Melanoma and vitiligo: immunology's Grecian urn

T cells and stromal fibroblasts in human tumor microenvironments represent potential therapeutic targets

The immune system of cancer patients recognizes tumor-associated antigens expressed on solid tumors and these antigens are able to induce tumor-specific humoral and cellular immune responses. Diverse immunotherapeutic strategies have been used in an attempt to enhance both antibody and T cell responses to tumors. While several tumor vaccination strategies significantly increase the number of tumor-specific lymphocytes in the blood of cancer patients, most vaccinated patients ultimately experience tumor progression. CD4+ and CD8+ T cells with an effector memory phenotype infiltrate human tumor microenvironments, but most are hyporesponsive to stimulation via the T cell receptor (TCR) and CD28 under conditions that activate memory T cells derived from the peripheral blood of the cancer patients or normal donors. Attempts to identify cells and molecules responsible for the TCR signaling arrest of tumor-infiltrating T cells have focused largely upon the immunosuppressive effects of tumor cells, tolerogenic dendritic cells and regulatory T cells. Here we review potential mechanisms by which human T cell function is arrested in the tumor microenvironment with a focus on the immunomodulatory effects of stromal fibroblasts. Determining in vivo which cells and molecules are responsible for the TCR arrest in human tumor-infiltrating T cells will be necessary to formulate and test strategies to prevent or reverse the signaling arrest of the human T cells in situ for a more effective design of tumor vaccines. These questions are now addressable using novel human xenograft models of tumor microenvironments.

Vitiligo-like Depigmentation Associated with Metastatic Melanoma of an Unknown Origin

Although malignant melanoma usually occurs after the diagnosis of vitiligo-like depigmentation, the latter is rarely followed by the former. We herein report on such a case in which recognition of the vitiligo-like depigmentation preceded diagnosing the metastatic melanoma by several months. A 56-year-old woman had first developed vitiligo-like depigmentation on the forehead, eyelids, neck and back 18 months previously and thereafter she detected a hard mass in the left axilla 2 months previously. Based on the histologic findings, the axillary mass was diagnosed as metastatic melanoma. To evaluate the primary tumor focus, thorough examinations that included PET-CT, bone scan and sigmoidoscopy were performed, but we couldn't find any the original primary tumor. Our case suggests that the vitiligo-like depigmentation could be a sign that heralds metastatic melanoma.

Vitiligo-like primary melanoma

Depigmented or hypopigmented macules and patches have been described in association to primary and metastatic melanoma. Primary melanoma presenting at the onset as a vitiliginous patch without histopathological evidence of regression seems to be a rare event. We report 2 patients with melanoma in situ that expressed clinically as vitiligo-like patches and review the possible immunologic mechanisms responsible for this unusual presentation.

Vitiligo associated with malignant melanoma and lupus erythematosus

There exists several reports where malignant melanoma is associated with vitiligo, vitiligo with discoid lupus erythematosus and lupus erythematosus with urticaria. However, there are no reports in which vitiligo, malignant melanoma, lupus erythematosus and urticaria coexist in the same case. Herein, we report a case of a patient who developed lupus erythematosus, malignant melanoma, vitiligo and urticaria simultaneously.

The course of melanoma-associated vitiligo: report of a case

The appearance of vitiligo-like lesions in patients with malignant melanoma is a well-known yet uncommon phenomenon. This finding is especially reported in patients undergoing immunotherapy with or without chemotherapy for malignant melanoma and is generally believed to be associated with a better prognosis. We report a case of preexisting vitiligo in a 48-year-old man, aggravated after chemo-immunotherapy of pulmonary metastatic melanoma with interferon-alpha, vinblastine and dacarbazine. Skin lesions remained stable after discontinuation of the treatment, and repigmentation heralded the recurrence of metastatic disease. These findings were in favor of vitiligo being a marker of the immunity against melanoma cells and its favorable impact on the prognosis of melanoma patients.

Initiation and regulation of CD8+T cells recognizing melanocytic antigens in the epidermis: implications for the pathophysiology of vitiligo

Antigen-specific CD8+T lymphocytes play an important role in defense against cutaneous microbial infection and skin cancer as well as in the pathophysiology of autoimmune skin disease such as lupus erythematodes and vitiligo. We have explored the role of CD8+ cytotoxic T lymphocytes (CTL) in an experimental mouse model of vitiligo, a pigmentation disorder characterized by focal loss of melanocytes in the skin. Using genetic immunization techniques we found that pigment cells in the epidermis can be destroyed by CD8+ T cells specifically recognizing a single H2-Kb-binding peptide derived from the model melanocytic self antigen tyrosinase-related protein 2 (TRP2), a melanosomal enzyme involved in pigment synthesis. Experimental evidence suggests that peripheral tolerance of pigment cell-specific cytotoxic CD8+T cells is regulated in two steps. In the induction phase, stimulation and expansion of these T cells in vivo strictly depends on CD4+ T cell help. In the effector phase, autoimmune destruction of melanocytes in the skin depends on local inflammation facilitating the migration of T cells into the epidermis and supporting effector functions. Our results suggest that accidental stimulation of CD8+ CTL recognizing MHC class I-binding peptides derived from melanocytic proteins in the context of an inflammatory skin disease may play an important role in the pathophysiology of vitiligo. Further investigations will address the role of chemokines, chemokine receptors and adhesion molecules in this experimental system and will reveal the role of keratinocytes and Langerhans cells in regulating cutaneous CD8+ T cell responses.

Peripheral CD8+ T Cell Tolerance Against Melanocytic Self-Antigens in the Skin Is Regulated in Two Steps by CD4+ T Cells and Local Inflammation: Implications for the Pathophysiology of Vitiligo

Experimental evidence has suggested a role for CD8+ cytotoxic T lymphocytes (CTL) in the pathophysiology of vitiligo, a pigmentation disorder with focal loss of melanocytes in the skin. The discovery of tyrosinase-related protein 2 (TRP2) as a model melanocytic self-antigen recognized by CD8+ CTL in C57BL/6 mice allowed us to analyze the requirements for CD8+ T cell-mediated autoimmune destruction of melanocytes in an experimental model. Using two different genetic methods for the induction of cellular immunity in vivo, gene gun bombardment of the skin and injection of recombinant adenovirus, we show that peripheral tolerance of CD8+ T cells recognizing a single TRP2-derived H2-Kb-binding peptide is regulated in two steps. In the induction phase, stimulation and expansion of TRP2-specific CD8+ T cells in vivo depend on CD4+ T cell help. In the effector phase, autoimmune destruction of melanocytes in the skin depends on local inflammation. Our results suggest that accidental stimulation of CD8+ CTL recognizing major histocompatibility complex class I-binding peptides derived from melanocytic proteins in the context of an inflammatory skin disease may play an important role in the pathophysiology of vitiligo.

Immunotherapy for melanoma

The immunogenicity of melanoma and the identification of melanoma-associated antigens is the basis for immunotherapy. This review will discuss the current status of melanoma immunotherapy with a focus on non-specific cytokines and highly specific vaccines, including peptides, viruses, dendritic cells, and whole cell vaccines. The passive transfer of melanoma-specific monoclonal antibodies and T-cells will also be reviewed. The problem of tumor escape and the association of immunotherapy to autoimmunity will be discussed. The use of immunotherapy in combination with other therapeutic agents and genetic profiling to predict responses suggests that immunotherapy will continue to play a role in the treatment of melanoma.

FAMMM syndrome: pathogenesis and management

Familial atypical multiple mole melanoma (FAMMM) syndrome is an autosomal dominant disorder with variable incomplete penetrance of the clinical phenotypes. Pathogenesis of this syndrome has not been fully investigated. Across multiple studies, germline mutations in the INK4a antioncogene encoding p16 protein were found on average in approximately 40% of the FAMMM syndrome. Patients with the FAMMM syndrome are genetically loaded with an increased risk of developing melanoma and other malignant neoplasms, for example, a pancreatic cancer. Melanoma can develop from numerous atypical moles as well as de novo. A proper diagnosis of the syndrome and early application of prophylactics decreases the risk of neoplastic transformation of melanocytes.

Natural mechanisms protecting against cancer

Carcinogenesis is a multistage process. At each step of this process, there are natural mechanisms protecting against development of cancer. The majority of cancers in humans is induced by carcinogenic factors present in our environment including our food. However, some natural substances present in our diet or synthesized in our cells are able to block, trap or decompose reactive oxygen species (ROS) participating in carcinogenesis. Carcinogens can also be removed from our cells. If DNA damage occurs, it is repaired in most of the cases. Unrepaired DNA alterations can be fixed as mutations in proliferating cells only and mutations of very few strategic genes can induce tumor formation, the most relevant are those activating proto-oncogenes and inactivating tumor suppressor genes. A series of mutations and/or epigenetic changes is required to drive transformation of a normal cell into malignant tumor. The apparently unrestricted growth has to be accompanied by a mechanism preserving telomeres which otherwise shorten with succeeding cell divisions leading to growth arrest. Tumor can not develop beyond the size of 1-2mm in diameter without the induction of angiogenesis which is regulated by natural inhibitors. To invade the surrounding tissues epithelial tumor cells have to lose some adhesion molecules keeping them attached to each other and to produce enzymes able to dissolve the elements of the basement membrane. On the other hand, acquisition of other adhesion molecules enables interaction of circulating tumor cells with endothelial cells facilitating extravasation and metastasis. One of the last barriers protecting against cancer is the activity of the immune system. Both innate and adaptive immunity participates in anti-tumor effects including the activity of natural killer (NK) cells, natural killer T cells, macrophages, neutrophils and eosinophils, complement, various cytokines, specific antibodies, and specific T cytotoxic cells. Upon activation neutrophils and macrophages are able to kill tumor cells but they can also release ROS, angiogenic and immunosuppressive substances. Many cytokines belonging to different families display anti-tumor activity but their role in natural anti-tumor defense remains largely to be established.

Isolation of the melanoma-associated antigen p23 using antibody phage display

The general responsiveness of human melanoma to immunotherapy has been well established, but active immunotherapy of melanoma has been hampered by insufficient information on the immunogenicity of melanoma-associated Ags in patients. In this study, we isolated a recombinant phage-Fab clone (A10-5) from a phage-Fab library derived from the B cells of a melanoma patient in remission after immunotherapy. Purified A10-5 Fab bound at high levels to cultured melanoma cell lines and to tissue sections of metastatic and vertical growth phase primary melanoma, but not to radial growth phase primary melanoma, nevi, or normal skin. A10-5 Fab bound to both the surface and the cytoplasm of cultured melanoma cells, but only to the cytoplasm of cultured fibroblasts. Western blot analysis revealed A10-5 Fab reactivity with a 33- and a 23-kDa glycoprotein under nonreducing conditions, and with a 23-kDa protein only under reducing conditions. A cDNA with an open reading frame predicted to encode a 23-kDa protein was cloned by screening a melanoma cell cDNA library with A10-5 Fab. This protein (p23) is the human homologue of the murine tumor transplantation Ag P198 that interacts with the cytoplasmic domain of ErbB-3 expressed by melanoma cells. Thus, the Ab phage display method has identified a novel, stage-specific melanoma-associated Ag that may have therapeutic and diagnostic value.

Local immune response in skin of generalized vitiligo patients. Destruction of melanocytes is associated with the prominent presence of CLA+ T cells at the perilesional site

In situ immune infiltrates in lesional, perilesional, and nonlesional skin biopsies from patients with vitiligo were analyzed by immunohistochemistry and compared with immune infiltrates found in the skin of normal healthy donors and relevant disease controls. An increased influx of activated skin-homing T cells and macrophages were seen in the perilesional biopsies. The overall percentages of cutaneous leukocyte-associated antigen-positive (CLA+) T cells were similar to those found in normal healthy donors. This is compatible with the similar expression of E-selectin. Most strikingly, however, the CLA+ T cells in perilesional skin were mainly clustered in the vicinity of disappearing melanocytes, and 60% to 66% of these interacting T cells expressed perforin and granzyme-B. The perforin+/granzyme-B+ cells were not seen in locations different from that of disappearing melanocytes. Interestingly, the majority of the infiltrating T cells were HLA-DR/CD8+. Another hallmark of the present study is the focal expression of intercellular adhesion molecule (ICAM)-1 and HLA-DR in the epidermis at the site of interaction between the immune infiltrates and the disappearing melanocytes. The data presented in this study are consistent with a major role for skin-homing T cells in the death of melanocytes seen in vitiligo.

Liposomes containing interferon-gamma as adjuvant in tumor cell vaccines

PURPOSE

Liposomal systems may be useful as a cytokine supplement in tumor cell vaccines by providing a cytokine reservoir at the antigen presentation site. Here, we examined the effect of liposome incorporation of mIFNgamma on its potency as adjuvant in an established tumor cell vaccination protocol in the murine B16 melanoma model. Adjuvanticity of the mIFNgamma-liposomes was compared to that achieved by mIFNgamma-gene transfection of the B16 tumor cells. Furthermore, we studied whether liposomal incorporation of mIFNgamma indeed increases the residence time of the cytokine at the vaccination site.

METHODS

C57B1/6 mice were immunized with i) irradiated IFNgamma-gene transfected B16 melanoma cells or ii) irradiated wild type B16 cells supplemented with (liposomal) mIFNgamma, followed by a challenge with viable B16 cells. The residence time of the (liposomal) cytokine at the subcutaneous (s.c.) vaccination site was monitored using radiolabeled mIFNgamma and liposomes.

RESULTS

Immunization with irradiated tumor cells admixed with liposomal mIFNgamma generated comparable protection against B16 challenge as immunization with mIFNgamma-gene modified tumor cells. Irradiated tumor cells admixed with soluble mIFNgamma did not generate any protective responses. Radiolabeling studies indicated that free mIFNgamma rapidly cleared from the s.c. injection site. Association of [125I]-mIFNgamma with liposomes increased the local residence time substantially: liposomal association of mIFNgamma resulted in a prolonged local residence time of the cytokine as reflected by a 4-fold increase of the area under the curve. The amount of released cytokine in the optimal dose range corresponds to the amount released by the gene-transfected cells. Moderate but significant CTL-activity against B16 cells was found for mice immunized with irradiated cells supplemented with mIFNgamma-liposomes compared to untreated control animals.

CONCLUSIONS

Prolonged presence of mIFNgamma at the site of antigen presentation is crucial for the generation of systemic immune responses in the B16 melanoma model. These studies show that liposomal encapsulation of cytokines is an attractive strategy for paracrine cytokine delivery in tumor vaccine development.

Liposomes as cytokine-supplement in tumor cell-based vaccines

Subcutaneous vaccination of C57bl/6 mice with irradiated B16 melanoma cells supplemented with liposomal interleukin-2 (IL2) or murine interferon-gamma (mIFNgamma), resulted in systemic protection in 50% of the animals, against a subsequent tumor cell challenge in a dose dependent manner. The protective efficacy was comparable to the efficacy of cytokine gene-modified cells as tumor vaccine, whereas irradiated B16 cells supplemented with soluble cytokine did not result in protective responses. In vivo evidence was obtained that the beneficial effects mediated by liposome incorporation of the cytokine are the result of a depot function of the liposomal cytokine supplement at the vaccination site. In can be concluded that liposomal delivery of cytokines offers an attractive alternative to cytokine-gene transfection of tumor cells for therapeutic vaccination protocols.

Anti-tyrosinase-related protein-2 immune response in vitiligo patients and melanoma patients receiving active-specific immunotherapy

Several melanosome glycoproteins have been shown to be antigenic in humans. Correlation of antigen-specific immune responses in patients with the autoimmune disease vitiligo, therapy-induced hypopigmentation, and cutaneous melanoma has not been well studied. We examined antibody responses to a melanocyte autoantigen, tyrosinase-related protein-2 (TRP-2), as it is highly expressed in cutaneous melanoma and melanocytes. TRP-2 recombinant protein was synthesized for western blot and affinity anti-TRP-2 enzyme-linked immunosorbent assay. We demonstrated that patients with malignant melanoma, vitiligo, and active-specific immunotherapy-induced depigmentation had significant anti-TRP-2 IgG titers. The highest level of anti-TRP-2 IgG response was found in vitiligo patients. Induction and enhancement of anti-TRP-2 IgG responses were observed in melanoma patients treated with a polyvalent melanoma cell vaccine containing TRP-2. Active-specific immunotherapy could induce and/or augment the TRP-2 IgG antibody titers. Melanoma patients who developed hypopigmentation and had improved survival after polyvalent melanoma cell vaccine had significantly augmented anti-TRP-2 antibody responses compared with patients with poor prognosis. This study demonstrates that TRP-2 autoantigen is immunogenic in humans. TRP-2 antibody responses provide a linkage between autoimmune responses by vitiligo patients and melanoma patients responding to immunotherapy who have induced hypopigmentation.

Antibody responses to melanoma/melanocyte autoantigens in melanoma patients

Melanogenesis-related proteins play important roles in melanin synthesis and antigenicity of melanomas. Identification of highly expressed melanoma-associated antigens (MAA) that are immunogenic in humans will provide potential targets for cancer vaccines. Melanogenesis-related proteins have been shown to be MAA. Autoantibody responses to these MAA have been shown to react with melanoma cells and melanocytes, and suggested to play a role in controlling melanoma progression. To assess antibody responses to potential melanoma/melanocyte autoantigens, the open-reading frame sequences of tyrosinase, tyrosinase-related protein (TRP)-1, TRP-2, and melanoma-associated glycoprotein antigen family (gp100/pmel17) genes were cloned and expressed as recombinant proteins in E. coli. Purified recombinant antigens were employed to detect antibodies in sera of melanoma patients and normal healthy donors. By affinity enzyme-linked immunosorbent assay and western blotting, all recombinant antigens were shown to be antigenic. The main subclass of antibody response to these antigens was IgG. Most importantly this study demonstrated anti-TRP-2 and anti-gp100/pmel17 IgG responses in melanoma patients. Only one of 23 normal donors had an antibody response to the antigens tested. MAA-specific IgG antibodies in sera were assessed in melanoma patients (n = 23) pre- and post-polyvalent melanoma cell vaccine treatment. Polyvalent melanoma cell vaccine treatment enhanced anti-MAA antibody responses; however, only anti-TRP-2 and anti-gp100/pmel17 antibody response was enhanced. These studies suggest that four melanogenesis-related proteins are autoimmunogenic and can be used as potential targets for active-specific immunotherapy.

Vitiligo

The destruction of melanocytes is the cause of depigmented maculae that clinically represent the disease vitiligo. Although the cause is unknown, various theories such as the autoimmune, autocytotoxic, and neural hypotheses have been proposed. Extensive research has provided numerous answers regarding the pathogenesis, histopathologic evidence, and treatment of vitiligo. This discussion of vitiligo summarizes the varied clinical presentations of the disease, theories attempting to explain the mechanism of melanocyte destruction, histopathologic findings, and different treatment modalities currently available.