Melanoma and innate immunity--aActive inflammation or just erroneous attraction? Melanoma as the source of leukocyte-attracting chemokines

The neutrophil-to-lymphocyte ratio and the prevalence of cutaneous melanoma: a retrospective observational study of NHANES statistics spanning 1999 to 2018

This study aimed to investigated the association between the ratio of neutrophils to lymphocytes (NLR) and cutaneous melanoma (CM) and to determine the association between the NLR and the prevalence of CM. A retrospective observational study involving 62,102 individuals over the age of 18, drawn from the National Health and Nutrition Examination Survey (NHANES), which was carried out over the period from 1999 to 2018. NLR derived from laboratory data, while CM diagnosis was based on participants' self-reports. The relationship between the NLR and CM was assessed using weighted logistic regression analyses, complemented by restricted cubic spline analyses. The study encompassed a total of 336 adults afflicted with CM and 49,621 adults free from CM. The findings exposed a correlation between the NLR and the occurrence of CM, having an odds ratio (OR) of 1.63 (95% confidence interval [CI]: 1.07 to 2.48; p = 0.022). Moreover, the restricted cubic spline model showed a non-linear pattern between the NLR and CM. Overall, we found that the NLR was positively associated with the prevalence of CM. Our findings highlight that NLR may be a systemic inflammation waring marker for CM in US individuals.

Inflammasome activation in melanoma progression: the latest update concerning pathological role and therapeutic value

The progression of melanoma is a complex process influenced by both internal and external cues which encourage the transition of tumour cells, uncontrolled growth, migration, and metastasis. Additionally, inflammation allows tumours to evade the immune system, contributing to cancer development. The inflammasome, a complex of many proteins, is crucial in enhancing immune responses to external and internal triggers. As a critical inflammatory mechanism, it contributes to the development of melanoma. These mechanisms may be triggered via various internal and external stimuli, causing the induction of specific enzymes such as caspase-1, caspase-11, or caspase-8. This, in turn, leads to the release of interleukin (IL)-1β and IL-18 and cell death by apoptosis and pyroptosis. Proper inflammasome stimulation is crucial for the host to deal with invading pathogens or tissue injury. However, inappropriate inflammasome stimulation can result in unregulated tissue reactions, thus easing many diseases, including melanoma. Hence, keeping a delicate equilibrium between the stimulation and prohibition of inflammasomes is crucial, necessitating meticulous control of the assembly and functional aspects of inflammasomes. This review examines the latest advancements in inflammasome studies, specifically focusing on the molecular processes that control inflammasome formation, signalling, and modulation in melanoma.

Myeloid-derived suppressor cells in cancer: Current knowledge and future perspectives

MDSCs (myeloid-derived suppressor cells) are crucial for immune system evasion in cancer. They accumulate in peripheral blood and tumor microenvironment, suppressing immune cells like T-cells, natural killer cells and dendritic cells. They promote tumor angiogenesis and metastasis by secreting cytokines and growth factors and contribute to a tumor-promoting environment. The accumulation of MDSCs in cancer patients has been linked to poor prognosis and resistance to various cancer therapies. Targeting MDSCs and their immunosuppressive mechanisms may improve treatment outcomes and enhance immune surveillance by developing drugs that inhibit MDSC function, by preventing their accumulation and by disrupting the tumor-promoting environment. This review presents a detailed overview of the MDSC research in cancer with regulation of their development and function. The relevance of MDSC as a prognostic and predictive biomarker in different types of cancers, along with recent advancements on the therapeutic approaches to target MDSCs are discussed in detail.

Melanoma-derived soluble mediators modulate neutrophil biological properties and the release of neutrophil extracellular traps

Polymorphonuclear neutrophils (PMNs) are the main effector cells in the inflammatory response. The significance of PMN infiltration in the tumor microenvironment remains unclear. Metastatic melanoma is the most lethal skin cancer with an increasing incidence over the last few decades. This study aimed to investigate the role of PMNs and their related mediators in human melanoma. Highly purified human PMNs from healthy donors were stimulated in vitro with conditioned media (CM) derived from the melanoma cell lines SKMEL28 and A375 (melanoma CM), and primary melanocytes as controls. PMN biological properties (chemotaxis, survival, activation, cell tracking, morphology and NET release) were evaluated. We found that the A375 cell line produced soluble factors that promoted PMN chemotaxis, survival, activation and modification of morphological changes and kinetic properties. Furthermore, in both melanoma cell lines CM induced chemotaxis, activation and release of neutrophil extracellular traps (NETs) from PMNs. In contrast, the primary melanocyte CM did not modify the biological behavior of PMNs. In addition, serum levels of myeloperoxidase, matrix metalloprotease-9, CXCL8/IL-8, granulocyte and monocyte colony-stimulating factor and NETs were significantly increased in patients with advanced melanoma compared to healthy controls. Melanoma cell lines produce soluble factors able to "educate" PMNs toward an activated functional state. Patients with metastatic melanoma display increased circulating levels of neutrophil-related mediators and NETs. Further investigations are needed to better understand the role of these "tumor-educated neutrophils" in modifying melanoma cell behavior.

Enhancing immunotherapy response in melanoma: myeloid-derived suppressor cells as a therapeutic target

Despite the remarkable success of immune checkpoint inhibitors (ICIs) in melanoma treatment, resistance to them remains a substantial clinical challenge. Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of myeloid cells that can suppress antitumor immune responses mediated by T and natural killer cells and promote tumor growth. They are major contributors to ICI resistance and play a crucial role in creating an immunosuppressive tumor microenvironment. Therefore, targeting MDSCs is considered a promising strategy to improve the therapeutic efficacy of ICIs. This Review describes the mechanism of MDSC-mediated immune suppression, preclinical and clinical studies on MDSC targeting, and potential strategies for inhibiting MDSC functions to improve melanoma immunotherapy.

Comprehensive Gene Expression Analysis to Identify Differences and Similarities between Sex- and Stage-Stratified Melanoma Samples

Overall lower incidence and better prognosis are observed in female melanoma patients compared to males. As sex and stage differences in the context of melanoma gene expression are understudied, we aim to highlight them through statistical analysis of melanoma gene expression datasets. Data from seven online datasets, including normal skin, commonly acquired nevi, and melanomas, were collected and analyzed. Sex/stage-related differences were assessed using statistical analyses on survival, gene expression, and its variability. Significantly better overall survival in females was observed in stage I, II but not in stage III. Gene expression variability was significantly different between stages and sexes. Specifically, we observed a significantly lower variability in genes expressed in normal skin and nevi in females compared to males, as well as in female stage I, II melanomas. However, in stage III, variability was lower in males. Similarly, class comparison showed that the gene expression differences between sexes are most notable in non-melanoma followed by early-stage-melanoma samples. Sexual dimorphism is an important aspect to consider for a holistic understanding of early-stage melanomas, not only from the tumor characteristics but also from the gene expression points of view.

The Role of the Vitamin D Receptor in the Pathogenesis, Prognosis, and Treatment of Cutaneous Melanoma

Melanoma is the malignant transformation of melanocytes and represents the most lethal form of skin cancer. While early-stage melanoma localized to the skin can be cured with surgical excision, metastatic melanoma often requires a multi-pronged approach and even then can exhibit treatment resistance. Understanding the molecular mechanisms involved in the pathogenesis of melanoma could lead to novel diagnostic, prognostic, and therapeutic strategies to ultimately decrease morbidity and mortality. One emerging candidate that may have value as both a prognostic marker and in a therapeutic context is the vitamin D receptor (VDR). VDR is a nuclear steroid hormone receptor activated by 1,25 dihydroxy-vitamin D3 [calcitriol, 1,25(OH)2D3]. While 1,25 dihydroxy-vitamin D3 is typically thought of in relation to calcium metabolism, it also plays an important role in cell proliferation, differentiation, programmed-cell death as well as photoprotection. This review discusses the role of VDR in the crosstalk between keratinocytes and melanocytes during melanomagenesis and summarizes the clinical data regarding VDR polymorphisms, VDR as a prognostic marker, and potential uses of vitamin D and its analogs as an adjuvant treatment for melanoma.

Unraveling the crosstalk between melanoma and immune cells in the tumor microenvironment

Cutaneous melanoma is the most common skin cancer with an incidence that has been rapidly increasing in the past decades. Melanomas are among the most immunogenic tumors and, as such, have the greatest potential to respond favorably to immunotherapy. However, like many cancers, melanomas acquire various suppressive mechanisms, which generally act in concert, to escape innate and adaptive immune detection and destruction. Intense research into the cellular and molecular events associated with melanomagenesis, which ultimately lead to immune suppression, has resulted in the discovery of new therapeutic targets and synergistic combinations of immunotherapy, targeted therapy and chemotherapy. Tremendous effort to determine efficacy of single and combination therapies in pre-clinical and clinical phase I-III trials has led to FDA-approval of several immunotherapeutic agents that could potentially be beneficial for aggressive, highly refractory, advanced and metastatic melanomas. The increasing availability of approved combination therapies for melanoma and more rapid assessment of patient tumors has increased the feasibility of personalized treatment to overcome patient and tumor heterogeneity and to achieve greater clinical benefit. Here, we review the evolution of the immune system during melanomagenesis, mechanisms exploited by melanoma to suppress anti-tumor immunity and methods that have been developed to restore immunity. We emphasize that an effective therapeutic strategy will require coordinate activation of tumor-specific immunity as well as increased recognition and accessibility of melanoma cells in primary tumors and distal metastases. This review integrates available knowledge on melanoma-specific immunity, molecular signaling pathways and molecular targeting strategies that could be utilized to envision therapeutics with broader application and greater efficacy for early stage and advanced metastatic melanoma.

PDGFR-alpha inhibits melanoma growth via CXCL10/IP-10: a multi-omics approach

Melanoma is the most aggressive skin-cancer, showing high mortality at advanced stages. Platelet Derived Growth Factor Receptor-alpha (PDGFR-alpha) potently inhibits melanoma- and endothelium-proliferation and its expression is significantly reduced in melanoma-biopsies, suggesting that melanoma progression eliminates cells expressing PDGFR-alpha. In the present study transient overexpression of PDGFR-alpha in endothelial (HUVEC) and melanoma (SKMel-28, A375, Preyer) human-cells shows strong anti-proliferative effects, with profound transcriptome and miRNome deregulation. PDGFR-alpha overexpression strongly affects expression of 82 genes in HUVEC (41 up-, 41 down-regulated), and 52 genes in SKMel-28 (43 up-, 9 down-regulated). CXCL10/IP-10 transcript showed up to 20 fold-increase, with similar changes detectable at the protein level. miRNA expression profiling in cells overexpressing PDGFR-alpha identified 14 miRNAs up- and 40 down-regulated, with miR-503 being the most down-regulated (6.4 fold-reduction). miR-503, miR-630 and miR-424 deregulation was confirmed by qRT-PCR. Interestingly, the most upregulated transcript (i.e., CXCL10/IP-10) was a validated miR-503 target and CXCL10/IP-10 neutralization significantly reverted the anti-proliferative action of PDGFR-alpha, and PDGFR-alpha inhibition by Dasatinb totally reverted the CXCL10/IP10 induction, further supporting a functional interplay of these factors. Finally, integration of transcriptomics and miRNomics data highlighted several pathways affected by PDGFR-alpha.

This study demonstrates for the first time that PDGFR-alpha strongly inhibits endothelial and melanoma cells proliferation in a CXCL10/IP-10 dependent way, via miR-503 down-regulation.

The Role of Myeloid-Derived Suppressor Cells (MDSC) in Cancer Progression

The immunosuppressive tumor microenvironment represents not only one of the key factors stimulating tumor progression but also a strong obstacle for efficient tumor immunotherapy. Immunosuppression was found to be associated with chronic inflammatory mediators including cytokines, chemokines and growth factors produced by cancer and stroma cells. Long-term intensive production of these factors induces the formation of myeloid-derived suppressor cells (MDSCs) representing one of the most important players mediating immunosuppression. Moreover, MDSCs could not only inhibit anti-tumor immune reactions but also directly stimulate tumor growth and metastasis. Therefore, understanding the mechanisms of their generation, expansion, recruitment and activation is required for the development of novel strategies for tumor immunotherapy.

Phytomedicine-Modulating oxidative stress and the tumor microenvironment for cancer therapy

In spite of the current advances and achievements in systems biology and translational medicinal research, the current strategies for cancer therapy, such as radiotherapy, targeted therapy, immunotherapy and chemotherapy remain palliative or unsatisfactory due to tumor metastasis or recurrence after surgery/therapy, drug resistance, adverse side effects, and so on. Oxidative stress (OS) plays a critical role in chronic/acute inflammation, carcinogenesis, tumor progression, and tumor invasion/metastasis which is also attributed to the dynamic and complex properties and activities in the tumor microenvironment (TME). Re-educating or reprogramming tumor-associated stromal or immune cells in the TME provides an approach for restoring immune surveillance impaired by disease in cancer patients to increase overall survival and reduce drug resistance. Herbal medicines or plant-derived natural products have historically been a major source of anti-cancer drugs. Delving into the lore of herbal medicine may uncover new leads for anti-cancer drugs. Phytomedicines have been widely documented to directly or indirectly target multiple signaling pathways and networks in cancer cells. A combination of anti-cancer drugs and polypharmacological plant-derived extracts or compounds may offer a significant advantage in sensitizing the efficacy of monotherapy and overcoming drug-induced resistance in cancer patients. This review introduces several phytochemicals and phytoextracts derived from medicinal plants or dietary vegetables that have been studied for their efficacy in preclinical cancer models. We address the underlying modes of action of induction of OS and deregulation of TME-associated stromal cells, mediators and signaling pathways, and reference the related clinical investigations that look at the single or combination use of phytochemicals and phytoextracts to sensitize anti-cancer drug effects and/or overcome drug resistance.

TLR7 Gln11Leu single nucleotide polymorphism and susceptibility to cutaneous melanoma

Cutaneous melanoma is a life-threatening skin cancer. Its incidence is rapidly increasing, and early diagnosis is the main factor able to improve its poor prognosis. Toll-like receptors (TLRs) are transmembrane glycoproteins that recognize pathogen- and damage-associated molecular patterns, against which TLRs activate the innate immune response and initiate the adaptive immune response. Genetic variations of these receptors may alter the immune system, and are involved in evolution and susceptibility to various diseases, including cancer. The aim of the present study was to evaluate whether the presence of TLR7 glutamine (Gln) 11 leucine (Leu) polymorphism confers an increased susceptibility to cutaneous melanoma. For that purpose, a case-control study was performed with 182 melanoma cases and 89 controls. To highlight the possible association between the aforementioned polymorphism and the susceptibility to melanoma, 93 cases of single melanoma and 89 cases of multiple primary melanoma (MPM) were compared in the present study. Since the TLR7 gene is localized on the chromosome X, the allelic frequency of the Gln11Leu polymorphism was analyzed separately in males and females. The distribution of allele frequencies between melanoma cases and controls (P=0.245) and between single melanoma and MPM cases (P=0.482) was not significant. Therefore, the present results do not suggest an association between TLR7 Gln11Leu polymorphism and susceptibility to cutaneous melanoma. Further studies are required to analyze the influence of other TLR polymorphisms on the susceptibility to malignant melanoma and the involvement of innate immunity in this malignancy.

Modulation of Acid Sphingomyelinase in Melanoma Reprogrammes the Tumour Immune Microenvironment

The inflammatory microenvironment induces tumours to acquire an aggressive and immunosuppressive behaviour. Since acid sphingomyelinase (A-SMase) downregulation in melanoma was shown to determine a malignant phenotype, we aimed here to elucidate the role of A-SMase in the regulation of tumour immunogenic microenvironment using in vivo melanoma models in which A-SMase was either downregulated or maintained at constitutively high levels. We found high levels of inflammatory factors in low A-SMase expressing tumours, which also displayed an immunosuppressive/protumoural microenvironment: high levels of myeloid-derived suppressor cells (MDSCs) and regulatory T lymphocytes (Tregs), as well as low levels of dendritic cells (DCs). In contrast, the restoration of A-SMase in melanoma cells not only reduced tumour growth and immunosuppression, but also induced a high recruitment at tumour site of effector immune cells with an antitumoural function. Indeed, we observed a poor homing of MDSCs and Tregs and the increased recruitment of CD8⁺ and CD4⁺ T lymphocytes as well as the infiltration of DCs and CD8⁺/CD44^high T lymphocytes. This study demonstrates that change of A-SMase expression in cancer cells is sufficient per se to tune in vivo melanoma growth and that A-SMase levels modulate immune cells at tumour site. This may be taken into consideration in the setting of therapeutic strategies.

Elevated chronic inflammatory factors and myeloid-derived suppressor cells indicate poor prognosis in advanced melanoma patients

Chronic inflammation is considered to be one of the hallmarks for tumor initiation and progression. Moreover, a long-term production and accumulation of inflammatory factors lead to a local and systemic immunosuppression associated with cancer progression. However, the correlation between inflammatory mediators, immunosuppressive cells and the clinical outcome of malignant melanoma patients was poorly investigated. In this study, we performed a complex analysis of various inflammatory factors, myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) in the peripheral blood of patients suffering from malignant melanoma of different stages. We demonstrated that levels of serum IL-1β, IFN-γ and CXCL10 were significantly increased in advanced melanoma patients. In addition, these factors were found to be associated with an increased frequency of MDSCs and Tregs as compared to age- and gender-matched healthy donors. Importantly, advanced melanoma patients with signs of progression displayed markedly elevated concentrations of IL-1β and CXCL10 as compared to patients with stable disease. Moreover, an enrichment of circulating monocytic (Mo)-MDSCs significantly correlated with a decreased progression free survival of these patients. Our data highlight a complex association between circulating inflammatory mediators, Mo-MDSCs and the clinical outcome as well as suggest that their levels in patients with advanced melanoma are of important prognostic value allowing the identification of those with high risk of disease progression.

Myeloid-derived suppressor cells in malignant melanoma

Melanoma is known for its rapid progression, metastasis to distant organs and therapeutic resistance. Despite high melanoma immunogenicity, the results of immunotherapeutic clinical studies are mostly unsatisfactory. One explanation is the development of strong immunosuppression mediated by highly immunosuppressive regulatory leukocytes, in particular, myeloid-derived suppressor cells (MDSCs). These cells were found to be enriched and activated in the melanoma microenvironment, inducing a profound impairment of anti-tumor immune responses and leading to the tumor progression. Therefore, understanding the mechanisms of MDSC generation, migration to the tumor site and activation as well as their targeting is important for the development of novel strategies for effective melanoma immunotherapy. We suggest that such therapeutic approaches should involve the inhibition of MDSC-mediated immunosuppressive melanoma microenvironment combined with other immunologic treatments.

Potential of long-chain n-3 polyunsaturated fatty acids in melanoma prevention

The possible antineoplastic activity of dietary long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs) has been supported by ample preclinical studies that have identified a number of molecular factors and pathways affected by these fatty acids and involved in cell growth, apoptosis, invasion, and angiogenesis. The aim of this critical review is to assess the current state of knowledge on the potential anticancer effects of LC n-3 PUFAs against malignant melanoma, one of the most common cancers among Western populations. The results of preclinical as well as human observational and interventional studies investigating the effects of LC n-3 PUFAs in melanoma were examined. Overall, the analysis of the literature reveals that, even though a large body of information is available, further effort is needed to identify the main molecular targets of LC n-3 PUFAs in melanoma. Moreover, additional well-designed human observational studies are essential to shed further light on the issue. The results of these studies could provide support and specific information for the development of clinical studies, especially those performed in combination with conventional or innovative antineoplastic therapies.

The cardioprotective protein apolipoprotein A1 promotes potent anti-tumorigenic effects

Here, we show that apolipoprotein A1 (apoA1), the major protein component of high density lipoprotein (HDL), through both innate and adaptive immune processes, potently suppresses tumor growth and metastasis in multiple animal tumor models, including the aggressive B16F10L murine malignant melanoma model. Mice expressing the human apoA1 transgene (A1Tg) exhibited increased infiltration of CD11b(+) F4/80(+) macrophages with M1, anti-tumor phenotype, reduced tumor burden and metastasis, and enhanced survival. In contrast, apoA1-deficient (A1KO) mice showed markedly heightened tumor growth and reduced survival. Injection of human apoA1 into A1KO mice inoculated with tumor cells remarkably reduced both tumor growth and metastasis, enhanced survival, and promoted regression of both tumor and metastasis burden when administered following palpable tumor formation and metastasis development. Studies with apolipoprotein A2 revealed the anti-cancer therapeutic effect was specific to apoA1. In vitro studies ruled out substantial direct suppressive effects by apoA1 or HDL on tumor cells. Animal models defective in different aspects of immunity revealed both innate and adaptive arms of immunity contribute to complete apoA1 anti-tumor activity. This study reveals a potent immunomodulatory role for apoA1 in the tumor microenvironment, altering tumor-associated macrophages from a pro-tumor M2 to an anti-tumor M1 phenotype. Use of apoA1 to redirect in vivo elicited tumor-infiltrating macrophages toward tumor rejection may hold benefit as a potential cancer therapeutic.

Silencing of CXCR4 by RNA interference inhibits cell growth and metastasis in human renal cancer cells

Renal cell carcinoma (RCC) is the third most common genitourinary malignancy, accounting for 3% of cancer in adults. The mortality and morbidity of RCC is strongly associated with its high propensity to metastasize to specific organs. This may be attributed to the fact that the CXCR4 G protein-coupled receptor (GPCR) on RCC cells mediates chemoattraction toward stromal-derived factor 1 (SDF-1) secreted by target organs. RNA interference (RNAi), which has been proven to be a powerful tool for suppressing gene expression, may lead to novel strategies for treating RCC. Our previous experiments confirmed that RCC A-498 cells overexpressing CXCR4 are associated with increased invasiveness. In this study, we constructed recombinant CXCR4-RNAi plasmids and transfected them into A-498 cells in vitro. Reverse transcription polymerase chain reaction (RT-PCR) and western blotting revealed that CXCR4 was downregulated in transfected cells compared with control cells. Our results from MTT and transwell migration assays indicated that specific downregulation of CXCR4 inhibited cell growth, invasiveness and migration. Flow cytometric analysis indicated that silencing of CXCR4 in A-498 cells by RNA interference induced cell apoptosis in RCC in vitro. Thus, siRNA targeting of CXCR4 can effectively inhibit the growth and metastasis of RCC cells and may be a promising innovative anticancer therapy.

Overexpression of the chemokine receptors CXCR4, CCR7, CCR9, and CCR10 in human primary cutaneous melanoma: a potential prognostic value for CCR7 and CCR10?

Multiple functional implications have been suggested for a limited number of chemokines and their cognate receptors in melanoma pathogenesis. The purpose of this study was to investigate the potential role of the chemokine receptors CXCR4, CCR7, CCR9, and CCR10 as prognostic markers in human primary cutaneous melanoma. Chemokine receptor expression was analyzed by immunohistochemistry in a total of 38 patients with cutaneous melanoma. Results were statistically correlated with melanoma features and clinical disease progression. No significant correlation between overexpression of CXCR4 or CCR9 and survival or prognosis was found. CCR7 overexpression was associated with significantly lower survival (0.005 log rank) and shorter time to progression (0.009 log rank)-similar to CCR10 overexpression (lower survival: 0.001 log rank, shorter time to progression: 0.002 log rank). In addition, CCR7 overexpression correlated with expression of metallothionein, while CCR10 seems to be associated with cerebral metastases. Two chemokine receptors permitting the identification of high-risk patients were identified: CCR7 and CCR10 overexpressions were found to be associated with a worse outcome of disease course independent of Breslow's tumor thickness and Clark level, thus representing possible additional prognostic markers.

Melanoma-induced immunosuppression and its neutralization

Malignant melanoma is characterized by a rapid progression, metastasis to distant organs, and resistance to chemo- and radiotherapy. Well-defined immunogenic capacities of melanoma cells should allow a successful application of different immunotherapeutic strategies. However, the overall results of immunotherapeutic clinical studies are not satisfactory. These paradoxical observations are supposed to be due to the profound immunosuppression mediated by different mechanisms dealing with alterations in tumor and surrounding stroma cells. Melanoma microenvironment has been characterized by a remarkable accumulation of highly immunosuppressive regulatory leucocytes, in particular, myeloid-derived suppressor cells (MDSCs). Their migration, retention and high activity in the tumor lesions have been demonstrated to be induced by chronic inflammatory conditions developing in the tumor microenvironment and characterized by the long-term secretion of various inflammatory mediators (cytokines, chemokines, growth factors, reactive oxygen and nitrogen species, prostaglandins etc.) leading to further cancer progression. Here, we discuss the role of chronic inflammation in the recruitment and activation of MDSCs in melanoma lesions as well as therapeutic approaches of MDSC targeting to overcome tumor immunosuppressive microenvironment induced by chronic inflammation and enhance the efficiency of melanoma immunotherapies.

Constitutive aberrant endogenous interleukin-1 facilitates inflammation and growth in human melanoma

Interleukin (IL)-1-mediated inflammation is proposed to contribute to the development and progression of some cancers. IL-1 family member proteins are known to be expressed constitutively in many melanoma tumor cells, and we hypothesize that these support molecular pathways of inflammation and facilitate tumor growth. To investigate the expression of IL-1α and IL-1β in melanoma patients, and their association with disease progression, immunohistochemical staining was carried out on tissues from 170 patients including benign nevi, primary melanomas, and metastatic melanomas. IL-1β levels were low (or zero) in benign nevi and higher in primary and metastatic melanomas (P < 0.0001). IL-1α was expressed in about 73% of nevi and 55% of metastatic melanomas, with levels significantly higher in primary tumors (P < 0.0001); most (98%) primary melanoma samples were positive for IL-1α. In vitro studies with seven human melanoma cell lines showed that five cell lines expressed IL-1α and IL-1β proteins and mRNA. We identified for the first time several important downstream signaling pathways affected by endogenous IL-1, including reactive oxygen and nitrogen species, COX-2, and phosphorylated NF-κB inhibitor (IκB) and stress-activated protein kinase/c-jun-NH(2)-kinase; all of which were decreased by siRNA to IL-1s. Downregulation of IL-1α, IL-1β, or MyD88 substantially increased p21 and p53 levels. Treatment with IL-1 receptor type I neutralizing antibody or IL-1 pathway-specific siRNAs led to growth arrest in IL-1-positive melanoma cells. Furthermore, blocking the IL-1 pathway increased autophagy in IL-1-positive melanoma cells. These results indicate that the endogenous IL-1 system is functional in most human melanoma and interrupting its signaling inhibits the growth of IL-1-positive melanoma cells.

Prognostic molecular biomarkers for cutaneous malignant melanoma

Molecular signatures of melanoma have propelled new approaches to early diagnosis, monitoring of treatment response, and targeted therapy. This review discusses messenger RNA (mRNA), genomic, and epigenomic melanoma biomarkers in blood and tissue specimens. The major focus is on tissue-based molecular assays to upstage sentinel lymph nodes (SLNs), and blood-based assays to detect melanoma progression by monitoring levels of circulating tumor cells (CTC) and circulating DNA.

A germline variant in the interferon regulatory factor 4 gene as a novel skin cancer risk locus

Genome-wide association studies on pigmentary phenotypes provide a pool of candidate genetic markers for skin cancer risk. The SNPs identified from a genome-wide association study of natural hair color were assessed for associations with the risk of three types of skin cancer simultaneously in a nested case-control study within the Nurses' Health Study [218 melanoma, 285 squamous cell carcinoma (SCC), and 300 basal cell carcinoma (BCC) cases, and 870 common controls]. Along with two known pigmentation loci, MC1R and OCA2, the IRF4 rs12203592 T allele was associated with an increased risk of each type of skin cancer (P value, 6.6 × 10(-4) for melanoma, 7.0 × 10(-7) for SCC, and 0.04 for BCC). This association was further replicated in additional samples (190 melanoma, 252 SCC, and 634 common controls). The P value in the replication set was 0.03 for melanoma and 4.2 × 10(-3) for SCC. The risk of BCC was replicated in an independent set of 213 cases and 718 controls (P value, 0.02). The combined results showed that the association with SCC reached the genome-wide significance level [odds ratio (OR) for additive model = 1.61, 95%CI, 1.36-1.91, P = 3.2 × 10(-8)]. The OR was 1.49 for melanoma (95%CI, 1.23-1.80; P = 4.5 × 10(-5)), and 1.32 for BCC (95%CI, 1.11-1.57; P = 1.6 × 10(-3)). Given that the T allele was shown previously to be associated with increased expression of IRF4 locus, further studies are warranted to elucidate the role of the IRF4 gene in human pigmentation and skin cancer development.

Angiogenesis and melanoma

Angiogenesis occurs in pathological conditions, such as tumors, where a specific critical point in tumor progression is the transition from the avascular to the vascular phase. Tumor angiogenesis depends mainly on the release by neoplastic cells of growth factors specific for endothelial cells, which are able to stimulate the growth of the host's blood vessels. This article summarizes the literature concerning the relationship between angiogenesis and human melanoma progression. The recent applications of antiangiogenic agents which interfere with melanoma progression are also described.

Inflammation and melanoma metastasis

Metastatic melanoma is extremely refractory to existing chemotherapeutic drugs and bioimmune adjuvant therapies, and the life span of patients with metastatic melanoma is often measured in months. Understanding the mechanisms responsible for the development of tumor metastasis is critical for finding successful curative measures. An expending amount of data reveal the importance of inflammatory microenvironment and stroma in cancer initiation and progression, which brings new directions and approaches to cancer treatment. This review will summarize current data on the role of the tumor microenvironment in shaping the metastatic phenotype of melanoma.

The good and the bad of chemokines/chemokine receptors in melanoma

Chemokine ligand/receptor interactions affect melanoma cell growth, stimulate or inhibit angiogenesis, recruit leukocytes, promote metastasis, and alter the gene expression profile of the melanoma associated fibroblasts. Chemokine/chemokine receptor interactions can protect against tumor development/growth or can stimulate melanoma tumor progression, tumor growth and metastasis. Metastatic melanoma cells express chemokine receptors that play a major role in the specifying the organ site for metastasis, based upon receptor detection of the chemokine gradient elaborated by a specific organ/tissue. A therapeutic approach that utilizes the protective benefit of chemokines involves delivery of angiostatic chemokines or chemokines that stimulate the infiltration of cytotoxic T cells and natural killer T cells into the tumor microenvironment. An alternative approach that tackles the tumorigenic property of chemokines uses chemokine antibodies or chemokine receptor antagonists to target the growth and metastatic properties of these interactions. Based upon our current understanding of the role of chemokine-mediated inflammation in cancer, it is important that we learn to appropriately regulate the chemokine contribution to the tumorigenic 'cytokine/chemokine storm', and to metastasis.

Chemokine receptor CXCR4 as a therapeutic target for neuroectodermal tumors

Chemokines (chemotactic cytokines) are a family of proteins associated with the trafficking and activation of leukocytes and other cell types in immune surveillance and inflammatory response. Besides their roles in the immune system, they play pleiotropic roles in tumor initiation, promotion, and progression. Chemokines can be classified into four subfamilies of chemokines, CXC, CC, C, or CX3C, based on their number and spacing of conserved cysteine residues near the N-terminus. This CXC subfamily can be further subclassified into two groups, depending on the presence or absence of a tripeptide motif glutamic acid-leucine-arginine (ELR) in the N-terminal domain. ELR(-)CXCL12, which binds to CXCR4 has been frequently implicated in various cancers. Over the past several years, studies have increasingly shown that the CXCR4/CXCL12 axis plays critical roles in tumor progression, such as invasion, angiogenesis, survival, homing to metastatic sites. This review focuses on involvement of CXCR4/CXCL12 interaction in neuroectodermal cancers and their therapeutic potentials. As an attractive therapeutic target of CXCR4/CXCL12 axis for cancer chemotherapy, development history and application of CXCR4 antagonists are described.

Chemokines and the microenvironment in neuroectodermal tumor-host interaction

Chemokines and chemokine receptors play an important role in immune homeostasis and surveillance. Altered or defective expression of chemokines and/or chemokine receptors could lead to a disease state including autoimmune disorder or cancer. Tumors from glioblastoma, melanoma, and neuroblastoma secrete high levels of chemokines that can promote tumor growth and progression or induce stromal cells present in the tumor microenvironment to produce cytokines or chemokines which, in turn, can regulate angiogenesis, tumor growth, and metastasis. On the other hand, chemokines secreted by tumor or stromal cells can also attract leukocytes such as dendritic cells, macrophages, neutrophils, and lymphocytes which may downmodulate tumor growth. New therapies that are aimed at limiting tumor growth and progression by attracting immune effector cells to the tumor site with chemokines may hold the key to the successful treatment of cancer, although this approach may be hampered by possible tumor growth-stimulating effects of chemokines.

Chemokines in neuroectodermal tumour progression and metastasis

Chemokines and their receptors have emerged as pivotal regulators of tumour growth, progression, and metastasis. Here we review the current knowledge on chemokines and receptors likely involved in the development of metastasis of neuroectodermal tumours, with emphasis on neuroblastoma. In this respect, we discuss the controversial role of the CXCR4/CXCL12 axis in bone marrow localization of neuroblastoma cells. In addition, we focus on the ability of neuroblastoma-derived chemokines such as CCL2 and CX3CL1 to attract lymphoid cells to the tumour site. Finally, chemokine receptor and function in other neuroectodermal tumours of adulthood (i.e. melanoma and small cell lung cancer) are discussed.

Chemokines in neuroectodermal cancers: the crucial growth signal from the soil

Although chemokines and their receptors were initially identified as regulators of cell trafficking during inflammation and immune response, they have emerged as crucial players in all stages of tumor development, primary growth, migration, angiogenesis, and establishment as metastases in distant target organs. Neuroectodermal tumors regroup neoplasms originating from the embryonic neural crest cells, which display clinical and biological similarities. These tumors are highly malignant and rapidly progressing diseases that disseminate to similar target organs such as bone marrow, bone, liver and lungs. There is increasing evidence that interaction of several chemokine receptors with corresponding chemokine ligands are implicated in the growth and invasive characteristics of these tumors. In this review we summarize the current knowledge on the role of CXCL12 chemokine and its CXCR4 and CXCR7 receptors in the progression and survival of neuroectodermal tumors, with particular emphasis on neuroblastoma, the most typical and enigmatic neuroectodermal childhood tumor.