PD-L1: PD-1 interaction contributes to the functional suppression of T-cell responses to human uveal melanoma cells in vitro

Anti-PD-1 antibodies in metastatic uveal melanoma: a treatment option?

Uveal melanomas (UMs) are a rare form of cancer with clinical and pathological characteristics distinct from cutaneous melanomas. Ipilimumab has shown efficacy and safety in the treatment of metastatic UM. This provides a rationale for treatment with other immune checkpoint inhibitors. This is a retrospective review of 15 patients with metastatic UM treated between June 2014 and February 2016, who received treatment with the anti-PD-1 Abs pembrolizumab or nivolumab. Patients were treated at two German university hospitals. Therapy was administered at the approved dosing schedules of 2 mg/kg q3w for pembrolizumab and 3 mg/kg q2w for nivolumab. Treatment was given until first tumor assessment and continued if tumor assessment showed disease control. Tumor assessments were performed at baseline and following scans every 12 weeks. Patients were monitored throughout for adverse events. Best response to treatment was stable disease in four patients. Eight out of 15 (53%) patients received treatment until first tumor assessment. As of February 2016, median progression-free survival (PFS) is 3 months (range 0.75-6.75 months) and overall survival (OS) is 5 months (range 1-16 months). Eight out of 15 (53%) patients are still alive (two patients lost to follow-up) with one out of four patients is in ongoing disease control. Patients with multiple organ metastases and elevated serum lactate dehydrogenase did not respond well to treatment. No objective response to PD-1 Ab therapy was seen. Best response to treatment was stable disease in four patients. Treatment was well tolerated with manageable toxicity.

PD-1 and cancer: molecular mechanisms and polymorphisms

The programmed cell death protein 1 (PD-1) is expressed by activated T cells that act as an immunoregulatory molecule, and are responsible for the negative regulation of T cell activation and peripheral tolerance. The PD-1 gene also encodes an inhibitory cell surface receptor involved in the regulation of T cell functions during immune responses/tolerance. Beyond potent inhibitory effects on T cells, PD-1 also has a role in regulating B cell and monocyte responses. An overexpression of PD-1 has been reported to contribute to immune system avoidance in different cancers. In particular, PD-1 over-expression influences tumor-specific T cell immunity in a cancer microenvironment. Blocking the PD-1/PD-1 ligand (PD-L1) pathway could potentially augment endogenous antitumor responses. Along these lines, the use of PD-1/PD-L1 inhibitors has been applied in clinical trials against diverse forms of cancer. It was believed that antibodies targeting PD-1/PD-L1 might synergize with other treatments that enhance endogenous antitumor immunity by blocking inhibitory receptor-ligand interactions. However, in all cases, the host genetic status (as well as that of the tumor) is likely to have an impact on the expected outcomes. Various investigations have evaluated the association between PD-1 polymorphisms and the risk of various types of cancer. Frequently studied PD-1 polymorphisms, PD-1.1 (rs36084323), PD-1.3 (rs11568821), PD-1.5 (rs2227981), PD-1.9 (rs2227982), and PD-1 rs7421861, and their associations in the risk of susceptibility to different types of cancer are mentioned in this review, as are studies highlighting the significance of conducting genetic association studies in different ethnic populations.

PD-L1 and PD-1 expression correlate with prognosis in extrahepatic cholangiocarcinoma

The present study aimed to investigate the clinicopathological significance of programmed cell death ligand-1 (PD-L1) and programmed cell death protein 1 (PD-1) expression in extrahepatic cholangiocarcinoma (ECC). PD-L1 and PD-1 expression was detected by immunohistochemical methods in 70 ECC formalin-fixed, paraffin-embedded tissue specimens and 50 para-carcinoma tissue specimens. The associations of PD-L1 and PD-1 expression with clinicopathological characteristics and prognosis of ECC patients were explored. Positive rates of PD-L1 and PD-1 expression were increased in ECC tissues compared with those in the corresponding para-carcinoma tissues. Besides, the expression of PD-L1 was correlated with the expression of PD-1 (P<0.05). Statistical analysis revealed that the expression of PD-L1 and PD-1 in ECC tissues exhibited no correlation with patient age, sex or histological grade, but was significantly correlated with tumor-node-metastasis (TNM) stage and lymphatic metastasis. Univariate analysis demonstrated that PD-L1 expression, PD-1 expression, TNM stage and lymphatic metastasis were significantly associated with the survival time of patients. Further multivariate analysis revealed the PD-L1 expression was an independent prognostic factor of patients with ECC. These preliminary results suggested that PD-L1 or PD-1 immunodetection may be a valuable prognostic marker for ECC patients, and that PD-L1 immunodetection may be used as an independent factor to evaluate the prognosis of ECC patients.

Image-Based Phenotypic Screening with Human Primary T Cells Using One-Dimensional Imaging Cytometry with Self-Tuning Statistical-Gating Algorithms

The parallel microfluidic cytometer (PMC) is an imaging flow cytometer that operates on statistical analysis of low-pixel-count, one-dimensional (1D) line scans. It is highly efficient in data collection and operates on suspension cells. In this article, we present a supervised automated pipeline for the PMC that minimizes operator intervention by incorporating multivariate logistic regression for data scoring. We test the self-tuning statistical algorithms in a human primary T-cell activation assay in flow using nuclear factor of activated T cells (NFAT) translocation as a readout and readily achieve an average Z' of 0.55 and strictly standardized mean difference of 13 with standard phorbol myristate acetate/ionomycin induction. To implement the tests, we routinely load 4 µL samples and can readout 3000 to 9000 independent conditions from 15 mL of primary human blood (buffy coat fraction). We conclude that the new technology will support primary-cell protein-localization assays and "on-the-fly" data scoring at a sample throughput of more than 100,000 wells per day and that it is, in principle, consistent with a primary pharmaceutical screen.

Uveal Melanoma: Identifying Immunological and Chemotherapeutic Targets to Treat Metastases

Uveal melanoma is an intraocular malignancy that, depending on its size and genetic make-up, may lead to metastases in up to 50% of cases. Currently, no therapy has been proven to improve survival. However, new therapies exploiting immune responses against metastases are being developed. The primary tumor is well characterized: tumors at high risk of developing metastases often contain macrophages and lymphocytes. However, these lymphocytes are often regulatory T cells that may suppress immune response. Currently, immune checkpoint inhibitors have shown marked efficacy in multiple cancers (eg, cutaneous melanoma) but do not yet improve survival in uveal melanoma patients. More knowledge needs to be acquired regarding the function of T cells in uveal melanoma. Other therapeutic options are related to the biochemical pathways. Targeting the RAF-MEK-ERK pathway with small molecule MEK inhibitors abrogates the growth of UM cells harboring GNAQ/GNA11 Q209 mutations, suggesting that these aberrant G-protein oncogenes mediate, at least in part, their effect through this hallmark proliferation pathway. Other pathways are also implicated, such as those involving c-Jun and YAP. Further studies may show how interference in the different pathways may affect survival.

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.

SOCS1 favors the epithelial-mesenchymal transition in melanoma, promotes tumor progression and prevents antitumor immunity by PD-L1 expression

Silencing of SOCS1 protein with shRNAi lentivirus (shR-SOCS1) led to partial reversion of the tumorigenic phenotype of B16F10-Nex2 melanoma cells. SOCS1 silencing inhibited cell migration and invasion as well as in vitro growth by cell cycle arrest at S phase with increased cell size and nuclei. Down-regulation of SOCS1 decreased the expression of epidermal growth factor receptor, Ins-Rα, and fibroblast growth factor receptors. The present work aimed at analyzing the SOCS1 cell signaling and expression of proteins relevant to tumor development. An RNA microarray analysis of B16F10-Nex2 melanoma cells with SOCS1 silenced by shRNAi-SOCS1 was undertaken in comparison with cells transduced with the empty vector. Among 609 differentially expressed genes, c-Kit, Met and EphA3 cytokine/tyrosine-kinase (TK) receptors were down regulated. A significant decrease in the expression of TK receptors, the phosphorylation of mediators of ERK1/2 and p38 pathways and STAT3 (S727) were observed. Subcutaneous immunization with shR-SOCS1-transduced viable tumor cells rendered protection against melanoma in a syngeneic model, with decreased expression of PD-L1 and of matrix metallo-proteinases (MMPs) and CD-10 in those cells. The present work shows the role of SOCS1 in murine melanoma development and the potential of SOCS1-silenced tumor cells in raising an effective anti-melanoma immune response.

Immune oppression array elucidating immune escape and survival mechanisms in uveal melanoma

AIM

To examine the genetic profile of primary uveal melanoma (UM) as compared to UM in immune escape.

METHODS

Dendritic cells (DC) loaded with lysates of UM cells of high metastatic potential were used to stimulate CTLs(CTLs). When CTLs co-cultured with the UM cells, most UM cells could be eliminated. Survival UM cells grew slowly and were considered to be survival variants and examined by a microarray analysis. These differential genes were analyzed further with Venn Diagrams and functions related to immune escape. We additionally examined transcriptional changes of manually selected survival variants of UM cells and of clinical UM samples by quantitative real-time polymerase chain reaction (qRT-PCR), and analyzed the correlation of these expressions and patients' survival.

RESULTS

Gene expression analyses revealed a marked up-regulation of SLAMF7 and CCL22 and a significant down-regulation of KRT10, FXYD3 and ABCC2. The expression of these genes in the relapsed UM was significantly greater than those in primary UM. UM patients with overexpression of these genes had a shorter survival period as compared with those of their underexpression.

CONCLUSION

Gene expression, in particular of SLAMF7, CCL22, KRT10, FXYD3 and ABCC2, differed between primary UM cells and survival variants of UM cells.

Evolving systemic targeted therapy strategies in uveal melanoma and implications for ophthalmic management: a review

Uveal melanoma (UM) is the most common primary ocular tumour in adults. Despite good local control of the primary tumour with current methods, survival after the development of metastasis has remained poor over the last 30 years. After cutaneous melanoma, UM is the most common type of melanoma, and an ongoing debate exists regarding whether these conditions should be considered separate entities, particularly in the context of targeted therapy, where many of the initial trials for patients with metatatic cutaneous melanoma excluded metastatic UM. This paper will review the recent and ongoing investigations designed to validate systemic targeted therapy and immunotherapy in patients with metastatic UM and suggests ways in which these developments may affect management of UM by ophthalmologists in the near future.

Apigenin inhibits the inducible expression of programmed death ligand 1 by human and mouse mammary carcinoma cells

Programmed death ligand 1 (PD-L1) is expressed by many cancer cell types, as well as by activated T cells and antigen-presenting cells. Constitutive and inducible PD-L1 expression contributes to immune evasion by breast cancer (BC) cells. We show here that the dietary phytochemical apigenin inhibited interferon (IFN)-γ-induced PD-L1 upregulation by triple-negative MDA-MB-468 BC cells, HER2(+) SK-BR-3 BC cells, and 4T1 mouse mammary carcinoma cells, as well as human mammary epithelial cells, but did not affect constitutive PD-L1 expression by triple-negative MDA-MB-231 BC cells. IFN-β-induced expression of PD-L1 by MDA-MB-468 cells was also inhibited by apigenin. In addition, luteolin, the major metabolite of apigenin, inhibited IFN-γ-induced PD-L1 expression by MDA-MB-468 cells. Apigenin-mediated inhibition of IFN-γ-induced PD-L1 expression by MDA-MB-468 and 4T1 cells was associated with reduced phosphorylation of STAT1, which was early and transient at Tyr701 and sustained at Ser727. Apigenin-mediated inhibition of IFN-γ-induced PD-L1 expression by MDA-MB-468 cells also increased proliferation and interleukin-2 synthesis by PD-1-expressing Jurkat T cells that were co-cultured with MDA-MB-468 cells. Apigenin therefore has the potential to increase the vulnerability of BC cells to T cell-mediated anti-tumor immune responses.

Uveal melanoma as a target for immune-therapy

Uveal melanoma (UM) is a rare disease that can be deadly in spite of adequate local treatment. Systemic therapy with chemotherapy is usually ineffective and new-targeted therapies have not improved results considerably. The eye creates an immunosuppressive environment in order to protect eyesight. UM cells use similar processes to escape immune surveillance. Regarding innate immunity the production of macrophage inhibiting factor (MIF) and TGF-β, added to MHC class I upregulation, inhibits the action of natural killer (NK) cells. UM cells produce cytokines such as IL-6 and IL-10 that favor macrophage differentiation to the M2 subtype, which promote tumor growth instead of an effective immune response. UM cells also impair the adaptive immune response through production of indoleamine 2,3-dioxygenase (IDO), overexpression of programmed death ligand-1 (PD-L1), alteration of FasL expression, and resistance to perforin. This biological background suggests that immunotherapy could be effective in fighting UM. A Phase II clinical trial with Ipilimumab has shown promising results with mean Overall Survival rate of ten months, and close to 50% of the patients alive at one year. Clinical trials with anti-PD1 antibodies in monotherapy and in combination with anti-CTLA4 are currently recruiting patients worldwide.

Immunotherapy for uveal melanoma

Uveal melanoma (UM) is a rare cancer with a high mortality rate. In comparison to cutaneous melanoma, UM has unique immunological features. Arising in the immune suppressive environment of the eye, it maintains immune resistance once metastatic. This is considered a major obstacle for successful immunotherapy in UM. However, a growing body of evidence suggests strategies that may abrogate resistance and enhance antitumor immunity in UM. Recently, three new immune agents have been approved for melanoma. While these drugs demonstrate durable clinical responses with long-term remissions in metastatic cutaneous melanoma, only limited data exist in metastatic UM. In this review, immunological aspects of UM and data from clinical studies of immunotherapeutic agents and regimens for UM will be discussed.

Ocular diseases: immunological and molecular mechanisms

Many factors, such as environmental, microbial and endogenous stress, antigen localization, can trigger the immunological events that affect the ending of the diverse spectrum of ocular disorders. Significant advances in understanding of immunological and molecular mechanisms have been researched to improve the diagnosis and therapy for patients with ocular inflammatory diseases. Some kinds of ocular diseases are inadequately responsive to current medications; therefore, immunotherapy may be a potential choice as an alternative or adjunctive treatment, even in the prophylactic setting. This article first provides an overview of the immunological and molecular mechanisms concerning several typical and common ocular diseases; second, the functions of immunological roles in some of systemic autoimmunity will be discussed; third, we will provide a summary of the mechanisms that dictate immune cell trafficking to ocular local microenvironment in response to inflammation.

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.

Implication of programmed cell death ligand 1 expression in tumor recurrence and prognosis in rectal cancer with neoadjuvant chemoradiotherapy

BACKGROUND

Programmed cell death ligand 1 (PD-L1) regulates immune responses through interaction with its receptor. PD-L1 is not only a predictor of poor prognosis but also a new therapeutic target in several malignancies. Neoadjuvant chemoradiotherapy (CRT) is an effective tool for local control of rectal cancer, but the disease recurrence rate remains high. The aim of this study was to retrospectively evaluate the correlation between PD-L1 expression and clinicopathological variables in rectal cancer after neoadjuvant CRT.

MATERIALS AND METHODS

A total of 90 rectal cancer patients who underwent neoadjuvant CRT were enrolled in this study. We evaluated PD-L1 expression using immunohistochemistry. Moreover, we investigated the correlation between PD-L1 expression and tumor-infiltrating T cells, and between CD8- and Foxp3-positive cells.

RESULTS

Patients with high PD-L1 expression more frequently had vascular invasion and tumor recurrence compared to patients with low PD-L1 expression (P = 0.0225 and P = 0.0051). High PD-L1 expression was significantly associated with poor recurrence-free and overall survival (P = 0.0027 and P = 0.0357). Multivariate analysis revealed lymph node metastasis and high PD-L1 expression as independent risk factors for tumor recurrence (P = 0.0102 and P = 0.0374). Numbers of infiltrating CD8-positive cells in patients with high PD-L1 expression were significantly lower than in patients with low PD-L1 expression (P = 0.0322).

CONCLUSION

Our data suggest that inhibition of PD-L1 may be a new immunotherapeutic strategy to reduce tumor recurrence and improve prognosis in patients with rectal cancer after neoadjuvant CRT.

Relationship between expression of PD-L1 and PD-L2 on esophageal squamous cell carcinoma and the antitumor effects of CD8⁺ T cells

The programmed death-1 (PD-1)/programmed death-ligands (PD-Ls) signal pathway has been implicated as a potential immune escape mechanism in several human cancers. However, the studies of PD‑1/PD‑Ls pathway in esophageal squamous cell carcinoma (ECSS) are not yet sufficient. The current study investigated the expression of PD‑L1, PD‑L2 and PD‑1 in ESCC tissues. The correlations between the expression of these proteins and clinical histopathological parameters were analyzed. Then the stable transfected Ec109 cell lines overexpressing PD‑L1/PD‑L2 were established by plasmid transfection successfully. Ec109 and CD8+ T cells were co‑cultured to analyze the effects of PD‑1/PD‑Ls signal pathway on the function of CD8+ T cells including proliferation, apoptosis and interferon‑γ production. We found that PD‑L1-positive patients had significantly poorer prognosis than the negative patients, while their prognosis was not related to PD‑L2 expression. The count of PD‑1+ TILs (tumor‑infiltrating lymphocytes) was negatively correlated with both PD‑L1 and PD‑L2 expression. In functional studies, we found that PD‑1/PD‑Ls signal pathway was able to downregulate the function of CD8+ T lymphocyte and its function could be restored by blocking the signal pathway. This indicates that PD‑1/PD‑Ls may prevent effective antitumor immunity, which provides important evidence to delineate the cellular immune deficiency mechanism in ESCC. Therefore, PD-1/PD-Ls are predicted to become novel targets for ESCC immunotherapy.

Phase II DeCOG-study of ipilimumab in pretreated and treatment-naïve patients with metastatic uveal melanoma

Purpose

Up to 50% of patients with uveal melanoma (UM) develop metastatic disease with limited treatment options. The immunomodulating agent ipilimumab has shown an overall survival (OS) benefit in patients with cutaneous metastatic melanoma in two phase III trials. As patients with UM were excluded in these studies, the Dermatologic Cooperative Oncology Group (DeCOG) conducted a phase II to assess the efficacy and safety of ipilimumab in patients with metastatic UM.

Patients and Methods

We undertook a multicenter phase II study in patients with different subtypes of metastatic melanoma. Here we present data on patients with metastatic UM (pretreated and treatment-naïve) who received up to four cycles of ipilimumab administered at a dose of 3 mg/kg in 3 week intervals. Tumor assessments were conducted at baseline, weeks 12, 24, 36 and 48 according to RECIST 1.1 criteria. Adverse events (AEs), including immune-related AEs were graded according to National Cancer Institute Common Toxicity Criteria (CTC) v.4.0. Primary endpoint was the OS rate at 12 months.

Results

Forty five pretreated (85%) and eight treatment-naïve (15%) patients received at least one dose of ipilimumab. 1-year and 2-year OS rates were 22% and 7%, respectively. Median OS was 6.8 months (95% CI 3.7–8.1), median progression-free survival 2.8 months (95% CI 2.5–2.9). The disease control rate at weeks 12 and 24 was 47% and 21%, respectively. Sixteen patients had stable disease (47%), none experienced partial or complete response. Treatment-related AEs were observed in 35 patients (66%), including 19 grade 3–4 events (36%). One drug-related death due to pancytopenia was observed.

Conclusions

Ipilimumab has very limited clinical activity in patients with metastatic UM. Toxicity was manageable when treated as per protocol-specific guidelines.

Trial Registration

ClinicalTrials.gov NCT01355120

Genetically modified murine adipose-derived mesenchymal stem cells producing interleukin-2 favor B16F10 melanoma cell proliferation

Adipose-derived mesenchymal stem cells (ADSCs) are attractive tools for cancer gene therapy due to their intrinsic tropism to the tumor environment. Interleukin-2 (IL2) is recognized as a key regulatory molecule, which enhances the activity and growth of the immune effector cell function. High-Dose IL2 Therapy is an option for treatment of malignant melanoma but has frequent, often serious and sometimes life-threatening side effects. Here we investigated the effect of genetically modified ADSCs (GM-ADSCs) expressing IL2 in immunocompetent mouse models of subcutaneous and lung metastatic melanoma. Prior to in vivo studies, we demonstrated that IL2 produced by GM-ADSCs may act as a growth factor for melanoma cells due to the increased viability and reduced apoptosis of melanoma cells after in vitro treatment. Subcutaneous co-injection of IL2-expressing ADSCs with melanoma cells significantly enhanced the melanoma tumor growth. Furthermore, histological analysis of subcutaneous tumors for IL2 and Melan-A (a melanocytic differentiation marker) confirmed that most of cells in melanoma/IL2-ADSC co-injected tumors are melanoma cells, not IL2-ADSCs. In pulmonary metastases model, melanoma cells were injected intravenously and 10 days later mice were treated by systematical injection of GM-ADSCs. Intravenously injected IL2-ADSCs engrafted into melanoma lung tumors but were unable to reduce melanoma lung metastases. Besides, administered IL2-ADSCs significantly reduced systemic CD4+ cells and did not impact the total survival of lung metastases melanoma bearing mice. In conclusion, this study showed that IL2-producing ADSCs can favor B16F10 melanoma cell proliferation. Therefore, therapies utilizing IL2 have to be taken into careful consideration.

The PD-1/PD-L1 pathway: biological background and clinical relevance of an emerging treatment target in immunotherapy

INTRODUCTION

The co-inhibitory receptor programmed death 1 (PD-1) and its ligands are key regulators in a wide spectrum of immune responses and play a critical role in autoimmunity and self-tolerance as well as in cancer immunology. Emerging evidence suggests that cancer cells might use the PD-1/PD-ligand (PD-L) pathway to escape anti-tumor immunity. Based on this evidence, early phase human clinical trials targeting the PD-1/PD-L pathway are currently underway for multiple human cancers.

AREAS COVERED

The role of the PD-1/PD-L pathway in autoimmune disease, viral infections as well as in malignant neoplasms is discussed and an overview of the existing therapeutics as well as the results of clinical trials targeting this pathway in cancer is given.

EXPERT OPINION

The PD-1/PD-L pathway represents an important mechanism of immune evasion for malignant neoplasms. Early clinical trials indicate effectiveness of PD-1/PD-L pathway blockade in several solid cancers. However, greater insight into the exact mechanisms by which tumors are able to evade anti-tumor immunity is needed to increase clinical effectiveness, for example by combination blockade of diverse co-inhibitory receptors.

PhiC31/PiggyBac modified stromal stem cells: effect of interferon γ and/or tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) on murine melanoma

Background

TRAIL and IFNγ are promising anti-cancer cytokines and it has been shown that IFNγ may sensitize cancer cells to TRAIL. Adipose derived mesenchymal stem cells (ADSCs) are attractive vehicles for delivering anti-cancer agents. In this study, we evaluated the therapeutic potential of PhiC31 (φC31) recombinase and/or piggyBac transposase (pBt) modified ADSCs expressing either TRAIL, IFNγ, or co-expressing TRAIL/IFNγ in mouse models of melanoma.

Methods

The expression and bioactivity of mouse IFNγ and TRAIL in φC31 and pBt modified cells were confirmed. We examined the effects of modified ADSCs on signal intensity of red fluorescence protein expressed by melanoma cells in subcutaneous tumors or established lung metastases and on survival (6 mice per group). We also conducted a flow cytometric analysis of systemic CD4⁺CD25⁺FOXP3⁺ T regulatory cells (Tregs) and histological analysis of melanoma tumors. Data were analyzed by Student t test, ANOVA, and log-rank tests. All statistical tests were two-sided.

Results

We demonstrated non-viral DNA-integrating vectors can be used for stable transgene expression. IFNγ inhibited melanoma cell growth in vitro probably via IFNγ-induced JAK/STAT1 signaling pathway activation. Murine TRAIL induced apoptosis in the human cell lines CAOV-4 and Ej-138, while MCF7 and B16F10 cells appeared to be insensitive to TRAIL. Treatment of melanoma cells with IFNγ did not influence their response to TRAIL. In contrast, results from in vivo studies showed that IFNγ-expressing ADSCs, engrafted into tumor stroma, inhibited tumor growth and angiogenesis, prevented systemic increase of Tregs, increased PD-L1 expression and CD8+ infiltration (but not interleukin-2+ cells), and prolonged the survival of mice (68 days, 95% confidence interval [CI] =52 to 86 days compared to 36 days, 95% CI =29 to 39 days for control, P < .001).

Conclusions

For the first time, we employed DNA integrating vectors for safe and stable modification of MSCs. Our data indicate potential of non-virally modified IFNγ-expressing ADSCs for treatment of melanoma through direct effects of IFNγ. This study may have a significant role in the management of cancer in the future.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-255) contains supplementary material, which is available to authorized users.

Biology of advanced uveal melanoma and next steps for clinical therapeutics

Uveal melanoma is the most common intraocular malignancy although it is a rare subset of all melanomas. Uveal melanoma has distinct biology relative to cutaneous melanoma, with widely divergent patient outcomes. Patients diagnosed with a primary uveal melanoma can be stratified for risk of metastasis by cytogenetics or gene expression profiling, with approximately half of patients developing metastatic disease, predominately hepatic in location, over a 15-yr period. Historically, no systemic therapy has been associated with a clear clinical benefit for patients with advanced disease, and median survival remains poor. Here, as a joint effort between the Melanoma Research Foundation's ocular melanoma initiative, CURE OM and the National Cancer Institute, the current understanding of the molecular and immunobiology of uveal melanoma is reviewed, and on-going laboratory research into the disease is highlighted. Finally, recent investigations relevant to clinical management via targeted and immunotherapies are reviewed, and next steps in the development of clinical therapeutics are discussed.

Programmed death-1 pathway in cancer and autoimmunity

Programmed death-1 (PD-1) is a co-receptor that is expressed predominantly by T cells. The binding of PD-1 to its ligands, PD-L1 or PD-L2, is vital for the physiologic regulation of the immune system. A major functional role of the PD-1 signaling pathway is the inhibition of self-reactive T cells, which serve to protect against autoimmune diseases. Elimination of the PD-1 pathway can therefore result in the breakdown of immune tolerance that can ultimately lead to the development of pathogenic autoimmunity. Conversely, tumor cells can at times co-opt the PD-1 pathway to escape from immunosurveillance mechanisms. Therefore, blockade of the PD-1 pathway has become an attractive target in cancer therapy. Recent clinical trials have shown that anti-PD-1 agents have profound effects on solid tumor regression. Current approaches include six agents that are either PD-1 and PD-L1 targeted neutralizing antibodies or fusion proteins. More than forty clinical trials are underway to better define the role of PD-1 blockade in variety of tumor types. In this review we will highlight the basic biology of the PD-1 system and discuss its potential roles in both autoimmunity and cancer. We propose that future research on PD-1 may lead to the translation of fundamental regulatory pathways into the development of practical new approaches for the treatment of autoimmune diseases and cancer.

Systemic treatment of metastatic uveal melanoma: review of literature and future perspectives

Up to 50% of patients with uveal melanoma develop metastatic disease with poor prognosis. Regional, mainly liver-directed, therapies may induce limited tumor responses but do not improve overall survival. Response rates of metastatic uveal melanoma (MUM) to systemic chemotherapy are poor. Insights into the molecular biology of MUM recently led to investigation of new drugs. In this study, to compare response rates of systemic treatment for MUM we searched Pubmed/Web of Knowledge databases and ASCO website (1980-2013) for "metastatic/uveal/melanoma" and "melanoma/eye." Forty studies (one case series, three phase I, five pilot, 22 nonrandomized, and two randomized phase II, one randomized phase III study, data of three expanded access programs, three retrospective studies) with 841 evaluable patients were included in the numeric outcome analysis. Complete or partial remissions were observed in 39/841 patients (overall response rate [ORR] 4.6%; 95% confidence intervals [CI] 3.3-6.3%), no responses were observed in 22/40 studies. Progression-free survival ranged from 1.8 to 7.2, median overall survival from 5.2 to 19.0 months as reported in 21/40 and 26/40 studies, respectively. Best responses were seen for chemoimmunotherapy (ORR 10.3%; 95% CI 4.8-18.7%) though mainly in first-line patients. Immunotherapy with ipilimumab, antiangiogenetic approaches, and kinase inhibitors have not yet proven to be superior to chemotherapy. MEK inhibitors are currently investigated in a phase II trial with promising preliminary data. Despite new insights into genetic and molecular background of MUM, satisfying systemic treatment approaches are currently lacking. Study results of innovative treatment strategies are urgently awaited.

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.

Influence of CD8+ T regulatory cells on intraocular tumor development

The interior of the eye, or uvea, is a site of immune privilege where certain immune responses are attenuated or completely excluded to protect non-regenerating tissues essential for vision. One consequence of this immunoregulation is compromised immune mediated elimination of intraocular tumors. For example, certain murine tumor cell lines which are rejected by host immune responses when transplanted in the skin grow progressively when placed in the anterior chamber (a.c.) of the eye. Progressive ocular tumor growth occurs despite induction of tumor-specific CD8+ T cell responses capable of eliminating a subsequent tumor challenge in the skin or opposite eye. Why these CD8+ T effectors fail to eliminate established ocular tumors is not known. It is well appreciated that growth of tumors in the a.c. induces the generation of immunosuppressive CD8+ T regulatory (Treg) cells. However, the contribution of CD8+ Treg in ocular tumor progression remains unclear. Several studies indicate that these CD8+ Treg target responding CD4+ T cells to inhibit their induction of macrophage-dependent delayed type hypersensitivity (DTH) responses to tumor antigens (Ags). However, induction of tumor-specific CD4+ T cell responses does not assure intraocular tumor elimination. This review is focused on how CD8+ Treg could influence the tumoricidal activity of ocular tumor-specific CD8+ T effector cells.

Regional lymphatic immunity in melanoma

Melanoma is an immunogenic tumor that has developed methods to successfully evade immune recognition, while paradoxically spreading through the lymphatic system. Increasing evidence supports that melanoma-derived factors suppress regional immunity within the host. At a very early stage, melanoma communicates with the tumor-draining lymph nodes, and prepares them for seeding of metastatic disease by stimulating lymphangiogenesis and downregulation of the sentinel lymph node immunity well before the malignant cells arrive. Investigations have demonstrated that the induction of suppressor cells, peripheral tolerance, and a less tumor-responsive Th2 cytokine environment may provide a hospitable environment for subsequent lymphatic metastasis. Patients with early-stage disease may benefit from the restoration of the regional immune function to a level that controls the progression of residual occult metastases and ensures a durable clinical response. Herein we provide a succinct summary of the current progress in this field in order to guide future investigations.

Expression of 12 cytokines in aqueous humour of uveal melanoma before and after combined Ruthenium-106 brachytherapy and transpupillary thermotherapy

PURPOSE

To determine the aqueous humour levels of 12 cytokines in eyes with uveal melanoma and whether their expression changes after combined Ru-106 brachytherapy and transpupillary thermotherapy (TTT).

METHODS

Aqueous humour samples were collected from 20 patients with previously untreated uveal melanoma undergoing combined Ru-106 brachytherapy and TTT, both at the time of plaque placement and removal. Using multiplex biochip array technology, 12 different cytokines were measured, including interleukin (IL)-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, vascular endothelial growth factor (VEGF), tumour necrosis factor (TNF)-α, interferon (IFN)-γ, epidermal growth factor (EGF) and monocyte chemoattractant protein (MCP)-1. Aqueous humour from 20 patients undergoing cataract surgery was used as control.

RESULTS

IL-6, IL-8, IFN-γ and MCP-1 were highly expressed in uveal melanoma, whereas IL-2, IL-10 and TNF- α were low in expression. There was a positive correlation between tumour height and IL-8 level (p = 0.020). Vascular endothelial growth factor tends to be highly expressed in melanoma-containing eyes (p = 0.056). Levels of IL-6, IL-8 and IL-1β increased after the mean 117 ± 38 hrs of brachytherapy and adjunctive TTT with a tumour apex dose of 61 ± 28 Gy and a scleral contact dose of 786 ± 226 Gy. Increase in levels of IL-6 (p = 0.003) and IL-8 (p = 0.046) positively correlated with scleral contact dose.

CONCLUSIONS

Cytokines such as IL-6, IL-8, IFN-γ and MCP-1 may be implicated in the progression of uveal melanoma. Ocular irradiation from a Ru-106 plaque promoted an increase in the levels of IL-6, IL-8 and IL-1β, modulation of which could be useful in managing radiation-related side effects.

Antigen-specific versus antigen-nonspecific immunotherapeutic approaches for human melanoma: the need for integration for optimal efficacy?

Due to its immunogenecity and evidence of immune responses resulting in tumor regression, metastatic melanoma has been the target for numerous immunotherapeutic approaches. Unfortunately, based on the clinical outcomes, even the successful induction of tumor-specific responses does not correlate with efficacy. Immunotherapies can be divided into antigen-specific approaches, which seek to induce T cells specific to one or several known tumor associated antigens (TAA), or with antigen-nonspecific approaches, which generally activate T cells to become nonspecifically lytic effectors. Here the authors critically review the different immunotherapeutic approaches in 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.

Costimulatory molecule expression on human uveal melanoma cells: functional analysis of CD40 and B7-H1

Costimulatory molecules play important roles in regulating T cell function in tumor immunity. In this study, we investigated costimulatory molecule expression on human uveal melanoma cells (a primary culture, and OCM-1, OMM-1 and 92-1 cell lines) and assessed the functional roles of selected costimulatory molecules. Uveal melanoma cells were incubated in the presence or absence of IFN-γ and expression of costimulatory molecules on the cells was measured by flow cytometry. The costimulatory effect of B7-H1-expressing uveal melanoma cells on cytokine production by purified T cells was studied in uveal melanoma/T cell co-culture experiments using a blocking anti-B7-H1 monoclonal antibody (mAb). The functional role of CD40-mediated interactions in modifying immune responses to uveal melanoma cells was assessed in vitro using recombinant human CD40 ligand (rhCD40L). MHC class I and B7-H1 were consistently detected and further upregulated by IFN-γ stimulation in all human uveal melanoma cell cultures. CD40 was consistently detected and further upregulated by IFN-γ stimulation in primary culture, OCM-1, and OMM-1 but not 92-1. IL-2 production from purified CD3(+) T cells co-stimulated with IFN-γ-treated uveal melanoma cells was significantly enhanced by the addition of anti-B7-H1 mAb. Treatment of primary culture, OCM-1, or OMM-1 with rhCD40L induced or enhanced secretion of chemokines IL-8, MCP-1, IP-10 and RANTES. These results suggest that the expression of B7-H1 on IFN-γ-treated uveal melanoma cells contributes to suppression of T cells by decreasing IL-2 production. In contrast, CD40 expressed on uveal melanoma cells plays an important role in augmenting anti-tumor immunity by stimulating chemokine production. The dual effects of CD40 and B7-H1 may contribute to positive or negative regulation of anti-tumor immune responses to human uveal melanoma.

Progressive upregulation of PD-1 in primary and metastatic melanomas associated with blunted TCR signaling in infiltrating T lymphocytes

Programmed death-1 (PD-1) is involved in T-cell tolerance to self-antigens. For some cancers, it has been suggested that the expression of a ligand of PD-1, namely PD-L1, could contribute to tumor escape from immune destruction. Nevertheless, the relationship between PD-1 expression on tumor-infiltrating T lymphocytes (TILs), disease stage, and TIL responsiveness is still poorly documented. In this study, we show that freshly isolated CD4(+) and CD8(+) TILs express substantial levels of PD-1 in primary melanomas. The expression of PD-1 was further increased at later stages in distant cutaneous metastases, especially on CD8(+) TILs. The expression of PD-1 ligands was frequent only in metastases, on both tumor cells and tumor-derived myeloid cells. TILs isolated from these cutaneous tumors are poorly reactive ex vivo, with blunted calcium response and IFN-γ production after TCR stimulation. Surprisingly, in distinct parts of a primary melanoma, either invasive or regressing, we show that TILs similarly express PD-1 and remain dysfunctional. The expressions of PD-1 and PD-L1 in metastatic melanoma lesions could be considered as witnesses of an unsuccessful anti-tumoral immune response, but the direct involvement of PD-1 in the severity of the disease, and the importance of TILs in tumor regression, remain to be established.

Tumor cell expression of programmed cell death-1 ligand 1 is a prognostic factor for malignant melanoma

BACKGROUND

: Melanoma tends to be refractory to various immunotherapies because of tumor-induced immunosuppression. To investigate the mechanism underlining the immunosuppression of melanoma patients, the authors focused on programmed cell death-1 (PD-1)/PD-1 ligand 1 (PD-L1) interaction between tumor cells and T cells.

METHODS

: Melanoma specimens were collected from 59 primary tumors, 16 lymph nodes, and 4 lesions of in-transit metastasis. Specimens stained with anti-PD-L1 monoclonal antibodies were digitalized to jpg files. To evaluate the intensity of PD-L1 expression, histograms were used, and the red density (RD) was measured. PD-1 expression on T cells was analyzed in blood samples from 10 patients who had stage IV melanoma and in 4 samples of in-transit metastases.

RESULTS

: Twenty-five patients comprised the "low" PD-L1 expression group (RD value, <90), and 34 patients comprised the "high" group (RD value, > or =90). Breslow tumor thickness in the high-expression group was significantly higher than in the low-expression group. Univariate and multivariate analyses revealed that the overall survival rate of the high-expression group was significantly lower than that of the low-expression group. In all patients with stage IV disease who were examined, both CD8-positive and CD4-positive T cells had significantly higher PD-1 expression levels in the peripheral blood. Tumor-infiltrating T cells expressed high levels of PD-1, and its expression was elevated further during the clinical course.

CONCLUSIONS

: The current results indicated that there is a correlation between the degree of PD-L1 expression and the vertical growth of primary tumors in melanoma. Multivariate analysis demonstrated that PD-L1 expression is an independent prognostic factor for melanoma. Cancer 2010. (c) 2010 American Cancer Society.

Regression of advanced melanoma upon withdrawal of immunosuppression: case series and literature review

We report two cases of stage IV malignant melanoma arising in patients treated with azathioprine for myasthenia gravis. In both cases, the melanoma metastases regressed upon withdrawal of immunosuppression. One patient remains melanoma free at 10 years, and the second patient experienced an 18-month disease free period. There is one prior case report in the medical literature to support full immune reconstitution for treatment in advanced immunosuppression-related melanoma, and one case series suggesting that transplant patients developing melanoma may benefit from a switch to sirolimus. Virtually, no data exist for the medical management of early stage melanoma in the immunosuppressed patients. We review the limited preclinical data in support of immune reconstitution and the data on immunosuppression as a risk factor for melanoma. We conclude that reduction or withdrawal of immunosuppression may be beneficial in patients with advanced stage melanoma and warrants further consideration in patients with early stage 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.