In vitro activation of cancer patient-derived dendritic cells by tumor cells genetically modified to express CD154

Development of a Bladder Cancer-on-a-Chip Model to Assess Bladder Cancer Cell Invasiveness

We have developed a bladder cancer-on-a-chip model which supports the 3D growth of cells and can be used to assess and quantify bladder cancer cell invasiveness in a physiologically appropriate environment. Three bladder cancer cell lines (T24, J82, and RT4) were resuspended in 50% Matrigel® and grown within a multi-channel organ-on-a-chip system. The ability of live cells to invade across into an adjacent 50% Matrigel®-only channel was assessed over a 2-day period. Cell lines isolated from patients with high-grade bladder cancer (T24 and J82) invaded across into the Matrigel®-only channel at a much higher frequency compared to cells isolated from a patient with low-grade cancer (RT4) (p < 0.001). The T24 and J82 cells also invaded further distances into the Matrigel®-only channel compared to the RT4 cells (p < 0.001). The cell phenotype within the model was maintained as assessed by cell morphology and immunohistochemical analysis of E-cadherin. Treatment with ATN-161, an α5β1 integrin inhibitor and well-known migrastatic drug, caused a dose-dependent decrease in the invasiveness of the J82 cells (p < 0.01). The combined data demonstrate that our bladder cancer-on-a-chip model supports the retention of the bladder cancer cell phenotype and can be used to reproducibly assess and quantify the invasiveness of live bladder cancer cells.

Non-stem bladder cancer cell-derived extracellular vesicles promote cancer stem cell survival in response to chemotherapy

BACKGROUND

Chemosenstive non-stem cancer cells (NSCCs) constitute the bulk of tumors and are considered as part of the cancer stem cell (CSC) niche in the tumor microenvironment (TME). Tumor-derived extracellular vesicles (EVs) mediate the communication between tumors and the TME. In this study, we sought to investigate the impacts of EVs released by NSCCs on the maintenance of CSC properties and chemoresistance.

METHODS

We employed murine MB49 bladder cancer (BC) sub-lines representing CSCs and NSCCs as a model system. Chemotherapy drugs were used to treat NSCCs in order to collect conditioned EVs. The impacts of NSCC-derived EVs on CSC progression were evaluated through sphere formation, cytotoxicity, migration, and invasion assays, and by analyzing surface marker expression on these BC cells. Differential proteomic analyses were conducted to identify cargo protein candidates involved in the EV-mediated communication between NSCCs and CSCs.

RESULTS

NSCC-derived EVs contained cargo proteins enriched in proteostasis-related functions, and significantly altered the development of CSCs such that they were more intrinsically chemoresistant, aggressive, and better able to undergo self-renewal.

CONCLUSIONS

We thus identified a novel communication mechanism whereby NSCC-EVs can alter the relative fitness of CSCs to promote disease progression and the acquisition of chemoresistance.

Enhanced metastatic potential in the MB49 urothelial carcinoma model

Recent data suggest that patients with a basal/stem-like bladder cancer (BC) subtype tend to have metastatic disease, but this is unconfirmed. Here we report the identification of murine MB49 cell line sub-clones with stem-like characteristics in culture. Subcutaneous implantation of S2 and S4 MB49 sub-clones into immunocompetent mice resulted in lung metastases in 50% and 80% of mice respectively, whereas none of the mice implanted with the parental cells developed metastasis. Gene profiling of cells cultured from S2 and S4 primary and metastatic tumors revealed that a panel of genes with basal/stem-like/EMT properties is amplified during metastatic progression. Among them, ITGB1, TWIST1 and KRT6B are consistently up-regulated in metastatic tumors of both MB49 sub-clones. To evaluate clinical relevance, we examined these genes in a human public dataset and found that ITGB1 and KRT6B expression in BC patient tumor samples are positively correlated with tumor grade. Likewise, the expression levels of these three genes are correlated with worse clinical outcomes. This MB49 BC metastatic pre-clinical model provides a unique opportunity to validate and recapitulate results discovered in patient studies and to pursue future mechanistic therapeutic interventions for BC metastasis.

Activation of myeloid and endothelial cells by CD40L gene therapy supports T-cell expansion and migration into the tumor microenvironment

CD40 is an interesting target in cancer immunotherapy due to its ability to stimulate T-helper 1 immunity via maturation of dendritic cells and to drive M2 to M1 macrophage differentiation. Pancreatic cancer has a high M2 content that has shown responsive to anti-CD40 agonist therapy and CD40 may thus be a suitable target for immune activation in these patients. In this study, a novel oncolytic adenovirus armed with a trimerized membrane-bound extracellular CD40L (TMZ-CD40L) was evaluated as a treatment of pancreatic cancer. Further, the CD40L mechanisms of action were elucidated in cancer models. The results demonstrated that the virus transferring TMZ-CD40L had oncolytic capacity in pancreatic cancer cells and could control tumor progression. TMZ-CD40L was a potent stimulator of human myeloid cells and T-cell responses. Further, CD40L-mediated stimulation increased tumor-infiltrating T cells in vivo, which may be due to a direct activation of endothelial cells to upregulate receptors for lymphocyte attachment and transmigration. In conclusion, CD40L-mediated gene therapy is an interesting concept for the treatment of tumors with high levels of M2 macrophages, such as pancreatic cancer, and an oncolytic virus as carrier of CD40L may further boost tumor killing and immune activation.

AdCD40L--crossing the valley of death?

CD40-mediated cancer therapy has been under development since it became clear that CD40 plays a profound role in the stimulation of adaptive immune responses. Further, CD40 signaling on tumor cells may lead to growth arrest or even apoptosis that improves therapy outcome. The therapeutic window is appealing since the immune system is selective and normal cells do not apoptose upon CD40 signaling. AdCD40L is an adenoviral-based immunostimulatory gene therapy under evaluation for its efficacy to treat cancer. Because of its nature, the adenoviral backbone will stimulate TLRs while CD40L potentiates the shifts toward Th1 type of immunity. AdCD40L has shown efficacy in various murine models, and safety studies have been performed on dog patients and in human clinical trials. AdCD40L has been used for both ex vivo gene modification of tumor cell vaccines as well as for direct intratumoral injections. Lately, an oncolytic vector has been used to further increase the eradication of solid tumors that as a consequence further boosts the release of tumor antigens and creates danger signaling in the tumor micro milieu. This review discusses the currently unfolding mechanisms of action of AdCD40L gene therapy and its possibilities to reach clinical care.

Local AdCD40L gene therapy is effective for disseminated murine experimental cancer by breaking T-cell tolerance and inducing tumor cell growth inhibition

CD40 ligand (CD40L) is one of the most potent stimulators of Th1-type immunity through its maturation of dendritic cells that, in turn, stimulate effector cells such as T cells and NK cells. Lately, CD40-mediated cell growth inhibition and apoptosis have been in focus for the development of novel cancer treatment regiments, including recombinant soluble CD40L or CD40-stimulating antibodies. In this study, intravesical CD40L gene transfer through adenoviral vectors (AdCD40L) was used to treat an aggressive model of disseminated bladder cancer (MB49/C57BL/6). Three weekly AdCD40L vector instillations increased overall survival of tumor-bearing mice (mean 18.5 d, control mice 13 d). Furthermore, bladder tumors were eradicated (2 of 10) simultaneously as lung metastases (6 of 10) were cleared. FoxP3 levels were similar in the tumors of AdCD40L-treated mice and control mice but the tumor-infiltrating effector T cells in AdCD40L-treated mice were cytotoxic (CD107a+) in contrast to those in control-treated tumors. Furthermore, AdCD40L gene therapy could induce cell growth inhibition and cell death in the MB49 tumor cells in vitro and in vivo. However, this effect was not potent enough to cure growing tumors in immunodeficient mice. In conclusion, AdCD40L gene therapy is potent for disseminated cancer both by activation of T cells and controlling tumor cell growth and viability.

Immunogene therapy against colon cancer metastasis using an adenovirus vector expressing CD40 ligand

BACKGROUND

Colon cancer is one of the most common cancers worldwide, and liver metastasis is a poor prognostic factor for all types of digestive cancers, including colon cancer. We studied CD40 ligand (CD40L)-mediated immunogene therapy for metastatic liver cancer in rats.

METHODS

We studied whether in vitro infection of a rat colon cancer cell line (RCN9) with an adenoviral-vector that expresses the CD40L (AxCAmCD40L) induced CD40L expression. In vivo to confirm the antitumor effect induced by AxCAmCD40L, the tumor cells that had been transduced by AxCAmCD40L were implanted into the subcutaneous tissues of syngenic rats (prevention model) or AxCAmCD40L was injected into the tumor tissues of the rats (treatment model). Furthermore, immune cells including NK cells, cytotoxic T cells, and tumor-specific antibodies induced by AxCAmCD40L were examined.

RESULTS

Immunogene therapy using AxCAmCD40L suppressed the tumor growth strongly or reduced tumor size in the prevention model and treatment model. NK cells, cytotoxic T cells, and tumor-specific antibodies contributed to this antitumor effect in both groups.

CONCLUSION

These observations suggest that CD40L-mediated immunogene therapy for metastatic colon cancer in the liver and lungs is effective and is mediated by the activation of both the cellular and humoral immune systems.

Cationic liposome-mediated transfection of CD40 ligand gene inhibits hepatic tumor growth of hepatocellular carcinoma in mice

OBJECTIVE

To evaluate the efficacy of cationic liposome-mediated CD40 ligand (CD40L) gene therapy for hepatocellular carcinoma.

METHODS

1x10(6) of parental H22 cells or H22 cells transfected with the expression vector containing murine CD40L cDNA encoding the entire coding region (pcDNA3.1(+)-mCD40L) were inoculated subcutaneously into the left flanks of syngenic BALB/C mice. The tumor-bearing mice (tumor nodules 10 mm in maximal diameter) received the treatment of the intratumoral injection of pcDNA3.1(+)-mCD40L/Transfectam, pcDNA3.1(+), or phosphate-buffered saline (PBS), or no treatment. The mice were monitored for tumor growth weekly. We examined mCD40L messenger ribonucleic acid (mRNA) expression by reverse transcription polymerase chain reaction (RT-PCR) and the histologic changes in tumors at two weeks after intratumoral injection using immunohistochemical staining of tumor tissues.

RESULTS

All mice inoculated with parental H22 cells developed a tumor subcutaneously, and the tumor size increased progressively within three weeks. However, the mice receiving H22-CD40L cells exhibited complete regression of the tumor two weeks after tumor cell inoculation. The tumor-bearing animals with the treatment of pcDNA3.1(+) or PBS, or without treatment had progressive tumor growth, while those mice treated with pcDNA3.1(+)-mCD40L exhibited a significant inhibition of tumor growth. RT-PCR analysis showed that 783-bp fragments corresponding to the mCD40L mRNA were amplified only from pcDNA3.1(+)-mCD40L treated tumors. The tumor samples from pcDNA3.1(+)-mCD40L-treated mice showed significant lymphocyte infiltration, apoptotic bodies, and confluent necrosis in the tumor tissues.

CONCLUSION

The tumorigenicity of CD40L-expressing cells was abrogated when the cells were implanted subcutaneously. In vivo gene therapy of established liver tumor nodules in mice by the intratumoral injection of pcDNA3.1(+)-mCD40L led to significant tumor inhibition. There was mCD40L mRNA expression in the tissues from pcDNA3.1(+)-mCD40L-treated tumors. The intratumoral injection of pcDNA3.1(+)-mCD40L induced a strong inflammatory, mainly lymphocytic infiltration of the tumor, and increased the necrotic rate of the neoplastic cells.

Efficient adenovector CD40 ligand immunotherapy of canine malignant melanoma

Cutaneous canine melanomas are usually benign in contrast to human malignant melanoma. However, the canine oropharyngeal, uveal, and mucocutaneous neoplasms are aggressive and have metastatic potential. Surgery and to a lesser extent radiotherapy and chemotherapy are widely adopted treatments but are seldom curative in advanced stages. The similarities between human and canine melanoma make spontaneous canine melanoma an excellent disease model for exploring novel therapies. Herein, we report the first 2 adenovector CD40L immunogene (AdCD40L) treatments of aggressive canine malignant melanoma. Case no. 1 was an advanced stage III oral melanoma that was cured from malignant melanoma with 2 intratumor AdCD40L injections before cytoreductive surgery. After treatment, the tumor tissue was infiltrated with T lymphocytes and B lymphocytes suggesting immune activation. This dog survived 401 days after the first round of gene therapy and was free of melanoma at autopsy. Case no. 2 had a conjunctival malignant melanoma with a rapid progression. This case was treated with 6 AdCD40L injections over 60 days. One hundred and twenty days after start of gene therapy and 60 days after the last injection, the tumor had regressed dramatically, and the dog had a minimal tumor mass and no signs of progression or metastasis. Our results indicate that AdCD40L immunogene therapy is beneficial in canine malignant melanoma and could be considered for human malignant melanoma as well.

A novel chromogranin-A promoter-driven oncolytic adenovirus for midgut carcinoid therapy

PURPOSE

The use of replication-selective oncolytic adenoviruses is an emerging therapeutic approach for cancer, which thus far has not been employed for carcinoids. We therefore constructed Ad[CgA-E1A], a novel replication-selective oncolytic adenovirus, where the chromogranin A (CgA) promoter controls expression of the adenoviral E1A gene.

EXPERIMENTAL DESIGN

The Ad[CgA-E1A] virus was evaluated for E1A protein expression, replication ability, and cytolytic activity in various cell lines. It was also evaluated for treatment of xenografted human carcinoid tumors in nude mice. To use Ad[CgA-E1A] for the treatment of carcinoid liver metastases, it is important that normal hepatocytes do not support virus replication to minimize hepatotoxicity. We therefore evaluated CgA protein expression in normal hepatocytes. We also evaluated CgA gene expression in normal hepatocytes and microdissected tumor cells from carcinoid metastases.

RESULTS

We found that Ad[CgA-E1A] replicates similarly to wild-type virus in tumor cells with neuroendocrine features, including the BON carcinoid cell line and the SH-SY-5Y neuroblastoma cell lines, whereas it is attenuated in other cell types. Thus, cells where the CgA promoter is active are selectively killed. We also found that Ad[CgA-E1A] is able to suppress fast-growing human BON carcinoid tumors in nude mice. Furthermore, CgA is highly expressed in microdissected cells from carcinoid metastases, whereas it is not expressed in normal hepatocytes.

CONCLUSION

Ad[CgA-E1A] is an interesting agent for the treatment of carcinoid liver metastases in conjunction with standard therapy for these malignancies.

Construction and expression of a eukaryotic expression plasmid containing human CD40 ligand in human hepatocellular carcinoma cell line HepG2 and its effect on apoptosis

AIM: To construct and express a eukaryotic expression plasmid containing human CD40 ligand (CD40L) in human hepatocellular carcinoma cell line HepG2 for the biological function study of CD40L on HepG2 cells.

METHODS: Human CD40L cDNA was synthesized by reverse transcription-polymerase chain reaction (RT-PCR) with the specific primers from the RNA of human peripheral blood monocyte (PBMC) and directly ligated into the eukaryotic expression vector pcDNA^TM3.1/myc-His(-)A through digestion with specific restriction endonuclease. The recombined plasmid was transformed into the E. coli DH5α to amplify CD40L gene. Then HepG2 cells were divided into 4 groups. The cells in group A were transfected with the recombined plasmid, and group B with the blank plasmid (not containing CD40L cDNA). The cells in group C were just normally cultured, and the ones in group D weren't transfected but added G418 as the control for transfection. The expression of CD40L and CD40 were detected by RT-PCR and fluorescent activated cell sorter (FACS) in HepG2 cells, and the apoptosis, cell cycle, as well as Fas expression, were measured by FACS.

RESULTS: The full-length human CD40L cDNA was successfully cloned into the eukaryotic vector pcDNA^TM3.1/myc-His(-)A. The recombinant plasmid was stably transfected into group A and the rate of CD40L expression was 39.7%. There was no CD40L expression in group B and C. The rates of CD40 expression in group A, B and C were 15.4%, 31.7% and 28.5%, respectively. The apoptotic rate of group A was 45.0±0.3%, but neither group B or C showed obvious apoptosis (P <0.01). Compared with group C, a larger proportion of cells in group A was restrained at G0/G1 phase (90.4±1.3% vs 60.6±1.5%, P <0.01), while the proportions of the cells in S phase (6.32±1.0% vs 12.0±0.7%) and G2/M phase (3.3±0.7% vs 27.3±1.2%) were reduced (both P <0.01). The expression of Fas in group A showed marked increase as compared with that in group B and C (27.8±1.5% vs 3.2±0.8%, 4.2±1.0%, respectively, both P <0.01).

CONCLUSION: The eukaryotic expression plasmid pcDNA^TM3.1/myc-His(-)A can be stably expressed in HepG2 cell line. CD40L-induced apoptosis of HepG2 is correlated with the increased expression of Fas and cell cycle arrest.

CpG oligonucleotide therapy cures subcutaneous and orthotopic tumors and evokes protective immunity in murine bladder cancer

Bacillus Calmette-Guerin (BCG) instillation is standard immunotherapy for superficial bladder carcinoma. However, many patients become refractory to BCG, giving impetus to the development of alternative therapies. CpG oligodeoxynucleotide (ODN) therapy has been shown to promote T(H)1-oriented antitumor responses in various tumor models. To investigate its therapeutic effect in bladder cancer, we used different CpG ODNs to treat C57BL/6 mice bearing the subcutaneous murine bladder tumor MB49. CpG type B ODN 1668 was superior at inhibiting tumor growth, leading to complete regression of large tumors. More importantly, CpG ODN 1668 also regressed orthotopically growing MB49 tumors for the first time. Rechallenge of CpG ODN-cured mice with MB49 showed that a majority of the mice were protected long term, demonstrating that CpG ODN therapy evokes a memory response. Adenoviral vectors (Ad) encoding CD40L, tumor necrosis factor-related activation-induced cytokine, lymphotactin, interleukin (IL) 2, and IL-15 were also investigated. AdCD40L and AdIL-15 transduction could abolish MB49 tumorigenicity, and these vectors were combined with CpG ODN 1668 to investigate any enhanced effects. No such effects were seen. All groups of mice treated with CpG ODNs, alone or in combination with adenoviral vector, exhibited increased serum concentrations of IL-12, indicative of a T(H)1 response. Our results show that CpG ODN therapy cures established subcutaneous and orthotopic bladder cancer via a T(H)1-mediated response and provides long-lasting protective immunity.

Therapeutic effect of CD40 ligand gene on hepatocelluLar carcinoma in mice

AIM: To investigate the anti-tumor effect of murine CD40 ligand gene in vivo.

METHODS: Parental H22 cells and H22 cells transfected with pcDNA3.1⁺-mCD40L (H22-CD40L)(1×10⁶) were inoculated subcutaneously into the left flanks of syngenic Balb/c mice respectively. Tumor-bearing mice (tumor nodules were 10 mm in maximal diameter) were treated by intratumoral injection of either pcDNA3.1⁺-mCD40L/Transfectam (treating group) or Transfectam or pcDNA3.1⁺ or RPMI1640 (control). All the mice were monitored for tumor growth weekly. The mCD40L mRNA expression was detected by reverse transcription polymerase chain reaction (RT-PCR) and the histological changes were observed after routine HE staining.

RESULTS: All the mice inoculated with parental H22 cells developed a subcutaneous tumor, and the tumor size increased progressively within 3 weeks. However, the mice received H22-CD40L cells exhibited complete regression 2 weeks after inoculation. Tumor-bearing animals received Transfectam or pcDNA3.1⁺ or RPMI1640 had progressive tumor growth, while those treated with pcDNA3.1⁺-mCD40L exhibited a significant inhibition of tumor growth. A fragment of 783 bp corresponding to the mCD40L mRNA was amplified only from pcDNA3.1⁺-mCD40L treatmented tumors. Tumor samples from pcDNA3.1⁺-mCD40L-treated mice showed significant lymphocyte infiltration, apoptosis and confluent necrosis.

CONCLUSION: The tumorigenicity of CD40L-expressing cells abrogated when they were implanted subcutaneously. In vivo gene therapy for established liver tumor nodules in mice by intratumor injection of pcDNA3.1⁺-mCD40L led to significant tumor inhibition. mCD40L mRNA is expressed in pcDNA3.1⁺-mCD40L treated tumors. Intratumoral injection of pcDNA3.1⁺-mCD40L induces a strong inflammatory, mainly lymphocyte infltration and necrosis of tumor cells.

Immunotherapy for superficial bladder cancer

The treatment of superficial bladder cancer requires adjuvant therapies besides transurethral resection because of a high recurrence rate after this standard treatment alone. Current adjuvant therapies involve intravesical chemotherapy for patients at low and intermediate risk for recurrence and progression, and intravesical bacillus Calmette-Guérin for patients at intermediate and high risk. However, these adjuvant therapies fail in a significant number of patients, dictating the need for new and improved adjuvant treatment modalities for superficial bladder cancer. Immunotherapy aiming at the modulation of the immune system of the patient is a promising alternative adjuvant. This review discusses the current status of the clinical development of various immunotherapy approaches for superficial bladder cancer, including passive immunotherapy, immune stimulants, immunogene therapy and cancer vaccination.

Construction of recombinant eukaryotic expression plasmid containing murine CD40 ligand gene and its expression in H22 cells

AIM: To construct a recombinant murine CD40 ligand (mCD40L) eukaryotic expression vector for gene therapy and target therapy of hepatocellular carcinoma (HCC).

METHODS: mCD40L cDNA was synthesized by RT-PCR with the specific primers and directly cloned into T vector to generate middle recombinant. After digestion with restriction endonuclease, the target fragment was subcloned into the multi-clone sites of the eukaryotic vector. The constructed vector was verified by enzyme digestion and sequencing, and the product expressed was detected by RT-PCR and immunofluorescence methods.

RESULTS: The full-length mCD40L-cDNA was successfully cloned into the eukaryotic vector through electrophoresis, and mCD40L gene was integrated into the genome of infected H22 cells by RT-PCR. Murine CD40L antigen molecule was observed in the plasma of mCD40L-H22 by indirect immuno-fluorescence staining.

CONCLUSION: The recombined mCD40L eukaryotic expression vector can be expressed in H22 cell line. It provides experimental data for gene therapy and target therapy of hepatocellular carcinoma.

Platelet factor 4 in conjunction with IL‐4 directs differentiation of human monocytes into specialized antigen‐ presenting cells

Recent evidence suggests that platelets are not only involved in haemostatic processes but also modulate immune responses. As antigen-presenting cells (APC) are of crucial importance for the regulation of immunity, in this study we wanted to define the role of platelet factor 4 (PF-4) as one of the major platelet-derived chemokines on the transition of monocytes into APCs. Our experiments show that within 3 days PF-4 in conjunction with IL-4 induces a rapid differentiation of monocytes into APC. These PFAPC (PF-4/IL-4 differentiated APC) display unique phenotypical and functional characteristics setting them apart from macrophages and conventional dendritic cells. Functional studies revealed that PFAPC preferentially stimulated proliferation of lymphocytes and lytic NK activity while they induced only moderate cytokine responses. Beyond day 3 of differentiation, PFAPC became less immunostimulatory and maintained their capacity to phagocytose particulate material even after LPS-induced maturation. These experiments uncover a previously unknown role for the platelet-derived CXC-chemokine PF-4 in differentiation of human APC. Our data further support the newly discovered function of platelets in immunomodulation and provide new evidence for a rapid transition of monocytes into APC under the influence of inflammatory stimuli.

Cloning and expression of murine CD40 ligand gene

AIM: To study sub-cloning and expression of murine CD40 ligand (mCD40L) gene in eukaryotic cells as a basis for further study.

METHODS: The mCD40L gene fragment was amplified by using RT-PCR and sub-cloned into eukaryotic expression plasmid pcDNA3.1⁺, then transfected into H22 cell with Lipofectamine. After 2-3 weeks selection with G418, DNA was extracted from infected cells and tested by RT-PCR, indirect immunofulorescence were used to detect the expression of mCD40 L.

RESULTS: The insertion mCD40L gene fragment in the eukaryotic expression plasmid was confirmed by enzyme digestion with EcoR I and Nhe I and sequence analysis. The result RT-PCR showed that mCD40L gene had been integrated into the genome of infected H22 cells. Indirect immunofulorescence analysis showed that mCD40L had been expressed in these cells.

CONCLUSION: The mCD40L gene is integrated into eukaryotic cells with eukaryotic expression plasmid and target gene is expressed efficiently.

Functional transfer of CD40L gene in human B-cell precursor ALL blasts by second-generation SIN lentivectors

Three different second-generation lentiviral self-inactivating vectors containing CMV, EF1alpha and PGK promoter, respectively, and all carrying the exogenous GFP gene, were compared for expression in human B-cell precursor ALL blasts. At a comparable percentage of transduction and vector DNA copy number, CMV clearly showed better efficiency of transcription. Human bone marrow stromal cells were favored compared to the MRC-5 cell line, as support for cell viability during infection. Cells were infected and analyzed after variable culture times ranging from 4 to 12 days, to reduce the possibility of pseudotransduction. In 10/14 samples, we detected more than 20% GFP-positive cells after exposure to high-titer viral supernatants. We then tested a similar vector carrying the human CD40L cDNA and, in similar infection conditions, obtained more than 20% transduction in 6/6 samples. The levels of transduction obtained were sufficient to induce the upregulation of CD83 molecule in cocultured immature dendritic cells.