Vaccination of melanoma patients with peptide- or tumor lysate-pulsed dendritic cells

Human Glioma-Induced Immunosuppression Involves Soluble Factor(s) That Alters Monocyte Cytokine Profile and Surface Markers

Patients with gliomas exhibit deficient in vitro and in vivo T cell immune activity, and human glioblastoma culture supernatants (GCS) inhibit in vitro T lymphocyte responses. Because APC are essential for initiating and regulating T cell responses, we investigated whether GCS would affect cytokines produced by monocytes and T cells from healthy donors of PBMC. Incubation of PBMC with GCS decreased production of IL-12, IFN-γ, and TNF-α, and increased production of IL-6 and IL-10. The GCS-induced changes in IL-12 and IL-10 occurred in monocytes, and involved changes in IL-12 p40 and IL-10 mRNA expression. Incubation with GCS also resulted in reduced expression of MHC class II and of CD80/86 costimulatory molecules on monocytes. The immunosuppressive effects were not the result of IL-6 or TGF-β1 that was detected in GCS. However, it was due to a factor(s) that is resistant to pH extremes, differentially susceptible to temperature, susceptible to trypsin, and has a minimum molecular mass of 40 kDa. Our findings show that glioblastoma-generated factors that are known to suppress T cell responses alter the cytokine profiles of monocytic APC that, in turn, inhibit T cell function. This model indicates that monocytes can serve as an intermediate between tumor-generated immune-suppressive factors and the T cell responses that are suppressed in gliomas.

Immunotherapy of metastatic malignant melanoma by a vaccine consisting of autologous interleukin 2-transfected cancer cells: outcome of a phase I study

We performed a phase I trial to evaluate the safety and tolerability of repeated skin injections of IL-2-transfected autologous melanoma cells into patients with advanced disease. Cell suspensions, propagated from excised metastases, were IL-2 gene transfected by adenovirus-enhanced transferrinfection and X-irradiated prior to injection. Vaccine production was successful in 54% of the patients. Fifteen patients (37%) received two to eight skin vaccinations of either 3 x 10(6) (intradermal) or 1 x 10(7) (half intradermal, half subcutaneous) transfected melanoma cells per vaccination (secreting 140-17,060 biological response modifier program units of IL-2/10(6) cells/24 hr). Analyses of safety and efficacy were carried out in 15 and 14 patients, respectively. Overall, the vaccine was well tolerated. All patients displayed modest local reactions (erythema, induration, and pruritus) and some experienced flu-like symptoms. Apart from newly appearing (4 of 14) and increasing (5 of 14) anti-adenovirus and newly detectable anti-nuclear antibody titers (1 of 15), recipients developed de novo or exhibited increased melanoma cell-specific delayed-type hypersensitivity (DTH) reactions (8 of 15) and vitiligo (3 of 15) and showed signs of tumor regression (3 of 15). This supports the idea of a vaccine-induced or -amplified anti-cancer immune response. None of the patients exhibited complete or partial regressions, but five of them experienced periods of disease stabilization. Three of these individuals received more than the four planned vaccinations and their mean survival time was 15.7 +/- 3.5 months as compared to 7.8 +/- 4.6 months for the entire patient cohort. These data indicate that IL-2-producing, autologous cancer cells can be safely administered to stage IV melanoma patients and could conceivably be of benefit to patients with less advanced disease.

High frequency of expression of MAGE genes in human hepatocellular carcinoma

AIMS/BACKGROUND

Activation of human MAGE genes leads to the expression of a set of tumor rejection antigens, which are recognized by cytotoxic T lymphocytes. The antigens may become the targets of immunotherapy. The expression of MAGE genes was originally found in, but is not restricted, to melanomas. The aim of this study was to investigate the expression of MAGE genes in human hepatocellular carcinomas.

METHODS

The expression of MAGE-1, -2, -3, -4 genes in tumorous and corresponding non-tumorous liver tissue was studied using a reverse-transcription polymerase chain reaction.

RESULTS

In the 50 hepatocellular carcinomas studied, MAGE-1, -2, -3, -4 mRNA expression was detected in 23 (46%), 17 (34%), 21 (42%) and 8 (16%), respectively. Seventy-four percent of the hepatocellular carcinomas expressed at least one of the MAGE genes. MAGE mRNAs were not detected in the corresponding non-tumor liver tissues. MAGE gene expression was not significantly correlated with clinicopathological factors.

CONCLUSIONS

The MAGE genes are expressed in a high percentage of hepatocellular carcinomas; the MAGE gene products are potential targets for tumor-specific immunotherapy.

Immunophenotypical and functional heterogeneity of dendritic cells generated from murine bone marrow cultured with different cytokine combinations: implications for anti-tumoral cell therapy

Dendritic cells (DC) are professional antigen-presenting cells that can be used as immune adjuvant for anti-tumoural therapies. This approach requires the generation of large quantities of DC that are fully characterized on the immunophenotypical and functional levels. In a murine model, we analysed the in vitro effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) alone or combined with interleukin-4 (IL-4) or Flt3 ligand (Flt3-L) on the number, immunophenotype and functions of bone marrow-derived DC. In GM-CSF cultures, we have identified two populations based on their level of expression of major histocompatibility complex (MHC) class II molecules: MHC-IIhi cells, exhibiting the typical morphology and immunophenotype of myeloid DC (CD11c+ 33D1+ DEC-205+ F4/80+), and MHC-IIlo cells, heterogeneous for DC markers (30% CD11c+; 50% 33D1+; DEC-205-; F4/80+). The addition of Flt3-L to GM-CSF induced a twofold increase in MHC-IIhi DC number; besides, the MHC-IIlo cells lost all DC markers. In contrast, after addition of IL-4 to GM-CSF, the two populations displayed a very similar phenotype (CD11c+ 33D1- DEC-205+ F4/80-), differing only in their expression levels of MHC class II and costimulatory molecules, and showed similar stimulatory activity in mixed leucocyte reaction. We next analysed the migration of these cultured cells after fluorescent labelling. Twenty-four hours after injection into the footpads of mice, fluorescent cells were detected in the draining popliteal lymph nodes, with an enhanced migration when cells were cultured with GM-CSF+Flt3-L. Finally, we showed that MHC-IIhi were more efficient than MHC-IIlo cells in an anti-tumoral vaccination protocol. Altogether, our data highlight the importance of characterizing in vitro-generated DC before use in immunotherapy.

Idiotype Vaccination Using Dendritic Cells After Autologous Peripheral Blood Stem Cell Transplantation for Multiple Myeloma—A Feasibility Study

The idiotype (Id) determinant on the multiple myeloma (MM) protein can be regarded as a tumor-specific marker. Immunotherapy directed at the MM Id may stem the progression of this disease. We report here on the first 12 MM patients treated at our institution with high-dose therapy and peripheral blood stem cell transplantation (PBSCT) followed by Id immunizations. MM patients received PBSCT to eradicate the majority of the disease. PBSCT produced a complete response in 2 patients, a partial response in 9 patients and stable disease in 1 patient. Three to 7 months after high-dose therapy, patients received a series of monthly immunizations that consisted of two intravenous infusions of Id-pulsed autologous dendritic cells (DC) followed by five subcutaneous boosts of Id/keyhole limpet hemocyanin (KLH) administered with adjuvant. Between 1 and 11 × 106 DC were obtained by leukapheresis in all patients even after PBSCT. The administration of Id-pulsed DC and Id/KLH vaccines were well tolerated with patients experiencing only minor and transient side effects. Two of 12 patients developed an Id-specific, cellular proliferative immune response and one of three patients studied developed a transient but Id-specific cytotoxic T-cell (CTL) response. Eleven of the 12 patients generated strong KLH-specific cellular proliferative immune responses showing the patients’ immunocompetence at the time of vaccination. The two patients who developed a cellular Id-specific immune response remain in complete remission. Of the 12 treated patients, 9 are currently alive after autologous transplantation with a minimum follow-up of 16 months, 2 patients died because of recurrent MM and 1 patient succumbed to acute leukemia. These studies show that patients make strong anti-KLH responses despite recent high-dose therapy and that DC-based Id vaccination is feasible after PBSCT and can induce Id-specific T-cell responses. Further vaccine development is necessary to increase the proportion of patients that make Id-specific immune responses. The clinical benefits of Id vaccination in MM remain to be determined.

Long-Term Culture of Human CD34+ Progenitors With FLT3-Ligand, Thrombopoietin, and Stem Cell Factor Induces Extensive Amplification of a CD34−CD14− and a CD34−CD14+ Dendritic Cell Precursor

Current in vitro culture systems allow the generation of human dendritic cells (DCs), but the output of mature cells remains modest. This contrasts with the extensive amplification of hematopoietic progenitors achieved when culturing CD34+ cells with FLT3-ligand and thrombopoietin. To test whether such cultures contained DC precursors, CD34+ cord blood cells were incubated with the above cytokines, inducing on the mean a 250-fold and a 16,600-fold increase in total cell number after 4 and 8 weeks, respectively. The addition of stem cell factor induced a further fivefold increase in proliferation. The majority of the cells produced were CD34−CD1a− CD14+(p14+) and CD34−CD1a−CD14−(p14−) and did not display the morphology, surface markers, or allostimulatory capacity of DC. When cultured with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4), both subsets differentiated without further proliferation into immature (CD1a+, CD14−, CD83−) macropinocytic DC. Mature (CD1a+, CD14−, CD83+) DCs with high allostimulatory activity were generated if such cultures were supplemented with tumor necrosis factor- (TNF). In addition, p14− cells generated CD14+ cells with GM-CSF and TNF, which in turn, differentiated into DC when exposed to GM-CSF and IL-4. Similar results were obtained with frozen DC precursors and also when using pooled human serum AB+ instead of bovine serum, emphasizing that this system using CD34+ cells may improve future prospects for immunotherapy.

Long-Term Culture of Human CD34+ Progenitors With FLT3-Ligand, Thrombopoietin, and Stem Cell Factor Induces Extensive Amplification of a CD34−CD14− and a CD34−CD14+ Dendritic Cell Precursor

Current in vitro culture systems allow the generation of human dendritic cells (DCs), but the output of mature cells remains modest. This contrasts with the extensive amplification of hematopoietic progenitors achieved when culturing CD34+ cells with FLT3-ligand and thrombopoietin. To test whether such cultures contained DC precursors, CD34+ cord blood cells were incubated with the above cytokines, inducing on the mean a 250-fold and a 16,600-fold increase in total cell number after 4 and 8 weeks, respectively. The addition of stem cell factor induced a further fivefold increase in proliferation. The majority of the cells produced were CD34−CD1a− CD14+(p14+) and CD34−CD1a−CD14−(p14−) and did not display the morphology, surface markers, or allostimulatory capacity of DC. When cultured with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4), both subsets differentiated without further proliferation into immature (CD1a+, CD14−, CD83−) macropinocytic DC. Mature (CD1a+, CD14−, CD83+) DCs with high allostimulatory activity were generated if such cultures were supplemented with tumor necrosis factor- (TNF). In addition, p14− cells generated CD14+ cells with GM-CSF and TNF, which in turn, differentiated into DC when exposed to GM-CSF and IL-4. Similar results were obtained with frozen DC precursors and also when using pooled human serum AB+ instead of bovine serum, emphasizing that this system using CD34+ cells may improve future prospects for immunotherapy.

Generation of phagocytic MAK and MAC-DC for therapeutic use: characterization and in vitro functional properties

Phagocytic cells with macrophage or dendritic cell phenotype, able to capture and ingest tumor cells, were derived in large numbers from peripheral blood mononuclear cells using two different activation procedures. Peripheral blood mononuclear cells were stimulated in nonadherent conditions in the presence of human AB serum with either granulocyte-macrophage colony-stimulating factor and dihydroxy-vitamin D3 for 7 days and with interferon-gamma for the last 18 hours to obtain activated macrophages (MAK) or with granulocyte-macrophage colony-stimulating factor and interleukin-13 for 7 days (with fresh interleukin-13 added on day 4) to obtain macrophage-dendritic cells (MAC-DC). A strong ability of MAC-DC to phagocytose yeasts was observed, in contrast to a low-intermediate phagocytosis capacity by MAK. Both CD14+ FCgammaR+ (FcgammaRI/CD64, FcgammaRII/CD32, FcgammaRIII/CD16) MAK and CD1a+/CD86+, CD14- MAC-DC were able to phagocytose whole tumor cells. However, only MAK phagocytosis was enhanced by FcgammaR engagement. MAK but not MAC-DC could lyse tumor cell in antibody-dependent cell cytotoxicity assays, via FcgammaRI. Thus, MAK as well as MAC-DC may represent valuable tools for different in vivo therapy strategies that do or do not include the use of monoclonal antibodies.

Idiotype Vaccination Using Dendritic Cells After Autologous Peripheral Blood Stem Cell Transplantation for Multiple Myeloma—A Feasibility Study

The idiotype (Id) determinant on the multiple myeloma (MM) protein can be regarded as a tumor-specific marker. Immunotherapy directed at the MM Id may stem the progression of this disease. We report here on the first 12 MM patients treated at our institution with high-dose therapy and peripheral blood stem cell transplantation (PBSCT) followed by Id immunizations. MM patients received PBSCT to eradicate the majority of the disease. PBSCT produced a complete response in 2 patients, a partial response in 9 patients and stable disease in 1 patient. Three to 7 months after high-dose therapy, patients received a series of monthly immunizations that consisted of two intravenous infusions of Id-pulsed autologous dendritic cells (DC) followed by five subcutaneous boosts of Id/keyhole limpet hemocyanin (KLH) administered with adjuvant. Between 1 and 11 × 106 DC were obtained by leukapheresis in all patients even after PBSCT. The administration of Id-pulsed DC and Id/KLH vaccines were well tolerated with patients experiencing only minor and transient side effects. Two of 12 patients developed an Id-specific, cellular proliferative immune response and one of three patients studied developed a transient but Id-specific cytotoxic T-cell (CTL) response. Eleven of the 12 patients generated strong KLH-specific cellular proliferative immune responses showing the patients’ immunocompetence at the time of vaccination. The two patients who developed a cellular Id-specific immune response remain in complete remission. Of the 12 treated patients, 9 are currently alive after autologous transplantation with a minimum follow-up of 16 months, 2 patients died because of recurrent MM and 1 patient succumbed to acute leukemia. These studies show that patients make strong anti-KLH responses despite recent high-dose therapy and that DC-based Id vaccination is feasible after PBSCT and can induce Id-specific T-cell responses. Further vaccine development is necessary to increase the proportion of patients that make Id-specific immune responses. The clinical benefits of Id vaccination in MM remain to be determined.

Clinical implications of the new biology in the development of melanoma vaccines

There has been a resurgence in clinical research of vaccine therapies, particularly for the treatment of melanoma. The renewed interest in this field is attributable to an increased understanding regarding the immune response to tumors and the immunobiology of melanoma. Molecular biology techniques have enabled investigators to develop genetically engineered tumor vaccines that are intended to favor the type 1 immune response over the type 2 response. Melanoma-associated antigens have been characterized at the molecular level and are currently being investigated in clinical trials. Dendritic cell biology has also provided a potent method to present antigens to the host for immunization. Lastly, vaccines are being explored as a method to generate immune T-cells for adoptive immunotherapy. These new areas of clinical investigation will be reviewed in the context of the historical developments that have laid the foundations of this field.

Phase II prostate cancer vaccine trial: report of a study involving 37 patients with disease recurrence following primary treatment

BACKGROUND

A phase II trial was conducted to assess the efficacy of infusions of dendritic cells (DC) and two HLA-A2-specific prostate-specific membrane antigen (PSMA) peptides (PSM-P1 and -P2). This report describes the evaluation of 37 subjects admitted with presumed local recurrence of prostate cancer after primary treatment failure.

METHODS

All subjects received six infusions of DC pulsed with PSM-P1 and -P2 at 6-week intervals. Clinical monitoring was conducted pre-, during, and post-phase II study. Data included: complete blood count, bone and total alkaline phosphatase, prostate markers, physical examination, performance status, bone scan, ProstaScint scan, and chest X-ray, as well as other assays to monitor cellular and humoral immune responses.

RESULTS

One complete and 10 partial responders were identified from this group based on National Prostate Cancer Project criteria, or on a 50% reduction of prostate-specific antigen (PSA), or on a significant resolution in lesions (biopsy-proven when possible) on ProstaScint scan.

CONCLUSIONS

About 30% of study participants in this group showed a positive response at the conclusion of the trial. This study suggests that DC-based cancer vaccines may provide an alternative therapy for prostate cancer patients whose primary treatment failed.

Dendritic cell vaccines for cancer immunotherapy

Human tumors express a number of protein antigens that can be recognized by T cells, thus providing potential targets for cancer immunotherapy. Dendritic cells (DCs) are rare leukocytes that are uniquely potent in their ability to present antigens to T cells, and this property has prompted their recent application to therapeutic cancer vaccines. Isolated DCs loaded with tumor antigen ex vivo and administered as a cellular vaccine have been found to induce protective and therapeutic anti-tumor immunity in experimental animals. In pilot clinical trials of DC vaccination for patients with non-Hodgkin's lymphoma and melanoma, induction of anti-tumor immune responses and tumor regressions have been observed. Additional trials of DC vaccination for a variety of human cancers are under way, and methods for targeting tumor antigens to DCs in vivo are also being explored. Exploitation of the antigen-presenting properties of DCs thus offers promise for the development of effective cancer immunotherapies.

Cellular and humoral immune responses in patients with metastatic renal cell carcinoma after vaccination with antigen pulsed dendritic cells

PURPOSE

Dendritic cells are the most potent stimulators of immune responses including antitumor responses. We performed a pilot study of cultured antigen loaded dendritic cells in patients with metastatic renal cell carcinoma.

MATERIALS AND METHODS

Dendritic cells were obtained by culturing plastic adherent mononuclear cells from peripheral blood for 5 days in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4. Day 5 dendritic cells were loaded with cell lysate from cultured autologous tumor cells and with the immunogenic protein keyhole-limpet hemocyanin (KLH) which serves as a helper antigen and as a tracer molecule. During the antigen pulse dendritic cells were activated with a combination of tumor necrosis factor-alpha and prostaglandin E2. Dendritic cells were administered by 3 intravenous infusions at monthly intervals. Cellular and humoral immune responses to KLH and cell lysate were measured in vitro before and after the vaccinations.

RESULTS

Preparation of 12 dendritic cell vaccines from patients with advanced renal cell carcinoma was successful. Treatment with fully activated CD83+ dendritic cells was well tolerated with moderate fever as the only side effect. Potent immunological responses to KLH and, most importantly, against cell lysate could be measured in vitro after the vaccinations.

CONCLUSIONS

Our data demonstrate that a dendritic cell based vaccine can induce antigen specific immunity in patients with metastatic renal cell carcinoma. Dendritic cell based immunotherapy represents a feasible, well tolerated and promising new approach for the treatment of advanced renal cell carcinoma.

Systemic administration of interleukin 2 enhances the therapeutic efficacy of dendritic cell-based tumor vaccines

We have reported previously that murine bone marrow-derived dendritic cells (DC) pulsed with whole tumor lysates can mediate potent antitumor immune responses both in vitro and in vivo. Because successful therapy was dependent on host immune T cells, we have now evaluated whether the systemic administration of the T cell stimulatory/growth promoting cytokine interleukin-2 (IL-2) could enhance tumor lysate-pulsed DC-based immunizations to further promote protective immunity toward, and therapeutic rejection of, syngeneic murine tumors. In three separate approaches using a weakly immunogenic sarcoma (MCA-207), the systemic administration of nontoxic doses of recombinant IL-2 (20,000 and 40,000 IU/dose) was capable of mediating significant increases in the potency of DC-based immunizations. IL-2 could augment the efficacy of tumor lysate-pulsed DC to induce protective immunity to lethal tumor challenge as well as enhance splenic cytotoxic T lymphocyte activity and interferon-gamma production in these treated mice. Moreover, treatment with the combination of tumor lysate-pulsed DC and IL-2 could also mediate regressions of established pulmonary 3-day micrometastases and 7-day macrometastases as well as established 14- and 28-day s.c. tumors, leading to either significant cure rates or prolongation in overall survival. Collectively, these findings show that nontoxic doses of recombinant IL-2 can potentiate the antitumor effects of tumor lysate-pulsed DC in vivo and provide preclinical rationale for the use of IL-2 in DC-based vaccine strategies in patients with advanced cancer.

Cancer vaccines

It has been more than 100 years since the first reported attempts to activate a patient's immune system to eradicate developing cancers. Although a few of the subsequent vaccine studies demonstrated clinically significant treatment effects, active immunotherapy has not yet become an established cancer treatment modality. Two recent advances have allowed the design of more specific cancer vaccine approaches: improved molecular biology techniques and a greater understanding of the mechanisms involved in the activation of T cells. These advances have resulted in improved systemic antitumor immune responses in animal models. Because most tumor antigens recognized by T cells are still not known, the tumor cell itself is the best source of immunizing antigens. For this reason, most vaccine approaches currently being tested in the clinics use whole cancer cells that have been genetically modified to express genes that are now known to be critical mediators of immune system activation. In the future, the molecular definition of tumor-specific antigens that are recognized by activated T cells will allow the development of targeted antigen-specific vaccines for the treatment of patients with cancer.

Recombinant adenovirus is an efficient and non-perturbing genetic vector for human dendritic cells

Recombinant adenoviral vectors have promise for human gene therapy because of efficient transgene expression in nondividing primary cell types. Dendritic cells (DC) have potential as adjuvants for immune therapy, since they are specialized to capture antigens to form MHC-peptide complexes, migrate to T cell areas in the lymph node, and activate T cells including CD4+ helpers and CD8+ cytotoxic T lymphocytes (CTL). We show that several current chemical and physical transfection methods allow < 2 % of DC to express reporter genes but that recombinant adenoviruses, encoding the reporter genes green fluorescent protein and LacZ, efficiently transfect monocyte-derived human DC. Immature DC, generated with IL-4 and GM-CSF, are transfected to 95% efficiency, while mature DC show reduced transfection (50%) and gene expression. Adenovirus-transfected, immature DC exhibit several critical functions. The DC can differentiate in the presence of lipopolysaccharide or a monocyte-conditioned medium to express the surface markers of mature, T cell stimulatory DC including CD25, CD83, and high levels of CD86 and HLA-DR. Transfected DC can also secrete high levels of IL-12 and are potent inducers of T cell growth. Transgene expression in DC is stable for at least 6 days in the presence of the DC survival factor, TRANCE. Therefore adenoviral infection does not perturb the maturation and function of DC. The efficiency of adenoviral-mediated gene transfer prompts the evaluation of this vector in studies of DC biology, including the expression of antigens for active immune therapy.

Dendritic cells: development, function and potential use for cancer immunotherapy

Dendritic cells (DC) are potent antigen presenting cells that are essential for the initiation of primary immune responses. They richly express MHC, costimulatory and adhesion molecules necessary for the stimulation of naive T cell populations. Dendritic cells are located at sites of antigen capture where they demonstrate phagocytic capacity and subsequently migrate to lymphatic areas for antigen presentation. Their phenotypic and functional characteristics are intimately linked to their stage of maturation. The hematopoietic development of dendritic cells is distinct and may follow several precursor pathways some closely linked to monocytes. Generation of large numbers of cells for potential clinical use has recently been accomplished through the in vitro culturing of progenitors with cytokines. The use of dendritic cell vaccines for cancer immunotherapy has emerged as an exciting new focus of investigation. Various strategies have been adopted to introduce tumor antigens into dendritic cells so that they may be more effectively presented to T cells in the context of costimulation. Animal models demonstrate that dendritic cell tumor vaccines reverse T-cell anergy and result in subsequent tumor rejection. Incorporating the expanding knowledge of dendritic cell biology into vaccine design is essential for the generation of effective immunotherapy for cancer patients.

Transforming Growth Factor-β1 Polarizes Murine Hematopoietic Progenitor Cells to Generate Langerhans Cell-Like Dendritic Cells Through a Monocyte/Macrophage Differentiation Pathway

We have recently demonstrated that CD11b−/dullCD11c+ and CD11b+hiCD11c+ dendritic cell (DC) precursor subsets represent two distinct DC differentiation pathways from murine bone marrow lineage-phenotype negative (Lin−)c-kit+ hematopoietic progenitor cells (HPCs) stimulated with granulocyte-macrophage colony-stimulating factor (GM-CSF) + stem cell factor (SCF) + tumor necrosis factor  (TNF). We show here that transforming growth factor-β1 (TGF-β1) significantly inhibits the generation of these CD11b−/dullCD11c+ and CD11b+hiCD11c+ DC precursors. Phenotypically, this inhibitory effect was accompanied by markedly suppressed expression of Ia and CD86 antigens as well as major histocompatibility complex (MHC) class II transactivator (CIITA) and CC-chemokine receptor 7 (CCR7) mRNAs in Lin−c-kit+ HPC cultures stimulated with GM-CSF + SCF + TNF at day 6. TGF-β1 could also suppress mature DC differentiation from CD11b+hiCD11c+ DC precursors, but not the differentiation from CD11b−/dullCD11c+ DC precursors. In the absence of TNF, TGF-β1 markedly suppressed the expression of CIITA and CCR7 mRNAs in GM-CSF + SCF-stimulated Lin−c-kit+ HPCs at either day 6 or day 12 and induced the differentiation solely into monocytes/macrophages as evident in morphology, active phagocytic, and endocytic activities. These cells expressed high levels of F4/80 and E-cadherin antigens, but low or undetectable levels of Ia, CD86, and CD40 molecules. However, upon the stimulation with TNF + GM-CSF, these cells could further differentiate into mature DCs expressing high levels of Ia and E-cadherin, characteristics for Langerhans cells (LCs), and gained the capacity of enhancing allogenic MLR. Taken together, all of these findings suggest that TGF-β1 polarizes murine HPCs to generate LC-like DCs through a monocyte/macrophage differentiation pathway.

Transforming Growth Factor-β1 Polarizes Murine Hematopoietic Progenitor Cells to Generate Langerhans Cell-Like Dendritic Cells Through a Monocyte/Macrophage Differentiation Pathway

We have recently demonstrated that CD11b−/dullCD11c+ and CD11b+hiCD11c+ dendritic cell (DC) precursor subsets represent two distinct DC differentiation pathways from murine bone marrow lineage-phenotype negative (Lin−)c-kit+ hematopoietic progenitor cells (HPCs) stimulated with granulocyte-macrophage colony-stimulating factor (GM-CSF) + stem cell factor (SCF) + tumor necrosis factor  (TNF). We show here that transforming growth factor-β1 (TGF-β1) significantly inhibits the generation of these CD11b−/dullCD11c+ and CD11b+hiCD11c+ DC precursors. Phenotypically, this inhibitory effect was accompanied by markedly suppressed expression of Ia and CD86 antigens as well as major histocompatibility complex (MHC) class II transactivator (CIITA) and CC-chemokine receptor 7 (CCR7) mRNAs in Lin−c-kit+ HPC cultures stimulated with GM-CSF + SCF + TNF at day 6. TGF-β1 could also suppress mature DC differentiation from CD11b+hiCD11c+ DC precursors, but not the differentiation from CD11b−/dullCD11c+ DC precursors. In the absence of TNF, TGF-β1 markedly suppressed the expression of CIITA and CCR7 mRNAs in GM-CSF + SCF-stimulated Lin−c-kit+ HPCs at either day 6 or day 12 and induced the differentiation solely into monocytes/macrophages as evident in morphology, active phagocytic, and endocytic activities. These cells expressed high levels of F4/80 and E-cadherin antigens, but low or undetectable levels of Ia, CD86, and CD40 molecules. However, upon the stimulation with TNF + GM-CSF, these cells could further differentiate into mature DCs expressing high levels of Ia and E-cadherin, characteristics for Langerhans cells (LCs), and gained the capacity of enhancing allogenic MLR. Taken together, all of these findings suggest that TGF-β1 polarizes murine HPCs to generate LC-like DCs through a monocyte/macrophage differentiation pathway.

Review: dendritic cell immunotherapy for melanoma

Melanoma is a particularly aggressive malignant tumour of the skin that is influenced by genetic, environmental and physiological elements. Since current therapy for melanoma is limited and associated with high toxicity and side effects, development of alternative approaches is imperative. The importance of dendritic cells (DCs) in immunity against tumours is now well established. DC immunotherapy for melanoma is possible but must be considered in terms of effectiveness and clinical viability. The source of DCs to be used in adoptive therapy as well as the nature and method of delivery of the priming antigen are important factors. The most suitable DC appears to be cells derived by culture from hemopoietic progenitor cells (HPC) in bone marrow or DC progenitors in peripheral blood. Generation of an effective anti-tumour immune response will be dependent upon the presentation of multiple melanoma-specific antigens by both major histocompatibility complex (MHC) class I and class II molecules and stimulation of both tumour-specific cytotoxic T lymphocytes (Tc) and T helper type 1 (Thl) cells. Different techniques for delivery of the priming antigen offer different advantages. DCs can be pulsed with peptide, protein or tumour cell lysate, transfected with viral vectors or naked nucleic acid and tumour/DC hybridomas can also be generated. Repeated antigen administration into neighbouring lymph nodes appears to be the most effective method for promoting a systemic anti-tumour response. Adjuvant therapies can also enhance immune responses and lead to total tumour clearance. The importance of DC immunotherapy in clinically different stages of disease will also be an important consideration.

Prolonged neoadjuvant treatment in locally advanced tumours: a novel concept based on biological considerations

BACKGROUND

Neoadjuvant chemotherapy is increasingly applied in patients with locally advanced cancers of many tumour types. Usually three cycles of chemotherapy are administered to reduce the tumour size prior to local therapy, and another three cycles thereafter. The chemotherapy certainly contributes to the improved outcome of this approach. However, biological factors within the primary tumour have been neglected, while they might also contribute to the eradication of micrometastases. We believe that the neoadjuvant strategy can be improved by optimally exploiting certain biological factors inherent to the primary tumour. In a group of patients with locally advanced breast cancer (LABC) we studied this concept. Recently we described the clinical results of this phase II study in patients with LABC treated with neoadjuvant chemotherapy plus granulocyte-macrophage colony-stimulating factor (GM-CSF). A remarkable good response and survival was seen. In contrast to other studies we applied six cycles of neoadjuvant treatment in stead of a sandwich approach consisting of three cycles before and three cycles after local therapy, leaving the primary tumour and draining lymph nodes in situ for a prolonged period. In addition, GM-CSF was administered as a haematopoietic growth factor in stead of granulocyte colony-stimulating factor (G-CSF) as GM-CSF has also immuno-stimulating properties. Our findings definitely warrant further exploration of prolonged neoadjuvant systemic treatment in combination with GM-CSF in other high risk primary tumours.

HYPOTHESES

The promising results of our study may be attributable to two potential biological phenomena. Firstly, the conservation of the tumour and its draining lymph nodes may prove to be an essential part of this approach, with particular emphasis on the activation of tumour specific cytotoxic T cells. Secondly, circulating angiogenesis inhibitors originating from the primary tumour may enhance the effect of chemotherapy on micrometastases.

Cancer vaccines: novel approaches and new promise

Cancer vaccines are a promising tool in the hands of the clinical oncologist. We have summarized the most recent findings and achievements in this exciting field. Tumor-associated antigens, as a basis for the new cancer vaccines, are reviewed. We emphasize novel approaches for the design of safe and more effective vaccines for cancer. We also discuss the possible clinical applications and the future prospects for vaccine development.

High level of retrovirus-mediated gene transfer into dendritic cells derived from cord blood and mobilized peripheral blood CD34+ cells

Dendritic cells (DCs), the most potent antigen-presenting cells, can be generated from CD34+ hematopoietic stem cells and used for generating therapeutic immune responses. To develop immunotherapy protocols based on genetically modified DCs, we have investigated the conditions for high-level transduction of a large amount of CD34+-derived DCs. Thus, we have used an efficient and clinically applicable protocol for the retroviral transduction of cord blood (CB) or mobilized peripheral blood (MPB) CD34+ cells based on infection with gibbon ape leukemia virus (GALV)-pseudotyped retroviral vectors carrying the nls-LacZ reporter gene. Infected cells have been subsequently cultured under conditions allowing their dendritic differentiation. The results show that using a growth factor combination including granulocyte-macrophage colony-stimulating factor plus tumor necrosis factor alpha plus interleukin 4 plus stem cell factor plus Flt3 ligand, more than 70% of DCs derived from CB or MPB CD34+ cells can be transduced. Semiquantitative PCR indicates that at least two proviral copies per cell were detected. Transduced DCs retain normal immunophenotype and potent T cell stimulatory capacity. Finally, by using a semisolid methylcellulose assay for dendritic progenitors (CFU-DCs), we show that more than 90% of CFU-DCs can be transduced. Such a highly efficient retrovirus-mediated gene transfer into CD34+-derived DCs makes it possible to envision the use of this methodology in clinical trials.

Tumor regressions observed in patients with metastatic melanoma treated with an antigenic peptide encoded by gene MAGE-3 and presented by HLA-A1

Thirty-nine tumor-bearing patients with metastatic melanoma were treated with 3 subcutaneous injections of the MAGE-3.A1 peptide at monthly intervals. No significant toxicity was observed. Of the 25 patients who received the complete treatment, 7 displayed significant tumor regressions. All but one of these regressions involved cutaneous metastases. Three regressions were complete and 2 of these led to a disease-free state, which persisted for more than 2 years after the beginning of treatment. No evidence for a cytolytic T lymphocyte (CTL) response was found in the blood of the 4 patients who were analyzed, including 2 who displayed complete tumor regression. Our results suggest that injection of the MAGE-3.A1 peptide induced tumor regression in a significant number of the patients, even though no massive CTL response was produced.

Expression of the SART-1 tumor rejection antigen in breast cancer

We investigated in breast cancers the expression of the SART-1 gene encoding tumor rejection antigens. SART-1 mRNA was expressed in all of the samples tested. The SART-1(800) antigen was detectable in 20 of 50 (40%) breast cancer tissues and all breast cancer cell lines tested, but not in normal breast tissues. The SART-1(800)+ breast cancer cells transfected with HLA-A2601 or HLA-A2402 cDNA were recognized by the HLA-A26-restricted and SART-1-specific cytotoxic T lymphocytes (CTLs) or the HLA-A24-restricted and SART-1-specific CTLs, respectively. Among the 20 SART-1(800)+ tumors, 9 or 8 tumors expressed estrogen receptor or progesterone receptor, respectively. Therefore, the patients with HLA-A26 or -A24 haplotype might be appropriate candidates for specific immunotherapy with the SART-1 peptides independently or in combination with hormone therapy.

Dendritic cells: a link between innate and adaptive immunity

Dendritic cells (DC) constitute a unique system of cells able to induce primary immune responses. As a component of the innate immune system, DC organize and transfer information from the outside world to the cells of the adaptive immune system. DC can induce such contrasting states as active immune responsiveness or immunological tolerance. Recent years have brought a wealth of information regarding DC biology and pathophysiology, that shows the complexity of this cell system. Although our understanding of DC biology is still in its infancy, we are now in a position to use DC-based immunotherapy protocols to treat cancer and infectious diseases.

Why are dendritic cells central to cancer immunotherapy?

Dendritic cell (DC)-based immunotherapy is rapidly emerging as a viable alternative to radiation or chemotherapy in the treatment of cancer. The resurgence of interest in cancer immunotherapy reflects the promising results that have been obtained in both animal models and early clinical trials with the DC-based approach. Here I suggest that this optimism is justified because the efficient capture and presentation of antigens by DCs is central to the induction of an immune response. I argue that the mechanism by which DCs capture antigen suggests that the immune system might actually be 'blind' to tumours, thereby challenging the theory of immune surveillance.

Antitumour immune response and cancer vaccination: the critical role of dendritic cells

Increasing the capacity of the immune system to mediate tumour regression has been a major goal in tumour immunology. Progress towards this goal has been recently aided by the identification of immunogenic cancer antigens and by a better understanding of the mechanisms of T-cell immune response and tumour escape. A rare antigen-presenting cell--the dendritic cell (DC)--appears to be the key to these mechanisms. The possibility of generating these cells in vitro from blood precursors has initiated a new era in cancer immunotherapy. Using DC as a cancer vaccine adjuvant has led to reports of measurable immune responses, and, in a few cases, to complete disease responses in patients with B-cell lymphoma and melanoma.

Accessing Epstein-Barr virus-specific T-cell memory with peptide-loaded dendritic cells

The conventional means of studying Epstein-Barr virus (EBV)-induced cytotoxic T-lymphocyte (CTL) memory, by in vitro stimulation with the latently infected autologous lymphoblastoid cell line (LCL), has important limitations. First, it gives no information on memory to lytic cycle antigens; second, it preferentially amplifies the dominant components of latent antigen-specific memory at the expense of key subdominant reactivities. Here we describe an alternative approach, based on in vitro stimulation with epitope peptide-loaded dendritic cells (DCs), which allows one to probe the CTL repertoire for any individual reactivity of choice; this method proved significantly more efficient than stimulation with peptide alone. Using this approach we first show that reactivities to the immunodominant and subdominant lytic cycle epitopes identified by T cells during primary EBV infection are regularly detectable in the CTL memory of virus carriers; this implies that in such carriers chronic virus replication remains under direct T-cell control. We further show that subdominant latent cycle reactivities to epitopes in the latent membrane protein LMP2, though rarely undetectable in LCL-stimulated populations, can be reactivated by DC stimulation and selectively expanded as polyclonal CTL lines; the adoptive transfer of such preparations may be of value in targeting certain EBV-positive malignancies.

Identification of New Melanoma Epitopes on Melanosomal Proteins Recognized by Tumor Infiltrating T Lymphocytes Restricted by HLA-A1, -A2, and -A3 Alleles

To isolate melanoma Ags recognized by T cells, cDNA libraries made from melanoma cell lines were screened with four CTLs derived from tumor infiltrating lymphocytes (TIL) that were able to recognize melanoma cells in a HLA-A1, -A2, or -A3 restricted manner. Although cDNAs encoding the previously identified melanoma Ags, tyrosinase and gp100, were isolated, these TIL were found to recognize previously unidentified peptides. An HLA-A1-restricted CTL, TIL1388, was found to recognize a tyrosinase peptide (SSDYVIPIGTY), and an HLA-A3-restricted CTL, TIL1351, recognized a gp100 peptide (LIYRRRLMK). CTL clones isolated from the HLA-A2-restricted TIL1383 recognized a gp100 peptide (RLMKQDFSV). HLA-A2-restricted CTL, TIL1200, recognized a gp100 peptide (RLPRIFCSC). Replacement of either cysteine residue with α-amino butyric acid in the gp100 peptide, RLPRIFCSC, enhanced CTL recognition, suggesting that the peptide epitope naturally presented on the tumor cell surface may contain reduced cysteine residues. Oxidation of these cysteines might have occurred during the course of the synthesis or pulsing of the peptide in culture. These modifications may have important implications for the development of efficient peptide-based vaccines. These newly identified peptide epitopes can extend the ability to perform immunotherapy using synthetic peptides to a broader population of patients, especially those expressing HLA-A1 or HLA-A3 for whom only a few melanoma epitopes have previously been identified.

GD1alpha-replica peptides functionally mimic GD1alpha, an adhesion molecule of metastatic tumor cells, and suppress the tumor metastasis

A novel peptide technology to produce mimicking peptides of carbohydrate moiety (which we propose to name glyco-replica peptides) is a useful tool to elucidate the functions of glycoconjugate. Carbohydrate moiety of ganglioside GD1alpha functions as a molecule involved in the adhesion between murine highly metastatic lymphoma RAW117-H10 cells and hepatic sinusoidal endothelial (HSE) cells. To prepare peptides which mimic the carbohydrate structure of GD1alpha, phage clones expressing peptides which bound to a monoclonal antibody against GD1alpha (KA17) were isolated from a phage-displayed random peptide library. Four phage clones having affinity to the monoclonal antibody KA17 were isolated, and these clones showed inhibitory effect on the binding of KA17 to GD1alpha. The amino acid sequences of the displayed pentadecamers were determined, and one of the phages displaying sequence WHWRHRIPLQLAAGR bound to HSE cells directly and showed the highest inhibitory effect on the adhesion between RAW117-H10 cells and HSE cells. The synthesized peptides having the same sequences to the displayed 15mers in the four isolated phage clones also showed the inhibitory effect on the adhesion of RAW117-H10 cells to HSE cells, and, again, the WHWRHRIPLQLAAGR peptide showed the highest inhibitory effect. Furthermore, intravenous injection of the peptide brought almost complete inhibition of the metastasis of RAW117-H10 cells to lung and spleen, and about 50% inhibition of the liver metastasis. These results indicate that GD1alpha plays an important role for metastasis of RAW117-H10 cells, and the peptides obtained by the present procedure are able to mimic the functional role of the glycoconjugate.

The shared tumor-specific antigen encoded by mouse gene P1A is a target not only for cytolytic T lymphocytes but also for tumor rejection

A number of human tumor antigens have been characterized recently using cytolytic T lymphocytes (CTL) as screening tools. Some of them are encoded by MAGE-type genes, which are silent in normal tissues except in male germ cells, but are activated in a variety of tumors. These tumor-specific shared antigens appear to be promising targets for cancer immunotherapy. However, the choice of these antigens as targets has been questioned because of the lack of direct evidence that in vivo responses against such antigens can lead to tumor rejection. The antigen encoded by the mouse gene P1A represents the only available animal model system for MAGE-type tumor antigens. We show here that mice immunized by injection of L1210 leukemia cells expressing P1A and B7-1 (L1210.P1A.B7-1) are efficiently protected against a challenge with a lethal dose of mastocytoma P815 tumor cells, which express P1A. Mice immunized with L1210 cells expressing B7-1 but not P1A were not protected. Furthermore, we observed that P1A-transgenic mice, which are tolerant to P1A, were not protected after immunization with L1210.P1A.B7-1. These results demonstrate that the immune response to P1A is the major component of the tumor rejection response observed in normal mice, and support the use of tumor-specific shared antigens as targets for the immunotherapy of human cancer.

A novel dendritic cell population in human blood: one-step immunomagnetic isolation by a specific mAb (M-DC8) and in vitro priming of cytotoxic T lymphocytes

Originating from a common progenitor cell, dendritic cells (DC) appear to develop along early branched pathways into various yet ill-defined subpopulations residing at various sites throughout the body where they capture and present antigen in the most professional fashion. Here we give evidence for a unique subpopulation of human DC circulating in blood that account for 0.5-1% of blood leukocytes only, their most specific characteristic being the expression of a cell surface protein recognized by a novel monoclonal antibody (M-DC8) which enables their isolation by a one-step immunomagnetic procedure. The isolated cells (> 97% pure) present morphologically as typical dendritic cells. They express the Fc(gamma)RIII (CD16), so far not found on DC, and avidly phagocytose latex beads as well as opsonized erythrocytes. These cells not only present antigens efficiently to naive T cells but also induce purified CD8+ T cells to become alloantigen-specific cytotoxic cells. Furthermore, when loaded with a tyrosinase-derived peptide they stimulate T cells from normal donors and melanoma patients to exhibit MHC-restricted specific cytotoxicity against melanoma cells.

Expression of the SART-1 antigens in uterine cancers

We recently reported that the SART-1 gene, encoding the SART-1(259) tumor antigen which is recognized by HLA-A26-restricted cytotoxic T lymphocytes (CTLs), is expressed in the cytosol of squamous cell carcinomas and adenocarcinomas. The present study deals with the expression of SART-1(259) and SART-1(800) antigens in uterine cancers. The SART-1(259) antigen was detected in the cytosol fraction of 4 of 8 uterine cancer cell lines, 24 of 74 (32%) uterine cancer tissues, 0 of 7 uterine myomas, and 0 of 5 non-tumorous uterine tissues. The SART-1(800) antigen was expressed in the nuclear fraction of all the uterine cancer cell lines, 41 of 74 (55%) uterine cancer tissues, 0 of 7 myomas, and 3 of 5 non-tumorous uterine tissues. The SART-1(259)+ uterine cancer cells were recognized by HLA-A24 restricted and SART-1 specific CTLs. Therefore, SART-1(259) antigen could be an appropriate vaccine candidate for a relatively large number of uterine cancer patients.

Generation of Melanoma-Specific Cytotoxic T Lymphocytes by Dendritic Cells Transduced with a MART-1 Adenovirus

Dendritic cells (DC) are potent stimulators of primary T cell responses. In this study, we demonstrate that DC, genetically engineered to express the MART-1/Melan-A (MART-1) tumor-associated Ag, express MART-1 mRNA and protein, correctly process and present the HLA-A2.1-restricted immunodominant MART-1 peptide (MART-127–35), and serve as potent stimulators of MART-1-specific CTL in vitro. A replication-defective E1-deleted adenovirus (AdV) was constructed that expresses MART-1 (AdVMART1). Transduced DC produce full length MART-1 mRNA as well as MART-1 protein. AdVMART1 does not significantly down-regulate cell surface class I expression despite having an intact E3 region. Transduction of an HLA-A2-positive/MART-1-negative cell line with AdVMART1 renders these cells sensitive to lysis by CTL specific for the MART-127–35 immunodominant peptide. In addition, DC transduced with AdVMART1 stimulated MART-127–35-specific tumor-infiltrating lymphocytes to synthesize IFN-γ. Finally, AdVMART1-transduced DC were able to generate MART-127–35 peptide-specific, class I-restricted CTL in PBL cultures from normal donors. This study supports the use of tumor Ag-engineered DC in genetic immunotherapy.

The role of CD4+ T cell responses in antitumor immunity

While most of the focus in cancer immunology is on CD8+ cytotoxic T lymphocyte responses, recent evidence indicates that CD4+ T cells are an equally critical component of the antitumor immune response. Successful immunity to cancer will therefore require activation of tumor-specific CD4+ T cells. Tumor antigens recognized by CD4+ T cells that are restricted by MHC class II are beginning to be defined in both murine and human tumors. These will provide the basis for new generations of antigen-specific tumor vaccines.