A combined treatment regimen of MGMT-modified γδ T cells and temozolomide chemotherapy is effective against primary high grade gliomas.

Chemotherapeutic drugs such as the alkylating agent Temozolomide (TMZ), in addition to reducing tumor mass, can also sensitize tumors to immune recognition by transient upregulation of multiple stress induced NKG2D ligands (NKG2DL). However, the potential for an effective response by innate lymphocyte effectors such as NK and γδ T cells that recognize NKG2DL is limited by the drug's concomitant lymphodepleting effects. We have previously shown that modification of γδ T cells with a methylguanine DNA methyltransferase (MGMT) transgene confers TMZ resistance via production of O6-alkylguanine DNA alkyltransferase (AGT) thereby enabling γδ T cell function in therapeutic concentrations of TMZ. In this study, we tested this strategy which we have termed Drug Resistant Immunotherapy (DRI) to examine whether combination therapy of TMZ and MGMT-modified γδ T cells could improve survival outcomes in four human/mouse xenograft models of primary and refractory GBM. Our results confirm that DRI leverages the innate response of γδ T cells to chemotherapy-induced stress associated antigen expression and achieves synergies that are significantly greater than either individual approach.

Blocking PD1/PDL1 Interactions Together with MLN4924 Therapy is a Potential Strategy for Glioma Treatment.

OBJECTIVE: MLN4924, a pharmacological inhibitor of cullin neddylation, resulted in glioma cell apoptosis, deregulation of the S-phase of DNA synthesis and thus, offers great potential for the treatment of brain tumours. However, targeting the neddylation pathway with an MLN4924 treatment stabilized the hypoxia-inducible factor 1A (HIF1A), which is one of the main transcriptional enhancers of the immune checkpoint molecule PDL1 (programmid death ligand-1) in cancer cells. The influence of immune checkpoint molecules on glioma progression has recently been discovered; PDL1 overexpression in gliomas corresponds to a significant shortening of patient survival and a decrease of the anti-tumour immune response. We hypothesize that i) PDL1 is up-regulated in gliomas after treatment with MLN4924 and induces T-cell energy; ii) co-utilization of the PD1/PDL1 blockage with MLN4924 therapy may reduce T-cell energy and may engage MLN4924-induced tumour disruption with the immune response. METHODS: PDL1 expression and its immunosuppressive role in gliomas, glioma microenvironments, and after treatments with MLN4924 were assessed by utilizing methods of immunohistochemistry, molecular biology, and biochemistry. RESULTS: We confirmed PDL1 overexpression in clinical brain tumour samples, PDGx and established glioma cell lines, extracellular media from glioma cells, and CSF (cerebrospinal fluid) samples from tumour-bearing mice. Our primary T-cell based assays verified that the up-regulation of PDL1 in tumour cells protects gliomas from T-cell treatment and reduces T-cell activation. We found that a pharmacological inhibitor of cullin neddylation, MLN4924, exhibited strong cytotoxicity towards PDGx and established glioma cell lines, in vitro, with an IC50's range from 0.2 to 3 uM. However, we observed a significant increase of HIF1A and PDL1 in mRNA and protein levels in all glioma cell lines after treatment with MLN4924. The MLN4924-dependent induction of PDL1 in gliomas resulted in T-cell energy, which was blocked by a blockage of the PD1/PDL1 interaction. CONCLUSION: We conclude that i) PDL1 up-regulation in gliomas and the glioma microenvironment is an important chemotherapeutic target; ii) MLN4924 therapy, combined with a blockage of the PD1/PDL1 pathway, should be considered as a potential strategy for glioma treatment.

Correction: In Vitro Pre-Clinical Validation of Suicide Gene Modified Anti-CD33 Redirected Chimeric Antigen Receptor T-Cells for Acute Myeloid Leukemia.

[This corrects the article DOI: 10.1371/journal.pone.0166891.].

In Vitro Pre-Clinical Validation of Suicide Gene Modified Anti-CD33 Redirected Chimeric Antigen Receptor T-Cells for Acute Myeloid Leukemia.

BACKGROUND: Approximately fifty percent of patients with acute myeloid leukemia can be cured with current therapeutic strategies which include, standard dose chemotherapy for patients at standard risk of relapse as assessed by cytogenetic and molecular analysis, or high-dose chemotherapy with allogeneic hematopoietic stem cell transplant for high-risk patients. Despite allogeneic hematopoietic stem cell transplant about 25% of patients still succumb to disease relapse, therefore, novel strategies are needed to improve the outcome of patients with acute myeloid leukemia. METHODS AND FINDINGS: We developed an immunotherapeutic strategy targeting the CD33 myeloid antigen, expressed in ~ 85-90% of patients with acute myeloid leukemia, using chimeric antigen receptor redirected T-cells. Considering that administration of CAR T-cells has been associated with cytokine release syndrome and other potential off-tumor effects in patients, safety measures were here investigated and reported. We genetically modified human activated T-cells from healthy donors or patients with acute myeloid leukemia with retroviral supernatant encoding the inducible Caspase9 suicide gene, a ΔCD19 selectable marker, and a humanized third generation chimeric antigen receptor recognizing human CD33. ΔCD19 selected inducible Caspase9-CAR.CD33 T-cells had a 75±3.8% (average ± standard error of the mean) chimeric antigen receptor expression, were able to specifically lyse CD33+ targets in vitro, including freshly isolated leukemic blasts from patients, produce significant amount of tumor-necrosis-factor-alpha and interferon-gamma, express the CD107a degranulation marker, and proliferate upon antigen specific stimulation. Challenging ΔCD19 selected inducible Caspase9-CAR.CD33 T-cells with programmed-death-ligand-1 enriched leukemia blasts resulted in significant killing like observed for the programmed-death-ligand-1 negative leukemic blasts fraction. Since the administration of 10 nanomolar of a non-therapeutic dimerizer to activate the suicide gene resulted in the elimination of only 76.4±2.0% gene modified cells in vitro, we found that co-administration of the dimerizer with either the BCL-2 inhibitor ABT-199, the pan-BCL inhibitor ABT-737, or mafosfamide, resulted in an additive effect up to complete cell elimination. CONCLUSIONS: This strategy could be investigated for the safety of CAR T-cell applications, and targeting CD33 could be used as a 'bridge" therapy for patients coming to allogeneic hematopoietic stem cell transplant, as anti-leukemia activity from infusing CAR.CD33 T-cells has been demonstrated in an ongoing clinical trial. Albeit never performed in the clinical setting, our future plan is to investigate the utility of iC9-CAR.CD33 T-cells as part of the conditioning therapy for an allogeneic hematopoietic stem cell transplant for acute myeloid leukemia, together with other myelosuppressive agents, whilst the activation of the inducible Caspase9 suicide gene would grant elimination of the infused gene modified T-cells prior to stem cell infusion to reduce the risk of engraftment failure as the CD33 is also expressed on a proportion of the donor stem cell graft.

Effect of HSV-IL12 Loaded Tumor Cell-Based Vaccination in a Mouse Model of High-Grade Neuroblastoma.

We designed multimodal tumor vaccine that consists of irradiated tumor cells infected with the oncolytic IL-12-expressing HSV-1 virus, M002. This vaccine was tested against the syngeneic neuroblastoma mouse model Neuro 2a injected into the right caudate nucleus of the immunocompetent A/J mice. Mice were vaccinated via intramuscular injection of multimodal vaccine or uninfected irradiated tumor cells at seven and 14 days after tumor establishment. While there was no survival difference between groups vaccinated with cell-based vaccine applied following tumor injection, a premunition prime/boost vaccination strategy produced a significant survival advantage in both groups and sustained immune response to an intracranial rechallenge of the same tumor. The syngeneic but unrelated H6 hepatocellular tumor cell line grew unrestricted in vaccinated mice, indicative of vaccine-mediated specific immunity to Neuro 2a tumors. Longitudinal analyses of tumor-infiltrating lymphocytes revealed a primary adaptive T cell response involving both CD4+ and CD8+ T cell subsets. Spleen cell mononuclear preparations from vaccinated mice were significantly more cytotoxic to Neuro 2a tumor cells than spleen cells from control mice as demonstrated in a four-hour in vitro cytotoxicity assay. These results strongly suggest that an irradiated whole cell tumor vaccine incorporating IL-12-expressing M002 HSV can produce a durable, specific immunization in a murine model of intracranial tumor.

Robust DNA Damage Response and Elevated Reactive Oxygen Species in TINF2-Mutated Dyskeratosis Congenita Cells.

Dyskeratosis Congenita (DC) is an inherited multisystem premature aging disorder with characteristic skin and mucosal findings as well as a predisposition to cancer and bone marrow failure. DC arises due to gene mutations associated with the telomerase complex or telomere maintenance, resulting in critically shortened telomeres. The pathogenesis of DC, as well as several congenital bone marrow failure (BMF) syndromes, converges on the DNA damage response (DDR) pathway and subsequent elevation of reactive oxygen species (ROS). Historically, DC patients have had poor outcomes following bone marrow transplantation (BMT), perhaps as a consequence of an underlying DNA hypersensitivity to cytotoxic agents. Previously, we demonstrated an activated DDR and increased ROS, augmented by chemotherapy and radiation, in somatic cells isolated from DC patients with a mutation in the RNA component of telomerase, TERC. The current study was undertaken to determine whether previous findings related to ROS and DDR in TERC patients' cells could be extended to other DC mutations. Of particular interest was whether an antioxidant approach could counter increased ROS and decrease DC pathologies. To test this, we examined lymphocytes from DC patients from different DC mutations (TERT, TINF2, and TERC) for the presence of an active DDR and increased ROS. All DC mutations led to increased steady-state p53 (2-fold to 10-fold) and ROS (1.5-fold to 2-fold). Upon exposure to ionizing radiation (XRT), DC cells increased in both DDR and ROS to a significant degree. Exposing DC cells to hydrogen peroxide also revealed that DC cells maintain a significant oxidant burden compared to controls (1.5-fold to 3-fold). DC cell culture supplemented with N-acetylcysteine, or alternatively grown in low oxygen, afforded significant proliferative benefits (proliferation: maximum 2-fold increase; NAC: 5-fold p53 decrease; low oxygen: maximum 3.5-fold p53 decrease). Together, our data supports a mechanism whereby telomerase deficiency and subsequent shortened telomeres initiate a DDR and create a pro-oxidant environment, especially in cells carrying the TINF2 mutations. Finally, the ameliorative effects of antioxidants in vitro suggest this could translate to therapeutic benefits in DC patients.

The safety of allogeneic innate lymphocyte therapy for glioma patients with prior cranial irradiation.

The standard treatment of high-grade glioma presents a combination of radiotherapy, chemotherapy and surgery. Immunotherapy is proposed as a potential adjunct to standard cytotoxic regimens to target remaining microscopic disease following resection. We have shown ex vivo expanded/activated γδ T cells to be a promising innate lymphocyte therapy based on their recognition of stress antigens expressed on gliomas. However, successful integration of γδ T cell therapy protocols requires understanding the efficacy and safety of adoptively transferred immune cells in the post-treatment environment. The unique features of γδ T cell product and the environment (hypoxia, inflammation) can affect levels of expression of key cell receptors and secreted factors and either promote or hinder the feasibility of γδ T cell therapy. We investigated the potential for the γδ T cells to injure normal brain tissue that may have been stressed by treatment. We evaluated γδ T cell toxicity by assessing actual and correlative toxicity indicators in several available models including: (1) expression of stress markers on normal primary human astrocytes (as surrogate for brain parenchyma) after irradiation and temozolomide treatment, (2) cytotoxicity of γδ T cells on normal and irradiated primary astrocytes, (3) microglial activation and expression of stress-induced ligands in mouse brain after whole-brain irradiation and (4) expression of stress-induced markers on human brain tumors and on normal brain tissue. The lack of expression of stress-induced ligands in all tested models suggests that γδ T cell therapy is safe for brain tumor patients who undergo standard cytotoxic therapies.

DNA damage responses and oxidative stress in dyskeratosis congenita.

Dyskeratosis congenita (DC) is an inherited multisystem disorder of premature aging, cancer predisposition, and bone marrow failure caused by selective exhaustion of highly proliferative cell pools. DC patients also have a poor tolerance to chemo/radiotherapy and bone marrow transplantation. Although critically shortened telomeres and defective telomere maintenance contribute to DC pathology, other mechanisms likely exist. We investigate the link between telomere dysfunction and oxidative and DNA damage response pathways and assess the effects of antioxidants. In vitro studies employed T lymphocytes from DC subjects with a hTERC mutation and age-matched controls. Cells were treated with cytotoxic agents, including Paclitaxel, Etoposide, or ionizing radiation. Apoptosis and reactive oxygen species (ROS) were assessed by flow cytometry, and Western blotting was used to measure expression of DNA damage response (DDR) proteins, including total p53, p53S15, and p21(WAF). N-acetyl-cysteine (NAC), an antioxidant, was used to modulate cell growth and ROS. In stimulated culture, DC lymphocytes displayed a stressed phenotype, characterized by elevated levels of ROS, DDR and apoptotic markers as well as a proliferative defect that was more pronounced after exposure to cytotoxic agents. NAC partially ameliorated the growth disadvantage of DC cells and decreased radiation-induced apoptosis and oxidative stress. These findings suggest that oxidative stress may play a role in the pathogenesis of DC and that pharmacologic intervention to correct this pro-oxidant imbalance may prove useful in the clinical setting, potentially alleviating untoward toxicities associated with current cytotoxic treatments.

Derivation of a myeloid cell-binding adenovirus for gene therapy of inflammation.

The gene therapy field is currently limited by the lack of vehicles that permit efficient gene delivery to specific cell or tissue subsets. Native viral vector tropisms offer a powerful platform for transgene delivery but remain nonspecific, requiring elevated viral doses to achieve efficacy. In order to improve upon these strategies, our group has focused on genetically engineering targeting domains into viral capsid proteins, particularly those based on adenovirus serotype 5 (Ad5). Our primary strategy is based on deletion of the fiber knob domain, to eliminate broad tissue specificity through the human coxsackie-and-adenovirus receptor (hCAR), with seamless incorporation of ligands to re-direct Ad tropism to cell types that express the cognate receptors. Previously, our group and others have demonstrated successful implementation of this strategy in order to specifically target Ad to a number of surface molecules expressed on immortalized cell lines. Here, we utilized phage biopanning to identify a myeloid cell-binding peptide (MBP), with the sequence WTLDRGY, and demonstrated that MBP can be successfully incorporated into a knob-deleted Ad5. The resulting virus, Ad.MBP, results in specific binding to primary myeloid cell types, as well as significantly higher transduction of these target populations ex vivo, compared to unmodified Ad5. These data are the first step in demonstrating Ad targeting to cell types associated with inflammatory disease.

Functional Sindbis virus replicative complexes are formed at the plasma membrane.

Formation of virus-specific replicative complexes (RCs) in infected cells is one of the most intriguing and important processes that determine virus replication and ultimately their pathogenesis on the molecular and cellular levels. Alphavirus replication was known to lead to formation of so-called type 1 cytopathic vacuoles (CPV1s), whose distinguishing feature is the presence of numerous membrane invaginations (spherules) and accumulation of viral nonstructural proteins (nsPs) at the cytoplasmic necks of these spherules. These CPV1s, modified endosomes and lysosomes, were proposed as the sites of viral RNA synthesis. However, our recent studies have demonstrated that Sindbis virus (SINV)-specific, double-stranded RNA (dsRNA)- and nonstructural protein (nsP)-containing RCs are initially formed at the plasma membrane. In this new study, we present extensive evidence that (i) in cells of vertebrate origin, at early times postinfection, viral nsPs colocalize with spherules at the plasma membrane; (ii) viral dsRNA intermediates are packed into membrane spherules and are located in their cavities on the external surface of the plasma membrane; (iii) formation of the membrane spherules is induced by the partially processed nonstructural polyprotein P123 and nsP4, but synthesis of dsRNA is an essential prerequisite of their formation; (iv) plasma membrane-associated dsRNA and protein structures are the active sites of single-stranded RNA (ssRNA) synthesis; (v) at late times postinfection, only a small fraction of SINV nsP-containing complexes are relocalized into the cytoplasm on the endosome membrane. (vi) pharmacological drugs inhibiting different endocytotic pathways have either only minor or no negative effects on SINV RNA replication; and (vii) in mosquito cells, at any times postinfection, dsRNA/nsP complexes and spherules are associated with both endosomal/lysosomal and plasma membranes, suggesting that mechanisms of RC formation may differ in cells of insect and vertebrate origins.

Targeting of mesenchymal stem cells to ovarian tumors via an artificial receptor.

BACKGROUND: Mesenchymal Progenitor/Stem Cells (MSC) respond to homing cues providing an important mechanism to deliver therapeutics to sites of injury and tumors. This property has been confirmed by many investigators, however, the efficiency of tumor homing needs to be improved for effective therapeutic delivery. We investigated the feasibility of enhancing MSC tumor targeting by expressing an artificial tumor-binding receptor on the MSC surface. METHODS: Human MSC expressing an artificial receptor that binds to erbB2, a tumor cell marker, were obtained by transduction with genetically modified adenoviral vectors encoding an artificial receptor (MSC-AR). MSC-AR properties were tested in vitro in cell binding assays and in vivo using two model systems: transient transgenic mice that express human erbB2 in the lungs and ovarian xenograft tumor model. The levels of luciferase-labeled MSCs in erbB2-expressing targeted sites were evaluated by measuring luciferase activity using luciferase assay and imaging. RESULTS: The expression of AR enhanced binding of MSC-AR to erbB2-expressing cells in vitro, compared to unmodified MSCs. Furthermore, we have tested the properties of erbB2-targeted MSCs in vivo and demonstrated an increased retention of MSC-AR in lungs expressing erbB2. We have also confirmed increased numbers of erbB2-targeted MSCs in ovarian tumors, compared to unmodified MSC. The kinetic of tumor targeting by ip injected MSC was also investigated. CONCLUSION: These data demonstrate that targeting abilities of MSCs can be enhanced via introduction of artificial receptors. The application of this strategy for tumor cell-based delivery could increase a number of cell carriers in tumors and enhance efficacy of cell-based therapy.

A fiber-modified mesothelin promoter-based conditionally replicating adenovirus for treatment of ovarian cancer.

PURPOSE: Recently, virotherapy has been proposed as a new therapeutic approach for ovarian cancer. Conditionally replicative adenoviruses (CRAd) may contain tumor-specific promoters that restrict virus replication to cancer cells. Mesothelin, a cell surface glycoprotein, is overexpressed in ovarian cancer but not in normal ovarian tissues. The purpose of this study was to explore the therapeutic utility of a mesothelin promoter-based CRAd in a murine model of ovarian cancer, using noninvasive in vivo imaging. EXPERIMENTAL DESIGN: We constructed a mesothelin promoter-based CRAd with a chimeric Ad5/3 fiber (AdMSLNCRAd5/3) that contains an Ad5 tail, Ad5 shaft, and an Ad3 knob. Previously, a chimeric Ad5/3 fiber has shown improved infectivity in many ovarian cancer cells. Viral replication and oncolysis were assessed in a panel of ovarian cancer cell lines. To test the oncolytic efficacy of AdMSLNCRAd5/3 in a murine model, bioluminescence imaging of tumor luciferase activity and survival analysis were done. RESULTS: AdMSLNCRAd5/3 achieved up to a 10,000-fold higher cell killing effect and up to 120-fold higher levels of viral replication in all human ovarian cancer cells, compared with wild-type Ad5. AdMSLNCRAd5/3 significantly inhibited tumor growth as confirmed by in vivo imaging (P < 0.05). Survival with AdMSLNCRAd5/3 was significantly enhanced when compared with no virus or with a wild-type Ad5-treated group (P < 0.05). CONCLUSIONS: The robust replication, oncolysis, and in vivo therapeutic efficacy of AdMSLNCRAd5/3 showed that this CRAd is a promising candidate for treating ovarian cancer. Importantly, we have applied in vivo imaging that has allowed repeated and longitudinal measurements of tumor growth after CRAd treatment.

An adenoviral platform for selective self-assembly and targeted delivery of nanoparticles.

Metallic nanoparticles (NPs) can be used for the diagnosis, imaging, and therapy of tumors and cardiovascular disease. However, targeted delivery of NPs to specific cells remains a major limitation for clinical realization of these potential treatment options. Herein, a novel strategy for the specific coupling of NPs to a targeted adenoviral (Ad) platform to deliver NPs to specific cells is defined. Genetic manipulation of the gene-therapy vector is combined with a specific chemical coupling strategy. In particular, a high-affinity interaction between a sequence of six-histidine amino acid residues genetically incorporated into Ad capsid proteins and nickel(II) nitrilotriacetic acid on the surface of gold NPs is employed. The selective self-assembly of gold NPs and Ad vectors into multifunctional platforms does not negatively affect the targeting of Ad to specific cells. This opens the possibility of using Ad vectors for targeted NP delivery, thereby providing a new type of combinatorial approach for the treatment of diseases that involves both nanotechnology and gene therapy.

Adenovirus tumor targeting and hepatic untargeting by a coxsackie/adenovirus receptor ectodomain anti-carcinoembryonic antigen bispecific adapter.

Adenovirus vectors have a number of advantages for gene therapy. However, because of their lack of tumor tropism and their preference for liver infection following systemic administration, they cannot be used for systemic attack on metastatic disease. Many epithelial tumors (e.g., colon, lung, and breast) express carcinoembryonic antigen (CEA). To block the natural hepatic tropism of adenovirus and to "retarget" the virus to CEA-expressing tumors, we used a bispecific adapter protein (sCAR-MFE), which fuses the ectodomain of the coxsackie/adenovirus receptor (sCAR) with a single-chain anti-CEA antibody (MFE-23). sCAR-MFE untargets adenovirus-directed luciferase transgene expression in the liver by >90% following systemic vector administration. Moreover, sCAR-MFE can "retarget" adenovirus to CEA-positive epithelial tumor cells in cell culture, in s.c. tumor grafts, and in hepatic tumor grafts. The sCAR-MFE bispecific adapter should, therefore, be a powerful agent to retarget adenovirus vectors to epithelial tumor metastases.

A mosaic fiber adenovirus serotype 5 vector containing reovirus sigma 1 and adenovirus serotype 3 knob fibers increases transduction in an ovarian cancer ex vivo system via a coxsackie and adenovirus receptor-independent pathway.

PURPOSE: Adenovirus serotype 5 (Ad5) has been used for gene therapy with limited success due to insufficient infectivity in cells with low expression of the primary receptor, the coxsackie and adenovirus receptor (CAR). Evidence that adenovirus serotype receptors other than CAR may be of use was presented in previous studies that showed that the Ad3 receptor is expressed at high levels in ovarian cancer cells. We hypothesized that combined use of unique chimeric fibers in the context of novel mosaic adenovirus vectors would enhance infectivity via non-CAR pathways in ovarian cancer cells. EXPERIMENTAL DESIGN: We constructed and characterized Ad5 vectors that use Ad3 knob and reovirus fibers to generate a mosaic fiber virion. Serotype 3 Dearing reovirus uses a fiber-like sigma 1 protein to infect cells expressing sialic acid and junction adhesion molecule 1. We therefore constructed a mosaic fiber Ad5 vector, designated Ad5/3-sigma 1, encoding two fibers: a sigma 1 chimeric fiber and the chimeric Ad5/3 fiber composed of an Ad3 knob. RESULTS: Functionally, Ad5/3-sigma 1 used sialic acid, junction adhesion molecule 1, and Ad3 receptor for cell transduction and achieved maximum infectivity enhancement in ovarian cancer cells with low CAR expression. Furthermore, Ad5/3-sigma 1 achieved infectivity enhancement in primary tissue slices of human ovarian tumor. CONCLUSIONS: We have developed a new type of Ad5 vector with the novel tropism, possessing fibers from Ad3 and reovirus, which exhibits enhanced infectivity via CAR-independent pathway(s). In addition, the flexible genetic platform of vector allows different combination of fiber variants that can be incorporated within the same particle.

Mesenchymal progenitor cells as cellular vehicles for delivery of oncolytic adenoviruses.

Natural and genetically modified oncolytic viruses have been systematically tested as anticancer therapeutics. Among this group, conditionally replicative adenoviruses have been developed for a broad range of tumors with a rapid transition to clinical settings. Unfortunately, clinical trials have shown limited antitumor efficacy partly due to insufficient viral delivery to tumor sites. We investigated the possibility of using mesenchymal progenitor cells (MPC) as virus carriers based on the documented tumor-homing abilities of this cell population. We confirmed preferential tumor homing of MPCs in an animal model of ovarian carcinoma and evaluated the capacity of MPCs to be loaded with oncolytic adenoviruses. We showed that MPCs were efficiently infected with an adenovirus genetically modified for coxsackie and adenovirus receptor-independent infection (Ad5/3), which replicated in the cell carriers. MPCs loaded with Ad5/3 caused total cell killing when cocultured with a cancer cell line. In an animal model of ovarian cancer, MPC-based delivery of the Ad5/3 increased the survival of tumor-bearing mice compared with direct viral injection. Further, tumor imaging confirmed a decrease in tumor burden in animals treated with oncolytic virus delivered by MPC carriers compared with the direct injection of the adenovirus. These data show that MPCs can serve as intermediate carriers for replicative adenoviruses and suggest that the natural homing properties of specific cell types can be used for targeted delivery of these virions.

Reovirus sigma1 fiber incorporated into adenovirus serotype 5 enhances infectivity via a CAR-independent pathway.

Adenovirus serotype 5 (Ad5) has been used for gene therapy with limited success because of insufficient infectivity in cells with low expression of the primary receptor, the coxsackie and adenovirus receptor (CAR). To enhance infectivity in tissues with low CAR expression, tropism expansion is required via non-CAR pathways. Serotype 3 Dearing reovirus utilizes a fiber-like sigma1 protein to infect cells expressing sialic acid and junction adhesion molecule 1 (JAM1). We hypothesized that replacement of the Ad5 fiber with sigma1 would result in an Ad5 vector with CAR-independent tropism. We therefore constructed a fiber mosaic Ad5 vector, designated as Ad5-sigma1, encoding two fibers: the sigma1 and the wild-type Ad5 fiber. Functionally, Ad5-sigma1 utilized CAR, sialic acid, and JAM1 for cell transduction and achieved maximum infectivity enhancement in cells with or without CAR. Thus, we have developed a new type of Ad5 vector with expanded tropism, possessing fibers from Ad5 and reovirus, that exhibits enhanced infectivity via CAR-independent pathway(s).

Cellular vehicles for cancer gene therapy: current status and future potential.

Cancer is a difficult target for any therapeutic strategy; therefore, there is a continuous search for new therapeutic modalities, for application either alone or in combination. In this regard, gene-based therapy is a new approach that offers hope of improved control of tumors. Intensive research to apply gene therapy for cancer treatment has led to identification of the most important technical and theoretical barriers that need to be overcome for clinical success. One of the central unresolved challenges remains the issue of specific and efficient delivery of genes to target cells or tissues, emphasizing the importance of the gene carrier. Along with different viral and non-viral vector systems, mammalian cells have also been considered as vehicles for delivery of anti-cancer therapeutics. The cell-based delivery approach was introduced as the first attempt to apply gene therapy to cancer treatment, and in general, has followed most of the ups and downs of gene therapy applications, progressing alongside new knowledge gained in this field. As a result, significant progress has been made in some aspects of the cell-based approach, while the development of other essential issues is only just gaining speed. It appears that the initial phase of development of cell-based protocols - the achievement of efficient ex vivo cell loading with therapeutics - has largely been fulfilled. However, the desired efficacy of cell-based strategies in general has not yet been reached, and specificity of tumor homing needs to be improved considerably. There is hope that advances in related scientific fields will promote the utilization of cells as powerful and versatile vehicles for cancer gene therapy.

Fiber-mosaic adenovirus as a novel approach to design genetically modified adenoviral vectors.

Genetic modification of the adenovirus (Ad) capsid is one of the successful strategies to achieve viral retargeting. However, it has been widely recognized that structural constraints imposed by viral proteins limit the number and nature of incorporated targeting ligands and often hamper viral propagation. To address this issue, we propose a genetic fiber-mosaic virus (having two distinct fibers in one viral particle) as a means to facilitate fiber modifications. Fiber-mosaic virus having tandem fibers: a wild type (wt) fiber and second adjunctive fiber, will utilize natural viral entry for the conventional propagation of the vectors whereas, adjunctive fiber will serve multiple potential purposes such as targeting, purification, or imaging of viral particles via genetic incorporation of the corresponding functional moieties. We generated the mosaic adenovirus vector encoding two fibers: wild-type and adjunctive fiber--Fiber-Fibritin (FF) and confirmed incorporation of FF in the mosaic viral particles. We investigated binding specificity of the mosaic virus and the possible interference of the two fibers during virus life cycle. Fiber-mosaic Ad attained new binding properties provided by the second fiber, while preserving the binding ability attributed to the wt fiber. Our results suggest that the two fibers being presented and structurally separated on the viral particle may also function separately as binding counterparts for virus attachment. Therefore, the mosaic setting will allow more flexibility in Ad retargeting approaches.