Expression of Fas and Fas ligand in uveal melanoma: biological implication and prognostic value

Defective FasL expression is associated with increased resistance to melanoma liver metastases and enhanced natural killer cell activity

The objective was to determine if the absence of FasL signaling would affect melanoma liver metastases by influencing the antimelanoma properties of liver natural killer (NK) cells. Melanoma liver metastases were induced in wild-type C57BL/6 mice and the gld/gld mutant C57BL/6 mouse strain that expresses a defective form of FasL (CD95L) that fails to engage and signal via the Fas receptor (CD95). Liver metastases were produced by intrasplenic injection of B16LS9 melanoma cells. Liver NK cell activity directed against murine B16LS9 melanoma cells was determined in a 24 h in-vitro cytotoxicity assay. Liver NK cells, NK T cells, and the NK cell surface activation marker, NKG2D, were measured by flow cytometry. Mice expressing defective FasL displayed reduced, rather than enhanced, melanoma liver metastases that coincided with increased liver NK cell-mediated tumor cell cytotoxicity. Enhanced cytotoxicity was not mediated by perforin, tumor necrosis factor-α, or tumor necrosis-associated apoptosis-inducing ligand but was closely associated with elevated interferon-γ in the tumor-bearing liver. FasL-defective gld/gld mice also displayed reduced numbers of liver NK T cells, which have been previously implicated in suppression on liver NK cell activity. The absence of functional FasL in the liver correlates with a heightened, not diminished, resistance to melanoma liver metastases. The resistance to liver metastases coincides with a significant, albeit transient, increase in liver NK cytotoxicity and elevated levels of interferon-γ in the liver.

Immunobiology of Uveal Melanoma: State of the Art and Therapeutic Targets

Uveal Melanoma (UM) represents the most common primary intraocular malignant tumor in adults. Although it originates from melanocytes as cutaneous melanoma, it shows significant clinical and biological differences with the latter, including high resistance to immune therapy. Indeed, UM can evade immune surveillance via multiple mechanisms, such as the expression of inhibitory checkpoints (e.g., PD-L1, CD47, CD200) and the production of IDO-1 and soluble FasL, among others. More in-depth understanding of these mechanisms will suggest potential targets for the design of novel and more effective management strategies for UM patients.

Immunological Backbone of Uveal Melanoma: Is There a Rationale for Immunotherapy?

No standard treatment has been established for metastatic uveal melanoma (mUM). Immunotherapy is commonly used for this disease even though UM has not been included in phase III clinical trials with checkpoint inhibitors. Unfortunately, only a minority of patients obtain a clinical benefit with immunotherapy. The immunological features of mUM were reviewed in order to understand if immunotherapy could still play a role for this disease.

DNA alteration-based classification of uveal melanoma gives better prognostic stratification than immune infiltration, which has a neutral effect in high-risk group

Background

In uveal melanomas, immune infiltration is a marker of poor prognosis. This work intended to decipher the biological characteristics of intra‐tumor immune population, compare it to other established biomarkers and to patients' outcome.

Methods

Primary, untreated, and mainly large uveal melanomas with retinal detachment were analyzed using: transcriptomic profiling (n = 15), RT‐qPCR (n = 36), immunohistochemistry (n = 89), Multiplex Ligation‐dependent Probe Amplification (MLPA) for copy number alterations (CNA) analysis (n = 89), array‐CGH (n = 17), and survival statistics (n = 86).

Results

Gene expression analysis divided uveal melanomas into two groups, according to the IFNγ/STAT1‐IRF1 pathway activation. Tumors with IFNγ‐signature had poorer prognosis and showed increased infiltration of CD8⁺ T lymphocytes and macrophages. Cox multivariate analyses of immune cell infiltration with MLPA data delineated better prognostic value for three prognostic groups (three‐tier stratification) than two (two‐tier stratification). CNA‐based model comprising monosomy 3, 8q amplification, and LZTS1and NBL1 deletions emerged as the best predictor for disease‐free survival. It outperformed immune cell infiltration in receiver operating characteristic curves. The model that combined CNA and immune infiltration defined risk‐groups according to the number of DNA alterations. Immune cell infiltration was increased in the high‐risk group (73.7%), where it did not correlate with patient survival, while it was associated with poorer outcome in the intermediate risk‐group.

Conclusions

High degree of immune cell infiltration occurs in a subset of uveal melanomas, is interferon‐gamma‐related, and associated with poor survival. It allows for two‐tier stratification, which is prognostically less efficient than a three‐tier one. The best prognostic stratification is by CNA model with three risk‐groups where immune cell infiltration impacts only some subgroups.

Tumor Infiltrating Lymphocytes in Uveal Melanoma: A Link with Clinical Behavior?

Experimental and clinical evidence indicate that immunological mechanisms might be important in the clinical course of uveal malignant melanoma (UMM). We analyzed the amount and phenotype of tumor infiltrating lymphocytes (TIL) and the expression of the apoptosis-inducing molecule Fas and its ligand, FasL, on tumor cells and TIL in a selected series of UMM with the aim to establish if a correlation between their expression and the clinical behavior of UMM exists. TIL phenotype and Fas/FasL expression were evaluated by immunohistochemistry in 61 cases of formalin-fixed, paraffin-embedded UMM. Results were compared with the follow-up data of patients. Most of the UMM showed a prevalence of CD8+ CD3+ T lymphocytes, or CD4+ and CD8+ cells in equal amounts. UMM showed a variable expression of FasL, ranging from 0 to > 40% of neoplastic cells. Fas was always expressed in TIL, although with a variable extent. A subgroup of UMM showed in TIL a strongly reduced or even absent expression of TCR ζ-chain, involved in activation of T-lymphocytes. This subgroup was characterized by a worse outcome. We hypothesized that an impaired cytotoxic immune response due to the loss of the ζ-chain expression plays a primary role in the biological course of UMM. Our results indicate that the overcoming of the impairment of TCR function may represent a prerequisite for the development of new therapeutic strategies for managing UMM, suggesting that elimination of tumor cells may be possible by activation of cytotoxic cells present within ocular melanomas.

Obstacles to improving outcomes in the treatment of uveal melanoma

The rate of advances in uveal melanoma has not kept pace with the rate of advances in cutaneous melanoma. Many patients lack access to or knowledge of specialty centers, and integrated multidisciplinary care between ophthalmology, radiation oncology, and medical oncology is far from the norm. This treatment isolation leads to limited communication about novel clinical trial opportunities. Clinical trials themselves are not widely available, and a lack of robust funding limits rapid and complete investigations. This review outlines the obstacles to success in uveal melanoma management and highlights strategies for overcoming these challenges. Cancer 2018;124:2693-2703. © 2018 American Cancer Society.

Molecular profiling of primary uveal melanomas with tumor-infiltrating lymphocytes

In contrast to other cancers, the presence of tumor-infiltrating lymphocytes (TILs) in uveal melanoma is associated with a poor prognosis. However, how TILs may promote disease progression and what regulates their infiltration has not yet been established. To address these clinically relevant outstanding questions, T cell, immune regulatory, and chemokine gene expression profiles of 57 enucleated uveal melanoma tumors were compared, encompassing 27 with TILs and 30 without,. Tumors with infiltrating lymphocytes expressed more CD8A mRNA, as well as IFNG, TGFB1, and FOXP3 transcripts. Other T helper associated cytokines and T helper transcription factors were not differentially expressed, nor were mediators of lymphocyte cytotoxicity. The immune inhibitors INDO, PDCA1, CTLA4, and LAG3, and the non-classical MHC Class I target of CD8⁺ T regulatory cells, HLA‑E, were significantly higher in tumors with TILs. FAS was also significantly higher. The C-C chemokine ligands CCL4, CCL5, and CCL20 were higher in tumors with TILs. Levels of CCL5 were most strongly correlated with levels of CD8A. Chemokine receptors were not differentially expressed. Molecular profiling of uveal melanoma tumors with TILs supports the existence of an immunosuppressive tumor microenvironment and suggests roles for CD8⁺ regulatory T cells, as well as specific chemokines, in fostering uveal melanoma disease progression.

Molecular pathology of uveal melanoma

Like other cancers, uveal melanomas (UM) are characterised by an uncontrolled, clonal, cellular proliferation, occurring as a result of numerous genetic, and epigenetic aberrations. Signalling pathways known to be disrupted in UM include: (1) the retinoblastoma pathway, probably as a result of cyclin D1 overexpression; p53 signalling, possibly as a consequence of MDM2 overexpression; and the P13K/AKT and mitogen-activated protein kinase/extracellular signal-related kinase pathway pathways that are disturbed as a result of PTEN and GNAQ/11 mutations, respectively. Characteristic chromosomal abnormalities are common and include 6p gain, associated with a good prognosis, as well as 1p loss, 3 loss, and 8q gain, which correlate with high mortality. These are identified by techniques such as fluorescence in situ hybridisation, comparative genomic hybridisation, microsatellite analysis, multiplex ligation-dependent probe amplification, and single-nucleotide polymorphisms. UM can also be categorised by their gene expression profiles as class 1 or class 2, the latter correlating with poor survival, as do BRCA1-associated protein-1 (BAP1) inactivating mutations. Genetic testing of UM has enhanced prognostication, especially when results are integrated with histological and clinical data. The identification of abnormal signalling pathways, genes and proteins in UM opens the way for target-based therapies, improving prospects for conserving vision and prolonging life.

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.

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.

Immunohistochemical characteristics of melanoma

Melanoma has a wide spectrum of histologic features which mimic epithelial, hematologic, mesenchymal, and neural tumors. Immunohistochemistry has been the primary tool to distinguish melanomas from these other tumors; it has also been studied for use as an adjunct to distinguish benign and malignant melanocytic tumors and to elucidate prognosis. Furthermore, there has been extensive effort to find a suitable marker to differentiate spindle cell and desmoplastic melanoma from other tumors. We have reviewed the literature investigating melanocytic differentiation markers, proliferation markers, immunomodulatory markers, signaling molecules, and nerve growth factors and receptors. Despite the proliferation of immunohistochemical markers, S-100 remains the most sensitive marker for melanocytic lesions, while markers such as HMB-45, MART-1/Melan-A, tyrosinase, and MITF demonstrate relatively good specificity but not as good sensitivity as S-100. No marker has proven useful in distinguishing spindle cell and desmoplastic melanomas from other tumors. Ki67 remains the most useful adjunct in distinguishing benign from malignant melanocytic tumors. None of the markers reviewed has been shown conclusively to have prognostic value for melanocytic neoplasms.

Proteomics in uveal melanoma research: opportunities and challenges in biomarker discovery

Uveal melanoma (UM) is the most frequent primary intraocular tumor in adult humans. Despite the significant advances in diagnosis and treatment of UM in the last decades, the prognosis of UM sufferers is still poor. Metastatic liver disease is the leading cause of death in UM and can develop after a long disease-free interval, suggesting the presence of occult micrometastasis. Proteomics technology has opened new opportunities for elucidating the molecular mechanism of complex diseases, such as cancer. This article will review the recent developments in biomarker discovery for UM research by proteomics. In the last few years, the first UM proteomics-based analyses have been launched, yielding promising results. An update on recent developments on this field is presented.

Expression of Fas ligand (CD95L) in primary malignant melanoma and melanoma metastases is associated with overall survival

BACKGROUND

There is increasing evidence that the Fas/Fas ligand (FasL) system is involved in tumor-mediated immune suppression. The purpose of this study was to investigate the effect of Fas (CD95) as well as FasL (CD95L) expression in primary malignant melanoma and melanoma metastases on overall survival (OS).

PATIENTS AND METHODS

19 patients with metastatic malignant melanoma who were treated with different dacarbazine (DTIC)-based chemotherapy regimens were included in this study. From each patient, primary melanoma biopsies and biopsies from metastases were histologically evaluated. Immunohistology was performed with antibodies to Fas/CD95 and FasL/CD95L. Differences in OS were plotted using the Kaplan-Meier method and compared by the log rank test.

RESULTS

Fas/CD95 and FasL/CD95L expression was detected in 73.7 and 63.2% of primary melanomas, respectively. In metastases, expression of both Fas/CD95 (63.2%) and FasL/CD95L (47.4%) was markedly decreased. Presence of FasL/ CD95L expression in primary melanoma resulted in significantly (p = 0.024) prolonged OS compared with FasL/CD95L-negative high-risk primary melanomas. In contrast, loss of FasL/CD95L expression in melanoma metastases resected before chemotherapy was associated with significantly prolonged median survival (p = 0.0139).

CONCLUSION

Presence of FasL/CD95L expression in primary malignant melanoma and the loss of FasL/ CD95L expression in metastases seem to be positive prognostic factors.

Apoptosis inhibitor, survivin, in posterior uveal melanoma: comparison among primary tumors, tumors resistant to brachytherapy, tumors with liver metastases, and liver metastases

PURPOSE

To study the expression of survivin, an apoptosis inhibitor protein, in human posterior uveal melanoma.

METHODS

Specimens were divided according to eyes with tumors that were enucleated primarily, those resistant to brachytherapy, eyes from patients with known liver metastases, and liver metastases.

RESULTS

There was only low expression of survivin in uveal melanoma. No difference in survivin positive cell counts per high power field (PCC/HPF) were found among tumors that were enucleated primarily (n = 33), tumors with previous brachytherapy (n = 29), tumors with liver metastases (n = 12) or liver metastases (n = 18). Corresponding counts were 11.8 (+/-14.3), 11.8 (+/-16.8), 7.1 (+/-11.2), and 4.7 (+/-8.8) in the four groups, respectively (p > 0.05). Half of the liver metastases showed no staining for survivin. Twenty patients (24%) had tumor-related death at the end of follow-up.

CONCLUSIONS

Survivin is expressed in posterior uveal melanomas that were treated by enucleation, as well as in tumors that were previously treated with brachytherapy or liver metastases; however, its expression by immunostaining did not seem with correlate with the tumor biological activity.

Expression of cell adhesion molecules and tumour infiltrating leucocytes in conjunctival melanoma

AIM

Very little is known about the immunology of conjunctival melanoma. We investigated the expression of cell adhesion molecules and the grade of tumour infiltration with lymphocytes and macrophages as important members for the communication between tumour cells and the immune system.

METHODS

Archival material from 35 conjunctival melanomas was used for immunohistochemical detection of intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), neural cell adhesion molecule (NCAM), CD3 and CD68 using monoclonal antibodies. Histological and clinical data for these tumours were assessed.

RESULTS

ICAM-1 was expressed in 34 of 35 tumours; in 20 cases, more than 50% of the cells stained ICAM-1 positive. VCAM-1 was expressed in 21 of 34 tumours; in 17 cases, only a small proportion (1-25%) stained VCAM-1 positive. NCAM was expressed in 14 of 34 tumours; in 11 cases, only a small proportion (1-25%) stained NCAM positive. CD3-positive leucocytes were found in 26 of 32 tumours, whereas CD68-positive leucocytes were present in 33 of 34 tumours. Cox regression analysis revealed that patients with NCAM-positive tumours had a 6.4-fold higher risk of dying from conjunctival melanoma (P = 0.02). NCAM-positive tumours were preferentially (P = 0.03) located in prognostically 'unfavourable' areas (i.e. fornices, palpebral, caruncle) and had no or only a weak CD3-positive infiltrate (P = 0.03).

CONCLUSIONS

ICAM-1, VCAM-1 and NCAM are differentially expressed in conjunctival melanoma. Leucocytes were present in almost every tumour. The association between NCAM expression and prognosis may be related to the differential anatomical tumour location of NCAM-positive and NCAM-negative tumours, and should be considered a preliminary observation due to the limited statistical power of this study.

Evidence of macrophage and lymphocyte, but not dendritic cell, infiltration in posterior uveal melanomas, whilst cultured uveal melanomas demonstrate pluripotency by expressing CD68 and CD163

Although variation in the level of macrophage infiltration has been reported in uveal melanoma, little is known about the expression of other leucocyte markers. An immuno- histochemistry study of the levels of expression of macrophage and other leucocyte markers, in a series of 10 primary choroidal melanoma biopsies, was undertaken. Biopsies were either fixed immediately in formalin and embedded in paraffin wax or established as short-term cultures. Using single- and double-labelling immunohistochemistry, cultured cells and paraffin sections were analysed for a range of melanoma (HMB45, Melan A, S100 and tyrosinase) and immune cell (CD68, CD163, CD45 and CD1a) markers. All samples expressed at least two known melanoma markers. Infiltrating macrophages were present in the majority of sections. When cultured specimens were studied by double-labelling immunofluorescence, uveal melanoma cells were seen to express macrophage markers or have cross-reactivity with related proteins. Expression of the leucocyte antigen CD45 was observed in three tumours but was not present in any cultured cells, whilst the expression of the dendritic cell marker CD1a was absent from all samples.

New prognostic factors in uveal melanomas: potential molecular targets for therapy

Even with advances in the diagnosis and local treatment of uveal melanoma, there has been no significant change in the survival rates of these patients in the last decades. Metastatic disease still occurs at the same frequency, and no systemic therapy is currently offered to patients after local eye treatment. Therefore, experimental and clinical research has been focused on the metastatic cascade in order to elucidate its underlying mechanisms at the molecular level. As a result, new prognostic factors in uveal melanoma have been described that also serve as molecular targets for the development of novel treatments. These prognostic factors/molecular targets, such as membrane receptors, enzymes, cytokines, cytoskeleton components, oncogenes, tumour suppressor genes, cell-cycle proteins and nuclear antigens, are reviewed in this article.