Adenovirus CD40 Ligand Gene Therapy Counteracts Immune Escape Mechanisms in the Tumor Microenvironment

Chemotherapeutic agents enhance AAV2-mediated gene transfer into breast cancer cells promoting CD40 ligand-based immunotherapy

PURPOSE

Supplementing conventional treatment with gene therapy to induce an immune response might be beneficial to cancer patients. In this study, we evaluated the efficiency of transduction of breast cancer cells with recombinant adeno-associated virus (rAAV) and effects of cytotoxic agents used in chemotherapy. Furthermore, the capacity of tumor cells expressing transgenic CD40 ligand (CD40L) to stimulate dendritic cells was measured.

METHODS

Breast cancer cell lines were infected with a rAAV encoding the enhanced green fluorescent protein (EGFP) or murine CD40L and transgene expression was analyzed by flow cytometry. Stimulation of isolated human dendritic cells by CD40L-expressing tumor cells was quantified by measuring secreted interleukin 12.

RESULTS

Infection with an EGFP-encoding rAAV resulted in variable fractions (14-93%, mean 42%) of transgene-expressing cells. Pre-incubation of MM 157, MM 231, and MCF7 cells with epirubicin or carboplatin substantially increased AAV-mediated transgene expression. rAAV/CD40L was used to generate CD40L-transgenic tumor cells, which specifically activated immature dendritic cells, as confirmed by blocking with an antibody binding to CD40L.

CONCLUSIONS

The efficiency of rAAV-mediated gene transfer into breast cancer cells is significantly higher than previously reported and can be further enhanced by co-administration of chemotherapeutic agents. We also confirmed that breast cancer cells can activate human dendritic cells after infection with a CD40L-encoding rAAV.

Adenovirus-mediated CD40 ligand therapy induces tumor cell apoptosis and systemic immunity in the TRAMP-C2 mouse prostate cancer model

BACKGROUND

The interaction between CD40 ligand (CD40L) and CD40 on antigen presenting cells is essential for the initiation of antigen-specific T-cell responses, whereas CD40L stimulation of CD40+ tumor cells can induce cellular apoptosis. We investigated the anti-tumor effects induced by CD40L gene transfer into the mouse prostate adenocarcinoma cell line TRAMP-C2, both in vitro and in vivo.

METHODS

TRAMP-C2 cells were transduced with an adenoviral vector encoding CD40L (AdCD40L). The induced expression of co-stimulatory molecules and cell viability was analyzed. AdCD40L-transduced TRAMP-C2 cells were used in prophylactic vaccination studies, while therapeutic studies were performed using peritumoral injections of AdCD40L.

RESULTS

AdCD40L yielded reduced TRAMP-C2 cell viability and induced apoptosis in vitro. Vaccination with CD40L-expressing TRAMP-C2 cells induced anti-tumor immunity and peritumoral AdCD40L injections induced tumor growth suppression.

CONCLUSIONS

Our observations highlight the therapeutic potential of using AdCD40L as a monotherapy or in combination with conventional chemotherapy or novel therapies (e.g., oncolytic viruses). The use of AdCD40L offers an attractive option for future clinical trials.

Stimulation through CD40 on Mouse and Human Renal Cell Carcinomas Triggers Cytokine Production, Leukocyte Recruitment, and Antitumor Responses that Can Be Independent of Host CD40 Expression

CD40, a member of the TNFR superfamily, is expressed on a variety of host immune cells, as well as some tumors. In this study, we show that stimulation of CD40 expressed on both mouse and human renal carcinoma cells (RCCs) triggers biological effects in vitro and in vivo. Treatment of the CD40+ Renca mouse RCC tumor cells in vitro with an agonistic anti-CD40 Ab induced strong expression of the genes and proteins for GM-CSF and MCP-1, and induced potent chemotactic activity. Similarly, administration of alphaCD40 to both wild-type and CD40-/- mice bearing Renca tumors resulted in substantial amounts of TNF-alpha and MCP-1 in the serum, increased the number of total splenocytes and MHC class II+ CD11c+ leukocytes, and when combined with IFN-gamma, inhibited the progression of established Renca tumors in vivo in both wild-type and CD40-/- mice. Similarly, treatment of CD40+ A704 and ACHN human RCC lines with mouse anti-human CD40 Ab induced strong expression of genes and proteins for MCP-1, IL-8, and GM-CSF in vitro and in vivo. Finally, in SCID mice, the numbers of ACHN pulmonary metastases were dramatically reduced by treatment with species-specific human CD40 Ab. These results show that CD40 stimulation of CD40+ tumor cells can enhance immune responses and result in antitumor activity.

Dendritic cells engineered to express CD40L continuously produce IL12 and resist negative signals from Tr1/Th3 dominated tumors

TNFalpha-matured dendritic cells (DCs) pulsed with tumor antigens are being evaluated as cancer vaccines. It has been shown that DCs produce IL12 during a limited time span and subsequently enter a stage of IL12 exhaustion. If DCs are generated ex vivo, the patient could receive IL12-exhausted DCs which may be detrimental for stimulating anti-tumor Th1 responses. Furthermore, many cancer patients exhibit a cytokine profile skewed toward IL10 and TGFbeta. This immunological profile, called the Tr1/Th3 response, is associated with the presence of regulatory T-cells. Tr1/Th3 responses potently inhibit DC maturation, thereby regulating Th1 responses. In the present study, we produced genetically engineered DCs that continuously express Th1-related cytokines such as IL12, and resist negative signals from Tr1/Th3-dominated bladder carcinoma cells. Human immature DCs were genetically engineered by adenoviral vectors to express CD40L, or were treated with TNFalpha as a positive control for maturation. The expression of different Th1/Th3 and inflammatory cytokines was monitored. IL12 and IFNgamma were expressed by CD40L-engineered DCs, while TNFalpha-matured DCs lacked IFNgamma and exhibited low IL12 expression. The addition of recombinant IL10 to genetically engineered DCs did not abolish their Th1 profile. Likewise, coculture with tumor cell lines expressing TGFbeta with or without recombinant IL10 did not revert to the engineered DCs. We further demonstrate that the resistance of CD40L-expressing DCs to TGFbeta and IL10 may be due to decreased levels of TGFbeta and IL10 receptors. Thus, CD40L-engineered DCs are robust Th1-promoting ones that are resistant to Tr1/Th3-signaling via IL10 and TGFbeta.

Cancer and pregnancy share similar mechanisms of immunological escape

BACKGROUND

Despite the fact that trophoblasts and cancer are both immunogenic, they are able to escape from host immunosurveillance, and the precise mechanisms involved in this process are surprisingly similar in both situations.

METHODS

A literature review of studies on immunological changes occurring during normal pregnancy and cancer was performed.

RESULTS

Loss or downregulation of classical HLA antigens as well as the presence of non-classical HLA-G molecules, a Th2 cytokine activity shift, secretion of immunosuppressive factors and blocking antibodies and finally induction of apoptosis in immunocytes seem to be the most effective mechanisms of immunological escape in pregnancy and cancer.

CONCLUSIONS

The process of immunological escape in cancer and pregnancy is based on similar mechanisms.

AdCD40LGene Therapy Counteracts T Regulatory Cells and Cures Aggressive Tumors in an Orthotopic Bladder Cancer Model

PURPOSE

The aim of this study was to develop an immunostimulating gene therapy for the treatment of orthotopic bladder carcinoma by transferring the gene for CD40L into the tumor site. CD40L stimulation of dendritic cells induces interleukin-12 expression that drives Th1 type of immune responses with activation of cytotoxic T cells.

EXPERIMENTAL DESIGN

The gene for murine CD40L was transferred into bladders of tumor-bearing mice using an adenoviral vector construct. To facilitate viral uptake, the bladders were pretreated with Clorpactin. Survival of mice as well as transgene expression and immunologic effect, such as resistance to tumor challenge and presence of T regulatory cells, were monitored.

RESULTS

On viral vector instillation, CD40L expression could be detected by reverse transcription-PCR. As a sign of transgene function, interleukin-12 (IL-12) expression was significantly increased. AdCD40L gene therapy cured 60% of mice with preestablished tumors. The cured mice were completely resistant to subcutaneous challenge with MB49 tumor cells, whereas the growth of a syngeneic irrelevant tumor was unaltered. Furthermore, the mRNA expression level of the T regulatory cell transcription factor Foxp3 was evaluated both in tumor biopsies and lymph nodes. There were no differences within the tumors of the different treatment groups. However, Foxp3 mRNA levels were down-regulated in the lymph nodes of AdCD40L-treated mice. Correspondingly, T cells from AdCD40L-treated mice were not able to inhibit proliferation of naive T cells as opposed to T cells from control-treated, tumor-bearing mice.

CONCLUSIONS

AdCD40L gene therapy evokes Th1 cytokine responses and counteracts T regulatory cell development and/or function.

Simultaneous targeting of CD3 on T cells and CD40 on B or dendritic cells augments the antitumor reactivity of tumor-primed lymph node cells

To date, molecular targets chosen for Ab activation to generate antitumor effector cells have been confined on T cells, such as TCR/CD3, CD28, CD137 (4-1BB), CD134 (OX40), and inducible costimulator. In this report we investigated the immune function of murine tumor-draining lymph node (TDLN) cells after simultaneous Ab targeting of CD3 on T cells and CD40 on APCs. Anti-CD3 plus anti-CD40-activated TDLN cells secreted significantly higher amounts of IFN-gamma, but less IL-10, compared with anti-CD3-activated cells. In adoptive immunotherapy, ligation of CD3 and CD40 resulted in the generation of more potent effector cells in mediating tumor regression. Freshly harvested TDLN cells were composed of approximately 60% CD3+ T cells, 30-35% CD19+ B cells, 5% CD11c+ dendritic cells (DC), and few CD14+ or NK cells (each <3%). CD40 was distributed predominantly on B cells and DCs. Cell depletion indicated that simultaneous targeting was toward CD3 on T cells and CD40 on APCs, respectively. Elimination of APCs completely abrogated the augmented antitumor responses induced by anti-CD40. Either B cell or DC removal partially, but significantly, reduced the therapeutic efficacy conferred by CD40 engagement. Furthermore, the immunomodulation function of anti-CD40 was associated with its capability to increase IL-12 secretion while inhibiting IL-4 production. Our study establishes a role for CD40 expressed on B cells or DCs in the costimulation of TDLN cells. Eliciting antitumor activity via simultaneous targeting of CD3 on T cells and CD40 on APCs is relevant for the design of effective T cell-based cancer immunotherapy.

The immunotherapy of prostate and bladder cancer

The role of the immune system in controlling the growth of tumour cells is highly complex and has been extensively debated. It is well documented that the immune system controls virally induced cancers, and there is evidence for a role of specific immunity in other types of tumours. The greater understanding of the regulation and optimization of adoptive, specific immune responses, and the better characterization of tumour-associated antigens indicate the way for active specific vaccination and cell therapy in urological tumours. Currently, bacille Calmette Guerin immunotherapy is established for localized bladder cancer and many experimental immunotherapies are under evaluation. Here we review some timely aspects of tumour immunology, and describe the current status and development of immunotherapy in prostate and bladder cancer.

Gene modification strategies to induce tumor immunity

The immune system provides an attractive option for use in cancer therapy. Our increasing understanding of the molecular events important in the generation of an effective immune response presents us with the opportunity to manipulate key genes to boost the immune response against cancer. Genetic modification is being employed to enhance a range of immune processes including antigen presentation, activation of specific T cells, and localization of immune effectors to tumors. In this review, we describe how many diverse cell types, including dendritic cells, T cells, and tumor cells, are being modified with a variety of genes, including those encoding antigens, cytokines, and chemokines, in order to enhance tumor immunity.

Tumor-induced suppression of interferon-γ production and enhancement of interleukin-10 production by natural killer (NK) cells: paralleled to CD4+ T cells

The predominance of type two cytokines in syngeneic B16 tumor-bearing mice was confirmed by analysing supernatant contents and mRNA copies of IFN-gamma, IL-4, IL-5, IL-10 and IL-13 from splenocytes. The cytokine-producing lymphocytes were then examined by double-staining flowcytometry. Both CD4+IFN-gamma+ T cells and DX5+IFN-gamma+ NK cells from spleen significantly declined, interestingly, the declining degrees of DX5+IFN-gamma+ NK cells were much greater than those of CD4+IFN-gamma+ T cells by the percentage in whole NK or T cells or the absolute amounts per spleen at early tumor stage (day 10) or tumor-advanced stage (day 20). In contrast to DX5+IFN-gamma+ NK cells, DX5+IL-10+ NK cells increased during tumor progression, the increasing degrees of DX5+IL-10+ NK cells were also much greater than those of CD4+IL-10+ T cells by the percentage or the absolute amounts. Though the percentage of DX5+IL-4+ NK cells only increased in early tumor stage (day 10), the increasing degree was also greater than that of CD4+IL-4+ T cells. In 20xfield view under laser confocal microscope, the mean numbers of DX5+IFN-gamma+ NK cells and CD4+IFN-gamma+ T cells dramatically declined after tumor inoculation. These results suggest that cytokines produced by NK cells, at least partly, account for the balance of type one and two cytokines as done by T cells, and in some conditions, that the NK1 or NK2 cells were possibly more sensitive to tumor progression.

In Vivo Retroviral Mediated Gene Transfer into Bladder Urothelium Results in Preferential Transduction of Tumoral Cells

OBJECTIVES

Superficial bladder tumours are at high risk for recurrence, relapse after resection, escape to intravesical immunotherapy and they may become invasive. New therapeutics are therefore needed to achieve cure. Thus, gene therapy is an attractive new treatment modality for malignant bladder tumours. The purpose of this study was to evaluate the feasibility and the efficiency of retroviral mediated reporter gene transfer into malignant urothelial cells both in vitro and in vivo.

METHODS

We evaluated the feasibility of the transfection of bladder tumour with direct intravesical instillation of a defective retrovirus. The vector was derived from LXSN. The efficiency of transduction with the Moloney Leukaemia Murine virus-based vector, amphotrophic retroviral vector, was monitored through the expression of two marker genes (nls-LacZ and NeoR). The canine animal was chosen since it can present with spontaneous bladder carcinomas mimicking human pathology. Primary cultures of two normal canine bladder urothelium and two canine primary bladder tumours were first studied. We then investigated in vivo, in two normal and two spontaneous tumour bearing dogs, the transduction of urothelial cells following direct intravesical instillation of 2.10(4) to 3.10(6) of the retroviral vector.

RESULTS

Transduced cells were evidenced in all primary cultures of canine normal urothelium and transitional cell carcinoma. Bladder biopsies from sound dogs instilled with the viral solution showed long lasting transduction up to 60 days long. Bladder cryosections from tumour-bearing dogs displayed transduction of superficial layers of urothelial cancer cells without passing through lamina propria. In vivo transduction was evidenced in 1 to 15% (mean 5%) of the cells in the tumours and preferentially addressed malignant cells. Normal epithelium either originating from sound or tumour-bearing animals was not transduced.

CONCLUSION

These results demonstrate for the first time the feasibility of in vivo retroviral transduction of bladder cancer using a clinically relevant procedure.

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