Neoadjuvant and adjuvant strategies in renal cell carcinoma: more questions than answers

The current standard treatment for early stage (I-III) renal cell cancer (RCC) is surgery. While the prognosis of stage I tumors is excellent, stage II and particularly stage III have a high risk of relapse. The adjuvant treatment of patients with RCC remains an area of investigation, with patient selection being a key aspect. There are currently two prognostic nomograms to establish the risk of relapse in patients with resected RCC. The results of earlier studies of adjuvant therapy, including the use chemotherapy and/or immunotherapy after nephrectomy have failed to show any benefit in the outcome of patients at risk of developing local recurrence or distant metastases. Two recent phase III trials with vaccines (autologous tumor cell vaccine and autologous tumor-derived heat shock protein peptide complex-96) have shown promising, albeit still preliminary, results. In the metastatic RCC setting, recent advances in the molecular understanding of oncogenic pathways have led to the development of new therapeutic strategies with the use of targeted therapies in the adjuvant setting. Neoadjuvant treatment is another treatment modality currently being evaluated for patients with early disease and in patients with metastatic RCC with inoperable primary tumors. The questions that remain unanswered include activity of these agents in early stages of the disease, patient selection, optimal start time of the adjuvant treatment, and finally, the optimal length of treatment.     

Immunotherapy as part of combinations for the treatment of cancer

Immunotherapy (biological therapy) comprises such things as active specific immunotherapy ("cancer vaccines"), nonspecific immunostimulation with cytokines, and the inhibition of suppressor influences exerted or elicited by the tumor. Just as cancer chemotherapy began with the use of single agents and evolved into combination therapy, so immunotherapeutic agents have been combined with each other and with chemotherapy. The alkylating agent cyclophosphamide (Cytoxan; CY) has been used for many years to inhibit tumor-derived suppressor influences in rodents, and has been exploited for the same use in humans. Combinations of CY and cancer vaccines such as autologous tumor cells, Melacine, large multivalent immunogen (LMI), and Theratope have been tested with some success in humans for more than a decade. In this use, the CY is a biological response modifier rather than an antitumor agent. Delayed treatment with CY in treating mouse plasmacytomas has proved more effective than immediate treatment, probably because it allows immunity to develop in the host. CY and moderate-dose interleukin-2 (IL-2) have also been a useful regimen in treating human melanomas. IL-2 is itself a useful component of combination immunotherapy, such as with melanoma peptide vaccines, or with interferon-alfa-2b, (IFN-a), as a dual combination or part of a biochemotherapy regimen. IL-2 and histamine, to block reactive oxygen species, may be a more useful combination for treatment of liver metastases of melanoma than IL-2 alone. In this combination, the histamine may permit continued, unimpeded activity of cytolytic T lymphocytes. Several different combinations of drugs and biological agents have been used as biochemotherapy for melanoma, but although there are higher immediate response rates, the long-range survival benefits have been marginal, not justifying the severe toxicity. Combinations of 5-fluorouracil (5-FU) and IFN-a or levamisole have had efficacy in colon and head and neck cancers, but here the biological agents acted as biochemical modulators. Trials of antibodies and chemotherapy have been limited. It appears that trastuzumab (Herceptin) potentiates antitumor therapy in breast cancer and also increases the cardiotoxicity of those regimens.     

肿瘤糖疫苗的研究进展

肿瘤细胞表面异常表达的糖抗原为肿瘤糖疫苗的研究提供了合适的靶标, 然而由于这些糖抗原的免疫原性较差, 这又给糖疫苗的发展带来了很大的困难。本文概述了近年来科学工作者在提高肿瘤糖疫苗的免疫原性方面所做的努力: 半合成的肿瘤糖疫苗将糖抗原与蛋白共价连接, 已经有很多疫苗进入了临床试验; 随后发展的全合成的肿瘤糖疫苗将糖抗原、T细胞表位和内源性佐剂共价连接, 使疫苗的结构和组成更加确定; 基于细胞代谢糖工程的肿瘤糖疫苗将非天然的糖疫苗与细胞表面代谢糖工程相结合, 得到了强烈的免疫应答; 某些基于天然糖抗原结构修饰的疫苗产生的抗体也可以与天然糖抗原发生交叉反应, 这为肿瘤糖疫苗的发展提供了新的方向。     

Developments in cancer vaccination

The clinical application of cancer vaccines has progressed steadily from the rapid preclinical, technological advances of recent years. Cancer vaccine development has followed to some extent the pattern of vaccination for infectious disease, although features, such as the need to treat established disease in the face of immune evasion, vary. The necessity of conducting safety testing of new therapies in advanced cancer patients rather than in early-diagnosed patients often means that therapeutic benefit is seldom observed. Data that support even limited clinical efficacy are therefore encouraging. Initial approaches using whole irradiated tumor cells continue with some success, although there has been some refinement involving the use of tumor antigens and their subunits in a protein/peptide form (often via manipulated dendritic cells) or as DNA and RNA delivered naked or by viruses. Appropriate modes of boosting the immune system and immune conditioning appear important. Cancer vaccination research is likely to continue along many paths before any approaches become mainstream.     

Melanoma vaccines: prospects for the treatment of melanoma

A number of melanoma vaccines, made from whole melanoma cells or components of melanoma cells, are being tested in Phase II or III trials in patients after surgical removal of high risk primary or regional lymph node metastases, or in those with disseminated melanoma. During the progress of these trials, a number of melanoma antigens and their peptide epitopes that are recognised by human T-cells have been described. These findings and new information about antigen recognition by human T-cells have made it possible to explore the use of peptide epitopes targeted at T-cells as melanoma vaccines. Preliminary results are encouraging and suggest that it may soon be possible to use well defined vaccines, selected on the basis of the antigenic phenotype of the patient's melanoma and their HLA status. Equally exciting advances have been made preparing and using recombinant viral vectors containing genes that code for melanoma antigens. Experimental studies on the use of naked DNA as vaccines are also proceeding. Several fundamental obstacles preventing the effective use of T-cell epitope vaccines remain. These include selection of HLA and tumour antigen loss variants by the immune system, and conditioning of an ineffective immune response by the growing tumour. These aspects suggest that the development of effective vaccine therapy in the future may require a combination of strategies designed to stimulate HLA-restricted and -non-restricted effector cells, and judicious use of cytokines to obtain an effective immune response.     

Emerging melanoma vaccines

No satisfactory treatment currently exists for melanoma once it has spread beyond its original site. At present, the only FDA-approved treatment for advanced melanoma is IFN-alpha2b. Vaccines are an experimental therapy intended to stimulate the immune system to react more strongly against patients' own melanoma cells, thereby destroying the tumour or slowing its progression. Unfortunately, the exact tumour antigens that can stimulate an effective tumour-protective response in humans remain unknown. The approach that is increasingly followed to circumvent this problem is to prepare polyvalent vaccines containing a variety of melanoma antigens, as the greater the number of antigens in a vaccine, the greater the chance it will contain the correct antigen(s) to stimulate an antitumour response. Two recent randomised trials suggest that this approach results in vaccines that can be clinically effective. One is a double-blind, placebo-controlled trial of a polyvalent, shed antigen melanoma vaccine developed by Bystryn and licenced to NeoVac; the other is a larger randomised trial of Melacine (Corixa Corp.), a vaccine prepared from the lysate of two melanoma cell lines adjuvanted with Detox, which was developed by Mitchell and commercialized by Corixa. In both cases, tumour progression was delayed in the vaccine-treated patients, although in the latter trial, this was only observed in patients with certain human leukocyte antigen phenotypes. Several other vaccines are currently in Phase III trials, but the results of these trials are still pending. The major issues that need to be addressed are designing more effective melanoma vaccines with a mix of melanoma-associated antigens that can stimulate clinically beneficial antitumour immune responses, and finding an adjuvant that can safely, easily and powerfully boost the frequency and magnitude of these responses.     

Synthetic immunomodulators and synthetic vaccines

Efforts have been made for several years to obtain well-defined, nontoxic adjuvants and antigens which could be used for human vaccination and immunostimulation. Among synthetic adjuvants, MDP represents one of the most studied family of compounds. This molecule is the minimal active structure of whole Mycobacteria and has been shown to be endowed with numerous biological activities. MDP is adjuvant active, increases nonspecific resistance against infectious challenges and, under certain conditions, increases resistance against tumor grafts. Moreover, MDP has other pharmacological properties such as pyrogenic and somnogenic activities. Several hundred MDP derivatives have been synthetized and some of the biological activities have been dissociated. One MDP derivative presently under clinical trials has been shown to be adjuvant active but is devoid of pyrogenicity. The mechanisms of activity of these MDP and derivative molecules will be discussed. More recently, synthetic antigens which are copies of natural epitopes, have been shown to induce protective antibodies against bacterial or viral pathogens. These synthetic antigens conjugated to synthetic carriers or to synthetic adjuvants such as MDP, may permit the preparation of totally synthetic vaccines.     

Cancer vaccines,a critical review--Part II

Cancer vaccines have been explored clinically against melanomas, adenocarcinomas and lymphomas. Breast cancer vaccines include Theratope, MUC1 mucin peptides and HER-2/neu peptide vaccines. Phase II trials suggest prolongation of survival of advanced breast cancer patients who generate high titers of antibody to Theratope. In contrast, melanoma ganglioside vaccines, which also elicit only antibodies, have not been effective in improving survival in controlled trials. Anti-idiotype vaccines for solid tumors, which depend upon mimicry of the tumor-associated antigens, have also had limited success. In lymphomas, where the idiotypes are the tumor-associated antigens, greater success has been achieved. A number of tumor-associated antigens have been identified in melanoma, such as the lineage related cancer-testis group (MAGE) and tyrosinase-related antigens. Non-lineage related antigens shared among a variety of very different tumors have recently been demonstrated too, which may permit immunization against more than one tumor group. Telomerase and MG50, one of several interleukin-1 receptor antagonist molecules, are both immunogenic and widespread in their representation. Carcinoembryonic antigen is the basis for vaccines against many adenocarcinomas. Both viral and non-viral vectors are being used to improve the reactivity to peptides in adenocarcinomas. Dendritic cell-carried vaccines, which package the antigens ex vivo rather than depending upon in vivo uptake, are being extensively explored in clinical models to improve the effectiveness of defined vaccines, such as peptides and RNA. 'Naked' DNA vaccines injected intramuscularly also have their advocates. Among the most recent attempts to improve the immunogenicity of vaccines is the use of antigens newly identified by genomic techniques and 'superagonist' peptide mimics, selected from combinatorial peptide libraries. These modern biochemical and molecular biological methods may greatly expand our ability to immunize against tumor antigens, which are essentially 'self' molecules. Finally, a greater understanding of ways in which tumors escape immunological detection or thwart immunological responses should lead to improved strategies against the tumor to augment the effect of vaccination.     

Tumor cell-based vaccination in renal cell carcinoma: rationale. approaches,and recent clinical development

Since there is some evidence for spontaneous immunity against renal cell carcinoma, vaccination strategies are often used in patients with this tumor type, both in the adjuvant and the metastatic setting. Therefore, therapeutic strategies aim at augmenting anti-tumor immunity, but tumor-specific antigens suitable for vaccination purposes in renal cell carcinoma still remain to be identified. Early approaches used whole tumor cells or cell lysates with or without non-specific adjuvants like BCG. Studies investigating tumor cell vaccines have demonstrated immunological responses following vaccination, like positive cutaneous delayed hypersensitivity reactions indicating biological acitivity of tumor cell vaccines, and clinical responses have been observed as well. However, no clinical benefit has been demonstrated in randomized phase III trials. In recent years, efforts to develop more potent vaccines resulted in more sophisticated methods of tumor vaccination: The insertion of "neo-antigens" to enhance immunogenicity, the insertion of T-cell co-stimulatory molecules to enhance anti-tumor T-cell activation and the local production of cytokines to enhance T-cell function or the migration of antigen-presenting cells. Tumor cells have been genetically modified to express and produce cytokines, which in turn enhance the immunogenicity of the vaccine. The important role of dendritic cells has been recognized and tumor antigen-pulsed dendritic cells have been proposed. Hybrid cell vaccines are another promising approach. Safety and some effectiveness of these vaccines were demonstrated in phase I and II trials. However, randomized phase III trials are mandatory to confirm the usefulness of vaccination strategies. This review will describe the principals of tumor vaccination and, in a second part, focus on clinical studies of tumor vaccination in patients with renal cell carcinoma.     

Advances in prostate cancer immunotherapies

Prostate cancer is a major cause of mortality in men in the Western world. Although treatment of early stage prostate cancer with radiation therapy or prostatectomy is efficient in most cases, some patients develop a fatal hormone-refractory disease. Treatments in this case are limited to aggressive chemotherapies, which can reduce serum prostate-specific antigen (PSA) levels in some patients. Taxane- and platinum-compound-based chemotherapies produce a survival benefit of only a few months. Therefore, it is crucial to develop novel, well tolerated treatment strategies. Over the past years, immunotherapy of hormone-refractory prostate cancer has been studied in numerous clinical trials. The fact that the prostate is a non-essential organ makes prostate cancer an excellent target for immunotherapy. Administration of antibodies targeting the human epidermal growth factor receptor-2 or the prostate-specific membrane antigen led to stabilisation of PSA levels in several patients. Vaccination of prostate cancer patients with irradiated allogeneic prostate cell lines has demonstrated that whole cell-based vaccines can significantly attenuate increases in PSA. Two different recombinant viral expression vectors have been applied in prostate cancer treatment: poxvirus and adenovirus vectors. Both vaccines have the advantages of using a natural method to induce immune responses and achieving high levels of transgene expression. Vaccinia viruses in combination with recombinant fowlpox or canarypox virus have been used to express recombinant PSA. Several studies demonstrated that this approach is safe and can lead to stabilisation of PSA values. A very promising approach in prostate cancer immunotherapy is vaccination of patients with dendritic cells. Thereby, peptides, recombinant proteins, tumour lysates or messenger RNA have been used to deliver antigens to autologous dendritic cells. Loading of dendritic cells with up to five different peptides derived from multiple proteins expressed in prostate cancer demonstrated that cytotoxic T-cell responses could be elicited in prostate cancer patients. Sipuleucel-T (APC8015), an immunotherapy product consisting of antigen-presenting cells, loaded ex vivo with a recombinant fusion protein consisting of prostatic acid phosphatase linked to granulocyte-macrophage colony-stimulating factor, demonstrated in a phase III, placebo-controlled trial an improvement in median time to disease progression. The improvement in overall survival was 4.5 months for sipuleucel-T-treated patients compared with the placebo group. Although there is a minor increase in overall survival of metastatic prostate cancer patients with some approaches, more effective therapeutic strategies need to be developed.     

Induction of carbohydrate‐specific antibodies in HLA‐DR transgenic mice by a synthetic glycopeptide: a potential anti cancer vaccine for human use

Abstract: Over the last few years, anticancer immunotherapy has emerged as a new exciting area for controlling tumors. In particular, vaccination using synthetic tumor‐associated antigens (TAA), such as carbohydrate antigens hold promise for generating a specific antitumor response by targeting the immune system to cancer cells. However, development of synthetic vaccines for human use is hampered by the extreme polymorphism of human leukocyte‐associated antigens (HLA). In order to stimulate a T‐cell dependent anticarbohydrate response, and to bypass the HLA polymorphism of the human population, we designed and synthesized a glycopeptide vaccine containing a cluster of a carbohydrate TAA B‐cell epitope (Tn antigen: α‐GalNAc‐Ser) covalently linked to peptides corresponding to the Pan DR ‘universal’ T‐helper epitope (PADRE) and to a cytotoxic T lymphocyte (CTL) epitope from the carcinoembryonic antigen (CEA). The immunogenicity of the construct was evaluated in outbred mice as well as in HLA transgenic mice (HLA‐DR1, and HLA‐DR4). A strong T‐cell dependent antibody response specific for the Tn antigen was elicited in both outbred and HLA transgenic mice. The antibodies induced by the glycopeptide construct efficiently recognized a human tumor cell line underlying the biological relevance of the response. The rational design and synthesis of the glycopeptide construct presented herein, together with its efficacy to induce antibodies specific for native tumor carbohydrate antigens, demonstrate the potential of a such synthetic molecule as an anticancer vaccine candidate for human use.     

Design of peptide-based vaccines for cancer

The immune system responds efficiently to bacteria, viruses and other agents however, the immune response to cancers is not as effective. In most cases other than specific genetic rearrangements leading to non-self proteins such as in leukemia and idiotypes in lymphoma, tumor associated proteins are self proteins and are not recognized by the immune system to prevent malignancy. In most cancers, patients develop antibodies and/or CTL-precursors to tumor associated antigens but are not effective in generating a therapeutic immune response. Adjuvants have been used with either whole tumors, subunits or peptides with the aim of increasing their immunity. Whole tumor antigens have certain advantages associated with it, such as ready availability as recombinant proteins, potential epitopes that can be presented by a number of MHC class I/II alleles and antibody development. The methods of identification of CD8 and CD4 epitopes either by use of epitope prediction algorithms or use of transgenic mice has made the use of defined synthetic peptides more attractive. The possibility to synthesize long peptides and introduce multiple epitopes (CD4 or CD8) from single or multiple antigens makes peptide a viable alternative to whole proteins. As an alternative to totally synthetic peptide constructs or polymers, polytopes have been generated by genetic engineering methods. In addition, to deliver immunogens to and to activate DC, receptor-mediated delivery of peptides using antibodies, cytokines and carbohydrates have been used. This review will encompass the various strategies, preclinical and clinical applications in designing peptide-based vaccines for cancer.     

Active specific immunotherapy with autologous tumor cell vaccines for stage II colon cancer: logistics, efficacy, safety and immunological Pharmacodynamics

In the area of cancer treatment, immunotherapy with vaccines has suffered in the last five years, due to many clinical trial failures. One must keep in mind however, that many of the clinical trials conducted in the past decade were performed without the benefit of sound regulatory guidance or validated and compliant manufacturing processes. This has clearly been the case for patient specific, tumor cell vaccine therapy. The safety concerns that emanated within the regulatory agencies from the Somatic Cell Therapy concepts, translated to active specific immunotherapy with vaccines. Fortunately, in the past five years advances in understanding the immune system, improved design of clinical trials, improvement and compliance of manufacturing processes provided opportunities to significantly improve efficacy and safety. Clearly, the vaccine research establishment has learned the importance of not just selecting antigens but the requirement of tumor associated immunogens that can stimulate a functional immune response. Also, it has become clear that immunotherapy works best in situations of minimal residual disease. Finally, more realistic endpoints in clinical trials have been recognized and accepted by oversight review committees. This commentary describes the "trials and tribulations" of developing a patient specific, autologous tumor cell vaccine for therapy of Stage II colon cancer.     

Controlled trial of active immunotherapy in management of stage IIB malignant melanoma.

The prognosis for patients who undergo surgery for stage IIB malignant melanoma is poor. Animal studies have suggested that BCG and tumour cell vaccines given together may provide effective immunotherapy. To assess the effectiveness of this treatment 15 patients with stage IIB malignant melanoma who had their tumour excised were studied. Seven were treated conservatively, and eight were vaccinated with BCG and autologous irradiated cells. Three vaccinated patients suffered widespread recurrence within three months. All four vaccinated patients who suffered a recurrence within the first year died, while none of the three controls with recurrent disease died. In view of this alarming trend the trial was stopped after a year. BCG and the tumour cells may have enhanced the tumour growth, although there was no apparent reason for this. The results of uncontrolled or unrandomised trials that have suggested that this treatment is beneficial should be treated with scepticism.     

Vaccines against polysaccharide antigens

Encapsulated bacteria such as Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae serogroup B (Hib) are a major cause of disease worldwide. Vaccine development against these organisms has targeted their capsular polysaccharides (CPS), as anti-capsular antibodies often protect against disease. The capsular polysaccharide vaccines that have been available against these organisms are neither immunogenic nor protective in young children and certain immunocompromised individuals. In general, polysaccharide (PS) antigens elicit a T-independent immune response, characterized by lack of memory, and poor immunogenicity at the extremes of life. Efforts to overcome the poor immunogenicity of CPS vaccines have led to development of conjugate vaccines. By conjugating CPS to carrier proteins it is possible to induce a T-dependent immune response against these antigens. Although conjugate vaccines have been successful against Hib disease, their applicability to multi-serotype/serogroup pathogens like the pneumococcus or the meningococcus is questioned. As a result, alternative vaccines including (1) surface proteins conserved across serotypes/serogroups, (2) peptides that mimic PS antigens and (3) DNA vaccines are presently under investigation. This review will highlight the potential and limitations of both CPS and CPS-conjugate vaccines against encapsulated bacteria as well as alternative strategies against PS antigens.     

Whole cell ELISA for measuring anti-tumour effects of immunotherapies in a mouse tumour model of ALCL

The use of whole cell vaccines to augment anti-tumour immunity has been explored throughout the last century. Using the recently established TS1G6 ALCL mouse model, we compared the ability of whole cell vaccines with different combinations of CpG oligodeoxynucleotides, Diphteria-, Pertussis- and Tetanus-vaccine (DPT) to enhance the immunogenicity of tumour cells. We have therefore developed a whole cell ELISA that detects the systemic anti-tumor-cell antibody response. CpG oligodeoxy-nucleotides can induce production of different TH1-cytokines and stimulate immune effector cells. Diphteria-, Pertusis- and Tetanusvaccine, injected together with irradiated tumor cells into Diphteria-, Pertussis- and Tetanus-preimmunized mice were used to serve as a target for the host's existing memory response and thus enhance the immunogenicity of the tumour cells by induction of a local inflammation. The combined application of oligodeoxynucleotides, the vaccines and irradiated tumor cells into preimmunized mice quickly induced very high titers of tumour cell-specific antibody response. We conclude that this therapy may be a new attractive part of a tumour immunization strategy.     

Immune modulators with defined molecular targets: cornerstone to optimize rational vaccine design

Vaccination remains the most valuable tool for preventing infectious diseases. However, the performance of many existing vaccines should be improved and there are diseases for which vaccines are still not available. The use of well-defined antigens for the generation of subunit vaccines has led to products with an improved safety profile. However, purified antigens are usually poorly immunogenic, making essential the use of adjuvants. Despite the fact that adjuvants have been used to increase the immunogenicity of vaccines for more than 70 years, only a handful has been licensed for human use (e.g., aluminium salts, the micro-fluidized squalene-in-water emulsion MF59 and monophosphoryl lipid A). Thus, the development of new adjuvants which are able to promote broad and sustained immune responses at systemic and mucosal levels still remains as a major challenge in vaccinology. Recent advances in our understanding of the immune system have facilitated the identification of new biological targets for screening programs aimed at the discovery of novel immune stimulators. This resulted in the identification of new candidate adjuvants, which made possible the modulation of the immune responses elicited according to specific needs. A number of promising adjuvants which are currently under preclinical or clinical development will be described in this review.     

抗肿瘤DNA疫苗的研究近况

DNA疫苗技术在近十年来取得了显著的进步,而它在肿瘤预防和治疗领域的优势,使得抗肿瘤的DNA疫苗成为当前医药界的一个研究热点。文章主要介绍了一些作为DNA疫苗免疫靶点的肿瘤抗原,包括已经鉴定并进入临床试验研究和潜在的.可作为治疗靶点的肿瘤抗原,并着重介绍了如何解决由于肿瘤抗原作为一种自身抗原而导致的抗肿瘤DNA疫苗所面临的免疫原性较弱和抗肿瘤效果不理想这两个主要的问题.包括: 加入分子佐剂.主要是一些细胞因子而有效提高抗肿瘤DNA疫苗的免疫原性;通过使用与肿瘤抗原基因种属不同,但具有一定同源性的基因而打破肿瘤抗原的外周免疫耐受。最后主要从肿瘤疫苗免疫的靶点入手.介绍了能够有效增强DNA疫苗抗肿瘤作用的几种新的策略。     

Dendritic cells incubated with irradiated tumor cells effectively stimulate T lymphocyte activation and induce enhanced expression of CD69, CD25 as well as production of IFNgamma and IL4

Understanding of immunological processes at the molecular level in the cancer-bearing organism is the prerequisite for development of specific tumor vaccines. Most of these vaccines are aimed at enhancing the immunogenicity of the antigens presented by the tumor cells. Since dendritic cells (DC) are potent antigen presenting cells (APC) in the organism, they are considered as a powerful tool to deliver the signals essential for the activation of immune system. In an attempt to clarify the functional importance of DC in the process of anti-tumor vaccination, we characterized the effect of DC activated with a classical tumor vaccine (mixture of irradiated B16F1 tumor cells and MVE-2) on the activation of T lymphocytes. The T lymphocyte activation was assessed by determination of expression of CD25, CD69, and intracellular IFNgamma and IL4 production. Activated DC significantly increased the proportion of CD25+ and CD69+ cells as well as IFNgamma+ and IL4+ cells among CD3+ T lymphocytes. On the other hand, the direct effect of the tumor vaccine on T lymphocytes was just an increment in the proportion of IL4+ T lymphocytes. With the results of in vivo experiments, the phagocytic cells (including DC) were proved to be essential for establishing an active protection against tumor cells (tumor development), but more importantly, also for formation of the memory cell pool. These data indicate that DC loaded with tumor antigens are required for effective stimulation of T lymphocytes, and that the phagocytic cells (including DC) are essential for the anti-tumor immunity triggered by this kind of vaccine.