Avian adenovirus vector CELO-TK displays anticancer activity in human cancer cells and suppresses established murine melanoma tumors

Avian adenovirus CELO is a novel adenovirus vector system with the advantages of efficient production, high virion stability, and the absence of crossreactivity with Ad5-neutralizing antibodies. In this study, we evaluated the anticancer efficacy of a CELO vector encoding the herpes simplex virus type 1 thymidine kinase, a prodrug-activating therapeutic gene. Vectors carrying the gene for HSV-tk or EGFP under the control of the HCMV promoter in place of the "nonessential" region of the CELO genome were constructed. Anticancer activity of the CELO-TK vector was studied in vitro, in human and murine tumor cells in cell culture, and in vivo, in established subcutaneous murine B16 melanoma tumors in C57BL/6 mice. The CELO-TK vector mediated delivery of functional HSV-tk to tumor cell lines in cell culture. Comparison of the CELO-TK vector to a first-generation human adenovirus type 5 vector Ad5-TK in cultured H1299 cells showed equal levels of functional activity at increasing multiplicities of infection with CELO-based vector. CELO vectors allowed for transduction and expression of EGFP and HSV-tk genes in subcutaneous melanoma tumors in C57BL/6 mice. Intratumoral injections of CELO-TK followed by ganciclovir administration resulted in suppression of tumor growth and significantly increased the median of survival. The results of the study demonstrated the efficacy of CELO vector as a vehicle for the delivery of prodrug-activating genes such as HSV-tk to tumor cells in vitro and in vivo.     

人AFP腺病毒载体感染的树突状细胞诱导小鼠抗肝癌免疫

目的探讨复制缺损型腺病毒载体(Ad)介导异种AFP修饰的树突状细胞(DCs)诱发抗肝癌免疫、打破肿瘤免疫耐受的效果。方法从HepG2和Hepa16细胞中克隆人和小鼠AFP,插入Ad中构建AdhAFP和AdmAFP。用AdhAFP或AdmAFP感染小鼠骨髓来源的DC后,在无或有删除CD4或CD8情况下免疫C57BL/6小鼠,7d后取脾细胞行51Cr释放实验,检测特异性CTL杀伤活性;或给免疫小鼠接种Hepa16肝癌细胞,观察荷瘤小鼠成活情况。结果AdhAFP/DCs免疫小鼠1周后其细胞毒性T淋巴细胞杀伤活性明显强于AdmAFP/DCs。AdhAFP/DCs免疫小鼠后1周接种5×106Hepa16肝瘤细胞,2个月后仍然有80%的小鼠无瘤生长;而接种1×106Hepa16细胞至AdmAFP/DCs免疫小鼠,2个月后小鼠成活率为20%。删除小鼠CD4或CD8T细胞均使AdhAFP/DCs诱发的抗肿瘤免疫反应消失。结论Ad介导异种AFP修饰的DCs能有效地打破肿瘤的免疫耐受,诱发强烈的抗原特异性细胞免疫反应,这种特异性细胞免疫反应是CD4和CD8依赖性的。     

Anti-4-1BB antibody-based combination therapy augments antitumor immunity by enhancing CD11c+CD8+ T cells in renal cell carcinoma

To improve the potential treatment strategies of incurable renal cell carcinoma (RCC), which is highly resistant to chemotherapy and radiotherapy, the present study established a combination therapy with immunostimulatory factor (ISTF) and anti-4-1BB monoclonal antibodies (mAbs) to augment the antitumor response in a murine RCC model. ISTF isolated from Actinobacillus actinomycetemcomitans stimulates macrophages, dendritic cells and B cells to produce IL-6, TNF-α, nitric oxide and major histocompatibility complex class II expression. 4-1BB (CD137) is expressed in activated immune cells, including activated T cells, and is a promising target for cancer immunotherapy. The administration of anti-4-1BB mAbs promoted antitumor immunity via enhancing CD11c⁺CD8⁺ T cells. The CD11c⁺CD8⁺ T cells were characterized by high killing activity and IFN-γ-producing ability, representing a phenotype of active effector cytotoxic T lymphocytes. The present study showed that combination therapy with ISTF and anti-4-1BB mAbs promoted partial tumor regression with established RCC, but monotherapy with ISTF or anti-4-1BB mAbs did not. These effects were speculated to be caused by the increase in CD11c⁺CD8⁺ T cells in the spleen and tumor, and IFN-γ production. These insights into the effector mechanisms of the combination of ISTF and anti-4-1BB mAbs may be useful for targeting incurable RCC.     

An Ad5[E1-, E2b-]-HER2/neu vector induces immune responses and inhibits HER2/neu expressing tumor progression in Ad5 immune mice

Immunotherapy is a promising approach for the treatment of cancers. Modified adenovirus 5 (Ad5) vectors have been used as a platform to deliver genes encoding tumor associated antigens (TAA). A major obstacle to Ad5 vector immunotherapy has been the induction of vector immunity following administration or the presence of pre-existing Ad5 immunity, which results in vector mitigation. It has been reported by us that the Ad5[E1-, E2b-] platform with unique deletions in the E1, E2b and E3 regions can induce potent cell mediated immunity (CMI) against delivered transgene products in the presence of pre-existing Ad5 immunity. Here we report the use of an Ad5[E1-, E2b-] vector platform expressing the TAA HER2/neu as a breast cancer immunotherapeutic agent. Ad5[E1-, E2b-]-HER2/neu induced potent CMI against HER2/neu in Ad5 na?ve and Ad5 immune mice. Humoral responses were also induced and antibodies could lyse HER2/neu expressing tumor cells in the presence of complement in vitro. Ad5[E1-, E2b-]-HER2/neu prevented establishment of HER2/neu-expressing tumors and significantly inhibited progression of established tumors in Ad5 na?ve and Ad5 immune murine models. These data demonstrate that in vivo delivery of Ad5[E1-, E2b-]-HER2/neu can induce anti-TAA immunity and inhibit progression of HER2/neu expressing cancers.     

Mechanisms involved in synergistic anticancer immunity of anti-4-1BB and anti-CD4 therapy

Anti-4-1BB-mediated anticancer effects were potentiated by depletion of CD4+ cells in B16F10 melanoma-bearing C57BL/6 mice. Anti-4-1BB induced the expansion and differentiation of polyclonal tumor-specific CD8+ T cells into IFN-gamma-producing CD11c+CD8+ T cells. The CD4+ cell depletion was responsible for facilitating immune cell infiltration into tumor tissues and removing some regulatory barriers such as T regulatory and indoleamine-2,3-dioxygenase (IDO)+ dendritic cells. Both monoclonal antibodies (mAb) contributed to the efficient induction of MHC class I molecules on the tumor cells in vivo. The effectors that mediated the anti-4-1BB effect were NKG2D+KLRG1+CD11c+CD8+ T cells that accumulated preferentially in the tumor tissues. Blocking NKG2D reduced the therapeutic effect by 20% to 26%, which may indicate that NKG2D contributes partially to tumor killing by the differentiated CD8+ T cells. Our results indicate that the combination of the two mAbs, agonistic anti-4-1BB and depleting anti-CD4, results in enhanced production of efficient tumor-killing CTLs, facilitation of their infiltration, and production of a susceptible tumor microenvironment.     

Tumor Necrosis Factor α-Gene Therapy for an Established Murine Melanoma Using RGB (Arg-Gly-Asp) Fiber-mutant Adenovirus Vectors

Although adenovirus vectors (Ad) provide high-level transduction efficacy to many cell types, extremely high doses of Ad are required for sufficient gene transduction into several tumors, including melanoma. Here, we demonstrated that the expression of coxsackie-adenovirus receptor, a primitive Ad-receptor, was very low in murine and human melanoma cells. We also found that fiber-mutant Ad containing the Arg-Gly-Asp (RGD) sequence in the fiber knob remarkably augmented gene transduction efficacy in melanoma cells by targeting α_v-integrins. In addition, intratumoral injection of RGD fiber-mutant Ad containing the tumor necrosis factor α gene (AdRGD-TNFα) revealed dramatic anti-tumor efficacy through hemolytic necrosis in an established murine B16 BL6 melanoma model. Ad-RGD-TNFα required one-tenth the dosage of Ad-TNFα to induce an equal therapeutic effect. These results suggest that α_v-integrin-targeted Ad will be a very powerful tool for the advancement of melanoma gene therapy.     

Tumor necrosis factor alpha-gene therapy for an established murine melanoma using RGD (Arg-Gly-Asp) fiber-mutant adenovirus vectors.

Although adenovirus vectors (Ad) provide high-level transduction efficacy to many cell types, extremely high doses of Ad are required for sufficient gene transduction into several tumors, including melanoma. Here, we demonstrated that the expression of coxsackie-adenovirus receptor, a primitive Ad-receptor, was very low in murine and human melanoma cells. We also found that fiber-mutant Ad containing the Arg-Gly-Asp (RGD) sequence in the fiber knob remarkably augmented gene transduction efficacy in melanoma cells by targeting alpha(v)-integrins. In addition, intratumoral injection of RGD fiber-mutant Ad containing the tumor necrosis factor alpha gene (Ad-RGD-TNFalpha) revealed dramatic anti-tumor efficacy through hemolytic necrosis in an established murine B16 BL6 melanoma model. Ad-RGD-TNFalpha required one-tenth the dosage of Ad-TNFalpha to induce an equal therapeutic effect. These results suggest that alpha(v)-integrin-targeted Ad will be a very powerful tool for the advancement of melanoma gene therapy.     

Adoptive transfer of immunity induced by semi-allogeneic hybrid cells,against a murine fibrosarcoma

Semi-allogeneic somatic hybrid cells derived from the fusion of a C57BL/6 fibrosarcoma (MCB6–1) and A9 cells (C3H origin) were used to immunize C57BL/6 mice against the parental tumor cells. These hybrid cells expressed H-2 histocompatibility antigens of both parental cells (H-2_b and H-2^k), and failed to produce tumors in normal C57BL/6 mice. A single i.p. injection of hybrid cells induced anti-tumor immunity which could be transferred to normal C57BL/6 recipient mice by immune spleen or peritoneal cells; the efficient cells were T cells, as this activity was completely abrogated by treatment with anti-Thy-1–2 antiserum and complement. Among immune splenic T cells, only the light-density T cells, obtained after fractionation on Percoll gradient, were effective in the transfer of immunity. Immunity induced by the hybrid cells was specific for MCB6-1 parental tumor cells. This immunity could be transferred during two brief periods, 7 to 12 days, and 40 to 50 days, after hybrid cell injection; there appeared to be an intermediate period, 12 to 40 days after immunization, during which no immunity could be transferred. These results suggest a suppressive mechanism implicated during hybrid cell immunization and interacting with the anti-tumor immune response.     

Ad介导人AFP和IFN-у协同诱发抗小鼠肝癌免疫效应

背景与目的:原发性肝癌(hepatocellular carcinoma,HCC)是常见的恶性肿瘤之一,目前对HCC的治疗尚无行之有效的手段。本研究探讨腺病毒(Adenovirus,Ad)载体介导异种甲胎蛋白(Alpha-fetoprotein,AFP)和酌干扰素(Interferon-gamma,IFN-γ酌)的协同抗肝癌效应。方法:用RT-PCR(reverse transcri-ptase-polymerase chain reaction)方法克隆小鼠IFN-γ酌基因并构建复制缺损型腺病毒编码人AFP和小鼠IFN-γ酌联合表达载体(Ad-hAFP/IFN-γ酌)。皮内免疫C57BL/6小鼠7d后,取脾细胞行51Cr释放实验检测特异性细胞毒T淋巴细胞(Cytotoxic Tlymphocytes,CTLs)杀伤活性;或给免疫小鼠皮下接种Hepa1-6肝癌细胞,观察荷瘤小鼠成活情况。结果:51Cr释放实验显示,Ad-hAFP/IFN-γ酌免疫小鼠1周后其诱导产生的特异性CTL杀伤活性明显强于Ad-hAFP或Ad-IFN-γ酌单独免疫,在效∶靶比(E∶T)为10∶1时,Ad-hAFP/IFN-γ酌、Ad-hAFP和Ad-IFN-γ酌诱发的CTL杀伤率分别(43.8±5.5)%、(28.2±3.2)%和(12.8±1.9)%;30∶1时,为(79.6±6.4)%、(51.9±4.3)%和(15.6±2.3)%以及90∶1时(88.2±6.3)%、(62.5±4.8)%和(26.5±2.4)%。荷瘤试验表明,Ad-hAFP或Ad-IFN-γ酌单独免疫小鼠后1周接种5×106Hepa1-6肝瘤细胞,观察2个月,Ad-hAFP免疫组80%的小鼠荷瘤,Ad-IFN-γ酌免疫组小鼠则100%荷瘤;而Ad-hAFP/IFN-γ酌免疫小鼠在接种同样数量的Hepa1-6细胞,2个月无小鼠荷瘤,小鼠100%存活。结论:腺病毒载体介导异种AFP能有效地诱发针对小鼠AFP的特异性细胞免疫反应,IFN-γ酌能明显增强这种效应。     

Polarization effects of 4-1BB during CD28 costimulation in generating tumor-reactive T cells for cancer immunotherapy

Using murine tumor-draining lymph node (TDLN) cells, we investigated the polarization effect of 4-1BB (CD137) during CD28 costimulation in generating antitumor T cells. Costimulation of TDLN cells through the newly induced 4-1BB molecules, CD3, and CD28 using monoclonal antibodies significantly enhanced cell proliferation. The greater cell yield with 4-1BB signaling appeared to be related to the inhibition of activation-induced cell death. Activation of TDLN cells through 4-1BB in addition to CD3/CD28 signaling shifted T-cell responses toward a type 1 cytokine pattern because 4-1BB ligation plus CD3/CD28 stimulation significantly augmented type 1 cytokine (e.g., IFN-gamma) and granulocyte macrophage colony-stimulating factor secretion. By contrast, type 2 cytokine (e.g., interleukin 10) secretion by the activated TDLN cells was significantly reduced. The in vivo antitumor reactivity of TDLN cells activated through 4-1BB in conjunction with CD3/CD28 pathways was examined using an adoptive immunotherapy model. The number of pulmonary metastases was significantly reduced and survival was prolonged after the transfer of anti-CD3/anti-CD28/anti-4-1BB-activated TDLN cells compared with an equivalent number of cells activated without anti-4-1BB. The antitumor effect through 4-1BB involvement during CD28 costimulation was dependent on IFN-gamma production and abrogated after IFN-gamma neutralization. By contrast, interleukin 10 neutralization resulted in significantly enhanced tumor regression. These results indicate that costimulation of TDLN cells through newly induced 4-1BB and CD3/CD28 signaling can significantly increase antitumor reactivity by shifting T-cell responses toward a type 1 cytokine pattern while concomitantly decreasing type 2 responses.     

Translational strategies exploiting TNF-alpha that sensitize tumors to radiation therapy

TNFerade is a radioinducible adenoviral vector expressing tumor necrosis factor-alpha (TNF-alpha) (Ad.Egr-TNF) currently in a phase III trial for inoperable pancreatic cancer. We studied B16-F1 melanoma tumors in TNF receptor wild-type (C57BL/6) and deficient (TNFR1,2-/- and TNFR1-/-) mice. Ad.Egr-TNF+IR inhibited tumor growth compared with IR in C57BL/6 but not in receptor-deficient mice. Tumors resistant to TNF-alpha were also sensitive to Ad.Egr-TNF+IR in C57BL/6 mice. Ad.Egr-TNF+IR produced an increase in tumor-associated endothelial cell apoptosis not observed in receptor-deficient animals. Also, B16-F1 tumors in mice with germline deletions of TNFR1,2, TNFR1 or TNF-alpha, or in mice receiving anti-TNF-alpha exhibited radiosensitivity. These results show that tumor-associated endothelium is the principal target for Ad.Egr-TNF radiosensitization and implicate TNF-alpha signaling in tumor radiosensitivity.     

Anti-4-1BB monoclonal antibody enhances rejection of large tumor burden by promoting survival but not clonal expansion of tumor-specific CD8+ T cells

Anti-4-1BB monoclonal antibody (mAb) has been shown to induce antitumor immunity by a CD4/CD8-dependent mechanism, but its direct effect on tumor-specific CD8+ T cells in tumor rejection is unclear. Here we used transgenic CD8+ T cells against the unmutated tumor rejection antigen P1A to analyze whether this mAb can promote CD8+ T-cell function against large tumors in the absence of CD4+ T-helper cells. RAG-2(-/-) mice were challenged with P1A-expressing plasmacytoma J558. Once tumor size reached a diameter of 0.85-1.75 cm, mice were treated with P1A-specific CD8+ CTL (P1CTL) in conjunction with anti-4-1BB mAb or control IgG. All of the mice showed a partial regression of tumor, but mice treated with anti-4-1BB mAb exhibited markedly enhanced tumor rejection, delayed tumor progression, and prolonged survival. Correspondingly, we observed a substantial increase in the number of P1CTL in anti-4-1BB mAb-treated mice. Surprisingly, anti-4-1BB mAb did not accelerate division of the tumor-specific CD8+ T cells, and the increase in tumor-specific T-cell number was due to reduced activation-induced cell death. These results indicate that anti-4-1BB mAb can promote CD8+ T cell-mediated protection against large tumors in the absence of CD4+ T-cell help by promoting P1CTL survival without increasing initial clonal expansion.     

Adenoviral vectors targeted to CD40 enhance the efficacy of dendritic cell-based vaccination against human papillomavirus 16-induced tumor cells in a murine model

Dendritic cells (DCs) represent a unique junction from which to initiate antigen-specific immunity. One of the most challenging obstacles for DC-based immunotherapy has been the means by which to convey tumor antigen-encoding genes to DCs. In this study, we show that adenoviral (or adenovirus, Ad) vectors targeted to CD40 by means of bispecific antibodies can enhance gene transfer to murine DCs. Moreover, we illustrate that this vector initiates phenotypic changes characteristic of DC maturation. To explore the in vivo potential of this strategy, we coupled this targeting approach with an Ad vector carrying the gene for a tumor antigen. In particular, the human papillomavirus (HPV) E7 antigen represents an attractive target for antigen-specific immunity of cervical cancer. Relative to DCs infected by untargeted Ad, DCs infected by AdE7 targeted to the receptor CD40 enhanced protection against HPV-16-induced tumor cells in a murine model. We have further established that this protection was both antigen specific and CD8+ T-cell dependent. Illustrating that Ad-modified DCs may be used in repeated vaccination, we report that preimmunization of animals with Ad infected DCs prior to E7 vaccination only moderately reduced vaccine efficacy. Finally, we have observed that CD40-targeted AdE7 can initiate partial therapeutic immunity in mice bearing established tumors. These findings suggest that gene-based vaccination of DCs with tumor antigens can elicit productive antitumoral immunity and that enhancements in gene transfer efficacy and/or DC maturation may facilitate this process.     

Paradoxical enhancement of CD8 T cell-dependent anti-tumor protection despite reduced CD8 T cell responses with addition of a TLR9 agonist to a tumor vaccine

Generation of antigen-specific CD8+ T cell responses is considered optimal for an effective immunotherapy against cancer. In this study, we provide a proof of principle that in vitro observed diminished CD8+ T cell response provided a strong in vivo tumor protection. Immunization with an adenovirus vaccine containing ovalbumin (OVA) gene (Ad5-OVA) strongly induces antigen-specific CD8+ T cell responses measured in vitro using various immunological assays. However, in an attempt to augment the antigenic CD8+ T cell response, coinjection of a TLR9 agonist CpG ODN with the viral vaccine unexpectedly reduced the CD8+ T cell responses measured in vitro but provided a remarkably enhanced tumor protection compared to the CD8+ T cell response generated by Ad5-OVA vaccine alone. Interestingly, despite reduced ex vivo/in vitro CD8+ T cell responses following Ad5-OVA+CpG immunization, immunodepletion studies revealed that the augmented anti-tumor immunity was primarily dependent on CD8+ T cells. The magnitude and effector function of anti-OVA CD8+ T cells remain low following primary and secondary antigenic challenge, presenting a dichotomy between in vitro CD8 T cell responses and in vivo anti-tumor immunity. To examine the impact of CpG ODN, we observed that presence of CpG suppresses the CD8+ T cell proliferation both in vitro and in vivo. These data demonstrate that coadministration of adenovirus vaccine with a TLR9 agonist can generate potentially effective tumor-reactive CD8+ T cells in vivo. In addition, the results indicate that widely used standard immune parameters may not predict the vaccine efficacy containing a TLR9 agonist as adjuvant.     

Tumor expression of 4-1BB ligand sustains tumor lytic T cells

Inadequate costimulation by solid tumors is generally believed to induce immune tolerance during primary tumor growth. We looked for tumor-specific immunity vs. tolerance in patients with Ewing's sarcoma. Circulating T cells from patients with progressively growing Ewing's tumors displayed MHC restricted tumor-induced proliferation and robust tumor lysis. Tumor-reactive T cells reside within the memory CD3+CD8+ subset and are CD28-/4-1BB+. Autologous Ewing's tumors expressed 4-1BBL, and tumor-induced T cell proliferation and activation required costimulation by 4-1BBL. Stimulation of PBL with anti-CD3/4-1BBL, but not anti-CD3/anti-CD28 induced tumor lytic effectors. Similarly, in a xenograft model, anti-CD3/4-1BBL expanded T cells controlled primary growth and prevented metastasis of autologous tumors while nonactivated and anti-CD3/anti-CD28 activated CD8+ cells did not. These results question prevailing models of tumor induced tolerance accompanying progressive tumor growth; rather, we show coexistence of progressive tumor growth and anti-tumor immunity, with costimulation provided by the tumor itself. They further demonstrate a potential new therapeutic role for 4-1BBL mediated costimulation in expanding tumor reactive CTLs for use in the adoptive immunotherapy of cancer.     

Eradication of established renal cell carcinoma by a combination of 5-fluorouracil and anti-4-1BB monoclonal antibody in mice

Renal cell carcinoma (RCC), one of the most incurable malignancies, is highly resistant to chemotherapy and radiotherapy. Cytokine immunotherapy has been the standard approach, but the overall response rate is still very low. Administration of agonistic anti-4-1BB monoclonal antibody (mAb) has been shown to induce regression of several animal tumors but its effect on RCC is unknown. We show here that monotherapy with either anti-4-1BB mAb or the cytotoxic drug, 5-fluorouracil (5-FU), has little effect on established RCC, Renca tumors, but combination therapy with anti-4-1BB mAb and 5-FU eradicates the tumors in more than 70 % of mice. The regressing tumor tissues from mice receiving the combination therapy contained more apoptotic tumor cells and tumor infiltrating lymphocytes than tumor tissues from mice receiving 5-FU or anti-4-1BB mAb monotherapy. The number of lymphocytes in the spleens and tumor- draining lymph nodes (TDLNs) of the combination therapy mice was greatly increased compared to that of control or 5-FU monotherapy mice. Mice that had recovered due to the combination therapy rapidly rejected rechallenge with the tumor, pointing to the establishment of long-lasting tumor-specific memory. Our results indicate that targeting tumors with 5-FU, and immune cells with 4-1BB stimulation, could be a useful strategy for treating incurable RCC.     

Successful immunotherapy of an intraocular tumor in mice.

Immune privilege in the eye is considered essential in the protection against local sight-threatening inflammatory responses. However, the deviant immune responses in the eye may also provide an ideal opportunity to uncontrolled growth of viruses or tumors by inhibiting intraocular immunological attack. To establish to what extent immune privilege interferes with T cell-mediated antitumor immunotherapy, we established a new ocular tumor model in the mouse and tested whether well-defined tumor-specific CTLs can eradicate an immunogenic intraocularly growing tumor. Tumor cells, transformed by human adenovirus type 5 early region 1 (Ad5E1), injected s.c. in a dose of 10(7) cells, did not induce s.c. tumor growth in C57BL/6 mice. However, an injection of 0.3 x 10(6) of these cells into the anterior chamber of the eye led to intraocular tumor growth in 95% of mice (n = 20). Tumor growth in the eye did not induce systemic tumor-specific tolerance, because 70% of the mice were able to eradicate the tumor spontaneously after 5 weeks. Mice vaccinated s.c. with irradiated tumor cells were protected against intraocular tumor challenge, indicating that preactivated memory T cells are able to protect against intraocular tumor growth. Moreover, an i.v. injection of an Ad5E1-specific CTL clone was able to eradicate established intraocular Ad5E1-transformed tumors, whereas the anatomy of the eye remained intact. These results demonstrate that tumor-specific, CTL-mediated immunity can be used successfully for the prevention and eradication of tumors growing in the immune-privileged anterior chamber of the eye, without detectable destruction of the eye.     

放疗或化疗诱导淋巴细胞减少联合免疫重建和瘤苗免疫

目的利用淋巴细胞减少期T细胞发生增殖活化的原理,以全身照射或环磷酰胺引起淋巴细胞减少,联合免疫重建及肿瘤疫苗免疫,以增强机体的肿瘤特异性免疫反应。方法分别以放疗或化疗（环磷酰胺）引起小鼠淋巴细胞减少,然后输入同系小鼠的未致敏脾细胞,建立免疫重建的淋巴细胞减少小鼠模型（RLM）。用黑色素瘤细胞F10对前者行免疫．肿瘤攻击实验,并行T细胞亚群清除试验。而化疗-RLM-免疫模型的抗肿瘤免疫反应效果通过过继免疫治疗检测。免疫用瘤苗为GMCSF修饰的黑色素瘤细胞D6-G6。免疫后9～10d,采集肿瘤疫苗接种部位的引流淋巴结,制备效应T细胞,然后过继回输给荷瘤3d（D5）的小鼠。2周后处死小鼠,计数肺转移灶数目。结果63．2％的放疗-RLM-免疫组小鼠可对肿瘤攻击产生抵抗,显著高于正常-免疫组（16．7％,P〈0．0001）。CD8^＋T细胞是介导抗肿瘤保护性免疫的主要效应细胞。延长免疫重建和瘤苗接种之问的间隔可削弱保护性抗肿瘤免疫。化疗-RLM-免疫组效应T细胞的在体抗肿瘤活性显著强于正常．免疫组。结论在放、化疗引起的淋巴细胞减少期进行瘤苗免疫,有助于打破机体对肿瘤的免疫耐受,增强抗肿瘤免疫反应。     

转4-1BBL 基因的小鼠肝癌细胞瘤苗刺激脾细胞产生细胞因子的研究

 目的 研究转4-1BBL基因的小鼠肝癌细胞瘤苗体外刺激同系小鼠脾细胞产生细胞因子（IL-2、TNF-α和GM-CSF）的能力。方法 以丝裂霉素C（MMC）处理高表达转m4-1 BBL基因的小鼠Hepa1-6肝癌细胞，制成肿瘤细胞瘤苗（TCV），体外与同系小鼠脾淋巴细胞共同培养后，观察其对脾细胞产生细胞因子（IL-2、TNF-α和GM—CSF）的影响。结果 TCV-4-1 BBL刺激后，脾细胞体外分泌细胞因子IL-2、TNF-α和GM-CSF的水平明显增高。结论 转4-1BBL基因的小鼠肝癌细胞瘤苗能刺激脾细胞产生细胞因子IL-2、TNF-α和GM-CSF。