Adoptive transfer of T cells modified with a humanized chimeric receptor gene inhibits growth of Lewis-Y-expressing tumors in mice

In this study, human T cells were provided with a reactivity against the Lewis-Y (Le(Y)) carbohydrate antigen, which is overexpressed on 70% of epithelial-derived tumors, but not normally recognized by T cells. Antitumor reactivity was achieved by transduction of T cells with a gene encoding a cell-surface chimeric receptor composed of single-chain anti-Le(Y) antibody linked to an enhanced cytoplasmic signaling domain made up of CD28 and CD3-zeta. Importantly, the single-chain antibody was humanized to try to reduce potential problems of human anti-mouse antibody responses in patients receiving chimeric receptor-modified T cells in future clinical trials. T cells expressing the chimeric receptor were demonstrated to secrete cytokines and proliferate in response to receptor ligation and lysed Le(Y+) tumors in vitro. Another aspect of this study was the finding that no activity was observed against normal tissue, as represented by autologous neutrophils that express low levels of Le(Y). Significantly, systemic delivery of anti-Le(Y) T cells dramatically inhibited established s.c. human ovarian OVCAR-3 tumors (a recognized difficult model to treat) in mice. Finally, we demonstrated that anti-Le(Y) T cells preferentially expanded or accumulated in the tumor compared with control empty vector T cells, thereby providing mechanistic insight into the specific antitumor response. This study supports the use of humanized gene-modified T cells as a potential therapy for Le(Y+) malignancies.

Virulizin, a novel immunotherapy agent, activates NK cells through induction of IL-12 expression in macrophages

Virulizin, a novel biological response modifier, has demonstrated significant antitumor efficacy in a variety of human tumor xenograft models including melanoma, pancreatic cancer, breast cancer, ovarian cancer and prostate cancer. The significant role of macrophages and NK (Natural killer) cells was implicated in the antitumor mechanism of Virulizin where expansion as well as increased activity of macrophages and NK cells were observed in mice treated with Virulizin. Depletion of macrophages compromised Virulizin-induced NK1.1+ cell infiltration into xenografted tumors and was accompanied by reduced antitumor efficacy. In the present study, involvement of macrophages in NK cell activation was investigated further. We found that depletion of NK cells in CD-1 nude mice by anti-ASGM1 antibody significantly compromised the antitumor activity of Virulizin. Cytotoxicity of NK cells isolated from Virulizin-treated mice was enhanced against NK-sensitive YAC-1 cells and C8161 human melanoma cells, but not against NK-insensitive P815 cells. An increased level of IL-12beta was observed in the serum of mice treated with Virulizin. IL-12 mRNA and protein levels were also increased in peritoneal macrophages isolated from Virulizin-treated mice. Moreover, Virulizin-induced cytotoxic activity of NK cells isolated from the spleen was abolished when an IL-12 neutralizing antibody was co-administered. In addition, depletion of macrophages in mice significantly impaired Virulizin-induced NK cell cytotoxicty. Taken together, the results suggest that Virulizin induces macrophage IL-12 production, which in turn stimulates NK cell-mediated antitumor activity.

Low-dose IL-2 induces cytokine cascade, eosinophilia, and a transient Th2 shift in melanoma patients

PURPOSE

To assess changes in serum cytokine levels in patients treated concomitantly with or without systemic low-dose IL-2. Vaccination targeted CTL responses to peptide antigens, and IL-2 was coadministered to expand activated CTL. Paradoxically, CTL responses were diminished in patients after 2 weeks of IL-2. We hypothesized that changes in the cytokine milieu may have contributed to this result.

EXPERIMENTAL DESIGN

Serum samples were studied from 37 patients enrolled in two clinical trials of a melanoma peptide vaccine administered with or without low-dose IL-2 therapy. Twenty-two patients enrolled in the MEL36 trial received six weekly vaccinations with the four-peptide mixture and were randomized to receive subcutaneous IL-2 (3 x 10(6) IU/m2/day) daily for 6 weeks beginning either at week 1 (upfront group) or at week 4 (delayed group) of vaccine therapy. Fifteen patients on the MEL39 trial were treated with the same vaccine without concurrent IL-2 administration.

RESULTS

Circulating levels of IL-5 peaked 1 week after starting IL-2, followed 2 weeks later by a marked eosinophilia, correlating in magnitude with peak IL-5 serum levels. Levels of IFNgamma, GM-CSF, IL-4, IL-10, and IL-12 had no observed relationship to IL-2 administration. At the time of the IL-5 serum peak, PBL responses to mitogen suggested a transient shift to Th2-dominance.

CONCLUSIONS

Low-dose IL-2 appears to have induced a transient Th2-dominant secondary cytokine cascade at the time of vaccination, for which eosinophilia is a surrogate marker. For future vaccine therapies targeting cytotoxic T-cell responses, delaying IL-2 until after initiation of immune responses may be more effective.

Lung cancer immunotherapy

Recent insights into anti-tumor immunotherapy have led to a wave of clinical trials involving immunotherapy for lung cancer. Vaccines have evolved from nonspecific immune stimulants, like Bacillus Calmette-Guerin (BCG), to much more specific and potent strategies, some of which generate active immune responses against tumor-associated antigens. Understanding the mechanisms of anti-tumor immunity and identifying target antigens will likely improve these therapeutic strategies and provide them with a niche in the future of lung cancer therapy.

Induction of Th1-type immunity and tumor protection with a prostate-specific antigen DNA vaccine

Prostate specific antigen (PSA) is a serum marker that is widely used in the detection and monitoring of prostate cancer. Though PSA is a self-antigen, T cell responses to PSA epitopes have been detected in healthy men and prostate cancer patients, suggesting it may be used as a target for active immunotherapy of prostate cancer. A PSA DNA vaccine (pPSA) was evaluated in mice and monkeys for its ability to induce antigen-specific immune responses. Mice immunized intradermally with pPSA demonstrated strong PSA-specific humoral and cellular immunity. The anti-PSA immune responses were skewed toward Th1, as shown by high IFNgamma and IL-2 production. The immune response was sufficient to protect mice from challenge with PSA-expressing tumor cells. Tumor protection was durable in the absence of additional vaccination, as demonstrated by protection of vaccinated mice from tumor rechallenge. Furthermore, pPSA vaccination induced PSA-specific antibody titers in male cynomolgus monkeys, which express a closely related PSA gene. These results demonstrate that vaccination with pPSA may be able to break tolerance and can induce an immune response that mediates tumor protection.

Expression of complement protein C5a in a murine mammary cancer model: tumor regression by interference with the cell cycle

The C5a anaphylatoxin protein plays a central role in inflammation associated with complement activation. This protein is commonly regarded as one of the most potent inducers of the inflammatory response and a C5a peptide agonist was used as a molecular adjuvant. However, the full length C5a protein has not been tested as a potential tumor therapy. In this report, we describe the creation of a mini-gene construct that directs C5a expression to any cell of interest. Functional expression could be demonstrated in the murine mammary sarcoma, EMT6. When C5a expressing cells were injected into syngeneic mice, most C5a-expressing clones had significantly reduced tumor growth. Further characterization of a clone expressing low levels of C5a demonstrated that one-third of mice injected with this line had complete tumor regression. The mice whose tumors regressed were immune to subsequent challenge with unmodified EMT6 cells, suggesting that a component of the innate immune response can be used to augment adaptive immunity. Cellular analyses demonstrated that a significant difference in actual tumor cell number could be detected as early as day 10. A block in cell cycle progression was evident at all time points and high levels of apoptosis were observed early in the regression event. These data demonstrate that the complement protein C5a can play a significant protective role in tumor immunity.

Immunostimulatory properties of human dendritic cells generated using IFN-beta associated either with IL-3 or GM-CSF

Despite limited clinical efficacy in large trials, dendritic cells (DC)-based immunization has yielded impressive responses in some patients. Key questions remain to be solved in order to optimize this therapeutic vaccine. Among them, the nature of the DC type used and its state of maturation are pivotal. Besides myeloid DC which are mostly used in clinical trials, a new DC type has been recently described resulting from the differentiation of monocytes in the presence of type I IFNs. In the present study, we analyze the features of type I IFNs DC generated in the presence of either IL-3 (IL-3-DC) or GM-CSF (GM-CSF-DC) and compare their capacity to respond to poly(I:C) and to subsequently trigger T-cell activation. The two DC types disclose a similar immunophenotype characterized by high levels of chemokines receptors, co-stimulatory and HLA molecules expression. After poly(I:C) maturation, both DC types display a marked upregulation of CD80, CD83 and CD86 and the same pattern of gene expression. In addition, poly(I:C) stimulated them to secrete IFN-alpha and IL-12p70. Both DC types elicit potent allogeneic reactions. Priming of autologous T cells by IL-3-DC or GM-CSF-DC pulsed with an HLA-A2 restricted melan-A derived peptide, lead to the expansion of peptide specific CTL secreting high amounts of IFN-gamma. We conclude that poly(I:C) matured IL-3-DC and GM-CSF-DC share similar phenotype and functional properties including the capacity to prime tumor-associated antigen specific CTL.

Selection of GM2, fucosyl GM1, globo H and polysialic acid as targets on small cell lung cancers for antibody mediated immunotherapy

Glycolipids GM2, GD2, GD3, fucosyl GM1, sialyl Lewis a (sLe(a)) and globo H, and polysialic acid on embryonal NCAM, are cell-surface antigens expressed on small cell lung cancer (SCLC) biopsy specimens. They are all candidates for inclusion in a polyvalent, antibody-inducing vaccine or for adoptive therapy with monoclonal antibodies (mAbs) against SCLC. To identify the minimum optimal combination of target antigens on SCLC and to confirm that antibodies against this combination might be able to mediate complement activation and lysis in the majority of cases, we tested ten SCLC cell lines with fluorescence activated cell sorter (FACS) and complement dependent cytotoxicity (CDC) assays using mAbs against these seven target antigens individually or pooled in different combinations. We find that (1) none of these mAbs demonstrated strong FACS reactivity with more than 6 of the 10 cell lines, (2) no mAb had strong CDC reactivity with more than 4 of the cell lines, (3) when the mAbs were pooled, nine cell lines were strongly positive by FACS and nine cell lines were strongly positive by CDC, and (4) mAbs against GM2, FucGM1, globo H and polysialic acid was the minimum optimal combination for inducing FACS reactivity. The addition of mAbs against sLe(a), GD2 and GD3 had no additional impact by FACS and only minimal additional impact in CDC assays. H345, the only cell line that had less than 30% CDC with the four mAb pool was strongly positive by FACS. To understand the lack of correlation between FACS and CDC in the case of H345, the ten cell lines were screened for expression of complement resistance factors CD55 and CD59. Three cell lines were strongly positive for CD55 and eight were strongly positive for CD59. Overall, no correlation was seen between expression of either of these factors on the ten cell lines and sensitivity to CDC. In the case of H345 however, complement resistance of H345 is demonstrated to be mediated primarily by CD59, and in the presence of mAb against CD59, the four mAb MEM-43 pool induced strong (94%) CDC. CD59 inhibits membrane attack complex formation but not activation of earlier complement components. Consequently, all ten cell lines are good targets for complement activation by the four antibody pool and for elimination by effector mechanisms including complement mediated inflammation and opsonization. These findings support our plan to develop a tetravalent vaccine against SCLC targeting GM2, fucosyl GM1, globo H and polysialic acid.

A two-year course of specific immunotherapy or of continuous antihistamine treatment reverse eosinophilic inflammation in severe persistent allergic rhinitis

Aim of the study was to evaluate the effect of a 2-year course of subcutaneous specific immunotherapy or continuous oral antihistamine treatment on the eosinophilic inflammation in nasal secretions of patients with severe persistent allergic rhinitis caused by house dust-mites. After informed consent, 31 rhinitis patients, sensitive to dust-mite antigens, were enrolled: 12 were randomly assigned to specific immunotherapy (group A), 11 to continuous oral antihistamine (cetirizine) treatment (group B), and 8 to an oral antihistamine (cetirizine) on demand (group C). Nasal scrapings were performed with a cotton-tipped swab and cells counted before and after 24 months of therapy. Intercellular adhesion molecule-1 and eosinophil cationic protein expression in cytological smears were assessed by immuno-histochemistry. All patients completed the study. The percentage of inflammatory cell types was comparable in the 3 groups at the beginning of the study. Eosinophils, identified as cells expressing eosinophil cationic protein, significantly decreased dropping to zero after 2 years of treatment in groups A and B, while no change was observed in group C. Expression of intercellular adhesion molecule-1 also decreased significantly in groups A and B, but not in group C. This decrease was associated with a significant reduction in epithelial shedding. In the 2-year period studied, specific subcutaneous immunotherapy and continuous oral antihistamine treatment were found to be effective in reducing eosinophilic infiltration and adhesion molecule expression in the nasal mucosa of patients with persistent allergic rhinitis. Furthermore, immunotherapy was more effective in controlling epithelial disruption while antihistamines appeared to be more active in controlling nasal inflammation. Both treatments induced a significant decrease in intercellular adhesion molecule-1 expression in epithelial cells and also a dramatic reduction of eosinophil cationic protein positive staining. These parameters can be considered useful means for controlling the state of persistent inflammation which is typical of persistent respiratory allergy. Nasal scraping was demonstrated to be a simple and safe procedure for monitoring some nasal inflammation parameters.

Targeted immunotherapy in acute myeloblastic leukemia: from animals to humans

Immunity against acute myeloid leukemia (AML) is demonstrated in humans by the graft-versus-leukemia effect in allogeneic hematopoietic stem cell transplantation. Specific leukemic antigens have progressively been discovered and circulating specific T lymphocytes against Wilms tumor antigen, proteinase peptide or fusion-proteins produced from aberrant oncogenic chromosomal translocations have been detected in leukemic patients. However, due to the fact that leukemic blasts develop various escape mechanisms, antileukemic specific immunity is not able to control leukemic cell proliferation. The aim of immunotherapy is to overcome tolerance and boost immunity to elicit an efficient immune response against leukemia. We review different immunotherapy strategies tested in preclinical animal models of AML and the human trials that spurred from encouraging results obtained in animal models, demonstrate the feasibility of immunotherapy in AML patients.

Effect of IL-2-Bax, a novel interleukin-2-receptor-targeted chimeric protein, on bleomycin lung injury

The role of lymphocytes in the pathogenesis of lung fibrosis is not clear, but the weight of the evidence supports a pro-fibrotic effect for lymphocytes. The high-affinity interleukin-2 receptor (haIL-2R) is expressed on activated, but not quiescent, T lymphocytes. This selective expression of haIL-2R provides the basis for therapeutic strategies that target IL-2R-expressing cells. We hypothesized that elimination of activated lymphocytes by IL-2R-targeted chimeric proteins might ameliorate lung fibrosis. We investigated the effects of IL-2-Bax, a novel apoptosis-inducing IL-2R-targeted chimeric protein, on bleomycin-induced lung injury in mice. Treatment groups included (i) a single intratracheal instillation of bleomycin and twice-daily intraperitoneal injections of IL-2-Bax; (ii) intratracheal bleomycin and intraperitoneal IL-2-PE66(4Glu), an older-generation chimeric protein; (iii) intratracheal bleomycin/intraperitoneal PBS; (iv) intratracheal saline/intraperitoneal PBS. Lung injury was evaluated 14 days after intratracheal instillation by cell count in bronchoalveolar lavage (BAL) fluid, semi-quantitative and quantitative histomorphological measurements and by biochemical analysis of lung hydroxyproline. Bleomycin induced a BAL lymphocytosis that was significantly attenuated by IL-2-Bax and IL-2-PE66(4Glu). However, morphometric parameters and lung hydroxyproline were unaffected by the chimeric proteins. These results show that IL-2-Bax reduces the lymphocytic infiltration of the lungs in response to bleomycin, but this effect is not accompanied by a decrease in lung fibrosis.

Lessons to be learned from primary renal cell carcinomas: novel tumor antigens and HLA ligands for immunotherapy

The lack of sufficient well-defined tumor-associated antigens is still a drawback on the way to a cytotoxic T-lymphocyte-based immunotherapy of renal cell carcinoma (RCC). We are trying to define a larger number of such targets by a combined approach involving HLA ligand characterization by mass spectrometry and gene expression profiling by oligonucleotide microarrays. Here, we present the results of a large-scale analysis of 13 RCC specimens. We were able to identify more than 700 peptides, mostly from self-proteins without any evident tumor association. However, some HLA ligands derived from previously known tumor antigens in RCC. In addition, gene expression profiling of tumors and a set of healthy tissues revealed novel candidate RCC-associated antigens. For several of them, we were able to characterize HLA ligands after extraction from the tumor tissue. Apart from universal RCC antigens, some proteins seem to be appropriate candidates in individual patients only. This underlines the advantage of a personalized therapeutic approach. Further analyses will contribute additional HLA ligands to this repertoire of universal as well as patient-individual tumor antigens.

Deglycosylation of anti-beta amyloid antibodies inhibits microglia activation in BV-2 cellular model

Immunotherapy has become a strategy for treatment of Alzheimer's disease, by inducing antibody response to amyloid-beta peptide (AbetaP) or by passive administration of anti-AbetaP antibodies. Clearance of amyloid plaques involves interaction of immunoglobulin Fc receptor (FcR)-expressing microglia and antibodyopsonized Abeta deposits, stimulating phagocytosis but may promote neuroinflammation. Carbohydrate moiety of Fc of the immunoglobulin G molecule plays a significant role in modulating binding to FcR and its effector functions. Here, we enzymatically removed Fc glycan from monoclonal antibody 196 raised against AbetaP Antigen binding ability and in vitro stability of deglycosylated antibody were unaffected by deglycosylation. Moreover, the deglycosylated antibody exhibits low affinity to FcR on microglial BV-2 cells and has limited ability to mediate microglial chemotaxis and antibodydependent cytotoxicity compared to native antibody. These data suggest that deglycosylation of anti-Abeta antibodies before in vivo administration might prevent microglial overactivation, thus reducing the risk of neuroinflammatory response during passive immunization.

Prolonged low dose IL-2 and thalidomide in progressive metastatic renal cell carcinoma with concurrent radiotherapy to bone and/or soft tissue metastasis: a phase II study

Metastatic renal cell cancer is one of the immuno-sensitive tumors. Apart from the immuno-modulating agents IFNalpha and IL-2, thalidomide has been reported to be effective in this type of cancer. However, bone metastases and bulky metastases, show limited response to immunotherapy, are often site of recurrent disease and are therefore often treated later with radiotherapy. In this phase II study, we evaluated toxicity and efficacy of the combination of continuous low dose (1 mIU/m2) s.c. IL-2 and thalidomide (200 mg once daily) in 22 patients with progressive metastatic renal cell cancer. In addition, 13 soft tissue lesions and two bone metastases in 13 patients were concurrently treated with fractionated radiotherapy. T cell number and activation in blood was measured by immunoflowcytometry. Nearly all patients developed grade 1-2 toxicity consisting of fatigue, sensory neuropathy, constipation and dizziness. Five patients had a grade 3-4 toxic event: four patients with deep venous thrombosis requiring anticoagulant therapy, and one patient who developed radiation myelopathy. On systemic response evaluation ten patients showed ongoing SD with a mean progression free survival of 9 months. One patient showed a PR (at an irradiated site). Regarding local response to irradiation, seven lesions showed a PR for a mean time period of 8.7 months, whereas seven were stable for 6 months. The radiation response of one lesion was not evaluable. Immunoflowcytometry showed an increase in number and activation of lymphocytes (mainly Natural Killer--NK-cells), which was absent or even decreased in irradiated patients. The combination of sc. low dose IL-2, thalidomide and radiotherapy is feasible, but relatively toxic and does not lead to higher responses at non-irradiated sites. The combination of immunotherapy and concurrent radiotherapy is effective at 60% of the relatively large evaluable sites. Progressive myelopathy developed in one patient, possibly due to radiotherapy in combination with thalidomide.

Immuno-gene therapy of melanoma by tumor antigen epitope modified IFN-gamma

Cytokine-based vaccines play a major part in tumor immuno-gene therapy. However, down-regulated antigen expression on tumor cells may diminish the immuno-potentiating aspects of cellular vaccines. In this study, we coexpressed a tumor antigen epitope with IFN-gamma in the same gene by replacing the IFN-gamma signal peptide with an antigen epitope-expressing signal peptide. We then investigated the effect of the antigen epitope-incorporated IFN-gamma on the immunotherapy of murine melanoma B16 tumors. Results showed that TRP-2 epitope-expressing IFN-gamma decreased B16 tumorigenicity and enhanced its immunogenicity after gene transfer. Protective immunity against wild type B16 tumors was induced by vaccination with IFN-gamma transiently gene-modified tumor cells. These data suggest that cellular vaccines engineered to express an antigen epitope within an immunostimulatory cytokine could potentiate the immunization effect.

Identification of a potential human telomerase reverse transcriptase-derived, HLA-A1-restricted cytotoxic T-lymphocyte epitope

The catalytic subunit of human telomerase reverse transcriptase (hTERT) is expressed in the majority of tumor cells of different histological origins as opposed to most normal somatic cells. This implicates hTERT as a widely expressed tumor-associated antigen and an attractive candidate for antigen-specific tumor immunotherapy. T lymphocytes specific for hTERT-derived epitopes have been isolated and shown reactive with hTERT-expressing tumor cells. To further increase the applicability of hTERT as a target antigen for immunotherapy, we set out to identify potential hTERT-derived, HLA-A1-restricted cytotoxic T-lymphocyte (CTL) epitopes. The "reverse immunology" approach, involving computer-assisted epitope prediction, in vitro CTL induction, and tetramer-guided CTL isolation, resulted in specific CTLs against hTERT-derived, HLA-A1-binding peptides. Intermediate- to low-avidity CTLs were induced against the hTERT325-333 peptide and recognized endogenously processed hTERT. Recognition of endogenous hTERT depended on an increase of hTERT expression above normal levels in tumor cells through hTERT transduction, most probably as a result of limited CTL avidity. The altered peptide ligand hTERT699T-707 was designed to increase HLA-A1-binding affinity of the hTERT699-707 peptide and was used to induce CTLs. However, these CTLs poorly cross-recognized native hTERT699-707 and failed to recognize endogenously processed hTERT. In conclusion, our study has identified the hTERT325-333 peptide as a potential hTERT-derived epitope that may prove useful for induction and monitoring of hTERT-specific, HLA-A1-restricted CTL responses.

A phase-II study of pegylated interferon alfa-2b for patients with metastatic renal cell carcinoma and removal of the primary tumor

Twenty-two patients with metastatic renal cell carcinoma and removal of the primary tumor were treated with subcutaneous pegylated interferon alfa-2b (PEG-Intron) to evaluate toxicity and efficacy. Start dose was 3.0 microg/kg/week, escalated to 6.0 microg/kg/week. After 2 months, therapy was extended in case of response or stable disease (SD) until progressive disease (PD) or relapse for a maximum of 2 years. National Cancer Institute common toxicity criteria (NCI-CTC) were monitored every 2-4 weeks. After 2 months, nine patients did not continue (8 PD, 1 SD with grade 4 CTC) and 13 extended treatment [three partial response (PR), 10 SD], of these, 11 progressed. One patient with PR developed a durable complete response later. Overall response rate was 13.6% (3/22). Median overall survival is 13 months (range 3-35 months). Dosage was escalated to 6 microg/kg/week in three patients. NCI-CTC grade 2 and 3 required dose attenuation in 12 patients during escalation, and reduction in 10 during the trial. Three patients discontinued because of grade 4 CTC (two fatigue, one hyperglycemia). Fatigue was the major dose-limiting toxicity. These results suggest an efficacy and toxicity of PEG-Intron comparable to standard interferon alfa-2b in patients with mRCC and removal of the primary tumor.

New developments in dendritic cell-based vaccinations: RNA translated into clinics

Dendritic cells (DCs) are the most powerful antigen-presenting cells that induce and maintain primary immune responses in vitro and in vivo. The development of protocols for the ex vivo generation of DCs provided a rationale for designing and developing DC-based vaccination studies for the treatment of infectious and malignant diseases. Recently, it was shown that DCs transfected with ribonucleic acid (RNA) coding for a tumour-associated antigen or whole tumour RNA are able to induce potent antigen and tumour-specific T-cell responses directed against multiple epitopes. The first RNA-transfected-DC-based clinical studies have shown that this form of vaccination is feasible and safe. In some cases, clinical responses were observed, but the preliminary data require further extensive investigations that should address the technical and biological problems of manipulating human DCs, as well as the development of standardised protocols and definitions of clinical settings.

Targeting novel antigens for prostate cancer treatment: focus on prostate-specific membrane antigen

Prostate-specific membrane antigen (PSMA) is a relatively omnipresent, but unique Type II dimeric transmembrane protein with a multiplicity of functions and has been shown to be a reasonable target for immunological approaches such as vaccines or more directed therapy with radioactively labelled monoclonal antibodies against PSMA. Given the abundance of various glycoprotein and carbohydrate antigens expressed on the surface of prostate cancer cells and cell lines, PSMA stands out as another 'self' antigen which is not only expressed on cancer cells, but on neovasculature. Although vaccines are varied in their design and target goal, recent technology has afforded researchers the opportunity to induce recruitment of multiple effector cell populations, cytokines and factors which can elicit both cellular and humoral responses. This review serves to present unique approaches in vaccine development which can induce immunological responsiveness with potential impact on disease progression and to introduce PSMA as a potential target for multimodality therapies.

Clinical trials of antitumor vaccination with an autologous tumor cell vaccine modified by virus infection: improvement of patient survival based on improved antitumor immune memory

For active specific immunotherapy of cancer patients, we designed the autologous virus-modified tumor cell vaccine ATV-NDV. The rationale of this vaccine is to link multiple tumor-associated antigens (TAAs) from individual patient-derived tumor cells with multiple danger signals (DS) derived from virus infection (dsRNA, HN, IFN-alpha). This allows activation of multiple innate immune responses (monocytes, dendritic cells, and NK cells) as well as adaptive immune responses (CD4 and CD8 memory T cells). Preexisting antitumor memory T cells from cancer patients could be activated by antitumor vaccination with ATV-NDV as seen by augmentation of antitumor memory delayed-type hypersensitivity (DTH) responses. In a variety of phase II vaccination studies, an optimal formulation of this vaccine could improve long-term survival beyond what is seen in conventional standard therapies. A new concept is presented which proposes that a certain threshold of antitumor immune memory plays an important role (1) in the control of residual tumor cells which remain after most therapies and (2) for long-term survival of treated cancer patients. This immune memory is T-cell based and most likely maintained by persisting TAAs from residual dormant tumor cells. Such immune memory was prominent in the bone marrow in animal tumor models as well as in cancer patients. Immunization with a tumor vaccine in which individual TAAs are combined with DS from virus infection appears to have a positive effect on antitumor immune memory and on patient survival.

Immunotherapy for superficial bladder cancer

The treatment of superficial bladder cancer requires adjuvant therapies besides transurethral resection because of a high recurrence rate after this standard treatment alone. Current adjuvant therapies involve intravesical chemotherapy for patients at low and intermediate risk for recurrence and progression, and intravesical bacillus Calmette-Guérin for patients at intermediate and high risk. However, these adjuvant therapies fail in a significant number of patients, dictating the need for new and improved adjuvant treatment modalities for superficial bladder cancer. Immunotherapy aiming at the modulation of the immune system of the patient is a promising alternative adjuvant. This review discusses the current status of the clinical development of various immunotherapy approaches for superficial bladder cancer, including passive immunotherapy, immune stimulants, immunogene therapy and cancer vaccination.

Tumor sensitivity to IFN-gamma is required for successful antigen-specific immunotherapy of a transplantable mouse tumor model for HPV-transformed tumors

PURPOSE

Many human tumors lose responsiveness to IFN-gamma, providing a possible mechanism for the tumor to avoid immune recognition and destruction. Here we investigate the importance of tumor responsiveness to IFN-gamma in the successful immunotherapy of TC1 tumors that were immortalized with human papillomavirus proteins E6 and E7.

METHODS

To investigate the role of IFN-gamma in vivo, we constructed a variant of TC1, TC1.mugR, that is unresponsive to IFN-gamma due to overexpression of a dominant negative IFN-gamma receptor.

RESULTS

Using recombinant Listeria monocytogenes that express HPV-16 E7 (Lm-LLO-E7) to stimulate an antitumor response, we demonstrate that sensitivity to IFN-gamma is required for therapeutic efficacy in that Lm-LLO-E7 induces regression of TC1 tumors but not TC1.mugR. In addition, we show that tumor sensitivity to IFN-gamma is not required for inhibition of tumor angiogenesis by Lm-LLO-E7 or for trafficking of CD4+ and CD8+ T cells to the tumor. However, it is required for penetration of lymphocytes into the tumor mass in vivo.

CONCLUSIONS

Our findings identify a role for IFN-gamma in immunity to TC1 tumors and show that loss of tumor responsiveness to IFN-gamma poses a challenge to antigen-based immunotherapy.

Carcinoembryonic antigen antibody inhibits lung metastasis and augments chemotherapy in a human colonic carcinoma xenograft

PURPOSE

In addition to its use as a blood marker for many carcinomas, elevated expression of carcinoembryonic antigen (CEA, CD66e, CEACAM5) has been implicated in various biological aspects of neoplasia, especially tumor cell adhesion, metastasis, the blocking of cellular immune mechanisms, and having antiapoptosis functions. However, it is not known if treatment with anti-CEA antibodies can affect tumor metastasis or alter the effects of cytotoxic drugs.

METHODS

In vitro, human colon cancer cell lines were treated with anti-CEA MAb IgG1, hMN-14 (labetuzumab), to assess direct effects on proliferation, as well as antibody-dependent cellular cytotoxicity (ADCC), and complement-dependent cytotoxicity (CDC). In vivo studies were undertaken in nude mice bearing s.c. (local growth) or i.v. (metastatic model) GW-39 and LS174T human colon cancer grafts, to evaluate the MAb alone and in combination with either CPT-11 or 5-fluorouracil (5FU).

RESULTS

In vitro, labetuzumab did not induce apoptosis, nor did it affect tumor cell proliferation directly or by CDC, but it did inhibit tumor cell proliferation by ADCC. In vivo, labetuzumab did not increase median survival in the GW-39 metastatic model unless the mice were pretreated with GM-CSF to increase their peripheral WBC counts; GM-CSF alone was ineffective. Also, if GW-39 tumors were pretreated with IFN-gamma to up-regulate CEA expression threefold prior to i.v. injection, labetuzumab significantly increased median survival of the mice. When nude mice received labetuzumab with CPT-11 or 5FU, median survival increased significantly as compared to the drug or antibody alone.

CONCLUSIONS

Labetuzumab, a CEA-specific MAb, induces effector-cell function in vitro against CEA-positive colonic tumor cells, and also inhibits growth of lung metastasis when CEA expression is up-regulated or if peripheral WBCs are increased. The MAb also shows chemosensitizing properties.

Targeting the silent minority: emerging immunotherapeutic strategies for eradication of malignant stem cells in chronic myeloid leukaemia

Standard allogeneic stem cell transplantation (alloSCT) has provided a cure for chronic myeloid leukaemia (CML) over the last 25 years, but is only an option for a minority of patients. It was hoped that the introduction of imatinib mesylate (IM), a specific tyrosine kinase inhibitor that targets the Bcr-Abl oncogene product, would provide long-term remission or even cure for those patients without a donor, but studies have shown that IM does not eliminate leukaemic stem cells in CML patients. To overcome this problem of molecular persistence, research is underway to combine reduced intensity stem cell transplant or non-donor-dependent immunotherapies with IM with the aim of increasing cure rate, reducing toxicity and improving quality of life. The alternative approach is to combine IM or second-generation agents with other novel drugs that interrupt key signalling pathways activated by Bcr-Abl. This article will focus on the latest immunotherapy and molecularly targeted therapeutic options in CML and how they may be combined to improve the outcome for CML patients in the future.

Interaction of PD-L1 on tumor cells with PD-1 on tumor-specific T cells as a mechanism of immune evasion: implications for tumor immunotherapy

Programmed death receptor ligand 1 (PD-L1, also called B7-H1) is a recently described B7 family member. In contrast to B7-1 and B7-2, PD-L1 does not interact with either CD28 or CTLA-4. To date, one specific receptor has been identified that can be ligated by PD-L1. This receptor, programmed death receptor 1 (PD-1), has been shown to negatively regulate T-cell receptor (TCR) signaling. Upon ligating its receptor, PD-L1 has been reported to decrease TCR-mediated proliferation and cytokine production. PD-1 gene-deficient mice developed autoimmune diseases, which early led to the hypothesis of PD-L1 regulating peripheral tolerance. In contrast to normal tissues, which show minimal surface expression of PD-L1 protein, PD-L1 expression was found to be abundant on many murine and human cancers and could be further up-regulated upon IFN-gamma stimulation. Thus, PD-L1 might play an important role in tumor immune evasion. This review discusses the currently available data concerning negative T-cell regulation via PD-1, the blockade of PD-L1/PD-1 interactions, and the implications for adoptive T-cell therapies.

Expression of MHC class I, MHC class II, and cancer germline antigens in neuroblastoma

BACKGROUND

Neuroblastoma is the most common solid extracranial tumor in childhood, still with poor survival rates for metastatic disease. Neuroblastoma cells are of neuroectodermal origin and express a number of cancer germline (CG) antigens. These CG antigens may represent a potential target for immunotherapy such as peptide-based vaccination strategies.

OBJECTIVE

The purpose of this study was to analyze the presence of MAGE-A1, MAGE-A3/A6, and NY-ESO-1 on an mRNA and protein level and to determine the expression of MHC class I and MHC class II antigens within the same tumor specimens.

METHODS

A total of 68 tumors were available for RT-PCR, and 19/68 tumors were available for immunohistochemical (IHC) analysis of MAGE-A1, MAGE-A3/A6, and NY-ESO-1. In parallel, the same tumors were stained with a panel of antibodies for MHC class I and MHC class II molecules.

RESULTS

Screening of 68 tumor specimens by RT-PCR revealed expression of MAGE-A1 in 44%, MAGE-A3/A6 in 21%, and NY-ESO-1 in 28% of cases. Immunohistochemistry for CG antigens of selected tumors showed good agreement between protein and gene expression. However, staining revealed a heterogeneous expression of CG antigens. None of the selected tumors showed MHC class I or MHC class II expression.

CONCLUSIONS

mRNA expression of MAGE-A1, MAGE-A3/A6, and NY-ESO-1 is congruent with the protein expression as determined by immunohistochemistry. The heterogeneous CG-antigen expression and the lack of MHC class I and II molecules may have implications for T-cell-mediated immunotherapy in neuroblastoma.

Nitroaspirin corrects immune dysfunction in tumor-bearing hosts and promotes tumor eradication by cancer vaccination

Active suppression of tumor-specific T lymphocytes can limit the immune-mediated destruction of cancer cells. Of the various strategies used by tumors to counteract immune attacks, myeloid suppressors recruited by growing cancers are particularly efficient, often resulting in the induction of systemic T lymphocyte dysfunction. We have previously shown that the mechanism by which myeloid cells from tumor-bearing hosts block immune defense strategies involves two enzymes that metabolize L-arginine: arginase and nitric oxide (NO) synthase. NO-releasing aspirin is a classic aspirin molecule covalently linked to a NO donor group. NO aspirin does not possess direct antitumor activity. However, by interfering with the inhibitory enzymatic activities of myeloid cells, orally administered NO aspirin normalized the immune status of tumor-bearing hosts, increased the number and function of tumor-antigen-specific T lymphocytes, and enhanced the preventive and therapeutic effectiveness of the antitumor immunity elicited by cancer vaccination. Because cancer vaccines and NO aspirin are currently being investigated in independent phase I/II clinical trials, these findings offer a rationale to combine these treatments in subjects with advanced neoplastic diseases.

State-of-the-art management of nasopharyngeal carcinoma: current and future directions

Nasopharyngeal carcinoma (NPC) is a distinct type of head and neck cancer. Approximately 70% of patients with newly diagnosed NPC present with locally advanced disease. Phase III clinical trials support the addition of chemotherapy to radiotherapy for the initial treatment of these patients. Once metastatic disease develops, practices become varied. Further experience needs to be gained with both targeted therapies and immunotherapy to gauge whether they will improve treatment outcomes in NPC.

NK cell activation and tumor infiltration are involved in the antitumor mechanism of Virulizin

Previous studies have demonstrated antitumor efficacy of Virulizin in several human tumor xenograft models and a critical role for macrophages in the antitumor mechanism of Virulizin. Although there is growing support for an immune stimulatory mechanism of action for Virulizin, the details remain to be elucidated. The aim of this study was to determine whether infiltration of natural killer (NK) cells into xenografted tumors is altered by Virulizin treatment, and whether such alterations contribute to the antitumor activity of Virulizin. Immunohistochemical analysis demonstrated that xenografted tumors from Virulizin-treated mice had an increase in infiltration of F4/80(+) (macrophages) and NK1.1(+) (NK) cells. The increase in NK1.1(+) cell infiltration occurred at an early stage of Virulizin treatment, which correlated with an early sign of apoptosis. In addition, Virulizin resulted in an increase in the number of NK cells in the spleens, and NK cells isolated from the spleen exhibited increased cytotoxicity to tumor cells in vitro. In NK cell-deficient SCID-beige mice, the antitumor activity of Virulizin was compromised, providing additional support to the hypothesis that NK cells are necessary for inhibition of tumor growth by Virulizin. Finally, depletion of macrophages resulted in the loss of Virulizin-induced increase in NK1.1(+) cell infiltration into xenografted tumors, suggesting the involvement of macrophages in NK cell infiltration into tumors. Taken together, these results strongly support a mechanism in which Virulizin stimulates a sustained expansion and infiltration of NK cells and macrophages into tumors with subsequent activation of NK cells that is responsible for the observed antitumor activity.

Generation of Th1 T cell responses directed to a HLA Class II restricted epitope from the Aspergillus f16 allergen

The Aspergillus allergen Asp f16 has been shown to confer protective Th1 T cell-mediated immunity against infection with Aspergillus conidia in murine models. Here, we use overlapping (11-aa overlap with preceding peptide) pentadecapeptides spanning the entire 427-aa coding region of Asp f16 presented on autologous dendritic cells (DC) to evaluate the ability of this antigen to induce Th1 responses in humans. Proliferative responses were induced in five out of five donors, and one line with a high frequency of interferon (IFN)-gamma-producing CD4(+) T cells in response to the complete peptide pool was characterized. This line was cytotoxic to autologous pool-pulsed and Aspergillus culture extract-pulsed targets. Limitation of cytotoxicity to the CD4(+) T cell subset was demonstrated by co-expression of the degranulation marker CD107a in response to peptide pool-pulsed targets. Cytotoxic T lymphocytes (CTL) killed Aspergillus hyphae and CTL culture supernatant killed Aspergillus conidia. By screening 21 smaller pools and individual peptides shared by positive pools we identified a single candidate sequence of TWSIDGAVVRT that elicited responses equal to the complete pool. The defined epitope was presented by human leucocyte antigen (HLA)-DRB1-0301. These data identify the first known Aspergillus-specific T cell epitope and support the use of Asp f16 in clinical immunotherapy protocols to prime protective immune responses to prevent or treat Aspergillus infection in immunocompromised patients.

A CD80-transfected human breast cancer cell variant induces HER-2/neu-specific T cells in HLA-A*02-matched situations in vitro as well as in vivo

Adjuvant treatment is still only working in a small percentage of breast cancer patients. Therefore, new strategies need to be developed. Immunotherapies are a very promising approach because they could successfully attack tumor cells in the stage of dormancy. To assess the feasibility of using an allogeneic approach for vaccination of breast cancer patients, we selected a CD80-transfected breast cancer cell line based on its immunogenic properties. Using CD80+ KS breast cancer cells and human leukocyte antigen (HLA)-A*02-matched peripheral blood mononuclear cells (PBMCs) of breast cancer patients in allogeneic mixed lymphocyte-tumor cell cultures (MLTCs), it was possible to isolate HLA-A*02-restricted cytotoxic T cells (CTLs). Furthermore, a genetically modified KS variant expressing influenza A matrix protein serving as a surrogate tumor-associated antigen (TAA) was able to stimulate flu peptide-specific T cells alongside the induction of alloresponses in MLTCs. KS breast cancer cells were demonstrated to express already known TAAs such as CEA, MUC-1, MAGE-1, MAGE-2, and MAGE-3. To further improve antigenicity, HER-2/neu was added to this panel as a marker antigen known to elicit HLA-A*02-restricted CTLs in patients with breast cancer. Thus, the antigen-processing and antigen-presentation capacity of KS cells was further demonstrated by the stimulation of HER-2/neu-specific CD8+ T cells in PBMCs of breast cancer patients in vitro. These results gave a good rationale for a phase I/II trial, where the CD80+ HER-2/neu-overexpressing KS variant is actually used as a cellular vaccine in patients with metastatic breast cancer. As a proof of principle, we present data from two patients where a significant increase of interferon-gamma (IFN-gamma) release was detected when postvaccination PBMCs were stimulated by allogeneic vaccine cells as well as by HLA-A*02-restricted HER-2/neu epitopes. In whole cell vaccine trials, monitoring is particularly challenging because of strong alloresponses and limited knowledge of TAAs. In this study, a panel of HER-2/neu epitopes, together with the quantitative real time (qRT)-PCR method to analyze vaccine-induced cytokines secreted by T cells, proved to be highly sensitive and feasible to perform an "immunological staging" following vaccination.

Antibody buffering of a ligand in vivo

Clearance is the practical limit on drug action. Here we propose a means of slowing clearance, thereby extending drug lifetime in vivo by "antibody buffering." In this process, a drug and an anti-drug antibody are coadministered. Most of the drug is bound to the antibody, preventing the drug from acting, but also preventing its elimination. A dynamic free drug pool is established by reversible dissociation from the antibody. The free drug is active and can be eliminated, but the free pool is constantly replenished by reequilibration from the antibody-drug complex, giving a long effective lifetime. Here we explore antibody buffering experimentally by using a model compound, 2-phenyloxazol-5-one-gamma-aminobutyrate (Ox), as a drug proxy. We show that antibody buffering can extend by an order of magnitude the plasma lifetime of Ox in rats, and that the steady-state Ox level depends on the molecular properties of the antibody used to buffer the Ox. In addition, the anti-Ox antibody can be recharged with drug in vivo to extend Ox lifetime without additional antibody administration, making this technique even more suitable for possible clinical application.

Intratumoral immunotherapy: using the tumour against itself

Summary Diverse immunotherapy approaches have achieved success in controlling individual aspects of immune responses in animal models. Transfer of such immunotherapies to clinical trials has obtained some success in patients, with clinical responses observed or effective antigen specific immune responses achieved, but has had limited impact on patient survival. Key elements required to generate de novo cell-mediated antitumour immune responses in vivo include recruitment of antigen-presenting cells to the tumour site, loading these cells with antigen, and their migration and maturation to full antigen-presenting function. In addition, it is essential for antigen-specific T cells to locate the tumour to mediate cytotoxicity, emphasizing the need for local inflammation to target effector cell recruitment. We review those therapies that involve the tumour site as a target and source of antigen for the initiation of immune responses, and discuss strategies to generate and co-ordinate an optimal cell-mediated immune response to control tumours locally.

Prospective clinical trials of biotherapies in solid tumors: a 5-year survey

PURPOSE

To review the content and quality of prospective clinical trials of biotherapies in solid tumors.

METHODS

Data were collected from the literature between 1990 and 2002 on general study characteristics, patient and disease factors, study methodology, and factors related to completeness of reporting. Quality of phase II studies was evaluated by an ad hoc questionnaire. Descriptive statistics, contingency tables, and the chi-square test were applied.

RESULTS

A total of 334 studies were selected, of which about three quarters were multicenter, with 42.5% reporting phase I, 42.2% phase II or I/II, and 11.9% phase III or II/III studies. Only 13.7% were randomized, and a study design emphasizing statistical analysis was lacking in as many as one third. The assessment of biological endpoints was stated as the primary or secondary goal in half of these studies. Melanoma (17.1%), renal carcinoma (11.1%), gastrointestinal neoplasms (11.1%), and lymphomas (6.3%) were the most studied diseases. Immunotherapies accounted for 182 studies; the remaining 152 reported other biotherapies. Patients with (1) advanced disease (P = 0.003), (2) heavily pretreated neoplasms (P < 0.0001), (3) poor performance status (PS < 2) (P < 0.0001), were more frequently enrolled in studies of biotherapy. Biotherapies were less frequently evaluated in phase III studies (7/152) compared with immunotherapies (33/182) (P < 0.0001). A statistical study design was more frequently identified in biotherapy trials (127/152) compared with immunotherapy trials (98/182) (P < 0.0001). Biological endpoints were less frequently evaluated in phase III studies in both biotherapies (100% no vs 0% yes) and immunotherapies (81.8% no vs 18.2% yes) (P = 0.01, for biotherapies; P < 0.0001, for immunotherapies). Phase I immunotherapy studies more frequently applied biological or molecular criteria for patient selection (41.1%) than phase II (29.3%) and III (3.1%) studies (P < 0.0001).

CONCLUSIONS

The very wide diversity in modalities of conducting and reporting clinical trials of biotherapies of solid tumors and the presence of some methodological pitfalls suggest that the methodological standards for conducting and publishing clinical trials in biotherapies should be improved to enhance the reliability of the body of published data.

Costimulatory B7-H1 in renal cell carcinoma patients: Indicator of tumor aggressiveness and potential therapeutic target

Expression of B7-H1, a costimulating glycoprotein in the B7 family, is normally restricted to macrophage-lineage cells, providing a potential costimulatory signal source for regulation of T cell activation. In contrast, aberrant expression of B7-H1 by tumor cells has been implicated in impairment of T cell function and survival, resulting in defective host antitumoral immunity. The relationship between tumor-associated B7-H1 and clinical cancer progression is unknown. Herein, we report B7-H1 expression by both renal cell carcinoma (RCC) tumors of the kidney and RCC tumor-infiltrating lymphocytes. In addition, our analysis of 196 clinical specimens reveals that patients harboring high intratumoral expression levels of B7-H1, contributed by tumor cells alone, lymphocytes alone, or tumor and/or lymphocytes combined, exhibit aggressive tumors and are at markedly increased risk of death from RCC. In fact, patients with high tumor and/or lymphocyte B7-H1 levels are 4.5 times more likely to die from their cancer than patients exhibiting low levels of B7-H1 expression (risk ratio 4.53; 95% confidence interval 1.94-10.56; P < 0.001.) Thus, our study suggests a previously undescribed mechanism whereby RCC may impair host immunity to foster tumor progression. B7-H1 may prove useful as a prognostic variable for RCC patients both pre- and posttreatment. In addition, B7-H1 may represent a promising target to facilitate more favorable responses in patients who require immunotherapy for treatment of advanced RCC.

Targeting the immune system: novel therapeutic approaches in squamous cell carcinoma of the head and neck

Despite advances in surgery, radiotherapy, and chemotherapy, the overall survival rates for patients with squamous cell carcinoma of the head and neck (SCCHN) have not changed over the last decades. Clearly, novel therapeutic strategies are needed for this cancer, which is highly immunosuppressive. Therefore, biologic therapies able to induce and/or up-regulate antitumor immune responses could represent a complementary approach to conventional treatments. Because patients with SCCHN are frequently immunocompromised due to the elimination or dysfunction of critical effector cells of the immune system, it might be necessary to restore these immune functions to allow for the generation of more effective antitumor host responses. Simultaneously, to prevent tumor escape, it might be necessary to alter attributes of the malignant cells. The present review summarizes recent advances in the field of immunotherapy of SCCHN, including techniques of nonspecific immune stimulation, the use of monoclonal antibodies, advances in adoptive immunotherapy and genetic engineering, as well as anticancer vaccines. These biologic therapies, alone or in combination with conventional treatment, are likely to develop into useful future treatment options for patients with SCCHN.

CD4+ T cells kill Id+ B-lymphoma cells: FasLigand-Fas interaction is dominant in vitro but is redundant in vivo

B-lymphoma cells express a highly tumor-specific antigen, monoclonal Ig, which is a promising target for immunotherapy. Previous work has demonstrated that B-lymphoma cells spontaneously process their endogenous monoclonal Ig and present variable (V) region peptides (Id-peptides) on their MHC class II molecules to CD4+ T cells. Id-specific CD4+ T cells protect mice against B-lymphoma cells in the absence of antiidiotypic antibodies. The molecular mechanism by which Id-specific CD4+ T cells kill B-lymphoma cells is hitherto unknown. We here demonstrate in an Id-specific T-cell receptor (TCR)-transgenic mouse model that Id-specific CD4+ T cells induce apoptosis of Fas+ B-lymphoma cells in vitro by FasLigand (FasL)-Fas interaction. Moreover, the rare B lymphomas that had escaped rejection in TCR-transgenic mice had down-regulated their sensitivity to Fas-mediated apoptosis. Although these results suggest that FasL-Fas interaction is important, Id-specific CD4+ T cells could eliminate Id+ B-lymphoma cells in vivo by other mechanisms, since three independent ways of blocking FasL-Fas-mediated killing failed to abrogate tumor protection in TCR-transgenic mice. These results suggest that there are several redundant pathways by which Id-specific CD4+ T cells eliminate Id+ B-lymphoma cells in vivo, of which FasL-Fas interaction is only one.

Both soluble and membrane-bound forms of Flt3 ligand enhance tumor immunity following "suicide" gene therapy in a murine colon carcinoma model

In prodrug-activated ("suicide") gene therapy, tumor cells are transfected with the gene for an enzyme that converts an inactive prodrug, such as ganciclovir (GCV), to a toxic compound. Transfected cells are killed on administration of GCV, as also are untransfected "bystander" cells. The ability of the dendritic cell stimulatory cytokine Flt3 ligand (Flt3-L) to modulate prodrug-activated gene therapy has been investigated. Transfectants of the murine colon carcinoma MC26 were generated expressing soluble (FLS) and membrane-bound forms of Flt3-L. They were inoculated together with wild-type MC26 cells and cells expressing herpes simplex virus-1 (HSV1) thymidine kinase into BALB/c mice, which were then administered GCV. Expression of Flt3-L or FLS prevented regrowth of tumor in most mice, which was comparable to the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF), while tumors recurred in all mice receiving "suicide" gene therapy alone. Recurring tumor cells were resistant to direct killing by GCV but sensitive to "bystander" killing in vitro. Mice without tumor recurrence were rechallenged with unmodified MC26 cells. Of those mice given transfectants expressing GM-CSF, Flt3-L, or FLS, approximately 50% were immune to rechallenge. These mice also showed cytotoxic and proliferative responses to MC26 cells. These experiments show that both soluble and membrane-bound forms of Flt3-L were able to induce a protective immune response to colon carcinoma cells in a fashion similar to GM-CSF.

Immunotherapy with bovine aortic endothelial cells in subcutaneous and intracerebral glioma models in rats: effects on survival time, tumor growth, and tumor neovascularization

High-grade gliomas are aggressive tumors of the central nervous system characterized by endothelial cell proliferation and a high degree of vascularity. Conventional antitumoral treatments (i.e., surgery, radiotherapy, and chemotherapy) do not achieve satisfactory results (median survival in glioblastoma 12-18 months). It has been suggested that immunotherapy with xenogenic endothelial cells could slow tumor growth rate in a number of tumors in a murine model, but the study did not include gliomas. In experiments performed in our laboratory, vaccination with proliferating bovine aortic endothelium increased survival time in Fischer rats inoculated intracerebrally with 9L. Immunotherapy was also able to reduce the growth of subcutaneously injected 9L gliosarcoma cells in Fischer rats and to decrease microvessel density within the tumors, in the absence of major organ toxicity. Immunoglobulins (Ig) in the sera from vaccinated rats stained bovine aortic endothelium as well as human umbilical vein endothelium in active proliferation. Moreover, immune sera from immunized rats stained microvessels of human malignant glioma specimens and vessels of intracerebrally implanted tumors. Two proteins of MW of 11 and 19 kDa were identified by Western blot as targets of Ig elicited by vaccination. A possible future development is to select peptides/proteins suitable for vaccination in humans, avoiding the biohazards connected with xenogenic whole-cell vaccination.

Immunotherapy of intracranial G422 glioblastoma with dendritic cells pulsed with tumor extract or RNA

OBJECTIVE

To investigate the anti-tumor efficacy of dendritic cell (DC)-based vaccines pulsed with tumor extracts or RNA in a mouse model of intracranial G422 glioblastoma.

METHODS

Bone marrow-derived DCs were pulsed ex vivo with tumor extracts or RNA. Ninety female mice harboring 4-day-old intracranial G422 glioblastomas and 126 normal mice were treated with three spaced one week apart subcutaneous injections either with PBS, unpulsed DCs, G422 tumor extracts, RNA, DCs pulsed with G422 tumor extracts (DC/extract) or with RNA (DC/RNA). Seven days after the third immunization of normal mice, the spleens of 36 of them were harvested for cytotoxic T lyphocyte (CTL) assays and the others were challenged in the brain with G422 tumor cells. All the treated mice were followed for survival. Some mice brains were removed and examined pathologically when they died.

RESULTS

Immunization using DC/extract or DC/RNA significantly induced G422-specific CTL responses compared with control groups (P<0.01). Vaccination with DC/extract or DC/RNA, either prior to G422 tumor challenge or in tumor-harboring mice, significantly prolonged survival compared with other control groups (P<0.01).

CONCLUSION

DCs pulsed with tumor extracts or RNA derived from autologous tumors has potential antitumor effects via activation of cell-mediated immunity. Our results suggest a useful therapeutic strategy against gliomas.

Effective immunotherapy against cancer: a question of overcoming immune suppression and immune escape?

During the last decade, the breakthroughs in understanding of the molecular mechanisms responsible for immune activation and the advent of recombinant DNA technologies have changed the view on immunotherapy from "a dream scenario" to becoming a clinical reality. It is now clear that both cellular immunity comprising T and NK cells, as well as strategies based on antibodies, can provide strong antitumoral effects, and evidence is emerging that these strategies may also cure patients with previously incurable cancers. However, there are still a number of issues that remain unresolved. Progress in immunotherapy against cancer requires a combination of new, improved clinical protocols and strategies for overcoming mechanisms of immune escape and tumor-induced immune suppression. This review discusses some of the salient issues that still need to be resolved, focusing on the role of oxidative stress and the use of antioxidants to alleviate the immune hyporesponsiveness induced by reactive oxygen species (ROS).

Dendritic cells can be rapidly expanded ex vivo and safely administered in patients with metastatic breast cancer

PURPOSE

Immunotherapy using either dendritic cells (DCs) or expanded cytotoxic T cells (CTLs) has received increased interest in the treatment of specific malignancies including metastatic breast cancer (MBC). DCs can be generated ex vivo from monocytes or CD34+ precursors. The ability to expand and safely administer CD34-derived DCs in patients with MBC that have received prior cytotoxic chemotherapy has not been evaluated.

METHODS

We enrolled ten patients with MBC that had received prior chemotherapy for the treatment of metastatic disease on a phase I/II trial designed to test the safety and feasibility of administering ex vivo expanded DCs from CD34+ progenitor cells.

RESULTS

Using a cocktail of multiple different cytokines, we could expand DCs 19-fold compared to the initial CD34-selected product, which allowed the administration of as many as six vaccine treatments per patient. Patients received three to six injections i.v. of DCs pulsed with either the wild type GP2 epitope from the HER-2/neu protein or an altered peptide ligand, isoleucine to leucine (I2L). Toxicity was mild, with no patients demonstrating grade III toxicity during the treatment. Two patients with subcutaneous disease had a partial response to therapy, while IFN-gamma-producing CD8+ T cells could be found in two other patients during treatment.

CONCLUSIONS

This approach is safe and effective in generating a significant quantity of DCs from CD34-precursors.

Mesothelin-specific CD8(+) T cell responses provide evidence of in vivo cross-priming by antigen-presenting cells in vaccinated pancreatic cancer patients

Tumor-specific CD8(+) T cells can potentially be activated by two distinct mechanisms of major histocompatibility complex class I-restricted antigen presentation as follows: direct presentation by tumor cells themselves or indirect presentation by professional antigen-presenting cells (APCs). However, controversy still exists as to whether indirect presentation (the cross-priming mechanism) can contribute to effective in vivo priming of tumor-specific CD8(+) T cells that are capable of eradicating cancer in patients. A clinical trial of vaccination with granulocyte macrophage-colony stimulating factor-transduced pancreatic cancer lines was designed to test whether cross-presentation by locally recruited APCs can activate pancreatic tumor-specific CD8(+) T cells. Previously, we reported postvaccination delayed-type hypersensitivity (DTH) responses to autologous tumor in 3 out of 14 treated patients. Mesothelin is an antigen demonstrated previously by gene expression profiling to be up-regulated in most pancreatic cancers. We report here the consistent induction of CD8(+) T cell responses to multiple HLA-A2, A3, and A24-restricted mesothelin epitopes exclusively in the three patients with vaccine-induced DTH responses. Importantly, neither of the vaccinating pancreatic cancer cell lines expressed HLA-A2, A3, or A24. These results provide the first direct evidence that CD8 T cell responses can be generated via cross-presentation by an immunotherapy approach designed to recruit APCs to the vaccination site.

Generation of dendritic cell-tumor cell hybrids by electrofusion for clinical vaccine application

Vaccination with hybrids comprising fused dendritic cells (DCs) and tumor cells is a novel cancer immunotherapy approach designed to combine tumor antigenicity with the antigen-presenting and immune-stimulatory capacities of DCs. For clinical purposes, we have incorporated a large-scale process for the generation of clinical-grade DCs together with novel electrofusion technology. The electrofusion system provides for ease and standardization of method, efficient DC-tumor cell hybrid formation, and large-quantity production of hybrids in a high-volume (6-ml) electrofusion chamber. In addition, we have evaluated DC electrofusion with a variety of allogeneic human tumor cell lines with the rationale that these tumor cell partners would prove a ready, suitable source for the generation of DC-tumor cell hybrid vaccines. The DC production process can generate 6x10(8) to 2x10(9) DCs from a single leukapheresis product (approximately 180 ml). As determined by FACS analysis, electrofusion of 6x10(7) total cells (1:1 ratio of DC and tumor cells) resulted in a consistent average of 8-10% DC-tumor cell hybrids, irrespective of the tumor type used. Hybrids were retained in the population for 48 h postfusion and following freezing and thawing. Upon pre-irradiation of the tumor cell partner for vaccine purposes, the overall fusion efficiency was not altered at doses up to 200 Gy. Evaluation of DC-tumor cell hybrid populations for their ability to stimulate T-cell responses demonstrated that electrofused populations are superior to mixed populations of DCs and tumor cells in generating a primary T-cell response, as indicated by IFN-gamma release. Moreover, hybrids comprising HLA-A*0201 DCs and allogeneic melanoma tumor cells (Colo 829 cell line) stimulated IFN-gamma secretion by antigen-specific CD8+ T cells, which are restricted for recognition of a melanoma gp100 peptide antigen (gp100(209-217)) within the context of the DC HLA haplotype. Maturation of the DC-Colo 829 cell hybrid population served to further improve this T-cell gp100-specific response. Overall, our results are promising for the large-scale generation of electrofused hybrids comprising DCs and allogeneic tumor cells, that may prove useful in human vaccine trials.

Pilot study of treatment of biochemotherapy-refractory stage IV melanoma patients with autologous dendritic cells pulsed with a heterologous melanoma cell line lysate

Eleven AJCC stage IV melanoma patients with progressive disease after treatment with biochemotherapy were treated with autologous dendritic cells pulsed with heterologous tumor cell lysates. The vaccine used mature DCs (CD1a+++, CD40++, CD80++, CD83+, and CD86+++) generated from peripheral blood monocytes in the presence of GM-CSF and IL-4. After 7 days, DCs were matured with a defined cocktail of cytokines (IL-1+IL-6+TNF-alpha+PGE2) and simultaneously pulsed with lysates of heterologous melanoma cell lines, for 2 days. A total of 4 x 10(6) DCs was injected monthly under ultrasound control in an inguinal lymph node of normal appearance. The study was closed when all patients died as a consequence of tumor progression. No sign of toxicity was observed during the study. One patient experienced a partial response lasting 5 months, and two patients showed a mixed response which lasted 3 months. The median survival of the whole group was 7.3 months (range 3-14 months). This vaccination program had specific antitumoral activity in highly pretreated and large tumor burden stage IV melanoma patients and was well tolerated. The clinical responses and the median survival of the group of patients, together with the low toxicity of our DC vaccine, suggest that this approach could be applied to earlier AJCC stage IV melanoma patients.

WT1 peptide vaccination combined with BCG-CWS is more efficient for tumor eradication than WT1 peptide vaccination alone

A Wilms' tumor gene WT1 is expressed at high levels not only in most types of leukemia but also in various types of solid tumors, including lung and breast cancer. WT1 protein has been reported to serve as a target antigen for tumor-specific immunotherapy both in vitro in human systems and in vivo in murine models. We have shown that mice immunized with WT1 peptide or WT1 cDNA could reject a challenge from WT1-expressing tumor cells (a "prophylactic" model). However, it was not examined whether WT1 peptide vaccination had the potency to reject tumor cells in a "therapeutic" setting. In the present study, we demonstrated for the first time that WT1 peptide vaccination combined with Mycobacterium bovis bacillus Calmette-Guérin cell wall skeleton (BCG-CWS) was more effective for eradication of WT1-expressing tumor cells that had been implanted into mice before vaccination (a "therapeutic" model) compared with WT1 peptide vaccination alone. An intradermal injection of BCG-CWS into mice, followed by that of WT1 peptide at the same site on the next day, generated WT1-specific cytotoxic T lymphocytes (CTLs) and led to rejection of WT1-expressing leukemia or lung cancer cells. These results showed that BCG-CWS, which was well known to enhance innate immunity, could enhance WT1-specific immune responses (acquired immunity) in combination with WT1 peptide vaccination. Therefore, WT1 peptide vaccination combined with BCG-CWS may be applied to cancer immunotherapy in clinical settings.

alpha-Tocopheryl succinate sensitizes established tumors to vaccination with nonmatured dendritic cells

PURPOSE

Dendritic cells (DCs) are considered potential candidates for cancer immunotherapy due to their ability to process and present antigens to T cells and stimulate immune responses. However, DC-based vaccines have exhibited minimal effectiveness against established tumors in mice and human cancer patients. The use of appropriate adjuvants can enhance the efficacy of DC-based cancer vaccines in treating established tumors.

METHODS

In this study we have employed alpha-tocopheryl succinate (alpha-TOS), a nontoxic esterified analogue of vitamin E, as an adjuvant to enhance the effectiveness of DC vaccines in treating established murine Lewis lung (3LL) carcinomas.

RESULTS

We demonstrate that locally or systemically administered alpha-TOS in combination with nonmatured DCs injected intratumorally (i.t.) or subcutaneously (s.c.) significantly inhibits the growth of preestablished 10-day tumors (mean tumor volume of 77.5 +/- 17.8 mm3 on day 30 post-tumor injection) as compared to alpha-TOS alone (mean tumor volume of 471 +/- 68 mm3 on day 30 post-tumor injection). Additionally, the adjuvant effect of alpha-TOS was superior to that of cyclophosphamide (CTX). The mean tumor volume on day 28 post-tumor injection in mice treated with CTX+DCs was 611 +/- 94 mm3 as compared to 105 +/- 36 mm3 in mice treated with alpha-TOS+DCs. Analysis of purified T lymphocytes from mice treated with alpha-TOS+DC revealed significantly increased secretion of IFN-gamma as compared to T cells from the various control groups.

CONCLUSION

This study demonstrates the potential usefulness of alpha-tocopheryl succinate, an agent nontoxic to normal cell types, as an adjuvant to augment the effectiveness of DC-based vaccines in treating established tumors.

Phase I/II trial of immunogenicity of a human papillomavirus (HPV) type 16 E7 protein-based vaccine in women with oncogenic HPV-positive cervical intraepithelial neoplasia

PURPOSE

Infection with oncogenic human papillomavirus (HPV) and HPV-16 in particular is a leading cause of anogenital neoplasia. High-grade intraepithelial lesions require treatment because of their potential to progress to invasive cancer. Numerous preclinical studies have demonstrated the therapeutic potential of E7-directed vaccination strategies in mice tumour models. In the present study, we tested the immunogenicity of a fusion protein (PD-E7) comprising a mutated HPV-16 E7 linked to the first 108 amino acids of Haemophilus influenzae protein D, formulated in the GlaxoSmithKline Biologicals adjuvant AS02B, in patients bearing oncogenic HPV-positive cervical intraepithelial neoplasia (CIN).

METHODS

Seven patients, five with a CIN3 and two with a CIN1, received three intramuscular injections of adjuvanted PD-E7 at 2-week intervals. Three additional CIN1 patients received a placebo. CIN3 patients underwent conization 8 weeks postvaccination. Cytokine flow cytometry and ELISA were used to monitor antigen-specific cellular and antibody responses from blood taken before and after vaccine or placebo injection.

RESULTS

Some patients had preexisting systemic IFN-gamma CD4+ (1/10) and CD8+ (5/10) responses to PD-E7. Vaccination, not placebo injection, elicited systemic specific immune responses in the majority of the patients. Five vaccinated patients (71%) showed significantly increased IFN-gamma CD8+ cell responses upon PD-E7 stimulation. Two responding patients generated long-term T-cell immunity toward the vaccine antigen and E7 as well as a weak H. influenzae protein D (PD)-directed CD4+ response. All the vaccinated patients, but not the placebo, made significant E7- and PD-specific IgG.

CONCLUSIONS

The encouraging results obtained from this study performed on a limited number of subjects justify further analysis of the efficacy of the PD-E7/AS02B vaccine in CIN patients.

T-cell-mediated lysis of B cells induced by a CD19xCD3 bispecific single-chain antibody is perforin dependent and death receptor independent

A recently developed bispecific antibody construct, directed against CD19 and CD3 (bscCD19xCD3), induces T-cell-mediated lysis of allogeneic and autologous B cells in a specific and highly efficient manner. Since knowledge of the molecular mechanisms underlying this lysis is limited, a study on bscCD19xCD3-activated T-cell-effector pathways was performed. BscCD19xCD3-induced lysis of target B-cell lines Nalm-6, Daudi, and Raji and of autologous primary B cells is caused by the perforin-dependent granule-exocytosis pathway but not by the death ligands FasL, TRAIL, or TNF-alpha. When activated by bscCD19xCD3 and Raji cells, T cells express FasL mRNA, but incubation of Raji cells with cell-free supernatants from cytotoxicity experiments caused an upregulation of c-Flipl, possibly accounting for the cells' insensitivity toward death-receptor-mediated lysis. In addition to granule exocytosis, Raji cells are lysed by at least one mechanism independent of perforin, which requires transport through the T cell's Golgi apparatus.