High-efficiency transduction of freshly isolated human tumor cells using adenoviral interleukin-2 vectors

Evaluation of the Friend Virus model for the development of improved adenovirus-vectored anti-retroviral vaccination strategies

We evaluated the suitability of the Friend Virus (FV) model for the development of improved adenovirus vectors for anti-retroviral vaccination using two types of adenovirus vectors, encoding F-MuLV Env and Gag, which differed only in their fiber genes (Ad5 and Ad5F35). Genetically FV-resistant C57BL/6 mice and highly susceptible CB6F1 hybrid mice were vaccinated by either homologous or heterologous prime-boost regimen. After FV challenge, viral loads in the spleens of C57BL/6 mice were reduced approximately 250-fold and were below the detection threshold in >50% of the mice. Vaccination outcome was critically influenced by the route of vector administration. In CB6F1 mice, vaccination resulted in reduced viremia, delayed onset of splenomegaly, and induction of FV-specific T cells as assessed by tetramer staining. Heterologous prime-boost vaccination resulted in significantly higher neutralizing antibody titers, translating into improved immune protection, in contrast to coexpression of cytokines. Our results suggest that the FV model can provide insight into the development of improved adenovirus vectors for HIV-1 vaccination.

Therapeutic vaccination against murine lymphoma by intratumoral injection of recombinant fowlpox virus encoding CD40 ligand

The interaction between CD40 ligand (CD40L, CD154) and its receptor CD40 on antigen-presenting cells is essential for the initiation of cell-mediated and humoral immune responses. Malignant B cells also express CD40 and respond to CD40L by enhancing expression of costimulatory molecules. In this study, we investigated the therapeutic antitumor effect of intratumoral administration of recombinant fowlpox virus encoding murine CD40L (rF-mCD40L) in a murine B-cell lymphoma model. BALB/c mice with established s.c. and widely metastatic A20 lymphoma tumors were treated with intratumoral injections of rF-mCD40L together with systemic chemotherapy. This combined chemoimmunotherapy resulted in complete tumor regression and long-term survival of the mice. Some tumor cells in the injected sites expressed the CD40L transgene and had increased expression of the CD80 and CD86 costimulatory molecules. The therapeutic effect was dependent on CD8 but not on CD4 T cells. Moreover, there was a requirement that the recombinant CD40L virus be injected directly into the tumor, as opposed to peritumoral or distant sites. Thus, rF-mCD40L injected directly into the tumor microenvironment enhances the immunogenicity of tumor B cells. The results support future plans for intratumoral injection of rF-mCD40L in patients with lymphoma.

In situ tumor vaccination with adenovirus vectors encoding measles virus fusogenic membrane proteins and cytokines

AIM: To evaluate whether intratumoral expression of measles virus fusogenic membrane glycoproteins H and F (MV-FMG), encoded by an adenovirus vector Ad.MV-H/F, alone or in combination with local coexpression of cytokines (IL-2, IL-12, IL-18, IL-21 or GM-CSF), can serve as a platform for inducing tumor-specific immune responses in colon cancer.

METHODS: We used confocal laser scanning microscopy and flow cytometry to analyze cell-cell fusion after expression of MV-FMG by dye colocalization. In a syngeneic bilateral subcutaneous MC38 and Colon26 colon cancer model in C57BL/6 and BALB/c mice, we assessed the effect on both the directly vector-treated tumor as well as the contralateral, not directly vector-treated tumor. We assessed the induction of a tumor-specific cytotoxic T lymphocyte (CTL) response with a lactate dehydrogenase (LDH) release assay.

RESULTS: We demonstrated in vitro that transduction of MC38 and Colon26 cells with Ad.MV-H/F resulted in dye colocalization, indicative of cell-cell fusion. In addition, in the syngeneic bilateral tumor model we demonstrated a significant regression of the directly vector-inoculated tumor upon intratumoral expression of MV-FMG alone or in combination with the tested cytokines. We observed the highest anti-neoplastic efficacy with MV-FMG and IL-21 coexpression. The degree of tumor regression of the not directly vector-treated tumor correlated with the anti-neoplastic response of the directly vector-treated tumor. This regression was mediated by a tumor-specific CTL response.

CONCLUSION: Our data indicate that intratumoral expression of measles virus fusogenic membrane glycoproteins is a promising tool both for direct tumor treatment as well as for tumor vaccination approaches that can be further enhanced by cytokine coexpression.

Combined liposome-mediated cytosine deaminase gene therapy with radiation in killing rectal cancer cells and xenografts in athymic mice

PURPOSE

The aim of this study was to assess the antitumor efficacy of combination of cytosine deaminase (CD) suicide gene therapy with radiation and to grope for new therapeutic strategy for local recurrent rectal cancer.

EXPERIMENTAL DESIGN

HR-8348 cell line of human rectal cancer was used to assess efficiency of transfection with plasmid pEGFP-N1 and PXJ41-CD. The cells were exposed to radiation followed by liposome-mediated transfection. Cell inhibition assay was done with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. Antitumor efficacy of combined liposome-mediated CD suicide gene therapy with radiation was determined by treatment of nude mice bearing HR-8348 cancer cell xenograft.

RESULTS

The efficiency of liposome-mediated CD gene transfection can be improved by radiation. With radiation at 2, 4, 6, and 8 Gy, the efficiency of liposome-mediated transfection increased from 21.3% to 62.2%, 78.0%, 83.2%, and 87.8%, respectively. CD expression was enhanced as well. Cancer cell inhibition experiment showed that combined liposome-mediated CD gene therapy with radiation had much stronger antitumor effect. With HR-8348 tumor xenograft model, suppression of tumor xenograft was observed. Compared with control group, tumor volume was inhibited by 81.5%, 48.5%, and 37.4%, respectively, in the combined CD/5-fluorocytosine with radiation group, CD/5-fluorocytosine group, and radiation group and the wet weight of tumor was decreased by 80%, 41.7%, and 37.7%, respectively.

CONCLUSION

These findings suggested that combination of liposome-mediated CD gene therapy with radiation is a safer and efficient anticancer method. Its therapeutic efficacy may meet clinical treatment on local recurrent rectal cancer.

Murine CD8 lymphocyte expansion in vitro by artificial antigen-presenting cells expressing CD137L (4-1BBL) is superior to CD28, and CD137L expressed on neuroblastoma expands CD8 tumour-reactive effector cells in vivo

The ability to expand tumour-infiltrating lymphocytes in vitro has been greatly enhanced by the use of antigen-independent mechanisms of immune cell costimulation. We have produced human, using the K562 cell line, and murine, using YAC-1 cells, artificial antigen presenting cells (aAPC) and demonstrate that these cell types stimulate murine lymphocyte populations in distinct ways. Using aAPC that have been transfected with CD137L (4-1BBL) and CD32 (FcRgammaII), as a means to bind anti-CD3 and anti-CD28 antibody, we found that CD4 cells preferentially expanded in vitro with K562 aAPC, while CD8 cells expanded with both K562 and YAC-1 aAPC. Co-stimulation mediated by CD137L on aAPC was superior to that mediated by anti-CD28 antibody. This was seen in both long and short-term expansion assays, and by the rapid induction of a CD8+ DX5+ population. DX5 serves, under these in vitro conditions, as a general marker for lymphocyte activation. In vivo, the superiority of CD137L was demonstrated by the induction of T helper 1 effectors seen in freshly isolated splenocytes from mice immunized with CD137L-expressing neuroblastoma tumour vaccines. The ability to stimulate a strong CD8 CTL response in vivo correlated with the induction of a DX5+ cell population in splenocytes with a memory-effector phenotype. The presence of this unique DX5+ cell population, phenotypically distinct with regards to CD69 and CD62L expression from DX5+ cells induced by aAPC in vitro, may be associated with the ability of CD137L to induce strong anti-tumour immunity.

CD40 ligand (CD154) improves the durability of respiratory syncytial virus DNA vaccination in BALB/c mice

Respiratory syncytial virus (RSV) infection is the single most important cause of serious acute respiratory illness in children <1 year of age worldwide, and is associated with life-threatening pneumonia or bronchiolitis in the elderly. Current vaccine strategies include live, attenuated virus, subunit and DNA vaccines, however, none have been sufficiently safe, or shown to induce satisfactory long-term immunity, thus immune modulators are being considered to enhance the effectiveness of RSV vaccines. In this study, we examine CD40 ligand (CD40L) as an immune modulator to enhance the durability of DNA vaccines encoding RSV F and/or G glycoproteins in BALB/c mice. The addition of CD40L to DNA vaccines encoding the F glycoprotein enhanced virus clearance and some aspects of the immune response to RSV challenge, suggesting that CD40L may enhance the durability of RSV DNA vaccines.

Improved antitumour immunity in murine neuroblastoma using a combination of IL-2 and IL-12

Neuroblastoma immunotherapy using cytokine-modified tumour cells has been tested in clinical trials. However, because of the complex nature of antitumour immune responses, a number of therapies may be required for complete tumour eradication and generation of systemic immunity. We report here the improved antitumour effect of two cytokines, interleukin-2 (IL-2) and interleukin-12 (IL-12), when coexpressed by neuroblastoma cell lines. Initially, transfection of human and mouse neuroblastoma cell lines resulted in high expression levels of biologically active IL-2 and IL-12 in vitro. These cytokines when expressed by transfected Neuro-2A cells completely abolished their in vivo tumorigenicity in a syngeneic neuroblastoma model. Vaccination of established tumours with IL-12-producing cells exhibited a clear effect with reduced tumour growth in the presence of IL-2. In vivo depletion studies showed that CD4(+) and CD8(+) T cells mediate the response against cytokine-producing cells. These results suggest that IL-2 and IL-12, when cotransfected in tumour cells, are effective against established disease and provide a promising immunotherapeutic approach for the treatment of neuroblastoma.

Enhancement of thymidine kinase-mediated killing of malignant glioma by BimS, a BH3-only cell death activator

Herpes simplex virus thymidine kinase (HSV-tk)/gancyclovir (GCV) therapy has the ability to inhibit tumor formation in animal models but the results of clinical trials have been disappointing. To improve the performance of tk/GCV therapy, we tried combination therapy designed to enhance its cytotoxic effects by introducing genes that induce apoptosis of the tumor cells through different pathways. We concentrated our efforts on the use of Bim, a BH3-only member of death activators in the Bcl-2 superfamily, because Bim is not involved in the pathways through which HSV-tk/GCV therapy induces apoptosis in malignant glioma cells. Among three alternative splicing variants, BimEL, BimL, and BimS, BimS lacks the binding domain for the dynein light chain LC8, which negatively regulates the proapoptotic function of BimEL and BimL. All four malignant glioma cell lines, U251, A172, T-430, and U373 underwent cell death after transfer of BimS using an adenovirus vector (AVC2). Intriguingly, combination of AVC2-BimS with AVC2-tk markedly increased the sensitivity of U251 cells to GCV both in vitro and in vivo. In contrast, AVC2-BimL did not induce significant cell death. These results indicated that BimS had the ability to improve the efficiency of HSV-tk/GCV therapy in the treatment of malignant glioma and suggested that the targeting of different proapoptotic pathways may be a useful strategy for the development of an effective gene therapy approach to treatment.

Midkine promoter-based adenoviral suicide gene therapy to midkine-positive pediatric tumor

BACKGROUND/PURPOSE

Suicide gene therapy based on the delivery of the herpes simplex virus thymidine kinase gene combined with ganciclovir (HSV-tk/GCV) is a promising approach for cancer treatment. Adenoviral (Ad) vectors are useful gene delivery vehicles for this approach; however, because these agents possess a high natural tropism for the liver, systems must be designed to avoid potential hepatotoxicity induced by expression of the therapeutic gene in this organ. It has been reported that Wilms' tumors or neuroblastomas express a high level of midkine (MK), a heparin-binding growth factor. In addition, no MK expression is observed in mouse or human liver. The authors investigated the application of MK promoter-based adenoviral gene therapy for MK-positive tumors, especially Wilms' tumors or neuroblastomas, and have shown that the MK promoter retains its fidelity in the adenoviral context, having low activity in liver and high activity in MK-positive tumor cells. We present herein the efficacy of in vivo tumor regression as well as prevention of lethal hepatic toxicity by using the MK promoter in an Ad vector-based HSV-tk/GCV treatment approach.

METHODS

Ad vectors, AdMKTK or AdCMVTK, encoding HSV-tk under the control of the MK or cytomegalovirus promoters, respectively, were injected systemically into mice, then hepatotoxicity and survival was monitored after GCV administration. In concurrent studies, the therapeutic impact of AdMKTK/GCV versus AdCMVTK/GCV on subcutaneous G-401 Wilms' tumors in nude mice was assessed.

RESULTS

By day 8 of systemic viral treatment, 4 of 5 mice treated with AdCMVTK/GCV had died, whereas all mice treated with AdMKTK/GCV survived at least 10 days. In the subcutaneous tumor study, equivalent regression of tumor was seen in the group that received AdMKTK as the group that received AdCMVTK intratumoral injection.

CONCLUSION

These data indicate that the MK promoter-based adenoviral suicide gene therapy is a unique therapeutic candidate for MK-positive tumors, Wilms' tumors, or neuroblastomas, by virtue of its mild hepatotoxicity and high efficacy against MK-positive tumors.

Potent antitumor effects of CD154 transduced tumor cells in experimental bladder cancer

PURPOSE

Current intravesical immunotherapy for bladder cancer with bacillus Calmette-Guerin instillations is standard treatment for patients with high risk superficial tumors but relapses are common. We evaluated the tumor vaccine concept in murine bladder cancer by comparing tumor cell transduction with genes coding for the immunostimulatory molecules CD154, interleukin (IL)-12 and CD80 to design a novel vaccination strategy.

MATERIALS AND METHODS

Adenoviral vectors were used to transduce murine bladder cancer MB-49 cells with genes coding for CD154, IL-12 and CD80. Parental or transduced MB-49 cells were injected subcutaneously into syngeneic mice. The effects of transgene expression on tumorigenicity and the generation of protective immunological memory against challenge with parental tumor were studied.

RESULTS

All 76 animals injected with parental MB-49 cells had tumors within 8 to 12 days. Tumor cell expression of CD154 combined with IL-12 completely inhibited tumor outgrowth with all 21 mice tumor-free and CD154 transduction alone was almost as effective with 33 of 35 tumor-free. IL-12 production by tumor cells delayed tumor outgrowth and 4 of 10 mice remained tumor-free. Over expression of CD80 had no effect on tumorigenicity. CD154 expressing tumors were rapidly infiltrated with large numbers of CD4+ and CD8+ T cells. Mice vaccinated 4 times with adenoviral CD154 transduced MB-49 cells were completely protected against challenge with parental tumor. Co-injection of CD154 modified cells with parental MB-49 cells retarded tumor growth.

CONCLUSIONS

Our experimental results suggest that the potent antitumor effects of CD154 gene transduction should be considered for immunostimulatory gene therapy for bladder cancer.

Autologous antileukemic immune response induced by chronic lymphocytic leukemia B cells expressing the CD40 ligand and interleukin 2 transgenes

Although the B cells of chronic lymphocytic leukemia (B-CLL cells) express both tumor-specific peptides and major histocompatibility complex (MHC) class I antigens, they lack the capacity for costimulatory signaling, contributing to their protection against host antitumor immunity. To stimulate CLL-specific immune responses, we sought to transfer the human CD40 ligand (hCD40L) gene to B-CLL cells, using an adenoviral vector, in order to upregulate costimulating factors on these cells. Because efficient gene transduction with adenoviral vectors requires the expression of virus receptors on target cells, including the coxsackievirus B-adenovirus receptors (CAR) and alpha(v) integrins, we cocultured B-CLL cells with human embryonic lung fibroblasts (MRC-5 line). This exposure led to increased expression of integrin alpha(v)beta3 on B-CLL cells, which correlated with higher transduction rates. Using this novel prestimulation system, we transduced B-CLL cells with the hCD40L gene. The Ad-hCD40L-infected cells had higher expression of B7 molecules and induced activation of autologous T cells in vitro, but these T cells could not recognize parental leukemic cells. By contrast, an admixture of Ad-hCD40L-positive cells and leukemic cells transduced with the human interleukin 2 (IL-2) gene produced greater T cell activation than did either immunostimulator population alone. Importantly, this combination generated autologous T cells capable of specifically recognizing parental B-CLL cells. These findings suggest that the combined use of genetically modified CD40L-expressing B-CLL cells in combination with IL-2-expressing B-CLL cells may induce therapeutically significant leukemia-specific immune responses.

Functional and selective targeting of adenovirus to high-affinity Fcgamma receptor I-positive cells by using a bispecific hybrid adapter

Adenovirus (Ad) efficiently delivers its DNA genome into a variety of cells and tissues, provided that these cells express appropriate receptors, including the coxsackie-adenovirus receptor (CAR), which binds to the terminal knob domain of the viral capsid protein fiber. To render CAR-negative cells susceptible to Ad infection, we have produced a bispecific hybrid adapter protein consisting of the amino-terminal extracellular domain of the human CAR protein (CARex) and the Fc region of the human immunoglobulin G1 protein, comprising the hinge and the CH2 and CH3 regions. CARex-Fc was purified from COS7 cell supernatants and mixed with Ad particles, thus blocking Ad infection of CAR-positive but Fc receptor-negative cells. The functionality of the CARex domain was further confirmed by successful immunization of mice with CARex-Fc followed by selection of a monoclonal anti-human CAR antibody (E1-1), which blocked Ad infection of CAR-positive cells. When mixed with Ad expressing eGFP, CARex-Fc mediated an up to 250-fold increase of transgene expression in CAR-negative human monocytic cell lines expressing the high-affinity Fcgamma receptor I (CD64) but not in cells expressing the low-affinity Fcgamma receptor II (CD32) or III (CD16). These results open new perspectives for Ad-mediated cancer cell vaccination, including the treatment of acute myeloid leukemia.

CD40 ligand (CD154) enhances the Th1 and antibody responses to respiratory syncytial virus in the BALB/c mouse

CD40 ligand (CD40L) is a cell surface costimulatory molecule expressed mainly by activated T cells. CD40L is critically important for T-B cell and T cell-dendritic cell interactions. CD40L expression promotes Th1 cytokine responses to protein Ags and is responsible for Ig isotype switching in B cells. Respiratory syncytial virus (RSV) is an important pathogen of young children and the elderly, which causes bronchiolitis and pneumonia. Studies of mice infected with RSV suggest that a Th2 cytokine response may be responsible for enhanced pulmonary disease. To investigate the effect CD40L has on RSV immunity, mice were infected simultaneously with RSV and either an empty control adenovirus vector or one expressing CD40L or were coimmunized with plasmid DNA vectors expressing CD40L and RSV F and/or G proteins and subsequently challenged with RSV. The kinetics of the intracellular and secreted cytokine responses, the cytotoxic T lymphocyte precursor frequency, NO levels in lung lavage, rates of virus clearance, and anti-RSV Ab titers were determined. These studies show that coincident expression of CD40L enhances the Th1 (IL-2 and IFN-gamma) cytokine responses, increases the expression of TNF-alpha and NO, accelerates virus clearance, and increases the anti-F and anti-G Ab responses. These data suggest that CD40L may have the adjuvant properties needed to optimize the safety and efficacy of RSV vaccines.

Intravesical liposome-mediated interleukin-2 gene therapy in orthotopic murine bladder cancer model

Using a novel orthotopic MBT-2 murine bladder tumor model, we evaluated the feasibility of intravesical gene therapy utilizing a cationic liposome, DMRIE/DOPE. Superficial bladder tumors were consistently established by intravesical instillation of 5x10(5) MBT-2 cells in syngeneic C3H female mice. In situ gene transfer to bladder tumors was accomplished via intravesical instillation of plasmid DNA/DMRIE/DOPE lipoplex. Beta-Galactosidase (beta-gal) gene expression was preferentially evident in bladder tumors and was present for at least 7 days after a single 30 min in situ transfection. Murine interleukin-2 (IL-2) gene was used for treatment of 3-day-old pre-established bladder tumors. Forty percent of animals treated with IL-2 gene were completely free of tumors by 60 days following the initial tumor implantation, while all control groups treated with beta-gal gene died. Those animals initially cured of pre-established tumors were completely resistant to a subsequent tumor re-challenge and their splenocyte-derived cytotoxic T lymphocytes were shown to be specific to MBT-2 cells, indicating that immunological memory against MBT-2 tumors was elicited by the treatment. These results demonstrate the possibility of an effective clinical application of this in situ intravesical IL-2 gene delivery system to high-risk superficial bladder tumors, obviating a need for tumor procurement and ex vivo gene transfer.

Recombinant adenovirus vectors for cytokine gene therapy in mice

BACKGROUND

Adenoviruses have several specific features useful for gene therapy. They infect various lineages of cells irrespective of cell cycle status. However, the exact mechanism of their infection and in vivo kinetics as a gene expression vector have not been elucidated.

OBJECTIVE

Using adenovirus vectors expressing marker genes, we examined the infectivity of these vectors (including cellular and tissue tropism), the duration and intensity of transgene expression, and the side effects.

METHODS

Various cells were infected with adenovirus expressing LacZ gene at various doses, and beta-galactosidase activity was measured and compared in relation with dose, time course, and cellular vitronectin receptor. Mice were injected with adenoviruses expressing LacZ, luciferase and GM-CSF, and in vivo gene expression was examined.

RESULTS

Adenovirus infection induced viral dose-dependent transgene expression that persisted for 2 weeks. Adherent cells were infected much more efficiently than nonadherent cells, probably because the former expressed much higher levels of the vitronectin receptor, one of the main receptors for adenovirus. Studies performed in mice with luciferase-expressing adenovirus revealed that the liver was the main target organ after intravenous injection and showed that the intravenous route was superior to other routes with regard to transgene expression. After intravenous injection of adenovirus expressing human GM-CSF, there was a transient and dose-dependent increase in the serum level of this cytokine. Administration of adenovirus expressing mouse GM-CSF enhanced hematopoiesis in the spleen and bone marrow.

CONCLUSION

These results indicated that adenoviruses can be used for in vivo cytokine gene therapy but suggested the necessity of taking into consideration the route of administration, the duration of transgene expression, the toxic dose, and host immune reactions.

Adenovirus mediated gene therapy in a glioblastoma vaccine model; specific antitumor immunity and abrogation of immunosuppression

Clinical trials are being performed using tumor genetically engineered to produce cytokines as a vaccine. The design of such a vaccine may be made more effective by further study using in-vitro as well as in-vivo models. We studied an in-vitro tumor 'vaccine' model in glioblastoma. We have demonstrated high efficiency transfection of the Interleukin-2 (IL-2) gene into glioblastoma cell lines using adenoviral vectors. Glioblastoma cell lines transduced with this vector could produce high levels of IL-2 for up to 2 weeks, long enough to elicit an antitumor immune response. We studied tumor/effector cell interactions using cytotoxicity assays coupled with flow cytometric analysis. Activation of CD8+ and expansion of CD3+/CD16+ effector cell subpopulations were observed, suggesting the generation of a specific anti-tumor response and the potential for systemic immunity. We demonstrated that glioblastoma produce immunosuppressive factors which reduce the antitumor response by peripheral blood effector cells. These immunosuppressive factors could be neutralized to improve antitumor response. A better understanding of tumor/effector cell interactions may improve the design of gene therapy trials.

IL-2 Adenovector-Transduced Autologous Tumor Cells Induce Antitumor Immune Responses in Patients With Neuroblastoma

In many different murine models, the immunogenicity of tumor cells can be increased by transduction with a range of immunostimulatory genes, inducing an immune response that causes regression of pre-existing unmodified tumor cells. To investigate the relevance of these animal models to pediatric malignancy, we used autologous unirradiated tumor cells transduced with an adenovirus-IL-2 to immunize 10 children with advanced neuroblastoma. In a dose-escalation study, we found that this tumor immunogen induced a moderate local inflammatory response consisting predominantly of CD4+ T lymphocytes, and a systemic response, with a rise in circulating CD25+and DR+ CD3+ T cells. Patients also made a specific antitumor response, manifest by an IgG antitumor antibody and increased cytotoxic T-cell killing of autologous tumor cells. Clinically, five patients had tumor responses after the tumor immunogen alone (one complete tumor response, one partial response, and three with stable disease). Four of these five patients were shown to have coexisting antitumor cytotoxic activity, as opposed to only one of the patients with nonresponsive disease. These results show a promising correlation between preclinical observations and clinical outcome in this disease, and support further exploration of the approach for malignant diseases of children.

© 1998 by The American Society of Hematology.

IL-2 Adenovector-Transduced Autologous Tumor Cells Induce Antitumor Immune Responses in Patients With Neuroblastoma

In many different murine models, the immunogenicity of tumor cells can be increased by transduction with a range of immunostimulatory genes, inducing an immune response that causes regression of pre-existing unmodified tumor cells. To investigate the relevance of these animal models to pediatric malignancy, we used autologous unirradiated tumor cells transduced with an adenovirus-IL-2 to immunize 10 children with advanced neuroblastoma. In a dose-escalation study, we found that this tumor immunogen induced a moderate local inflammatory response consisting predominantly of CD4+ T lymphocytes, and a systemic response, with a rise in circulating CD25+and DR+ CD3+ T cells. Patients also made a specific antitumor response, manifest by an IgG antitumor antibody and increased cytotoxic T-cell killing of autologous tumor cells. Clinically, five patients had tumor responses after the tumor immunogen alone (one complete tumor response, one partial response, and three with stable disease). Four of these five patients were shown to have coexisting antitumor cytotoxic activity, as opposed to only one of the patients with nonresponsive disease. These results show a promising correlation between preclinical observations and clinical outcome in this disease, and support further exploration of the approach for malignant diseases of children.

© 1998 by The American Society of Hematology.

Interleukin-2 gene-modified allogeneic tumor cells for treatment of relapsed neuroblastoma

Tumor cells that have been genetically modified to express immunostimulatory genes will induce effective antitumor responses in a range of syngeneic animal models. For human applications, transduced autologous tumor cell lines are often difficult or impossible to prepare, so that there are strong incentives for substituting a standardized allogeneic tumor cell line. However, such lines may be inferior immunogens if they differ from host tumors in the antigens they express. We have evaluated the safety, immunostimulatory, and antitumor activity of an interleukin-2-secreting allogeneic neuroblastoma cell line in 12 children with relapsed stage IV neuroblastoma. They received two to four subcutaneous injections of cells in a dose-escalating schedule, up to a maximum of 10(8) cells per injection. There was induration and pruritus at the injection site, and skin biopsies revealed mild panniculitis with CD3+ cells surrounding scanty residual tumor cells. There was a limited but significant peripheral monocytosis. No patient showed any increase in direct cytotoxic effector function against the immunizing cell line, but 3 patients had a rise in the frequency of neuroblastoma-reactive cytotoxic T lymphocyte precursor cells. One child had > 90% tumor response (PR), 7 had stable disease, and 4 had progressive disease in response to vaccine alone. Although these results offer some encouragement for the continued pursuit of allogeneic vaccine strategies in human cancer, the antitumor immune responses we observed are inferior to those obtained in an earlier immunization study using autologous neuroblastoma cells. Hence, we suggest that this earlier approach remains preferable, its difficulties notwithstanding.

In vivo therapy of hepatocellular carcinoma with a tumor-specific adenoviral vector expressing interleukin-2

A recombinant adenovirus (AdVAFP1-IL2) containing the murine alpha-fetoprotein (AFP) promoter was constructed to direct hepatocellular carcinoma (HCC)-specific expression of the human interleukin-2 (IL-2) gene. In vitro testing of AdVAFP1-IL2 showed HCC-specific IL-2 gene expression three to four orders of magnitude higher in AFP-producing HCC lines compared to non-AFP producing non-HCC lines. The in vivo efficacy and tumor specificity of AdVAFP1-IL2 was evaluated compared to AdVCMV-IL2 (in which the IL-2 gene is driven by the strong constitutive cytomegalovirus promoter) in the treatment of established human HCC (Hep 3B/Hep G2) xenografts growing in CB-17/SCID mice. Intratumoral injection of AdV resulted in growth retardation and regression in a majority of established hepatomas, but with a much wider therapeutic index and less systemic toxicity using the AFP vector. This study illustrates the superiority of using transcriptionally targeted recombinant AdV vectors in cytokine-based gene therapy.

Gene marking and gene therapy for transplantation medicine

The classic application for gene therapy is in the correction of single gene defects, although this has been complicated by the low efficiency of gene transfer into hematopoietic cells. Gene therapy, however, has potential for the modulation of tumor cell growth, drug sensitivity, and antitumor immune responses. In addition, gene marking can be used, in spite of this limited transfer efficiency, to provide information on hematopoiesis, sources of cancer relapse after stem cell transplant, and the relative efficacy of graft manipulation techniques. This article reviews the applications of gene therapy and gene marking in transplantation medicine.