Melanoma immunology: past, present and future

Advancements in Melanoma Therapies: From Surgery to Immunotherapy

OPINION STATEMENT

Melanoma is defined as the most aggressive and deadly form of skin cancer. The treatment of melanoma depends on the disease stage, tumor location, and extent of its spread from its point of origin. Melanoma treatment has made significant advances, notably in the context of targeted and immunotherapies. Surgical resection is the main therapeutic option for earlystage melanoma, and it provides favourable outcomes. With disease metastasis, systemic treatments such as immunotherapy and targeted therapy become increasingly important. The identification of mutations that lead to melanoma has influenced treatment strategies. Targeted therapies focusing on these mutations offer improved response rates and fewer toxicities than conventional chemotherapy. Furthermore, developing immunotherapies, including checkpoint inhibitors and tumor-infiltrating lymphocyte (TIL) therapies, has demonstrated encouraging outcomes in effectively combating cancer cells. These therapeutic agents demonstrate superior effectiveness and a more tolerable side-effect profile, improving the quality of life for patients receiving treatment. The future of melanoma treatment may involve a multimodal approach consisting of a combination of surgery, targeted therapy, and immunotherapy adapted to each patient's profile. This approach may improve survival rates and health outcomes.

New strategies for melanoma immunotherapy: How to overcome immunosuppression in the tumor microenvironment

Using ret transgenic mouse model of spontaneous melanoma, we showed an accumulation of melanoma antigen-specific memory T cells. However, their antitumor effects could be blocked by myeloid-derived suppressor cells, tolerogenic dendritic cells and regulatory T cells. We suggest that effective melanoma immunotherapy should include the neutralization of immunosuppressive tumor microenvironment.

Dispelling myths concerning pigmented skin lesions

The history of medicine is replete with examples of debunked myths, and in daily clinical dermatological practice, we must still counter many misconceptions regarding pigmented lesions, both with patients and other medical practitioners. Debunking myths and attempting to explain the reasons for these erroneous beliefs are the purposes of this review. The literature review has been partially guided by the results obtained from an online questionnaire conducted on an Italian website (www.vediamocichiara.it) from February 15, 2015 to March 15, 2015. The remaining discussed were selected on the basis of the existing literature and our personal experience. In order to explore these misconceptions, the following are the seven most salient questions that require investigation: (i) Is it dangerous to excise moles?; (ii) Is it dangerous to traumatize moles?; (iii) Are plantar moles worrisome?; (iv) Is it necessary to selectively apply sunscreen to moles?; (v) Is it inadvisable to partially biopsy a melanoma?; (vi) Do moles turn into melanoma?; and (vii) Is it necessary to perform sentinel lymph node biopsy for thin melanomas and for atypical Spitz naevi? Myths are ubiquitous, being prevalent in dermatological practice, with many of them concerning pigmented skin lesions. By encouraging critical analysis by patients and medical practitioners, the birth and perpetuation of myths can potentially be minimized, for the ultimate benefit of patients. This requires a scientific approach to be rigorously applied to dermatology, with critical questioning of unsubstantiated hypotheses including those emanating from the mass media as well as from respected sources.

Modulation of the myeloid compartment of the immune system by angiogenic- and kinase inhibitor-targeted anti-cancer therapies

Targeted therapies were rationally designed to inhibit molecular pathways in tumor cells critically involved in growth and survival; however, many drugs used in targeted therapies may affect the immune system. In addition, selected conventional chemotherapeutic agents have also been reported to be endowed with direct or indirect effects on immunity, for instance via immunogenic death of tumors. Thus, cancer therapies may have off-target effects, some of which are directed to the immune system. Here, we will review some of these effects in specific therapeutic approaches. We will examine the modulation of the immune contexture in human sarcoma and melanoma induced by anti-angiogenic therapies and by BRAF inhibitors, respectively. We will then discuss how the anti-tumor agent trabectedin is selectively cytotoxic to cells of the monocytic-macrophage lineage and how these immune-related effects can be part of the response to treatment.

Enrichment of CD56(dim)KIR + CD57 + highly cytotoxic NK cells in tumour-infiltrated lymph nodes of melanoma patients

An important checkpoint in the progression of melanoma is the metastasis to lymph nodes. Here, to investigate the role of lymph node NK cells in disease progression, we analyze frequency, phenotype and functions of NK cells from tumor-infiltrated (TILN) and tumor-free ipsilateral lymph nodes (TFLN) of the same patients. We show an expansion of CD56^dimCD57^dimCD69+CCR7+KIR+ NK cells in TILN. TILN NK cells display robust cytotoxic activity against autologous melanoma cells. In the blood of metastatic melanoma patients the frequency of NK cells expressing the receptors for CXCL8 receptor is increased compared to healthy subjects, and blood NK cells also express the receptors for CCL2 and IL6. These factors are produced in high amount in TILN and in vitro switch the phenotype of blood NK cells from healthy donors to the phenotype associated with TILN. Our data suggest that the microenvironment of TILN generates and/or recruits a particularly effective NK cell subset.

Heat-shock proteins-based immunotherapy for advanced melanoma in the era of target therapies and immunomodulating agents

INTRODUCTION

Heat-shock proteins (HSPs) are highly conserved, stress-induced proteins that function as chaperones, stabilizing proteins and delivering peptides. Tumor-derived HSP peptide complexes (HSPPCs) induced immunity against several malignancies in preclinical models, exhibiting activity across tumor types.

AREAS COVERED

HSPPC-based vaccination showed clinical activity in subsets of patients with different malignancies (e.g., gastric, colorectal, pancreatic, ovarian cancer, and glioblastoma). In Phase III clinical trials for advanced melanoma and renal cell carcinoma patients, HSPPC-based vaccine demonstrated an excellent safety profile, thus emerging as a flexible tumor- and patient-specific therapeutic approach.

EXPERT OPINION

Melanoma, renal clear cell carcinoma, and glioblastoma are among suitable targets for HSP-based treatment as demonstrated by immune responses and clinical activity observed in subsets of patients, mainly those with early stage of disease and limited tumor burden. In order to further improve clinical activity, combinations of HSPPC-based vaccines with mutation-driven therapies, antiangiogenic agents, or immunomodulating monoclonal antibodies should be tested in controlled clinical trials.

Two immune faces of pancreatic adenocarcinoma: possible implication for immunotherapy

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive human neoplasms, having extremely poor prognosis with a 5-year survival rate of <1 % and a median survival of 6 months. In contrast to other malignancies, pancreatic cancer is highly resistant to chemotherapy and targeted therapy. Therefore, new treatment options are urgently needed to improve the survival of patients with PDAC. Based on our data showing that patients with higher CD8+ T cell tumour infiltration exhibited prolonged overall and disease-free survival compared to patients with lower or without CD8+ T cell tumour infiltration, we suggested that immunotherapy could be a promising treatment option for PDAC. However, clinical data from the chemoradioimmunotherapy with interferon-α (IFN) trial did not point to an improved efficiency of chemoradiation combined with IFN as compared to chemoradiotherapy alone, suggesting an important role of the immune suppression induced by PDAC and/or unspecific immune stimulation. In support of this hypothesis, we found that the PDAC patients and experimental mice had an increased number of regulatory T cells and myeloid-derived suppressor cells. These results allowed us to conclude that PDAC provokes not only an anti-tumour immune response, but also strong immune suppression. Thus, we supposed that new immunotherapeutical strategies should involve not only stimulation of the immune system of PDAC patients, but also exert control over the tumour immune suppressive milieu.

[Personalized therapy concepts for malignant melanoma]

Metastatic melanoma is commonly regarded as one of the most difficult tumor entities to treat. Up to 2011 no systemic therapy had been able to achieve a prolongation of overall survival in controlled randomized trials. Cytotoxic chemotherapy resulted in objective remission in only a small subgroup of patients. The growing insight into the molecular pathology and the discovery of frequent mutations made it possible to define melanoma subgroups suitable for targeted therapies. In approximately 50% of melanomas activating mutations of the BRAF gene were identified and can be treated with specific inhibitors. Further mutations which can be approached by targeted therapies are found on the c-Kit and NRAS genes. Another promising approach is immunotherapy aimed to activate cytotoxic T cells. A monoclonal antibody directed against CTLA-4 was approved after convincing results in clinical trials and antibodies against PD-1 or PD-L1 are currently under clinical investigation. Through these achievements life prolonging therapies are available for melanoma patients for the first time.

Ret transgenic mouse model of spontaneous skin melanoma: focus on regulatory T cells

Ret transgenic mouse model of skin malignant melanoma is characterized by the overexpression of the human ret transgene in melanin-containing cells. Transgenic mice spontaneously develop skin tumors with metastases in lymph nodes, lungs, liver, brain, and the bone marrow. Tumor lesions show typical melanoma morphology and express melanoma-associated antigens. Although transgenic mice demonstrate an accumulation of melanoma antigen-specific memory and effector T cells, their anti-tumor effects could be blocked by highly immunosuppressive leukocytes enriched in the tumor microenvironment and in the periphery. Here, we discuss the role of one of the most potent immunosuppressive subset, regulatory T cells, in the melanoma progression in this model.

Intravenous delivery of siRNA targeting CD47 effectively inhibits melanoma tumor growth and lung metastasis

CD47 is a "self marker" that is usually overexpressed on the surface of cancer cells to enable them to escape immunosurveillance. Recognition of CD47 by its receptor, signal regulatory protein α (SIRPα), which is expressed in the macrophages, inhibits phagocytic destruction of cancer cells by the macrophages. In this study, we have first shown that clinical isolates of human melanoma significantly upregulate CD47, possibly as a mechanism to defend themselves against the macrophages. We then exploited RNA interference (RNAi) technology to test the hypothesis that knocking down CD47 in the tumor cells will render them targets for macrophage destruction; hence, creating a novel anti-cancer therapy. Anti-CD47 siRNA was encapsulated in a liposome-protamine-hyaluronic acid (LPH) nanoparticle (NP) formulation to address the challenge of targeted delivery of siRNA-based therapeutics in vivo. Efficient silencing of CD47 in tumor tissues with systemic administration of LPH(CD47) also significantly inhibited the growth of melanoma tumors. In a lung metastasis model, LPH(CD47) efficiently inhibited lung metastasis to about 27% of the untreated control. Moreover, no hematopoietic toxicity was observed in the animals that received multiple doses of LPH(CD47). Our findings indicate CD47 as a potential prognostic marker for melanoma development as well as a target for therapeutic intervention with RNAi-based nanomedicines.

Modulation of microenvironment acidity reverses anergy in human and murine tumor-infiltrating T lymphocytes

Stimulating the effector functions of tumor-infiltrating T lymphocytes (TIL) in primary and metastatic tumors could improve active and adoptive T-cell therapies for cancer. Abnormal glycolysis, high lactic acid production, proton accumulation, and a reversed intra-extracellular pH gradient are thought to help render tumor microenvironments hostile to roving immune cells. However, there is little knowledge about how acidic microenvironments affect T-cell immunity. Here, we report that lowering the environmental pH to values that characterize tumor masses (pH 6-6.5) was sufficient to establish an anergic state in human and mouse tumor-specific CD8(+) T lymphocytes. This state was characterized by impairment of cytolytic activity and cytokine secretion, reduced expression of IL-2Rα (CD25) and T-cell receptors (TCR), and diminished activation of STAT5 and extracellular signal-regulated kinase (ERK) after TCR activation. In contrast, buffering pH at physiologic values completely restored all these metrics of T-cell function. Systemic treatment of B16-OVA-bearing mice with proton pump inhibitors (PPI) significantly increased the therapeutic efficacy of both active and adoptive immunotherapy. Our findings show that acidification of the tumor microenvironment acts as mechanism of immune escape. Furthermore, they illustrate the potential of PPIs to safely correct T-cell dysfunction and improve the efficacy of T-cell-based cancer treatments.

T-Cell Mediated Immune Responses Induced in ret Transgenic Mouse Model of Malignant Melanoma

Poor response of human malignant melanoma to currently available treatments requires a development of innovative therapeutic strategies. Their evaluation should be based on animal models that resemble human melanoma with respect to genetics, histopathology and clinical features. Here we used a transgenic mouse model of spontaneous skin melanoma, in which the ret transgene is expressed in melanocytes under the control of metallothionein-I promoter. After a short latency, around 25% mice develop macroscopic skin melanoma metastasizing to lymph nodes, bone marrow, lungs and brain, whereas other transgenic mice showed only metastatic lesions without visible skin tumors. We found that tumor lesions expressed melanoma associated antigens (MAA) tyrosinase, tyrosinase related protein (TRP)-1, TRP-2 and gp100, which could be applied as targets for the immunotherapy. Upon peptide vaccination, ret transgenic mice without macroscopic melanomas were able to generate T cell responses not only against a strong model antigen ovalbumin but also against typical MAA TRP-2. Although mice bearing macroscopic primary tumors could also display an antigen-specific T cell reactivity, it was significantly down-regulated as compared to tumor-free transgenic mice or non-transgenic littermates. We suggest that ret transgenic mice could be used as a pre-clinical model for the evaluation of novel strategies of melanoma immunotherapy.

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.

Phenotype, function and clinical implications of myeloid-derived suppressor cells in cancer patients

The involvement of a smouldering microenvironment is currently considered a cancer hallmark and a required step for tumour cells to disable specific immunity while promoting angiogenesis and stroma remodelling. Nevertheless, the molecular pathways driving such aberrant interactions in human cancer and their actual implication in disease progression are still poorly defined. Here, we will report about the remarkable efforts devoted by our group as well as many other scientists to dissect this process focusing on tumour-mediated activation of myeloid dysfunctional pathways occurring in cancer patients. Indeed, myeloid-derived suppressor cells (MDSC), playing a crucial role as cellular regulators of immune responses, have been extensively shown to restrain tumour immunity through a vast array of molecular mechanisms and to promote tumour progression in different murine models. Although in mice the phenotypic features of these cells were defined initially rather generally by Gr1(+) and CD11b(+) co-expression, more recent studies have unravelled the actual complexity of this population and the existence of different cell subsets. This complexity is even more remarked in the human setting, where heterogeneous populations of myeloid cells with variable phenotype and immunosuppressive features have been described in patients affected by different types of tumours. The lack of homogeneous properties of human MDSC has made these cells a controversial and still unacknowledged player in cancer-related immune suppression and disease progression. Nevertheless, with the efforts of the scientific community, MDSC will soon reveal their key role thereby becoming novel targets for innovative therapeutic strategies.

Overcoming immunosuppression in the melanoma microenvironment induced by chronic inflammation

Malignant melanoma is known by its rapid progression and poor response to currently applied treatments. Despite the well-documented melanoma immunogenicity, the results of immunotherapeutic clinical trials are not satisfactory. This poor antitumor reactivity is due to the development of chronic inflammation in the tumor microenvironment characterized by infiltrating leukocytes and soluble mediators, which lead to an immunosuppression associated with cancer progression. Using the ret transgenic mouse melanoma model that closely resembles human melanoma, we demonstrated increased levels of chronic inflammatory factors in skin tumors and metastatic lymph nodes, which correlated with tumor progression. Furthermore, Gr1(+)CD11b(+) myeloid-derived suppressor cells (MDSC), known to block tumor-reactive T cells, were enriched in melanoma lesions and showed an enhanced immunosuppressive capacity. This MDSC accumulation was associated with a strong TCR ζ-chain downregulation in T cells suggesting that the tumor inflammatory microenvironment supports MDSC recruitment and immunosuppressive activity. Indeed, upon administration of phosphodiesterase-5 inhibitor sildenafil or paclitaxel in non-cytotoxic doses, we observed reduced levels of chronic inflammatory mediators in association with decreased MDSC amounts and immunosuppressive function. This led to a partial restoration of ζ-chain expression in T cells and to a significantly increased survival of tumor-bearing mice. CD8 T-cell depletion resulted in an abrogation of beneficial outcome of both drugs, suggesting the involvement of MDSC and CD8 T cells in the observed therapeutic effects. Our data imply that inhibition of chronic inflammation in the tumor microenvironment should be applied in conjunction with melanoma immunotherapies to increase their efficacy.

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.

Chronic inflammation promotes myeloid-derived suppressor cell activation blocking antitumor immunity in transgenic mouse melanoma model

Tumor microenvironment is characterized by chronic inflammation represented by infiltrating leukocytes and soluble mediators, which lead to a local and systemic immunosuppression associated with cancer progression. Here, we used the ret transgenic spontaneous murine melanoma model that mimics human melanoma. Skin tumors and metastatic lymph nodes showed increased levels of inflammatory factors such as IL-1β, GM-CSF, and IFN-γ, which correlated with tumor progression. Moreover, Gr1(+)CD11b(+) myeloid-derived suppressor cells (MDSCs), known to inhibit tumor reactive T cells, were enriched in melanoma lesions and lymphatic organs during tumor progression. MDSC infiltration was associated with a strong TCR ζ-chain down-regulation in all T cells. Coculturing normal splenocytes with tumor-derived MDSC induced a decreased T-cell proliferation and ζ-chain expression, verifying the MDSC immunosuppressive function and suggesting that the tumor inflammatory microenvironment supports MDSC recruitment and immunosuppressive activity. Indeed, upon manipulation of the melanoma microenvironment with the phosphodiesterase-5 inhibitor sildenafil, we observed reduced levels of numerous inflammatory mediators (e.g., IL-1β, IL-6, VEGF, S100A9) in association with decreased MDSC amounts and immunosuppressive function, indicating an antiinflammatory effect of sildenafil. This led to a partial restoration of ζ-chain expression in T cells and to a significantly increased survival of tumor-bearing mice. CD8 T-cell depletion resulted in an abrogation of sildenafil beneficial outcome, suggesting the involvement of MDSC and CD8 T cells in the observed therapeutic effects. Our data imply that inhibition of chronic inflammation in the tumor microenvironment should be applied in conjunction with melanoma immunotherapies to increase their efficacy.

Melanoma vaccines: developments over the past 10 years

Decades of preclinical evaluation and clinical trials into melanoma vaccines have yielded spectacular progress in our understanding of melanoma antigens and the immune mechanisms of tumor rejection. Key insights and the results of their clinical evaluation are reviewed in this article. Unfortunately, durable clinical benefit following vaccination remains uncommon. Two recent clinical advances that will impact on melanoma vaccine development are trials with inhibitors of CTLA-4 and oncogenic BRAF. Long-term therapeutic control of melanoma will require integration of specific active immunotherapy with these emerging successful therapies from the disparate fields of immune regulation and signal transduction.

Racial differences in survival after surgical treatment for melanoma

BACKGROUND

Surgical-treatment outcomes for melanoma in African Americans are poorly characterized as a result of low incidence of melanoma among African Americans. We examined differences by race in overall and melanoma-specific survival, stratified by receipt of surgical treatment and by specific types of surgical treatment.

METHODS

Data from the 1973-2004 public-use Surveillance, Epidemiology and End Results Program (SEER) were analyzed by Cox proportional hazard models to compare the effects of surgical treatments on overall and melanoma-specific survival in blacks, whites, and other race, controlling for confounding demographic and tumor-related variables.

RESULTS

Of 151,154 patients with first primary melanoma (148,883 whites, 789 blacks and 1,532 other race), 142,653 (94.4%) received surgical treatment. Among patients who received surgical treatment, 10-year melanoma-specific survival was lower in blacks (73%) than in whites (88%) and other race (85%); black patients were at significantly higher risk of overall and melanoma-specific mortality when compared with white (hazard ratio [HR] = 1.64, 95% confidence interval [CI] 1.44-1.86, P < 0.0001 and HR = 1.50, 95% CI 1.25-1.79, P < 0.0001, respectively) and with other race (HR = 1.55, 95% CI 1.31-1.85, P < 0.0001 and HR = 1.49, 95% CI 1.16-1.91, P = 0.0017, respectively). Blacks who underwent biopsy, wide excision and surgery not otherwise specified were at higher risk of overall mortality compared with whites with the same treatment.

CONCLUSION

Overall and melanoma-specific survival was lower in blacks undergoing surgical treatment for melanoma compared to both whites and other race. Reasons for these disparities remain poorly understood.

The immunological era in melanoma treatment: new challenges for heat shock protein-based vaccine in the advanced disease

INTRODUCTION

Tumor-derived heat shock protein (HSP)-peptide complexes (HSPPCs) induced immunity against malignancies in preclinical trials, working across tumor types and bypassing the need to identify single immunogenic peptides. These results paved the way for the use of human gp96 obtained from autologous tumor samples as an anti-cancer vaccine.

AREAS COVERED

Autologous tumor-derived HSP gp96 peptide complex (HSPPC-96) vaccine is emerging as a tumor- and patient-specific cancer vaccine, with confirmed activity in several malignancies. It has been tested in Phase III clinical trials in advanced melanoma and kidney cancer with evidence for efficacy in patients with earlier stage disease. HSPPC-96-based vaccine demonstrated an excellent safety profile, thus emerging as a novel therapeutic approach with a suggestive role in cancer therapy. This review summarizes work on the use of HSPPC-96 as an autologous anti-tumor vaccine in advanced melanoma. Data were retrieved by PubMed and Medline research and using the authors' personal experience.

EXPERT OPINION

Further investigations are needed to understand the biological basis of immune functions in order to improve the clinical outcome of HSP-based cancer therapy. In the near future, the combination of HSP-based vaccines with other biological compounds might represent a successful strategy in the therapy of advanced melanoma.

Clinical uses of GM-CSF, a critical appraisal and update

The role of granulocyte-macrophage-colony-stimulating factor (GM-CSF) in the supportive care of cancer patients has been evaluated with promising results. More recently, GM-CSF has been added to regimens for the mobilization of hematopoietic progenitor cells. An expanding role for GM-CSF in regulating immune responses has been recognized based upon its activity on the development and maturation of antigen presenting cells and its capability for skewing the immune system toward Th1-type responses. GM-CSF has been shown to preferentially enhance both the numbers and activity of type 1 dendritic cells (DC1), the subsets of dendritic cells responsible for initiating cytotoxic immune responses. The increase in DC1 content and activity following local and systemic GM-CSF administration support a role for GM-CSF as an immune stimulant and vaccine adjuvant in cancer patients. GM-CSF has shown clinical activity as an immune stimulant in tumor cell and dendritic cell vaccines, and may increase antibody-dependent cellular cytotoxicity. The successful use of myeloid acting cytokines to enhance anti-tumor responses will likely require the utilization of GM-CSF in combination with cytotoxic or other targeted therapies.

Dual targeting of tumor and endothelial cells by gonadotropin-releasing hormone agonists to reduce melanoma angiogenesis

We showed previously that GnRH receptors are expressed in melanoma cells; their activation reduces cell growth and metastatic behavior. Here, we investigated whether GnRH agonists might affect the expression of genes involved in melanoma progression. By genome-wide transcriptomic and real-time PCR analysis, we first observed that GnRH agonists decrease the expression of the pro-angiogenic factor vascular endothelial growth factor (VEGF) (all isoforms) in BLM melanoma cells. Then, we demonstrated that GnRH agonists specifically decrease the expression of the VEGF165 isoform as well as its secretion from BLM cells. These data suggested that activation of GnRH receptors might reduce the pro-angiogenic behavior of melanoma cells. To verify this hypothesis, we treated BLM cells with a GnRH agonist; the conditioned medium from these cells was tested to assess its capability to stimulate human umbilical vein endothelial cell (HUVEC) motility. The migration of HUVECs towards the conditioned medium of GnRH agonist-treated BLM cells was significantly lower than the migration of HUVECs toward the conditioned medium of untreated cells. Thus, GnRH agonists reduce the pro-angiogenic behavior of melanoma cells through a decreased production of bioactive VEGF. We then found that GnRH receptors are also expressed on HUVECs and that GnRH agonists reduce their ability to proliferate and to form capillary-like tubes when stimulated by VEGF. These findings suggest that GnRH agonists exert an anti-angiogenic activity indirectly by decreasing VEGF secretion from tumor cells and directly by counteracting the pro-angiogenic activity of the growth factor. These data might lead to the development of novel targeted approaches for melanoma.

Tumor-initiated inflammation overrides protective adaptive immunity in an induced melanoma model in mice

We studied the effect of the immune system on two differentially aggressive melanomas developing in mice on conditional deletion of the INK4A/ARF tumor suppressor gene, with concomitant expression of oncogene H-Ras(G12V) and a natural cancer-germline tumor antigen (TA). "Slow progressor" melanomas contained no activated T lymphocytes (TL). In contrast, "aggressive" melanomas were infiltrated by activated TLs lacking effector molecules and expressing high levels of PD-1, indicating an exhausted phenotype. Aggressive melanomas were also infiltrated by immature myeloid cells (IMC). Infiltration was associated with local inflammation and systemic Th2/Th17-oriented chronic inflammation that seemed to impair further activation of TLs, as tumor-specific T cells adoptively transferred into mice bearing aggressive melanomas were poorly activated and failed to infiltrate the melanoma. This immunosuppression also led to the incapacity of these mice to reject inoculated TA-positive tumors, in contrast to slow-progressing melanoma-bearing mice, which were responsive. To test the role of adaptive immunity in tumor progression, we induced melanomas in immunodeficient RagKO compound mice. These mice developed aggressive but not slow-progressing melanomas at a higher frequency and with a shorter latency than immunocompetent mice. Immunodeficient mice also developed abnormal inflammation and infiltration of IMCs in a manner similar to immunocompetent mice, indicating that this phenotype was not dependent on adaptive immunity. Therefore, tumor-intrinsic factors distinguishing the two melanoma types control the initiation of inflammation, which was independent of adaptive immunity. The latter delayed development of aggressive melanomas but was overridden by inflammation.

CD4(+)CD45RA(+)CXCR4 (+) lymphocytes are inversely associated with progression in stages I-III melanoma patients

The chemokine receptor CXCR4 was described as an independent predictor of poor prognosis in primary human melanoma. To investigate on a possible role of CXCR4 expression on peripheral blood lymphocytes (PBL) subsets, 195 patients with melanoma were evaluated for correlations between PBL subsets CXCR4 expressing and clinicopathological and prognostic features. One hundred ninety-five patients with stages I-III melanoma were enrolled in this study. Lymphocytes subsets were assayed by the direct fluorescence method for whole blood and staining with fluorochrome-conjugated monoclonal antibodies. Correlations between PBL subsets, baseline patient, and tumor features were studied by contingency tables and the chi(2) test. The Kaplan-Meier product limit method was applied to plot disease-free- and overall-survival curves. Univariate analysis was performed with the log-rank test. Cox proportional-hazards regression was used to analyze the effect of multiple risk factors on disease-free survival (DFS). Melanoma patients characterized by CD4(+)CD45RA(+)CXCR4(+) higher than 25% of PBL showed a longer DFS. Conversely, CD4(+)CD45RA(+)CXCR4(+) <25% increased the risk of relapse. The 5-year DFS rate was 76% for patients with CD4(+)CD45RA(+)CXCR4(+) lymphocytes <25% of PBL, and 94% for patients with CD4(+)CD45RA(+)CXCR4(+) >25% (p = 0.030 at log-rank test). Univariate and multivariate analysis for DFS confirmed the prognostic value of the CD4(+)CD45RA(+)CXCR4(+) lymphocytes. Although further studies are needed to better define the involved subpopulation, the detection of cellular subset CD4(+)CD45RA(+)CXCR4(+) is an easy and feasible evaluation of melanoma patients in concomitance with the established melanoma prognostic markers.

HSPPC-96 vaccine in metastatic melanoma patients: from the state of the art to a possible future

Heat-shock proteins are highly conserved, stress-induced proteins with chaperone function for trafficking and delivering peptides within the different compartments of the cell. Tumor-derived heat-shock protein-peptide complexes (HSPPCs) can be used for vaccination against malignancies. In particular, the HSPPC-96-based vaccine vitespen (formerly Oncophage) is the first autologous cancer vaccine made from individual patients' tumors that has shown encouraging results in clinical trials. In Phase I and II clinical trials, this vaccine has shown activity on different malignancies, such as gastric cancer, colorectal cancer, pancreatic cancer, non-Hodgkin's lymphoma and chronic myelogenous leukemia. In Phase III clinical trials in melanoma and kidney cancer, it demonstrated an excellent safety profile with almost no toxicity. Heat-shock protein-based vaccines can be considered as a novel therapeutic approach with a promising role in cancer management.

The oncolytic activity of Newcastle disease virus NDV-HUJ on chemoresistant primary melanoma cells is dependent on the proapoptotic activity of the inhibitor of apoptosis protein Livin

Patients with advanced melanoma usually do not benefit from conventional chemotherapy treatment. There is therefore a true need for a new kind of therapy for melanoma. One factor responsible for the poor prognosis of melanoma is the inhibitor of apoptosis protein (IAP) family member Livin. In this study, we applied a novel approach for the treatment of melanoma, using a unique strain of the oncolytic Newcastle disease virus (NDV-HUJ). We found that, unlike chemotherapeutic drugs, NDV-HUJ, a one-cycle replicating virus, overcomes the resistance to apoptosis of melanoma primary cultures that over express the Livin protein. In contrast, melanoma tumor cells that do not express Livin are relatively resistant to NDV-HUJ treatment. Furthermore, we show that NDV-HUJ-induced oncolysis is attributed to the dual function of Livin: although Livin inhibits apoptosis through the inhibition of caspases, under the robust apoptotic stimulation of NDV-HUJ, caspases can cleave Livin to create a truncated protein with a paradoxical proapoptotic activity. Thus, NDV-HUJ is a potent inducer of apoptosis that can overcome the antiapoptotic effect of Livin and allow cleavage of Livin into the proapoptotic tLivin protein. Moreover, the results indicate that the interferon system, which is functional in melanoma, is not involved in NDV-induced oncolysis. Taken together, our data offer the possibility of a new viral oncolytic treatment for chemoresistant melanoma.

Immunotherapy for neuroblastoma: turning promise into reality

Neuroblastoma is one of the commonest and most aggressive paediatric malignancies. The majority of children present with metastatic disease for which long-term survival remains poor despite intensive multi-modal therapies. Toxicity from current treatment regimes is already significant, and there is little room to further intensify therapy. Alternative treatment strategies are therefore needed in order to improve survival. Immunotherapy is an attractive therapeutic option for these children as it potentially offers a much more specific and less toxic treatment than conventional therapies. This review discusses the different immunotherapy strategies that may be useful in neuroblastoma, their advantages and disadvantages and the challenges that need to be overcome to successfully use them clinically.

Skin melanoma development in ret transgenic mice despite the depletion of CD25+Foxp3+ regulatory T cells in lymphoid organs

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) known to mediate self-tolerance were also shown to contribute to tumor progression. In mouse melanoma transplantation models, Treg depletion resulted in the stimulation of antitumor immune responses and tumor eradication. To study Treg in conditions close to the clinical situation, we used a ret transgenic mouse spontaneous melanoma model, which, in contrast to transplantation models, resembles human melanoma regarding clinical development. Significantly higher numbers of Treg were found in skin tumors and metastatic lymph nodes at early stages of melanoma progression compared with more advanced stages accompanied by the elevated CCR4 expression on Treg and higher production of its ligand CCL2 in tumor lesions. Numbers of tumor infiltrating Treg inversely correlated with Treg amounts in the bone marrow, suggesting their possible recruitment to melanoma lesions from this organ. The immunosuppressive function of Treg from transgenic tumor-bearing mice was similar to that from transgenic tumor-free mice or nontransgenic littermates. Although anti-CD25 mAb injections resulted in the efficient Treg depletion from lymphoid organs of transgenic mice, melanoma development was not significantly delayed. Furthermore, the treatment of mice with macroscopical tumors also failed to inhibit tumor progression, which correlated with the inability to deplete intratumoral Treg. We suggest that in the autochthonous melanoma genesis, other immunosuppressive cells could play an important role and replace immunosuppressive, tumor-promoting functions of Treg. Therefore, effective melanoma immunotherapy should include the inhibition of Treg migration into the tumor combined with neutralization of other immunosuppressive cells and factors in the tumor microenvironment.

Tumor antigen-specific FOXP3+ CD4 T cells identified in human metastatic melanoma: peptide vaccination results in selective expansion of Th1-like counterparts

We have previously shown that vaccination of HLA-A2 metastatic melanoma patients with the analogue Melan-A(26-35(A27L)) peptide emulsified in a mineral oil induces ex vivo detectable specific CD8 T cells. These are further enhanced when a TLR9 agonist is codelivered in the same vaccine formulation. Interestingly, the same peptide can be efficiently recognized by HLA-DQ6-restricted CD4 T cells. We used HLA-DQ6 multimers to assess the specific CD4 T-cell response in both healthy individuals and melanoma patients. We report that the majority of melanoma patients carry high frequencies of naturally circulating HLA-DQ6-restricted Melan-A-specific CD4 T cells, a high proportion of which express FOXP3 and proliferate poorly in response to the cognate peptide. Upon vaccination, the relative frequency of multimer+ CD4 T cells did not change significantly. In contrast, we found a marked shift to FOXP3-negative CD4 T cells, accompanied by robust CD4 T-cell proliferation upon in vitro stimulation with cognate peptide. A concomitant reduction in TCR diversity was also observed. This is the first report on direct ex vivo identification of antigen-specific FOXP3+ T cells by multimer labeling in cancer patients and on the direct assessment of the impact of peptide vaccination on immunoregulatory T cells.

Modified peptides in anti-cancer vaccines: are we eventually improving anti-tumour immunity?

The discovery of tumour antigens recognized by T cells and the features of immune responses directed against them has paved the way to a multitude of clinical studies aimed at boosting anti-tumour T cell immunity as a therapeutic tool for cancer patients. One of the different strategies explored to ameliorate the immunogenicity of tumour antigens in vaccine protocols is represented by the use of optimized peptides or altered peptide ligands, whose amino acid sequence has been modified for improving HLA binding or TCR interaction with respect to native epitopes. However, despite the promising results achieved with preclinical studies, the clinical efficacy of this approach has not yet met the expectations. Although multiple reasons could explain the relative failure of altered peptide ligands as more effective cancer vaccines, the possibility that T cells primed by modified tumour peptides might may be unable to effectively cross-recognize tumour cells has not been sufficiently addressed. Indeed, the introduction of conservative amino acid substitutions may still produce diverse and unpredictable changes in the HLA/peptide interface, with consequent modifications of the TCR repertoire that can interact with the complex. This could lead to the expansion of a broad array of T cells whose TCRs may not necessarily react with equivalent affinity with the original antigenic epitope. Considering the results presently achieved with this vaccine approach, and the emerging availability of alternative strategies for boosting anti-tumour immunity, the use of modified tumour peptides could be reconsidered.

Activation of p38 mitogen-activated protein kinase drives dendritic cells to become tolerogenic in ret transgenic mice spontaneously developing melanoma

PURPOSE

The purpose of the study was to investigate signaling molecules involved in the acquisition of tolerogenic properties by dendritic cells (DC) in ret transgenic mice with spontaneous melanoma progression and to target these molecules to overcome the barrier for effective melanoma immunotherapy.

EXPERIMENTAL DESIGN

DC functions and expression patterns of p38 mitogen-activated protein kinase (MAPK) in DCs were evaluated in a ret transgenic murine cutaneous melanoma model, which shows high similarity to human cutaneous melanoma with respect to clinical development. In contrast to transplantation melanoma models (like B16), this model allows the study of melanoma progression under conditions of natural interactions between tumor and host cells over time.

RESULTS

We showed a strong tumor infiltration with immature DCs and a reduction in the number of mature DCs in lymphoid organs during melanoma progression. DCs from melanoma-bearing mice secreted significantly more interleukin 10 and less interleukin 12p70, and showed a decreased capacity to activate T cells compared with DCs from tumor-free animals. Observed DC dysfunction was linked to considerable activation of p38 MAPK. Inhibition of its activity in spleen DCs from tumor-bearing mice led to normalization of their cytokine secretion pattern and T-cell stimulation capacity.

CONCLUSIONS

Our data show a critical role of constitutively activated p38 MAPK in the acquirement of tolerogenic pattern by DCs during melanoma progression that contributes to the suppression of antitumor T-cell immune responses. We suggest that new strategies of melanoma immunotherapy can include inhibitors of p38 MAPK activity in DCs.

Molecular pathogenesis of cutaneous melanocytic neoplasms

Melanoma is the deadliest form of skin cancer without an effective treatment. An understanding of the genetic basis of melanoma has recently shed light on some of the mechanisms of melanomagenesis. This review explores the major genes involved in familial and sporadic cutaneous melanoma with an emphasis on CDKN2A, CDK4, MC1R, and MAPK pathway targets (e.g., RAS and BRAF), apoptosis regulators (e.g., BCL-2, AKT, and APAF-1), and the tumor-suppressor genes TP53 and PTEN. New directions for therapeutics based on our current knowledge of the genes implicated in melanoma are also discussed.

Immunomodulation in the treatment of haematological malignancies

Despite the continuous advances in immunology and cancer biology, haematological malignancies are often incurable. Conventional chemotherapy and radiation are efficacious for some lymphoma and leukaemia, however relapse and progressive disease often occurs. The evidence that the immune system can play an essential role in controlling cancer progression provide a basis for the development of active therapies, such as immunization, aimed to evoke or amplify a tumour-specific immune response. However, the inability of the patient's own immune system to mount effective responses against tumour antigens is a major limit of vaccination approaches. The adoptive transfer of effectors of the adaptive immune system is an attractive strategy to circumvent the limitations of autologous immune responses. Donor lymphocyte infusion and the transfer of monoclonal antibodies (MoAbs) have been the first forms of adoptive therapy approved for clinical use and are still fundamental components of immunotherapy of haematological malignancies. Due to the continuous characterization of tumour-specific antigen, the development of tumour-tailored therapies that exploit the specificity of antibodies and T cell receptors (TCRs) is progressing rapidly. This review highlights the current advances in the field of adoptive immunotherapy of haematological malignancies, starting by elucidating the ongoing progress in passive transfer of MoAbs. We will also discuss recent advances in the adoptive transfer with tumour-specific high avidity T cells, which can be generated ex vivo by the transfer of gene constructs encoding single chain antibodies or TCRs, thus redirecting T cell specificity to selected tumour antigens. The ability to produce gene-modified T cells of desired specificity and defined functional activity may improve in the future T cell based immunotherapy of cancer.

Oncophage: step to the future for vaccine therapy in melanoma

Heat-shock proteins (HSPs) are a group of proteins whose expression is increased when the cells are exposed to elevated temperatures or other stressful conditions. This increase in expression is transcriptionally regulated. The function of HSPs is similar in virtually all living organisms, from bacteria to humans. Their expression also occur under non-stressful conditions, simply 'monitoring' the cell's proteins, i.e., they carry old proteins to the cell's 'recycling bin' and they help newly synthesized proteins fold properly. These activities are part of a cell's own repair system. HSPs are molecular chaperones for protein molecules. They are usually cytoplasmic proteins and they perform functions in various intracellular processes. Tumour-derived HSP-peptide complexes (HSPPCs) can be used for vaccination against malignancies. In particular, HSPPC-96 complex, called Vitespen (formerly Oncophage) is a HSPs-based vaccine made from individual patients' tumours with a promising role in cancer management. This vaccine has been extensively studied in Phase I and II clinical trials, showing activity on different malignancies, including gastric cancer, colorectal cancer, pancreatic cancer, non-Hodgkin's lymphoma and chronic myelogenous leukaemia. The vaccine has also been studied in Phase III clinical trials in melanoma and kidney cancer, showing an excellent safety profile with essentially no toxicity. Thus, HSP-based vaccines are a novel therapeutic approach with a promising role in cancer management.

Dendritic cell vaccination and immune monitoring

We exploited dendritic cells (DC) to vaccinate melanoma patients. We recently demonstrated a statistical significant correlation between favorable clinical outcome and the presence of vaccine-related tumor antigen-specific T cells in delayed type hypersensitivity (DTH) skin biopsies. However, favorable clinical outcome is only observed in a minority of the treated patients. Therefore, it is obvious that current DC-based protocols need to be improved. For this reason, we study in small proof of principle trials the fate, interactions and effectiveness of the injected DC.

Immune modulation by melanoma-derived factors

Melanomas, while the less common of skin cancers, are highly aggressive and once they metastasize usually indicate a poor prognosis. Melanomas are in many cases immunogenic and thus have been a prime target for immunotherapy, which has resulted in objective responses in some patients. To understand why antitumor immunity fails, and for the purpose of discovering new targets to improve therapy, there has been great interest to analyse the antitumor immune responses which exist in these patients, and uncover mechanisms which block tumor-specific immune responses. It is now evident that immunosuppressive cell networks and factors play a major role in the failure of the antitumor immune responses and therapies to eradicate the tumor. In this review, the factors produced by melanomas which can modulate and enhance these suppressive mechanisms are discussed. The roles of immature dendritic cells, neutrophils, T-regulatory cells, myeloid-derived suppressor cells and M2 macrophages or tumor-associated macrophages are described. Furthermore, taking into consideration of the cross-talk which exists among these different cell types and the cycle of immunosuppression which is evident in melanoma cancer patients and animal models, will be important for future therapeutic approaches.

The role of vaccine therapy in the treatment of melanoma

BACKGROUND

Melanoma is a tumour that is usually resistant to systemic therapy. Since it has been considered to be a highly immunogenic tumour, it has become an excellent target for the active specific immunotherapy. Vaccine therapy represents a novel approach to the treatment of melanoma.

OBJECTIVE

To evaluate different vaccines tested in stage III and/or IV melanoma patients.

METHODS

Systematic review of the published evidence on vaccine therapy in melanoma.

RESULTS

Melanoma vaccines can be classified into six groups: whole-cell vaccines, dendritic cell vaccines, peptide vaccines, ganglioside vaccines, DNA vaccines and viral vectors. The main characteristics of these vaccines including their advantages and disadvantages and the results from conducted trials are presented. Clinical responses to melanoma vaccines are still poor and currently there is no melanoma vaccine with a proven efficacy.

CONCLUSION

Vaccine therapy still remains an experimental therapy in patients with metastatic melanoma. Further research is required although a future therapy for advanced melanoma is probably a multimodal approach including vaccines, adjuvants and negative co-stimulatory blockade.

Extensive necrosis of visceral melanoma metastases after immunotherapy

BACKGROUND

The prognosis for metastatic melanoma remains poor even with traditional decarbazine or interferon therapy. 5-year survival is markedly higher amongst patients undergoing metastatectomy. Unfortunately not all are suitable for metastatectomy. Alternative agents for systemic therapy have, to date, offered no greater rates of survival beyond traditional therapy. A toll-like receptor 9 agonist, PF-3512676 (formerly known as CPG 7909) is currently being evaluated for its potential.

CASE PRESENTATION

We present the case of a 54-year-old Caucasian male with completely resected metastatic cutaneous melanoma after immunotherapy. The patient initially progressed during adjuvant high-dose interferon, with metastases to the liver, spleen, and pelvic lymph nodes. During an 18-month treatment period with PF-3512676 (formerly known as CPG 7909), a synthetic cytosine-phosphorothioate-guanine rich oligodeoxynucleotide, slow radiologic disease progression was demonstrated at the original disease sites. Subsequent excision of splenic and pelvic nodal metastases was performed, followed by resection of the liver metastases. Histologic examination of both hepatic and splenic melanoma metastases showed extensive necrosis. Subsequent disease-free status was demonstrated by serial positron emission tomography (PET).

CONCLUSION

Existing evidence from phase I/II trials suggests systemic treatment with PF-3512676 is capable of provoking a strong tumor-specific immune response and may account for the prolonged tumor control in this instance.