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.

Vaccination with p53-peptide-pulsed dendritic cells, of patients with advanced breast cancer: report from a phase I study

Peptides derived from over-expressed p53 protein are presented by class I MHC molecules and may act as tumour-associated epitopes. Due to the diversity of p53 mutations, immunogenic peptides representing wild-type sequences are preferable as a basis for a broad-spectrum p53-targeting cancer vaccine. Our preclinical studies have shown that wild-type p53-derived HLA-A2-binding peptides are able to activate human T cells and that the generated effector T cells are cytotoxic to human HLA-A2+, p53+ tumour cells. In this phase I pilot study, the toxicity and efficacy of autologous dendritic cells (DCs) loaded with a cocktail of three wild-type and three modified p53 peptides are being analysed in six HLA-A2+ patients with progressive advanced breast cancer. Vaccinations were well tolerated and no toxicity was observed. Disease stabilisation was seen in two of six patients, one patient had a transient regression of a single lymph node and one had a mixed response. ELISpot analyses showed that the p53-peptide-loaded DCs were able to induce specific T-cell responses against modified and unmodified p53 peptides in three patients, including two of the patients with a possible clinical benefit from the treatment. In conclusion, the strategy for p53-DC vaccination seems safe and without toxicity. Furthermore, indications of both immunologic and clinical effect were found in heavily pretreated patients with advanced breast cancer. An independent clinical effect of repeated administration of DCs and IL-2 can not of course be excluded; further studies are necessary to answer these questions.

Rhabdomyosarcomas are potential target of MAGE-specific immunotherapies

The search for alternative strategies of therapy remains a major issue for most neoplastic diseases. The expression of several tumor antigens makes human rhabdomyosarcomas, which are the most frequent form of soft tissue tumor in children, a good candidate for tumor-specific immunotherapy. To assess the feasibility of this approach, we evaluated the ability of rhabdomyosarcoma cell lines to process and present the MAGE-A tumor antigens to effectors of the immune system. To this end, we investigated recognition of MAGE-A-positive rhabdomyosarcoma cells by HLA-B*3701-restricted T cells specific for a MAGE-A-derived peptide. Low level of HLA expression impaired recognition of the tumor cells. Therefore, to obtain HLA expression avoiding the use of IFN-gamma and TNF-alpha, which could affect the proteasome activity, a rhabdomyosarcoma line was transduced by a retroviral vector encoding the HLA-B*3701 allele. Recognition of the infected cells was then observed also in the absence of IFN-gamma and TNF-alpha treatment, thus demonstrating that rhabdomyosarcoma cells were indeed able to naturally process and present the MAGE-A antigens. These results demonstrate that rhabdomyosarcoma cells expressing MAGE-A can be targets of tumor-specific effectors, suggesting the feasibility of clinical protocols of specific immunotherapy also for the treatment of rhabdomyosarcoma.

Phase 1B study to improve immune responses in head and neck cancer patients using escalating doses of 25-hydroxyvitamin D3

Patients with head and neck squamous cell carcinoma (HNSCC) have profound immune defects. These defects are associated with a poor prognosis and are mediated, in part, by immune inhibitory CD34(+) progenitor cells, whose numbers are increased in the peripheral blood of HNSCC patients. Immune inhibitory CD34(+) cells are also present within HNSCC tumors. A phase IB clinical trial was conducted with HNSCC patients to determine if treatment with the differentiation-inducer 25-hydroxyvitamin D(3) could diminish CD34(+) cell levels and improve a panel of immune parameters. Here we present the results of treatment with orally administered escalating doses (20, 40, 60 microg) of 25-hydroxyvitamin D(3), with an emphasis on the six patients who received the maximum dosage of 60 microg per day. Peripheral blood was collected at 0, 1, 2, 4, and 6 weeks, and assessed for markers of immune activity. Although no clinical responses were observed, results of this pilot study demonstrated that treatment of HNSCC patients with 25-hydroxyvitamin D(3 )reduces the number of immune suppressive CD34(+) cells, increases HLA-DR expression, increases plasma IL-12 and IFN-gamma levels, and improves T-cell blastogenesis. In contrast, 25-hydroxyvitamin D(3) treatment did not modulate plasma IL-1beta, IL-2, IL-4, IL-6, IL-10, GM-CSF, or TGF-beta levels.

Trials and tribulations of immunotherapy as a treatment option for patients with squamous cell carcinoma of the head and neck

Head and neck squamous cell carcinoma (HNSCC) is an aggressive epithelial malignancy that is the sixth most common neoplasm in the world. Despite numerous advances in treatments involving surgery, radiation, and chemotherapy, the 5-year survival has remained at less than 50% for the last 30 years primarily due to local recurrences [66]. Consequently, the possibility of developing immunotherapeutic approaches as a treatment for HNSCC has gained interest. The present review has 3 objectives pertaining to immunotherapeutic means to treat HNSCC patients: (1) to summarize the feasibility of such approaches, (2) to provide an overview of the obstacles to attaining protective immune reactivity, and (3) to consider how these obstacles can be overcome to stimulate immune reactivity to HNSCC. These objectives will also be considered in the context of what lessons have been learned from immunotherapeutic trials for other solid malignancies and the applicability of this information to HNSCC.

Melanoma cells transfected to express CD83 induce antitumor immunity that can be increased by also engaging CD137

Interactions between CD83 and its ligand(s) can up-regulate immune responses. M2-CD83 cells, derived by transfecting the M2 clone of mouse melanoma K1735 cells to express mouse CD83, were rejected by syngeneic mice, unless they were injected with a CD83Ig fusion protein. Rejection was mediated by CD4+ and CD8+ T cells plus natural killer cells, whereas rejection of M2-1D8 cells, which express anti-CD137 single-chain variable region fragments (scFv), occurs in the absence of CD8+ T cells. Furthermore, the tumor specificity of the immunity induced by the two cell lines differed. Immunization with live or mitomycin C-treated M2-CD83 cells prevented outgrowth of transplanted M2-WT cells and had therapeutic efficacy against established M2-WT tumors. A highly metastatic clone of K1735 cells, SW1-C, and its subline SW1-P2, which expresses an activating transcription factor 2-driven peptide, were then studied because they have particularly low immunogenicity. Neither SW1-C nor SW1-P2 cells became rejectable after expression of CD83 or anti-CD137 scFv. However, outgrowth of cells from either line was delayed in mice immunized against M2-CD83 or M2-1D8 cells, and immunization with a mixture of mitomycin C-treated cells from M2-CD83 plus M2-1D8 prevented tumor formation by SW1-P2 cells in five of five and by SW1-C cells in three of five mice. We conclude that M2 cells expressing CD83 can induce a tumor-destructive immune response also against SW1 cells and that this response can be made more effective by combining them with M2 cells expressing anti-CD137 scFv. A similar approach may be therapeutically beneficial against certain human cancers.

Clinical applications of dendritic cell vaccination in the treatment of cancer

Dendritic cell (DC) immunotherapy has shown significant promise in animal studies as a potential treatment for cancer. Its application in the clinic depends on the results of human trials. Here, we review the published clinical trials of cancer immunotherapy using exogenously antigen-exposed DCs. We begin with a short review of general properties and considerations in the design of such vaccines. We then review trials by disease type. Despite great efforts on the part of individual investigative groups, most trials to date have not yielded data from which firm conclusions can be drawn. The reasons for this include nonstandard DC preparation and vaccination protocols, use of different antigen preparations, variable means of immune assessment, and nonrigorous criteria for defining clinical response. While extensive animal studies have been conducted using DCs, optimal parameters in humans remain to be established. Unanswered questions include optimal cell dose, use of mature versus immature DCs for vaccination, optimal antigen preparation, optimal route, and optimal means of assessing immune response. It is critical that these questions be answered, as DC therapy is labor- and resource-intensive. Cooperation is needed on the part of the many investigators in the field to address these issues. If such cooperation is not forthcoming, the critical studies that will be required to make DC therapy a clinically and commercially viable enterprise will not take place, and this therapy, so promising in preclinical studies, will not be able to compete with the many other new approaches to cancer therapy presently in development. Trials published in print through June 2003 are included. We exclude single case reports, except where relevant, and trials with so many variables as to prevent interpretation about DC therapy effects.

Exosome-based immunotherapy

Exosomes are small membrane vesicles originating from late endosomes and secreted by hematopoietic and epithelial cells in culture. Exosome proteic and lipid composition is unique and might shed some light into exosome biogenesis and function. Exosomes secreted from professional antigen-presenting cells (i.e., B lymphocytes and dendritic cells) are enriched in MHC class I and II complexes, costimulatory molecules, and hsp70-90 chaperones, and have therefore been more extensively studied for their immunomodulatory capacities in vitro and in vivo. This review will present the main biological features pertaining to tumor or DC-derived exosomes, will emphasize their immunostimulatory function, and will discuss their implementation in cancer immunotherapy.

A primer on cancer immunology and immunotherapy

The role of immunity in cancer has been abundantly demonstrated in murine tumor models as well as in man. Induction of clinically effective antitumor immune responses, based on this information, in patients with cancer however, remains elusive. This is not because tumors lack recognizable antigens [in fact there is evidence that there are thousands of potential novel targets in each tumor cell] but rather due to the fact that the induction of responses is not adequate nor particularly well understood. Tumors seem to be rather effective at limiting immune responses. Many of the molecularly defined antigens that have been detected on tumor cells are derived from self-proteins and as such are subject to tolerizing mechanisms. Such tumors have also developed escape mechanisms capable of evading or suppressing immune responses. Understanding the role of dendritic cells during the effector phase of the immune response and the complex interactions of stromal, immune, and tumor cells in the tumor microenvironment represent the next challenges to be understood for tumor immunology.

Apoptosis pathways in cancer and cancer therapy

Activation of apoptosis pathways is a key mechanism by which cytotoxic drugs kill tumor cells. Also immunotherapy of tumors requires an apoptosis sensitive phenotype of target cells. Defects in apoptosis signalling contribute to resistance of tumors. Activation of apoptosis signalling following treatment with cytotoxic drugs has been shown to lead to activation of the mitochondrial (intrinsic) pathway of apoptosis. In addition, signalling through the death receptor (extrinsic) pathways, contributes to sensitivity of tumor cells towards cytotoxic treatment. Both pathways converge finally at the level of activation of caspases, the effector molecules in most forms of cell death. In addition to classical apoptosis, non-apoptotic modes of cell death have recently been identified. Mechanisms to overcome apoptosis resistance include direct targeting of antiapoptotic molecules expressed in tumors as well as re-sensitization of previously resistant tumor cells by re-expression of caspases and counteracting apoptotis inhibitory molecules such as Bcl-2 and molecules of the IAP family of endogenous caspase inhibitors. Molecular insights into regulation of apoptosis and defects in apoptosis signalling in tumor cells will provide novel approaches to define sensitivity or resistance of tumor cells towards antitumor therapy and provide new targets for rational therapeutic interventions for future therapeutic strategies.

Designer glycopeptides for cytotoxic T cell-based elimination of carcinomas

Tumors express embryonic carbohydrate antigens called tumor-associated carbohydrate antigens (TACA). TACA-containing glycopeptides are appealing cytotoxic T cell (CTL)-based vaccines to prevent or treat cancer because the same sugar moieties are expressed in a variety of tumors, rendering a vaccination strategy applicable in a large population. Here we demonstrate that by using glycopeptides with high affinity for the major histocompatibility complex and glycosylated in a position corresponding to a critical T cell receptor (TcR) contact, it is possible to induce anti-TACA CTL in vivo. In the current study we show that designer glycopeptides containing the Thomsen-Freidenreich (TF) antigen (beta-Gal-[1-->3]-alpha-GalNAc-O-serine) are immunogenic in vivo and generate TF-specific CTL capable of recognizing a variety of tumor cells in vitro including a MUC1-expressing tumor. The fine specificity of the TF-specific CTL repertoire indicates that the TcR recognize the glycosylated amino acid residue together with TF in a conventional major histocompatibility complex class I-restricted fashion. These results have high potential for immunotherapy against a broad range of tumors.