Tumor immunity as autoimmunity: tumor antigens include normal self proteins which stimulate anergic peripheral T cells

Trial watch: Peptide vaccines in cancer therapy

Prophylactic vaccination constitutes one of the most prominent medical achievements of history. This concept was first demonstrated by the pioneer work of Edward Jenner, dating back to the late 1790s, after which an array of preparations that confer life-long protective immunity against several infectious agents has been developed. The ensuing implementation of nation-wide vaccination programs has de facto abated the incidence of dreadful diseases including rabies, typhoid, cholera and many others. Among all, the most impressive result of vaccination campaigns is surely represented by the eradication of natural smallpox infection, which was definitively certified by the WHO in 1980. The idea of employing vaccines as anticancer interventions was first theorized in the 1890s by Paul Ehrlich and William Coley. However, it soon became clear that while vaccination could be efficiently employed as a preventive measure against infectious agents, anticancer vaccines would have to (1) operate as therapeutic, rather than preventive, interventions (at least in the vast majority of settings), and (2) circumvent the fact that tumor cells often fail to elicit immune responses. During the past 30 y, along with the recognition that the immune system is not irresponsive to tumors (as it was initially thought) and that malignant cells express tumor-associated antigens whereby they can be discriminated from normal cells, considerable efforts have been dedicated to the development of anticancer vaccines. Some of these approaches, encompassing cell-based, DNA-based and purified component-based preparations, have already been shown to exert conspicuous anticancer effects in cohorts of patients affected by both hematological and solid malignancies. In this Trial Watch, we will summarize the results of recent clinical trials that have evaluated/are evaluating purified peptides or full-length proteins as therapeutic interventions against cancer.

Trial watch: DNA vaccines for cancer therapy

The foundation of modern vaccinology dates back to the 1790s, when the English physician Edward Jenner uncovered the tremendous medical potential of prophylactic vaccination. Jenner’s work ignited a wave of nationwide vaccination campaigns abating the incidence of multiple life-threatening infectious diseases and culminating with the eradication of natural smallpox virus, which was definitively certified by the WHO in 1980. The possibility of using vaccines against cancer was first proposed at the end of the 19th century by Paul Ehrlich and William Coley. However, it was not until the 1990s that such a hypothesis began to be intensively investigated, following the realization that the immune system is not completely unresponsive to tumors and that neoplastic cells express immunogenic tumor-associated antigens (TAAs). Nowadays, anticancer vaccines are rapidly moving from the bench to the bedside, and a few prophylactic and therapeutic preparations have already been approved by FDA for use in humans. In this setting, one interesting approach is constituted by DNA vaccines, i.e., TAA-encoding circularized DNA constructs, often of bacterial origin, that are delivered to patients as such or by means of specific vectors, including (but not limited to) liposomal preparations, nanoparticles, bacteria and viruses. The administration of DNA vaccines is most often performed via the intramuscular or subcutaneous route and is expected to cause (1) the endogenous synthesis of the TAA by myocytes and/or resident antigen-presenting cells; (2) the presentation of TAA-derived peptides on the cell surface, in association with MHC class I molecules; and (3) the activation of potentially therapeutic tumor-specific immune responses. In this Trial Watch, we will summarize the results of recent clinical trials that have evaluated/are evaluating DNA vaccines as therapeutic interventions against cancer.

The profile of tumor antigens which can be targeted by immunotherapy depends upon the tumor's anatomical site

Previously, we showed that vesicular stomatitis virus (VSV) engineered to express a cDNA library from human melanoma cells (ASMEL, Altered Self Melanoma Epitope Library) was an effective systemic therapy to treat subcutaneous (s.c.) murine B16 melanomas. Here, we show that intravenous treatment with the same ASMEL VSV-cDNA library was an effective treatment for established intra-cranial (i.c.) melanoma brain tumors. The optimal combination of antigens identified from the ASMEL which treated s.c. B16 tumors (VSV-N-RAS+VSV-CYTC-C+VSV-TYRP-1) was ineffective against i.c. B16 brain tumors. In contrast, combination of VSV-expressed antigens-VSV-HIF-2α+VSV-SOX-10+VSV-C-MYC+VSV-TYRP1-from ASMEL which was highly effective against i.c. B16 brain tumors, had no efficacy against the same tumors growing subcutaneously. Correspondingly, i.c. B16 tumors expressed a HIF-2α(Hi), SOX-10(Hi), c-myc(Hi), TYRP1, N-RAS(lo)Cytc(lo) antigen profile, which differed significantly from the HIF-2α(lo), SOX-10(lo), c-myc(lo), TYRP1, N-RAS(Hi)Cytc(Hi) phenotype of s.c. B16 tumors, and was imposed upon the tumor cells by CD11b(+) cells within the local brain tumor microenvironment. Combining T-cell costimulation with systemic VSV-cDNA treatment, long-term cures of mice with established i.c. tumors were achieved in about 75% of mice. Our data show that the anatomical location of a tumor profoundly affects the profile of antigens that it expresses.

A new hope in immunotherapy for malignant gliomas: adoptive T cell transfer therapy

Immunotherapy emerged as a promising therapeutic approach to highly incurable malignant gliomas due to tumor-specific cytotoxicity, minimal side effect, and a durable antitumor effect by memory T cells. But, antitumor activities of endogenously activated T cells induced by immunotherapy such as vaccination are not sufficient to control tumors because tumor-specific antigens may be self-antigens and tumors have immune evasion mechanisms to avoid immune surveillance system of host. Although recent clinical results from vaccine strategy for malignant gliomas are encouraging, these trials have some limitations, particularly their failure to expand tumor antigen-specific T cells reproducibly and effectively. An alternative strategy to overcome these limitations is adoptive T cell transfer therapy, in which tumor-specific T cells are expanded ex vivo rapidly and then transferred to patients. Moreover, enhanced biologic functions of T cells generated by genetic engineering and modified immunosuppressive microenvironment of host by homeostatic T cell expansion and/or elimination of immunosuppressive cells and molecules can induce more potent antitumor T cell responses and make this strategy hold promise in promoting a patient response for malignant glioma treatment. Here we will review the past and current progresses and discuss a new hope in adoptive T cell therapy for malignant gliomas.

Trial Watch: Peptide vaccines in cancer therapy

Throughout the past 3 decades, along with the recognition that the immune system not only influences oncogenesis and tumor progression, but also determines how established neoplastic lesions respond therapy, renovated enthusiasm has gathered around the possibility of using vaccines as anticancer agents. Such an enthusiasm quickly tempered when it became clear that anticancer vaccines would have to be devised as therapeutic, rather than prophylactic, measures, and that malignant cells often fail to elicit (or actively suppress) innate and adaptive immune responses. Nonetheless, accumulating evidence indicates that a variety of anticancer vaccines, including cell-based, DNA-based, and purified component-based preparations, are capable of circumventing the poorly immunogenic and highly immunosuppressive nature of most tumors and elicit (at least under some circumstances) therapeutically relevant immune responses. Great efforts are currently being devoted to the identification of strategies that may provide anticancer vaccines with the capacity of breaking immunological tolerance and eliciting tumor-associated antigen-specific immunity in a majority of patients. In this sense, promising results have been obtained by combining anticancer vaccines with a relatively varied panels of adjuvants, including multiple immunostimulatory cytokines, Toll-like receptor agonists as well as inhibitors of immune checkpoints. One year ago, in the December issue of OncoImmunology, we discussed the biological mechanisms that underlie the antineoplastic effects of peptide-based vaccines and presented an abundant literature demonstrating the prominent clinical potential of such an approach. Here, we review the latest developments in this exciting area of research, focusing on high-profile studies that have been published during the last 13 mo and clinical trials launched in the same period to evaluate purified peptides or full-length proteins as therapeutic anticancer agents.

Immunobiology of malignant gliomas

The immune system of patients with malignant gliomas is profoundly suppressed. The suppression involves both the cellular and humoral immunity and it is mainly attributable to selective depletion and malfunction of helper T cells. Malignant glioma cells express potent immunosuppressive factors such as transforming growth factor-beta(2), inteleukin-10 and prostaglandin E(2). Malignant glioma cells also produce chemoattractants and immunostimulatory cytokines which may activate the immune cells. However, the production of these stimulatory cytokines is not self-destructive to glioma cells because of the immunosuppression. Rather, the tumour cells use them to gain a growth advantage. Indeed the cytokines may act as a growth stimulator of the tumour cells themselves (autocrine mechanism), they may act as angiogenic factors to endothelial cells (paracrine mechanism) or induce the attracted immune cells to secrete angiogenic factors. Some cytokines produced by malignant glioma cells are known to be growth inhibitory to normal astrocytes. Recent studies on tumour suppressor genes suggest a close link between the aberrant genes and the immunobiologic features of malignant glioma cells.

Pulsing with blast cell lysate or blast-derived total RNA reverses the dendritic cell-mediated cytotoxic activity of cytokine-induced killer cells against allogeneic acute myelogenous leukemia cells

Immunotherapeutic strategies may be a treatment option in patients with refractory acute myelogenous leukemia (AML) or, in cases of complete remission after conventional therapy regimens, may help to reduce disease recurrence or delay time to progression. Evidence suggests a key role of dendritic cells (DCs) in cancer immunotherapy due to their capacity to present tumour antigens to effector cells. We generated cytokine-induced killer (CIK) cells from healthy donors and examined their responses in vitro in an LDH release assay against three cell lines and allogeneic HLA non-matched blasts from three patients with de novo AML after coincubation with autologous peripheral blood monocyte-derived DCs. Although DCs were unable to enhance CIK cell effects against all three cell lines tested, the cytotoxic activity against the patients’ AML cells increased after coculture with mature DCs, which was significant in two of three patients. However, neither prior pulsing of the DCs with blast cell lysates nor with leukemic cell-derived total RNA further enhanced the lytic capacity of the CIK cells. On the contrary, pulsing reduced or even reversed the cytotoxic activity of the effector cells. This decrease of allogeneic cytotoxicity led us to conclude that monocyte-derived DCs may be useful in autologous or allogeneic vaccine strategies for the treatment of AML or in priming donor lymphocytes in vitro, but unfractionated antigens as pulsing agents may have inhibitory effects on T cell efficiency and their employment in immunotherapeutic strategies for AML seems questionable.

Induction of hsp70-mediated Th17 autoimmunity can be exploited as immunotherapy for metastatic prostate cancer

A close connectivity between autoimmune and tumor rejection responses is known to exist in the case of melanoma immunotherapy. However, relatively little is known about self-antigens on other types of normal cells, their relation to the development of autoimmune disease, and their possible coexistence as potential tumor rejection antigens on associated tumors. In the current study, we induced inflammatory killing of normal prostate tissue in situ using a fusogenic membrane glycoprotein along with the immune adjuvant hsp70. We show here that, in the prostate, hsp70 induces interleukin (IL)-6, which triggers a CD4- and CD8-dependent progressive autoimmune reactivity, associated with IL-17 expression. This autoimmune response was also able to induce the rejection of established prostate tumors, but not other histologic types of tumors, growing elsewhere in the animal. These data show that the intimate connectivity between autoimmune and tumor rejection responses extends beyond the classic melanoma paradigm and may be clinically valuable for the treatment of established metastatic disease of the prostate.

Killing of normal melanocytes, combined with heat shock protein 70 and CD40L expression, cures large established melanomas

Previously, we showed that nine intradermal injections of a plasmid in which the HSVtk suicide gene is expressed from a melanocyte-specific promoter (Tyr-HSVtk), combined with a plasmid expressing heat shock protein 70 (CMV-hsp70), along with systemic ganciclovir, kills normal melanocytes and raises a CD8+ T cell response that is potent enough to eradicate small, 3-day established B16 tumors. We show in this study that, in that regimen, hsp70 acts as a potent immune adjuvant through TLR-4 signaling and local induction of TNF-alpha. hsp70 is required for migration of APC resident in the skin to the draining lymph nodes to present Ags, derived from the killing of normal melanocytes, to naive T cells. The addition of a plasmid expressing CD40L increased therapeutic efficacy, such that only six plasmid injections were now required to cure large, 9-day established tumors. Generation of potent immunological memory against rechallenge in cured mice accompanied these therapeutic gains, as did induction of aggressive autoimmune symptoms. Expression of CD40L, along with hsp70, increased both the frequency and activity of T cells activated against melanocyte-derived Ags. In this way, addition of CD40L to the hsp70-induced inflammatory killing of melanocytes can be used to cure large established tumors and to confer immunological memory against tumor cells, although a concomitant increase in autoimmune sequelae also is produced.

Accumulation of low-avidity anti-melanocortin receptor 1 (anti-MC1R) CD8+ T cells in the lesional skin of a patient with melanoma-related depigmentation

Spontaneous or therapy-induced depigmentation in patients with melanoma has long been considered a favourable prognostic indicator. In this report, we isolated T cells infiltrating the depigmented skin of an HLA-A2+/DR4+ patient with melanoma, and detected a very high frequency of CD8+ T cells specific for melanocortin receptor 1 (MC1R), a hormone receptor involved in cutaneous pigmentation. In particular, tissue-infiltrating CD8+ T cells dominantly recognized the novel MC1R52-60 peptide epitope in an HLA-A2-restricted manner, and peptide-reactive CD8+ T cells were also detected in freshly isolated peripheral blood from this patient. Although type 1 CD4+ T-cell responses against MC1R were not detected in fresh tissue isolates, short-term in-vitro stimulation of peripheral blood lymphocytes resulted in the rapid expansion of CD4+ T cells reactive against novel HLA-DR4-presented epitopes derived from the MC1R protein (i.e. MC1R82-95, MC1R105-118 and MC1R149-161). MC1R peptide-specific CD8+ T-cell clones isolated from the depigmented skin of this patient were characterized by comparatively low functional avidity for specific major histocompatibility complex-peptide complexes and were poorly lytic; however, these effector cells were capable of secreting both interferon-gamma and granzyme B against relevant target cells in vitro, and may have played an important role in the induction of leucoderma in situ in this patient.

Tumor exosomes expressing Fas ligand mediate CD8+ T-cell apoptosis

Tumor-derived immune suppression is considered to be a major mechanism of tumor evasion from the immune system destruction, however, little is known regarding the induction of T-cell functional suppression by tumor-derived exosomes. Herein, we investigate tumor-derived exosomes involved in normal immunological communications as means of inhibiting an antitumor T-cell response. Exosomes derived from LNCaP, a human prostate cancer cell line, were visualized by FACS and identified based on size (80-200 nm) in comparison to marker beads. Exosomes from tumor cell line inhibited T-cell proliferation. Dose-dependent apoptosis of T cells was induced by co-culture with tumor exosomes. Addition of anti-FasL antibody blocked the apoptosis induction by tumor exosomes. This study suggests that induction of T-cell apoptosis by tumor-derived exosomes appears to be a novel mechanism of tumor immune evasion.

Potent selection of antigen loss variants of B16 melanoma following inflammatory killing of melanocytes in vivo

We have reported that i.d. injection of plasmids encoding hsp70 and a suicide gene transcriptionally targeted to melanocytes generates specific proinflammatory killing of melanocytes. The resulting CD8+ T cell response eradicates systemically established B16 tumors. Here, we studied the consequences of that CD8+ T cell response on the phenotype of preexisting tumor. In suboptimal protocols, the T cell response selected B16 variants, which grow extremely aggressively, are amelanotic and have lost expression of the tyrosinase and tyrosinase-related protein 2 (TRP-2) antigens. However, expression of other melanoma-associated antigens, such as gp100, was not affected. Antigen loss could be reversed by long-term growth in culture away from immune-selective pressures or within 96 hours by treatment with the demethylating agent 5-azacytidine (5-Aza). When transplanted back into syngeneic animals, variants were very poorly controlled by further vaccination. However, a combination of vaccination with 5-Aza to reactivate antigen expression in tumors in situ generated highly significant improvements in therapy over treatment with vaccine or 5-Aza alone. These data show that inflammatory killing of normal cells activates a potent T cell response targeted against a specific subset of self-antigens but can also lead to the immunoselection of tumor variants. Moreover, our data indicate that emergence of antigen loss variants may often be due to reversible epigenetic mechanisms within the tumor cells. Therefore, combination therapy using vaccination and systemic treatment with 5-Aza or other demethylating agents may have significant therapeutic benefits for antitumor immunotherapy.

A simple method to cure established tumors by inflammatory killing of normal cells

We describe a simple technology used to cure an established metastatic disease. Intradermal injection of plasmid DNA encoding a transcriptionally targeted cytotoxic gene, along with hsp70, not only promoted tissue-specific, inflammatory killing of normal melanocytes, but also induced a CD8(+) T-cell-dependent, antigen-specific response in mice that eradicated systemically established B16 tumors. This CD8(+) T cell response was subsequently suppressed in vivo within a few days. The data demonstrate that deliberate destruction of normal tissue can be exploited to generate immunity against a malignant disease originating from that tissue. This approach obviates the need to identify tumor antigens and does not require complex isolation of tumor cells or their derivatives. In addition, it provides a model system for studying the mechanisms underlying the etiology and control of autoimmune diseases. Finally, despite targeting normal tissue, therapy could be separated from development of overt autoimmune symptoms, suggesting that the strategy may be valuable against tumors derived from both non-essential and essential tissue types.

Core-binding factor-β positive acute myeloid leukaemia cells induce T-cell responses

The addition of specific cytokines is a mandatory prerequisite for the generation and subsequent function of leukaemia-derived dendritic cells (DC) believed to induce specific T-cell responses. In this study, we report the ability of blasts derived from cytogenetically classified acute myeloid leukaemia (AML) cells with the inversion of chromosome 16 to stimulate allogeneic and autologous T cells without additional cytokines. They displayed a measurable immunogenic effect. Sixteen of 17 established, stable AML cell lines, growing primary tumour cells from patients with a variety of chromosomal abnormalities, altered their surface marker expression pattern in proliferating culture. They lost the progenitor markers CD33, CD13 and CD34 while significantly increasing expression of the co-stimulatory molecules CD80 and CD86. Four cell lines derived from inv(16) positive blasts mounted allogeneic as well as autologous T cell activation with concomitant expression of CD25 and CD69. Moreover, oligoclonal expanded T cells were able to lyse inv(16) AML blasts in a specific major histocompatibility complex class I-restricted and CD80-dependent manner. AML blasts with karyotypes other than inv(16) activated T cells, but without inducing a significant proliferation. We conclude from this study that AML blasts derived from inv(16) positive patients may be preferential targets for AML immunotherapy strategies.

Melanocyte-specific immune response in melanoma and vitiligo: two faces of the same coin?

The appearance of depigmentation during the course of malignant melanoma has been considered a good prognostic sign. Is it only a side-effect, informative of the immune system's response to the treatment, or does it act as a necessary amplifier of these clinically important anti-tumor responses? The current review will attempt to tackle this question by reviewing the current literature, as well as by posing some novel hypotheses. Understanding the nature of humoral and cellular immune responses directed against normal melanocytes and their malignant counterparts may lead to the design of improved therapeutic strategies relevant to both vitiligo and melanoma.

Immunologic mechanisms of antitumor activity

The growth and metastatic spread of tumors, to a large extent, depends on their capacity to evade host immune surveillance and overcome host defenses. All tumors express antigens that are recognized to a variable extent by the immune system, but in many cases an inadequate immune response is elicited because of partial antigen masking or ineffective activation of effector cells. Tumor antigens presented in the context of major histocompatability antigen (MHC) class I complexes on either the tumor cell itself or on antigen-presenting cells are capable of inducing tumor-specific cytotoxic T lymphocytes. The presence of costimulatory molecules, such as B7-1 and B7-2, on antigen-presenting cells and the secretion of IL-2 promote the differentiation of recruited CD8+ lymphocytes into cytotoxic T lymphocytes. Tumor escape from immune effectors is most often caused by weak immunogenicity of tumor antigens, antigen masking, or overall immunosuppression, a characteristic of advanced cancer. Failure of antigen processing or binding to MHC molecules, inadequate or low-affinity binding of MHC complexes to T-cell receptors, or inadequate expression of costimulatory adhesion molecules in conjunction with the antigen-presenting MHC complex may all lead to poor immunogenicity of tumor-associated peptides and impaired antitumor response. Therapeutic interventions to augment tumor antigenicity include vaccination with immunogenic peptides, administration of in vitro expanded and activated immune effector cells, in vivo effector cell expansion with cytokine therapies, or genetic modification of either immune effectors or tumor cells with cytokine genes or genes encoding costimulatory molecules to effectively activate the immune response.

RNA as a tumor vaccine: a review of the literature

Many approaches have been attempted to harness the host immune system to act against malignant tumors. These have included animal and clinical trials with agents to non-specifically boost immunity, factors to augment specific immunity, transfer of lymphokine-activated killer cells and transfer of expanded populations of tumor-infiltrating lymphocytes. Therapeutic vaccination strategies have been employed using tumor extracts, purified tumor antigens, recombinant peptide tumor antigens and specific DNA sequences coding for a tumor antigen (genetic vaccination) both through direct administration to the host and by administration of antigen presenting cells exposed to these materials ex vivo. Recently, the use of RNA has been proposed for use in tumor vaccination protocols. The use of RNA has several potential advantages. Since total cellular RNA or mRNA can be utilized, it is not necessary to know the molecular nature of the putative tumor antigen(s). RNA can be effectively amplified; thus, unlike tumor-extract vaccines, only a small amount of tumor is needed to prepare the material for vaccination. Also, unlike DNA-based vaccines, there is little danger of incorporation of RNA sequences into the host genome. The possible utility of RNA-based vaccines for tumor immunotherapy should be further explored to determine whether such approaches are clinically useful.

A symbiotic concept of autoimmunity and tumour immunity: lessons from vitiligo

Vitiligo is a skin disease in which melanocytes (MCs) are eradicated from lesional epidermis, resulting in disfiguring loss of pigment. MCs are destroyed by MC-reactive T cells, as well as other non-immune and immune components. Similarities exist between the autoimmunity observed in vitiligo and the tumour immunity observed in melanoma immuno-surveillance. An analysis of these mechanisms might lead to the development of new therapies for both vitiligo and melanoma.

Immunotherapy: on the edge between experimental and clinical oncology

Cancer immunotherapy is still largely confined to the laboratory bench and experimental animal models. Yet the field is rapidly moving forward and some immunological tools are now entering into clinical use. The first and perhaps best example of such progress is given by bioengineered humanized monoclonal antibodies of which some have been already approved for therapy in B-cell lymphoma and breast cancer. Unexpectedly, another remarkable form of immunotherapy has turned out to derive from T-cell adoptive therapy associated with allogeneic bone marrow transplantation. Its benefits render such an approach the first choice therapy for a large number of hematological malignancies and it is now being adapted also for treatment of advanced solid tumors. Finally, harnessing the immune system against the autologous tumor remains the most ambitious but still distant design for immunotherapy. Recent technical advances and a better understanding of the immune system in cancer patients should concur in defining the best strategy for active immunotherapy in clinical oncology.

Cytokines in cancer therapy

Cytokines are crucial factors in the activation and development of immune response, including responses against tumor cells. Interleukin (IL)-2, a T-cell growth factor, has been largely used to activate T and NK cells in vivo and to maintain such an activation for therapeutic purposes. When given to patients, IL-2 was shown to cause clinical responses, especially in metastatic melanoma and renal cancer patients, though its mechanism of action could not be completely elucidated. Cytokines (IL-2, IL-12, GM-CSF) are also used as natural adjuvants of vaccines of various formulation to help in activating and maintaining an antitumor immune response. This review summarizes findings deriving from the use of cytokines in cancer therapy and provides insights into future approaches when a more appropriate use of cytokines, together with new vaccines, is likely to improve clinical outcome.

Cancer gene therapy: hard lessons and new courses

Gene therapy for the treatment of cancer was initiated with high levels of optimism and enthusiasm. Recently, this perception has had to be tempered by the realisation that efficiency and accuracy of gene delivery remain the most significant barriers to its success. So far, there has been a disappointing inability to reach target cells with sufficient efficacy to generate high enough levels of direct killing and this has necessitated the invocation of bystander effects in order for any potential strategy to be convincing. At least in the foreseeable future, clinical advance will come from co-operation with other more established disciplines - such as chemotherapy, radiotherapy and immunotherapy. This is inevitable - and necessary - in order to prove that gene therapy can have efficacy as part of a combinatorial therapy, before hoping to move clinical mountains alone. In addition, there will have to be a thorough understanding of the clinical situations in which gene therapy will be used in order both to understand its own limitations, and to exploit its full potential. This will enable it to find the appropriate clinical niche in which its abilities will be optimally useful. Finally, anyone wishing to practise clinical cancer gene therapy will rapidly have to learn the ways of the free market and be able to juggle commercial necessities with ideological purity. Gene Therapy (2000) 7, 2-8.

Are natural antibodies involved in tumour defence?

Natural antibodies (NAb) are found in the serum of healthy individuals. These antibodies are produced without any apparent specific antigenic stimulation. They are one part of the circulating immunoglobulins and are found in virtually all vertebrate species. NAb react to various self- and non-self antigens. A protective function in different infection models could be demonstrated. Several groups have reported the ability of NAb to bind to tumour cells. Their possible role in tumour defence is documented in mice. The present status of attempts to characterise the role of NAb in tumour defence is discussed, particularly as regards the human immune system. This paper focuses on antibody cell interactions and discusses the genetic background of the Nab-producing B-cells.

Cutting Edge: Passive But Not Active CD8+ T Cell-Based Immunotherapy Interferes with Liver Tumor Progression in a Transgenic Mouse Model

To evaluate tumor immunotherapies, we used transgenic mice that harbor a progressive liver tumor associated with the expression of the SV40 large tumor T oncoprotein (SV40-T). To induce “self” tumor Ag-specific CD8+ T cells, mice were injected with an immunodominant SV40-T CTL epitope mixed with a heterologous helper peptide. Despite repeated injections, this vaccine failed to raise a tumor-specific CD8+ T cell response that was efficient enough to counteract tumors. Although coimmunization with SV40-T CTL epitope and heterologous helper peptide efficiently recruited the respective Th cells, only low-avidity SV40-T-specific CD8+ T cells were activated. Furthermore, major alterations in SV40-T-specific B and Th cell responses were characterized. In contrast, transfers of higher-avidity CTLs specific for the same SV40-T epitope were effective in counteracting tumors. These results suggest that passive therapies targeted to self tumor Ag may be more suitable than active immunization in the treatment of spontaneous tumors.

Antitumor Effect of CD40 Ligand: Elicitation of Local and Systemic Antitumor Responses by IL-12 and B7

The interaction between CD40 ligand (CD40L, CD154) and its receptor CD40 has been implicated in the establishment of cell-mediated immunity as well as humoral immune responses. To examine the role of CD40L in eliciting antitumor immunity, we introduced murine CD40L gene into P815 mastocytoma (CD40L-P815). CD40L-P815 cells underwent prompt rejection when inoculated s.c. into syngenic DBA/2 mice or athymic BALB/c nu/nu mice, which was mediated by NK cells and dependent on endogenous IL-12. The primary rejection of CD40L-P815 cells in DBA/2 mice elicited CD8+ T cell-mediated protective and systemic immunity against parental tumor cells, which was induced by CD4+ T cells and endogenous B7. These results indicated a potent antitumor effect of CD40L that is mediated by potentiation of host Ag-presenting cell functions, and introduction of CD40L will be useful as a new strategy of immuno-gene therapy against tumors.

Future perspectives in specific immunotherapy of melanoma

With the discovery of T-cell recognised tumour-associated antigens (TAAs), interest in specific immunotherapy for treatment of malignancies has increased substantially. The majority of studies investigating TAAs have focused on melanoma-associated antigens because of evidence that the immune system influences the pathogenesis of melanoma. This paper reviews the different types of melanoma antigens, their in vitro and in vivo immunogenicity and clinical data regarding the use of specific immunotherapy in patients with stage I-IV melanoma. Results of clinical studies are highly variable but encourage further research in these patients. Developing and perfecting laboratory and clinical correlates of response to these specific immunotherapies are vital to determining their role in clinical practice.

Regulation of CD80/B7-1 and CD86/B7-2 molecule expression in human primary acute myeloid leukemia and their role in allogenic immune recognition

Clinical data and animal models afford evidence for anti-leukemia immunity in humans, but the interactions critical for blast cell recognition are unresolved. Expression of B7 molecules by antigen-presenting cells (APC) provides co-stimulatory signals to T lymphocytes via CD28 and CTLA-4 which prevent the induction of alloantigen-specific tolerance. Conversely, expression of CD40 ligand by stimulated T cells activates APC via CD40. In human hematological B cell malignancies (follicular lymphoma and chronic lymphocytic leukemia), the defect in alloantigen presentation of tumoral cells can be repaired by up-regulation of B7 and other co-stimulatory molecules via CD40. We studied the role of B7 molecules in alloimmune recognition and the various ways to improve the antitumoral response on peripheral blood leukemic cells from 20 patients with a diagnosis of primary acute myeloid leukemia (AML). We focused on myelo/monocytic M4/M5 French-American-British classification subtypes which are considered as the neoplastic counterpart of normal monocytes, a prototypic APC. In one-way mixed lymphocyte reaction of CD4+ T cells against leukemic cells, differences in B7-1, B7-2 or CD40 expression by AML cells did not induce specific cytokine secretion; interleukin (IL)-2 and interferon (IFN)-gamma were detected but not IL-4, corresponding to a Th1 pattern. Blockade experiments showed that proliferation and IFN-gamma secretion only partially depended on B7 molecules, which in contrast had a pivotal role in IL-2 synthesis. In contrast with murine models which suggest a pivotal role for CD80/B7-1 in the immune response against AML, our data support a greater role for CD86/B7-2, in line with the baseline expression of CD86/B7-2 and lack of CD80/B7-1 on most M4/M5 AML cells. AML cell stimulation via CD40: (1) significantly improved IL-2 secretion but not proliferation of responding T lymphocytes, (2) increased CD54/ICAM-1 expression in three quarters of cases, (3) failed in most cases to induce CD40-specific CD80/B7-1 up-regulation, and (4) had a weak effect on CD86/B7-2 expression. These data contrast with the very efficient up-regulation of both B7 co-stimulatory molecule expression and tumoral cell alloimmune recognition following CD40 stimulation in B cell malignancy models. The role of the defective B7 molecule up-regulation by the CD40 pathway in inefficient tumor immunogenicity of primary AML cells has to be further investigated, in particular using transfection experiments of CD80/B7-1-deficient AML cell lines. From our in vitro data we conclude that B7 molecules play an important role in the alloimmune surveillance of AML as suggested by the high B7 molecule dependency of IL-2 secretion. Nonetheless, the contribution of B7 molecules to alloimmune T cell proliferation against primary AML cells in human and the way to improve it--regulation via CD40 in particular--differ from B cell malignancies and murine models, suggesting the requirement for specific strategies in the development of antitumor immunity.

Human antibodies against the polymorphic epithelial mucin in ovarian cancer patients recognise a novel sequence in the tandem repeat region

The humoral immune response to the polymorphic epithelial mucin (PEM) was studied by characterising the reactivity of human antibodies generated by EBV-immortalised B-cells from tumour-draining lymph nodes of ovarian cancer patients. All the human antibodies, selected in ELISA for their reactivity to the protein tandem core repeat sequence, reacted with PEM-expressing tumour cells. Aberrant glycosylation of the peptide core of the PEM molecule in cancer cells leads to the exposure of peptide epitopes that can be considered tumour specific. The epitope mapping of six human antibodies revealed that only one of them contained the PDTR sequence, shown to be the immunodominant epitope in the mouse. Four of the six human antibodies recognised a novel common immunogenic sequence (APPAH) in the tandem repeats. The binding of these human antibodies did not appear to be modulated by the length of the carbohydrate side chains, as shown by O-glycosylation inhibition studies. These results indicate that distinct sequences within the tandem repeat of PEM are target for a humoral immune response in humans. The presence of antibodies directed against different epitopes within the same antigenic region may modulate the antigen presentation process and the ongoing immune response. This data may help in clarifying the mechanisms of the immune response to PEM in cancer patients for the development of PEM-based immunotherapy.

Immunotherapy III: Combinatorial molecular immunotherapy--a synthesis and suggestions

Animal models have clearly shown that tumor cells may be amenable to molecular manipulation which can result in immune activation and rejection of unmodified cells (Chapters 4 and 5). The challenge now is to design clinical trials which have a realistic chance of success, (although the definition of 'success' is itself an important issue [see Chapter 9]. How should such a strategy be formulated? A review of the previous fifteen years since the first (immune) gene transfer studies were reported, encompasses a great wealth of data. Unfortunately, far from crystallising a set of unifying principles, these diverse reports shroud us in a fog of uncertainty as to how best to proceed. However, if this technology is to have practical, widespread application in the treatment of cancer patients, it is necessary to identify certain critical immunological goals which any protocols should achieve. Clear elucidation of these goals, by unifying the huge amount of disparate experimental data, must eventually be accomplished. In this chapter, we have reviewed the literature covering the era of molecular immunotherapy. We propose four general goals around which widely applicable clinical protocols, not necessarily dependent upon tumour type or experimental bias, might be based and suggest how they may be achieved in the context of gene transfer.

Dendritic cells pulsed with RNA are potent antigen-presenting cells in vitro and in vivo

Immunization with defined tumor antigens is currently limited to a small number of cancers where candidates for tumor rejection antigens have been identified. In this study we investigated whether pulsing dendritic cells (DC) with tumor-derived RNA is an effective way to induce CTL and tumor immunity. DC pulsed with in vitro synthesized chicken ovalbumin (OVA) RNA were more effective than OVA peptide-pulsed DC in stimulating primary, OVA-specific CTL responses in vitro. DC pulsed with unfractionated RNA (total or polyA+) from OVA-expressing tumor cells were as effective as DC pulsed with OVA peptide at stimulating CTL responses. Induction of OVA-specific CTL was abrogated when polyA+ RNA from OVA-expressing cells was treated with an OVA-specific antisense oligodeoxynucleotide and RNase H, showing that sensitization of DC was indeed mediated by OVA RNA. Mice vaccinated with DC pulsed with RNA from OVA-expressing tumor cells were protected against a challenge with OVA-expressing tumor cells. In the poorly immunogenic, highly metastatic, B16/F10.9 tumor model a dramatic reduction in lung metastases was observed in mice vaccinated with DC pulsed with tumor-derived RNA (total or polyA+, but not polyA- RNA). The finding that RNA transcribed in vitro from cDNA cloned in a bacterial plasmid was highly effective in sensitizing DC shows that amplification of the antigenic content from a small number of tumor cells is feasible, thus expanding the potential use of RNA-pulsed DC-based vaccines for patients bearing very small, possibly microscopic, tumors.

Therapy of murine tumors with p53 wild-type and mutant sequence peptide-based vaccines

The BALB/c Meth A sarcoma carries a p53 missense mutation at codon 234, which occurs in a peptide, termed 234CM, capable of being presented to cytotoxic T lymphocytes (CTL) by H-2Kd molecules (Noguchi, Y., E.C. Richards, Y.-T. Chen, and L.J. Old. 1994. Proc. Natl. Acad. Sci. USA. 91:3171-3175). Immunization of BALB/c mice with bone marrow-derived dendritic cells (DC), generated in the presence of granulocyte macrophage colony-stimulating factor and interleukin 4, and prepulsed with the Meth A p53 mutant peptide, induced CTL that specifically recognized peptide-pulsed P815 cells, as well as Meth A cells naturally expressing this epitope. Immunization with this vaccine also protected naive mice from a subsequent tumor challenge, and it inhibited tumor growth in mice bearing day 7 subcutaneous Meth A tumors. We additionally determined that immunization of BALB/c mice with DC pulsed with the p53 peptide containing the wild-type residue at position 234, 234CW, induced peptide-specific CTL that reacted against several methylcholanthrene-induced BALB/c sarcomas, including CMS4 sarcoma, and rejection of CMS4 sarcoma in vaccination and therapy (day 7) protocols. These results support the efficacy of DC-based, p53-derived peptide vaccines for the immunotherapy of cancer. The translational potential of this strategy is enhanced by previous reports showing that DC can readily be generated from human peripheral blood lymphocytes.

Analysis of TCR usage in human tumors: a new tool for assessing tumor-specific immune responses

Tumor-infiltrating lymphocytes (TILs), through displaying a T-cell receptor (TCR) repertoire as heterogeneous as that of normal peripheral blood T cells, show overexpression of TCR variable-gene segments that include clonally expanded TCR sequences. Here, Marialuisa Sensi and Giorgio Parmiani analyze the available information on TCR usage by T cells present in the infiltrate of histologically different tumors and suggest that the analysis of TCR sequences represents a powerful new tool to assess the in vivo immune response to growing tumors. Ultimately, this strategy may lead to the identification and manipulation of T-cell populations endowed with antitumor reactivity.

Dendritic cells generated from peripheral blood transfected with human tyrosinase induce specific T cell activation

Peptides of melanosomal proteins have recently been shown to be recognized in an HLA-restricted mode by specific cytolytic T lymphocytes in melanoma patients. Dendritic antigen-presenting cells (DC) are considered to be the most effective stimulators of T cell responses, and the use of these cells has therefore been proposed to generate therapeutic responses to tumor antigens in cancer patients. We, therefore, generated DC from peripheral blood of normal donors in the presence of granulocyte/macrophage colony-stimulating factor and interleukin-4. Flow cytometric analysis of the cells during a 2-week culture revealed a loss of CD14 and CD34 expression, a concomittent increase of CD1a, CD11a,b and c, CD44, CD45, CD54, HLA-class I and II, and intermediate levels of CD26, CD80 and CD86. Cultured DC stimulated proliferation of allogeneic T cells and induced a marked, up to 20-fold, stimulation of T cell proliferation after pulsing with tetanus toxoid. To achieve independence of already-identified antigenic peptides presented in HLA class I-restricted fashion, which limits the general applicability of such peptides for vaccination of melanoma patients, we tested whether DC are transfectable with eukaryotic expression plasmids. DC transfected with two reporter genes (CAT, beta-galactosidase) using a liposome-based transfection technique, exhibited only low levels of enzymatically active proteins, but were able to degrade rapidly intracellular proteins and to process peptides efficiently. Chloramphenicol acetyltransferase as well as tyrosinase mRNA were detectable after transfection by reverse-transcriptase-polymerase chain reaction, and enzyme activities became measurable. Furthermore, DC transfected with the tyrosinase gene were able to induce specific T cell activation in vitro, indicating appropriate peptide processing and presentation in DC after transfection. These data suggest new approaches to future tumor vaccination strategies.

CD4+ Th0 cell clones, isolated from a metastatic lymph node of a melanoma patient, possess cytolytic function

In the present study T lymphocytes isolated from a metastatic lymph node (T-LNL) of a melanoma patient have been cloned. In the attempt to verify whether T-LNL may acquire in vitro functional activities in the absence of tumour-associated antigens, they were cloned utilizing allogenic lymphocytes as feeder cells. Nineteen clones generated from T-LNL proved to be CD4+ and, among these, five were able to kill autologous and allogeneic human melanoma cells in HLA-class-II-restricted way. On the basis of their cytokine production, these CD4+ cytolytic T-LNL clones were shown to belong to the Th0 subset and three of them expressed the V beta 17 chain of the T cell receptor. These results suggest the presence of melanoma-specific but functionally inactive lymphocytes with T cell receptor oligoclonality in the lymph node environment. These specific T cells may acquire in vitro the capacity to kill autologous and allogeneic tumours without any induction by autologous melanoma cells.

Mouse embryo fibroblasts transformed by activated ras or dominant-negative p53 express cross-reactive tumor rejection antigens

To study the immune response against oncogene-transformed tumors, C3H/HcN mouse embryo fibroblasts (MEF) were transfected with an activated allele of the H-ras proto-oncogene VaII2 and a dominant-negative allele of the murine p53 tumor suppressor gene VaII35. Transformed cell lines were derived and found to be tumorigenic in syngeneic mice. Immunization with irradiated p53 + ras-transformed MEF, but not primary MEF or unrelated syngeneic cells, protected mice from subsequent challenge with live tumor cells. The role of different immune cell subsets in the effector phase of anti-tumor immunity induced by immunization with p53 + ras-transformed MEF was investigated by in vivo antibody depletion experiments. Immunized mice depleted of CD8+ T, NK or B cells were resistant, but depletion of CD4+ T cells rendered mice susceptible to tumorigenic challenge. In contrast to the tumor-specific immune responses mounted against most chemically or UV-induced tumors, a series of independently derived p53 + ras-transformed MEF were cross-reactive in tumor rejection assays. In addition, immunization with C3H-derived L-929 cell lines expressing single gene products H-ras or p53 did not protect mice against tumorigenic challenge with p53 + ras-transformed tumors. However, MEF transformed by expression of either H-ras or p53 were cross-protective in vivo. Our data suggest that the p53 + ras-transformed MEF share tumor rejection antigens which are also induced by single gene transformation of the parental primary cell but are not the products of oncogenic ras or p53 protein.

T-cell repertoires in healthy and diseased human tissues analysed by T-cell receptor beta-chain CDR3 size determination: evidence for oligoclonal expansions in tumours and inflammatory diseases

Many examples of oligoclonal T-cell expansion in infiltrated diseased tissues have been reported. However, it remains to be established whether such observations can be generalized and to what extent oligoclonal patterns obtained after in vitro culture of T-cell infiltrates reflect in vivo situations. Using new high resolution analysis which requires no in vitro cellular expansion, we detected such oligoclonal T-cell expansions in 7/7 melanoma tumour biopsies, 3/3 biopsies of inflammatory skin during acute graft versus host disease (aGVHD) after allogeneic bone marrow transplantation (alloBMT) and 7/7 synovial membranes from patients with rheumatoid arthritis. Thus, oligoclonal T-cell expansions are readily observed when a sufficiently sensitive detection method is used, suggesting that similar expansions are the rule among T-cell infiltrates in different diseases. This observation and the monitoring of the in vivo evolution of such expansion during the course of the disease and during in vitro culture should have important clinical implications.

Autoimmune mechanisms in the pathogenesis of paraneoplastic nervous system disease

There is compelling circumstantial evidence that humoral autoimmune response may be involved in the generation of paraneoplastic neurologic syndromes (PNS). However, still it is unproven whether the autoantibody is pathogenic or represents an epiphenomenon to the actual disease process. Paraneoplastic antibodies have been identified in patients with PNS which react with similar antigenic epitopes in tumor and neurons. However, the antigens identified by the paraneoplastic antibodies are primarily intracellular in location, questioning the pathogenetic role of the antibody. The molecular events of antigen processing and presentation, T-cell receptor restriction, polyclonal B-cell proliferation, cellular immunity, and the role of cytokines in mediation of neuronal injury must be further defined in order to elucidate the role of autoimmunity in the pathogenesis of these disorders.

Identification of a gene encoding a melanoma tumor antigen recognized by HLA-A31-restricted tumor-infiltrating lymphocytes

The availability of antitumor cytotoxic T lymphocytes which can be generated from either peripheral blood lymphocytes after stimulation in vitro or tumor infiltrating lymphocytes (TIL) has made it possible to identify a number of melanoma antigens presented by major histocompatibility complex class I molecules. The present and previous studies indicated that TIL586 recognized an antigen expressed on most melanoma and normal melanocytes in the context of the HLA-A31 molecule. We report here the cloning of a cDNA that directs the expression of the shared melanoma antigen recognized by this TIL. The DNA sequence analysis revealed that the cDNA was almost identical to the gene encoding tyrosinase-related protein 1 or glycoprotein gp75 which was originally identified by serum antibodies in a patient with melanoma. The gene was found to be expressed only in melanoma, normal melanocyte cell lines, and retina, but not in other normal tissues tested. The gp75 antigen presented by HLA-A31 may therefore constitute a useful immune target for specific treatment of patients with melanoma, since both antibody- and T cell-mediated immune responses can be generated against this antigen.

Promotion of macrophage-stimulated autoreactive T cell proliferation by interleukin-10: counteraction of macrophage suppressor activity during tumor growth

CD4+ autoreactive T cells are a major cell population in regulating immune responses to altered autologous neoplastic cells. Normal autoreactive T cells recognize major histocompatibility complex (MHC) class II molecules in association with self-peptides on antigen-presenting cells, such as macrophages (M phi). Tumor-bearing hosts (TBH) have decreased autoreactivity partly because tumors increase M phi secretion of suppressor molecules like prostaglandin E2 (PGE2) and decrease M phi MHC class II expression. Because interleukin (IL)-10, a cytokine produced by T cells, M phi, and tumor cells, inhibits production of most M phi suppressor molecules, we determined if IL-10 could reverse tumor-induced murine splenic M phi-mediated suppression of autoreactive T cell proliferation. Tumor growth enhanced activated M phi production of PGE2, nitric oxide, and tumor necrosis factor-alpha (TNF-alpha). IL-10 strongly reduced or inhibited M phi production of these molecules. When added to pure normal host (NH) CD4+ T cells, NH syngeneic splenic M phi stimulated autoreactive T cell proliferation more than did TBH splenic M phi. Exogenous IL-10 or M phi preincubation with IL-10 restored TBH M phi-stimulated autoreactivity to normal levels. IL-10 treatment had little or no effect on NH M phi-stimulated autoreactivity. IL-10 inhibited TBH M phi secretion of suppressor molecules in T cell proliferation assays because supernatants from IL-10-pretreated TBH M phi-syngeneic NH T cell cultures had decreased levels of suppressor molecules. When endogenous IL-10 activity was neutralized with anti-IL-10 monoclonal antibody, autoreactive T cell proliferation stimulated by NH or TBH M phi was slightly, but significantly decreased. Although IL-10 is known to inhibit M phi foreign antigen-presenting cell-dependent T cell proliferation, this study shows that IL-10 restores autoreactive T cell functions during tumor growth by counteracting M phi production of inhibitory molecules. These data suggest that IL-10 up-regulates anti-cancer autoreactive T cell responses by down-regulating suppressor M phi activity.

Lymphocytic infiltration and destruction of parathyroid adenomas: a possible tumour-specific autoimmune reaction in two cases of primary hyperparathyroidism

Two cases of primary hyperparathyroidism with underlying parathyroid adenomas were found to be associated with lymphocytic infiltration and destruction of the neoplastic tissue. There was no inflammatory infiltrate in the adjacent rim of the remnant of parathyroid gland or in the other tumour-free glands. The lymphoid cell population within the tumours was composed of both infiltrating T-cells and compact nodule-forming B-cells. In one of the tumours there was considerable fibrosis and atrophy of the adenomatous tissue. The histological picture was consistent with an autoimmune process directed against the adenomas, indicating that this reaction had, in part, been successful in reducing the abnormal cell population.

Frequency of cytotoxic T lymphocyte precursors (CTLp) interacting with autologous tumor via the T-cell receptor: limiting dilution analysis of specific CTLp in peripheral blood and tumor-invaded lymph nodes of melanoma patients

The frequencies of cytotoxic T-lymphocyte precursors (CTLp) that lyse autologous tumor by a T-cell receptor (TCR)-dependent mechanism (specific CTLp) were evaluated by limiting dilution analysis (LDA) using lymphocytes from peripheral blood (PBL) and from surgically resected, tumor-invaded lymph nodes (LNL) in 9 melanoma patients. The frequency of specific CTLp was determined in PBLs and/or LNIs of all patients by a modified LDA assay, enabling us to measure lytic activity on the autologous tumor that could be significantly inhibited by an anti-CD3 monoclonal antibody (MAb). This assay allowed us to detect frequencies of specific CTLp ranging from 1/720 to 1/32,037 in peripheral blood and from 1/328 to 1/22,061 in tumor-invaded lymph nodes. These frequencies indicated that lymphoid populations from PBLs or LNLs of melanoma patients may contain as low as 30 to as much as 3,000 specific CTLp/10(6) lymphocytes. In addition, comparison of wells containing specific CTLp with those showing no inhibition by anti-CD3 MAb indicated that specific CTLp represent between 3 and 88% of all precursors with lytic activity on the tumor. In 6 of 9 patients, no marked differences between PBLs and LNIs in specific CTLp frequencies were found. A 10-fold increase of specific CTLp, in comparison to PBL and LNL, was found only in lymphocytes isolated from a subcutaneous metastasis of one patient. Our results indicate that CTLp interacting with autologous tumor by a TCR-dependent mechanism exist in PBL and LNL of most melanoma patients, although a wide variation in their absolute number is evident among different patients.

Non-fastidious, melanoma-specific CD8+ cytotoxic T lymphocytes from choroidal melanoma patients

To characterize the anti-melanoma reactivity of CD8+ cytotoxic T lymphocytes (CTL) from choroidal melanoma patients, CTL clones were isolated from the peripheral blood of three patients after mixed lymphocyte/tumor cell culture (MLTC). Clones were derived from lymphocytes stimulated by allogeneic (OCM-1, A24, A28) or autologous (OCM-3, A1, A30) melanoma cells. Their reactivity against a panel of HLA-typed melanoma and nonmelanoma cells was assessed, to determine whether a single CTL clone could recognize and lyse a variety of allogeneic melanoma cell lines. While proportionately more clones derived from autologous MLTC were melanoma-specific than allogeneic MLTC (42% versus 14%), melanoma-specific CTL were recovered from both. Notably, a novel melanoma specificity was identified. These CTL clones were termed non-fastidious because they were capable of lysing melanoma cells with which they had no HLA class I alleles in common. Nonetheless, lysis was mediated by the HLA class I molecule. Since lysis was specific for melanoma cells, these CTL appeared to recognize a shared melanoma peptide(s). Because of their prevalence, we propose that non-fastidious CTL are integral to human anti-melanoma T cell immunity. This reinforces clinical findings that allogeneic melanomas can substitute for autologous tumors in active specific immunotherapy. By circumventing the need for autologous melanoma, it is possible to treat patients after removal of the primary choroidal melanoma in an attempt to prevent metastasis.