Immune modulation by melanoma-derived factors

Regression in cutaneous melanoma: histological assessment, immune mechanisms and clinical implications

Tumour regression is an immunologically driven process that results in complete or partial disappearance of tumour cells. This can be observed in histological sections as replacement of tumour cells with fibrosis, angiogenesis, and a variable inflammatory infiltrate. In primary cutaneous melanoma, the prognostic significance of regression has been debated for decades, in part because inconsistent histological criteria are used in prognostication studies. It is broadly accepted that CD8+ T lymphocytes are the primary effectors of the anti-tumour response, but the interplay between melanoma and the immune system is complex, dynamic, and incompletely understood. Sustained progress in unravelling the pathogenesis of melanoma regression has led to the identification of therapeutic targets, culminating in the development of immune checkpoint inhibitors for the management of advanced disease. Modern techniques allow for high-resolution spatial analyses of the tumour microenvironment. Such studies may lead to better understanding of the immune drivers of melanoma regression, thereby facilitating the search for new prognostic and predictive biomarkers to assist clinical decision-making.

Helper Innate Lymphoid Cells-Unappreciated Players in Melanoma Therapy

Immune checkpoint inhibitors (ICIs) and targeted therapy have dramatically changed the outcome of metastatic melanoma patients. Although immune checkpoints were developed based on the biology of adaptive T cells, they have subsequently been shown to be expressed by other subsets of immune cells. Similarly, the immunomodulatory properties of targeted therapy have been studied primarily with respect to T lymphocytes, but other subsets of immune cells could be affected. Innate lymphoid cells (ILCs) are considered the innate counterpart of T lymphocytes and include cytotoxic natural killer cells, as well as three helper subsets, ILC1, ILC2 and ILC3. Thanks to their tissue distribution and their ability to respond rapidly to environmental stimuli, ILCs play a central role in shaping immunity. While the role of NK cells in melanoma physiopathology and therapy is well established, little is known about the other helper ILC subsets. In this review, we summarize recent findings on the ability of the melanoma TME to influence the phenotype and functional plasticity of helper ILCs and highlight how this subset may in turn shape the TME. We also discuss changes in the melanoma TME induced by targeted therapy that could affect helper ILC functions, the expression of immune checkpoints on this subset and how their inhibition by ICIs may modulate helper ILC function and contribute to therapeutic efficacy.

Silibinin induces immunogenic cell death in cancer cells and enhances the induced immunogenicity by chemotherapy

Introduction: Silibinin is a natural flavonoid compound known to induce apoptosis in cancer cells. Despite silibinin's safety and efficacy as an anticancer drug, its effects on inducing immunogenic cell death (ICD) are largely unknown. Herein, we have evaluated the stimulating effects of silibinin on ICD in cancer cells treated with silibinin alone or in combination with chemotherapy. Methods: The anticancer effect of silibinin, alone or in combination with doxorubicin or oxaliplatin (OXP), was assessed using the MTT assay. Compusyn software was used to analyze the combination therapy data. Western blotting was conducted to examine the level of STAT3 activity. Flow cytometry was used to analyze calreticulin (CRT) and apoptosis. The heat shock protein (HSP70), high mobility group box protein1 (HMGB1), and IL-12 levels were assessed by ELISA. Results: Compared to the negative control groups, silibinin induced ICD in CT26 and B16F10 cells and significantly enhanced the induction of this type of cell death by doxorubicin, and these changes were allied with substantial increases in the level of damage-associated molecular patterns (DAMPs) including CRT, HSP70, and HMGB1. Furthermore, conditioned media from cancer cells exposed to silibinin and doxorubicin was found to stimulate IL-12 secretion in dendritic cells (DCs), suggesting the link of this treatment with the induction of Th1 response. Silibinin did not augment the ICD response induced by OXP. Conclusion: Our findings showed that silibinin can induce ICD and it potentiates the induction of this type of cell death induced by chemotherapy in cancer cells.

Interferon-gamma signaling promotes melanoma progression and metastasis

Interferon-gamma (IFNG) has long been regarded as the flag-bearer for the anti-cancer immunosurveillance mechanisms. However, relatively recent studies have suggested a dual role of IFNG, albeit there is no direct experimental evidence for its potential pro-tumor functions. Here we provide in vivo evidence that treatment of mouse melanoma cell lines with Ifng enhances their tumorigenicity and metastasis in lung colonization allograft assays performed in immunocompetent syngeneic host mice, but not in immunocompromised host mice. We also show that this enhancement is dependent on downstream signaling via Stat1 but not Stat3, suggesting an oncogenic function of Stat1 in melanoma. The experimental results suggest that melanoma cell-specific Ifng signaling modulates the tumor microenvironment and its pro-tumorigenic effects are partially dependent on the γδ T cells, as Ifng-enhanced tumorigenesis was inhibited in the TCR-δ knockout mice. Overall, these results show that Ifng signaling may have tumor-promoting effects in melanoma by modulating the immune cell composition of the tumor microenvironment.

Chemokine Pathways in Cutaneous Melanoma: Their Modulation by Cancer and Exploitation by the Clinician

The incidence of cutaneous malignant melanoma is rising globally and is projected to continue to rise. Advances in immunotherapy over the last decade have demonstrated that manipulation of the immune cell compartment of tumours is a valuable weapon in the arsenal against cancer; however, limitations to treatment still exist. Cutaneous melanoma lesions feature a dense cell infiltrate, coordinated by chemokines, which control the positioning of all immune cells. Melanomas are able to use chemokine pathways to preferentially recruit cells, which aid their growth, survival, invasion and metastasis, and which enhance their ability to evade anticancer immune responses. Aside from this, chemokine signalling can directly influence angiogenesis, invasion, lymph node, and distal metastases, including epithelial to mesenchymal transition-like processes and transendothelial migration. Understanding the interplay of chemokines, cancer cells, and immune cells may uncover future avenues for melanoma therapy, namely: identifying biomarkers for patient stratification, augmenting the effect of current and emerging therapies, and designing specific treatments to target chemokine pathways, with the aim to reduce melanoma pathogenicity, metastatic potential, and enhance immune cell-mediated cancer killing. The chemokine network may provide selective and specific targets that, if included in current therapeutic regimens, harbour potential to improve outcomes for patients.

STAT3 inhibitory stattic enhances immunogenic cell death induced by chemotherapy in cancer cells

BACKGROUND

Induction of immunogenic cell death (ICD) is considered a promising strategy for cancer immunotherapy. Stattic is an inhibitor of STAT3, which is found constitutively active in many cancers and plays a major role in cancer progression.

OBJECTIVES

In the present study, we proposed to evaluate whether stattic can enhance the effects of chemotherapy in the induction of ICD in cancer cells harboring hyperactive STAT3.

METHODS

The growth inhibitory effects of stattic and chemo agents including doxorubicin (DOX) and oxaliplatin (OXP) were evaluated using MTT assay in B16F10 and CT26 cell lines. Flow cytometry was applied to study cell apoptosis and calreticulin (CRT) surface exposure. The levels of high mobility group box 1 (HGMB1), heat shock protein70 (HSP70) and interleukin-12 (IL-12) were measured using ELISA.

RESULTS

Treatment of B16F10 and CT26 cells with stattic in combination with DOX resulted in synergistic antitumor effects with combination index being 0.82 and 0.87, respectively. Interestingly, we found a higher level of ICD markers including CRT expression as well as HMGB1 and HSP70 secretion in the cells received combination therapy of stattic and DOX as compared with monotherapies. Moreover, exposure of dendritic cells (DCs) to conditioned media (CM) from cancer cells treated with stattic and/or DOX resulted in secretion of IL-12, which is an indicator of DCs maturation and induction of Th1 response. OXP and stattic monotherapy induced ICD in CT26 cells and stimulated IL-12 secretion by DCs; however, we did not observe a significant increase in the level of ICD in CT26 cells and IL-12 secretion by DCs when CT26 cells were treated with stattic and OXP combination as compared with monotherapy groups.

CONCLUSION

These findings indicate that STAT3 inhibitory stattic can increase ICD induced by DOX. Graphical abstract.

Racial Differences in Immunological Landscape Modifiers Contributing to Disparity in Prostate Cancer

Prostate cancer affects African Americans disproportionately by exhibiting greater incidence, rapid disease progression, and higher mortality when compared to their Caucasian counterparts. Additionally, standard treatment interventions do not achieve similar outcome in African Americans compared to Caucasian Americans, indicating differences in host factors contributing to racial disparity. African Americans have allelic variants and hyper-expression of genes that often lead to an immunosuppressive tumor microenvironment, possibly contributing to more aggressive tumors and poorer disease and therapeutic outcomes than Caucasians. In this review, we have discussed race-specific differences in external factors impacting internal milieu, which modify immunological topography as well as contribute to disparity in prostate cancer.

CAR-T cell therapy in melanoma: A future success story?

Chimeric antigen receptor (CAR)-T cells are one of the impressive recent success stories of anti-cancer immunotherapy. Especially in haematological malignancies, this treatment strategy has shown promising results leading to the recent approval of two CAR-T cell constructs targeting CD19 in the United States and the European Union. After the huge success in haematological cancers, the next step will be the evaluation of its efficacy in different solid tumors, which is currently investigated in preclinical as well as clinical settings. A commonly examined tumor model in the context of immunotherapy is melanoma, since it is known for its immunogenic features. However, the first results of CAR-T cell therapy in solid tumors did not reveal the same impressive outcomes that were observed in haematological malignancies, as engineered cells need to cope with several challenges. Obstacles include the lack of migration of CAR-T cells from blood vessels to the tumor site as well as the immunosuppressive tumor microenvironment within solid tumors. Another hurdle is posed by the identification of an ideal target antigen to avoid on-target/off-tumor toxicities. Regarding immune escape mechanisms, which can be developed by tumor cells to bypass immune recognition, the observation of antigen loss should also be considered. This article gives an overview of the challenges displayed in CAR-T cell therapy for the use in solid tumors and discusses different new strategies and approaches that deal with these problems in order to improve CAR-T cell therapy, particularly for its use in melanoma.

The disruption of hematopoiesis in tumor progression

Human adult hematopoiesis maintains homeostasis by replacing depleted progeny pools and inducing a primary immune response to infectious diseases and tumors. Recent studies have shown that tumor progression is associated with profound perturbations in hematopoiesis. Scientists have sought to clarify the complex mechanisms underlying the developmental fate of hematopoiesis by assessing hematopoietic stem and progenitor cells in various tumors. Results have shown that tumors disrupt normal hematopoiesis, resulting in extramedullary hematopoiesis and myeloid skewing. The key regulatory roles played by myeloid-derived suppressor cells induce immune suppression. Here, we summarize recent findings and discuss mechanisms underlying the disruption of hematopoiesis in solid tumors.

Unraveling the ECM-Immune Cell Crosstalk in Skin Diseases

The extracellular matrix (ECM) is a complex network of proteins and proteoglycans secreted by keratinocytes, fibroblasts and immune cells. The function of the skin ECM has expanded from being a scaffold that provides structural integrity, to a more dynamic entity that is constantly remodeled to maintain tissue homeostasis. The ECM functions as ligands for cell surface receptors such as integrins, dystroglycans, and toll-like receptors (TLRs) and regulate cellular signaling and immune cell dynamics. The ECM also acts as a sink for growth factors and cytokines, providing critical cues during epithelial morphogenesis. Dysregulation in the organization and deposition of ECMs lead to a plethora of pathophysiological conditions that are exacerbated by aberrant ECM-immune cell interactions. In this review, we focus on the interplay between ECM and immune cells in the context of skin diseases and also discuss state of the art therapies that target the key molecular players involved.

Regulatory cells in the skin: Pathophysiologic role and potential targets for anti-inflammatory therapies

Inflammation is a fundamental defense mechanism to protect the body from danger, which becomes potentially harmful if it turns chronic. Therapeutic strategies aimed at specifically blocking proinflammatory signals, particularly cytokines, such as IL-4, IL-6, IL-13, IL-17A, or TNF-α, have substantially improved our ability to effectively and safely treat chronic inflammatory diseases. Much less effort has been made to better understand the role of potential anti-inflammatory mechanisms. Here we summarize the current understanding of regulatory cell populations in the context of chronic inflammation, namely macrophages, Langerhans cells, myeloid-derived suppressor cells, and regulatory T and B lymphocytes. Emphasis is given to the skin because many different immune-related diseases occur in the skin. Development, phenotype, function, and evidence for their role in animal models of inflammation, as well as in the corresponding human diseases, are described. Finally, the feasibility of using regulatory cells as targets for potentially disease-modifying therapeutic strategies is discussed.

Chemokine Receptors and Exercise to Tackle the Inadequacy of T Cell Homing to the Tumor Site

While cancer immune therapy has revolutionized the treatment of metastatic disease across a wide range of cancer diagnoses, a major limiting factor remains with regard to relying on adequate homing of anti-tumor effector cells to the tumor site both prior to and after therapy. Adoptive cell transfer (ACT) of autologous T cells have improved the outlook of patients with metastatic melanoma. Prior to the approval of checkpoint inhibitors, this strategy was the most promising. However, while response rates of up to 50% have been reported, this strategy is still rather crude. Thus, improvements are needed and within reach. A hallmark of the developing tumor is the evasion of immune destruction. Achieved through the recruitment of immune suppressive cell subsets, upregulation of inhibitory receptors and the development of physical and chemical barriers (such as poor vascularization and hypoxia) leaves the microenvironment a hostile destination for anti-tumor T cells. In this paper, we review the emerging strategies of improving the homing of effector T cells (TILs, CARs, TCR engineered T cells, etc.) through genetic engineering with chemokine receptors matching the chemokines of the tumor microenvironment. While this strategy has proven successful in several preclinical models of cancer and the strategy has moved into the first phase I/II clinical trial in humans, most of these studies show a modest (doubling) increase in tumor infiltration of effector cells, which raises the question of whether road blocks must be tackled for efficient homing. We propose a role for physical exercise in modulating the tumor microenvironment and preparing the platform for infiltration of anti-tumor immune cells. In a time of personalized medicine and genetic engineering, this "old tool" may be a way to augment efficacy and the depth of response to immune therapy.

PD-L1 expression in tumour-infiltrating lymphocytes is a poor prognostic factor for primary acral melanoma patients

AIMS

Programmed cell death protein 1-programmed death-ligand 1 (PD-L1) blockade immunotherapy has shown notable therapeutic benefit in metastatic melanoma, but the clinical relevance of PD-L1 expression remains unclear in melanoma, especially in acral melanoma, which is the most common subtype in Asians. The aim of this study was to evaluate the clinical effect of PD-L1 expression in primary acral melanoma.

METHODS AND RESULTS

We used immunohistochemistry to evaluate PD-L1 expression in tumour cells and tumour-infiltrating lymphocytes (TILs), and analysed its associations with clinicopathological features and survival in 78 primary acral melanoma patients. We found that expression of PD-L1 in tumour cells and TILs occurred exclusively in a tumour-stroma interface pattern, consistent with the predominant pattern of TIL distribution. The presence of peritumoral TILs was also associated with high PD-L1 expression in tumour cells. Furthermore, PD-L1 expression in tumour cells and that in TILs showed a close relationship (Spearman's rho = 0.381, P = 0.001). However, neither PD-L1 expression in tumour cells nor that in TILs was significantly correlated with clinicopathological features. In univariate analysis, cases with PD-L1-positive TILs had significantly poorer survival than those with PD-L1-negative TILs (median disease-specific survival of 40.7 months versus 78.0 months; P = 0.008). In multivariate analysis, PD-L1 expression in TILs was an independent factor for poor prognosis (P = 0.032), whereas PD-L1 expression in tumour cells was not significantly correlated with survival in univariate analysis (P = 0.378) and multivariate analysis (P = 0.354).

CONCLUSION

This is the first study to demonstrate that PD-L1 expression in TILs, but not that in tumour cells, is an independent predictor of poor prognosis in acral melanoma.

Macrophages in skin melanoma-the key element in melanomagenesis

Cutaneous melanoma is an aggressive cancer and its onset and growth are associated, through direct and indirect interactions, with the cancer microenvironment. The microenvironment comprises a dynamic complex of numerous types of cells (due to histogenesis) that constantly interact with each other through multiple cytokines and signaling proteins. Macrophages are one of the most thoroughly studied pleiotropic cells of the immune system. One of their major cytophysiological functions is their involvement in phagocytosis. Previous studies examining the microenvironment of melanomas and tumor-associated macrophages have revealed that they are involved in all stages of melanomagenesis. In the case of cancer initiation, they form an inflammatory microenvironment and then suppress the anticancer activity of the immune system, stimulate angiogenesis, enhance migration and invasion of the cancer cells, and ultimately contribute to the metastatic process. The present review provides a detailed overview on the function of macrophages in the melanoma microenvironment.

Melanoma exosomes promote mixed M1 and M2 macrophage polarization

Macrophages are key participants in melanoma growth and survival. In general, macrophages can be classified as M1 or M2 activation phenotypes. Increasing evidence demonstrates that melanoma exosomes also facilitate tumor survival and metastasis. However, the role of melanoma exosomes in directly influencing macrophage function is poorly understood. Herein, we investigated the hypothesis that natural melanoma exosomes might directly influence macrophage polarization. To explore this hypothesis, ELISA, RT-qPCR, and macrophage functional studies were performed in vitro using an established source of melanoma exosomes (B16-F10). ELISA results for melanoma exosome induction of common M1 and M2 cytokines in RAW 264.7 macrophages, revealed that melanoma exosomes do not polarize macrophages exclusively in the M1 or M2 direction. Melanoma exosomes induced the M1 and M2 representative cytokines TNF-α and IL-10 respectively. Further assessment, using an RT-qPCR array with RAW 264.7 and primary macrophages, confirmed and extended the ELISA findings. Upregulation of markers common to both M1 and M2 polarization phenotypes included CCL22, IL-12B, IL-1β, IL-6, i-NOS, and TNF-α. The M2 cytokine TGF-β was upregulated in primary but not RAW 264.7 macrophages. Pro-tumor functions have been attributed to each of these markers. Macrophage functional assays demonstrated a trend toward increased i-NOS (M1) to arginase (M2) activity. Collectively, the results provide the first evidence that melanoma exosomes can induce a mixed M1 and M2 pro-tumor macrophage activation phenotype.

M1 and M2 macrophages' clinicopathological significance in cutaneous melanoma

Skin malignant melanoma (MM) is an aggressive cancer with an increasing incidence with limited therapies in advanced stages. Tumor-associated macrophages (TAMs) are the major immune constituent of the MM microenvironment and contribute toward its prognosis. TAMs' characterization and localization in human cancer is important to understand cancer progression and to identify molecular personalized therapies. M2 TAMs in stage I-II MMs are associated with worse prognostic parameters. A comprehensive M1-macrophage and M2-macrophage intratumoral localization and quantification in all stages of skin MMs is documented here with its clinical significance. To highlight immune pathways and possible early indicators of MM progression, we evaluated the number of M1 and M2 TAMs and intratumoral distribution in a large series of skin MMs. CD68 double immunostaining with MRP8-14 or inducible nitric oxide synthase (M1 macrophages) and with CD163 or CD204 (M2 macrophages) was performed in 94 stage I-IV skin MMs with a long duration of follow-up. The accumulation and distribution of M1 and M2 TAMs in intratumoral nests, stroma, and at the invasive front was correlated with clinicopathological variables. Since the early stage of MMs, M1 intratumoral macrophages were fewer than the M2 population; their recruitment was rapidly and progressively overwhelmed by an increase in M2 TAMs during MM progression. Independent of their intratumoral distribution, the accumulation of both M1 and M2 TAMs is associated with poor prognostic indicators and patients' survival. M1-recruited macrophages shift to the M2 phenotype early in MM development, possibly induced by high inducible nitric oxide synthase intratumoral increase peculiarly occurring since the initial MM stages. M2-recruited TAMs overwhelm M1 accumulation in all stages of MM progression, thus favoring neoplastic growth and dissemination. Independent of their intratumoral distribution, the prevalent accumulation of M2 TAMs in MM is statistically confirmed to be a poor indicator of patients' outcome and a potential target of immune therapies.

Myeloid-derived suppressor cells are elevated in patients with psoriasis and produce various molecules

Psoriasis is a debilitating chronic inflammatory disease. In addition to the characteristic effects on the skin, chronic inflammation associated with the disease is recognized to contribute to cardiovascular, hepatic and renal comorbidities. Immature myeloid regulatory cells, known as myeloid‑derived suppressor cells (MDSCs), have been demonstrated to accumulate in various diseases and chronic inflammatory states, including inflammatory bowel disease and various types of cancer. The results of the present study, obtained using flow cytometry and cell culture analysis of peripheral blood mononuclear cells from psoriasis and healthy patients, revealed that MDSC levels are significantly increased in the blood of patients with psoriasis compared with healthy controls. Furthermore, these cells are capable of producing various molecules, including matrix metalloproteinase‑9 and‑1, interleukin‑8, growth‑related oncogene, and monocyte chemoattractant protein 1. These molecules may recruit additional immune cells involved in the pathogenesis of the disease, and contribute to the chronic inflammatory state in these patients. Therefore, MDSCs, which have various immune regulatory functions, may contribute to the pathogenesis of psoriasis as a systemic inflammatory disease.

Melanoma exosome induction of endothelial cell GM-CSF in pre-metastatic lymph nodes may result in different M1 and M2 macrophage mediated angiogenic processes

Angiogenesis is a key process in the preparation of lymph nodes for melanoma metastasis. Granulocyte macrophage colony stimulating factor (GM-CSF) induces hypoxia inducible factor 1 alpha (HIF-1α) in M1 or HIF-2α in M2 polarized macrophages. HIF-1α promotes neoangiogenesis while HIF-2α facilitates morphogenic normalization of neovasculature. Melanoma exosomes induce GM-CSF expression by endothelial cells in vitro and HIF-1α expression in pre-metastatic lymph nodes in vivo. This suggest a relationship between melanoma exosome induced endothelial GM-CSF and macrophage mediated angiogenesis in lymph nodes. Theoretically, induction of endothelial cell derived GM-CSF by melanoma exosomes mediates different angiogenic functions in pre-metastatic lymph nodes depending on subcapsular sinus (SCS) macrophage polarity. To explore this hypothesis, experiments utilizing melanoma exosomes in a lymph node model are outlined. Despite their opposing immune functions, indirect melanoma exosome stimulation of M1 or M2 SCS macrophages via endothelial derived GM-CSF in lymph nodes may induce different although complementary pro-tumor angiogenic processes.

Tumor-associated macrophages in skin: How to treat their heterogeneity and plasticity

Immunosuppressive tumor-associated macrophages (TAMs) promote an immunosuppressive environment in the tumor-bearing host, together with regulatory T cells (Tregs). TAMs compose cancer stroma in skin cancers including melanomas and non-melanomas. The majority of tumor-associated macrophages (TAMs) are alternatively activated M2 macrophages that favor tumor development, and they comprise one of the main populations of inflammatory cells in skin cancers. On the other hand, TAMs could be modulated into M1-type macrophages that suppress tumor growth by stimulating and recruiting Th1 and effector cells in the tumor sites. Therefore, TAMs are a target for immunotherapy in various cancers. In this review, we discuss the definition and suppressive mechanisms of TAMs, as well as their biological activities in tumor-bearing hosts to assess potential therapeutic strategies.

Melanoma exosomes enable tumor tolerance in lymph nodes

Melanoma preferentially spreads via lymph nodes. Melanoma exosomes can induce angiogenesis and immune suppression. However, a role for melanoma exosomes in facilitating tumor tolerance in lymph nodes has not been considered. Herein, the hypothesis that melanoma exosome mediated induction of vascular endothelial cell (VEC) derived tumor necrosis factor alpha (TNF-α) results in lymphatic endothelial cell (LEC) mediated tumor tolerance is explored. To support this hypothesis, experiments involving ex vivo lymph node associated VECs, LECs, dendritic cells and T lymphocytes are proposed based upon a previously established fluorescent exosome lymph node trafficking model. The implication of the hypothesis in the context of melanoma exosome mediated induction of tumor tolerance in lymph nodes is then discussed.

A subpopulation that may correspond to granulocytic myeloid-derived suppressor cells reflects the clinical stage and progression of cutaneous melanoma

Seventy-eight melanoma patients and 10 healthy individuals were examined. Follow-up examinations of all melanoma patients were performed regularly every three months. Myeloid-derived suppressor cells (MDSC) were defined as lineage negative (CD3(-), CD19(-), CD56(-)), HLA-DR(-/low), CD11b(+) and CD33(+). Classification of granulocytic (GrMDSC) and monocytic (MoMDSC) subsets was based on the CD15 and CD14 expression, respectively. Unlike the MoMDSC, that were present in 60% of healthy controls and 15% of melanoma patients, the GrMDSC were present in all examined participants, and the melanoma patients were found to have statistically higher frequencies compared with healthy controls. Accordingly, we kept focused on GrMDSC frequencies in relation to the melanoma stages and course of the disease. The GrMDSC values are highest in stage IV melanoma patients, with statistical significance compared with stages IA, IB, IIA and IIB. Patients with progression had statistically higher GrMDSC counts comparing with those with stable disease (P = 0.0079). Patients who had progression-free interval (PFI) < 12 months showed significantly higher GrMDSC values compared with those with PFI > 12 months (P = 0.0333). GrMDSC showed significant negative correlation with PFI intervals (P = 0.0095). The GrMDSC subset was predominant in all our patients. We confirmed that GrMDSC do accumulate early in the peripheral blood of melanoma patients and their frequencies correlate narrowly with the clinical stage and the spread of the disease. The increase in GrMDSC frequencies correlates well with a progressive disease and could be considered a potential predictive biomarker of high-risk melanoma cases that are more likely to have a shorter PFI.

Targeting the tumor microenvironment to enhance antitumor immune responses

The identification of tumor-specific antigens and the immune responses directed against them has instigated the development of therapies to enhance antitumor immune responses. Most of these cancer immunotherapies are administered systemically rather than directly to tumors. Nonetheless, numerous studies have demonstrated that intratumoral therapy is an attractive approach, both for immunization and immunomodulation purposes. Injection, recruitment and/or activation of antigen-presenting cells in the tumor nest have been extensively studied as strategies to cross-prime immune responses. Moreover, delivery of stimulatory cytokines, blockade of inhibitory cytokines and immune checkpoint blockade have been explored to restore immunological fitness at the tumor site. These tumor-targeted therapies have the potential to induce systemic immunity without the toxicity that is often associated with systemic treatments. We review the most promising intratumoral immunotherapies, how these affect systemic antitumor immunity such that disseminated tumor cells are eliminated, and which approaches have been proven successful in animal models and patients.

Restoring immunosurveillance by dendritic cell vaccines and manipulation of the tumor microenvironment

Cancer cells evolve from normal cells throughout life and are usually recognized by our immune system and destroyed, a process called immunosurveillance. Unfortunately, in some instances cancer cells paralyze our immune system, resulting in outgrowth and spreading of the tumor. Understanding the complexity of immunomodulation by tumors is important for the development of therapeutical strategies. Nowadays, various approaches have been developed to enhance anti-tumor immune responses and abrogate the immune dampening effect of the tumor and its surrounding environment, including dendritic cell-based vaccines, therapies to counteract myeloid derived suppressor cell function within the tumor and antagonists of inhibitory signaling pathways to overcome 'immune checkpoints'. The challenge is now to find the right combination of immune based therapies to fully restore immune function and provide a more efficacious and enduring anti-tumor response.

Tumor-educated myeloid cells: impact the micro- and macroenvironment

Immune escape mechanisms of cancers include some of the mechanisms normally used for immune homeostasis, particular those preventing autoimmunity; one of these is the polarisation of myeloid cells. Thereby, tumors, i.e. the cancerous and stromal cells, also condition distant sites like spleen and bone marrow via soluble factors and membrane vesicles such as exosomes in order to create a tumor-educated macroenvironment. Albeit these mechanisms are currently in the focus of (tumor-)immunologic research, the first evidence had been published almost 40 years ago. One of these early reports will be discussed here.

WNT5A induces release of exosomes containing pro-angiogenic and immunosuppressive factors from malignant melanoma cells

Background

Wnt proteins are important for developmental processes and certain diseases. WNT5A is a non-canonical Wnt protein that previously has been shown to play a role in the progression of malignant melanoma. High expression of WNT5A in melanoma tumors correlates to formation of distant metastasis and poor prognosis. This has partly been described by the findings that WNT5A expression in melanoma cell lines increases migration and invasion.

Methods

Malignant melanoma cell lines were treated with rWNT5A or WNT5A siRNA, and mRNA versus protein levels of soluble mediators were measured using RT-PCR, cytokine bead array and ELISA. The induced signaling pathways were analyzed using inhibitors, Rho-GTPase pull down assays and western blot. Ultracentrifugation and electron microscopy was used to analyze microvesicles. Gene expression microarray data obtained from primary malignant melanomas was used to verify our data.

Results

We show that WNT5A signaling induces a Ca²⁺-dependent release of exosomes containing the immunomodulatory and pro-angiogenic proteins IL-6, VEGF and MMP2 in melanoma cells. The process was independent of the transcriptional machinery and depletion of WNT5A reduced the levels of the exosome-derived proteins. The WNT5A induced exosomal secretion was neither affected by Tetanus toxin nor Brefeldin A, but was blocked by the calcium chelator Bapta, inhibited by a dominant negative version of the small Rho-GTPase Cdc42 and was accompanied by cytoskeletal reorganization. Co-cultures of melanoma/endothelial cells showed that depletion of WNT5A in melanoma cells decreased endothelial cell branching, while stimulation of endothelial cells with isolated rWNT5A-induced melanoma exosomes increased endothelial cell branching in vitro. Finally, gene expression data analysis of primary malignant melanomas revealed a correlation between WNT5A expression and the angiogenesis marker ESAM.

Conclusions

These data indicate that WNT5A has a broader function on tumor progression and metastatic spread than previously known; by inducing exosome-release of immunomodulatory and pro-angiogenic factors that enhance the immunosuppressive and angiogenic capacity of the tumors thus rendering them more aggressive and more prone to metastasize.

Immunomics in Skin Cancer - Improvement in Diagnosis, Prognosis and Therapy Monitoring

This review will focus on the elements of the skin’s immune system, immune cells and/or non-immune cells that support immune mechanisms, molecules with immune origin and/or immune functions that are involved in skin carcinogenesis. All these immune elements are compulsory in the development of skin tumors and/or sustainability of the neoplastic process. In this light, recent data gathered in this review will acknowledge all immune elements that contribute to skin tumorigenesis; moreover, they can serve as immune biomarkers. These immune markers can contribute to the diagnostic improvement, prognosis forecast, therapy monitoring, and even personalized therapeutical approach in skin cancer. Immune processes that sustain tumorigenesis in non-melanoma and melanoma skin cancers are described in the framework of recent data.

ESAT-6-gpi DNA vaccine augmented the specific antitumour efficacy induced by the tumour vaccine B16F10-ESAT-6-gpi/IL-21 in a mouse model

In this study, we hypothesized that the mice immunized with the glycosylphosphatidylinositol (GPI) anchored 6-kDa early-secreted antigenic target (ESAT-6) DNA vaccine (ESAT-6-gpi) and the tumour vaccine B16F10-ESAT-6-gpi/IL-21 might significantly enhance immune responses and antimelanoma efficacy. Our experimental results indicated that the anti-ESAT-6 antibody induced by the DNA vaccine ESAT-6-gpi bound ESAT-6 to the surface of tumour vaccine to activate a complement classical pathway and resulted in the B16F10 tumour cell lysis and apoptosis, which served as a potential trigger for breaking melanomatous immune tolerance to elicit an initiation of natural antimelanoma immunity. Our innovative approach of using the DNA vaccine ESAT-6-gpi priming and the tumour vaccine B16F10-ESAT-6-gpi/IL-21 boosting induced strong antimelanoma immunity that inhibited melanomatous growth. These findings highlighted the DNA vaccine ESAT-6-gpi as an immune enhancer to augment the immune efficacy of the tumour vaccine B16F10-ESAT -6-gpi/IL-21 against melanoma in a mouse model.

Newer developments in the immunotherapy of malignant melanoma

Individuals with malignant melanoma present a variety of immune abnormalities including but not limited to cellular immune dysfunction, antigen presentation deficits, and cytokine production defects. Therefore, enhancing the immune system potential represents an appealing avenue for melanoma therapy. The authors review the immune therapies currently in clinical use as well as the most promising immunotherapy candidates. Ipilimumab, a monoclonal antibody against the CTLA-4, was approved for the therapy of advanced melanoma in 2011. In addition, sizeable anti-melanoma activity has recently been shown with the use of other agents including anti-PD-1/anti-PD-1 ligand antibodies. Consequently, these experimental immunotherapy agents may soon become important items in the anti-melanoma armamentarium.

Melanoma-derived conditioned media efficiently induce the differentiation of monocytes to macrophages that display a highly invasive gene signature

The presence of tumor-associated macrophages (TAMs) in melanomas is correlated with a poor clinical prognosis. However, there is limited information on the characteristics and biological activities of human TAMs in melanomas. In this study, we developed an in vitro method to differentiate human monocytes to macrophages using modified melanoma-conditioned medium (MCM). We demonstrate that factors from MCM-induced macrophages (MCMI-Mφ) express both M1-Mφ and M2-Mφ markers and inhibit melanoma-specific T-cell proliferation. Furthermore, microarray analyses reveal that the majority of genes up-regulated in MCMI-Mφ are associated with tumor invasion. The most strikingly up-regulated genes are CCL2 and MMP-9. Consistent with this, blockade of both CCL-2 and MMPs diminish MCMI-Mφ-induced melanoma invasion. Finally, we demonstrated that both MCMI-Mφ and in vivo TAMs express the pro-invasive, melanoma-associated gene, glycoprotein non-metastatic melanoma protein B. Our study provides a framework for understanding the mechanisms of cross-talk between TAMs and melanoma cells within the tumor microenvironment.

The immune system--a hidden treasure for biomarker discovery in cutaneous melanoma

This chapter describes how skin immune system (SIS) is specifically involved in the development of cutaneous melanoma. Local immune surveillance is presented as a complex process that comprises markers to be monitored in disease's evolution and in therapy. The ranking of tissue or soluble immune markers in a future panel of diagnostic/prognostic panel are evaluated. Taking into account the difficulties of cutaneous melanoma patients' management, this chapter shows the immune surveillance at the skin level, the conditions that favor the tumor escape from the immunological arm, the immune pattern of skin melanoma with diagnostic/prognostic relevance, the circulatory immune markers, and, last but not least, how immune markers are used in immune-therapy monitoring. The chapter cannot be exhaustive but will give the reader a glimpse of the complex immune network that lies within tumor escape and where to search for immune-therapeutical targets in skin melanoma.

Immunotherapy for metastatic melanoma

Melanoma has traditionally been considered an immunogenic tumor. A number of approaches have been studied for enhancement of antitumor immunity. The first cytokine approved for the treatment of metastatic melanoma, interleukin-2, has resulted in prolonged responses in a small subset of patients, providing hope that immunotherapy might be useful for this disease. Ipilimumab, a monoclonal antibody to CTLA-4, was recently approved and a number of other promising investigational approaches are currently being pursued. This manuscript discusses more recent advances in the treatment of melanoma employing a variety of immune-enhancing approaches.

Ultraviolet radiation and the slug transcription factor induce proinflammatory and immunomodulatory mediator expression in melanocytes

Despite extensive investigation, the precise contribution of the ultraviolet radiation (UVR) component of sunlight to melanoma etiology remains unclear. UVR induces keratinocytes to secrete proinflammatory and immunomodulatory mediators that promote inflammation and skin tumor development; expression of the slug transcription factor in keratinocytes is required for maximal production of these mediators. In the present studies we examined the possibility that UVR-exposed melanocytes also produce proinflammatory mediators and that Slug is important in this process. Microarray studies revealed that both UVR exposure and Slug overexpression altered transcription of a variety of proinflammatory mediators by normal human melanocytes; some of these mediators are also known to stimulate melanocyte growth and migration. There was little overlap in the spectra of cytokines produced by the two stimuli. However IL-20 was similarly induced by both stimuli and the NFκB pathway appeared to be important in both circumstances. Further exploration of UVR-induced and Slug-dependent pathways of cytokine induction in melanocytes may reveal novel targets for melanoma therapy.

Dissection of stromal and cancer cell-derived signals in melanoma xenografts before and after treatment with DMXAA

Background:

The non-malignant cells of the tumour stroma have a critical role in tumour biology. Studies dissecting the interplay between cancer cells and stromal cells are required to further our understanding of tumour progression and methods of intervention. For proof-of-principle of a multi-modal approach to dissect the differential effects of treatment on cancer cells and stromal cells, we analysed the effects of the stromal-targeting agent 5,6-dimethylxanthenone-4-acetic acid on melanoma xenografts.

Methods:

Flow cytometry and multi-colour immunofluorescence staining was used to analyse leukocyte numbers in xenografts. Murine-specific and human-specific multiplex cytokine panels were used to quantitate cytokines produced by stromal and melanoma cells, respectively. Human and mouse Affymetrix microarrays were used to separately identify melanoma cell-specific and stromal cell-specific gene expression.

Results:

5,6-Dimethylxanthenone-4-acetic acid activated pro-inflammatory signalling pathways and cytokine expression from both stromal and cancer cells, leading to neutrophil accumulation and haemorrhagic necrosis and a delay in tumour re-growth of 26 days in A375 melanoma xenografts.

Conclusion:

5,6-Dimethylxanthenone-4-acetic acid and related analogues may potentially have utility in the treatment of melanoma. The experimental platform used allowed distinction between cancer cells and stromal cells and can be applied to investigate other tumour models and anti-cancer agents.

Dendritic cell-based vaccine in advanced melanoma: update of clinical outcome

Dendritic cells (DCs) are unique specialized antigen-presenting cells capable of priming naive T cells and inducing antigen-specific cytotoxic T lymphocytes. This study presents an update of clinical results from a DC-based phase I-II clinical vaccine trial in stage IV melanoma. From 2003 to 2010, 27 patients with metastatic melanoma were treated with mature DCs pulsed with autologous tumor lysate and keyhole limpet hemocyanin and with subcutaneous low-dose interleukin-2. Delayed-type hypersensitivity (DTH) tests for in-vivo immunomonitoring were performed at baseline and every four vaccinations thereafter. Two complete, two mixed and six partial responses, and five stable diseases were observed (overall response, 37.0%; clinical benefit, 55.5%). All 15 responders showed DTH positivity. A median overall survival of 22.9 months [95% confidence interval (CI): 13.4-61.3] for DTH-positive patients (19) and 4.8 months (95% CI: 3.9-11.9) for DTH-negative patients (8; log rank=7.26; P=0.007) was observed. The overall median overall survival was 16 months (95% CI: 9-33). Our results would seem to highlight a relationship between positive-DTH test and an improved survival.

PD-1 expression on Melan-A-reactive T cells increases during progression to metastatic disease

Programmed death 1 (PD-1) is known as an important factor for the development of tolerogenicity. This has been proven in chronic viral infections and different tumor models. To address the role of PD-1 and its ligand programmed death ligand 1 (PD-L1) in different stages of malignant melanoma, we investigated peripheral blood and tumor tissues in regard to overall survival (OS) and prognostic relevance. One hundred samples of peripheral blood mononuclear cells from HLA-A2(+) patients with malignant melanoma (Stages I-IV) were analyzed in seven color FACS combined with multimer analyses for the immunodominant epitope of Melan-A (peptide A2/Melan-A(p26-35mod) ). Corresponding formalin-fixed paraffin-embedded tissues of primary tumor and distant organ metastases from 37 cases were analyzed by immunohistochemistry for Melan-A, PD-L1 and PD-1 expression. Compared to the total CD8(+) T cell population, PD-1 expression by A2/Melan-A(+) CD8(+) T cells was over-represented in melanoma stages III and IV (p < 0.001). Although elevation of PD-1(+) Melan-A(+) CD8(+) T cells had no significant influence on OS, a positive correlation was observed between PD-L1 expression on melanoma cells and OS (p = 0.05). Correlation of advanced tumor stage with increased A2/Melan-A-multimer(+) PD-1(+) T cells in the peripheral blood suggest that blocking of PD-1 could have therapeutic potential in advanced stage melanoma.

Tolerance-inducing strategies in islet transplantation

Allogeneic islet transplantation is a promising approach for restoring normoglycemia in type 1 diabetic patients. Current use of immunosuppressive therapies for management of islet transplant recipients can be counterintuitive to islet function and can lead to complications in the long term. The induction of donor-specific tolerance eliminates the dependency on immunosuppression and allows recipients to retain responses to foreign antigens. The mechanisms by which tolerance is achieved involve the deletion of donor-reactive T cells, induction of T-cell anergy, immune deviation, and generation of regulatory T cells. This review will outline the various methods used for inducing donor-specific tolerance in islet transplantation and will highlight the previously unforeseen potential of tissue stromal cells in promoting islet engraftment.

Ex vivo enrichment of circulating anti-tumor T cells from both cutaneous and ocular melanoma patients: clinical implications for adoptive cell transfer therapy

Tumor-infiltrating lymphocytes (TILs) have been successfully used for adoptive cell transfer (ACT) immunotherapy; however, due to their scarce availability, this therapy is possible for a limited fraction of cutaneous melanoma patients. We assessed whether an effective protocol for ex vivo T-cell expansion from peripheral blood mononuclear cells (PBMCs), suitable for ACT of both cutaneous and ocular melanoma patients, could be identified. PBMCs from both cutaneous and ocular melanoma patients were stimulated in vitro with autologous, irradiated melanoma cells (mixed lymphocyte tumor cell culture; MLTCs) in the presence of IL-2 and IL-15 followed by the rapid expansion protocol (REP). The functional activity of these T lymphocytes was characterized and compared with that of TILs. In addition, the immune infiltration in vivo of ocular melanoma lesions was analyzed. An efficient in vitro MLTC expansion of melanoma reactive T cells was achieved from all PBMC’s samples obtained in 7 cutaneous and ocular metastatic melanoma patients. Large numbers of melanoma-specific T cells could be obtained when the REP protocol was applied to these MLTCs. Most MLTCs were enriched in non-terminally differentiated T_EM cells homogeneously expressing co-stimulatory molecules (e.g., NKG2D, CD28, CD134, CD137). A similar pattern of anti-tumor activity, in association with a more variable expression of co-stimulatory molecules, was detected on short-term in vitro cultured TILs isolated from the same patients. In these ocular melanoma patients, we observed an immune infiltrate with suppressive characteristics and a low rate of ex vivo growing TILs (28.5% of our cases). Our MLTC protocol overcomes this limitation, allowing the isolation of T lymphocytes with effector functions even in these patients. Thus, anti-tumor circulating PBMC-derived T cells could be efficiently isolated from melanoma patients by our novel ex vivo enrichment protocol. This protocol appears suitable for ACT studies of cutaneous and ocular melanoma patients.

IL-10 expression by primary tumor cells correlates with melanoma progression from radial to vertical growth phase and development of metastatic competence

Downregulation of the immune system facilitates tumor progression at different stages of cutaneous melanoma. Sentinel nodes, the first lymph nodes on lymphatics draining directly from a primary melanoma, are immune downregulated by tumor-generated immunosuppressive cytokines, including interleukin-10 (IL-10). To better understand the kinetics of sentinel node suppression, we investigated IL-10 expression by melanoma cells and tumor-associated macrophages and lymphocytes at different stages of primary melanoma evolution. We used reverse-transcriptase in situ PCR to identify the cellular sources of IL-10 mRNA in 39 melanomas. IL-10 mRNA was identified in tumor cells of 2 of 6 melanomas in situ (33%), of 17 of 21 invasive melanomas (81%) and of 11 of 12 metastatic melanomas (92%). Higher IL-10 expression correlates with tumor progression, with differences between melanoma in situ, invasive melanoma and metastatic melanoma. In primary melanomas, the IL-10 mRNA content of tumor cells correlates with Clark's level. There was significantly more IL-10 mRNA in vertical growth-phase melanoma cells than in radial growth-phase cells. In a logistic regression model, moderate-to-high IL-10 mRNA expression by tumor cells was significantly associated with vertical growth-phase melanoma. IL-10 mRNA was detected in melanoma-associated macrophages and lymphocytes. In invasive melanomas, IL-10 mRNA reactivity of macrophages decreased as Clark's level increased. Alterations of immunity by IL-10 derived from melanoma cells and melanoma-associated macrophages and lymphocytes potentially facilitate evolution of the primary melanoma and render regional lymph nodes susceptible to metastases.

Immunomodulatory cytokines as therapeutic agents for melanoma

Melanoma is the most aggressive form of skin cancer whose worldwide incidence is rising faster than any other cancer. Few treatment options are available to patients with metastatic disease, and standard chemotherapeutic agents are generally ineffective. Cytokines such as IFN-α or IL-2 can promote immune recognition of melanoma, occasionally inducing dramatic and durable clinical responses. Here, we discuss several immunomodulatory agents, the safety of which are being evaluated in clinical trials. Challenges include an incomplete understanding of signaling pathways, appropriate clinical dose and route, and systemic immunosuppression in advanced melanoma patients. We consider how targeted cytokine therapy will integrate into the clinical arena, as well as the low likelihood of success of single cytokine therapies. Evidence supports a synergy between cytokine immunotherapy and other therapeutic approaches in melanoma, and strengthening this area of research will improve our understanding of how to use cytokine therapy better.

Intertissue flow of glutathione (GSH) as a tumor growth-promoting mechanism: interleukin 6 induces GSH release from hepatocytes in metastatic B16 melanoma-bearing mice

B16 melanoma F10 (B16-F10) cells with high glutathione (GSH) content show high metastatic activity in vivo. An intertissue flow of GSH, where the liver is the main reservoir, can increase GSH content in metastatic cells and promote their growth. We have studied here possible tumor-derived molecular signals that could activate GSH release from hepatocytes. GSH efflux increases in hepatocytes isolated from mice bearing liver or lung metastases, thus suggesting a systemic mechanism. Fractionation of serum-free conditioned medium from cultured B16-F10 cells and monoclonal antibody-induced neutralization techniques facilitated identification of interleukin (IL)-6 as a tumor-derived molecule promoting GSH efflux in hepatocytes. IL-6 activates GSH release through a methionine-sensitive/organic anion transporter polypeptide 1- and multidrug resistance protein 1-independent channel located on the sinusoidal site of hepatocytes. Specific siRNAs were used to knock down key factors in the main signaling pathways activated by IL-6, which revealed a STAT3-dependent mechanism. Our results show that IL-6 (mainly of tumor origin in B16-F10-bearing mice) may facilitate GSH release from hepatocytes and its interorgan transport to metastatic growing foci.

Immune-related biomarkers for diagnosis/prognosis and therapy monitoring of cutaneous melanoma

Skin melanoma, a life-threatening disease, has a recently reported worldwide increase in incidence, despite primary prevention. Skin melanoma statistics emphasize the need for finding markers related to the immune response of the host. The mechanisms that are able to over-power the local immune surveillance comprise molecules that can be valuable markers for diagnosis and prognosis. This article summarizes the immune markers that can monitor the disease stage and evaluate the efficacy of therapeutic interventions. Recent data regarding immunotherapy are presented in the context of tumor escape from immune surveillance and the immune molecules that are both targets and a means of monitoring. Perspectives for developing immune interventions for skin melanoma management and the position of tissue or soluble immune markers as a diagnostic/prognostic panel are evaluated. State-of-the-art technology is emphasized for developing immune molecular signatures for a complex characterization of the patient's immunological status.

Induction of monocyte chemoattractant protein-1 and interleukin-10 by TGFbeta1 in melanoma enhances tumor infiltration and immunosuppression

Melanoma progression is associated with the expression of different growth factors, cytokines, and chemokines. Because TGFβ1 is a pleiotropic cytokine involved not only in physiologic processes but also in cancer development, we analyzed in A375 human melanoma cells, the effect of TGFβ1 on monocyte chemoattractant protein-1 (MCP-1) and interleukin-10 (IL-10) expression, two known factors responsible for melanoma progression. TGFβ1 increased the expression of MCP-1 and IL-10 in A375 cells, an effect mediated by the cross-talk between Smad, PI3K (phosphoinositide 3-kinase)/AKT, and BRAF-MAPK (mitogen activated protein kinase) signaling pathways. Supernatants from TGFβ1-treated A375 cells enhanced MCP-1-dependent migration of monocytes, which, in turn, expressed high levels of TGF,β1, bFGF, and VEGF mRNA. Moreover, these supernatants also inhibited functional properties of dendritic cells through IL-10-dependent mechanisms. When using in vitro, the TGFβ1-blocking peptide P144, TGFβ1-dependent Smad3 phosphorylation, and expression of MCP-1 and IL-10 were inhibited. In vivo, treatment of A375 tumor-bearing athymic mice with P144 significantly reduced tumor growth, associated with a lower macrophage infiltrate and decreased intratumor MCP-1 and VEGF levels, as well as angiogenesis. Finally, in C57BL/6 mice with B16-OVA melanoma tumors, when administered with immunotherapy, P144 decreased tumor growth and intratumor IL-10 levels, linked to enhanced activation of dendritic cells and natural killer cells, as well as anti-OVA T-cell responses. These results show new effects of TGFβ1 on melanoma cells, which promote tumor progression and immunosuppression, strongly reinforcing the relevance of this cytokine as a molecular target in melanoma.

Diagnostic value and prognostic significance of plasmatic proteasome level in patients with melanoma

Plasmatic proteasome (p-proteasome) also called circulating proteasome has recently been described as a tumor marker. We investigated the diagnostic and prognostic accuracies of p-proteasome levels in a melanoma population classified according to the American Joint Committee on Cancer staging system. Using an ELISA test, we measured p-proteasome levels in 90 patients and 40 controls between March 2003 and March 2008. The subunit composition of p-proteasomes was determined in metastatic melanoma by proteomic analysis. The mean p-proteasome levels were correlated with stages (P < 0.0001; r(S) = 0.664). They were significantly higher in patients with stage IV and stage III with lymph node metastasis (9187 ± 1294 and 5091 ± 454 ng/ml, respectively) compared to controls (2535 ± 187 ng/ml; P < 0.001), to stage I/II (2864 ± 166 ng/ml; P < 0.001) and to stage III after curative lymphadenectomy (2859 ± 271 ng/ml; P < 0.001). The diagnostic accuracy of p-proteasome was evaluated by receiver operating characteristic analysis. With a cut-off of 4300 ng/ml, diagnostic specificity and sensitivity of p-proteasome for regional or visceral metastases were respectively 96.3% and 72.2%. In univariate analysis, high p-proteasome levels (>4300 ng/ml) were significantly correlated with an increased risk of progression [hazard ratio (HR) = 7.34; 95% CI 3.54-15.21, P < 0.0001] and a risk of death (HR = 5.92; 95% CI 2.84-12.33, P < 0.0001). In multivariate analysis, high p-proteasome levels were correlated with a poorer clinical outcome in the subgroup analysis limited to patients with disease stages I, II and III. Proteomic analysis confirmed the presence of all proteasome and immunoproteasome subunits. Taken together, these results indicate that p-proteasomes are a new marker for metastatic dissemination in patients with melanoma.

Role of immune-regulatory cells in skin pathology

The skin harbors a complex and unique immune system that protects against various pathologies, such as infection and cancer. Although many of the mechanisms of immune activation in the skin have been investigated, it is likewise important to uncover the immune-regulatory components that limit effective immunity or prevent autoimmunity. Several cell populations are involved in this immune-regulatory function, including CD4+ T cells that coexpress the transcription factor Foxp3, known as Tregs, and cells with immune-regulatory function known as myeloid-derived suppressor cells (MDSCs). This review focuses on the role that immune-regulatory cells, such as MDSCs and Tregs, play in cutaneous pathology, such as malignancy, psoriasis, dermatitis, burn wounds, and transplantation. Although their depletion may serve to augment immunity, expansion of these cells may be used to suppress excessive immune reactions. These cells are attractive, therapeutic targets for various conditions and thus, deserve further exploration.