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

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

Dynamic observation: Immune-privileged microenvironment limited the effectiveness of immunotherapy in an intraocular metastasis mouse model

Introduction: Intraocular metastasis (IM) occurred in approximately 8-10% of patients with metastatic malignancy, for whom oncological immunotherapies showed poor visual potential. However, the mechanism for that inefficiency remains unclear and requires further exploration. Methods: we established a novel mouse model of intraocular metastasis by intracarotid injection of cutaneous melanoma cells. We investigated disease progression using ophthalmic and histological examinations. We used combined anti-PD-1 and anti-CTLA4 antibodies for immunotherapy and evaluate the therapeutic effects in mice model. In addition, we characterized the immune microenvironment of tumor infiltrating CD8+ T by fluorescence staining and assessed their cytotoxicity by flow cytometry. Results: All mice presented IM in the left eye, while the right eye was healthy. Uveal tissues with rich vascularity (e.g., the iris, ciliary body, and choroid) initiated intraocular metastasis at an early stage, and intraocular metastasis development resulted in several secondary changes, including corneal swelling, retinal detachment, and intratumoral haemorrhage. Immunotherapy could inhibit intraocular metastasis, prolong the time to eye rupture but did not prevent rupture ending. This inefficiency might be attributed to ocular tissues specificities that inhibited CD8+ T cells infiltration via PD-L1 expression. PD-L1low corneal tissue resisted tumor invasion with high levels of CD8+ T cells infiltration, whereas CD8+ T cells were deficient in PD-L1high uveal metastasis. Furthermore, we found a significantly increased PD-1+/- CD4+ and PD-1+/- CD8+ T cells infiltrating the intratumoral haemorrhage area. Although these CD8+ T cells in the IM were not exhausted and had a higher capacity of cytotoxicity (higher Interferon-γ ratio) than CD8+ T cells in the blood, FasL+ PD-L1+ ocular tissue can strongly inhibit these IM infiltrating T cells. Conclusions: Immunotherapy can inhibit the disease progression of intraocular metastasis. Enhancing the effects of tumor-infiltrating CD8+ T cells should be one of the highest potentials to improve the visual potential.

Uveal melanoma: progress in molecular biology and therapeutics

Uveal melanoma (UM) is the most common intraocular malignancy in adults. So far, no systemic therapy or standard treatment exists to reduce the risk of metastasis and improve overall survival of patients. With the increased knowledge regarding the molecular pathways that underlie the oncogenesis of UM, it is expected that novel therapeutic approaches will be available to conquer this disease. This review provides a summary of the current knowledge of, and progress made in understanding, the pathogenesis, genetic mutations, epigenetics, and immunology of UM. With the advent of the omics era, multi-dimensional big data are publicly available, providing an innovation platform to develop effective targeted and personalized therapeutics for UM patients. Indeed, recently, a great number of therapies have been reported specifically for UM caused by oncogenic mutations, as well as other etiologies. In this review, special attention is directed to advancements in targeted therapies. In particular, we discuss the possibilities of targeting: GNAQ/GNA11, PLCβ, and CYSLTR2 mutants; regulators of G-protein signaling; the secondary messenger adenosine diphosphate (ADP)-ribosylation factor 6 (ARF6); downstream pathways, such as those involving mitogen-activated protein kinase/MEK/extracellular signal-related kinase, protein kinase C (PKC), phosphoinositide 3-kinase/Akt/mammalian target of rapamycin (mTOR), Trio/Rho/Rac/Yes-associated protein, and inactivated BAP1; and immune-checkpoint proteins cytotoxic T-lymphocyte antigen 4 and programmed cell-death protein 1/programmed cell-death ligand 1. Furthermore, we conducted a survey of completed and ongoing clinical trials applying targeted and immune therapies for UM. Although drug combination therapy based on the signaling pathways involved in UM has made great progress, targeted therapy is still an unmet medical need.

Identification of an immune-related signature for the prognosis of uveal melanoma

AIM

To construct an immune-related prognostic signature (IPS) that can distinguish and predict prognosis in uveal melanoma (UM).

METHODS

The transcriptomic data and clinicopathological information of 80 UM patients were extracted from the TCGA database. These patients were randomly assigned to a training and a testing set.

RESULTS

Lasso Cox analysis was performed for the prognostic immune-related genes to develop an IPS for UM in the training set. The signature was validated in both the testing set and entire cohort. We confirmed the prognostic value of our IPS in distinct subgroups and found its association with the T stage and basal diameter of the tumor. Tumor Immune Estimation Resource database analysis revealed that the IPS was negatively correlated with the infiltration of neutrophils and dendritic cells, but positively correlated with the infiltration level of CD8+ T cells. In addition, we demonstrated that immune checkpoints containing PD-1, CTLA-4, IDO, and TIGIT were moderately associated with the IPS.

CONCLUSION

This is the first study to develop and validate an immune-related signature with the ability of predicting prognosis for UM patients. Further studies are needed to validate its prediction accuracy.

Circulating tumor cells in cancer patients: developments and clinical applications for immunotherapy

Cancer metastasis is the leading cause of cancer-related death. Circulating tumor cells (CTCs) are shed into the bloodstream from either primary or metastatic tumors during an intermediate stage of metastasis. In recent years, immunotherapy has also become an important focus of cancer research. Thus, to study the relationship between CTCs and immunotherapy is extremely necessary and valuable to improve the treatment of cancer. In this review, based on the advancements of CTC isolation technologies, we mainly discuss the clinical applications of CTCs in cancer immunotherapy and the related immune mechanisms of CTC formation. In order to fully understand CTC formation, sufficiently and completely understood molecular mechanism based on the different immune cells is critical. This understanding is a promising avenue for the development of effective immunotherapeutic strategies targeting CTCs.

Aging boosts antiviral CD8+T cell memory through improved engagement of diversified recall response determinants

The determinants of protective CD8+ memory T cell (CD8+TM) immunity remain incompletely defined and may in fact constitute an evolving agency as aging CD8+TM progressively acquire enhanced rather than impaired recall capacities. Here, we show that old as compared to young antiviral CD8+TM more effectively harness disparate molecular processes (cytokine signaling, trafficking, effector functions, and co-stimulation/inhibition) that in concert confer greater secondary reactivity. The relative reliance on these pathways is contingent on the nature of the secondary challenge (greater for chronic than acute viral infections) and over time, aging CD8+TM re-establish a dependence on the same accessory signals required for effective priming of naïve CD8+T cells in the first place. Thus, our findings reveal a temporal regulation of complementary recall response determinants that is consistent with the recently proposed "rebound model" according to which aging CD8+TM properties are gradually aligned with those of naïve CD8+T cells; our identification of a broadly diversified collection of immunomodulatory targets may further provide a foundation for the potential therapeutic "tuning" of CD8+TM immunity.

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.

CTCs 2020: Great Expectations or Unreasonable Dreams

Circulating tumor cells (CTCs) are cellular elements that can be scattered into the bloodstream from primary cancer, metastasis, and even from a disseminated tumor cell (DTC) reservoir. CTCs are “seeds”, able to give rise to new metastatic lesions. Since metastases are the cause of about 90% of cancer-related deaths, the significance of CTCs is unquestionable. However, two major issues have stalled their full clinical exploitation: rarity and heterogeneity. Therefore, their full clinical potential has only been predicted. Finding new ways of studying and using such tremendously rare and important events can open new areas of research in the field of cancer research, and could drastically improve tumor companion diagnostics, personalized treatment strategies, overall patients management, and reduce healthcare costs.

Investigation of indoleamine 2,3-dioxygenase 1 expression in uveal melanoma

The purpose of this study was to investigate indoleamine 2,3-dioxygenase 1 (IDO1) expression and its implications in uveal melanoma (UM). Bioinformatics analysis was performed on microarray data (GSE22138 and GSE27831) from the Gene Expression Omnibus (GEO) database to evaluate IDO1 expression in mRNA level. Ninety-two cases in the database were divided into the IDO1-high group (46 cases) and IDO1-low group (46 cases). Paraffin embedded tumor sections from 27 patients with UM were studied by immunofluorescence. The mRNA results showed that IDO1 expression was inversely correlated with tumor thickness (9.93 ± 3.33 mm in IDO1-high group vs. 11.56 ± 2.38 mm in IDO1-low group) (p = 0.016) and metastatic rate (30.4% in IDO1-high group vs. 69.6% in IDO1-low group, p < 0.001). The IDO1-high group showed higher immune cell gene expression: CD3D (6.56 ± 1.0 vs. 5.46 ± 0.53, p < 0.0001), CD4 (4.72 ± 0.4 vs. 4.2 ± 0.42, p < 0.0001), and CD68 (6.17 ± 1.23 vs. 5.53 ± 0.77, p = 0.015). Further analysis showed that immune-suppressive T regulatory cell genes (CD3D, CD4, IL2RA and FOXP3) were expressed in 67.4% (31/46) cases in the IDO1-high group and 23.91% (11/46) cases in the IDO1-low group. In addition, IDO1 and interferon gamma (IFNG) mRNA expression were strongly correlated (r = 0.70, p < 0.0001). The correlation analysis of different immune checkpoints showed that IDO1 was positively correlated with CD274(PDL1), but not CTLA4 or PDCD1.The disease-free survival (DFS) in the IDO1-high/IFNG-high group was better than that of the IDO1-low/IFNG-low group. The IDO1 immunostaining result showed that 2 cases in 18 UMs with Bruch's membrane (BM) rupture and 7 out of 9 cases without BM rupture were scored high (Grade 2-3) (p = 0.001). Comparing the immune cells staining results between IDO1-high group and IDO1-low group, higher percentage of patients in the former group had high levels of T cells and macrophages infiltration, but only the difference in macrophage was statistically significant (CD68, 77.78% vs. 27.78%, p = 0.04). The analysis based on GEO data and the result from immunostaining study are consistent with each other. In conclusion, the expression of IDO1 is probably induced by IFNγ from infiltrated immune cells in UM. BM rupture is an important indicator of IDO1 expression level and distribution pattern. The complex role of IDO1 may limit its therapeutic effect in UM.

The Interplay between Circulating Tumor Cells and the Immune System: From Immune Escape to Cancer Immunotherapy

Circulating tumor cells (CTCs) have aroused increasing interest not only in mechanistic studies of metastasis, but also for translational applications, such as patient monitoring, treatment choice, and treatment change due to tumor resistance. In this review, we will assess the state of the art about the study of the interactions between CTCs and the immune system. We intend to analyze the impact that the cells of the immune system have in limiting or promoting the metastatic capability of CTCs. To this purpose, we will examine studies that correlate CTCs, immune cells, and patient prognosis, and we will also discuss relevant animal models that have contributed to the understanding of the mechanisms of immune-mediated metastasis. We will then consider some studies in which CTCs seem to play a promising role in monitoring cancer patients during immunotherapy regimens. We believe that, from an accurate and profound knowledge of the interactions between CTCs and the immune system, new immunotherapeutic strategies against cancer might emerge in the future.

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.

Resistance to anticancer immunity in cancer patients: potential strategies to reverse resistance

In the 1990s, the application of immunotherapy approaches to target cancer cells resulted in significant clinical responses in patients with advanced malignancies who were refractory to conventional therapies. While early immunotherapeutics were focused on T cell-mediated cytotoxic activity, subsequent efforts were centered on targeted antibody-mediated anticancer therapy. The initial success with antibody therapy encouraged further studies and, consequently, there are now more than 25 FDA-approved antibodies directed against a range of targets. Although both T cell and antibody therapies continue to result in significant clinical responses with minimal toxicity, a significant subset of patients does not respond to immunotherapy and another subset develops resistance following an initial response. This review is focused on describing examples showing that cancer resistance to immunotherapies indeed occurs. In addition, it reviews the mechanisms being used to overcome the resistance to immunotherapies by targeting the tumor cell directly and/or the tumor microenvironment.

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.

Circulating and disseminated tumour cells - mechanisms of immune surveillance and escape

Metastatic spread of tumour cells is the main cause of cancer-related deaths. Understanding the mechanisms of tumour-cell dissemination has, therefore, become an important focus for cancer research. In patients with cancer, disseminated cancer cells are often detectable in the peripheral blood as circulating tumour cells (CTCs) and in the bone marrow or lymph nodes as disseminated tumour cells (DTCs). The identification and characterization of CTCs and DTCs has yielded important insights into the mechanisms of metastasis, resulting in a better understanding of the molecular alterations and profiles underlying drug resistance. Given the expanding role of immunotherapies in the treatment of cancer, interactions between tumour cells and immune cells are the subject of intense research. Theoretically, cancer cells that exit the primary tumour site - leaving the protection of the typically immunosuppressive tumour microenvironment - will be more vulnerable to attack by immune effector cells; thus, the survival of tumour cells after dissemination might be the 'Achilles' heel' of metastatic progression. In this Review, we discuss findings relating to the interactions of CTCs and DTCs with the immune system, in the context of cancer immuno-editing, evasion from immune surveillance, and formation of metastases.

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.

Onto better TRAILs for cancer treatment

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), also known as Apo-2 ligand (Apo2L), is a member of the TNF cytokine superfamily. By cross-linking TRAIL-Receptor (TRAIL-R) 1 or TRAIL-R2, also known as death receptors 4 and 5 (DR4 and DR5), TRAIL has the capability to induce apoptosis in a wide variety of tumor cells while sparing vital normal cells. The discovery of this unique property among TNF superfamily members laid the foundation for testing the clinical potential of TRAIL-R-targeting therapies in the cancer clinic. To date, two of these therapeutic strategies have been tested clinically: (i) recombinant human TRAIL and (ii) antibodies directed against TRAIL-R1 or TRAIL-R2. Unfortunately, however, these TRAIL-R agonists have basically failed as most human tumors are resistant to apoptosis induction by them. It recently emerged that this is largely due to the poor agonistic activity of these agents. Consequently, novel TRAIL-R-targeting agents with increased bioactivity are currently being developed with the aim of rendering TRAIL-based therapies more active. This review summarizes these second-generation novel formulations of TRAIL and other TRAIL-R agonists, which exhibit enhanced cytotoxic capacity toward cancer cells, thereby providing the potential of being more effective when applied clinically than first-generation TRAIL-R agonists.

Reprogramming the tumor microenvironment: tumor-induced immunosuppressive factors paralyze T cells

It has become evident that tumor-induced immuno-suppressive factors in the tumor microenvironment play a major role in suppressing normal functions of effector T cells. These factors serve as hurdles that limit the therapeutic potential of cancer immunotherapies. This review focuses on illustrating the molecular mechanisms of immunosuppression in the tumor microenvironment, including evasion of T-cell recognition, interference with T-cell trafficking, metabolism, and functions, induction of resistance to T-cell killing, and apoptosis of T cells. A better understanding of these mechanisms may help in the development of strategies to enhance the effectiveness of cancer immunotherapies.

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.

Melanoma-educated CD14+ cells acquire a myeloid-derived suppressor cell phenotype through COX-2-dependent mechanisms

Tumors can suppress the host immune system by employing a variety of cellular immune modulators, such as regulatory T cells, tumor-associated macrophages, and myeloid-derived suppressor cells (MDSC). In the peripheral blood of patients with advanced stage melanoma, there is an accumulation of CD14(+)HLA-DR(lo/-) MDSC that suppress autologous T cells ex vivo in a STAT-3-dependent manner. However, a precise mechanistic basis underlying this effect is unclear, particularly with regard to whether the MDSC induction mechanism relies on cell-cell contact of melanoma cells with CD14(+) cells. Here, we show that early-passage human melanoma cells induce phenotypic changes in CD14(+) monocytes, leading them to resemble MDSCs characterized in patients with advanced stage melanoma. These MDSC-like cells potently suppress autologous T-cell proliferation and IFN-γ production. Notably, induction of myeloid-suppressive functions requires contact or close proximity between monocytes and tumor cells. Further, this induction is largely dependent on production of cyclooxygenase-2 (COX-2) because its inhibition in these MDSC-like cells limits their ability to suppress T-cell function. We confirmed our findings with CD14(+) cells isolated from patients with advanced stage melanoma, which inhibited autologous T cells in a manner relying up prostaglandin E2 (PGE2), STAT-3, and superoxide. Indeed, PGE2 was sufficient to confer to monocytes the ability to suppress proliferation and IFN-γ production by autologous T cells ex vivo. In summary, our results reveal how immune suppression by MDSC can be initiated in the tumor microenvironment of human melanoma.

Prevalence of heterotypic tumor/immune cell-in-cell structure in vitro and in vivo leading to formation of aneuploidy

Cell-in-cell structures refer to a unique phenomenon that one living cell enters into another living cell intactly, occurring between homotypic tumor cells or tumor (or other tissue cells) and immune cells (named as heterotypic cell-in-cell structure). In the present study, through a large scale of survey we observed that heterotypic cell-in-cell structure formation occurred commonly in vitro with host cells derived from different human carcinomas as well as xenotypic mouse tumor cell lines. Most of the lineages of human immune cells, including T, B, NK cells, monocytes as well as in vitro activated LAK cells, were able to invade tumor cell lines. Poorly differentiated stem cells were capable of internalizing immune cells as well. More significantly, heterotypic tumor/immune cell-in-cell structures were observed in a higher frequency in tumor-derived tissues than those in adjacent tissues. In mouse hepatitis models, heterotypic immune cell/hepatocyte cell-in-cell structures were also formed in a higher frequency than in normal controls. After in vitro culture, different forms of internalized immune cells in heterotypic cell-in-cell structures were observed, with one or multiple immune cells inside host cells undergoing resting, degradation or mitosis. More strikingly, some internalized immune cells penetrated directly into the nucleus of target cells. Multinuclear cells with aneuploid nucleus were formed in target tumor cells after internalizing immune cells as well as in situ tumor regions. Therefore, with the prevalence of heterotypic cell-in-cell structures observed, we suggest that shielding of immune cells inside tumor or inflammatory tissue cells implies the formation of aneuploidy with the increased multinucleation as well as fine-tuning of microenvironment under pathological status, which may define distinct mechanisms to influence the etiology and progress of tumors.

Soluble FAS in the prediction of benefit from cetuximab and irinotecan for patients with advanced colorectal cancer

The FAS/FASL system, comprising membrane-bound (mFAS and mFASL) and soluble forms (sFAS and sFASL), has been related to apoptosis driven by chemotherapy administration. In vitro experiments show chemotherapy upregulating membrane-bound forms, leading to an increase of receptor availability (at 24-72 h) and favoring apoptosis. The regulatory effect of chemotherapy on sFAS in patients has never been explored prospectively in advanced colorectal cancer (ACRC). We performed a pharmacodynamic study to address sFAS/sFASL variation. A prospective phase II translational multicenter study was designed to evaluate progression-free rate (PFR) in patients with ACRC treated with irinotecan and cetuximab in third-line therapy. The effect of sFAS was studied in vitro in colorectal cancer cell lines. Our results showed that statistically significant changes were observed in sFAS at 24-72 h compared to baseline levels in the pharmacodynamic study. Of the 93 patients enrolled in the prospective study in third-line therapy with cetuximab-irinotecan, 85 were evaluated for sFAS/sFASL changes at 48 h. There was no difference in PFR at 4 months between patients with sFAS and sFASL changes. In vitro analysis showed that although LoVo cell lines were sensitive to oxaliplatin and fluorouracil due to modulation of sFAS and FAS, HT29 lines were not. In summary, chemotherapy regulates FAS soluble fractions in vitro and in vivo, but does not predict PFR in ACRC patients undergoing third-line therapy with the combination of cetuximab and irinotecan.

P2X7 signaling promotes microsphere embolism-triggered microglia activation by maintaining elevation of Fas ligand

Background

The cerebral microvascular occlusion elicits microvascular injury which mimics the different degrees of stroke severity observed in patients, but the mechanisms underlying these embolic injuries are far from understood. The Fas ligand (FasL)-Fas system has been implicated in a number of pathogenic states. Here, we examined the contribution of microglia-derived FasL to brain inflammatory injury, with a focus on the potential to suppress the FasL increase by inhibition of the P2X₇-FasL signaling with pharmacological or genetic approaches during ischemia.

Methods

The cerebral microvascular occlusion was induced by microsphere injection in experimental animals. Morphological changes in microglial cells were studied immunohistochemically. The biochemical analyses were used to examine the intracellular changes of P2X₇/FasL signaling. The BV-2 cells and primary microglia from mice genetically deficient in P2X₇ were used to further establish a linkage between microglia activation and FasL overproduction.

Results

The FasL expression was continuously elevated and was spatiotemporally related to microglia activation following microsphere embolism. Notably, P2X₇ expression concomitantly increased in microglia and presented a distribution pattern that was similar to that of FasL in ED1-positive cells at pathological process of microsphere embolism. Interestingly, FasL generation in cultured microglia cells subjected to oxygen-glucose deprivation-treated neuron-conditioned medium was prevented by the silencing of P2X₇. Furthermore, FasL induced the migration of BV-2 microglia, whereas the neutralization of FasL with a blocking antibody was highly effective in inhibiting ischemia-induced microglial mobility. Similar results were observed in primary microglia from wild-type mice or mice genetically deficient in P2X₇. Finally, the degrees of FasL overproduction and neuronal death were consistently reduced in P2X₇^−/− mice compared with wild-type littermates following microsphere embolism insult.

Conclusion

FasL functions as a key component of an immunoreactive response loop by recruiting microglia to the lesion sites through a P2X₇-dependent mechanism. The specific modulation of P2X₇/FasL signaling and aberrant microglial activation could provide therapeutic benefits in acute and subacute phase of cerebral microembolic injury.

Cell surface delivery of TRAIL strongly augments the tumoricidal activity of T cells

PURPOSE

Adoptive T-cell therapy generally fails to induce meaningful anticancer responses in patients with solid tumors. Here, we present a novel strategy designed to selectively enhance the tumoricidal activity of T cells by targeted delivery of TNF-related apoptosis-inducing ligand (TRAIL) to the T-cell surface.

EXPERIMENTAL DESIGN

We constructed two recombinant fusion proteins, anti-CD3:TRAIL and K12:TRAIL. Tumoricidal activity of T cells in the presence of these fusion proteins was assessed in solid tumor cell lines, primary patient-derived malignant cells, and in a murine xenograft model.

RESULTS

When added to T cells, K12:TRAIL and anti-CD3:TRAIL selectively bind to the T-cell surface antigens CD3 and CD7, respectively, leading to cell surface accretion of TRAIL. Subsequently, anti-CD3:TRAIL and K12:TRAIL increased the tumoricidal activity of T cells toward cancer cell lines and primary patient-derived malignant cells by more than 500-fold. Furthermore, T-cell surface delivery of TRAIL strongly inhibited tumor growth and increased survival time of xenografted mice more than 6-fold.

CONCLUSIONS

Targeted delivery of TRAIL to cell surface antigens of T cells potently enhances the tumoricidal activity of T cells. This approach may be generally applicable to enhance the efficacy of adoptive T-cell therapy.

Palmitoylation of human FasL modulates its cell death-inducing function

Fas ligand (FasL) is a transmembrane protein that regulates cell death in Fas-bearing cells. FasL-mediated cell death is essential for immune system homeostasis and the elimination of viral or transformed cells. Because of its potent cytotoxic activity, FasL expression at the cell surface is tightly regulated, for example, via processing by ADAM10 and SPPL2a generating soluble FasL and the intracellular fragments APL (ADAM10-processed FasL form) and SPA (SPPL2a-processed APL). In this study, we report that FasL processing by ADAM10 counteracts Fas-mediated cell death and is strictly regulated by membrane localization, interactions and modifications of FasL. According to our observations, FasL processing occurs preferentially within cholesterol and sphingolipid-rich nanodomains (rafts) where efficient Fas–FasL contact occurs, Fas receptor and FasL interaction is also required for efficient FasL processing, and FasL palmitoylation, which occurs within its transmembrane domain, is critical for efficient FasL-mediated killing and FasL processing.

Influence of immune privilege on ocular tumor development

Mechanisms that maintain ocular immune privilege may contribute to ocular tumor progression by inhibiting tumoricidal immune responses. Consistent with that notion are observations from transplantable tumor models in mice demonstrating that the tumoricidal activity of CD8(+) cytolytic T lymphocytes (CTL) may be inhibited directly by interfering with CTL effector function in the eye or indirectly by abrogating the effector function of CD8+ T cell-activated intratumoral macrophages that are critical for ocular tumor rejection. In addition, epigenetic gene regulation by factors within the ocular tumor environment favors the generation of tumor variants that are resistant to CD8(+) CTL. Intratumoral macrophages may be essential for eliminating these variants because, unlike CTL, their tumoricidal activity is nonspecific. Hence, the inhibition of macrophage effector function within the eye, presumably to preserve immune privilege by minimizing ocular immunopathology, may hasten the outgrowth of tumor escape variants which contributes to ocular tumor progression.

Tumour-mediated TRAIL-Receptor expression indicates effective apoptotic depletion of infiltrating CD8+ immune cells in clinical colorectal cancer

Expression of apoptosis-related proteins on tumour cells has been shown in several experimental models to be an efficient mechanism for a counterattack against host anti-tumour immune responses in solid tumours. Here we provide a clinical evidence for such a tumour immune escape mechanism by demonstrating tumour to T cell-directed death receptor signalling (TRAIL/TRAIL-Receptor (TRAIL-R)) in colorectal cancer (CRC). In a series of patients with CRC and completed 5-year follow up, we investigated apoptosis and expression levels of apoptosis-related proteins. Gene and protein profiles in the tumours demonstrated intratumoural upregulated gene expression for Fas, Fas-L, TRAIL, TRAIL-R and TNF-alpha (RT-qPCR). Levels of terminaldeoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick-end labelling (TUNEL)-positive events were positively correlated with TRAIL-R1-expression on tumour infiltrating immune cells. Among the immune cells, preferentially CD8+ T cells were found to express TRAIL-R1 while serial immunostaining in the same patient tumours showed abundant apoptotic (TUNEL-positive) immune cells. In conclusion, our results in tumour samples from CRC patients suggest TRAIL-R1-mediated apoptotic depletion of infiltrating immune cells (CD8+) in response to TRAIL expression by the tumour itself. This supports the notion of an efficient escape from tumour immune response and thus evasion from the attack of activated CD8+ T cells. These findings may enhance our understanding of tumour progression in CRC and might be helpful for the development of TRAIL and its death receptor-based therapy.

[Dissecting the pathways of tumour escape: " question of life and death?"]

Apoptotic pathways are providing important saveguard mechanisms in protection from cancer by eliminating altered and often harmful cells. The disturbances of cell proliferation, differentiation and apoptosis are also found on specific signal-transduction pathways within the tumour cells and between these and the immune system. The article focuses attention on the evolution of the melanocytic naevi in the direction of a dysplastic or tumour cell. The determination of single molecules as prognostic parameters within cancer genesis seems to be problematic. New hopes are being placed on the treatment with TW-37, ABT-737 and TAT-Bim, which, to an extent, are able to support the programmed cell death. The clinical importance of these innovative therapies remains to be seen and should therefore, be viewed with considerable criticism.

Immunogene therapy against colon cancer metastasis using an adenovirus vector expressing CD40 ligand

BACKGROUND

Colon cancer is one of the most common cancers worldwide, and liver metastasis is a poor prognostic factor for all types of digestive cancers, including colon cancer. We studied CD40 ligand (CD40L)-mediated immunogene therapy for metastatic liver cancer in rats.

METHODS

We studied whether in vitro infection of a rat colon cancer cell line (RCN9) with an adenoviral-vector that expresses the CD40L (AxCAmCD40L) induced CD40L expression. In vivo to confirm the antitumor effect induced by AxCAmCD40L, the tumor cells that had been transduced by AxCAmCD40L were implanted into the subcutaneous tissues of syngenic rats (prevention model) or AxCAmCD40L was injected into the tumor tissues of the rats (treatment model). Furthermore, immune cells including NK cells, cytotoxic T cells, and tumor-specific antibodies induced by AxCAmCD40L were examined.

RESULTS

Immunogene therapy using AxCAmCD40L suppressed the tumor growth strongly or reduced tumor size in the prevention model and treatment model. NK cells, cytotoxic T cells, and tumor-specific antibodies contributed to this antitumor effect in both groups.

CONCLUSION

These observations suggest that CD40L-mediated immunogene therapy for metastatic colon cancer in the liver and lungs is effective and is mediated by the activation of both the cellular and humoral immune systems.

Clinical significance of Fas and FasL protein expression in gastric carcinoma and local lymph node tissues

AIM: To investigate the relation of Fas and Fas ligand (FasL) protein expression with carcinogenesis and metastasis of gastric carcinoma.

METHODS: Immunohistochemistry was used to detect Fas and FasL protein expression in 64 gastric carcinoma tissue samples and 20 normal gastric tissue samples. Relation between FasL and Fas expression, age and gender of gastric cancer patients, and pathological subtype and lymph node metastasis of gastric cancer was analyzed.

RESULTS: The Fas expression level was significantly higher in normal gastric tissue samples than in gastric carcinoma tissue samples (85.0% vs 25.0%, P < 0.001), while the FasL expression level was significantly lower in normal gastric tissue samples than in gastric carcinoma tissue samples (30.0% vs 81.3%, P < 0.001). The Fas expression level was significantly higher in invasive lymph nodes than in non-invasive lymph nodes (82.9% vs 56.5%, P < 0.003) and in well-differentiated gastric carcinoma tissue samples than in poorly-differentiated gastric carcinoma tissue samples (50.0% vs 18.0%, P = 0.015). The FasL expression level was significantly lower in well-differentiated gastric carcinoma tissue samples than in poorly- differentiated gastric carcinoma tissue samples (42.9% vs 84.0%, P = 0.021). The Fas and FasL expression levels (25.0% and 81.3%) were significantly different in gastric carcinoma tissue samples (P < 0.001), but had a non-linear correlation (P = 0.575).

CONCLUSION: Abnormal Fas and FasL expressions in gastric carcinoma and lymph node tissues are involved in carcinogenesis and metastasis of gastric cancer.

Personalizing Stem Cell Research and Therapy: The Arduous Road Ahead or Missed Opportunity?

The euphoria of stem cell therapy has diminished, allowing scientists, clinicians and the general public to seriously re-examine how and what types of stem cells would effectively repair damaged tissue, prevent further tissue damage and/or replace lost cells. Importantly, there is a growing recognition that there are substantial person-to-person differences in the outcome of stem cell therapy. Even though the small molecule pharmaceuticals have long remained a primary focus of the personalized medicine research, individualized or targeted use of stem cells to suit a particular individual could help forecast potential failures of the therapy or identify, early on, the individuals who might benefit from stem cell interventions. This would however demand collaboration among several specialties such as pharmacology, immunology, genomics and transplantation medicine. Such transdisciplinary work could also inform how best to achieve efficient and predictable stem cell migration to sites of tissue damage, thereby facilitating tissue repair. This paper discusses the possibility of polarizing immune responses to rationalize and individualize therapy with stem cell interventions, since generalized "one-size-fits-all" therapy is difficult to achieve in the face of the diverse complexities posed by stem cell biology. We also present the challenges to stem cell delivery in the context of the host related factors. Although we focus on the mesenchymal stem cells in this paper, the overarching rationale can be extrapolated to other types of stem cells as well. Hence, the broader purpose of this paper is to initiate a dialogue within the personalized medicine community by expanding the scope of inquiry in the field from pharmaceuticals to stem cells and related cell-based health interventions.

Antitumor immunity and cancer stem cells

Self-renewing cancer stem cells (CSC) capable of spawning more differentiated tumor cell progeny are required for tumorigenesis and neoplastic progression of leukemias and several solid cancers. The mechanisms by which CSC cause tumor initiation and growth are currently unknown. Recent findings that suggest a negative correlation between degrees of host immunocompetence and rates of cancer development raise the possibility that only a restricted minority of malignant cells, namely CSC, may possess the phenotypic and functional characteristics to evade host antitumor immunity. In human malignant melanoma, a highly immunogenic cancer, we recently identified malignant melanoma initiating cells (MMIC), a novel type of CSC, based on selective expression of the chemoresistance mediator ABCB5. Here we present evidence of a relative immune privilege of ABCB5(+) MMIC, suggesting refractoriness to current immunotherapeutic treatment strategies. We discuss our findings in the context of established immunomodulatory functions of physiologic stem cells and in relation to mechanisms responsible for the downregulation of immune responses against tumors. We propose that the MMIC subset might be responsible for melanoma immune evasion and that immunomodulation might represent one mechanism by which CSC advance tumorigenic growth and resistance to immunotherapy. Accordingly, the possibility of an MMIC-driven tumor escape from immune-mediated rejection has important implications for current melanoma immunotherapy.

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.

Increased levels of soluble CD226 in sera accompanied by decreased membrane CD226 expression on peripheral blood mononuclear cells from cancer patients

Background

As a cellular membrane triggering receptor, CD226 is involved in the NK cell- or CTL-mediated lysis of tumor cells of different origin, including freshly isolated tumor cells and tumor cell lines. Here, we evaluated soluble CD226 (sCD226) levels in sera, and membrane CD226 (mCD226) expression on peripheral blood mononuclear cells (PBMC) from cancer patients as well as normal subjects, and demonstrated the possible function and origin of the altered sCD226, which may provide useful information for understanding the mechanisms of tumor escape and for immunodiagnosis and immunotherapy.

Results

Soluble CD226 levels in serum samples from cancer patients were significantly higher than those in healthy individuals (P < 0.001), while cancer patients exhibited lower PBMC mCD226 expression than healthy individuals (P < 0.001). CD226-Fc fusion protein could significantly inhibit the cytotoxicity of NK cells against K562 cells in a dose-dependent manner. Furthermore, three kinds of protease inhibitors could notably increase mCD226 expression on PMA-stimulated PBMCs and Jurkat cells with a decrease in the sCD226 level in the cell culture supernatant.

Conclusion

These findings suggest that sCD226 might be shed from cell membranes by certain proteases, and, further, sCD226 may be used as a predictor for monitoring cancer, and more important, a possible immunotherapy target, which may be useful in clinical application.

Adenovirus-mediated CD40L gene therapy induced both humoral and cellular immunity against rat model of hepatocellular carcinoma

Adenoviral-vector expressing CD40L (AxCAmCD40L)-mediated gene therapy was studied for treatment of hepatocellular carcinoma (HCC) using CD40 ligand (CD40L) complementary DNA in rats. The particular focus was whether humoral immunity took part in antitumor effect. When tumor cells transduced by AxCAmCD40L were implanted into the subcutaneous tissues of syngeneic rats, the tumor growth was suppressed. Intratumoral injection of AxCAmCD40L to pre-existing tumor in rats also led to significant reduction of tumor size. When tumor cells were re-implanted to prevention model rats and treatment model rats, no tumor growth was observed. Many studies to date have reported that cellular immunity induces antitumor immunity. However, the present study demonstrated that not only cellular immunity but also humoral immunity plays an essential role in a HCC model. These observations suggested that CD40L-mediated immune gene therapy for HCC was very effective treatment by activation of both cellular and humoral immune system.

Apoptosis and pathogenesis of melanoma and nonmelanoma skin cancer

Skin cancers, i.e., basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and melanoma, belong to the most frequent tumors. Their formation is based on constitutional and/or inherited factors usually combined with environmental factors, mainly UV-irradiation through long term sun exposure. UV-light can randomly induce DNA damage in keratinocytes, but it can also mutate genes essential for control and surveillance in the skin epidermis. Various repair and safety mechanisms exist to maintain the integrity of the skin epidermis. For example, UV-light damaged DNA is repaired and if this is not possible, the DNA damaged cells are eliminated by apoptosis (sunburn cells). This occurs under the control of the p53 suppressor gene. Fas-ligand (FasL), a member of the tumor necrosis superfamily, which is preferentially expressed in the basal layer of the skin epidermis, is a key surveillance molecule involved in the elimination of sunburn cells, but also in the prevention of cell transformation. However, UV light exposure downregulates FasL expression in keratinocytes and melanocytes leading to the loss of its sensor function. This increases the risk that transformed cells are not eliminated anymore. Moreover, important control and surveillance genes can also be directly affected by UV-light. Mutation in the p53 gene is the starting point for the formation of SCC and some forms of BCC. Other BCCs originate through UV light mediated mutations of genes of the hedgehog signaling pathway which are essential for the maintainance of cell growth and differentiation. The transcription factor Gli2 plays a key role within this pathway, indeed, Gli2 is responsible for the marked apoptosis resistance of the BCCs. The formation of malignant melanoma is very complex. Melanocytes form nevi and from the nevi melanoma can develop through mutations in various genes. Once the keratinocytes or melanocytes have been transformed they re-express FasL which may allow the expanding tumor to evade the attack of immune effector cells. FasL which is involved in immune evasion or genes which govern the apoptosis resistance, e.g., Gli2 could therefore be prime targets to prevent tumor formation and growth. Attempts to silence these genes by RNA interference using gene specific short interfering RNAs (siRNAs) or short hairpin RNAs (shRNAs) have been functionally successful not only in tissue cultures and tumor tissues, but also in a mouse model. Thus, siRNAs and/or shRNAs may become a novel and promising approach to treat skin cancers at an early stage.

Down-regulation of mcl-1 by small interfering RNA sensitizes resistant melanoma cells to fas-mediated apoptosis

Resistance of malignant melanoma cells to Fas-mediated apoptosis is among the mechanisms by which they escape immune surveillance. However, the mechanisms contributing to their resistance are not completely understood, and it is still unclear whether antiapoptotic Bcl-2-related family proteins play a role in this resistance. In this study, we report that treatment of Fas-resistant melanoma cell lines with cycloheximide, a general inhibitor of de novo protein synthesis, sensitizes them to anti-Fas monoclonal antibody (mAb)-induced apoptosis. The cycloheximide-induced sensitization to Fas-induced apoptosis is associated with a rapid down-regulation of Mcl-1 protein levels, but not that of Bcl-2 or Bcl-xL. Targeting Mcl-1 in these melanoma cell lines with specific small interfering RNA was sufficient to sensitize them to both anti-Fas mAb-induced apoptosis and activation of caspase-9. Furthermore, ectopic expression of Mcl-1 in a Fas-sensitive melanoma cell line rescues the cells from Fas-mediated apoptosis. Our results further show that the expression of Mcl-1 in melanoma cells is regulated by the mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) and not by phosphatidylinositol 3-kinase/AKT signaling pathway. Inhibition of ERK signaling with the mitogen-activated protein/ERK kinase-1 inhibitor or by expressing a dominant negative form of mitogen-activated protein/ERK kinase-1 also sensitizes resistant melanoma cells to anti-Fas mAb-induced apoptosis. Thus, our study identifies mitogen-activated protein kinase/ERK/Mcl-1 as an important survival signaling pathway in the resistance of melanoma cells to Fas-mediated apoptosis and suggests that its targeting may contribute to the elimination of melanoma tumors by the immune system.

Immunosuppressive mechanisms in human tumors: why we still cannot cure cancer

Tumor cells often evoke specific immune responses that, however, fail to eliminate all the tumor cells. The development of cancer immunotherapies is, therefore, mostly focused on the generation of large numbers of activated anti-tumor effector cells by vaccination or adoptive T cell transfer. These developments are built on an ever-extended list of identified tumor-associated antigens and corresponding T cell epitopes, and a steady flow of reports from proof-of-principle animal model experiments demonstrating cure from disease by immune interventions. However, the promises have not translated into clinical successes for cancer patients. Even where tumor regression or complete responses were achieved there is usually relapse of the disease. Increasing numbers of reports over recent years highlight potential immunosuppressive mechanisms that act in tumors and systemically in cancer patients to block effective anti-tumor immune responses. They account in large parts for the failures of cancer immunotherapy and need to be overcome before progress can be expected. We review here the current state of the research on immunosuppressive networks in human cancer.

Dynamic cross-talk between tumor and immune cells in orchestrating the immunosuppressive network at the tumor microenvironment

Accumulating evidence indicates that a dynamic cross-talk between tumors and the immune system can regulate tumor growth and metastasis. Increased understanding of the biochemical nature of tumor antigens and the molecular mechanisms responsible for innate and adaptive immune cell activation has revolutionized the fields of tumor immunology and immunotherapy. Both the protective effects of the immune system against tumor cells (immunosurveillance) and the evasion of tumor cells from immune attack (tumor-immune escape) have led to the concept of cancer immunoediting, a proposal which infers that a bidirectional interaction between tumor and inflammatory/regulatory cells is ultimately responsible for orchestrating the immunosuppressive network at the tumor site. In this context, a major challenge is the potentiation or redirection of tumor antigen-specific immune responses. The success in reaching this goal is highly dependent on an improved understanding of the interactions and mechanisms operating during the different phases of the cancer immunoediting process. In this review, we discuss the multiple defense and counterattack strategies that tumors have devised in order to evade immune attack and to thwart the effectiveness of several immunotherapeutic approaches.

Presence and phenotype of dendritic cells in uveal melanoma

BACKGROUND

Uveal melanoma arises in an immune-privileged site and can itself add to the immunosuppressive environment. Previous studies on cutaneous melanoma have shown the presence of tolerogenic dendritic cells (DCs), which could play an important role in the progression of the tumour.

AIM

To examine the presence and functional status of DCs in a small series of uveal melanomas.

METHODS

10 cases of uveal melanoma were examined for the expression of FXIIIa, CD68, human leucocyte antigen (HLA)-DR, CD40, CD83, transforming growth factor betaR1 and indolamine 2,3 dioxygenase by immunohistochemical analysis on sections embedded in paraffin wax.

RESULTS

CD68-positive macrophages were present in all of the tumours and were evenly distributed throughout. DCs expressing FXIIIa-positive were seen in 7 cases, and were often found concentrated in foci within the tumour mass. These cells were dendritic and expressed high levels of HLA-DR. The DCs did not express the maturation markers CD83 or CD40. In one case, concentration of DCs around the area of tumour necrosis was observed, and some of these cells expressed CD83.

CONCLUSION

Numerous tolerising antigen-presenting cells may play a role in melanoma-related immunosuppression in the eye, although activation of DCs may be associated with tumour necrosis.

Multifaceted targeting in cancer: the recent cell death players meet the usual oncogene suspects

Recent complicated advances towards the blueprinting of the altered molecular networks that lie behind cancer development have paved the way for targeted therapy in cancer. This directed a significant part of the research community to the development of specialized targeted agents, many of which are already available or in clinical trials. The prospect of patient-tailored therapeutic strategies, although very close to becoming a reality also raises the level of complexity of the therapeutic approach. This review summarizes the functions, in vivo expression patterns and aberrations of factors presently targeted or representing potential targets by therapeutic agents, focusing on those implicated in death receptor-induced apoptosis. The authors overview the regulation of these factors and death receptor-induced apoptosis by classical oncogenes (e.g., RAS, MYC, HER2) and their effectors/regulators, most of which are also being targeted. In addition, the importance of orthologic systemic approaches in future patient-tailored therapies are discussed.

Retinoic acid elicits cytostatic, cytotoxic and immunomodulatory effects on uveal melanoma cells

The current therapy of uveal melanoma (UM) metastases remains inefficient, which warrants the development of new treatment modalities. For the first time we investigated the effects of retinoic acid (RA) on a panel of UM cell lines and found that RA induces morphological changes compatible with differentiation, suppresses proliferation and causes apoptosis in these cells. RA treatment resulted in an increase of p21, p27 and p53 protein levels and G1 arrest in UM cells, which correlated with significant down-modulation of surface Her2/neu proto-oncogene expression. In addition, RA-treated UM cells exhibited increased sensitivity to both MHC class I-restricted killing by cytotoxic T lymphocytes and NK cell-mediated lysis that were accompanied by more efficient conjugate formation between UM cells and killer lymphocytes. Taken together, our results implicate UM as a new target for treatment with retinoids and suggest that retinoids and T- or NK-cell based immunotherapy can have mutually enhancing effects in UM patients.

Cytotoxic T Lymphocytes Induce Caspase-Dependent and -Independent Cell Death in Neuroblastomas in a MHC-Nonrestricted Fashion

The MHC class I- restricted processing and presentation pathway is frequently nonfunctional in tumor cells; therefore, the direct targeting of tumor cells by CTLs may be difficult, if at all possible, to achieve. We used neuroblastoma (NB), which represents a striking example of a tumor with an impaired MHC class I pathway, as a model to study bystander effects of activated T lymphocytes on tumor cells. We found that NB cell lines are susceptible to killing by differentiated CD8(+) CTL clones in a MHC class I-nonrestricted manner that involves two programs of cell death distinguished on the basis of different kinetics, sensitivities to caspase inhibitors, and cytokine-blocking reagents. The "early" death exhibited characteristic features of apoptosis, whereas the "delayed" caspase-independent death exhibited features associated with necrosis and was partially inhibited by TNF-alpha-blocking and prevented by overexpression of Bcl-2 or Bcl-x(L). Our data reveal a previously unappreciated complexity of death pathways induced in tumor cells by immune activation and suggest that redirecting nonspecific effector CTLs to even a small proportion of NB cells or activating CTLs in a tumor's proximity may have therapeutic effects in patients with NB.

Protective mechanisms of head and neck squamous cell carcinomas from immune assault

Head and neck squamous cell carcinoma (HNSCC) is an aggressive malignancy that is the sixth most common neoplasm in the world. Despite advances in treatments involving surgery, radiation, and chemotherapy, the 5-year survival has remained at less than 50% for the past 30 years, primarily because of local recurrences. Thus, the possibility of immunotherapeutic approaches for patients with HNSCC has gained interest. Unfortunately, patients with HNSCC have profound immune defects that are associated with increased recurrence. This review aims to provide an overview of both the defensive and immune subversive mechanisms by which patients with HNSCC can protect themselves from immune antitumor assault.

Tumor-driven evolution of immunosuppressive networks during malignant progression

Tumors evolve mechanisms to escape immune control by a process called immune editing, which provides a selective pressure in the tumor microenvironment that could lead to malignant progression. A variety of tumor-derived factors contribute to the emergence of complex local and regional immunosuppressive networks, including vascular endothelial growth factor, interleukin-10, transforming growth factor-beta, prostaglandin E(2), and soluble phosphatidylserine, soluble Fas, soluble Fas ligand, and soluble MHC class I-related chain A proteins. Although deposited at the primary tumor site, these secreted factors could extend immunosuppressive effects into the local lymph nodes and the spleen, promoting invasion and metastasis. Vascular endothelial growth factors play a key role in recruiting immature myeloid cells from the bone marrow to enrich the microenvironment as tumor-associated immature dendritic cells and tumor-associated macrophages. The understanding of the immunosuppressive networks that evolve is incomplete, but several features are emerging. Accumulation of tumor-associated immature dendritic cells may cause roving dendritic cells and T cells to become suppressed by the activation of indoleamine 2,3-dioxygenase and arginase I by tumor-derived growth factors. Soluble phosphatidylserines support tumor-associated macrophages by stimulating the release of anti-inflammatory mediators that block antitumor immune responses. Soluble Fas, soluble FasL, and soluble MHC class I-related chain A proteins may help tumor cells escape cytolysis by cytotoxic T cells and natural killer cells, possibly by counterattacking immune cells and causing their death. In summary, tumor-derived factors drive the evolution of an immunosuppressive network which ultimately extends immune evasion from the primary tumor site to peripheral sites in patients with cancer.

Immunosuppression in melanoma immunotherapy: potential opportunities for intervention

Although melanomas are substantially more immunogenic than other tumors, current immunotherapeutic approaches for melanoma patients have met with only limited success. Although melanoma-specific CD8+ T-cell responses can often be generated in patients naturally or through vaccination regimens, tumors frequently continue to grow unabated, suggesting that tumor-specific immune responses may be actively dampened in vivo. Research over the past decade has brought to light several mechanisms used by melanomas and other tumors to suppress tumor-specific immune responses. These include the presence of regulatory immune cells within the tumor microenvironment and draining lymph nodes that serve to shut down effector T-cell function. In addition, melanoma tumors themselves express a number of soluble and membrane-bound molecules that are responsible for inhibiting activated immune cells. The identification of these suppressive mechanisms has provided significant opportunities for designing novel therapeutic interventions that could augment current vaccination and adoptive transfer approaches for treatment of melanoma.

Polymorphisms of the FAS and FAS ligand genes associated with risk of cutaneous malignant melanoma

The FAS/FAS ligand (FASLG) system has a key role in regulating cell growth and thus tumorigenesis. Functional promoter polymorphisms of the FAS and FASLG genes alter the transcriptional activities, but no published study has investigated the role of these polymorphisms in the etiology of cutaneous malignant melanoma (CMM). In a hospital-based, case-control study of 602 non-Hispanic white CMM patients and 603 cancer-free age- and sex-matched control subjects, we genotyped FAS-1377G>A, FAS-670A>G, FASLG-844T>C and FASLG-IVS2nt-124G>A polymorphisms and assessed their respective associations with CMM risk. We found that an increased risk of CMM was associated with the FAS-1377GG [adjusted odds ratio (OR)=1.32; 95% confidence interval (CI)=1.00-1.75 for -1377GG] and -670AA (adjusted OR=1.28; 95% CI=1.00-1.65 for -670AA) genotypes compared to the -1377AA/AG and -670AG/GG genotypes, respectively; an increased risk of CMM was associated with the FASLG-IVS2nt-124AG+GG (OR=1.54; 95% CI=1.18-2.01) genotype compared to the AA genotype, but no evident risk was associated with any of the FAS-844T>C genotypes. In the combined analysis of these four variant alleles, we found that, compared to those having 0-3 variants, those having 4-8 variant alleles had a significantly increased risk for CMM (OR=1.38; 95% CI=1.10-1.73), and this risk was more pronounced in subgroups of old (>50 years) males, and those who were at low risk of sunlight-induced CMM, except for having fair skin colour, moles, dysplastic nevi and a family history of cancer. In conclusion, genetic variants in the FAS and FASLG genes may contribute to the etiology of CMM in the general population, particularly in those with a low risk of sunlight-induced CMM.

Shared biology of GVHD and GVT effects: Potential methods of separation

The difficult separation of clinical graft-versus-tumor (GVT) effects from graft-versus-host disease (GVHD) reflects their shared biology. Experimental approaches to mediate GVT effects while limiting GVHD include: (1) allograft T cell depletion followed by immune enhancement; (2) modulation of T cell dose or T cell subset composition; (3) donor lymphocyte infusion; (4) reduced-intensity host preparation; (5) modulation of Th1/Th2 and Tc1/Tc2 cell balance; (6) cytokine therapy or neutralization; (7) T regulatory cell therapy; (8) co-stimulatory pathway modulation; (9) chemokine pathway modulation; (10) induction of antigen-specific T cells; (11) alloreactive NK cell therapy; and (12) targeted pharmaceutical inhibition of proteosome, mammalian target of rapamycin, and histone deacetylase pathways. Clearly, a multitude of approaches exist that hold promise for separating GVT effects from GVHD. Future success in this endeavor will require a strong commitment towards translational research and continued advances in cell, vaccine, cytokine, monoclonal antibody, and targeted molecular therapy.

Dual treatment with COX-2 inhibitor and sodium arsenite leads to induction of surface Fas Ligand expression and Fas-Ligand-mediated apoptosis in human melanoma cells

Most human melanomas express Fas receptor on the cell surface, and treatment with exogenous Fas Ligand (FasL) efficiently induces apoptosis of these cells. In contrast, endogenous surface expression of FasL is suppressed in Fas-positive melanomas. We report here the use of a combination of sodium arsenite, an inhibitor of NF-kappaB activation, and NS398, a cyclooxygenase-2 (COX-2) inhibitor, for restoration of the surface FasL expression. We observed a large increase of Fas-mediated apoptosis in Fas-positive melanomas. This was due to induction of FasL surface expression and increased susceptibility to Fas death signaling after arsenite and NS398 treatment. Furthermore, silencing COX-2 expression by specific RNAi also effectively increased surface FasL expression following arsenite treatment. Upregulation of the surface FasL levels was based on an increase in the efficiency of translocation to the cell surface and stabilization of FasL protein on the cell surface, rather than on acceleration of the FasL gene transcription. Data obtained demonstrate that the combination of arsenite with inhibitors of COX-2 may affect the target cancer cells via induction of FasL-mediated death signaling.