New tumor antigens recognized by T cells

BAP31, a promising target for the immunotherapy of malignant melanomas

PURPOSE

Malignant melanoma's (MM) incidence is rising faster than that of any other cancer in the US and the overall survival at 5 years is less than 10%. B cell associated protein 31 (BAP31) is overexpressed in most MMs and might be a promising target for immunotherapy of this disease.

EXPERIMENTAL DESIGN

Firstly, we investigated the expression profiles of human BAP31 (hBAP31) and mouse BAP31 (mBAP31) in human and mouse normal tissues, respectively. The expression level of hBAP31 in human MMs and mBAP31 in B16 melanoma cells was also analyzed. Then we constructed novel mBAP31 DNA vaccines and tested there ability to stimulate mBAP31-specific immune responses and antitumor immunity in B16 melanoma-bearing mice.

RESULTS

For the first time, we found that protein expression of hBAP31 were dramatically upregulated in human MMs when compared with human normal tissues. Predominant protein expression of mBAP31 was found in mouse B16 melanoma cells but not in mouse important organs. When mice were immunized with mBAP31 DNA vaccines, strong cellular response to mBAP31 was observed in the vaccinated mice. CTLs isolated from immunized mice could effectively kill mBAP31-positive target mouse B16 melanoma tumor cells in vitro and vaccination with mBAP31 DNA vaccines had potent anti-tumor activity in therapeutic model using B16 melanoma cells.

CONCLUSIONS

These are the first data supporting a vaccine targeting BAP31 that is capable of inducing effective immunity against BAP31-expressing MMs and will be applicable to human MMs and hBAP31 DNA vaccine warrants investigation in human clinical trials.

Vaccines for cancer prevention: a practical and feasible approach to the cancer epidemic

Concerted efforts of tumor immunologists over more than two decades contributed numerous well-defined tumor antigens, many of which were promptly developed into cancer vaccines and tested in animal models and in clinical trials. Encouraging results from animal models were seldom recapitulated in clinical trials. The impediment to greater success of these vaccines has been their exclusive use for cancer therapy. What clinical trials primarily revealed were the numerous ways in which cancer and/or standard treatments for cancer could suppress the patient's immune system, making it very difficult to elicit effective immunity with therapeutic vaccines. In contrast, there is an extensive database of information from experiments in appropriate animal models showing that prophylactic vaccination is highly effective and safe. There are also studies that show that healthy people have immune responses against antigens expressed on tumors, some generated in response to viral infections and others in response to various nonmalignant acute inflammatory events. These immune responses do not appear to be dangerous and do not cause autoimmunity. Epidemiology studies have shown that these immune responses may reduce cancer risk significantly. Vaccines based on tumor antigens that are expressed differentially between tumors and normal cells and can stimulate immunity, and for which safety and efficacy have been proved in animal models and to the extent possible in therapeutic clinical trials, should be considered prime candidates for prophylactic cancer vaccines.

From genes to drugs: targeted strategies for melanoma

The past decade has revealed that melanoma is comprised of multiple subclasses that can be categorized on the basis of key features, including the clinical stage of disease, the oncogenic molecular 'drivers', the anatomical location or the behaviour of the primary lesion and the expression of specific biomarkers. Although exercises in subclassification are not new in oncology, progress in this area has produced both conceptual and clinical breakthroughs, which, for melanoma, are unprecedented in the modern history of the disease. This Review focuses on these recent striking advances in the strategy of molecularly targeted approaches to the therapy of melanoma in humans.

Cancer vaccines: Where are we going?

Abstract The discovery that the immune system can distinguish molecular targets on cancer cells has led to efforts to develop cancer immunotherapeutics that can improve the recognition and effective elimination of tumor cells. Several types of tumor antigens are recognized by T lymphocytes, which are classified according to patterns of gene expression or protein distribution. Of particular interest is the group of molecules known as cancer-germline or cancer-testis antigens. As the relationship between the immune system and cancer has become clearer, so too have the challenges in designing effective cancer immunotherapeutics: (i) antigens need to be specifically selected based on ideal characteristics, such as tissue distribution that is restricted to tumors; (ii) selected antigens need to be combined with adjuvant agents that enhance their immunogenicity and yield robust responses; (iii) vaccination should be timed to pre-empt the development of regulatory suppressive immune mechanisms; and (iv) if suppressive regulatory mechanisms do arise, specific antagonists may be needed to enhance pro-immune outcomes. These challenges are shaping current and future research in this area.

The E75 HER2/neu peptide vaccine

E75 (HER2/neu 369-377) is an immunogenic peptide from the HER2/neu protein which is overexpressed in many breast cancer patients. A large amount of preclinical work and a small number of Phase I trials have been completed evaluating the vaccine potential of the E75 peptide mixed with an immunoadjuvant. Our group has performed two concurrent E75 + GM-CSF Phase II trials in node-positive and node-negative disease-free breast cancer patients. These trials, totaling 186 patients, were designed to assess the ability of the E75 vaccine to prevent disease recurrence in these high risk patients. In this review article, we discuss the safety of the vaccine, the immunologic response to the peptide, and most importantly, the potential clinical benefit of the vaccine. The recurrence rate, mortality associated with recurrence, and the distribution of recurrences are presented and discussed. Additionally, the lessons learned from these trials to include optimal dosing and the need for booster inoculations are addressed. We also present data exploring possible explanations and mechanisms behind the potential clinical utility of this simple single epitope vaccine. Finally, we present some of the future directions for our Cancer Vaccine Development Program assessing multi-epitope peptide vaccines and combination immunotherapies.

T cell therapies following hematopoietic stem cell transplantation: surely there must be a better way than DLI?

Advances in the past few years have significantly improved adoptive immunotherapy strategies available following autologous and allogeneic hematopoietic stem cell transplantation (HSCT). Minimal residual disease, relapsed disease and viral infections remain a significant cause of mortality in patients undergoing HSCT. Novel therapies are critically needed to overcome these management dilemmas, while sparing the graft-versus-tumor effect and avoiding graft-versus-host disease. This review focuses on the T-cell strategies currently available to allay disease while minimizing toxicities in patients who have undergone HSCT.

Identification of NY-ESO-1, MAGE-1, and MAGE-3 in head and neck squamous cell carcinoma

BACKGROUND

Certain tumor antigens have been identified that stimulate an immune response, thus making them targets for immunotherapy. NY-ESO-1, MAGE-1, and MAGE-3 are such antigens. This study was undertaken to determine their presence or absence in head and neck squamous cell cancers and to correlate this with patient characteristics.

METHODS

Reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry (IH) were used to identify NY-ESO-1, MAGE-1, and MAGE-3 in surgical specimens. Patient data (previous treatment, gender, age, primary site, metastasis, tumor grade, tumor stage, smoking history, and alcohol history) were collected by chart review and examined for correlation with presence or absence of antigen.

RESULTS

Three tumors were found to be positive for NY-ESO-1 by RT-PCR. All of these tumors were also positive for MAGE-1 and MAGE-3. IH was only positive for NY-ESO-1 in one patient. Eighteen of the 45 tumors (40%) were positive for MAGE-1 by RT-PCR. By IH, only six tumors were positive for MAGE-1. Five (83.3%) of those that were positive by IH were positive by RT-PCR. Twenty of the 45 tumors (44.4%) were positive for MAGE-3 by RT-PCR. By IH, 12 tumors were positive for MAGE-3. Nine (75%) of those positive by IH were also positive by RT-PCR. Overall, of the 45 tumors, 27 (60%) were positive by RT-PCR for at least one of the antigens. None of the patient characteristics correlated with the presence or absence of antigen.

CONCLUSIONS

There is high expression of MAGE-1 and MAGE-3 antigens in head and neck squamous cell carcinomas, whereas NY-ESO-1 is not significantly expressed. IH correlates but is not as sensitive as RT-PCR for detection of these antigens. There is no correlation between antigen expression and patient data. On the basis of the high levels of MAGE-1 and MAGE-3 expression, use of these antigens may serve as a potential approach to immunotherapy for squamous cell carcinoma from head and neck sources.

Immunotherapy of Hematologic Malignancy

Over the past few years, improved understanding of the molecular basis of interactions between antigen presenting cells and effector cells and advances in informatics have both led to the identification of many candidate antigens that are targets for immunotherapy. However, while immunotherapy has successfully eradicated relapsed hematologic malignancy after allogeneic transplant as well as virally induced tumors, limitations have been identified in extending immunotherapy to a wider range of hematologic malignancies. This review provides an overview of three immunotherapy strategies and how they may be improved.

In Section I, Dr. Stevenson reviews the clinical experience with genetic vaccines delivered through naked DNA alone or viral vectors, which are showing promise in clinical trials in lymphoma and myeloma patients. She describes efforts to manipulate constructs genetically to enhance immunogenicity and to add additional elements to generate a more sustained immune response.

In Section II, Dr. Molldrem describes clinical experience with peptide vaccines, with a particular focus on myeloid tissue-restricted proteins as GVL target antigens in CML and AML. Proteinase 3 and other azurophil granule proteins may be particularly good targets for both autologous and allogeneic T-cell responses. The potency of peptide vaccines may potentially be increased by genetically modifying peptides to enhance T-cell receptor affinity.

Finally, in Section III, Dr. Heslop reviews clinical experience with adoptive immunotherapy with T cells. Transferred T cells have clinical benefit in treating relapsed malignancy post transplant, and Epstein-Barr virus associated tumors. However, T cells have been less successful in treating other hematologic malignancies due to inadequate persistence or expansion of adoptively transferred cells and the presence of tumor evasion mechanisms. An improved understanding of the interactions of antigen presenting cells with T cells should optimize efforts to manufacture effector T cells, while manipulation of lymphocyte homeostasis in vivo and development of gene therapy approaches may enhance the persistence and function of adoptively transferred T cells.

Identification and characterization of 9D7, a novel human protein overexpressed in renal cell carcinoma

With the objective of discovering novel tumor-associated antigens of the cancer/testis type, we compared the transcriptional profiles of renal cell carcinoma (RCC) and non-tumorous kidney and further screened for genes expressed in RCC and testis, but not other normal tissues. In a first step, a representational difference analysis library consisting of approximately 1,900 RCC cDNA clones was generated. Clones were then spotted onto filters and hybridized with cDNA probes derived from a testis-specific cDNA library, a pool of RCCs and a pool of 10 healthy normal tissues, respectively. Based on strong hybridization signals with both RCC and testis, but not normal tissue probes, 185 clones were sequenced and annotated. After EST-database comparison, 35 clones were selected for experimental analysis, including conventional and quantitative RT-PCR as well as Northern blotting. Clone 9D7 showed strong mRNA expression in RCC as well as in several other major tumor types. In normal tissues there was little or no mRNA expression with the exception of heart. 9D7 was cloned to full-size and found to represent a novel human gene containing 5 exons residing on chromosome 14. Alternative splicing within exon 1 generates 2 open-reading-frames consisting of 717 or 435 bp corresponding to predicted proteins of 239 or 145 amino acids. 9D7 shows high homology (227/239 amino acids or 95% identity) to a growth factor-inducible gene of Rattus norvegicus involved in apoptosis. In situ hybridization as well as immunohistochemical analysis using 9D7-specific antisera confirmed overexpression of 9D7 in RCCs as compared to normal kidney tissue.

An oral DNA vaccine against human carcinoembryonic antigen (CEA) prevents growth and dissemination of Lewis lung carcinoma in CEA transgenic mice

A DNA vaccine encoding human carcinoembryonic antigen (CEA) broke peripheral T-cell tolerance toward this tumor self-antigen expressed by Lewis lung carcinoma stably transduced with CEA in C57BL/6J mice transgenic for CEA. This vaccine, delivered by oral gavage with an attenuated strain of Salmonella typhimurium (SL7207), and boosted with an antibody-IL2 fusion protein, induced tumor-protective immunity mediated by MHC class I antigen-restricted CD8(+) T cells, resulting in eradication of subcutaneous tumors in 100% of mice and prevention of experimental pulmonary metastases in 75% of experimental animals. Both CTL and antigen-presenting dendritic cells were activated as indicated by a decisive increase in their respective activation markers CD2, CD25, CD28 as well as CD48 and CD80. The antitumor effects of this CEA-based DNA vaccine obtained in prophylactic settings, suggest that this approach could lead to the rational design of effective treatment modalities for human lung cancer.

Therapeutic vaccines against melanoma and colorectal cancer

Our overall strategy is to develop multivalent recombinant vaccines capable of eliciting broad immune responses in patients with malignant melanoma or colorectal cancer. We report herein results from initial studies conducted in cancer patients to evaluate the effect of intratumoral administration of recombinant canarypox viruses carrying cytokine genes. Our current focus is on the induction of tumor-specific T-cell responses using a prime/boost immunization schedule with a unique vector system derived from the canary pox virus called ALVAC, in which we incorporate genes encoding Tumor Associated Antigens (TAAs) of interest. Clinical studies in colorectal cancer evaluating an ALVAC CEA candidate vaccine have shown that this approach is safe and can induce tumor-specific T cell responses. Additional clinical studies evaluating candidate vaccines against melanoma and colorectal cancer, targeting either the gp100, Mage 1, Mage 3 or p53 molecules are ongoing.

Synthesis and antigenic properties of reduced peptide bond analogues of an immunodominant epitope of the melanoma MART-1 protein

Backbone modifications have been introduced into the melanoma derived peptide MART-1(27-35) to increase its binding to class I major histocompatibility complex HLA-A2 molecule, and ultimately to enhance its immunogenicity. Each analogue was obtained by replacing one peptide bond at a time in the natural epitope by the aminomethylene (CH2-NH) surrogate. All analogues displayed an increased resistance to proteolysis. Interestingly, the comparative results showed that five analogues bound more efficiently to HLA-A2 than the parent peptide. On the other hand, two pseudopeptide/HLA-A2 complexes were recognized by one melanoma-specific T cell clone. Close examination of the impact of such modifications at the molecular level provides useful supports for the rational design of stable compounds with applications in anti-tumour specific immunotherapy and in vaccine development.

Cancer vaccines

Cancer vaccines have been extensively tested in animal models, and in humans. Initial studies focused on first generation vaccines based on whole cell preparations or tumor lysates derived from autologous or allogeneic tumors. Clinical studies conducted with such candidate vaccines contributed to establish the feasibility of immunizing cancer patients against their own tumors. Significant clinical benefits were observed, both in terms of long term survival and recurrence rate, in some of these trials. More recently, however, cancer vaccines targeting well-characterized tumor-associated antigens, i.e. molecules selectively or preferentially expressed by cancer cells but not by normal cells, have been designed and tested in humans. Results obtained as of today with these second-generation vaccines suggest that they are safe and that they can elicit humoral and cellular responses against tumor-specific antigens, without inducing unacceptable clinical signs of autoimmunity. Advances in tumor biology and tumor immunity have helped to better understand the mechanisms displayed by a number of tumors to escape host immunity. This bulk of new knowledge will be used to design future cancer vaccines, which will likely target multiple TAAs, presented by different antigen presentation platforms, in association with synthetic adjuvants and/or immunostimulatory cytokines. Lastly, specific tools allowing to assess in a qualitative and quantitative manner immune responses are critically needed in order to establish correlates between clinical and immune responses in patients receiving experimental vaccines.

Recombinant viruses as a tool for therapeutic vaccination against human cancers

Viral vectors can be used to express a variety of genes in vivo, that encode tumor associated antigens, cytokines, or accessory molecules. For vaccination purposes, the ideal viral vector should be safe and enable efficient presentation of expressed antigens to the immune system. It should also exhibit low intrinsic immunogenicity to allow for its re-administration in order to boost relevant specific immune responses. Furthermore, the vector system must meet criteria that enable its industrialization. The characteristics of the most promising viral vectors, including retroviruses, poxviruses, adenoviruses, adeno-associated viruses, herpes simplex viruses, and alphaviruses, will be reviewed in this communication. Such recombinant viruses have been successfully used in animal models as therapeutic cancer vaccines. Based on these encouraging results, a series of clinical studies, reviewed herein, have been undertaken. Human clinical trials, have as of today, allowed investigators to establish that recombinant viruses can be safely used in cancer patients, and that such recombinants can break immune tolerance against tumor-associated antigens. These promising results are now leading to improved immunization protocols associating recombinant viruses with alternate antigen-presentation platforms (prime-boost regimens), in order to elicit broad tumor-specific immune responses (humoral and cellular) against multiple target antigens.

Advances in specific immunotherapy of malignant melanoma

Management of malignant melanoma continues to present a challenge to dermatologists, particularly in advanced cases. In light of the steady increase in the worldwide incidence and mortality rates for melanoma, better understanding of the immune mechanisms regulating melanoma progression and interaction with the host's immune system seems eminently important. New studies on the role of immune mechanisms in the pathogenesis and clinical course of melanoma have recently been published. We review the immune mechanisms involved in tumor progression and ways in which these mechanisms may be applied toward immunotherapeutic management of malignant melanoma.

LEARNING OBJECTIVE

After the completion of this learning activity, participants should be familiar with (1) the immune mechanisms involved in host-tumor interaction and tumor rejection, (2) factors allowing the escape of melanoma cells from immune recognition, and (3) the current rationale for the different types of specific immunotherapy in melanoma. Better understanding of basic mechanisms in tumor immunology should raise awareness of future immunotherapeutic approaches in patients with melanoma, particularly in those who are at high risk of recurrence or who present with advanced disease.

Reduction in serum IL-6 after vacination of breast cancer patients with tumour-associated antigens is related to estrogen receptor status

Elevated serum IL-6 concentrations have been associated with poor prognosis in a variety of cancers, and decreases in serum IL-6 concentrations have been reported after chemotherapy. We have demonstrated that serum IL-6 concentrations are elevated in breast cancer patients [normal women 0.7 +/- 2.5 pg/ml (n=36), breast cancer patients 38.3 +/- 138.7 pg/ml (n = 111)]. After vaccination of breast cancer patients with a combination of tumour-associated antigens and biological adjuvants (IL-2 and GM-CSF), the concentration of IL-6 decreased significantly (P<0.05) to 8.1 +/- 14.6 pg/ml (n=85). Other studies have shown that oestrogen suppresses IL-6 production in oestrogen receptor positive breast cancer cells. We have demonstrated that the decrease in IL-6 associated with vaccination is related to the oestrogen receptor status of the tumours from breast cancer patients, as a decrease in IL-6 from 124.0 +/- 267.5 pg/ml (n=26) to 6.2 +/- 11.0 pg/ml (n=34) only occurs in patients with oestrogen receptor negative tumours. The IL-6 concentration in breast cancer patients with oestrogen receptor positive tumours remained unchanged (9.5 pg/ml before vaccination, and 9.3 pg/ml after vaccination). These results suggest that postmenopausal women with oestrogen receptor negative breast cancers, who do not respond well to either hormonal therapy with tamoxifen or adjuvant chemotherapy, may have a significant response to vaccination with autologous tumour-associated antigens.

Oligosaccharide trimming plays a role in the endoplasmic reticulum-associated degradation of tyrosinase

The effect of glucosidase and mannosidase inhibitors on the ER-associated degradation of tyrosinase was assessed in transiently transfected COS-7 cells. We found that the glucosidase inhibitors castanospermine and deoxynojirimycin had very little effect on tyrosinase degradation, whereas the mannosidase inhibitors deoxymannojirimycin and kifunensine significantly delayed the rate of tyrosinase degradation as measured by pulse-chase analysis. In addition, we show that tyrosinase degradation is sensitive to the proteasome inhibitor lactacystin and that tyrosinase associates with endogenous calnexin in COS-7 cells. Our data support a model of tyrosinase degradation that involves mannose trimming, calnexin association, and the retrograde transport of tyrosinase from the ER to the cytosol for proteasomal degradation. The pathways of tyrosinase degradation have important ramifications with regard to the exact types of antigenic epitopes that are presented to the immune system.

The role of cytotoxic T-lymphocytes in the prevention and immune surveillance of tumors--lessons from normal and immunodeficient mice

The idea of immunological surveillance against cancer has existed for nearly 100 years but as no conclusive evidence has yet been published the importance of the cellular immune defense in the detection and removal of incipient or existing tumors is still a hotly debated subject. However, in order to select a relevant immunotherapeutic strategy in the treatment of cancer, a fundamental understanding of the basic immunologic conditions under which a tumor develops and exists is a prerequisite. Therefore, a murine model was set up that we hoped would enable us to confirm or reject the theory of immunological surveillance. A large panel of methylcholanthrene induced tumors was established in T-cell immunodeficient nude mice and congenic normal mice to study the influence of the immune system on developing tumors. As nude mice developed tumors fastest and with the highest incidence, we concluded that in this model the immune system constituted a 'tumor-suppressive factor' delaying and sometimes abrogating tumor growth, i.e. performing immune surveillance. Immunogenicity of the tumors was assessed by transplantation back to normal histocompatible mice. Tumors originating from the immunodeficient nude mice turned out to be far more immunogenic than tumors from normal mice, resulting in a high rejection rate. CD8+ cytotoxic T cells were found to be indispensable for this rejection, leading to the conclusion that the cytotoxic T cells perform immune selection in normal mice, eliminating immunogenic tumor cell variants in the incipient tumor. In this review, we discuss the difficulties facing immunotherapy when conclusions are drawn from the presented observations and hypotheses.

Interleukin-2-induced, melanoma-specific T cells recognize CAMEL, an unexpected translation product of LAGE-1

Melanoma-specific cytotoxic T lymphocytes (CTLs) were induced by in vitro stimulation of peripheral blood mononuclear cells of a melanoma patient with autologous IL-2-producing melanoma 518/IL2.14 cells. CTL clone 1/29 recognized, in addition to autologous melanoma cell lines, a panel of HLA-A*0201-expressing allogeneic melanoma cell lines but was not reactive with normal melanocytes. Here, we report the full molecular characterization of the target structure for CTL 1/29, which was identified by cDNA expression cloning. The recognized antigen was named CAMEL (CTL-recognized antigen on melanoma). The CAMEL cDNA turned out to be derived from the LAGE-1 gene, a recently described tumor antigen that is strongly homologous to NY-ESO-1. CAMEL, however, is not encoded by the putative open reading frame (ORF) of LAGE-1 but by an alternative frame starting from the second ATG of the mRNA. The first 11 amino acids of the CAMEL protein, MLMAQEALAFL, constitute the epitope of CTL 1/29. This epitope is also encoded by a similar alternative ORF in NY-ESO-1. In summary, CTL induction with IL-2-transfected melanoma cells has revealed a new tumor antigen that may serve as a target for immunotherapy.

A Non-AUG-Defined Alternative Open Reading Frame of the Intestinal Carboxyl Esterase mRNA Generates an Epitope Recognized by Renal Cell Carcinoma-Reactive Tumor-Infiltrating Lymphocytes In Situ

A number of Ags recognized by tumor-reactive T cells have been characterized, including nonmutated gene products and a variety of epitopes shown to arise from either mutated or alternatively processed transcripts. Here, we report that the screening of a cDNA library with an HLA-B7-restricted renal cell carcinoma-reactive T cell clone derived from tumor-infiltrating lymphocytes (TILs) that were clonally amplified in vivo (as assessed by TCRBV complementarity determining region-3 length distribution analysis) resulted in the isolation of a nonamer encoded by an alternative open reading frame (ORF) (a +1 frameshift) of the intestinal carboxyl esterase gene. This peptide binds HLA-B*0702-presenting molecules as assessed in an immunofluorescence-based peptide binding assay using transfected T2 cells. Constitutive expression of this alternative ORF protein was observed in all transformed HLA-B7+ renal cell lines that were recognized in cytotoxicity assays by the TILs. The intestinal carboxyl esterase gene is transcribed in renal cell carcinoma tumors as well as in normal liver, intestinal, or renal tissues. Mutation of the natural ATG translation initiation site did not alter recognition, indicating that frameshifting (i.e., slippage of the ribosome forward) and recoding are not involved. In addition, a point mutation of the three AUG codons that may be used as alternative translation initiation sites in the +1 ORF did not abolish recognition, whereas mutation of an upstream ACG codon did, indicating that the latter codon initiates the translation of the alternative ORF. These results further extend the types of Ags that can be recognized by tumor-reactive TILs in situ (i.e., leading to clonal T cell expansion).

A hsp70-2 Mutation Recognized by CTL on a Human Renal Cell Carcinoma

We performed T cell cloning experiments with a tumor-infiltrating lymphocyte subpopulation derived from a renal cell carcinoma tumor site (RCC-7) in which the TCR clonotypic repertoire had been analyzed in terms of TCRBV complementarity-determining region 3 size distribution. We report in this work the characterization of one of the five RCC-specific MHC class I-restricted CTL clones isolated in RCC-7. This TCRBV6J1S1 CTL recognized only the autologous RCC-7 tumor cell line in the context of HLA-A*0201, and the Ag is encoded by a mutated form of the hsp70-2 gene found in the tumor cells, but not in autologous PBLs nor in 47 other tumors. The identification of this gene was achieved by cotransfecting into COS cells a cDNA library of RCC-7 together with HLA-A*0201. Transfectants expressing the Ag were identified by their ability to stimulate TNF release by the CTL clone. The antigenic peptide is a decamer with a mutated residue at position 8. Half-maximal lysis was obtained with only 5 × 10−11 M of decapeptide in target sensitization assays compared with 5 × 10−8 M for the wild-type decapeptide. This difference in recognition was not related to difference in binding HLA-A*0201-presenting molecules, as assessed in an immunofluorescence-based peptide-binding assay using T2 cells. Constitutive hsp70 expression in various tumors suggests that this stress-induced protein may be recognized in situ by tumor-infiltrating lymphocytes. The finding in the tumor of a mutated form of the stress-induced hsp70-2 gene whose product is specifically recognized by TILs with high avidity is discussed in view of the present use of mycobacteria or heterologous heat-shock proteins as immunomodulators or as subunit vaccine candidates.

First comparative delineation of the T cell receptor repertoire in primary and multiple subsequent/coexisting metastatic melanoma sites

At present, very little is known about the types and heterogeneity of T cell responses and immunodominant epitopes of melanoma-associated antigens at coexisting sites of primary melanoma and metastatic lesions. To address this issue, we compared the T cell receptor (TCR) gene usage, complementary-determining region 3 diversity, and melanoma-associated antigens expression patterns of primary and metastatic melanoma specimens from three patients with partially homologous HLA class-1 types. Results obtained showed an overall predominance of a very limited number of TCRV regions with AV13 and BV14 being most frequently overexpressed. Sequencing of the dominating TCR transcripts confirmed the restricted usage of certain TCR specificities and, in two of the three patients, identified several identical TCR clonotypes at more than one metastatic site. Nevertheless, we failed to detect TCR transcripts that were common to all tumor deposits in a given patient and, within the majority of coexisting metastases, tumor-infiltrating lymphocytes preferentially used individual site-specifically expanded TCR beta-chain VJ segment combinations. This occurrence of individual responses simultaneously executed at and influenced in their specificity by the different sites of tumor growth, has important implications for the type of strategies chosen in the development of efficacious vaccines for patients with metastatic melanoma.

In vivo tumor transfection with superantigen plus cytokine genes induces tumor regression and prolongs survival in dogs with malignant melanoma

In vivo transfection of established tumors with immunostimulatory genes can elicit antitumor immunity. Therefore, we evaluated the safety and efficacy of intratumoral injections of a bacterial superantigen with a cytokine gene in dogs with malignant melanoma, a spontaneous and highly malignant canine tumor. 26 dogs with melanoma were treated with lipid-complexed plasmid DNA encoding staphylococcal enterotoxin B and either GM-CSF or IL-2. Dogs were evaluated for treatment-associated toxicity, tumor responses, immunologic responses, and survival times. The overall response rate (complete or partial remissions) for all 26 dogs was 46% (12 of 26), and was highest in patients with smaller tumors. Toxicity was minimal or absent in all dogs. Injected tumors developed marked infiltrates of CD4+ and CD8+ T cells and macrophages, and tumor regression was associated with development of high levels of antitumor cytotoxic T lymphocyte activity in peripheral blood lymphocytes. Survival times for animals with stage III melanomas treated by intratumoral gene therapy were prolonged significantly compared with animals treated with surgical tumor excision only. Thus, local tumor transfection with superantigen and cytokine genes was capable of inducing both local and systemic antitumor immunity in an outbred animal with a spontaneously developing malignant tumor.

Genetically modified bone marrow-derived dendritic cells expressing tumor-associated viral or "self" antigens induce antitumor immunity in vivo

The clinical application of synthetic tumor peptide-based vaccines is currently limited to patients with specified major histocompatibility complex (MHC) class I alleles. Such logistic limitations may be overcome using tumor gene-based approaches. Here we describe the effective generation of dendritic cells (DC) expressing tumor peptide-MHC complexes as a result of particle-mediated transfer of genes encoding tumor-associated antigens (TAA). Bone marrow-derived DC were transfected with plasmid DNA encoding the tumor-associated viral antigen E7 derived from human papilloma virus (HPV) 16. When applied as a vaccine, these genetically modified DC induced antigen-specific CD8+ cytotoxic T lymphocytes (CTL) in vivo and promoted the rejection of a subsequent, normally lethal challenge with an HPV 16-transformed tumor cell line. Of greatest interest, immunization of mice with syngeneic DC genetically modified to enhance their presentation of a constitutive "self" epitope derived from the tumor-suppressor gene product p53 caused a significant reduction in the in vivo growth of a chemically induced p53-positive sarcoma. These results suggest that cancer vaccines consisting of DC genetically modified to express TAA of viral or "self" origin effectively induce antitumor immunity in vivo.

A CASP-8 mutation recognized by cytolytic T lymphocytes on a human head and neck carcinoma

Of the antigens recognized on human tumors by autologous cytolytic T lymphocytes, all those defined thus far have been identified on melanoma or renal cell carcinoma. We report here the identification of an antigen recognized by autologous cytolytic T lymphocytes on a human squamous cell carcinoma of the oral cavity. The antigen is encoded by a mutated form of the CASP-8 gene. This gene, also named FLICE or MACH, codes for protease caspase-8, which is required for induction of apoptosis through the Fas receptor and tumor necrosis factor receptor-1. The mutation, which was found in the tumor cells but not in the normal cells of the patient, modifies the stop codon and adds an Alu repeat to the coding region, thereby lengthening the protein by 88 amino acids. The ability of the altered protein to trigger apoptosis appears to be reduced relative to the normal caspase-8. The antigenic peptide is a nonamer presented by HLA-B*3503. The five last amino acids are encoded by the extension of the reading frame caused by the mutation. This, together with previous observations of CDK4 and beta-catenin mutations, suggests that a significant fraction of the point mutations generating a tumor antigen also play a role in the tumoral transformation or progression.

Transloading of tumor antigen-derived peptides into antigen-presenting cells

The discovery of a steadily growing number of tumor antigens (TAs) has made generic, cell-free, peptide-based cancer vaccines a possible alternative to cytokine-transfected autologous cellular cancer vaccines. The major drawback of peptide vaccines, however, is the poor immunogenicity of peptides. It is commonly thought that for the induction of an effective anticancer immune response, antigen-presenting cells (APCs) have to display TA-derived peptides to T lymphocytes. Polycationic amino acids have been employed in the past to enhance transport of proteins into cells. In a systematic study, the ability of different cationic polymers to transfer fluorescence-tagged peptides to APCs was investigated. We were able to show that several compounds enhance uptake of fluorescence-labeled peptides by APCs to different degrees. The most efficient compound identified, polyarginine (pArg), enhanced peptide delivery by more than 2 logs as compared with cells treated with peptide alone, whereas polylysine (pLys) treatment resulted in approximately 10-fold increased levels of fluorescence. Augmentation of peptide uptake was concentration-dependent, and the molecular weight of pArg or pLys also influenced peptide delivery. Furthermore, highly negatively charged peptides appear to be delivered with higher efficiency, although neutral peptides were also taken up at enhanced rates. Whereas peptide uptake mediated by pLys appears to be due to an at least transient permeabilization of cell membranes, peptide delivery in the presence of pArg may rely on endocytic processes. TA-derived peptides applied as cancer vaccines in conjunction with polycations afforded antitumor protection in animal models.

Cell-free tumor antigen peptide-based cancer vaccines

The central role that tumor antigen-derived peptides play in induction of antitumor immunity makes them ideal candidates for peptide-based cancer vaccines. We have demonstrated that "transloading" is an efficient strategy for importing short peptide ligands into antigen-presenting cells in vitro. Postulating that the transloading procedure might effect peptide uptake by antigen-presenting cells in vivo as well, we tested this approach for the generation of peptide-based cancer vaccines. In the P815 mastocytoma system, we vaccinated mice by s.c. injection of a single, known natural peptide derived from JAK-1 kinase. Whereas vaccination with peptide alone or mixed with incomplete Freund's adjuvant was ineffective, application of the peptide in conjunction with the polycation poly-L-lysine protected a significant number of animals against tumor challenge. Dependent upon the type of poly-L-lysine applied, protection against tumor take was comparable to that achieved with irradiated whole-cell vaccines, genetically modified to secrete granulocyte-macrophage colony-stimulating factor. In the murine melanoma M-3, a combination of four putative tumor antigen-derived peptides was tested as a cancer vaccine. Administered in combination with polycations, these peptides evoked potent antitumor immunity that could not be obtained with the peptides alone or peptides emulsified in incomplete Freund's adjuvant. However, peptide-polycation vaccines applied to the M-3 model were not as efficient as cellular control vaccines, consisting of irradiated interleukin 2 or granulocyte-macrophage colony-stimulating factor-secreting tumor cells.

T cells recognize the VH complementarity-determining region 3 of the idiotypic protein of B cell non-Hodgkin's lymphoma

The idiotypic protein expressed by B lymphoma cells is a clone-specific tumor antigen which may be suitable for immune targeting by T cells. In this study, we cloned the immunoglobulin heavy chain variable gene (VH) of the idiotypic protein from a patient with B cell lymphoma and used a synthetic peptide of 22 amino acids corresponding to the VH complementarity-determining region (CDR)-3 of the idiotypic protein to investigate whether autologous T cells could recognize this unique peptide. We demonstrated that autologous T cells possessing both CD4+ and CD8+ phenotypes could be propagated. The T cells were able to proliferate, secrete cytokines, and lyse autologous cells presensitized with the specific peptide in a major histocompatibility complex-dependent manner. Moreover, these CDR3 peptide-primed T cells were also able to kill autologous lymphoma cells. Our results therefore offer new perspectives for specific therapeutic vaccination for the treatment of B cell lymphoma.

T-cell receptor biases and clonal proliferations in blood and pleural effusions of patients with lung cancer

We sought evidence that pulmonary carcinomas mediate a cellular immunologic response by analyzing T-cell antigen receptor beta-chain variable gene (TCRBV) repertoires of lymphocytes from peripheral blood (PBL) and malignant pleural effusions (PEL) of five lung cancer patients. Expression levels of 27 TCRBV were quantitated by multiprobe RNase protection assay (RPA), and clonal expansions were identified by sequence enrichment nuclease assay (SENA) and junctional region sequencing. Abnormal TCRBV expansions were identified in all subjects by RPA (mean 6.9 +/- 1.7/patient), and their number closely correlated with elapsed time since initial diagnosis (r = 0.97). SENA, performed in specimens from three patients, confirmed the presence of mono or oligoclonality in 48% of abnormal RPA expansions, and further identified T-cell clones among TCRBV with normal expression levels. The majority of clonal expansions were among PEL, and were nearly equally divided between CD4 and CD8. These data show that T-cell repertoires of lung cancer patients are characterized by marked abnormalities and frequent clonal expansions, most likely representing responses to unique, tumor-specific antigens (TSA). Moreover, this process appears exaggerated among PEL, further suggesting that malignant effusions include local proliferations of tumor reactive T cells. These findings imply the presence of lung cancer TSA capable of eliciting cellular immune responses and raise the possibility that selective immunotherapies can ultimately be developed.

Analogues of CTL epitopes with improved MHC class-I binding capacity elicit anti-melanoma CTL recognizing the wild-type epitope

The MHC class-I binding affinity of an epitope is an important parameter determining the immunogenicity of the peptide-MHC complex. In order to improve the immunogenicity of an epitope derived from melanocyte lineage-specific antigen gp100, we performed amino-acid substitutions within the epitope and assayed both HLA-A*0201 binding and CTL recognition. Anchor replacements towards the HLA-A*0201 peptide-binding motif gave rise to peptides with higher HLA-A*0201 binding capacity compared to the wild-type epitope. In addition, several of the gp100 154-162 epitope-analogues were more efficient at target-cell sensitization for lysis by anti-gp100 154-162 CTL compared to the wild-type epitope. These altered gp100 154-162 epitopes were subsequently tested for their capacity to induce CTL responses in vivo using HLA-A*0201/Kb transgenic mice, and in vitro using HLA-A*0201 + donor-derived lymphocytes. Interestingly, the peptide-specific CTL obtained, which were raised against the different gp100 154-162 epitope-analogues, displayed cross-reactivity with target cells endogenously processing and presenting the native epitope. These data demonstrate that altered epitopes can be exploited to elicit native epitope-reactive CTL. The use of epitope-analogues with improved immunogenicity may contribute to the development of CTL-epitope based vaccines in viral disease and cancer.

Transcription of the gene encoding melanoma-associated antigen gp100 in tissues and cell lines other than those of the melanocytic lineage

The expression of the gp100 antigen is generally thought to be confined to cells of the melanocytic lineage, which makes the protein a suitable melanoma-specific marker. Strikingly, after screening a panel of normal tissues, tumour samples and cell lines of non-melanocytic origin, we found transcripts encoding gp100 in virtually every tissue and cell line tested. In contrast, tyrosinase and MART-1/MelanA transcripts were detected only in cells of the melanocytic lineage. However, no gp100 protein could be detected by either Western blotting or cytotoxicity assays. Therefore, at the protein level, gp100 remains exclusive for cells of melanocytic origin despite its transcription in many cell types. The major implication of this finding is that screening of patient material for gp100 expression should preferrably be performed by antibody staining. Reverse transcriptase polymerase chain reaction (RT-PCR) can be employed, provided that it is performed in a tightly controlled, semiquantitative setting.

An N-glycosylated tyrosinase epitope associates with newly synthesized MHC class I molecules in melanoma cells

Endogenous antigenic epitopes are presented to CD8+ T cells by MHC class I molecules. Many endogenous antigens are glycoproteins, and it is not clear what effect the attachment of carbohydrate to potential immunogenic epitopes has on their processing and presentation (i.e., is the carbohydrate moiety removed prior to presentation, or is it presented along with the peptide to T cells?). A major question in this regard is whether natural antigenic epitopes that possess N-linked carbohydrate can associate with class I molecules during assembly in the endoplasmic reticulum (ER). One such antigenic epitope, corresponding to amino acids 369-377 of the enzyme tyrosinase, possesses an N-linked glycosylation site. We have studied the transport and loading of this epitope in streptolysin O-permeabilized melanoma cells. We show here that that the glycosylated epitope is capable of loading onto newly synthesized HLA-A2 molecules in the ER of two melanoma cell lines. The results are discussed in respect to the processing and presentation of the tyrosinase epitope.

Renal-cell carcinoma-specific lysis by cytotoxic T-lymphocyte clones isolated from peripheral blood lymphocytes and tumor-infiltrating lymphocytes

Melanoma and renal-cell carcinoma (RCC) are generally considered to be relatively immunogenic tumor types in humans. In the case of melanoma, many major histocompatibility complex (MHC) class I-restricted tumor-specific cytotoxic T lymphocytes (CTL) have been isolated from either tumor-infiltrating lymphocytes (TIL) or autologous peripheral blood lymphocytes (PBL). In contrast, such CTL have only incidentally been described in the case of RCC. It has often been reported that TIL lines isolated from RCC display non-MHC-restricted and non-specific activity. Here, we report the isolation and characterization of tumor-specific CTL from PBL of one RCC patient and from TIL of another RCC patient. CTL clones 263/17 and 263/45, isolated from the PBL of patient LE-9211, were restricted by HLA-B7. CTL clone 5E, isolated from the TIL of patient LE-8915, was restricted by HLA-B37. The autologous RCC cell lines were efficiently lysed by the CTL clones, whereas normal epithelial cells of the proximal tubuli matched for the restriction element and K562 were not. From a panel of allogeneic RCC cell lines, CTL 5E recognized MZ-1940-RCC. Reactivity to allogeneic RCC sharing HLA-B7 was also observed with CTL 263/17 and 263/45, both of which could lyse the HLA-B7-positive cell line MZ-1851-RCC. Our data provide evidence that common tumor antigens are recognized by CTL on RCC.

Binding and transport of melanoma-specific antigenic peptides by the transporter associated with antigen processing

To gain insight into how tumor antigens are generated and presented, a panel of peptides corresponding to melanoma-specific T cell epitopes were tested for their transport capacity by the transporter associated with antigen processing (TAP). The melanoma epitopes exhibited differential capacities to be transported by TAP in streptolysin O-permeabilized cells, as well as differential competition for peptide binding to TAP. The data indicate that some melanoma-specific epitopes are good substrates for TAP, while others are poor substrates for TAP. One of the epitopes, derived from tyrosinase, was transported into the endoplasmic reticulum (ER), in spite of being a poor competitor for reporter peptide transport and for peptide binding. These results suggest that the melanoma antigens follow distinct pathways for presentation, along the MHC class I pathway.