Clinical outcomes in metastatic uveal melanoma treated with PD-1 and PD-L1 antibodies

BACKGROUND

Antibodies inhibiting the programmed death receptor 1 (PD-1) have demonstrated significant activity in the treatment of advanced cutaneous melanoma. The efficacy and safety of PD-1 blockade in patients with uveal melanoma has not been well characterized.

METHODS

Fifty-eight patients with stage IV uveal melanoma received PD-1 or PD-1 ligand (PD-L1) antibodies between 2009 and 2015 at 9 academic centers. Patients who were evaluable for response were eligible for the analysis. Imaging was performed every 12 weeks and at the investigators' discretion. Safety and clinical efficacy outcomes, including the best overall response, progression-free survival (PFS), and overall survival (OS), were retrospectively determined.

RESULTS

Of 56 eligible patients, 48 (86%) had received prior therapy, and 35 (63%) had received treatment with ipilimumab. Three patients had an objective response to ipilimumab, and 8 had stable disease as their best response. Thirty-eight patients (68%) received pembrolizumab, 16 (29%) received nivolumab, and 2 (4%) received atezolizumab. Objective tumor responses were observed in 2 patients for an overall response rate of 3.6% (95% confidence interval [CI], 1.8%-22.5%). Stable disease (≥6 months) was observed in 5 patients (9%). The median PFS was 2.6 months (95% CI, 2.4-2.8 months), and the median OS was 7.6 months (95% CI, 0.7-14.6 months). There was no association between prior treatment with ipilimumab or liver-directed therapy and PFS or OS. Treatment was well tolerated, and only 1 patient discontinued treatment because of toxicity.

CONCLUSIONS

PD-1 and PD-L1 antibodies rarely confer durable remissions in patients with metastatic uveal melanoma. Clinical trial enrollment should be prioritized in this population. Cancer 2016;122:3344-3353. © 2016 American Cancer Society.

Predominant expression of T cell receptor V alpha 7 in tumor-infiltrating lymphocytes of uveal melanoma

Expression of T cell receptor (TCR) V alpha genes in tumor-infiltrating lymphocytes (TILs) within intraocular melanoma was studied. Primers for 18 different human TCR V alpha families were used to analyze TCR V alpha-C alpha gene rearrangements in TIL in these melanomas obtained at surgery. A limited number of TCR V alpha genes were expressed and rearranged in these tumors, and TILs expressing V alpha 7 were found in seven of eight of these uveal melanomas. TCR gene usage is also restricted in experimental autoimmune disease, in T cells within organs like skin and other epithelial tissues, and in the brain of patients with multiple sclerosis (MS). The restricted usage of TCR genes in TIL may indicate that a specific antigen in these melanomas is targeted.

Prognostic parameters in uveal melanoma: a review

Histologic cell type, largest tumor diameter and tumor location have traditionally been regarded as the leading predictors of survival for uveal melanoma. Morphological cell typing is, however, subjective to variations in interpretation. More objective classification parameters have emerged from extensive cytomorphometrical and DNA flow cytometrical studies. For patients with uveal melanoma there is no effective therapy if metastases have developed, and the median survival after clinical diagnosis of hepatic metastases is extremely poor. Current research focuses on the mechanisms underlying the metastatic process, including tumor vasculature, cytogenetics, oncogene activation, immunology, melanoma-associated antigens and tumor cell migration (cell-cell and cell-matrix interaction). Several new prognostic parameters have emerged from these studies, such as closed vascular patterns, loss of one chromosome 3, and different indices of cell proliferation. Furthermore, considerable genotypical and phenotypical differences have been found between uveal and cutaneous melanoma. In prospective studies on large series of melanomas a combination of histopathological and/or clinical prognostic parameters might be selected with high sensitivity and specificity, providing a way of selecting patients at high risk of developing metastatic disease, who might be eligible for adjuvant therapy.

Molecular profiling of driver events in metastatic uveal melanoma

Metastatic uveal melanoma is less well understood than its primary counterpart, has a distinct biology compared to skin melanoma, and lacks effective treatments. Here we genomically profile metastatic tumors and infiltrating lymphocytes. BAP1 alterations are overrepresented and found in 29/32 of cases. Reintroducing a functional BAP1 allele into a deficient patient-derived cell line, reveals a broad shift towards a transcriptomic subtype previously associated with better prognosis of the primary disease. One outlier tumor has a high mutational burden associated with UV-damage. CDKN2A deletions also occur, which are rarely present in primaries. A focused knockdown screen is used to investigate overexpressed genes associated withcopy number gains. Tumor-infiltrating lymphocytes are in several cases found tumor-reactive, but expression of the immune checkpoint receptors TIM-3, TIGIT and LAG3 is also abundant. This study represents the largest whole-genome analysis of uveal melanoma to date, and presents an updated view of the metastatic disease.

Ipilimumab in pretreated patients with metastatic uveal melanoma: safety and clinical efficacy

Current systemic treatments for metastatic uveal melanoma (UM) have not improved overall survival (OS). The fully human anti-cytotoxic T-lymphocyte antigen-4 (CTLA-4) monoclonal antibody, ipilimumab, improved OS of patients with advanced cutaneous melanoma in a phase 3 trial; however, UM patients were excluded. The aim of this subanalysis, performed by the ipilimumab-ocular melanoma expanded access program (I-OMEAP) study group, was to assess the activity and safety of ipilimumab in patients with UM in a setting similar to daily clinical practice. Patients participating in a multicenter expanded access program (EAP) received induction treatment with ipilimumab 10 mg/kg. Maintenance doses were administered in patients who experienced clinical benefit or at physicians' discretion. Tumor assessment was evaluated per modified World Health Organization criteria at baseline, Week 12, Week 24, and Week 36. Adverse events (AEs) and immune-related AEs (irAEs) were collected according to Common Terminology Criteria for Adverse Events version 3.0. Thirteen pretreated patients with metastatic UM were treated at 6 European institutions. All patients received at least one dose of ipilimumab. Overall, no objective responses were observed; however, two patients had stable disease (SD), with a third patient achieving SD after initial progressive disease. Median OS as of July 1, 2011, was 36 weeks (range 2-172+ weeks). No grade 3/4 AEs of non-immune origin were reported. Three patients (23%) experienced grade 3 irAEs (1 thrombocytopenia, 1 diarrhea, and 1 alanine/aspartate aminotransferase elevation) that resolved with steroid therapy. The results indicate UM is a potential indication for ipilimumab treatment that should be further investigated in clinical trials.

Human uveal melanoma cells produce macrophage migration-inhibitory factor to prevent lysis by NK cells

Human uveal melanoma arises in an immune privileged ocular environment in which both adaptive and innate immune effector mechanisms are suppressed. Uveal melanoma is the most common intraocular tumor in adults and is derived from tissues in the eye that produce macrophage migration-inhibitory factor (MIF), a cytokine that has recently been demonstrated to produce immediate inhibition of NK cell-mediated lytic activity. Although NK cell-mediated lysis of uveal melanomas is inhibited in the eye, melanoma cells that disseminate from the eye are at risk for surveillance by NK cells. Moreover, uveal melanoma cells demonstrate a propensity to metastasize to the liver, an organ with one of the highest levels of NK activity in the body. Therefore, we speculated that uveal melanomas produced MIF as a means of escaping NK cell-mediated lysis. Accordingly, seven primary uveal melanoma cell lines and two cell lines derived from uveal melanoma metastases were examined for their production of MIF. MIF was detected in melanoma culture supernatants by both ELISA and the classical bioassay of macrophage migration inhibition. Melanoma-derived MIF inhibited NK cell-mediated lysis of YAC-1 and uveal melanoma cells. Cell lines derived from uveal melanoma metastases produced approximately twice as much biologically active MIF as cultures from primary uveal melanomas. Inhibition of NK cell-mediated killing by uveal melanoma-derived MIF was specifically inhibited in a dose-dependent manner by anti-MIF Ab. The results suggest that human uveal melanoma cells maintain a microenvironment of immune privilege by secreting active MIF that protects against NK cell-mediated killing.

HER2 CAR-T Cells Eradicate Uveal Melanoma and T-cell Therapy-Resistant Human Melanoma in IL2 Transgenic NOD/SCID IL2 Receptor Knockout Mice

Chimeric antigen receptors (CAR) can transmit signals akin to those from activated T-cell receptors when bound to a cell surface target. CAR-expressing T cells against CD19 can cause curative effects in leukemia and lymphoma and is approved for clinical use. However, no CAR-T therapy is currently approved for use in solid tumors. We hypothesize that the resistance of solid tumors to CAR-T can be overcome by similar means as those used to reactivate tumor-infiltrating T lymphocytes (TIL), for example, by cytokines or immune checkpoint blockade. Here we demonstrate that CAR-T cells directed against HER2 can kill uveal and cutaneous melanoma cells in vitro and in vivo. Curative effects in vivo were only observed in xenografts grown in a NOD/SCID IL2 receptor gamma (NOG) knockout mouse strain transgenic for human IL2. The effect was target-specific, as CRISPR/Cas9-mediated disruption of HER2 in the melanoma cells abrogated the killing effect of the CAR-T cells. The CAR-T cells were also able to kill melanoma cells from patients resistant to adoptive T-cell transfer (ACT) of autologous TILs. Thus, CAR-T therapy represents an option for patients that do not respond to immunotherapy with ACT of TIL or immune checkpoint blockade. In addition, our data highlight the use of IL2 transgenic NOG mice as models to prove efficacy of CAR-T-cell products, possibly even in a personalized manner. SIGNIFICANCE: These findings demonstrate that a novel humanized mouse model can help clinical translation of CAR-T cells against uveal and cutaneous melanoma that do not respond to TIL therapy or immune checkpoint blockade.

Re-evaluation of "reactive lymphoid hyperplasia of the uvea": an immunohistochemical and molecular analysis of 10 cases

OBJECTIVE

Cases of uveal lymphoid proliferation previously classified as reactive lymphoid hyperplasia (RLH) were studied to correlate pathologic features with clinical outcome.

DESIGN

Retrospective case series.

PARTICIPANTS

Ten cases of RLH of the uvea on file at the Armed Forces Institute of Pathology with sufficient formalin-fixed, paraffin-embedded tissue for analysis.

METHODS

Clinical, histologic, immunohistochemical, and molecular (polymerase chain reaction [PCR]) characteristics of uveal lymphoid proliferations were studied.

MAIN OUTCOME MEASURES

Morphologic, immunohistochemical, and PCR characteristics of study cases.

RESULTS

Patient age ranged from 40 to 73 years at time of enucleation, with a mean age of 55 years. Retinal detachment was noted clinically in nine patients and glaucoma in eight. All patients were treated with enucleation, and three received radiotherapy. Histologically, two cases were interpreted as RLH and eight were well-differentiated small-cell lymphoma (WDSCL). Systemic lymphoid infiltrate developed in two patients, but there were no deaths with a mean follow-up of 9.9 years. Mature lymphocytes were noted in the iris and angle structures; the atypical cells of uveal lymphoma were found in the choroid and ciliary body. Eight cases were monoclonal by B-cell and T-cell markers and/or immunoglobulin light chain restriction. Amplifiable DNA was present in 6 of 10 cases by PCR. Three cases monoclonal by cell markers were also monoclonal by PCR, but two cases monoclonal by cell markers could not be confirmed by PCR. Lymphoid follicles with germinal centers were found in two cases of RLH and five cases of WDSCL. Nine specimens demonstrated extraocular lymphoid involvement of the episclera and orbit; most appeared more benign morphologically than the choroidal infiltrates. Extraocular infiltrates of WDSCL were monoclonal by immunohistochemistry in five cases, polyclonal in one case, and indeterminate in two cases.

CONCLUSIONS

Most cases (8 of 10) previously described as RLH were low-grade B-cell lymphomas histologically and by immunohistochemistry. PCR results agreed with histologic diagnosis in four of six cases. Open-angle glaucoma was common and related mostly to lymphocytic infiltration of the angle structures. Extraocular involvement is common but may not be representative of the choroidal lesion. Prognosis is excellent in low-grade uveal lymphoid neoplasia.

Immune escape mechanisms of intraocular tumors

The notion that the immune system might control the growth of tumors was suggested over 100 years ago by the eminent microbiologist Paul Ehrlich. This concept was refined and expanded by Burnet and Thomas 50 years later with their articulation of the "immune surveillance" hypothesis. In its simplest form, the immune surveillance hypothesis suggests that neoplasms arise spontaneously and express novel antigens that are recognized by the immune system, which either eliminates the tumors or restrains their growth. Within the eye, immune responses are controlled and sometimes profoundly inhibited - a condition known as immune privilege. Immune privilege in the eye is the result of a complex array of anatomical, physiological, and immunoregulatory mechanisms that prevent the induction and expression of many immune responses. Tumors arising in the eye would seem to have an advantage in evading immune surveillance due to ocular immune privilege. Uveal melanoma, the most common and malignant intraocular tumor in adults, not only benefits from the immune privilege of the eye but also has adopted many of the mechanisms that contribute to ocular immune privilege as a strategy for protecting uveal melanoma cells once they leave the sanctuary of the eye and are disseminated systemically in the form of metastases. Although the immune system possesses a battery of effector mechanisms designed to rid the body of neoplasms, tumors are capable of rapidly evolving and countering even the most sophisticated immunological effector mechanisms. To date, tumors seem to be winning this arms race, but an increased understanding of these mechanisms should provide insights for designing immunotherapy that was envisioned over half a century ago, but has failed to materialize to date.

HLA expression in uveal melanoma: there is no rule without some exception

A decrease in the expression of HLA antigens is considered a characteristic of tumor progression and is considered an important tumor-escape mechanism. In general, HLA Class I expression is even further decreased on metastases. Tumor cells that loose their HLA Class I antigens become less susceptible to lysis by specific T cells, but may become more sensitive to Natural Killer cells. Loss of HLA Class I can be observed at different levels, i.e. total loss of Class I, loss of expression of one locus or one haplotype, or even one specific allele. We studied HLA expression on human uveal melanoma and observed that loss of expression of a locus or one or more alleles is a common phenomenon. However, in contrast with the commonly accepted paradigm, loss of HLA Class I expression on the uveal melanoma was not associated with tumor cell escape and a worse survival, but with a better survival of the patients involved. We hypothesize that this is due to the route of metastases formation: in uveal melanoma, spreading of metastases is purely hematogeneous, and it is quite possible that NK-cell mediated surveillance of tumor cells in the blood is the underlying mechanism. This is supported by our finding that metastases of uveal melanoma have a high HLA Class I expression, leading to our conclusion that uveal melanoma is an exception to the general rule regarding HLA Class I expression in tumor immunology.

alpha-Melanocyte stimulating hormone, inflammation and human melanoma

Alpha-melanocyte stimulating hormone (alpha-MSH) arises from the proteolytic cleavage of proopiomelanocortin (POMC) and is the most potent naturally occurring melanotropic peptide. The biological effects of alpha-MSH are mediated via melanocortin receptors (MCRs), which are expressed in virtually every cutaneous cell type. alpha-MSH has pleiotrophic functions including the modulation of a wide range of inflammatory stimuli such as proinflammatory cytokines, adhesion molecules and inflammatory transcription factors. All of the former would be consistent with a cytoprotective role for this hormone in protecting skin cells from exogenous stress, as would occur following UV exposure or exposure to agents inducing inflammation or oxidative stress. In addition to actions on normal skin cells it also modulates both cutaneous and uveal melanoma cell behavior. With respect to melanoma, alpha-MSH is intriguing as studies have shown that while alpha-MSH has the potential to retard metastatic spread (by reducing cell migration and invasion) it is also capable of reducing the ability of the immune system to detect tumor cells (by down regulating adhesion molecules that would normally assist in immune cell interaction with melanoma cells). This review considers the evolving biology of alpha-MSH and discusses its role in man that extend far beyond pigmentation of skin melanocytes, suggesting that the detoxifying role of alpha-MSH in inducing melanogenesis is only one aspect of the stress-coping role of this hormone. Indeed melanoma cells may owe at least some of their success to the 'protective' role of alpha-MSH.

HLA expression and tumor-infiltrating immune cells in uveal melanoma

BACKGROUND

In uveal melanoma, both the amount of tumor-infiltrating cells and the level of expression of HLA antigens are quite variable. We hypothesized that low levels of HLA expression lead to a lack of antigen presentation, which might prevent proper immunologic recognition of the tumor. This lack of recognition might subsequently lead to low levels of tumor-infiltrating cells.

METHODS

To test this hypothesis, we determined the type and number of tumor-infiltrating cells in tumor sections from 24 uveal melanomas. We applied monoclonal antibodies directed against different types of immune cells and compared the results with the expression of HLA class I and class II antigens on the tumor cells.

RESULTS

Infiltrating immune cells were observed in all uveal melanomas (although in small amounts), with a predominance of T lymphocytes. Significant positive correlations were observed between the number of CD3+ cells (T lymphocytes) and monomorphic HLA class I expression, allele-specific HLA-A2 and Bw4 expression, and HLA class II expression. Furthermore, the number of CD4+ cells (T helper cells, monocytes/ macrophages) and of CD11b+ cells (monocytes/macrophages) was significantly correlated with the level of monomorphic HLA class I expression.

CONCLUSION

These data support our hypothesis that low levels of HLA expression (and therefore a lack of presentation of tumor-specific antigens) may lead to a low level of tumor infiltrate.

Identification of an Immunogenic Subset of Metastatic Uveal Melanoma

PURPOSE

Uveal melanoma is a rare melanoma variant with no effective therapies once metastases develop. Although durable cancer regression can be achieved in metastatic cutaneous melanoma with immunotherapies that augment naturally existing antitumor T-cell responses, the role of these treatments for metastatic uveal melanoma remains unclear. We sought to define the relative immunogenicity of these two melanoma variants and determine whether endogenous antitumor immune responses exist against uveal melanoma.

EXPERIMENTAL DESIGN

We surgically procured liver metastases from uveal melanoma (n = 16) and cutaneous melanoma (n = 35) patients and compared the attributes of their respective tumor cell populations and their infiltrating T cells (TIL) using clinical radiology, histopathology, immune assays, and whole-exomic sequencing.

RESULTS

Despite having common melanocytic lineage, uveal melanoma and cutaneous melanoma metastases differed in their melanin content, tumor differentiation antigen expression, and somatic mutational profile. Immunologic analysis of TIL cultures expanded from these divergent forms of melanoma revealed cutaneous melanoma TIL were predominantly composed of CD8(+) T cells, whereas uveal melanoma TIL were CD4(+) dominant. Reactivity against autologous tumor was significantly greater in cutaneous melanoma TIL compared with uveal melanoma TIL. However, we identified TIL from a subset of uveal melanoma patients which had robust antitumor reactivity comparable in magnitude with cutaneous melanoma TIL. Interestingly, the absence of melanin pigmentation in the parental tumor strongly correlated with the generation of highly reactive uveal melanoma TIL.

CONCLUSIONS

The discovery of this immunogenic group of uveal melanoma metastases should prompt clinical efforts to determine whether patients who harbor these unique tumors can benefit from immunotherapies that exploit endogenous antitumor T-cell populations. Clin Cancer Res; 22(9); 2237-49. ©2015 AACR.

Autocrine secretion of Fas ligand shields tumor cells from Fas-mediated killing by cytotoxic lymphocytes

Mechanisms responsible for resistance of tumors to death receptor-mediated damage by cytotoxic lymphocytes are not well understood. Uveal melanoma cells expressed Fas but were insensitive to Fas triggering induced by bystander cytotoxic T lymphocytes or a Fas-specific agonistic antibody; this could not be ascribed to tumor counterattack against T cells or general resistance of the tumors to apoptosis. Treatment with inhibitors of metalloproteases rendered uveal melanomas sensitive to Fas-mediated cytotoxicity. Metalloprotease inhibitors did not affect the expression of Fas but increased the surface expression of Fas ligand (FasL), which correlated with the disappearance of soluble FasL from culture supernatants of tumor cells. FasL eluted from the surface of uveal melanomas specifically inhibited cytotoxic T lymphocyte lysis of tumor cells pretreated with an inhibitor of metalloproteases. In addition to uveal melanomas, a number of other tumor cell lines of various cellular origins were sensitized to Fas-mediated cytotoxicity by metalloprotease inhibitors. Our results show that autocrine secretion of FasL shields tumor cells from Fas-mediated killing by cytotoxic lymphocytes. This defines a novel mechanism of tumor escape from immune surveillance.

Immunotherapy for the Treatment of Uveal Melanoma: Current Status and Emerging Therapies

PURPOSE OF REVIEW

Uveal melanoma is a distinct subset of melanoma with a biology and treatment approach that is unique from that of cutaneous melanoma. Here we will review the current data evaluating immunotherapies in both the adjuvant and metastatic settings in uveal melanoma.

RECENT FINDINGS

In the adjuvant setting, interferon demonstrated no survival benefit in uveal melanoma, and studies evaluating immune-based strategies such as vaccine therapy are ongoing. Anti-CTLA-4 and anti-PD-1/ PD-L1 blockade in uveal melanoma have been evaluated in several small prospective and/or retrospective studies with rare responses and no overall survival benefit demonstrated. Ongoing studies evaluating combination checkpoint inhibition and other antibody-based therapies are ongoing. Although immunotherapy with anti-CTLA-4 and anti-PD-1 agents has dramatically changed the treatment approach to cutaneous melanoma, its success in uveal melanoma has been much more limited. Clinical trial participation should be prioritized in patients with uveal melanoma.

Uveal melanoma: the inflammatory microenvironment

Uveal melanoma is a highly malignant intraocular tumor with quite homogeneous tumor tissue and a diffuse leukocytic infiltration. In contrast with many other malignancies, the presence of infiltrating macrophages and T cells is associated with a poor prognosis rather than a good one. The clear link between inflammation and cancer in this malignancy provides a paradigm for macrophage plasticity and function. Macrophages in uveal melanoma have an M2-like phenotype and are associated with the loss of one specific chromosome - monosomy 3. The central players involved in this process and discussed in this review include macrophages, T lymphocytes, chemokines and cytokines, including the macrophage-attraction molecules. When a tumor acquires the ability to release significant amounts of macrophage-attraction molecules it causes the expansion of a population of myeloid immature cells that may not only help the tumor to suppress immune reactions but also aid in the construction of new blood vessels for tumor growth. A better understanding of the molecular basis of a local myelomonocytic cell population will bring a better understanding of the immunopathology of this disease and will lead to therapeutic interventions in uveal melanoma. This review focuses on the roles of the local inflammatory microenvironment in the development and progression of uveal melanoma.

The Role of Immune Checkpoint Blockade in Uveal Melanoma

Uveal melanoma (UM) represents the most common intraocular malignancy in adults and accounts for about 5% of all melanomas. Primary disease can be effectively controlled by several local therapy options, but UM has a high potential for metastatic spread, especially to the liver. Despite its clinical and genetic heterogeneity, therapy of metastatic UM has largely been adopted from cutaneous melanoma (CM) with discouraging results until now. The introduction of antibodies targeting CTLA-4 and PD-1 for immune checkpoint blockade (ICB) has revolutionized the field of cancer therapy and has achieved pioneering results in metastatic CM. Thus, expectations were high that patients with metastatic UM would also benefit from these new therapy options. This review provides a comprehensive and up-to-date overview on the role of ICB in UM. We give a summary of UM biology, its clinical features, and how it differs from CM. The results of several studies that have been investigating ICB in metastatic UM are presented. We discuss possible reasons for the lack of efficacy of ICB in UM compared to CM, highlight the pitfalls of ICB in this cancer entity, and explain why other immune-modulating therapies could still be an option for future UM therapies.

Inflammatory cell infiltrates in advanced metastatic uveal melanoma

Current treatments for metastatic uveal melanoma (mUM) are limited and rarely prolong patient survival. Immunotherapy trials for mUM are few and to date have demonstrated only marginal success. High densities of tumor-associated macrophages (TAMs) and infiltrating T lymphocytes (TILs) in primary UM are associated with poor prognosis. Little is known about the immune microenvironment of mUM. Our aim was to examine the presence and distribution of TAMs and TILs in mUM within the liver. Whole-tissue sections of liver mUM (n=35) were examined by immunohistochemistry. For TAMs, monoclonal antibodies against CD68 and CD163 were used. Macrophage density and morphology were scored using previous established systems. Density and spatial distribution of TILs were highlighted using antibodies against CD3 (pan-lymphocyte marker), CD4 (T-helper cells), and CD8 (T-cytotoxic cells). CD68+ and CD163+ TAMs were seen within the tumor in all 35 specimens; their density was "moderate" in 50% of cases and "few" in 43%, and the majority showed an "indeterminate" phenotype. CD3+ TILs were noted both within mUMs and surrounding the tumor. Of these, CD8+ TILs were "few" in number within mUM but were predominantly seen peritumorally at the tumor/normal liver interface, whereas CD4+ TILs showed a high perivascular density within mUM. CD68+ and CD163+ TAMs of "indeterminate" morphology were observed in mUM, suggesting a tendency toward the protumorigenic M2 phenotype. CD4+ TILs were seen within the mUM, whereas CD8+ TILs tended to be peritumoral. The biological and functional roles of inflammatory cells in mUM require further investigation to determine if they represent potential targets for future therapies in mUM.

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

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

Uveal melanoma expression of indoleamine 2,3-deoxygenase: establishment of an immune privileged environment by tryptophan depletion

The enzyme indoleamine 2,3-dioxygenase (IDO) catalyzes degradation of tryptophan, an essential amino acid required for lymphocyte activation and proliferation. Many tumors express IDO which implies that it acts as a mechanism to evade T cell-mediated immune attack, and also to establish an immunosuppressive tumor microenvironment. The purpose of this study was to determine whether primary and metastatic uveal melanoma expressed the IDO gene and whether uveal melanoma cells could deplete tryptophan. In situ expression of IDO in primary uveal melanoma from tumor bearing eyes and metastatic uveal melanoma liver tissues was determined by immunohistostaining with IDO-specific antibody. Reverse transcription PCR was used to assess IDO gene transcription by primary and metastatic uveal melanoma cell lines. IDO protein expression was determined by Western blot of uveal melanoma cell protein lysate. IDO catalytic activity was assessed by measuring the presence of kynurenine, a product generated by tryptophan degradation, in uveal melanoma culture supernatants. Primary uveal melanoma from tumor-bearing eyes and metastatic uveal melanoma from the liver did not express IDO in situ. IDO was not constitutively expressed in either primary or metastatic uveal melanoma cell lines. However, stimulation of primary and metastatic uveal melanoma cell cultures with interferon-gamma (IFN-gamma) universally upregulated both IDO gene and protein expression. Culture supernatants from IFN-gamma treated primary and metastatic uveal melanoma cell cultures contained elevated levels of kynurenine. Addition of the IDO inhibitor 1-methyl dl-tryptophan significantly diminished kynurenine levels in IFN-gamma treated uveal melanoma cell cultures. The results from this study suggest that IFN-gamma inducible IDO upregulation by primary and metastatic uveal melanoma may generate a local immune privileged microenvironment to promote escape from T cell-mediated immune surveillance.

Ocular involvement by a peripheral T-cell lymphoma

Non-Hodgkin's lymphomas can simulate uveitis. Two patients with non-Hodgkin's lymphoma had anterior uveitis. Material was obtained from the enucleated eye in case 1, and from an inguinal lymph node in case 2. Immunologic evaluation of this material led to the diagnosis of peripheral T-cell lymphoma in both cases. Immunologic evaluation is useful in the examination of patients with lymphoma.

TGF-beta in uveal melanoma

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

Ki-67 immunostaining in uveal melanoma. The effect of pre-enucleation radiotherapy

The reactivity of 33 choroidal and ciliary body melanomas with monoclonal antibody Ki-67, which recognizes a proliferation associated nuclear antigen, has been assessed and compared with clinicopathologic parameters. In 23 cases, 8 Gy irradiation was given 2 days before enucleation. Nonirradiated melanomas had a significantly higher proliferation rate as defined by staining with monoclonal antibody Ki-67 as compared with irradiated tumors (P = 0.007). Similarly, a strong relationship was found between pre-enucleation irradiation and low mitotic activity (P = 0.001). There was no significant correlation between the presence of Ki-67-positive nuclei and histologic classification, largest tumor diameter, localization of the tumor, age, sex, scleral invasion, pigmentation, and lymphocytic infiltration. The relevance of Ki-67 immunohistochemistry for the assessment of the life prognosis of patients with uveal melanoma has to be studied prospectively.

Antibody to Toxocara canis in the aqueous humor

The aqueous humor and serum samples of patients with presumed ocular toxocariasis were examined by an enzyme-linked immunosorbent assay (ELISA) for antibody to the embryonated egg antigen. Using a single dilution (1:8), higher amounts of antibody have been found in the aqueous humor than in the serum samples. Antibody was not found in the serum or aqueous humor of patients with retinoblastoma, Coats' disease, uveal malignant melanoma, or central retinal artery obstruction. While two patients with presumed ocular toxocariasis had normal serum levels of antibody, the aqueous humor ELISA titers were greatly elevated, supporting the clinical diagnosis and suggesting localized antibody production.