Synergy of vaccine strategies to amplify antigen-specific immune responses and antitumor effects

Several different vaccine strategies have been evaluated and combined in an attempt to amplify T-cell responses toward induction of antitumor immunity. The model tumor antigen used was carcinoembryonic antigen (CEA). While initial T-cell activation studies were conducted in conventional mice, combined vaccine strategy studies and antitumor studies were conducted in transgenic mice in which CEA is expressed in normal gastrointestinal tissue and CEA protein is found in sera. The studies reported here demonstrate: (a) A recombinant avipox (fowlpox, rF) vector expressing the signal 1 (CEA) and the B7-1 costimulatory molecule transgenes (designated rF-CEA/B7-1) is more potent in inducing CEA-specific T-cell responses than rF-CEA; one administration of recombinant fowlpox vector expressing CEA and three different costimulatory molecule transgenes (B7-1, ICAM-1, LFA-3, designated rF-CEA/TRICOM) was more potent in inducing CEA-specific T-cell responses than four vaccinations with rF-CEA or two vaccinations with rF-CEA/B7-1. Moreover, up to four vaccinations with rF-CEA/TRICOM induced greater CEA-specific T-cell responses with each vaccination. (b) A diversified prime and boost strategy using a prime with a recombinant vaccinia vector expressing CEA and the triad of costimulatory molecules (designated rV-CEA/TRICOM) and a boost with rF-CEA/TRICOM was more potent in inducing CEA-specific T-cell responses than the repeated use of rF-CEA/TRICOM alone. (c) The addition of granulocyte macrophage colony-stimulating factor (GM-CSF) to the rF-CEA or rF-CEA/TRICOM vaccinations via the simultaneous administration of a rF-GM-CSF vector enhanced CEA-specific T-cell responses. These strategies (TRICOM/diversified prime and boost/GM-CSF) were combined to treat CEA-expressing carcinoma liver metastases in CEA-transgenic mice; vaccination was initiated 14 days posttumor transplant. Antitumor effects in terms of survival and CD8(+) and CD4(+) responses specific for CEA were also observed in this CEA-transgenic mouse model. These studies demonstrate that the use of cytokines and diversified prime and boost regimens can be combined with the use of recombinant vectors expressing signal 1 and multiple costimulatory molecules to further amplify T-cell responses toward more effective vaccine strategies.     

Antitumor activity and immune responses induced by a recombinant carcinoembryonic antigen-vaccinia virus vaccine.

BACKGROUND: Human carcinoembryonic antigen (CEA) is a 180-kd glycoprotein expressed in human colorectal, gastric, pancreatic, breast, and non-small-cell lung carcinomas. Previous studies have demonstrated enhanced immune responses to other antigens presented with vaccinia virus proteins via a recombinant vaccinia virus construct. In addition, we have developed a recombinant CEA-vaccinia virus construct, designated rV(WR)-CEA, and have demonstrated humoral anti-CEA responses in mice after immunization with that virus. PURPOSE: The goals of this study were (a) to construct a recombinant CEA-vaccinia vaccine in a less virulent vaccinia strain that is potentially safe and effective for treatment of patients whose tumors express CEA and (b) to evaluate the ability of the recombinant CEA-vaccinia vaccine to prevent and reverse tumor growth in mice and to elicit cell-mediated and humoral anti-CEA immune responses. METHODS: Using the New York City strain of vaccinia virus, which is used in smallpox vaccination and is more attenuated for humans than rV(WR), we derived a recombinant CEA-vaccinia construct, designated rV(NYC)-CEA. The ability of this construct to induce antitumor immunity was evaluated in mice receiving subcutaneous injections of murine colon adenocarcinoma cells expressing the human CEA gene. RESULTS: Administration of rV(NYC)-CEA in mice induced strong anti-CEA antibody responses, as well as CEA-specific cell-mediated responses, including delayed-type hypersensitivity, lymphoproliferative, and cytotoxic responses. Vaccination of mice with the rV(NYC)-CEA rendered them resistant to the growth of subsequently transplanted CEA-expressing tumors. Moreover, when mice were vaccinated 7 days after tumor cell injection, tumor growth was either greatly reduced or eliminated. No toxic effects were observed in any of the mice. CONCLUSION: These studies demonstrate that antitumor activity can be induced with the use of a recombinant CEA-vaccinia virus construct derived from an attenuated vaccinia strain, and they reveal the range of cell-mediated and humoral responses induced by this recombinant vaccine.     

Ritonavir inhibits intratumoral docetaxel metabolism and enhances docetaxel antitumor activity in an immunocompetent mouse breast cancer model

Docetaxel (Taxotere^®) is currently used intravenously as an anticancer agent and is primarily metabolized by Cytochrome P450 3A (CYP3A). The HIV protease inhibitor ritonavir, a strong CYP3A4 inhibitor, decreased first‐pass metabolism of orally administered docetaxel. Anticancer effects of ritonavir itself have also been described. We here aimed to test whether ritonavir co‐administration could decrease intratumoral metabolism of intravenously administered docetaxel and thus increase the antitumor activity of docetaxel in an orthotopic, immunocompetent mouse model for breast cancer. Spontaneously arising K14cre;Brca1^F/F;p53^F/F mouse mammary tumors were orthotopically implanted in syngeneic mice lacking Cyp3a (Cyp3a^?/?) to limit ritonavir effects on systemic docetaxel clearance. Over 3 weeks, docetaxel (20 mg/kg) was administered intravenously once weekly, with or without ritonavir (12.5 mg/kg) administered orally for 5 days per week. Untreated mice were used as control for tumor growth. Ritonavir treatment alone did not significantly affect the median time of survival (14 vs. 10 days). Median time of survival in docetaxel‐treated mice was 54 days. Ritonavir co‐treatment significantly increased this to 66 days, and substantially reduced relative average tumor size, without altering tumor histology. Concentrations of the major docetaxel metabolite M2 in tumor tissue were reduced by ritonavir co‐administration, whereas tumor RNA expression of Cyp3a was unaltered. In this breast cancer model, we observed no direct antitumor effect of ritonavir alone, but we found enhanced efficacy of docetaxel treatment when combined with ritonavir. Our data, therefore, suggest that decreased docetaxel metabolism inside the tumor as a result of Cyp3a inhibition contributes to increased antitumor activity.     

Combination with bortezomib enhances the antitumor effects of nanoparticle-encapsulated thiostrepton

Bortezomib is well-known for inducing cell death in cancer cells, specifically through the mechanism of proteasome inhibition. Thiostrepton, a thiazole antibiotic, has also been described for its proteasome inhibitory action, although differing slightly to bortezomib in the proteasomal site to which it is active. Previously we had shown the synergic effect of bortezomib and thiostrepton in breast cancer cells in vitro, where sub-apoptotic concentrations of both proteasome inhibitors resulted in synergic increase in cell death when combined as a treatment. Here, we administered such a combination to MDA-MB-231 xenograft tumors in vivo, and found that the effect of complementary proteasome inhibitors reduced tumor growth rates more efficiently than compared with when administered alone. Increased induction of apoptotic activity in tumors was found be associated with the growth inhibitory activity of combination treatment. Further examination additionally revealed that combination-treated tumors exhibited reduced proteasome activity, compared with non-treated and single drug-treated tumors. These data suggest that this drug combination may be useful as a therapy for solid tumors.     

Synergistic enhancement of the antitumor activity of recombinant human TNF-alpha by recombinant human IFN-gamma

The effect of recombinant human interferon-gamma (rHu-IFN-gamma) on the antitumor activity of recombinant human tumor necrosis factor (rHu-TNF-alpha) was examined in vitro and in vivo. rHu-IFN-gamma enhanced both cytostatic and cytocidal activity of rHu-TNF-alpha against most rHu-TNF-alpha-sensitive tumor cells in vitro. However, there was no correlation between the degree of enhancement by rHu-IFN-gamma and that of the susceptibility of tumor cells to rHu-TNF-alpha. The enhancing effect of rHu-IFN-gamma was most marked when tumor cells were treated with rHu-IFN-gamma either for 1 day before treatment with rHu-TNF-alpha or for the first day of the exposure to rHu-TNF-alpha. A marked enhancing effect of rHu-IFN-gamma was also observed in the in vivo antitumor activity of rHu-TNF-alpha against HMV-2 melanoma. A combined treatment with rHu-TNF-alpha and rHu-IFN-gamma in a patient with papillary adenocarcinomas was shown to be much more effective than treatment with rHu-TNF-alpha alone. These results suggest that combined treatment with both agents will have better results in clinical trials.     

Vector-based vaccine/cytokine combination therapy to enhance induction of immune responses to a self-antigen and antitumor activity

Many antigens associated with human tumors are overexpressed in tumor cells as compared with normal tissues; these "self" tumor-associated antigens are also expressed during fetal development, and it is, thus, not surprising that they are either weakly immunogenic or functionally nonimmunogenic in the tumor-bearing host. In the studies reported here, we have used different vaccines and vaccine strategies in an attempt to develop antitumor immunity in a stringent animal model. The tumor antigen used was human carcinoembryonic antigen (CEA). The model used was CEA transgenic mice, in which the human CEA transgene is under the control of the endogenous CEA promoter; CEA is expressed in fetal tissues and normal gastrointestinal tissues, and CEA protein is found in sera. Previous studies have shown these CEA transgenic mice to be tolerant to the induction of CEA immunity using CEA protein in adjuvant as an immunogen. CEA-expressing tumor cells were implanted 14 days before vaccine therapy. The vaccines used were recombinant vaccinia virus containing the transgenes for CEA and three T-cell costimulatory molecules [B7-1, ICAM-1, and LFA-3, designated recombinant vaccinia (rV)-CEA/TRICOM], with each transgene under the control of individual poxvirus promoters, and a replication-defective avipox virus (fowlpox; rF) containing the same four transgenes (designated rF-CEA/TRICOM). The results demonstrate that (a) continued boosting with vaccine is required to maintain CEA-specific T-cell responses, and boosting with rF-CEA/TRICOM is superior to boosting with rF-CEA; (b) a diversified vaccination protocol consisting of primary vaccination with rV-CEA/TRICOM followed by boosting with rF-CEA/TRICOM is more efficacious than homogeneous vaccination with rF-CEA/TRICOM in the induction of both CEA-specific T-cell responses and antitumor activity; and (c) the use of cytokines, local granulocyte macrophage colony-stimulating factor (GM-CSF) and low-dose systemic interleukin 2, in combination with vaccine is essential in inducing antitumor activity, as compared with the use of cytokines alone, or the use of vaccines without cytokine. Both GM-CSF and interleukin 2 were shown to contribute to the induction of CEA-specific T-cell responses. These studies thus provide a "proof of concept" that potent vaccines and vaccine strategies, in combination with cytokines, may be essential to obtain the level of T-cell responses directed against a self-antigen that is necessary to achieve antitumor responses.     

Cancer‐associated fibroblast‐targeted strategy enhances antitumor immune responses in dendritic cell‐based vaccine

Given the close interaction between tumor cells and stromal cells in the tumor microenvironment (TME), TME‐targeted strategies would be promising for developing integrated cancer immunotherapy. Cancer‐associated fibroblasts (CAFs) are the dominant stromal component, playing critical roles in generation of the pro‐tumorigenic TME. We focused on the immunosuppressive trait of CAFs, and systematically explored the alteration of tumor‐associated immune responses by CAF‐targeted therapy. C57BL/6 mice s.c. bearing syngeneic E.G7 lymphoma, LLC1 Lewis lung cancer, or B16F1 melanoma were treated with an anti‐fibrotic agent, tranilast, to inhibit CAF function. The infiltration of immune suppressor cell types, including regulatory T cells and myeloid‐derived suppressor cells, in the TME was effectively decreased through reduction of stromal cell‐derived factor‐1, prostaglandin E₂, and transforming growth factor‐β. In tumor‐draining lymph nodes, these immune suppressor cell types were significantly decreased, leading to activation of tumor‐associated antigen‐specific CD8⁺ T cells. In addition, CAF‐targeted therapy synergistically enhanced multiple types of systemic antitumor immune responses such as the cytotoxic CD8⁺ T cell response, natural killer activity, and antitumor humoral immunity in combination with dendritic cell‐based vaccines; however, the suppressive effect on tumor growth was not observed in tumor‐bearing SCID mice. These data indicate that systemic antitumor immune responses by various immunologic cell types are required to bring out the efficacy of CAF‐targeted therapy, and these effects are enhanced when combined with effector‐stimulatory immunotherapy such as dendritic cell‐based vaccines. Our mouse model provides a novel rationale with TME‐targeted strategy for the development of cell‐based cancer immunotherapy.     

Combination of low-dose cisplatin and recombinant xenogeneic endoglin as a vaccine induces synergistic antitumor activities

Angiogenesis is critical to the growth and metastasis of solid tumors, and acquired drug resistance is one of the major hindrances to chemotherapy. Thus, we sought a rational strategy using the combination of antiangiogenic biotherapy and chemotherapy for cancer therapy. We explored the efficacy of a strategy combining low-dose cisplatin and a recombinant xenogeneic endoglin as a protein vaccine, which we previously demonstrated to have effective antiangiogenic effects in several mouse models. We found that both low-dosage cisplatin and xenogeneic endoglin vaccine individually resulted in effective suppression of tumor growth in 2 tumor models via inhibition of tumor angiogenesis. Remarkably, the combination therapy resulted in not only significant antiangiogenic effects but also additional promotion of tumor cell apoptosis and inhibition of tumor cell proliferation, without any ensuing increase in host toxicity during the course of treatment, which lasted for 6 months. In addition, the combination demonstrated a synergistic relationship, which was shown in all of the synergistic indexes, i.e., tumor volume, angiogenesis, apoptosis and proliferation. Both antibodies and antibody-producing B cells against mouse self-endoglin were observed in all mice immunized by the xenogeneic endoglin vaccine (alone and combination), which suggested that low-dose cisplatin did not suppress the host immune response but potentiated the antitumor activity of the xenogeneic endoglin vaccine. These observations may provide the basis for an effective alternative strategy for cancer therapy in the near future.     

卵巢癌抗独特型微抗体疫苗诱导BALB/c小鼠体内抗肿瘤免疫应答的实验研究

背景与目的：6B11抗独特型微抗体由模拟人卵巢癌抗原的抗独特型单链抗体(6B11ScFv)融合人IgG1铰链区和CH3区所构成,它具有6811ScFv和人1gGFc的双重免疫学活性。本研究观察6811抗独特型微抗体在BALB／c小鼠体内诱导抗肿瘤免疫反应情况,探讨其作为卵巢癌疫苗的可能性。方法：用卵巢癌6B11抗独特型微抗体免疫BALB／c小鼠。采用间接ELISA、竞争抑制实验和流式细胞术检测免疫鼠血清。结果：6B11抗独特型微抗体免疫小鼠后,在不用佐剂的情况下可诱导小鼠产生较高的Ab3,末次免疫后30天仍持续在较高的水平。分别在末次免疫后4天、14天、24天和30天可刺激小鼠脾脏淋巴细胞CD4^ T细胞和CD8^ T细胞明显升高。结论：6811抗独特型微抗体可诱导机体产生特异体液免疫和细胞免疫反应,这为抗独特型微抗体疫苗的临床应用提供了一定的实验依据。     

自噬对抗肿瘤免疫应答的影响

与细胞凋亡近似,自噬是一种重要的细胞生理反应.大量证据显示,自噬参与调控肿瘤发生、胚胎发育、组织重构等病理生理过程,更与免疫功能密切相关.免疫系统具有二重性,既能抑制又能促进肿瘤的发育进程.此外,自噬作为一种免疫系统效应器,已被证实参与天然免疫和获得性免疫过程.本文着重就自噬参与免疫反应分子机制方面的研究进展加以综述.     

Implications of aging and self-tolerance on the generation of immune and antitumor immune responses

Cancer statistics show a disproportionately higher burden of tumors in the old. Most of the studies evaluating vaccination strategies have not taken into consideration the effect that aging has on the immune system. For the first time, we describe an animal tumor model in which self-tolerance and aging are present at the same time. FVB-Her-2/neu mice which are tolerant to neu antigens crossed with HLA-A2/Kb mice (A2xneu) develop spontaneous tumors when they are more than 22 months old. Analysis of CD8(+) T-cell-specific responses in A2xneu mice indicated that the priming activity of old A2xneu mice to induce an immune response was diminished compared with young animals. Following intratumoral injections of CpG-ODN, approximately 30% of young A2xneu mice rejected the tumor; however, no antitumor effect was observed in old A2xneu mice. Analysis of T regulatory cells (Treg) indicated that there are significantly more Tregs in old animals. After CpG-ODN vaccination plus Treg depletion, 70% of young A2xneu mice rejected the tumor. The same treatment prolonged survival in old A2xneu mice, but none of the animals rejected the tumor. Even though CpG-ODN injections plus Treg depletion could rescue the antitumor responses against self-tumor antigens in young tolerant mice, the same therapy is not as effective in old tolerant hosts. Relevant tumor models such as the A2xneu mice in which self-tolerance and aging are present at the same time are critical to allow the optimization of vaccination strategies to effectively stimulate immune responses against self-tumor antigens in the young and the old.     

Specific cytolytic T-cell responses to human CEA from patients immunized with recombinant avipox-CEA vaccine.

Avipox viruses are replication-defective members of the poxvirus family. Avipox-derived vectors such as ALVAC (canarypox) and fowlpox have the ability to infect mammalian cells, including human cells, but do not replicate. The first clinical trial of an avipox recombinant vaccine for patients with advanced carcinomas has recently been conducted using the ALVAC vector and the human carcinoembryonic antigen (CEA) transgene (designated ALVAC-CEA; J. L. Marshall et al, J. Clin. Oncol., 17: 332-337, 1999). The T-cell responses elicited by patients before and after vaccination with the ALVAC-CEA recombinants are characterized in this report. Pre- and postvaccination peripheral blood mononuclear cells (PMBCs) of the eight patients positive for HLA-class I A2 allele, were incubated with the HLA-A2-CEA peptide CAP-1 and interleukin 2. In no cases using prevaccination PMBCs could cultures be established that had the ability to lyse C1R-A2 target cells pulsed with the CAP-1 peptide. However, T-cell cultures from seven of eight of these same patients, obtained from PBMCs after ALVAC-CEA vaccination, were shown to lyse C1R-A2 cells only when pulsed with CAP-1. Moreover, all seven of these T-cell cultures were shown to lyse allogeneic human carcinoma cell lines (SW1463 and SW480) that were both A2+ and expressed CEA; an allogeneic tumor cell line (LS174T) expressing CEA that was negative for A2 expression was not lysed. HLA-A2+ and CEA+ autologous tumor cells were also capable of being lysed by CEA-specific T cells from this patient. Analysis of this CTL line also revealed the expression of several homing and adhesion-associated molecules. Fluorescence-activated cell sorter analysis of the T-cell lines established from patients after ALVAC-CEA vaccination revealed that most were CD8+/CD4-, but many also had a CD8+/CD4+ component. Analyses of T-cell receptor Vbeta usage of several of the CEA-specific CTL lines showed a relatively diverse Vbeta pattern. These studies demonstrate for the first time the ability to vaccinate cancer patients with an avipox recombinant and derive T cells that are capable of lysing allogeneic and autologous tumor cells in a MHC-restricted manner. These studies thus form the rationale to use such replication-deficient recombinant vaccines in future cancer vaccine trials.     

顺铂预处理化疗通过免疫调节增强CIK细胞对B16恶性黑色素瘤的抑制作用

目的 观察顺铂( Cisplatin,DDP)预处理化疗联合CIK细胞对B16恶性黑色素瘤的抑制作用,探讨DDP预处理化疗增强细胞因子诱导的杀伤细胞(cytokine - induced killer cells,CIK cells)抑瘤作用的潜在机制.方法 建立C57BL/6小鼠B16黑色素瘤模型,测量肿瘤体积,绘制...     

Combination of tumor site-located CTL-associated antigen-4 blockade and systemic regulatory T-cell depletion induces tumor-destructive immune responses

Accumulating data indicate that tumor-infiltrating regulatory T cells (Treg) are present in human tumors and locally suppress antitumor immune cells. In this study, we found an increased Treg/CD8 ratio in human breast and cervical cancers. A similar intratumoral lymphocyte pattern was observed in a mouse model for cervical cancer (TC-1 cells). In this model, systemic Treg depletion was inefficient in controlling tumor growth. Furthermore, systemic CTL-associated antigen-4 (CTLA-4) blockade, an approach that can induce tumor immunity in other tumor models, did not result in TC-1 tumor regression but led to spontaneous development of autoimmune hepatitis. We hypothesized that continuous expression of an anti-CTLA-4 antibody localized to the tumor site could overcome Treg-mediated immunosuppression and locally activate tumor-reactive CD8+ cells, without induction of autoimmunity. To test this hypothesis, we created TC-1 cells that secrete a functional anti-CTLA-4 antibody (TC-1/alphaCTLA-4-gamma1 cells). When injected into immunocompetent mice, the growth of TC-1/alphaCTLA-4-gamma1 tumors was delayed compared with control TC-1 cells and accompanied by a reversion of the intratumoral Treg/CD8 ratio due to an increase in tumor-infiltrating IFNgamma-producing CD8+ cells. When local anti-CTLA-4 antibody production was combined with Treg inhibition, permanent TC-1 tumor regression and immunity was induced. Importantly, no signs of autoimmunity were detected in mice that received local CTLA-4 blockade alone or in combination with Treg depletion.     

Modulation of antitumor immune responses by hematopoietic cytokines

BACKGROUND: Advances in immunotherapy for the treatment of patients with malignant disease have led to increasingly successful use of these methods in the clinical setting. This review presents findings from recent studies that have explored improved methods for the presentation of tumor-associated antigens and for the restoration of tumor specific immune responses using cytokine therapy. METHODS: A review of human clinical trial research on immune cytokines from 1995 (MEDLINE) to the present was conducted. Particular attention was focused on articles that reported results from Phase II or later clinical studies in patients with malignant disease. RESULTS: The defects in cellular immunity commonly seen in patients with malignancies often are expressed as tumor specific anergy. Reversing patient tolerance to tumor antigens may be accomplished by treatment with immunoregulatory cytokines, such as Flt-3 and granulocyte-macrophage-colony stimulating factor, that mature and activate dendritic cells. Published clinical studies indicate that granulocyte-macrophage-colony stimulating factor stimulates antigen-presenting cells and has promising antitumor activity as an adjunct or as stand-alone therapy for patients with malignant disease, including leukemia, melanoma, breast carcinoma, prostate carcinoma, and renal cell carcinoma. CONCLUSIONS: Immune-modulating cytokines may be used alone or in combination with other treatments to help restore immune function, improve response to tumor-associated antigens, and reduce the toxic effects of standard antitumor therapies. The evolving understanding of how dendritic cells regulate immune responses and promising results from published studies of immune-enhancing cytokines in the treatment of patients with malignant disease support the conduct of randomized clinical trials to confirm the clinical benefit of these immunotherapeutic strategies.     

重组人淋巴毒素抗肿瘤作用的研究

目的：探讨重组人淋巴毒素体内外抗肿瘤作用。方法：体外采用ＭＴＴ法测ｒｈＬＴ对人胃癌细胞ＭＫＮ－４５的细胞毒作用,体内采用小鼠移植性肿瘤研究其抗肿瘤活性。结果：ｒｈＬＴ对体外培养的ＭＫＮ－４５有较强的细胞毒作用,其ＩＣ５０为１．９８×１０＾－２μｇ／ｍｌ,ｒｈＬＴ对小鼠体内移植的Ｓ１８０实体瘤和小鼠Ｅｈｒｌｉｃｈ氏实体瘤均有一定的抑制作用,其抑制率分别为３４．１３％和３４．０８％;     

趋化肽fMLP增强博安霉素的抗肿瘤作用

背景和目的:博安霉素(Boanmycin,BAM)是博来霉素的A6组分,临床研究表明对多种肿瘤有效。趋化肽可吸引与激活白细胞(含巨噬细胞),使其对肿瘤生长、侵袭与转移过程产生一定的影响。本研究探讨BAM和趋化肽fMLP(N-formyl-methionyl-leucyl-phenylalanine,CHO-Met-Ile-Phe)联合抗肿瘤作用。方法:体外采用MTT法测定BAM和fMLP联合对肿瘤细胞的细胞毒作用,尤其是巨噬细胞存在时的作用。体内实验以小鼠移植性肝癌H22模型观察BAM和fMLP联合抗肿瘤作用。结果:体外实验,BAM与fMLP联合对肿瘤细胞没有协同作用,但BAM10μg/ml、30μg/ml和100μg/ml与fMLP20μg/ml联合在加入巨噬细胞后对肿瘤细胞有显著协同作用。体内实验时,fMLP1mg/mouse为瘤周给药×3,fMLP无显著抗肿瘤作用。BAM和fMLP合用时设计了3个实验:(1)肿瘤接种后24h开始治疗,BAM为瘤周给药×3,BAM0.5mg/kg在13天的抑瘤率为26.6%,合用fMLP后为64.7%,P<0.05,CDI值为0.36,有显著协同作用。(2)肿瘤接种后24h开始治疗,BAM为腹腔给药×3,BAM1mg/kg组肿瘤生长较快,合用fMLP后生长缓慢。在14天的抑瘤率为11%,合用fMLP后为70.6%,P<0.05,CDI为0.42,有显著协同作用。(3)肿瘤接种后96h开始治疗,BAM腹腔给药×3,BAM1mg/kg组肿瘤生长较快,合用fMLP后生长缓慢。在13天的抑瘤     

Combination of low-dose gemcitabine and recombinant quail vascular endothelial growth factor receptor-2 as a vaccine induces synergistic antitumor activities

Vascular endothelial growth factor receptor-2 (VEGFR-2) has been shown to play a major role in inducing the full spectrum of VEGF biological response which is essential for tumor angiogenesis. We have demonstrated that immunotherapy of tumors with a vaccine based on quail homologous VEGFR-2 (qVEGFR) was effective in providing both protective and therapeutic antitumor immunity in several tumor models in mice. The purpose of this study was to determine whether the combination therapy of low-dose gemcitabine with qVEGFR as a vaccine could inhibit tumor growth to a greater extent. To test this concept, H22 hepatoma and Lewis lung carcinoma models were established in BALB/c mice and C57BL/6 mice, respectively. Mice were treated with either qVEGFR as a protein vaccine, gemcitabine, or both agents together. qVEGFR or low-dose chemotherapy treatment individually resulted in tumor inhibition to a certain extent.Remarkably, the combination therapy resulted in synergistic antitumor activity. Histological examination revealed that there was endothelial deposition of immunoglobulins within tumor tissues from mice treated with vaccine or combination therapy, especially intratumor angiogenesis was suppressed more significantly for the combination group. Also, ELISPOT analysis showed that mice treated with either qVEGFR alone or in combination with low-dose chemotherapy produced similar amount of anti-VEGFR antibody-producing B cells, which suggested that low-dose gemcitabine did not suppress the host's immune response, but potentiated the antitumor activity of the qVEGFR vaccine. Furthermore, TUNEL staining demonstrated a significant increase in the number of TUNEL-positive cells in the combination group compared with those of other groups. The observations may provide a new bio-chemotherapeutic approach for cancer.     

Vaccination with a recombinant Saccharomyces cerevisiae expressing a tumor antigen breaks immune tolerance and elicits therapeutic antitumor responses

PURPOSE: Saccharomyces cerevisiae, a nonpathogenic yeast, has been used previously as a vehicle to elicit immune responses to foreign antigens, and tumor-associated antigens, and has been shown to reduce tumor burden in mice. Studies were designed to determine if vaccination of human carcinoembryonic antigen (CEA)-transgenic (CEA-Tg) mice (where CEA is a self-antigen) with a recombinant S. cerevisiae construct expressing human CEA (yeast-CEA) elicits CEA-specific T-cell responses and antitumor activity. EXPERIMENTAL DESIGN: CEA-Tg mice were vaccinated with yeast-CEA, and CD4(+) and CD8(+) T-cell responses were assessed after one and multiple administrations or vaccinations at multiple sites per administration. Antitumor activity was determined by tumor growth and overall survival in both pulmonary metastasis and s.c. pancreatic tumor models. RESULTS: These studies demonstrate that recombinant yeast can break tolerance and that (a) yeast-CEA constructs elicit both CEA-specific CD4(+) and CD8(+) T-cell responses; (b) repeated yeast-CEA administration causes increased antigen-specific T-cell responses after each vaccination; (c) vaccination with yeast-CEA at multiple sites induces a greater T-cell response than the same dose given at a single site; and (d) tumor-bearing mice vaccinated with yeast-CEA show a reduction in tumor burden and increased overall survival compared to mock-treated or control yeast-vaccinated mice in both pulmonary metastasis and s.c. pancreatic tumor models. CONCLUSIONS: Vaccination with a heat-killed recombinant yeast expressing the tumor-associated antigen CEA induces CEA-specific immune responses, reduces tumor burden, and extends overall survival in CEA-Tg mice. These studies thus form the rationale for the incorporation of recombinant yeast-CEA and other recombinant yeast constructs in cancer immunotherapy protocols.