Application of mesenchymal stem cells as a vehicle to deliver replication-competent adenovirus for treating malignant glioma

Mesenchymal stem cells as therapeutic vehicles for glioma

Glioma is a disease with a poor prognosis despite the availability of multimodality treatments, and the development of novel therapies is urgently needed. Challenges in glioma treatment include the difficulty for drugs to cross the blood-brain barrier when administered systemically and poor drug diffusion when administered locally. Mesenchymal stem cells exhibit advantages for glioma therapy because of their ability to pass through the blood-brain barrier and migrate to tumor cells and their tolerance to the immune system. Therefore, mesenchymal stem cells have been explored as vehicles for various therapeutic agents for glioma treatment. Mesenchymal stem cells loaded with chemotherapeutic drugs show improved penetration and tumor accumulation. For gene therapy, mesenchymal stem cells can be used as vehicles for suicide genes, the so-called gene-directed enzyme prodrug therapy. Mesenchymal stem cell-based oncolytic viral therapies have been attempted in recent years to enhance the efficacy of infection against the tumor, viral replication, and distribution of viral particles. Many uncertainties remain regarding the function and behavior of mesenchymal stem cells in gliomas. However, strategies to increase mesenchymal stem cell migration to gliomas may improve the delivery of therapeutic agents and enhance their anti-tumor effects, representing promising potential for patient treatment.

Investigating the potential of oncolytic viruses for cancer treatment via MSC delivery

Mesenchymal stem cells (MSCs) have attracted considerable interest as a promising approach for cancer treatment due to their ability to undergo tumor-trophic migration. MSCs possess the unique ability to selectively migrate to tumors, making them an excellent candidate for targeted delivery of oncolytic viruses (OVs) to treat isolated tumors and metastatic malignancies. OVs have attracted attention as a potential treatment for cancer due to their ability to selectively infect and destroy tumor cells while sparing normal cells. In addition, OVs can induce immunogenic cell death and contain curative transgenes in their genome, making them an attractive candidate for cancer treatment in combination with immunotherapies. In combination with MSCs, OVs can modulate the tumor microenvironment and trigger anti-tumor immune responses, making MSC-releasing OVs a promising approach for cancer treatment. This study reviews researches on the use of MSC-released OVs as a novel method for treating cancer. Video Abstract.

Mesenchymal stem cell-released oncolytic virus: an innovative strategy for cancer treatment

Oncolytic viruses (OVs) infect, multiply, and finally remove tumor cells selectively, causing no damage to normal cells in the process. Because of their specific features, such as, the ability to induce immunogenic cell death and to contain curative transgenes in their genomes, OVs have attracted attention as candidates to be utilized in cooperation with immunotherapies for cancer treatment. This treatment takes advantage of most tumor cells' inherent tendency to be infected by certain OVs and both innate and adaptive immune responses are elicited by OV infection and oncolysis. OVs can also modulate tumor microenvironment and boost anti-tumor immune responses. Mesenchymal stem cells (MSC) are gathering interest as promising anti-cancer treatments with the ability to address a wide range of cancers. MSCs exhibit tumor-trophic migration characteristics, allowing them to be used as delivery vehicles for successful, targeted treatment of isolated tumors and metastatic malignancies. Preclinical and clinical research were reviewed in this study to discuss using MSC-released OVs as a novel method for the treatment of cancer. Video Abstract.

Modifying oncolytic virotherapy to overcome the barrier of the hypoxic tumor microenvironment. Where do we stand?

Viruses are completely dependent on host cell machinery for their reproduction. As a result, factors that influence the state of cells, such as signaling pathways and gene expression, could determine the outcome of viral pathogenicity. One of the important factors influencing cells or the outcome of viral infection is the level of oxygen. Recently, oncolytic virotherapy has attracted attention as a promising approach to improving cancer treatment. However, it was shown that tumor cells are mostly less oxygenated compared with their normal counterparts, which might affect the outcome of oncolytic virotherapy. Therefore, knowing how oncolytic viruses could cope with stressful environments, particularly hypoxic environments, might be essential for improving oncolytic virotherapy.

Mesenchymal stem cell carriers enhance anti-tumor efficacy of oncolytic virotherapy

Oncolytic viruses (OVs) specifically infect, replicate and eventually destroy tumor cells, with no concomitant toxicity to adjacent normal cells. Furthermore, OVs can regulate tumor microenvironments and stimulate anti-tumor immune responses. Mesenchymal stem cells (MSCs) have inherent tumor tropisms and immunosuppressive functions. MSCs carrying OVs not only protect viruses from clearing by the immune system, but they also deliver the virus to tumor lesions. Equally, cytokines released by MSCs enhance anti-tumor immune responses, suggesting that MSCs carrying OVs may be considered as a promising strategy in enhancing the anti-tumor efficacies of virotherapy. In the present review, preclinical and clinical studies were evaluated and discussed, as well as the effectiveness of MSCs carrying OVs for tumor treatment.

Mesenchymal Stromal Stem Cell-Derived Microvesicles Enhance Tumor Lysate Pulsed Dendritic Cell Stimulated Autologous T lymphocyte Cytotoxicity

Background

Immunotherapy is one promising therapeutic strategy against glioma, an aggressive form of brain cancer. Previous studies have demonstrated that multiple tumor antigens exist and can be used to induce tumor specific T cell responses. Furthermore, recently it was shown that TLR4-primed mesenchymal stem cells (MSCs), also known as MSC1, mostly elaborate pro-inflammatory mediators. Compared to MSCs, MSC-derived microvesicles (MVs) have advantageous properties that present them as stable, long lasting effectors with no risk of immune rejection. Therefore, peripheral blood monocyte derived dendritic cells (MoDCs) have been used to load tumor antigens and stimulate T cell mediated responses in the presence of MSC1-derived MVs in vitro.

Methods

The B92 tumor cell line was heated to 43^°C for 90 min prior to preparation of tumor cell lysates. MVs were purified by differential ultracentrifugation after isolation, stimulation of proliferation and treatment of MSCs. Autologous T cells isolated from non-adherent cells were harvested during the procedure to generate MoDCs and then incubated with heat stressed tumor cell lysate pulsed DCs in the presence of MSC1-derived MVs. T cells were then co-cultured with tumor cells in 96-well plates at a final volume of 200 μl CM at an effector: target ratio of 100:1 to determine their specific cytotoxic activity.

Results

Flow cytometric analysis, T cell mediated cytotoxicity showed that heat stressed tumor antigen pulsed MoDCs and MSC1-derived MVs primed T cells elicited non-significantly enhanced cytotoxic activity toward B92 tumor cells (P≥0.05).

Conclusion

These findings may offer new insights into tumor antigen presenting technology involving dendritic cells and MSC1-derived MVs. Further exploration of the potential of such nanoscale particles in immunotherapy and in novel cancer vaccine settings appears warranted.

Selective effects of a fiber chimeric conditionally replicative adenovirus armed with hep27 gene on renal cancer cell

ASBTARCT Adenoviruses mediated cancer gene therapies are widely investigated and show a promising effect on cancer treatment. However, efficient gene transfer varies among different cancer cell lines based on the expression of coxsakie adenovirus receptor (CAR). Hep27, a member of dehydrogenase/reductase (SDR) family, can bind to Mdm2, resulting in the attenuation of Mdm2-mediated p53 degradation. Here we constructed a fiber chimeric adenovirus carrying hep27 gene (F5/35-ZD55-Hep27), in which the fiber protein of 5-serotype adenovirus (Ad5) was substituted by that of 35-serotype adenovirus (Ad35), aiming to facilitate the infection for renal cancer cells and develop the role of hep27 in cancer therapy. We evaluated the CAR and CD46 (a membrane cofactor protein for Ad35) expression in four kinds of renal cancer cells and assessed the relationship between receptors and infection efficiency. 5/35 fiber-modified adenovirus had a much promising infectivity compared with Ad5-based vector in renal cancer cells. F5/35-ZD55-Hep27 had enhanced antitumor activity against human renal cancer cells compared to the other groups. Further, hep27 mediated p53 and cleaved-PARP upregulation and mdm2 downregulation was involved and caused increased apoptosis. Moreover, F5/35-ZD55-Hep27 significantly suppressed tumor growth in subcutaneous renal cancer cell xenograft models. Our data demonstrated that 5/35 fiber-modified adenovirus F5/35-ZD55-Hep27 transferred into renal cancers efficiently and increased p53 to induce cancer cell apoptosis. Thus 5/35 fiber-modified adenoviral vector F5/35-ZD55-Hep27 might a promising vector and antitumor reagent for renal cancer gene therapy.

Two mature products of MIR-491 coordinate to suppress key cancer hallmarks in glioblastoma

MIR-491 is commonly co-deleted with its adjacent CDKN2A on chromosome 9p21.3 in glioblastoma multiforme (GBM). However, it is not known whether deletion of MIR-491 is only a passenger event or has an important role. Small-RNA sequencing of samples from GBM patients demonstrated that both mature products of MIR-491 (miR-491-5p and -3p) are downregulated in tumors compared with the normal brain. The integration of GBM data from The Cancer Genome Atlas (TCGA), miRNA target prediction and reporter assays showed that miR-491-5p directly targets EGFR, CDK6 and Bcl-xL, whereas miR-491-3p targets IGFBP2 and CDK6. Functionally, miR-491-3p inhibited glioma cell invasion; overexpression of both miR-491-5p and -3p inhibited proliferation of glioma cell lines and impaired the propagation of glioma stem cells (GSCs), thereby prolonging survival of xenograft mice. Moreover, knockdown of miR-491-5p in primary Ink4a-Arf-null mouse glial progenitor cells exacerbated cell proliferation and invasion. Therefore, MIR-491 is a tumor suppressor gene that, by utilizing both mature forms, coordinately controls the key cancer hallmarks: proliferation, invasion and stem cell propagation.

Immune Suppression during Oncolytic Virotherapy for High-Grade Glioma; Yes or No?

Oncolytic viruses have been seriously considered for glioma therapy over the last 20 years. The oncolytic activity of several oncolytic strains has been demonstrated against human glioma cell lines and in in vivo xenotransplant models. So far, four of these stains have additionally completed the first phase I/II trials in relapsed glioma patients. Though safety and feasibility have been demonstrated, therapeutic efficacy in these initial trials, when described, was only minor. The role of the immune system in oncolytic virotherapy for glioma remained much less studied until recent years. When investigated, the immune system, adept at controlling viral infections, is often hypothesized to be a strong hurdle to successful oncolytic virotherapy. Several preclinical studies have therefore aimed to improve oncolytic virotherapy efficacy by combining it with immune suppression or evasion strategies. More recently however, a new paradigm has developed in the oncolytic virotherapy field stating that oncolytic virus-mediated tumor cell death can be accompanied by elicitation of potent activation of innate and adaptive anti-tumor immunity that greatly improves the efficacy of certain oncolytic strains. Therefore, it seems the three-way interaction between oncolytic virus, tumor and immune system is critical to the outcome of antitumor therapy. In this review we discuss the studies which have investigated how the immune system and oncolytic viruses interact in models of glioma. The novel insights generated here hold important implications for future research and should be incorporated into the design of novel clinical trials.

Oncolytic adenoviruses: A thorny path to glioma cure

Glioblastoma Multiforme (GBM) is a rapidly progressing brain tumor. Despite the relatively low percentage of cancer patients with glioma diagnoses, recent statistics indicate that the number of glioma patients may have increased over the past decade. Current therapeutic options for glioma patients include tumor resection, chemotherapy, and concomitant radiation therapy with an average survival of approximately 16 months. The rapid progression of gliomas has spurred the development of novel treatment options, such as cancer gene therapy and oncolytic virotherapy. Preclinical testing of oncolytic adenoviruses using glioma models revealed both positive and negative sides of the virotherapy approach. Here we present a detailed overview of the glioma virotherapy field and discuss auxiliary therapeutic strategies with the potential for augmenting clinical efficacy of GBM virotherapy treatment.

Use of genetically modified mesenchymal stem cells to treat neurodegenerative diseases

The transplantation of mesenchymal stem cells (MSCs) for treating neurodegenerative disorders has received growing attention recently because these cells are readily available, easily expanded in culture, and when transplanted, survive for relatively long periods of time. Given that such transplants have been shown to be safe in a variety of applications, in addition to recent findings that MSCs have useful immunomodulatory and chemotactic properties, the use of these cells as vehicles for delivering or producing beneficial proteins for therapeutic purposes has been the focus of several labs. In our lab, the use of genetic modified MSCs to release neurotrophic factors for the treatment of neurodegenerative diseases is of particular interest. Specifically, glial cell-derived neurotrophic factor (GDNF), nerve growth factor (NGF), and brain derived neurotrophic factor (BDNF) have been recognized as therapeutic trophic factors for Parkinson's, Alzheimer's and Huntington's diseases, respectively. The aim of this literature review is to provide insights into: (1) the inherent properties of MSCs as a platform for neurotrophic factor delivery; (2) the molecular tools available for genetic manipulation of MSCs; (3) the rationale for utilizing various neurotrophic factors for particular neurodegenerative diseases; and (4) the clinical challenges of utilizing genetically modified MSCs.

Monitoring adenoviral based gene delivery in rat glioma by molecular imaging

AIM: To determine whether endothelial progenitor cells (EPCs) can be used as delivery vehicle for adenoviral vectors and imaging probes for gene therapy in glioblastoma.

METHODS: To use cord blood derived EPCs as delivery vehicle for adenoviral vectors and imaging probes for glioma gene therapy, a rat model of human glioma was made by implanting U251 cells orthotopically. EPCs were transfected with an adenovirus (AD5/carrying hNIS gene) and labeled with iron oxide and inoculated them directly into the tumor 14 d following implantation of U251 cells. Magnetic resonance imaging (MRI) was used to in vivo track the migration of EPCs in the tumor. The expression of gene products was determined by in vivo Tc-99m single photon emission computed tomography (SPECT). The findings were validated with immunohistochemistry (IHC).

RESULTS: EPCs were successfully transfected with the adenoviral vectors carrying hNIS which was proved by significantly (P < 0.05) higher uptake of Tc-99m in transfected cells. Viability of EPCs following transfection and iron labeling was not altered. In vivo imaging showed the presence of iron positive cells and the expression of transgene (hNIS) product on MRI and SPECT, respectively, all over the tumors following administration of transfected and iron labeled EPCs in the tumors. IHC confirmed the distribution of EPC around the tumor away from the injection site and also showed transgene expression in the tumor. The results indicated the EPCs’ ability to deliver adenoviral vectors into the glioma upon intratumor injection.

CONCLUSION: EPCs can be used as vehicle to deliver adenoviral vector to glioma and also act as imaging probe at the same time.

Susceptibility of human placenta derived mesenchymal stromal/stem cells to human herpesviruses infection

Fetal membranes (FM) derived mesenchymal stromal/stem cells (MSCs) are higher in number, expansion and differentiation abilities compared with those obtained from adult tissues, including bone marrow. Upon systemic administration, ex vivo expanded FM-MSCs preferentially home to damaged tissues promoting regenerative processes through their unique biological properties. These characteristics together with their immune-privileged nature and immune suppressive activity, a low infection rate and young age of placenta compared to other sources of SCs make FM-MSCs an attractive target for cell-based therapy and a valuable tool in regenerative medicine, currently being evaluated in clinical trials. In the present study we investigated the permissivity of FM-MSCs to all members of the human Herpesviridae family, an issue which is relevant to their purification, propagation, conservation and therapeutic use, as well as to their potential role in the vertical transmission of viral agents to the fetus and to their potential viral vector-mediated genetic modification. We present here evidence that FM-MSCs are fully permissive to infection with Herpes simplex virus 1 and 2 (HSV-1 and HSV-2), Varicella zoster virus (VZV), and Human Cytomegalovirus (HCMV), but not with Epstein-Barr virus (EBV), Human Herpesvirus-6, 7 and 8 (HHV-6, 7, 8) although these viruses are capable of entering FM-MSCs and transient, limited viral gene expression occurs. Our findings therefore strongly suggest that FM-MSCs should be screened for the presence of herpesviruses before xenotransplantation. In addition, they suggest that herpesviruses may be indicated as viral vectors for gene expression in MSCs both in gene therapy applications and in the selective induction of differentiation.