis of small UM is challenging. Up to 95 % of all UMs carry somatic mutations in the G-coupled proteins GNAQ and GNA11 promoting anchorage-independent growth and proliferation. About 50 % of UMs are fatal. Once metastatic, patients have limited options for successful therapy.

METHODS

We have developed functionalized gold nanoparticles (AuNPs) to visualize transcripts of mutant GNAQ mRNA in living cells. In addition to their suitability as a specific tool for GNAQ mutation detection, we have developed a novel linker that enables conjugation of siRNAs to AuNPs allowing for greater and more rapid intracellular release of siRNAs compared to previously described approaches.

RESULTS

Binding of modified AuNPs to matching target mRNA leads to conformational changes, resulting in a detectable fluorescent signal that can be used for mutation detection in living cells. Knockdown of GNAQ with siRNA-AuNPs effectively reduced downstream signals and decreased cell viability in GNAQ mutant uveal melanoma cells.

CONCLUSION

AuNPs may in future be developed to serve as sensors for mutations of vital importance. The new release system for siRNA-AuNP improves previous systems, which conceivably will be useful for future therapeutic gene regulatory approaches.

New insights into the development of infantile intraocular medulloepithelioma

PURPOSE

To define the maturational sequence of 3 infantile intraocular medulloepitheliomas.

DESIGN

Retrospective clinicohistopathologic and immunohistochemical study.

METHODS

Immunoreactivity of paraffin sections for CRX (cone-rod homebox transcription factor) and NeuN (biomarker for neuronal differentiation) were investigated together with other biomarkers, including S100, glial fibrillary acidic protein, epithelial membrane antigen, and various cytokeratins.

RESULTS

Three infants (aged 1, 6, and 8 months) had iris neovascularization, 2 had anterior ciliary body tumors, and 1 a posterior tumor associated with a retinochoroidal coloboma. Each tumor displayed a premedullary monolayer of cuboidal epithelium that was S100(+), NeuN(-), and CRX(-) and that transitioned into a multilaminar medullary epithelium forming neurotubules with adluminal cells that were CRX(+). NeuN first appeared in ablumenal neurotubular cells in 1 tumor and was also discovered among neuroblast-appearing cells in another. The third tumor associated with a coloboma was CRX(-) and NeuN(-).

CONCLUSIONS

A simple premedullary epithelial monolayer appears to be the fundamental source for the tumor and its multilaminar medullary epithelium. CRX(+) and NeuN(+) cells within the multilayered medullary layer approximate expression patterns similar to those found in retinal development and differentiation. Discovery of these biomarkers in the neoplastic ciliary epithelium in a small number of tumors indicates preliminarily that the most anterior layers of the optic cup have a retained retinal and neuroglial differentiation potentiality. The third case was CRX(-) and NeuN(-) and possibly arose from embryonic pigment epithelium at the edge of the retinochoroidal coloboma. These immunohistochemical findings offer histogenetic and potential diagnostic insights.

The demethylating agent 5-Aza reduces the growth, invasiveness, and clonogenicity of uveal and cutaneous melanoma

PURPOSE

Uveal melanoma is the most common primary intraocular malignancy in adults. Although local disease can be controlled with radiation therapy or enucleation, many cases are complicated by metastases, which account for the significant mortality from this disease. To date, no chemotherapeutic regimens effectively treat local or metastatic disease. Epigenetic silencing of tumor suppressor genes has been shown to be an important factor in the growth and metastasis of many cancers. One form of epigenetic alteration is DNA methylation, which often occurs at promoter elements resulting in the silencing of target gene transcription.

METHODS

We used 5-aza-2'-deoxycytidine (5-Aza), a well characterized demethylating agent that is US Food and Drug Administration approved to decrease DNA methylation in multiple uveal and cutaneous melanoma cell lines.

RESULTS

Demethylation of melanoma cell lines using 5-Aza causes significant decreases in growth, invasion, and clonogenicity. Treatment of melanoma cells with combined 5-Aza therapy and irradiation showed an even more pronounced effect on cell viability. In addition, treatment with 5-Aza decreased the number of metastases from the eye to the lung in a murine cutaneous melanoma xenograft model.

CONCLUSIONS

We demonstrate in vitro and in vivo that demethylating agents such as 5-Aza may be promising chemotherapeutic agents for treating melanoma and decreasing progression to metastatic disease. These results provide proof of concept for an exciting potential therapy to reduce mortality from this disease. Future work will focus on identifying pathways that mediate these changes.

Effect of hypoxic stress on migration and characteristics of monocytes in uveal melanoma

IMPORTANCE

Among the characteristics of uveal melanoma that are associated with a poor prognosis are a large tumor size and the presence of increased numbers of lymphocytes and macrophages. In rapidly growing tumors, reduction in oxygen tension may occur with increased distance from blood vessels, which we hypothesize may lead to an inflammatory microenvironment, further stimulating tumor growth.

OBJECTIVES

To analyze whether hypoxia induces uveal melanoma cells to express proinflammatory cytokines and whether tumor supernatant (TSN) affects monocyte migration and differentiation.

DESIGN AND SETTING

The expression of proinflammatory genes in freshly cultured uveal melanoma samples was studied in an in vitro 24-hour hypoxic culture system using quantitative polymerase chain reaction. In addition, cell lines cultured under normoxic and hypoxic conditions were used. The effect of TSN on monocyte chemotaxis was tested using a transwell migration system and by analyzing monocyte differentiation. The levels of the cytokines CCL2, IL6, and PGE2 in TSN were determined by enzyme-linked immunosorbent assay.

PARTICIPANTS

Five cell lines (OCM8, 92.1, Mel270,Mel290 and OMM2.5) and 11 primary short-term cultures.

RESULTS

Exposure of freshly cultured uveal melanoma cells to hypoxia led to an increased expression of the proinflammatory cytokines PLGF (OMIM 601121), TGFβ (OMIM 190180), END1 (OMIM +131240), and ICAM1 (OMIM 147840) and a lower expression of AIMP1 (OMIM 603605) (EMAP2), CCL2 (MCP-1) (OMIM +158105), and IL1b (OMIM *147720). The TSN from cultured melanoma cell lines induced chemotaxis of monocytes, but this was independent of the normoxic or hypoxic state. The TSN of 1 cell line and 2 primary uveal melanoma cultures inhibited the dendritic cell maturation and did not induce M2 macrophage polarization in vitro.

CONCLUSIONS AND RELEVANCE

Our results indicate that under hypoxic conditions, immune response genes are differentially expressed in cultured primary uveal melanoma cells. The TSN from uveal melanoma cell lines is capable of affecting the chemotactic response and maturation of monocytes in vitro, but this is irrespective of hypoxia.

Mutant Gq/11 promote uveal melanoma tumorigenesis by activating YAP

Uveal melanoma (UM) is the most common cancer in adult eyes. Approximately 80% of UMs harbor somatic activating mutations in GNAQ or GNA11 (encoding Gq or G11, respectively). Herein, we show in both cell culture and human tumors that cancer-associated Gq/11 mutants activate YAP, a major effector of the Hippo tumor suppressor pathway that is also regulated by G protein-coupled receptor signaling. YAP mediates the oncogenic activity of mutant Gq/11 in UM development, and the YAP inhibitor verteporfin blocks tumor growth of UM cells containing Gq/11 mutations. This study reveals an essential role of the Hippo-YAP pathway in Gq/11-induced tumorigenesis and suggests YAP as a potential drug target for UM patients carrying mutations in GNAQ or GNA11.

Hippo-independent activation of YAP by the GNAQ uveal melanoma oncogene through a trio-regulated rho GTPase signaling circuitry

Mutually exclusive activating mutations in the GNAQ and GNA11 oncogenes, encoding heterotrimeric Gαq family members, have been identified in ∼ 83% and ∼ 6% of uveal and skin melanomas, respectively. However, the molecular events underlying these GNAQ-driven malignancies are not yet defined, thus limiting the ability to develop cancer-targeted therapies. Here, we focused on the transcriptional coactivator YAP, a critical component of the Hippo signaling pathway that controls organ size. We found that Gαq stimulates YAP through a Trio-Rho/Rac signaling circuitry promoting actin polymerization, independently of phospholipase Cβ and the canonical Hippo pathway. Furthermore, we show that Gαq promotes the YAP-dependent growth of uveal melanoma cells, thereby identifying YAP as a suitable therapeutic target in uveal melanoma, a GNAQ/GNA11-initiated human malignancy.

Establishment of novel cell lines recapitulating the genetic landscape of uveal melanoma and preclinical validation of mTOR as a therapeutic target

Uveal melanoma (UM) is the most common primary tumor of the eye in adults. There is no standard adjuvant treatment to prevent metastasis and no effective therapy in the metastatic setting. We have established a unique panel of 7 UM cell lines from either patient's tumors or patient-derived tumor xenografts (PDXs). This panel recapitulates the molecular landscape of the disease in terms of genetic alterations and mutations. All the cell lines display GNAQ or GNA11 activating mutations, and importantly four of them display BAP1 (BRCA1 associated protein-1) deficiency, a hallmark of aggressive disease. The mTOR pathway was shown to be activated in most of the cell lines independent of AKT signaling. mTOR inhibitor Everolimus reduced the viability of UM cell lines and significantly delayed tumor growth in 4 PDXs. Our data suggest that mTOR inhibition with Everolimus, possibly in combination with other agents, may be considered as a therapeutic option for the management of uveal melanoma.

Uveal melanoma expresses NK-1 receptors and cyclosporin A induces apoptosis in human melanoma cell lines overexpressing the NK-1 receptor

Substance P and neurokinin-1 (NK-1) receptor antagonists respectively induce proliferation and growth inhibition in human melanoma cell lines. The presence of NK-1 receptors in human melanoma cell lines and samples has been reported, but the presence of NK-1 receptors has not been demonstrated in uveal melanomas. It is known that melanoma express the tachykinin 1 receptor (TAC1R) gene. This gene is overexpressed in several human cancer cell lines, but such overexpression is currently unknown in human malignant melanoma cell lines (COLO 858, MEL HO, COLO 679). In this study, we attempt to demonstrate the overexpression of the TAC1R gene in such cells. We performed an in vitro study by real-time quantitative RT-PCR for TAC1R and found that the NK-1 receptor was overexpressed in the three human melanoma cell lines studied. Using a knockdown method, we demonstrate that the NK-1 receptor is involved in the viability of the COLO 858 melanoma cell line. Immunohistochemistry was also used to demonstrate NK-1 receptors in uveal melanoma samples. We observed that NK-1 receptors were present in the 21/21 uveal melanomas. In addition, cyclosporin A inhibited the growth of the three melanoma cell lines studied in a dose-dependent manner, and after the administration of this immunosuppresive drug apoptosis was observed. This indicates at least that the antitumor action of cyclosporin A is mediated by the NK-1 receptor. Our findings suggest that the NK-1 receptor could be a promising target in the treatment of human melanomas.

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.

MicroRNA 145 may play an important role in uveal melanoma cell growth by potentially targeting insulin receptor substrate-1

BACKGROUND

MicroRNAs (miRNAs) contribute to tumorigenesis by acting as either oncogenes or tumor suppressor genes. In this study, we investigated the role of miR-145 in the pathogenesis of uveal melanoma.

METHODS

Expression profiles of miRNAs in uveal melanoma were performed using Agilent miRNA array. Quantitative real-time polymerase chain reaction was used to screen the expression levels of miR-145 in normal uveal tissue, uveal melanoma tissue, and uveal melanoma cell lines. Lenti-virus expression system was used to construct MUM-2B and OCM-1 cell lines with stable overexpression of miR-145. Cell proliferation, cell cycle, and cell apoptosis of these miR-145 overexpression cell lines were examined by MTT assay and flow cytometry respectively. The target genes of miR-145 were predicted by bioinformatics and confirmed using a luciferase reporter assay. The expression of insulin-like growth factor-1 receptor (IGF-1R), insulin receptor substrate-1 (IRS-1) proteins was determined by Western blotting analysis. IRS-1 was knocked down in OCM-1 cells. TUNEL, BrdU, and flow cytometry assay were performed in IRS-1 knocked down OCM-1 cell lines to analyze its function.

RESULTS

Forty-seven miRNAs were up regulated in uveal melanoma and 61 were down regulated. miR-145 expression was significantly lower in uveal melanoma sample and the cell lines were compared with normal uveal sample. Overexpression of miR-145 suppressed cell proliferation by blocking the G1 phase entering S phase in uveal melanoma cells, and promoted uveal melanoma cell apoptosis. IRS-1 was identified as a potential target of miR-145 by dual luciferase reporter assay. Knocking down of IRS-1 had similar effect as overexpression of miR-145.

CONCLUSION

miR-145 might act as a tumor suppressor in uveal melanoma, and downregulation of the target IRS-1 might be a potential mechanism.