Mutant Uveal Melanoma Research Articles

Abstract 2138: RasGRP3 mediates MAPK pathway activation in GNAQ mutant uveal melanoma

Abstract Uveal melanoma (UM) is the most common intraocular malignancy in adults and no effective treatment options are available for metastatic disease. Over 80% of UM show mutations in the Gαq family members GNAQ and GNA11. MAP-kinase pathway activation in part mediated by protein kinase C (PKC) has been shown as one critical contributing factor to GNAQ-mediated oncogenesis. However PKC inhibition alone does not completely suppress MAPK signaling. A more refined understanding of the signaling cascade linking MAPK signaling to mutant GNAQ or GNA11 is required to develop more effective strategies for targeted therapy. Among more than 10 different PKC isoforms, we identified both PKC δ and PKC ϵ to be required and sufficient to activate MAPK pathway in GNAQ mutant melanomas by using siRNA mediated knock-down and co-transfection of GNAQQ209L and specific PKC isoform cDNAs. Overexpression of GNAQQ209L in 293FT cells increased Ras-GTP level and knock down of three Ras isoforms in GNAQ mutant uveal melanoma cell lines decreased MAPK signaling. Microarray analysis of 5 different GNAQ/11 mutant and 5 NRAS/BRAF-mutant melanoma cells revealed RasGRP3, a Ras-guanyl nucleotide exchange factor (RasGEF), ranks at the top of 487 differentially expressed genes between (cut off : p<0.05, fold change >2 or <-2). Quantitative RT-PCR and western blot confirmed markedly (>100 fold) elevated RasGRP3 levels in GNAQ/11 mutant melanoma cells, while other RasGEFs were not significantly altered. Knock down of RasGRP3 decreased MAPK signaling and proliferation in GNAQ mutant melanoma cells, while it no effect on BRAF mutant cells. Mutating the PKC phosphorylation site of RasGRP3 (T133) partially attenuated RasGRP3-mediated MAPK signaling. Overexpression of PKC δ and PKC ϵ increased RasGRP3 T133 phosphorylation but not PKC α and PKC ζ. While PKC inhibition completely abrogated RasGRP3 T133 phosphorylation, it did not fully suppress RasGRP3-mediated MAPK signaling, indicating that its activating effect only partly requires PKC. We found that RasGRP3 activation mediated by its diacylglycerol(DAG) binding C1 domain provides an independent conduit of activation, which is augmented by PKC-mediated phosphorylation at T133. DAG is a second messenger that is released by phospholipase C, a direct effector of activated GNAQ/11. Finally, we found that the markedly elevated RasGRP3 expression in GNAQ mutant melanoma cell lines is a direct consequence of the oncogenic signaling and is mediated by PKC δ and ϵ. Hence, our data identify RasGRP3 as a critical signaling node linking oncogenic signaling downstream of GNAQ/11 to the Ras/Raf/MEK/ERK pathway through three mechanisms: phosphorylation by PKC δ and ϵ, binding of the second messenger DAG, and by upregulation of its protein level as a consequence of oncogenic GNAQ-mediated activation of PKC δ and PKC ϵ. The findings nominate RasGRP3 as a possible therapeutic target for cancers driven by oncogenic GNAQ/11. Citation Format: Xu Chen, Qiuxia Wu, Philippe Depeille, Jeroen P. Roose, Boris C. Bastian. RasGRP3 mediates MAPK pathway activation in GNAQ mutant uveal melanoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2138. doi:10.1158/1538-7445.AM2015-2138

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

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. 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. 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. 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.

GNAQ and GNA11 mutations in uveal melanoma.

G-protein-coupled receptors signal through heterotrimeric G proteins, Gα and G-βγ, to manage numerous aspects of physiologic homeostasis. Many neoplastic processes harbor alterations in G-protein-coupled receptors and/or G-α proteins, best exemplified by recurrent activating mutations in GNAQ or GNA11 in uveal melanomas. This review will discuss the multiple activated signaling targets downstream of mutant GNAQ and GNA11 in uveal melanoma, including MEK, PI3-kinase/Akt, protein kinase C, and YAP. This knowledge has led to the rapid expansion of clinical trials that are specific to patients with uveal melanoma and promises future breakthroughs in therapies.

Oncogenic GNAQ and GNA11 mutations in uveal melanoma in Chinese.

PurposeTo examine whether GNAQ and GNA11 somatic mutations previously identified in uveal melanomas of Caucasians are associated with uveal melanomas in Chinese patients.MethodsUveal melanomas treated by primary enucleation in Chinese patients underwent a mutation analysis of GNAQ and GNA11 with sequencing of exon 5 and exon 4.ResultsThe study included 50 patients with uveal melanoma and with a mean age of 47.6±13.0 years. During the follow-up of at least 3 years, 20 (40%) patients developed extraocular metastases. The frequencies of GNAQ and GNA11 somatic mutations in uveal melanoma were 18% (9/50) and 20% (10/50), respectively. The mutations occurred exclusively in codon 209 of exon 5. No mutations were detected in exon 4. Mutations affecting codon 209 in GNAQ were c.626A>C(Q209P) (78%) and c.626A>T(Q209L) (22%). Mutations affecting codon 209 in GNA11 were exclusively c.626A>T(Q209L) (100%). In none of the tumors, mutations of BRAF and NRAS were detected. GNAQ/11 mutations were marginally (P = 0.045) associated with optic disc involvement. In Kaplan-Meier analysis, metastasis-free survival was not significantly (P = 0.94) associated with GNAQ/11 mutations.ConclusionsMutations of GNAQ and GNA11 can be found in Chinese patients as in Caucasian patients with uveal melanoma, with a higher frequency reported for Caucasian patients.

Clinical significance of immunohistochemistry for detection of BAP1 mutations in uveal melanoma

Uveal melanoma is a lethal cancer with a strong propensity to metastasize. Limited therapeutic options are available once the disease has disseminated. A strong predictor for metastasis is the loss of chromosome 3. Inactivating mutations in BAP1 encoding the BRCA1-associated protein 1 and located on chromosome 3p21.1, have been described in uveal melanoma and other types of cancer. In this study, we determined the prevalence of somatic BAP1 mutations and examined whether these mutations correlate with the functional expression of BAP1 in uveal melanoma tissue and with other clinical, histopathological and chromosomal parameters. We screened a cohort of 74 uveal melanomas for BAP1 mutations, using different deep sequencing methods. The frequency of BAP1 mutations in our study group was 47%. The expression of BAP1 protein was studied using immunohistochemistry. BAP1 staining was absent in 43% of the cases. BAP1 mutation status was strongly associated with BAP1 protein expression (P<0.001), loss of chromosome 3 (P<0.001), and other aggressive prognostic factors. Patients with a BAP1 mutation and absent BAP1 expression had an almost eightfold higher chance of developing metastases compared with those without these changes (P=0.002). We found a strong correlation between the immunohistochemical and sequencing data and therefore propose that, immunohistochemical screening for BAP1 should become routine in the histopathological work-up of uveal melanoma. Furthermore, our analysis indicates that loss of BAP1 may be particularly involved in the progression of uveal melanoma to an aggressive, metastatic phenotype.

Abstract 1410: Gnaq/11 mutant uveal melanoma is susceptible to Brd4 inhibition by JQ1

Abstract Uveal melanoma (UM) represents the most common intraocular malignancy in the United States, and there are no effective treatments for this aggressive disease. Uveal melanoma is characterized by oncogenic mutations in Gnaq and Gna11, which activate the mitogen-activated protein kinase pathway (MAPK). Furthermore, both primary and metastatic UM are characterized by genetic abnormalities, including the amplification of the chromosomal arm 8q and monosomy of chromosome 3, which are significantly associated with poor prognosis. The oncogene MYC, which is located on 8q24.1, is amplified in nearly 70% of uveal melanoma, and is also regulated by the MAPK pathway. Chromatin regulators have become attractive targets for cancer therapy. In particular, the BET-bromodomain inhibitor JQ1 has shown selective inhibition of c-Myc expression, followed by the suppression of c-Myc-dependent target genes. We examined the effects of JQ1 in a panel of 8 UM cell lines, including cell lines with Gnaq/Gna11 mutations (92.1, Omm1.3, Mel270, Mel202, Omm1), a cell line with MYC amplification (Mel290), and cells without either mutation or amplification (C918, Mel285). The Gnaq/Gna11 mutant cells were the most sensitive to growth inhibition at nanomolar concentrations of JQ1 (IC50=200nM), followed by the cell line with amplified MYC (IC50=1μM), while the cells without mutation or amplification exhibited little inhibition. We also examined the biochemical effects of JQ1 treatment, which caused a dose- and time-dependent suppression of c-Myc as well as survivin, XIAP, ERK1 and E2F1, while p21and the pro-apoptotic protein Bim were induced in all the cell lines. Interestingly, JQ1 also suppressed the anti-apoptotic protein Bcl-xL and induced PARP cleavage only in the Gnaq/Gna11 mutant cells. Flow cytometric analysis indicated a cell cycle arrest in G1 in all the cell lines and an apoptotic population in sub-G1in the mutant cells. Furthermore, treatment with JQ1 resulted in significant antitumor activity in mouse xenograft models of uveal melanoma with Gnaq mutation. All together, these observations support the evidence that JQ1 represent a promising therapeutic approach for uveal melanoma with Gnaq/Gna11 mutations. Citation Format: Grazia Ambrosini, Gary K. Schwartz. Gnaq/11 mutant uveal melanoma is susceptible to Brd4 inhibition by JQ1. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1410. doi:10.1158/1538-7445.AM2014-1410

SF3B1 and EIF1AX mutations in uveal melanoma: a protective factor, or not?

AbstractPurpose The recent identification of mutations in the splicing factor SF3B1 and translation initiation factor EIF1AX prompted us to investigate the occurrence of these mutations in our uveal melanoma (UM) cohort.Methods Nineteen tumours were subjected to whole exome sequencing. In addition, the SF3B1 (exon 14) and EIF1AX (exon 1 and 2) mutation status was determined in 95 UM by Sanger sequencing.Results Mutations in SF3B1 were identified in 26% of UM and 19% harboured a mutation in either exon 1 or 2 of the EIF1AX gene. SF3B1 and EIF1AX mutations correlated significantly with good prognostic features such as spindle cell type, absence of closed vascular loops, positive BAP1 immunohistochemistry staining and disomy 3. Univariate analyses of EIF1AX mutated cases compared to those without EIF1AX mutations showed a significantly increase in disease‐free survival (DFS). Overall, the SF3B1 mutated cases did not show a significant difference in DFS compared to SF3B1 wild types. After stratifying for chromosome 3 status, patients with a disomy 3 UM and a SF3B1 mutation had a worse DFS compared to those with a disomy 3 UM and a wild type SF3B1 (P &lt; 0.01).Conclusion SF3B1 and EIF1AX mutations occur in approximately a quarter of UM. Mutations in these genes associate with favourable prognostic features. In our study, we also reveal that patients with a normal chromosome 3 UM and a SF3B1 mutation have a higher risk of developing late metastasis.

GNAQ/11 Mutations in Uveal Melanoma: Is YAP the Key to Targeted Therapy?

GNAQ and GNA11 are frequently mutated in uveal melanoma, but they remain difficult therapeutic targets. In this issue of Cancer Cell, Feng and colleagues and Yu and colleagues demonstrate that the oncogenic activity of mutant GNAQ/11 is mediated at least in part through YAP, potentially uncovering a new therapeutic strategy.

The Phosphoinositide 3-Kinase α Selective Inhibitor BYL719 Enhances the Effect of the Protein Kinase C Inhibitor AEB071 in GNAQ/GNA11-Mutant Uveal Melanoma Cells

G-protein mutations are one of the most common mutations occurring in uveal melanoma activating the protein kinase C (PKC)/mitogen-activated protein kinase and phosphoinositide 3-kinase (PI3K)/AKT pathways. In this study, we described the effect of dual pathway inhibition in uveal melanoma harboring GNAQ and GNA11 mutations via PKC inhibition with AEB071 (sotrastaurin) and PI3K/AKT inhibition with BYL719, a selective PI3Kα inhibitor. Growth inhibition was observed in GNAQ/GNA11-mutant cells with AEB071 versus no activity in wild-type cells. In the GNAQ-mutant cells, AEB071 decreased phosphorylation of myristoylated alanine-rich C-kinase substrate, a substrate of PKC, along with ERK1/2 and ribosomal S6, but persistent AKT activation was present. BYL719 had minimal antiproliferative activity in all uveal melanoma cell lines, and inhibited phosphorylation of AKT in most cell lines. In the GNA11-mutant cell line, similar effects were observed with ERK1/2 inhibition, mostly inhibited by BYL719. With the combination treatment, both GNAQ- and GNA11-mutant cell lines showed synergistic inhibition of cell proliferation and apoptotic cell death. In vivo studies correlated with in vitro findings showing reduced xenograft tumor growth with the combination therapy in a GNAQ-mutant model. These findings suggest a new therapy treatment option for G-protein-mutant uveal melanoma with a focus on specific targeting of multiple downstream pathways as part of combination therapy.

Simultaneous Inhibition of the HGF/MET and Erk1/2 Pathways Affect Uveal Melanoma Cell Growth and Migration

PurposeNearly all primary uveal melanoma (UM) that metastasize involve the liver. Hepatocyte growth factor (HGF) is proposed to be an important microenvironmental element in attracting/supporting UM metastasis through activation of MET. The majority (>85%) of UM express mutations in the G-alpha proteins, that drive the MEK-ERK1/2 pathway. Thus, we proposed that the combination of MET and MEK inhibition would inhibit the growth and migration of G-alpha protein mutant versus non-mutant UM cells.MethodsWestern-blots demonstrated the relative protein levels of ERK1/2 and MET in UM cells. Cells were treated with the small molecule inhibitors AZD6244 (MEKi) and/or MK-8033 (METi) and downstream markers evaluated. Further studies determined the effect of combination MEKi and METi treatment on cell growth, apoptosis and migration.ResultsAll G-alpha protein mutant UM cell lines express MET mRNA and protein. The level of mRNA expression correlates with protein expression. MEKi, but not METi treatment results in markedly reduced ERK1/2 phosphorylation. Either MEKi or METi treatment alone results in reduced cell proliferation, but only modest induction of apoptosis. The combination MEKi+METi results in significant reduction of proliferation in G-alpha protein mutant cells. UM cell migration was blocked by METi, but not MEKi treatment.ConclusionsMET protein expression showed no correlation with G-alpha protein mutation status. Combining MEKi with METi treatment has added benefit to either treatment alone in reducing G-alpha protein mutant UM cell growth. Combining METi with MEKi treatment adds the effect of limiting uveal melanoma cell migration.

A Molecular Revolution in Uveal Melanoma: Implications for Patient Care and Targeted Therapy

Uveal melanoma is the most common primary intraocular malignancy and has a strong propensity for fatal metastasis. Recent advances in the molecular genetics of uveal melanoma are revolutionizing our understanding of this cancer and the care of patients. The development of a new molecular classification of uveal melanoma based on a widely available 15-gene expression profile now allows patients at high risk of metastasis to be identified early so that individualized management can be offered. The recent discovery of major driver mutations in uveal melanoma provide a rational basis for development of new targeted therapies. Taken together, these advances are transforming our understanding and management of uveal melanoma with the ultimate goal of improving patient outcomes.

Combined PKC and MEK inhibition for treating metastatic uveal melanoma

Uveal melanoma (UM) is the most common primary intraocular malignancy and the second most common form of melanoma. UM has a strong tendency for metastatic disease, and no effective treatments have yet been identified. Activating oncogenic mutations are commonly found in GNAQ and GNA11 in UM, and inhibiting key downstream effectors of the GNAQ/11 signaling pathway represents a rational therapeutic approach for treating metastatic UM. Chen et al., doi:10.1038/onc.2013.418, now confirm activation of the MAPK and PKC pathways as a result of GNAQ and GNA11 activating mutations in melanocytes, and they demonstrate that MAPK activation occurs downstream of PKC activation. PKC inhibitors disrupt MAPK signaling and block proliferation of GNAQ/11 mutant UM cell lines and slow the in vivo growth of xenografted UM tumors without inducing their shrinkage. However, a combination of PKC and MEK inhibition led to sustained MAPK pathway inhibition and tumor regression in vivo. Hence, the authors concluded that MEK and PKC inhibition is synergistic, with superior efficacy to treatment of GNAQ/GNA11 mutant UMs with either drug alone.

Abstract C149: The PKC inhibitor Sotrastaurin selectively inhibits the growth of GNAQ mutant uveal melanoma.

Abstract GNAQ mutations are early and frequent events in the pathology of Uveal Melanoma. These mutations hyper-activate PLCb-PKC-ERK1/2 signaling resulting in PKC dependence. Targeting GNAQ mutant Uveal Melanoma Cells with the PKC inhibitor AEB071 (Sotrastaurin) leads to pathway modulation and growth inhibition. The Myristoylated Alanine-rich C-kinase Substrate (MARCKS) is directly phosphorylated by PKC and can be used as a readout for PKC activation. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C149. Citation Format: Rosemary Barrett, Ribo Guo, Jing Yuan, Vesselina Cooke, Anthony Vattay, Joshua Korn, Guiqing Liang, Xin Li, Ramu Thiruvamoor, Andrew Wylie, Anka Bric, Nicholas Keen, William Sellers. The PKC inhibitor Sotrastaurin selectively inhibits the growth of GNAQ mutant uveal melanoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C149.

Protein Kinase C Inhibitors as Novel Radiosensitizing Agents in the Treatment of Primary GNAQ Mutant Uveal Melanoma

Radiation therapy (RT) is the standard of care approach for treatment of patients with primary uveal melanoma (UM). However, since the tumors are generally radioresistant, large fraction sizes of radiation are required to achieve tumor cell kill, which leads to an increase in normal tissue toxicity and frequently results in vision-threatening radiation complications. Activating somatic mutations in the G protein αq-subunit, GNAQ, have been recently identified to be present in approximately 50% of UM patients.

Characterisation of novel uveal melanoma cell lines under serum-free conditions

The establishment of long-term uveal melanoma (UM) cell lines is difficult. However, studying living cells and their behaviour in the presence of other cells and the extracellular matrix is important in terms of understanding tumour biology and malignant behaviour. We have established three UM cell lines and report a first characterisation of these cell lines. Three established UM cell lines (UMT2, UMT26 and UMT33) were analysed according to their morphologic characteristics, melanocytic differentiation, adhesion on different extracellular matrices and proliferative activity. Copy number changes of chromosomes 1, 3, 6 and 8 were studied by multiplex ligation-dependent probe amplification (MLPA). Oncogenic mutations in UM involving exons 4 and 5 of GNAQ and GNA11, respectively, were analysed by sequencing. All cell lines grew in suspension. UMT2 cells were homogeneous, UMT26 and UMT33 cells heterogeneous with regard to cell size and pigmentation. All UM cell lines revealed a melanocytic differentiation. UMT2 and 33 adhered on various extracellular matrices, while UMT26 only adhered to basal membrane extract (BME). This difference corresponded to the different expression of various integrins. Ki67 was expressed by 89% of UMT2 and 95% of UMT33 cells, which thus were in a proliferative stage, while only 2% of UMT26 cells revealed immunostaining for this proliferation marker. The doubling time of UMT2 was 3 days, 12 days for UMT33, and circa 3-4 months for UMT26. MLPA revealed disomy 3 in UMT2 and monosomy 3 in UMT33. The same point mutation was found in UMT2, 26 and 33, in exon 5 of GNA11 at codon 209 (p.Q209L). The establishment of UM cell lines under serum-free conditions is possible. Characterisation of UMT2, 26, and 33 revealed obvious differences in cytomorphology, melanocytic differentiation, adhesion on extracellular matrices, and proliferative activity. UMT2, 26 and 33 showed the same oncogenic mutation in exon 5 of GNA11.

Identification of Unique MEK-Dependent Genes in GNAQ Mutant Uveal Melanoma Involved in Cell Growth, Tumor Cell Invasion, and MEK Resistance

Metastatic uveal melanoma represents the most common intraocular malignancy with very poor prognosis and no effective treatments. Oncogenic mutations in the G-protein α-subunit q and 11 have been described in about 85% of uveal melanomas and confer constitutive activation. Multiple signaling pathways are induced as a consequence of GNAQ/11 activation, which include the MEK/ERK kinase cascade. We analyzed the transcriptional profile of cell lines treated with a mitogen-activated protein (MAP)/extracellular signal-regulated (ERK) kinase (MEK) inhibitor to identify gene targets of activated GNAQ and to evaluate the biologic importance of these genes in uveal melanoma. We conducted microarray analysis of uveal melanoma cell lines with GNAQ mutations treated with the MEK inhibitor selumetinib. For comparison, we used cells carrying BRAF(V600E) and cells without either mutation. Changes in the expression of selected genes were then confirmed by quantitative real-time PCR and immunoblotting. We found that GNAQ mutant cells have a MEK-dependent transcriptional output and identified a unique set of genes that are downregulated by MEK inhibition, including the RNA helicase DDX21 and the cyclin-dependent kinase regulator CDK5R1 whereas Jun was induced. We provide evidence that these genes are involved in cell proliferation, tumor cell invasion, and drug resistance, respectively. Furthermore, we show that selumetinib treatment regulates the expression of these genes in tumor tissues of patients with metastatic GNAQ/11 mutant uveal melanoma. Our findings define a subset of transcriptionally regulated genes by selumetinib in GNAQ mutant cells and provide new insights into understanding the biologic effect of MEK inhibition in this disease.

Pyrophosphorolysis DetectsB-RAFMutations in Primary Uveal Melanoma

Mutations in the genes that control cell proliferation in cutaneous melanoma are generally uncommon in uveal melanoma. Despite the absence of known activating mutations, the RAF-MEK-ERK, or mitogen-activated protein kinase (MAPK), pathway is usually activated in uveal melanoma. An assay with increased potential to identify mutations is now available, and this study was therefore conducted to reanalyze uveal melanoma cell lines and primary tumors for this mutation. Eleven uveal melanoma cell lines and 45 primary uveal melanomas were analyzed for mutations in exon 15 of the B-RAF gene by using pyrophosphorolysis-activated polymerization (PAP). Mutations were validated by sequencing of the PAP product. B-RAF mutations were detected in cell lines OCM-1 and -3 (V600E) and in six primary uveal melanomas. The V600K mutation was detected in one primary uveal melanoma, for which the V600E assay turned out to be sensitive as well. Direct sequencing of the exon 15 PCR product did not reveal the mutations found with the PAP-assay, indicating a low frequency of the mutant allele in primary samples. Because of the very sensitive PAP technology, B-RAF mutations were found in cell lines and primary uveal melanomas, which suggests that they may occasionally play a role in the activation of the MAPK pathway in uveal melanoma and indicates a higher prevalence of B-RAF mutations in uveal melanoma than was reported earlier. However, the relative scarcity of the B-RAF mutation excludes an elemental role for this mutation in uveal melanoma.

Chromosomal Mutations in Uveal Melanoma - The Good, The Bad, and The Ugly

Chromosomal Mutations in Uveal Melanoma - The Good, The Bad, and The Ugly

Detection of BRAF gene mutation in primary choroidal melanoma tissue

Numerous BRAF mutations have been detected in melanoma biopsy specimens and cell lines. In contrast, several studies report lack of BRAF mutations in uveal melanoma including primary and metastatic choroidal and ciliary body melanomas. To our knowledge, for the first time, here we report a case of choroidal melanoma harboring the BRAF mutation (V600E). The activation of RAF/MEK/ERK pathway, although independent of BRAF mutation, was reported in uveal melanoma. The presence of V600E mutation indicates that the RAF/MEK/ERK pathway, in addition to cutaneous melanoma progression, may play a role in the choroidal melanoma development.

Prevalence of the BRCA2 6174 del T mutation in Israeli uveal melanoma patients.

Substantial differences exist in the incidence rates of uveal melanoma (UM) among Israeli Jewish subpopulations: high in immigrants from North America and Europe (Ashkenazic) and low in immigrants from Africa and Asia (Sepharadic). This trend persists in Israeli-born individuals when stratified by their ancestral place of birth. There have been several anecdotal reports of uveal melanoma occurring in breast cancer families with mutations in the BRCA2 gene as well as one systematic study reporting BRCA2 mutations in UM. A single BRCA2 mutation, 6174 del T, occurs in about 1% of the Ashkenazic population and rarely in non-Ashkenazic. To assess the contribution of this germline mutation to uveal melanoma in Jewish Israeli patients, we tested this relationship through analysis of blood samples from a series of UM patients. A total of 153 cases (84 female, 69 male) were available for study, which represents 30% of all cases of UM diagnosed in Israel during the period 1984-1999 (82% for the period 1992-1999). Of the 143 UM patients for which a result could be obtained (4 due to refusals, 6 due to damage to the blood sample), 4 (2.8%, 95% confidence interval [CI] 0-5.6) carried the 6174 del T mutation. Assuming a population frequency of the mutation of 1% as estimated among Ashkenazic Jews in the United States, the probability of observing 4 or more carriers with the 6174 del T mutation, assuming no relationship between uveal melanoma and BRCA2, is 0.057. Although our study confirms the relationship between uveal melanoma and BRCA2, it is clear that the 6174 del T mutation accounts for only a small fraction of all Israeli UM cases. Therefore, BRCA2 mutations are likely to account for an even smaller proportion in populations with low frequencies of BRCA2 alterations.