Regression of engineered tumor cells secreting cytokines is related to a shift in host cytokine profile from type 2 to type 1

Fusion Hybrid of Dendritic Cells and Engineered Tumor Cells Expressing Interleukin-12 Induces Type 1 Immune Responses against Tumor

Aims and Background

Dendritic cell (DC)-tumor fusion hybrid vaccinees that facilitate antigen presentation represent a novel powerful strategy in cancer immunotherapy. Preclinical studies have demonstrated that IL-12 promotes specific antitumor immunity mediated by T cells in several types of tumors. In the present study, we investigated the antitumor immunity derived from vaccination of fusion hybrids between DCs and engineered J558/IL-12 myeloma cells secreting Th1 cytokine IL-12.

Methods

The expression vector pcDNA-IL-12 was generated and transfected into J558 myeloma cells and then bone marrow-derived DCs were fused with engineered J558/IL-12 cells. The antitumor immunity derived from vaccination of the fusion hybrid DC/J558/IL-12 was evaluated in vitro and in vivo.

Results

DC/J558/IL-12 cells secreted recombinant IL-12 (1.6 ng/mL), and inoculation of BALB/c mice with DC/J558/IL-12 hybrid induced a Th1 dominant immune response and resulted in tumor regression. Immunization of mice with engineered DC/J558/IL-12 hybrid elicited stronger J558 tumor-specific cytotoxic T lymphocyte (CTL) responses in vitro as well as more potent protective immunity against J558 tumor challenge in vivo than immunization with the mixture of DCs and J558/IL-12, J558/IL-12 and J558, respectively. Furthermore, the antitumor immunity mediated by DC/J558/1L-12 tumor cell vaccination in vivo appeared to be dependent on CD8+ CTL.

Conclusions

These results demonstrate that the engineered fusion hybrid vaccines that combine Th1 cytokine gene-modified tumor cells with DCs may be an attractive strategy for cancer immunotherapy.

CD40 ligation converts TGF-beta-secreting tolerogenic CD4-8- dendritic cells into IL-12-secreting immunogenic ones

CD40L, the ligand for CD40 on dendritic cells (DCs), plays an important role in maturation and activation of DCs leading to induction of immune responses. Our previous studies showed that the mouse splenic CD4(-)8(-) DCs are tolerogenic and capable of stimulating suppressive type 1 CD4(+) regulatory T (Tr1) cell responses via TGF-beta secretion. In this study, we investigated whether CD40 ligation is able to convert tolerogenic CD4(-)8(-) DCs into immunogenic ones by in vitro treatment of DCs with anti-CD40 antibody. Our data showed that in vitro CD40 ligation with anti-CD40 antibody converted TGF-beta-secreting tolerogenic CD4(-)8(-) DCs into IL-12-secreting immunogenic ones capable of stimulating type 1 CD4(+) helper T (Th1) and CD8(+) cytotoxic T lymphocyte (CTL) responses leading to induction of antitumor immunity. In addition, in vivo CD40 ligation by intratumoral injection of adenoviral vector AdVCD40L expressing CD40 ligand also induced tumor growth inhibition and regression of established P815 tumors with infiltration of tolerogenic CD4(-)8(-) DCs. Therefore, our data provide new information for and may thus have useful impacts in CD40 ligation-based immunotherapy of cancer.

Vaccination of fiber-modified adenovirus-transfected dendritic cells to express HER-2/neu stimulates efficient HER-2/neu-specific humoral and CTL responses and reduces breast carcinogenesis in transgenic mice

HER-2/neu transgene-modified dendritic cell (DC)-based vaccines are potent at eliciting HER-2/neu-specific antitumor immunity. In this study, we constructed a recombinant adenovirus (RGD)AdVneu with fiber gene modified by RGD insertion into the viral knob's H1 loop. We transfected DCs with (RGD)AdVneu, and assessed/compared HER-2/neu-specific humoral and cytotoxic T lymphocyte (CTL) responses and antitumor immunity derived from the original AdVneu-transfected DCs (DCneu1) and (RGD)AdVneu-transfected DCs (DCneu2). We demonstrated that DCneu2 displayed increased HER-2/neu expression by 8.3-fold compared to DCneu1. We also demonstrated that DCneu2 vaccination induced stronger HER-2/neu-specific humoral and CTL immune responses than DCneu1 vaccination. DCneu2 vaccination protected all the mice from HER-2/neu-expressing Tg1-1 tumor cell challenge in wild-type FVB/NJ mice, compared to a partial protection in DCneu1-immunized mice. In addition, DCneu2 vaccination also significantly delayed tumor growth than DCneu1 immunization (P<0.05) in Tg FVBneuN mice. Three immunizations of DCneu2 starting at the mouse age of 2 months also significantly delayed breast cancer development in Tg mice compared to DCneu2 vaccine (P<0.05). Importantly, DCneu2 vaccine reduced breast carcinogenesis by 9% in Tg mice with self HER-2/neu tolerance. Therefore, vaccination of fiber-modified adenovirus-transfected DCs to enhance expression of tumor antigens such as HER-2/neu is likely representative of a new direction in DC-based vaccine of breast cancer.

The tumour microenvironment and implications for cancer immunotherapy

Tumour cells exist in a complex milieu of cellular and non-cellular components comprising fibroblasts, endothelial cells, immune cells and metabolites of cellular respiration. An elaborate interplay between these components and tumour cells exists with implications for immunological recognition of tumour cells. Tumours have been shown to alter their antigen and cytokine profiles, desensitise and impair immune defences, signal fibroblasts to facilitate metastasis, and take advantage of acidic and hypoxic conditions that impede normal cells. This paper aims to review the roles of the stroma, extracellular matrix and chemistry of the microenvironment on tumour growth, with particular emphasis on interactions with the immune system, and to highlight some of the novel therapeutic strategies that target the tumour microenvironment.

HER-2/neu-gene engineered dendritic cell vaccine stimulates stronger HER-2/neu-specific immune responses compared to DNA vaccination

HER-2/neu is a candidate for developing breast cancer-targeted immunotherapeutics. Although DNA-based and HER-2/neu transgene-modified dendritic cell (DC)-based vaccines are potent at eliciting HER-2/neu-specific antitumor immunity, there has been no side-by-side study comparing them directly. The present study utilizes an in vivo murine tumor model expressing HER-2/neu antigen to compare the efficacy between adenovirus (AdVneu)-transfected dendritic cells (DC(neu)) and plasmid DNA (pcDNAneu) vaccine. Our data showed that DC(neu) upregulated the expression of immunologically important molecules and inflammatory cytokines and partially converted regulatory T (Tr)-cell suppression through interleukin-6 (IL-6) secretion. Vaccination of DC(neu) induced stronger HER-2/neu-specific humoral and cellular immune responses than DNA vaccination, which downregulated HER-2/neu expression and lysed HER-2/neu-positive tumor cells in vitro, respectively. In two HER-2/neu-expressing tumor models, DC(neu) completely protected mice from tumor cell challenge compared to partial or no protection observed in DNA-immunized mice. In addition, DC(neu) significantly delayed breast cancer development in transgenic mice in comparison to DNA vaccine (P<0.05). Taken together, we have demonstrated that HER-2/neu-gene-modified DC vaccine is more potent than DNA vaccine in both protective and preventive animal tumor models. Therefore, DCs genetically engineered to express tumor antigens such as HER-2/neu represent a new direction in DC vaccine of breast cancer.

Combined radiation therapy and dendritic cell vaccine for treating solid tumors with liver micro-metastasis

BACKGROUND

Tumor metastasis and relapse are major obstacles in combating human malignant diseases. Neither radiotherapy alone nor injection of dendritic cells (DCs) can successfully overcome this problem. Radiation induces tumor cell apoptosis and necrosis, resulting in the release of tumor antigen and danger signals, which are favorable for DC capturing antigens and maturation. Hence, the strategy of combined irradiation and DC vaccine may be a novel approach for treating human malignancies and early metastasis.

METHODS

To develop an effective combined therapeutic approach, we established a novel concomitant local tumor and liver metastases model through subcutaneous (s.c.) and intravenous (i.v.) injection. We selected the optimal time for DC injection after irradiation and investigated the antitumor effect of combining irradiation with DC intratumoral injection and the related mechanism.

RESULTS

Combined treatment with radiotherapy and DC vaccine could induce a potent antitumor immune response, resulting in a significant decrease in the rate of local tumor relapse and the numbers of liver metastases. The related mechanisms for this strong antitumor immunity of this combined therapy might be associated with the production of apoptotic and necrotic tumor antigens and heat shock proteins after irradiation, phagocytosis, migration and maturation of DCs, and induction of more efficient tumor-specific cytotoxic T lymphocyte activity through a cross-presentation pathway.

CONCLUSIONS

Co-administration of local irradiation and intratumoral DC injection may be a promising strategy for treating radiosensitive tumors and eliminating metastasis in the clinic.

Combined CD4+ Th1 effect and lymphotactin transgene expression enhance CD8+ Tc1 tumor localization and therapy

Type 1 T cells are the major components in antitumor immunity. The lack of efficient CD8(+) cytotoxic T (Tc) cell infiltration of tumors is a major obstacle to adoptive Tc-cell therapy. We have previously demonstrated that adenovirus (AdV)-mediated transgene lymphotactin (Lptn) expression by intratumoral AdVLptn injection and intravenous CD4(+) helper T (Th) cell transfer can enhance Tc-cell tumor infiltration and eradication of early stage tumors (5 mm in diameter). In this study, we generated ovalbumin (OVA)-specific Tc1 and Th1 cells in vitro by incubation of OVA-pulsed dendritic cells with naive T cells from T-cell receptor (TCR) transgenic OT I and OT II mice. We then investigated the potential synergy of Th1 help effect and Lptn transgene expression in Tc1-cell therapy of well-established OVA-expressing EG7 solid tumors (7 mm in diameter). Our data showed that a combined adoptive T-cell therapy of Th1 (2.5 x 10(6) cells per mouse) and Tc1 (5 x 10(6) cells per mouse) resulted in regression of all eight (100%) transgene Lptn expressed EG7 tumors, which is significantly higher than four from eight (50%) in AdVLptn/Tc1 group and two from eight (25%) in Tc1/Th1 group (P < 0.05). The amount of transferred Tc1 cells detected in Lptn-expressed tumors with Th1 treatment is 0.72%, which is significantly higher than those of AdVLptn (0.22%), Th1 (0.41%) and the control AdVpLpA (0.09%) treatment groups (P < 0.05). Enhanced Tc1 tumor localization may be derived from the chemotactic effect of Lptn and the proliferative effect of Th1 and Lptn. This novel therapeutic strategy with enhancement of Tc1 tumor localization in the therapy of well-established tumors may become a tool of considerable conceptual interest in the implementation of future clinical objectives.

Tumor-infiltrating dendritic cell subsets of progressive or regressive tumors induce suppressive or protective immune responses

Tumor-infiltrating dendritic cells (TID) have an ambivalent role in regulation of tumor regression or growth. However, their precise natures and molecular mechanisms have not been elucidated. In this study, we studied TIDs recruited in progressive P815 and regressive P198 tumors of the same origin. Our data showed that P815 tumors contained CD4+ 8+ and CD4- 8- TID815 subsets, whereas P198 tumors contained CD4+ 8+ and CD4+ 8- TID198 subsets. They similarly stimulate allogeneic T cell proliferation and have nitric oxide-mediated cytotoxicity to tumor cells with an exception of CD4- 8- TID815 with less efficiency. The newly identified fourth CD4+ 8+ TID815 or TID198 subset and the CD4+ 8- TID198 all express high levels of IFN-gamma and interleukin (IL)-6, whereas CD4- 8- TID815 secrete a marked level of transforming growth factor-beta. Vaccination of mice with P815 tumor lysate-pulsed CD4+ 8+ TID815 or TID198 and CD4+ 8- TID198 induced IFN-gamma-secreting Th1 and effective CTL responses leading to protective immunity against P815 tumor, whereas CD4- 8- TID815 stimulated IL-10-expressing Tr1 responses leading to immune suppression. Transfer of CD4+ Tr1 cells obtained from CD4- 8- TID815-immunized wild-type, but not IL-10(-/-) mice, into CD4+ 8+ TID815 immunized mice abolished otherwise inevitable development of antitumor immunity. Taken together, our findings provide an important insight into immunologic alterations in progressive and regressive tumors and an implication for dendritic cell-based approaches in the design of cancer vaccines.

Intratumoral administration of immature dendritic cells following the adenovirus vector encoding CD40 ligand elicits significant regression of established myeloma

Our previous study showed that J558 myeloma cells engineered CD40L lost their tumorigenicity in syngeneic mice, and the inoculation of J558/CD40L tumor cells further led to the protective immunity against wild tumors. In the present study, we investigated whether the vaccine can exert more efficient antitumor immunity by combination with adenovirus mediated CD40L gene therapy and immature dendritic cells (iDCs). The results demonstrated that intratumoral administration of iDCs 2 days after AdVCD40L injection, not only significantly suppressed the tumor growth, but also eradiated the established tumors in 40% of the mice. The potent antitumor effect produced by the combination therapy correlated with high expression of MHC, costimulatory and Fas molecules on J558 cells, which was derived from CD40L transgene expression. In addition, transgene CD40L expression could dramatically induce J558 cell apoptosis. Effectively capturing apoptotic bodies by iDCs in vivo could induce DC maturation, prime tumor-specific CTLs and tend to Th1-type immune response. Finally, in vivo depletion experimentation suggested both CD4+ and CD8+ T cells were involved in mediating the antitumor immune responses of combined treatment of AdVCD40L and iDCs, with CD8+ T cells being the major effector. These findings could be beneficial for designing strategies of DCs vaccine and CD40L for anticancer immunotherapy.

Engineered fusion hybrid vaccine of IL-18 gene-modified tumor cells and dendritic cells induces enhanced antitumor immunity

Dendritic cell (DC)-tumor fusion hybrid vaccines that facilitate antigen presentation represent a novel powerful strategy in cancer immunotherapy. In our study, we investigated the antitumor immunity derived from the vaccination of fusion hybrids between engineered J558/IL-18 myeloma cells secreting Th1 cytokine IL-18 and DCs. DC/J558/IL-18 could secret a higher level of IL-18 than DCs, efficiently expressed J558 tumor antigen P1A, and enhanced ability of allogeneic T cell stimulation when compared to J558/IL-18. Our data showed that the immunization of BALB/c mice with DC/J558/IL-18 hybrids induced the most potent protective immunity against 1 x 10(6) cells with a J558 tumor challenge, compared to those immunized with the mixture of DCs and J558/IL-18, J558/IL-18, or J558. Furthermore, the immunization of mice with engineered DC/J558/IL-18 hybrids elicited stronger NK activity and J558 tumor-specific cytotoxic T lymphocyte (CTL) responses in vitro. In addition, DC/J558/IL-18 tumor cells into syngeneic mice induced a Th1 dominant immune response to J558 and resulted in tumor regression, which indicated that the antitumor effect mediated by DC/J558/IL-18 appeared to be dependent on TH1 cytokine production. These results demonstrate that the engineered fusion hybrid vaccines that combine Th1 gene-modified tumor with DCs may be an attractive strategy for cancer immunotherapy.

Synergistic effect of lymphotactin and interferon gamma-inducible protein-10 transgene expression in T-cell localization and adoptive T-cell therapy of tumors

The lack of efficient T-cell infiltration of tumors is a major obstacle to successful adoptive T-cell therapy. We have previously demonstrated that adenovirus (AdV)-mediated transgene lymphotactin (Lptn) or IP-10 expression in tumors can significantly enhance T-cell tumor infiltration. In this study, active OVA-specific CD8+ T cells were prepared by coculturing naive OVA-specific CD8+ T cells from transgenic OT I mice with OVA-I peptide-pulsed dendritic cells in vitro. These XCR-1- and CXCR3-expressing T cells predominantly secreted IFN-gamma and displayed significant killing activity (84% at effector:target cell ratio of 1.5) against OVA-expressing EG7 tumor cells through perforin-mediated pathway. Our data also showed that chemokine Lptn and IP-10 not only can chemoattract, but also stimulate proliferation of CD8+ T cells in vitro, and that a mixture of Lptn and IP-10 can more efficiently chemoattract CD8+ T cells than either one of them. Furthermore, we demonstrated that the transferred CD8+ T cells detected in group of tumors treated with both AdVLptn and AdVIP-10 (group a) are around 4 and 2 times more than that in groups of tumors treated with control AdVpLpA (group b) and either AdVIP-10 (group c) or AdVLptn (group d), respectively. Around 87.5% of mice in group a were tumor-free compared to the aggressive tumor growth in all 8 mice of group b and 25% or 37.5% cured mice seen in groups c and d (p<0.05). Thus, our results indicate that enhancement of adoptive T-cell therapy can be obtained by double tranmsgene Lptn and IP-10 expression, which facilitates CD8+ T-cell tumor localization through proliferation and chemoattraction of the transferred CD8+ T cells by in situ chemokine transgene expressions in the tumors. Collectively, our data provide solid evidence of a potent synergy between adoptive T-cell therapy and adenovirus-mediated Lptn and IP-10 gene transfer into tumor tissues, which culminated in the T-cell tumor localization and eradication of well-established tumor masses.

Dendritic cells engineered to express the Flt3 ligand stimulate type I immune response, and induce enhanced cytoxic T and natural killer cell cytotoxicities and antitumor immunity

BACKGROUND

Tumor antigen presentation by dendritic cells (DCs) to T cells in lymphoid organs is crucial for induction of antitumor immune responses. Fms-like tyrosine kinase 3 ligand (Flt3L) is a regulator of hematopoietic cell development.

METHODS

To investigate the potential effect of Flt3L transgene expression on DC-based cancer vaccines, we constructed a recombinant adenovirus AdVFlt3L expressing Flt3L, transfected DCs with AdVFlt3L, and investigated the efficacy of antitumor immunity by vaccination of DC(Flt3L) engineered to express Flt3L transgene.

RESULTS

Our data demonstrated that AdVFlt3L transfection up-regulated the expression of cytokine IL-1beta and chemokines MIP-1alpha, MIP-1beta, IP-10, MCP-1 and MIP-2, and stimulated DC(Flt3L) cell proliferation in vitro and migration toward regional lymph nodes in vivo. Our data also demonstrated that vaccination of Mut1-pulsed DC(Flt3L) cells was able to stimulate (i). a type 1 immune response comprising CD4(+) Th1 and CD8(+) Tc1 activation and (ii). around 2- and 3-fold enhanced tumor-specific cytotoxic T lymphocyte (CTL) and non-specific NK responses (p < 0.05) than vaccination with similarly pulsed control virus-transfected and untransfected DCs, respectively. More importantly, vaccination of Mut1-pulsed DC(Flt3L) cells induced enhanced antitumor immunity in vivo, even against poorly immunogenic 3LL tumor cells. Vaccinations of Mut1-pulsed DCs, DC(pLpA) and DC(Flt3L) all protected mice from challenge of low dose (0.5 x 10(5)) tumor cells. However, only vaccination of the last one was able to protect 63% (6/8) mice from challenge of high dose (3 x 10(5)) 3LL tumor cells (p < 0.01).

CONCLUSIONS

DCs engineered to secrete Flt3L may offer a new strategy in DC-based cancer vaccines.

Tumour necrosis factor-alpha (TNF-alpha) transgene-expressing dendritic cells (DCs) undergo augmented cellular maturation and induce more robust T-cell activation and anti-tumour immunity than DCs generated in recombinant TNF-alpha

Tumour antigen presentation by dendritic cells (DCs) to T cells in lymphoid organs is crucial for induction of anti-tumour immune responses. It has been previously reported that tumour necrosis factor-alpha (TNF-alpha) is required for DC activation and subsequent induction of optimal immune responses, and thus DCs for anti-tumour vaccination are often generated by culture in exogenous TNF-alpha. In the present study, we investigated the effect on anti-tumour immunity of vaccination with Mut1 tumour peptide-pulsed DCs engineered to express a TNF-alpha transgene. Our data shows that transfection of DCs with recombinant adenovirus AdV-TNF-alpha resulted in greater maturation of the DCs than occurred with control DCs cultured in exogenous TNF-alpha, as determined by up-regulated expression of pro-inflammatory cytokines (e.g. interleukins 1beta and 18), chemokines [e.g. interferon-gamma-inducible protein-10 and macrophage inflammatory protein-1beta (MIP-1beta)], the CC chemokine receptor CCR7, and immunologically important cell surface molecules (CD40, CD86 and intercellular adhesion molecule-1). These transgenic DCs stimulated stronger allogeneic T-cell responses in vitro and T-cell activation in vivo; displayed 2.4-fold enhanced chemotactic responses to the MIP-3betain vitro (P<0.05); and, perhaps most importantly, trafficked into the draining lymph nodes dramatically (seven-fold, P<0.01) more efficiently than the control DCs. Our data also demonstrate that vaccination of mice with Mut1 peptide-pulsed, AdV-TNF-alpha-transfected DCs stimulated more efficient in vitro Mut1-specific CD8+ cytotoxic T-cell responses and solid tumour immunity in vivo, when compared to the in vitro TNF-alpha-cultivated DCs. Thus, DCs engineered to secrete TNF-alpha may offer a new strategy in DC cancer vaccines.

Leukemic dendritic cells: potential for therapy and insights towards immune escape by leukemic blasts

Dendritic cells (DCs) are a system of potent antigen-presenting cells (APCs) specialized to initiate primary immune responses. DCs are considered important elements in the induction of specific antitumor cytotoxic effectors. At present, because of potential therapeutic implications, the critical role of DCs in cancer patients is under intensive investigation. Interactions between DCs and acute myeloid leukemia cells represent an attractive model for the study of DC physiology. Moreover, DCs can be a valuable therapeutic tool for the adjuvant treatment of leukemic patients. However, DC subsets in vivo may also be affected by leukemogenesis and may contribute to the escape of leukemia from immune control. The aim of this review is to shed further light on this paradoxical picture where the line between immune tolerance and immune defense is narrow.

Enhanced HER-2/neu-specific antitumor immunity by cotransduction of mouse dendritic cells with two genes encoding HER-2/neu and alpha tumor necrosis factor

The present study uses an in vivo murine tumor model expressing the human HER-2/neu antigen to evaluate the potential vaccine using dendritic cells (DCs) infected with adenovirus AdVHER-2. We first investigated whether infected DCs (DC(HER-2)) engineered to express HER-2/neu could induce HER-2/neu-specific immune responses. Our data showed that (i) AdVHER2-infected DC(HER-2) expressed HER-2/neu by Western blot and flow cytometric analysis, and (ii) vaccination of mice with DC(HER-2) induced HER-2/neu-specific cytotoxic T-lymphocyte (CTL) responses, but protected only 25% of vaccinated mice from challenge of 3 x 10(5) MCA26/HER-2 tumor cells. Further, to enhance the efficacy of DC(HER-2) vaccine, we coinfected DCs with both AdVHER-2 and AdVTNF-alpha. The infected DCs (DC(HER-2/TNF-alpha)) displayed the expression of both HER-2/neu and TNF-alpha by flow cytometric and ELISA analysis. We next investigated whether DC(HER-2/TNF-alpha) could induce stronger HER-2/neu-specific immune responses. We found that DC(HER-2/TNF-alpha) displayed up-regulation of immunologically important CD40, CD86, and ICAM-I molecules compared with DC(HER-2), indicating that the former ones are more mature forms of DCs. Vaccination of DC(HER-2/TNF-alpha) induced stronger allogeneic T-cell proliferation and 36% enhanced HER-2/neu-specific T-cell responses in vitro than DC(HER-2) cells. More importantly, it stimulated the significant anti-HER-2/neu immunity in vivo, which protected 8/8 mice from challenge of 3 x 10(5) MCA26/HER-2 tumor cells. Therefore, DCs genetically engineered to express both the tumor antigen and cytokines such as TNF-alpha as an immunoadjuvant are likely to represent a new direction in DC vaccine of cancer.

Engineered fusion hybrid vaccine of IL-4 gene-modified myeloma and relative mature dendritic cells enhances antitumor immunity

Dendritic cell (DC)-tumor fusion hybrid vaccine which facilitates antigen presentation represents a new powerful strategy in cancer therapy. In the present study, we investigated the antitumor immunity derived from vaccination of fusion hybrids between wild-type J558 or engineered J558-IL-4 myeloma cells secreting cytokine interleukin-4 (IL-4) and immature DCs (DC(IMAT)) or relative mature DCs (DC(RMAT)). DC(RMAT) displayed an up-regulated expression of immune molecules (Ia(d), CD40, CD54, CD80 and CD86) and certain cytokines/chemokines, and enhanced ability of allogeneic T cell stimulation when compared to DC(IMAT). These DCs were fused with myeloma cells by polyethylene glycol (PEG). The fusion efficiency was approximately 20%. Our data showed that immunization of C57BL/6 mice with DC(RMAT)/J558 hybrids induced protective immunity against a high dose of J558 tumor challenge (1x10(6) cells) in 3 out of 10 immunized mice, compared with no protection seen in mice immunized with DC(IMAT)/J558 hybrids. Furthermore, immunization of mice with engineered DC(RMAT)/J558-IL-4 hybrids elicited stronger J558 tumor-specific cytotoxic T lymphocyte (CTL) responses in vitro and induced more efficient protective immunity (10/10 mice; tumor free) against J558 tumor challenge in vivo than DC(RMAT)/J558 hybrid vaccines. The results demonstrate the importance of DC maturation in DC-tumor hybrid vaccines and indicate that the engineered fusion hybrid vaccines which combine gene-modified tumor and DC vaccines may be an attractive strategy for cancer immunotherapy.

Intratumoral coinjection of two adenoviral vectors expressing functional interleukin-18 and inducible protein-10, respectively, synergizes to facilitate regression of established tumors

We have constructed two recombinant adenoviral vectors AdVIP-10 and AdVIL-18 expressing the functional chemokine IFN-gamma inducible protein (IP)-10 and cytokine interleukin (IL)-18, respectively. Injection of either AdVIP-10 or AdVIL-18 subcutaneously into tumor nodules derived from the J558 murine myeloma cell line delayed some tumor growth but it was not curative in all cases. Coinjection of these two vectors at the same tumor nodule not only significantly suppressed the tumor growth, but also cured established tumors in 8 of 10 (80% tumor free) mice. The latter treatment stimulated T-cell infiltration into tumors in association with tumor necrosis formation, induced a type 1 immune response and induced the activation of J558 tumor-specific cytotoxic T lymphocytes. Moreover, the antitumor activity of IP-10 and IL-18 combined gene therapy was significantly diminished in mice with depletion of either CD4(+) (50% tumor free) or CD8(+) (40% tumor free) T cells, and completely lost (0% tumor free) in T cell-deficient nude and IFN-gamma knockout mice, indicating the critical roles of T cells and IFN-gamma in this therapeutical model. Taken together, the findings of this study demonstrate that the combined use of two adenoviral vectors expressing IP-10 and IL-18, respectively, synergize to facilitate regression of established tumors. These observations also suggest the potential use of double-recombinant adenoviral vectors expressing chemokines and immunomodulatory cytokines in cancer gene therapy.

Synergistic effect of adoptive T-cell therapy and intratumoral interferon gamma-inducible protein-10 transgene expression in treatment of established tumors

The lack of efficient T-cell infiltration of tumors is a major obstacle to successful adoptive T-cell therapy. We have previously shown that transplanted SP2/0 myeloma tumors engineered to express lymphotactin invariably induced tumor regress mediated by SP2/0 tumor-specific T cells. Herein, we further systemically characterize these activated T cells and investigate their therapeutic efficacy, either alone or with the chemokine interferon gamma (IFN-gamma)-inducible protein-10 (IP-10) gene therapy. Following stimulation with SP2/0 cells, these activated T cells were CD25(+)FasL(+) L-selectin(low), expressed CXCR3 receptor and were chemoattracted by IP-10 in vitro. They comprised 64% CD4(+) Th1 and 36% CD8(+) Tc1 cells, both of which expressed IFN-gamma, perforin, and TNF-alpha, but not IL-4. The activated T cells were strongly cytotoxic for SP2/0 tumor cells (79% specific killing; E:T ratio, 50), mainly via perforin-mediated pathway. Cell tracking using labeled T cells confirmed that these T cells infiltrated better into the IP-10-expressing tumors than non-IP-10-expressing ones. In vivo, combined intratumoral IP-10 gene transfer and adoptive T-cell immunotherapy for well-established SP2/0 tumors eradicated the tumors in 7 of the 8 mice. Control or IP-10 adenoviral treatments by themselves neither alter the lethal outcome for tumor-bearing mice nor did T-cell therapy by itself, although the latter two treatments did slow its time-frame. Taken together, our data provide solid evidence of a potent synergy between adoptive T-cell therapy and IP-10 gene transfer into tumor tissues, which culminated in the eradication of well-established tumor masses.

Adenovirus-mediated CD40 ligand gene-engineered dendritic cells elicit enhanced CD8(+) cytotoxic T-cell activation and antitumor immunity

CD40L, the ligand for CD40 on dendritic cells (DCs), plays an important role in their activation and is essential for induction of antigen-specific T-cell responses. In the present study, we investigated the efficacy of antitumor immunity induced by vaccination with DCs engineered to express CD40L and pulsed with Mut1 tumor peptide. Our data show that transfection of DCs with recombinant adenovirus AdV-CD40L resulted in activation of DCs with up-regulated expression of proinflammatory cytokines (IL-1beta and IL-12), chemokines (RANTES, IP-10, and MIP-1alpha), and immunologically important cell surface molecules (CD54, CD80, and CD86). Our data also demonstrate that DCs transfected with AdV-CD40L (DC(CD40L)) are able to stimulate enhanced allogeneic T-cell proliferation and Mut1-specific CD8(+) cytotoxic T-cell responses in vitro. Vaccination of mice with Mut1 peptide-pulsed control virus-transfected DC (DC(pLpA)) could only protect mice from challenge of a low dose (0.5 x 10(5) cells per mouse, 8/8 mice), but not a high dose (3 x 10(5) cells per mouse, 0/8 mice) of 3LL tumor cells. However, vaccination of Mut1 peptide-pulsed AdV-CD40L-transfected DC(CD40L) induced an augmented antitumor immunity in vivo by complete protection of mice (8/8) from challenge of both low and high doses of 3LL tumor cells. Thus, DCs engineered to express CD40L by adenovirus-mediated CD40 ligand gene transfer may offer a new strategy in production of DC cancer vaccines.

DNA array and biological characterization of the impact of the maturation status of mouse dendritic cells on their phenotype and antitumor vaccination efficacy

We systematically investigated the impact of the relative maturation levels of dendritic cells (DCs) on their cell surface phenotype, expression of cytokines and chemokines/chemokine receptors (by DNA array and RNase protection analyses), biological activities, and abilities to induce tumor immunity. Mature DCs expressed significantly heightened levels of their antigen-presenting machinery (e.g., CD54, CD80, CD86) and numerous cytokines and chemokines/chemokine receptors (i.e., Flt-3L, G-CSF, IL-1alpha and -1beta, IL-6, IL-12, CCL-2, -3, -4, -5, -17, and -22, MIP-2, and CCR7) and were significantly better at inducing effector T cell responses in vitro. Furthermore, mice vaccinated with tumor peptide-pulsed mature DCs better survived challenge with a weakly immunogenic tumor (8 of 8 survivors) than did mice vaccinated with less mature (3 of 8 survived) or immature (0 of 8 survivors) DCs. Nevertheless, intermediate-maturity DCs expressed substantial levels of Flt-3L, IGF-1, IL-1alpha and -1beta, IL-6, CCL-2, -3, -4, -9/10, -17, and -22, MIP-2, osteopontin, CCR-1, -2, -5, and -7, and CXCR-4. Taken together, our data clearly underscore the critical nature of employing DCs of full maturity for DC-based antitumor vaccination strategies.

Efficient antitumor immunity derived from maturation of dendritic cells that had phagocytosed apoptotic/necrotic tumor cells

Dendritic cells (DCs) that acquired antigen from apoptotic tumor cells are able to induce major histocompatibility complex (MHC) class I-restricted cytotoxic T lymphocytes and antitumor immunity. In the present study, we investigated the efficiency of antitumor immunity derived from DCs that had phagocytosed apoptotic/necrotic BL6-10 melanoma cells compared with that of DCs pulsed with the tumor mTRP2 peptide. Our data showed that phagocytosis of apoptotic/necrotic tumor cells resulted in maturation of DCs with up-regulated expression of proinflammatory cytokines [interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha, interferon-gamma and granulocyte-macrophage colony-stimulating factor], chemokines (MIP-1alpha, MIP-1beta and MIP-2), the CC chemokine receptor CCR7 and the cell surface molecules (MHC class II, CD11b, CD40 and CD86), and down-regulated expression of the CC chemokine receptors CCR2 and CCR5. These mature DCs displayed enhanced migration toward the CC chemokine MIP-3beta in a chemotaxis assay in vitro and to the regional lymph nodes in an animal model in vivo. Our data also showed that vaccination with DCs that had phagocytosed apoptotic/necrotic BL6-10 cells was able to (i) more strongly stimulate allogeneic T-cell proliferation in vitro, (ii) induce an in vivo Th1-type immune response leading to more efficient tumor-specific cytotoxic CD8(+) T-cell-mediated immunity and (iii) eradicate lung metastases in all 6 vaccinated mice compared with mice vaccinated with DCs pulsed with the tumor mTRP2 peptide, in which lung metastases were reduced (mean number of 16 per mouse) but not completely eradicated. Therefore, DCs that had phagocytosed apoptotic/necrotic tumor cells appear to offer new strategies in DC cancer vaccines.

Lymphotactin expression by engineered myeloma cells drives tumor regression: mediation by CD4+ and CD8+ T cells and neutrophils expressing XCR1 receptor

The C chemokine lymphotactin has been characterized as a T cell chemoattractant both in vitro and in vivo. To determine whether lymphotactin expression within tumors could influence tumor growth, we transfected an expression vector for lymphotactin into SP2/0 myeloma cells and tested their ability to form tumors in BALB/c and nude mice. Transfection did not alter cell growth in vitro. Whereas SP2/0 cells gave rise to a 100% tumor incidence, lymphotactin-expressing SP2/0-Lptn tumors invariably regressed in BALB/c mice and became infiltrated with CD4(+) and CD8(+) T cells and neutrophils. Regression of the SP2/0-Lptn tumors was associated with a type 1 cytokine response and dependent on both CD4(+) and CD8(+) T cells, but not NK cells. Both SP2/0 and SP2/0-Lptn tumors grew in nude mice, but growth of the latter tumors was retarded and associated with heavy neutrophil responses; this retardation of SP2/0-Lptn tumor growth was reversed by neutrophil depletion of the mice. Our data also indicate that mouse neutrophils express the lymphotactin receptor XCR1 and that lymphotactin specifically chemoattracts these cells in vitro. Thus, lymphotactin has natural adjuvant activities that may augment antitumor responses via effects on both T cells and neutrophils and thereby could be important in gene transfer immunotherapies for some cancers.

Neutrophils and B cells express XCR1 receptor and chemotactically respond to lymphotactin

The C chemokine lymphotactin (Lptn) has been reported to act specifically on CD4(+) and CD8(+) T lymphocytes and natural killer (NK) cells, but not monocytes. However, the chemotactic effect of Lptn on other types of hematopoietic cells has not been well studied. In this study we investigated (i) the chemotactic influences of Lptn on T and B lymphocytes, neutrophils, monocytes, and dendritic cells, and (ii) the expression of the Lptn receptor (XCR1) by these cells, using RT-PCR. Our data showed that Lptn is chemotactic for B lymphocytes and neutrophils as well as T lymphocytes, but not for monocytes or dendritic cells, and that XCR1 expression is found only in association with T and B lymphocytes and neutrophils, but not monocytes or dendritic cells. Thus, this study is the first demonstration of a chemotactic effect of Lptn on neutrophils and confirms the association of this effect with expression of the XCR1 receptor on these cells. These data suggest that Lptn could potentially be an important protein in the regulation of T and B lymphocytes and neutrophil trafficking, and thereby also their roles in inflammatory and immunological responses.