Differences in T-cell immunity toward tumor-associated antigens in colorectal cancer and breast cancer patients

Targeting the arginine metabolic brake enhances immunotherapy for leukaemia

Therapeutic approaches which aim to target Acute Myeloid Leukaemia through enhancement of patients' immune responses have demonstrated limited efficacy to date, despite encouraging preclinical data. Examination of AML patients treated with azacitidine (AZA) and vorinostat (VOR) in a Phase II trial, demonstrated an increase in the expression of Cancer-Testis Antigens (MAGE, RAGE, LAGE, SSX2 and TRAG3) on blasts and that these can be recognised by circulating antigen-specific T cells. Although the T cells have the potential to be activated by these unmasked antigens, the low arginine microenvironment created by AML blast Arginase II activity acts a metabolic brake leading to T cell exhaustion. T cells exhibit impaired proliferation, reduced IFN-γ release and PD-1 up-regulation in response to antigen stimulation under low arginine conditions. Inhibition of arginine metabolism enhanced the proliferation and cytotoxicity of anti-NY-ESO T cells against AZA/VOR treated AML blasts, and can boost anti-CD33 Chimeric Antigen Receptor-T cell cytotoxicity. Therefore, measurement of plasma arginine concentrations in combination with therapeutic targeting of arginase activity in AML blasts could be a key adjunct to immunotherapy.

The Immunogenicity of Colorectal Cancer in Relation to Tumor Development and Treatment

Although most cancer types have been viewed as immunologically silent until recently, it has become increasingly clear that the immune system plays key roles in the course of tumor development. Remarkable progress towards understanding cancer immunogenicity and tumor-immune system interactions has revealed important implications for the design of novel immune-based therapies. Natural immune responses, but also therapeutic interventions, can modulate the tumor phenotype due to selective outgrowth of resistant subtypes. This is the result of heterogeneity of tumors, with genetic instability as a driving force, and obviously changes the immunogenicity of tumors. In this review, we discuss the immunogenicity of colorectal cancer (CRC) in relation to tumor development and treatment. As most tumors, CRC activates the immune system in various ways, and is also capable of escaping recognition and elimination by the immune system. Tumor-immune system interactions underlie the balance between immune control and immune escape, and may differ in primary tumors, in the circulation, and in liver metastases of CRC. Since CRC immunogenicity varies between tumors and individuals, novel immune-based therapeutic strategies should not only anticipate the molecular profile, but also the immunological profile of a specific tumor.

Peripheral ENO1-specific T cells mirror the intratumoral immune response and their presence is a potential prognostic factor for pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with an average survival of 4-6 months following diagnosis. Surgical resection is the only treatment with curative intent, but resectable PDAC patients are in the minority. Also, unlike other neoplasms, PDAC is resistant to conventional and targeted chemotherapy. Innovative treatments, such as immunotherapy, can be very important and the study of the immune response is fundamental. We previously demonstrated that PDAC patients show tumor-infiltrating T cells specific to α-enolase (ENO1), a glycolytic enzyme over-expressed by pancreatic tumor cells, which plays an important role in promoting cell migration and cancer metastasis. In the present study, we evaluate the functional anticancer proprieties of ENO1-specific T cells isolated from the peripheral blood of PDAC patients. Furthermore, comparing the T cell receptor repertoire of ENO1-specific peripheral and infiltrating tumor T cells from the same patient suggests that ENO1-specific T cells, despite having a different functional profile, can recirculate from the tumor to the periphery. Finally, of clinical relevance, the presence of peripheral ENO1-specific T cells has a prognostic value and significantly correlates with a longer survival.

Immune cell interplay in colorectal cancer prognosis

The immune response to colorectal cancer has proven to be a reliable measure of patient outcome in several studies. However, the complexity of the immune response in this disease is not well understood, particularly the interactions between tumour-associated cells and cells of the innate and adaptive immune system. This review will discuss the relationship between cancer associated fibroblasts and macrophages, as well as between macrophages and T cells, and demonstrate how each population may support or prevent tumour growth in a different immune environment.

Development and clinical evaluation of dendritic cell vaccines for HPV related cervical cancer--a feasibility study

Human papillomavirus infection (HPV) and HPV related immune perturbation play important roles in the development of cervical cancer. Since mature dendritic cells (DCs) are potent antigen-presenting cells (APC), they could be primed by HPV antigens against cervical cancers. In this study we were able to generate, maintain and characterize, both phenotypically and functionally, patient specific dendritic cells in vitro. A randomized Phase I trial with three arms--saline control (arm I), unprimed mature DC (arm II) and autologous tumor lysate primed mature DC (arm III) and fourteen patients was conducted. According to WHO criteria, grade 0 or grade one toxicity was observed in three patients. One patient who received tumor lysate primed dendritic cells and later cis-platin chemotherapy showed a complete clinical response of her large metastatic disease and remained disease free for more than 72 months. Our findings indicate that DC vaccines hold promise as adjuvants for cervical cancer treatment and further studies to improve their efficacy need to be conducted.

Tumor-specific cytotoxic T lymphocyte activity determines colorectal cancer patient prognosis

The composition of tumor-targeted T cell infiltrates is a major prognostic factor in colorectal cancer (CRC) outcome; however, the functional role of these populations in prolonging patient survival remains unclear. Here, we evaluated 190 patients with CRC for the presence of functionally active tumor-infiltrating lymphocytes (TILs), the tumor specificity of these TILs, and the correlation between patient TILs and long-term survival. Using intracytoplasmic cytokine staining in conjunction with HLA multimers loaded with tumor peptide and antigen-specific cytokine secretion assays, we determined that TNF-α expression delineates a population of tumor antigen-specific (TA-specific) cytotoxic T lymphocytes (CTLs) present within tumors from patients with CRC. Upregulation of TNF-α expression in TILs strongly correlated with an increase in the total amount of intratumoral TNF-α, which is indicative of tumor-specific CTL activity. Moreover, a retrospective multivariate analysis of 102 patients with CRC, which had multiple immune parameters evaluated, revealed that increased TNF-α concentration was an independent prognostic factor. Together, these results indicate that the prognostic impact of T cell infiltrates for CRC maybe largely based on subpopulations of active TA-specific T cells within the tumor, suggesting causal implication for these cells in patient survival. Additionally, these results support the use of intratumoral TNF-α, which is indicative of T cell function, as a prognostic parameter for CRC.

Phase II trial of a GM-CSF-producing and CD40L-expressing bystander cell line combined with an allogeneic tumor cell-based vaccine for refractory lung adenocarcinoma

We created a vaccine in which irradiated allogeneic lung adenocarcinoma cells are combined with a bystander K562 cell line transfected with hCD40L and hGM-CSF. By recruiting and activating dendritic cells, we hypothesized that the vaccine would induce tumor regression in metastatic lung adenocarcinoma. Intradermal vaccine was given q14 days×3, followed by monthly ×3. Cyclophosphamide (300 mg/m IV) was administered before the first and fourth vaccines to deplete regulatory T cells. All-trans retinoic acid was given (150/mg/m/d) after the first and fourth vaccines to enhance dendritic cell differentiation. Twenty-four participants were accrued at a single institution from October 2006 to June 2008, with a median age 64 years and median of 4 previous lines of systemic therapy. A total of 101 vaccines were administered. Common toxicities were headache (54%) and site reaction (38%). No radiologic responses were observed. Median overall survival was 7.9 months and median progression-free survival was 1.7 months. Of 14 patients evaluable for immunological study, 5 had peptide-induced CD8 T-cell activation after vaccination. Overall, vaccine administration was feasible in an extensively pretreated population of metastatic lung cancer. Despite a suggestion of clinical activity in the subset with immune response, the trial did not meet the primary endpoint of inducing radiologic tumor regression.

Contribution of the immune system to the chemotherapeutic response

The immune system plays an important role in the surveillance of neoplastic cells by eliminating them before they manifest as full-blown cancer. Despite this, tumors do develop in the presence of a functioning immune system. Conventional chemotherapy and its ability to directly kill tumor cells is one of the most effective weapons in the fight against cancer, however, increasing evidence suggests that the therapeutic efficacy of some cytotoxic drugs relies on their capacity to interact with the immune system. Killing of tumor cells in a manner that favors their capture by immune cells or selective targeting of immunosuppressive pathways by specific chemotherapies promotes the generation of an effective anti-cancer response; however, this alone is rarely sufficient to cause elimination of advanced disease. An understanding of the immunological events occurring in both animal models and patients undergoing chemotherapy will guide decisions for the development of appropriate combinations and scheduling for the integration of chemotherapy with immunotherapy.

Antigen-specific Tregs control T cell responses against a limited repertoire of tumor antigens in patients with colorectal carcinoma

Spontaneous antitumor T cell responses in cancer patients are strongly controlled by Tregs, and increased numbers of tumor-infiltrating Tregs correlate with reduced survival. However, the tumor antigens recognized by Tregs in cancer patients and the impact of these cells on tumor-specific T cell responses have not been systematically characterized. Here we used a broad panel of long synthetic peptides of defined tumor antigens and normal tissue antigens to exploit a newly developed method to identify and compare ex vivo the antigen specificities of Tregs with those of effector/memory T cells in peripheral blood of colorectal cancer patients and healthy subjects. Tregs in tumor patients were highly specific for a distinct set of only a few tumor antigens, suggesting that Tregs exert T cell suppression in an antigen-selective manner. Tumor-specific effector T cells were detectable in the majority of colorectal cancer patients but not in healthy individuals. We detected differences in the repertoires of antigens recognized by Tregs and effector/memory T cells in the majority of colorectal cancer patients. In addition, only effector/memory T cell responses against antigens recognized by Tregs strongly increased after Treg depletion. The selection of antigens according to preexisting T cell responses may improve the efficacy of future immunotherapies for cancer and autoimmune disease.

Immunotherapy of lymphoma and leukemia with T-cell engaging BiTE antibody blinatumomab

Hematologic malignancies are predominantly treated with chemotherapy or a combination of chemotherapy with monoclonal antibodies. Current treatment regimens often are not satisfactory due to severe side effects and a substantial proportion of relapsed patients. This has prompted the development of better tolerated and more efficacious immunotherapeutic strategies for the treatment of lymphoma and leukemia. With blinatumomab (MT103) a first antibody, which can potentially engage all cytotoxic T cells of a patient for tumor cell lysis, is now available for clinical evaluation. Blinatumomab is a single-chain bispecific antibody construct with specificity for CD19 and CD3 belonging to the class of bispecific T cell engager. Here, we review the current progress in development of blinatumomab for treatment of patients with CD19-expressing hematological malignancies.

Fit for purpose? A case study: validation of immunological endpoint assays for the detection of cellular and humoral responses to anti-tumour DNA fusion vaccines

Clinical trials are governed by an increasingly stringent regulatory framework, which applies to all levels of trial conduct. Study critical immunological endpoints, which define success or failure in early phase clinical immunological trials, require formal pre-trial validation. In this case study, we describe the assay validation process, during which the sensitivity, and precision of immunological endpoint assays were defined. The purpose was the evaluation of two multicentre phase I/II clinical trials from our unit in Southampton, UK, which assess the effects of DNA fusion vaccines on immune responses in HLA-A2+ patients with carcinoembryonic antigen (CEA)-expressing malignancies and prostate cancer. Validated immunomonitoring is being performed using ELISA and IFNgamma ELISPOTs to assess humoral and cellular responses to the vaccines over time. The validated primary endpoint assay, a peptide-specific CD8+ IFNgamma ELISPOT, was tested in a pre-trial study and found to be suitable for the detection of low frequency naturally occurring CEA- and prostate-derived tumour-antigen-specific T cells in patients with CEA-expressing malignancies and prostate cancer.

Quantification of the CD8+ T cell response against a mucin epitope in patients with breast cancer

Introduction:

Mucin 1, encoded by the MUC1 gene, is a tumor-associated antigen expressed on the surface of breast cancer cells. It would be of interest to see whether there is a naturally existing T cell immune response against mucin epitopes in cancer patients.

Materials and Methods:

Using tetramer and interferon-γ assays, the immune response to one MUC1 peptide epitope in the peripheral blood of breast cancer patients was quantified. The data were compared with the clinical course of the patients.

Results:

CD8⁺ T cells capable of recognizing the HLA-A*0201-restricted STAPPVHNV epitope were detected in 9 of 19 patients with a frequency ranging 0.01–0.082%. No significant difference was found between the occurrence of epitope-specific CD8⁺ T cells of patients with progressive disease and disease-free patients. However, all patients with stable disease showed a specific immune response, including both patients with the highest frequency.

Conclusions:

The results of this study provide further evidence that a natural specific cellular immune response against this mucin epitope exists in breast cancer patients.

Functional T Cell Responses to Tumor Antigens in Breast Cancer Patients Have a Distinct Phenotype and Cytokine Signature

The overall prevalence with which endogenous tumor Ags induce host T cell responses is unclear. Even when such responses are detected, they do not usually result in spontaneous remission of the cancer. We hypothesized that this might be associated with a predominant phenotype and/or cytokine profile of tumor-specific responses that is different from protective T cell responses to other chronic Ags, such as CMV. We detected significant T cell responses to CEA, HER-2/neu, and/or MAGE-A3 in 17 of 21 breast cancer patients naive to immunotherapy. The pattern of T cell cytokines produced in response to tumor-associated Ags (TAAs) in breast cancer patients was significantly different from that produced in response to CMV or influenza in the same patients. Specifically, there was a higher proportion of IL-2-producing CD8(+) T cells, and a lower proportion of IFN-gamma-producing CD4(+) and/or CD8(+) T cells responding to TAAs compared with CMV or influenza Ags. Finally, the phenotype of TAA-responsive CD8(+) T cells in breast cancer patients was almost completely CD28(+)CD45RA(-) (memory phenotype). CMV-responsive CD8(+) T cells in the same patients were broadly distributed among phenotypes, and contained a high proportion of terminal effector cells (CD27(-)CD28(-)CD45RA(+)) that were absent in the TAA responses. Taken together, these results suggest that TAA-responsive T cells are induced in breast cancer patients, but those T cells are phenotypically and functionally different from CMV- or influenza-responsive T cells. Immunotherapies directed against TAAs may need to alter these T cell signatures to be effective.

Cross-priming of cyclin B1, MUC-1 and survivin-specific CD8+ T cells by dendritic cells loaded with killed allogeneic breast cancer cells

Introduction

The ability of dendritic cells (DCs) to take up whole tumor cells and process their antigens for presentation to T cells ('cross-priming') is an important mechanism for induction of tumor specific immunity.

Methods

In vitro generated DCs were loaded with killed allogeneic breast cancer cells and offered to autologous naïve CD8⁺ T cells in 2-week and/or 3-week cultures. CD8⁺ T cell differentiation was measured by their capacity to secrete effector cytokines (interferon-γ) and kill breast cancer cells. Specificity was measured using peptides derived from defined breast cancer antigens.

Results

We found that DCs loaded with killed breast cancer cells can prime naïve CD8⁺ T cells to differentiate into effector cytotoxic T lymphocytes (CTLs). Importantly, these CTLs primed by DCs loaded with killed HLA-A*0201^- breast cancer cells can kill HLA-A*0201⁺ breast cancer cells. Among the tumor specific CTLs, we found that CTLs specific for HLA-A2 restricted peptides derived from three well known shared breast tumor antigens, namely cyclin B1, MUC-1 and survivin.

Conclusion

This ability of DCs loaded with killed allogeneic breast cancer cells to elicit multiantigen specific immunity supports their use as vaccines in patients with breast cancer.

In situ analysis of FOXP3+ regulatory T cells in human colorectal cancer

The immune system spontaneously responds to tumor-associated antigens in peripheral blood of colorectal cancer (CRC) patients. Regulatory T cells (Treg) are suspected of influencing the interaction between the tumor and immune system and thus the course of malignant diseases. However, the function of Tregs in the development of T cell responses and on the clinical course of CRC is not clear. We analyzed Treg infiltration (FOXP3 staining) in situ in 40 CRC patients and investigated whether there is a correlation to disease stage, systemic T cell response, and survival. Treg infiltration was significantly higher in CRC than in healthy colon. Stromal Treg infiltration was significantly higher than epithelial infiltration in CRC. Furthermore, Treg infiltration in the tumor was significantly higher in limited disease than in metastatic CRC. The average Treg infiltration rate in the tumor was non-significantly higher in patients without systemic TAA-specific T cell response. Survival did not differ between patients with high Treg infiltration and those with low Treg infiltration. In conclusion, a direct link between Treg infiltration in the tumor and the development of a systemic T cell response in CRC cannot be proven. However, local Treg infiltration was significantly higher in limited disease, in which a systemic TAA-directed T cell responses is less frequently observed.

The Shaping of a Polyvalent and Highly Individual T-Cell Repertoire in the Bone Marrow of Breast Cancer Patients

We analyzed the T-cell repertoires from the bone marrow of 39 primary operated breast cancer patients and 11 healthy female donors for the presence and frequencies of spontaneously induced effector/memory T lymphocytes with peptide-HLA-A2-restricted reactivity against 10 breast tumor-associated antigens (TAA) and 3 normal breast tissue–associated antigens by short-term IFN-γ enzyme-linked immunospot (ELISpot) analysis. Sixty-seven percent of the patients recognized TAAs with a mean frequency of 144 TAA reactive cells per 106 T cells. These patients recognized simultaneously an average of 47% of the tested TAAs. The T-cell repertoire was highly polyvalent and exhibited pronounced interindividual differences in the pattern of TAAs recognized by each patient. Strong differences of reactivity were noticed between TAAs, ranging from 100% recognition of prostate-specific antigenp141-149 to only 25% recognition of MUC1p12-20 or Her-2/neup369-377. In comparison with TAAs, reactivity to normal breast tissue–associated antigens was lower with respect to the proportions of responding patients (30%) and recognized antigens (27%), with a mean frequency of only 85/106 T cells. Healthy individuals also contained TAA-reactive T cells but this repertoire was more restricted and the frequencies were in the same range as T cells reacting to normal breast tissue–associated antigens. Our data show a highly individual T-cell repertoire for recognition of TAAs in breast cancer patients. This has potential relevance for T-cell immune diagnostics, for tumor vaccine design, and for predicting immune responsiveness. (Cancer Res 2006; 66(16): 8258-65)

Genetic vaccines against Ep-CAM break tolerance to self in a limited subset of subjects: initial identification of predictive biomarkers

The epithelial cell adhesion molecule, Ep-CAM, has been historically considered a target of passive immunotherapy using monoclonal antibodies, and more recently, of a first Pox-vector-based cancer vaccine Phase I trial in colorectal cancer patients. To shed further light on the use of this antigen, we isolated the mouse and rhesus homologues of human Ep-CAM and explored different genetic vaccination modalities based on the use of adenoviral vectors as well as DNA electroporation (DNA-EP). Immune responses to Ep-CAM were measured by IFN-gamma ELISPOT and intracellular staining assays using overlapping sets of peptides covering the entire coding regions. We found the most powerful vaccination regimen to be constituted by DNA-EP-prime/Adeno-boost mixed-modality protocols. Vaccination in rhesus macaques resulted in breakage of immunological tolerance in a minority of cases. Similarly, a low frequency of responders was observed with the mouse Ep-CAM vaccine in outbred CD1 mice. When immunized CD1 mice were analyzed for MHC haplotype and TCR expression levels, we observed that immune responders all had the same q/q MHC class I haplotype and showed higher expression levels of the TCRVbeta4 and TCRVbeta8 T cell receptors. Our results underscore the current limitations in our capacity to induce efficient cancer vaccines against self antigens like Ep-CAM, but also represent a first effort to identify predictive biomarkers of response.

Identification of alpha-fetoprotein-derived peptides recognized by cytotoxic T lymphocytes in HLA-A24+ patients with hepatocellular carcinoma

Alpha-fetoprotein (AFP) has been proposed as a potential target forT-cell-based immunotherapy for hepatocellular carcinoma (HCC), but the number of its epitopes that have been identified is limited and the status of AFP-specific immunological responses in HCC patients has not been well-characterized. To address the issue, we examined the possibility of inducing AFP-specific cytotoxic T cells (CTLs) using novel HLA-A*2402-restricted T-cell epitopes (HLA, human leukocyte antigen) derived from AFP and then analyzed the relationship between its frequency of occurrence and clinical features associated with patients having HCC. Five AFP-derived peptides containing HLA-A*2402 binding motifs and showing high binding affinity to HLA-A*2402 induced CTLs to produce IFN-gamma and kill an AFP-producing hepatoma cell line. The frequency of AFP-specific CTLs was 30-190 per 1 x 10(6) peripheral blood mononuclear cells, which was the same as that of other immunogenic cancer associated antigen-derived epitopes. Analyses of the relationships between AFP-specific CTL responses and clinical features of patients with HCC revealed that AFP epitopes were more frequently recognized by CTLs in patients with advanced HCC correlating to tumor factors or the stage of TNM classification. The analyses of CTL responses before and after HCC treatments showed that the treatments changed the frequency of AFP-specific CTLs. In conclusion, we identified five HLA-A*2402-restricted T-cell epitopes derived from AFP. The newly identified AFP epitopes could be a valuable component of HCC immunotherapy and for analyzing host immune responses to HCC.

Pre-existing T-cell immunity against mucin-1 in breast cancer patients and healthy volunteers

PURPOSE

There is evidence that some tumor patients are able to generate tumor-associated antigen (TAA)-specific T-cell immunity spontaneously. However, little is understood about the existence and nature of self-reactive T-cells that recognize TAA in healthy donors (HD).

METHODS

Human mucin (MUC-1), a highly glycosylated transmembrane protein, is a well characterized TAA expressed by epithelial tumors. We compared endogenous MUC-1-specific T-cell immunity of breast cancer patients (BCP) and healthy volunteers using two MUC-1-derived HLA-A*0201-restricted peptides (MUC-1(950-958), MUC-1(12-20)). Antigen-dependent interferon (IFN)-gamma and Granzyme B expression of T-cells were analysed by a reverse transcription-polymerase chain reaction (qRT-PCR)-based assay.

RESULTS

A 32% of BCP and 43% of healthy volunteers revealed pre-existent CD8+ T-cells specific for MUC-1(950-958) but not for MUC-1(12-20). In patients, MUC-1-specific T-cells have been detected mainly in early stage disease prior adjuvant therapy. Those T-cells showed MUC-1-dependent IFN-gamma production after short-term stimulation but no clear Granzyme B expression. However, after repetitive in vitro stimulations using peptide-pulsed CD40-stimulated B-cell lines as autologous antigen presenting cells (APC) T-cell lines exhibited lytic capacity against HLA-A*0201+/MUC-1+ tumor cells.

CONCLUSION

MUC-1(950-958) is a dominant tumor antigen against which CD8+ T-cells were found frequently in BCP as well as in HD. Until now, this was only known for MelanA/MART-1. In contrast to previous reports, MUC-1-specific immunity was not linked to gender or number of pregnancies in women. Whether MUC-1(950-958)-related immunity highlights a yet unknown cross-reactivity in HD remains unclear. The presence of MUC-1-specific T-cells in some BCP may reflect a balance between immune tolerance and immune defence during aetiopathology.

Presence and specificity of tumor associated lymphocytes from ascites fluid in prostate cancer

BACKGROUND

In the present study, we had the rare opportunity to study immunological responses of TAL from ascites fluid in a patient with hormone-refractory prostate cancer.

METHODS

We evaluated tumor antigen-specific T-cell responses, induced by either prostate specific antigen (PSA) pulsed dendritic cells (DCs) or PSA peptides, in TAL and peripheral blood lymphocytes.

RESULTS

DC stimulation with PSA protein induced recognition of naturally processed PSA epitopes by both blood and ascites T cells. In contrast, only ascites T cells recognized the PSA-3 peptide, after stimulation with PSA-pulsed DCs or peptides. Finally, although IFNgamma secreting T cells were detectable in both blood and ascites by ELISPOT, multiplex cytokine assay detected the presence of predominantly Th2 cytokines.

CONCLUSIONS

Although tumor antigen-specific TAL were detected in ascites fluid, these cells were producing immunosuppressive cytokines which may contribute to tumor escape from recognition and/or destruction by the immune system.

CD8+ T-cell response against MUC1-derived peptides in gastrointestinal cancer survivors

The tumor-associated antigens CEA, MUC1 and Her2/neu are broadly expressed in gastrointestinal tumors, and are attractive candidates for targeting by T-cell-based immunotherapy. However, little is known about the natural cytotoxic T-cell response of patients suffering from colorectal or gastric carcinoma against these three as well as other antigens. Using a quantitative reverse transcription-polymerase chain reaction-based assay for IFN-gamma, we analyzed the CD8+ T-cell repertoire present in the blood of HLA-A2+ gastrointestinal tumor survivors against five known epitopes derived from CEA, MUC1 and Her2/neu. The results show that most of the patients (16 from 22 tested) have detectable, peripheral CD8+ T cells directed against at least one of these three proteins. Interestingly, the majority of these patients reacts to the two MUC1-derived HLA-A*0201 epitopes tested (14 from 16), demonstrating that this protein represents one dominant target for CD8+ T cells in gastrointestinal cancer.

T cell responses against tumor associated antigens and prognosis in colorectal cancer patients

INTRODUCTION: Spontaneous T cell responses against specific tumor-associated antigens (TAA) are frequently detected in peripheral blood of tumor patients of various histiotypes. However, little is known about whether these circulating, spontaneously occurring, TAA-reactive T cells influence the clinical course of disease. METHODS: Fifty-four HLA-A2 positive colorectal cancer patients had been analyzed for the presence of T cell responses against epitopes derived from the TAA Ep-CAM, her-2/neu, and CEA either by ELISPOT assay or by intracellular cytokine staining. Then, Kaplan-Meier survival analysis was performed comparing T-cell-responders and T-cell-non-responders. For comparison, a group of T-cell-non-responders was compiled stringently matched to T-cell-responders based on clinical criteria and also analyzed for survival. RESULTS: Sixteen out of 54 patients had a detectable T cell response against at least one of the three tested TAA. Two out of 21 patients (9.5%) with limited stage of disease (UICC I and II) and 14 out of 33 patients (42.4%) with advanced disease (UICC III and IV) were T cell response positive. Comparing all T-cell-responders (n = 16) and all T-cell-non-responders (n = 38), no survival difference was found. In an attempt to reduce the influence of confounding clinical factors, we then compared 16 responders and 16 non-responders in a matched group survival analysis; and again no survival difference was found (p = 0.7). CONCLUSION: In summary, we found no evidence that spontaneous peripheral T cell responses against HLA-A2-binding epitopes of CEA, her-2/neu and Ep-CAM are a strong prognostic factor for survival.

Phase I study of sequential vaccinations with fowlpox-CEA(6D)-TRICOM alone and sequentially with vaccinia-CEA(6D)-TRICOM, with and without granulocyte-macrophage colony-stimulating factor, in patients with carcinoembryonic antigen-expressing carcinomas

PURPOSE

Our previous clinical experience with vaccinia and replication-defective avipox recombinant carcinoembryonic antigen (CEA) vaccines has demonstrated safety and clinical activity with a correlation between CEA-specific immune response and survival. Preclinical evidence demonstrated that the addition of the transgenes for three T-cell costimulatory molecules (B7-1, ICAM-1, LFA-3, designated TRICOM) results in a significant improvement in antigen-specific T-cell responses and antitumor activity. We describe here the first trial in humans of the CEA-TRICOM vaccines (also including an enhancer agonist epitope within the CEA gene).

PATIENTS AND METHODS

Fifty-eight patients with advanced CEA-expressing cancers were accrued to eight cohorts that involved vaccinations with the following: replication-defective fowlpox recombinant (rF)-CEA(6D)-TRICOM; primary vaccination with recombinant vaccinia (rV)-CEA(6D)-TRICOM plus rF-CEA(6D)-TRICOM booster vaccinations; and rV-CEA(6D)-TRICOM and then rF-CEA(6D)-TRICOM, plus granulocyte-macrophage colony-stimulating factor (GM-CSF) with vaccines, or with divided doses of vaccine with GM-CSF. Vaccines were administered every 28 days for six doses and then once every 3 months. Reverting to treatments every 28 days was allowed if patients progressed on the 3-month schedule.

RESULTS

In this phase I study, no significant toxicity was observed. Twenty-three patients (40%) had stable disease for at least 4 months, with 14 of these patients having prolonged stable disease (> 6 months). Eleven patients had decreasing or stable serum CEA, and one patient had a pathologic complete response. Enhanced CEA-specific T-cell responses were observed in the majority of patients tested.

CONCLUSION

We demonstrated that the CEA-TRICOM vaccines are safe and can generate significant CEA-specific immune responses, and they seem to have clinical benefit in some patients with advanced cancer.

Identification of an epitope from the epithelial cell adhesion molecule eliciting HLA-A*2402-restricted cytotoxic T-lymphocyte responses

Because the epithelial cell adhesion molecule (Ep-CAM) is expressed in almost all carcinomas and human leucocyte antigen (HLA)-A*2402 is the most common allele in many ethnic groups, including Japanese, the identification of peptide sequences, which elicit HLA-A*2402-restricted Ep-CAM-specific cytotoxic T-lymphocyte (CTL) responses, would facilitate specific immunotherapy for various histological types of carcinomas. An epitope was identified through the following steps: (i) computer-based epitope prediction from the amino acid sequence of Ep-CAM, (ii) major histocompatibility complex (MHC) stabilization assay to determine the affinity of the predicted peptide with HLA-A*2402 molecules, (iii) stimulation of CD8+ T cells with peptide-pulsed dendritic cells and (iv) testing the CTL specificity by means of enzyme-linked immunospot (ELISPOT) assays, CTL assays and MHC/peptide-tetramer staining. Peripheral CD8+ T cells of four of five healthy donors after three rounds of stimulation with the peptide Ep-CAM173-181 (RYQLDPKFI) secreted interferon-gamma in ELISPOT assays when exposed to the peptide. A CTL clone specific to the peptide efficiently lysed Ep-CAM-expressing cancer cell lines in an HLA-A*2402-restricted fashion. Endogenous processing and presentation of the peptide in a lung cancer cell line were confirmed by means of cold target inhibition assays. The CTL clone was also lytic to normal bronchial epithelial cells but to a lesser extent at low effector: target ratios. All these data suggest that the peptide-specific CTL responses may play some roles both in anti-cancer and autoimmune reactions. The peptide should prove useful to study anti-Ep-CAM CTL responses among population possessing HLA-A*2402.

Tissue expression and sero-reactivity of tumor-specific antigens in colorectal cancer

The expression of 14 individual and two groups of tumor antigens was characterized for colorectal carcinoma by RT-PCR using 26 colorectal carcinoma specimens, eight cell lines, six samples of patients with inflammatory bowl diseases, and nine specimens from different locations of an individual patient with a metastasized rectal carcinoma. The most frequently detected mRNAs were MAGE-A1 (58%), GAGE-3-7 (54%), and cTAGE-5a (31%). At medium frequencies (12-19%) we found cTAGE-1, MAGE-A2, se57-1, RAGE-4, and GAGE-1,2,8, while other tumor antigens were expressed rarely (<9%). 85% of the samples were positive for at least one of the most frequently expressed antigens. Using a secondary SEREX approach and sera of eight colorectal cancer patients we found reactive antibodies against recombinant cTAGE-1 (2 sera), se57-1 (2), truncated GAGE (1), and MAGE-A1 (1). We conclude that certain cancer-germline genes can be detected in colorectal cancer and might therefore be promising targets for immunotherapy.

Activated platelets rapidly up-regulate CD40L expression and can effectively mature and activate autologous ex vivo differentiated DC

Background DC are a promising immunotherapeutic for treatment of infectious/malignant disease. For clinical trials, immature DC generated from precursor cells such as monocytes, using serum-free media containing GM-CSF and IL-4, can be matured with specific cytokines/factors. CD40 ligand (CD40L) plays an important role in DC activation/maturation but is not available for clinical applications. These studies evaluated the feasibility of using activated platelets with elevated CD40L surface expression to stimulate autologous DC maturation. Methods Pilot and clinical scale studies were executed using magnetic/centrifugal separation. Monocyte precursors were differentiated to immature DC with GM-CSF and IL-4 and the ability of activated autologous platelets to mature these cells was evaluated on the basis of phenotype and function. Results In small-scale studies, DC cultures stimulated with activated autologous platelets (CD40L-AP), tumor necrosis factor-alpha (TNF-alpha) or soluble CD40L (sCD40L) up-regulated expression of phenotype markers indicative of activation and maturation. CD86 expression was significantly enhanced (P<0.05) by stimulation with either CD40L-AP (75.5+/-14.5%) or sCD40L (80.5%+/-5.3%) compared with immature DC (55.2+/-14.8%), as were CD80 and CD83. Similarly, in large-scale studies using Isolex 300I to enrich for monocytes and platelets for DC generation/maturation on a clinical scale, stimulation with CD40L-AP increased CD86 and CD80 expression as well as the ability to stimulate allogeneic lymphocytes compared with control cultures. Discussion These results demonstrate that thrombin-activated platelets express CD40L and are effective at inducing matured DC with potent immunogenic activity. Furthermore, these studies demonstrate the feasibility of this approach for clinical immunotherapeutic interventions.