Cell-based Carriers Research Articles

Stem cell technology and engineering for cancer treatment

Stem cells are not only widely used for regenerative medicine, but are also considered as a useful tool for cancer treatment. For a long time, stem cells have been utilized to renew the immune system for radiation or chemotherapy treated patients. Recently, stem cells are being engineered to carry therapeutic reagents to target tumor sites. Cancer vaccines based on the knowledge of cancer stem cells have been studied and applied for cancer treatment. Induced pluripotent stem cells have been used to create active T cells to support cancer immunotherapy. Those are due to the unique characteristics of stem cells, such as immunological tolerance, migration, and tissue reparation. This review discusses stem cell applications in transplantation, stem cell-based carriers, induced-pluripotent stem cells, cancer stem cells, and potential of stem cells engineering to revolutionize cancer treatment.

Immune cells: more than simple carriers for systemic delivery of oncolytic viruses.

Oncolytic virotherapy on its own has numerous drawbacks, including an inability of the virus to actively target tumor cells and systemic toxicities at the high doses necessary to effectively treat tumors. Addition of immune cell-based carriers of oncolytic viruses holds promise as a technique in which oncolytic virus can be delivered directly to tumors in smaller and less toxic doses. Interestingly, the cell carriers themselves have also demonstrated antitumor effects, which can be augmented further by tailoring the appropriate oncolytic virus to the appropriate cell type. This review discusses the multiple factors that go into devising an effective, cell-based delivery system for oncolytic viruses.

Crosstalk Between Immune Cell and Oncolytic Vaccinia Therapy Enhances Tumor Trafficking and Antitumor Effects

The combination of an oncolytic virus, that directly destroys tumor cells and mediates an acute immune response, with an immune cell therapy, capable of further enlisting and enhancing the host immune response, has the potential to create a potent therapeutic effect. We have previously developed several strategies for optimizing the delivery of oncolytic vaccinia virus vectors to their tumor targets, including the use of immune cell-based carrier vehicles and the incorporation of mutations that increase production of the enveloped form of vaccinia (extracellular enveloped viral (EEV)) that is better adapted to spread within a host. Here, we initially combine these approaches to create a novel therapeutic, consisting of an immune cell (cytokine-induced killer, CIK) preloaded with an oncolytic virus that is EEV enhanced. This resulted in direct interaction between the viral and immune cell components with each assisting the other in directing the therapy to the tumor and so enhancing the antitumor effects. This effect could be further improved through CCL5 expression from the virus. The resulting multicomponent therapy displays the ability for synergistic crosstalk between components, so significantly enhancing tumor trafficking and antitumor effects.

Radiovirotherapy: Principles and Prospects in Oncology

Radiovirotherapy is defined as the use of viruses to deliver radioisotopic treatment into infected cells. Oncolytic viruses are able to selectively target and kill cancer cells. The combination of oncolytic viruses and radiation therapies can have synergistic antitumour properties. Viruses may act as radiosensitizers, and radiations can increase viral oncolytic properties. The combination of oncolytic viruses with a virally-directed radioisotope therapy is an innovative method to combine viruses and radiation therapy, selectively within the tumour cells. The sodium/iodide symporter (NIS) is the main transgene that has been studied for this approach. NIS can mediate the uptake of isotopes of iodine and technetium 99m for in vivo gene expression imaging and therapy. This review highlights the principles of radiovirotherapy, and its recent progress. Better understanding of the regulation of NIS opens up pathways by which to potentiate the functional expression of NIS. In terms of the therapeutic isotope, Iodine-131 has been most frequently studied but other isotopes (astatine- 211, rhenium-188) are of growing interest. Oncolytic viruses are able to infect selectively and replicate in cancer cells and promising early phase clinical trials have been recently published. Their development allows a better selectivity of viral infection and adds a virus-specific cytotoxicity to the therapeutic approach. Active research into strategies such as immunosuppressive treatment and cell-based carrier systems is seeking to circumvent the host antiviral immune response and, thus, increase the potential for systemic delivery. Finally, other anticancer therapies such as chemotherapy and external beam radiotherapy may have a synergistic effect with radiovirotherapy and such combinatorial approaches offering the prospect of accelerated translation into clinical studies.

Vitamin D3-Inducible Mesenchymal Stem Cell-Based Delivery of Conditionally Replicating Adenoviruses Effectively Targets Renal Cell Carcinoma and Inhibits Tumor Growth

Cell-based carriers were recently exploited as a tumor-targeting tool to improve systemic delivery of oncolytic viruses for cancer therapy. However, the slow clearance of carrier cells from normal organs indicates the need for a controllable system which allows viral delivery only when the carrier cells reach the tumor site. In this study, we sought to develop a pharmaceutically inducible cell-based oncolytic adenovirus delivery strategy for effective targeting and treatment of renal cell carcinoma (RCC), which is one of the most malignant tumor types with an unfavorable prognosis. Herein, we demonstrated the intrinsic tumor homing property of human bone marrow-derived mesenchymal stem cells (hMSCs) to specifically localize primary and metastatic RCC tumors after systemic administration in a clinically relevant orthotopic animal model. The platelet derived growth factor AA (PDGF-AA) secreted from RCC was identified as a chemoattractant responsible for the recruitment of hMSCs. Like endogenous osteocalcin whose barely detectable level of expression was dramatically induced by vitamin D(3), the silenced replication of human osteocalcin promoter-directed Ad-hOC-E1 oncolytic adenoviruses loaded in hMSCs was rapidly activated, and the released oncolytic adenoviruses sequentially killed cocultured RCC cells upon vitamin D(3) exposure. Moreover, the systemic treatment of RCC tumor-bearing mice with hMSC cell carriers loaded with Ad-hOC-E1 had very limited effects on tumor growth, but the loaded hMSCs combined with vitamin D(3) treatment induced effective viral delivery to RCC tumors and significant tumor regression. Therapeutic effects of hMSC-based Ad-hOC-E1 delivery were confirmed to be significantly greater than those of injection of carrier-free Ad-hOC-E1. Our results presented the first preclinical demonstration of a novel controllable cell-based gene delivery strategy that combines the advantages of tumor tropism and vitamin D(3)-regulatable human osteocalcin promoter-directed gene expression of hMSCs to improve oncolytic virotherapy for advanced RCC.

Abstract 5661: Pharmaceutically controlled replication of adenoviruses in mesenchymal stem cell-based cell carriers improves oncolytic virotherapy for advanced human renal cell carcinoma

Abstract Cell-based carriers were recently exploited as a tumor-targeting tool to improve systemic delivery of oncolytic viruses for cancer therapy. However, the slow clearance of carrier cells from normal organs indicates the need for a controllable system which allows viral delivery only when the carrier cells reach the tumor site. In this communication, we sought to develop a pharmaceutically-inducible cell-based oncolytic adenovirus delivery strategy for effective targeting and treatment of renal cell carcinoma (RCC), which is one of the most malignant tumor types with an unfavorable prognosis. Herein, we demonstrated the intrinsic tumor homing property of human bone marrow-derived mesenchymal stem cells (hMSCs) to specifically localize primary and metastatic RCC tumors after systemic administration in a clinically relevant orthotopic animal model. PDGF-AA secreted from RCC was identified as a chemoattractant responsible for the recruitment of hMSCs. Like endogenous osteocalcin whose barely detectable level of expression was dramatically induced by vitamin D3, the silenced replication of human osteocalcin promoter-directed Ad-hOC-E1 oncolytic adenoviruses loaded in hMSCs was rapidly activated and the released viral progenies sequentially killed co-cultured RCC cells upon vitamin D3 exposure. Moreover, systemic treatment of RCC tumor-bearing mice with Ad-hOC-E1-loaded hMSCs had very limited effect on tumor growth, but when it combined with vitamin D3 treatment induced effective viral delivery to RCC tumors and significant tumor regression. Therapeutic effects of hMSC-based Ad-hOC-E1 delivery were confirmed to be significantly greater than those of injection of carrier-free Ad-hOC-E1. Our results presented the first pre-clinical demonstration of a novel controllable cell-based gene delivery strategy that combines the advantages of tumor tropism and vitamin D3-regulatable human osteocalcin promoter-directed gene expression of hMSCs to improve oncolytic virotherapy for advanced RCC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5661. doi:1538-7445.AM2012-5661

Abstract 3487: Distant delivery of glioma-restricted oncolytic adenovirus loaded into a neural stem cell-based carrier prolongs the survival of animals with human glioblastoma

Abstract Despite recent advancements in the treatment of brain tumors, the prognosis for patients with malignant glioblastoma (GBM) still remains poor due to the invasive nature of these tumors. In this context, our lab and others have investigated the unique inherent tumor tropic properties of neural stem cells (NSCs) as a novel platform for the targeted delivery of oncolytic adenovirus for anti-glioma therapy. NSCs hold great promise for glioma therapy because of their inherent ability to target satellite tumor foci throughout the brain. In this study, we report that the infection/loading of NSCs with oncolytic adenovirus upregulate various chemoattractant receptors such as CXCR4 (10-fold, P=0.0054), VEGFR2 (5-fold, P=0.0143) and significantly enhances glioma specific migration of NSCs both in vitro and in vivo. In a human glioma xenograft animal model, virus loaded NSCs retain a majority of their tumor homing capacity with minimal effect on their viability, and are capable of delivering a therapeutic payload to tumor cells located far from the original implanted site. Moreover, NSC-based cell carriers significantly reduce the non-specific distribution of therapeutic virus in the animal brain. Finally, distance delivery of NSCs-loaded with CRAd-S-pk7, a glioma restricted oncolytic adenovirus, in multiple orthotropic xenograft models of human glioma have shown the ability to inhibit tumor growth and increase median survival by about 38 days (54%) as compared to the animal group treated with the CRAd-S-pk7 alone (P=0.0416). Our data suggest that NSC-based cell carriers have the potential to improve the therapeutic efficacy of anti-glioma virotherapy by not only protecting the therapeutic virus from the host immune system, but also by enhancing targeted delivery of therapeutic virus at disseminated tumor sites. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3487. doi:1538-7445.AM2012-3487

A Comparative Study of Neural and Mesenchymal Stem Cell-Based Carriers for Oncolytic Adenovirus in a Model of Malignant Glioma

Glioblastoma multiforme is a primary malignancy of the central nervous system that is universally fatal due to its disseminated nature. Recent investigations have focused on the unique tumor-tropic properties of stem cells as a novel platform for targeted delivery of anticancer agents to the brain. Neural stem cells (NSCs) and mesenchymal stem cells (MSCs) both have the potential to function as cell carriers for targeted delivery of a glioma restricted oncolytic virus to disseminated tumor due to their reported tumor tropism. In this study, we evaluated NSCs and MSCs as cellular delivery vehicles for an oncolytic adenovirus in the context of human glioma. We report the first preclinical comparison of the two cell lines and show that, while both stem cell lines are able to support therapeutic adenoviral replication intracellularly, the amount of virus released from NSCs was a log higher than the MSC (p < 0.001). Moreover, only virus loaded NSCs that were administered intracranially in an orthotopic glioma model significantly prolonged the survival of tumor bearing animals (median survival for NSCs 68.5 days vs 44 days for MSCs, p < 0.002). Loading oncolytic adenovirus into NSCs and MSCs also led to expression of both pro- and anti-inflammatory genes and decreased vector-mediated neuroinflammation. Our results indicate that, despite possessing a comparable migratory capacity, NSCs display superior therapeutic efficacy in the context of intracranial tumors. Taken together, these findings argue in favor of NSCs as an effective cell carrier for antiglioma oncolytic virotherapy.

Abstract 5397: Human mesenchymal stem cell-based cell carrier for tumor-homing delivery of replicating retrovirus vectors in glioblastoma models

Abstract In previous studies, we have demonstrated that replicating murine leukemia virus (RMLV)-based vectors can achieve highly efficient in vivo delivery of prodrug activating genes in glioblastoma models, with infection restricted to actively dividing tumor cells without spread to extratumoral sites, resulting in significantly prolonged survival upon prodrug administration; this approach is now being tested in a multi-center clinical trial. RMLV vectors can eventually spread to almost all actively dividing GBM cells over time. We are seeking to further improve the efficiency of this novel therapeutic strategy by engineering human mesenchymal stem cells (MSC) to function as RMLV vector producer cells (MSC-VPC). Primary MSC have been shown to actively migrate through tumor masses beyond the immediate injection site and track to diffusely infiltrating tumor foci. In the present study, we developed optimized methods for engineering MSC-VPC, and we then further examined tumor transduction efficiency of MSC-mediated RMLV delivery, and how this delivery method might affect vector replication kinetics in vivo. First, we evaluated the vector productivity of MSC-VPC in U87 human glioblastoma cells in vitro. Primary human MSCs were infected with RMLV vector AC3-GFP, expressing the GFP marker gene. These MSC were then re-plated at very low density onto a monolayer of naïve U87 glioma cells, and fluorescence was monitored over time. Under the fluorescent microscope, progressive spread of the RMLV vector released from the MSCs could be confirmed, as indicated by increasing GFP(+) U87 cells over time. Next, we tested MSC-VPC in intracranial U87 tumor models in vivo. Five days after intracranial tumor cell implantation, 1E3 transduction units (TU) of AC3-GFP vector or 5E3 MSC-VPC (∼20% pretransduced with AC3-GFP) were stereotactically injected at the tumor site. Tumors were harvested and digested on day 9 for FACS analysis to detect GFP expression. While the highest percentage of GFP(+) cells was 28.6% in the vector supernatant-treated group, up to 45% transduction efficiency was achieved in the MSC-VPC group. These results suggest the use of MSCs as tumor-homing carriers may be provide more efficient delivery of RMLV vectors in human glioma models. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5397. doi:10.1158/1538-7445.AM2011-5397

191. A Comparative Study of Stem Cell-Based Cell Carrier Systems for the Systemic Delivery of an Oncolytic Adenovirus for Antiglioma Therapy

191. A Comparative Study of Stem Cell-Based Cell Carrier Systems for the Systemic Delivery of an Oncolytic Adenovirus for Antiglioma Therapy

Unbiased selection of bone marrow derived cells as carriers for cancer gene therapy

There is currently great interest in development of cell-based carriers for delivery of viral vectors to metastatic tumors. To date, several cell carriers have been tested based largely upon their predicted tumor-localizing properties. However, cell types may exist which can be mobilized from the circulation by a tumor which have not yet been identified. Here we use an unbiased screen of bone marrow (BM) cells to identify cells which localize to tumors and which might serve as effective candidate cell carriers without any prior prediction or selection. Unsorted BM cells from green fluorescent protein (GFP)-transgenic donor mice were adoptively transferred into C57Bl/6 mice bearing pre-established subcutaneous B16 melanoma tumors. Forty-eight hours and eight days later, tumors, organs and blood were analyzed for GFP-expressing cells by flow cytometry. The phenotype of GFP cells in organs was determined by co-staining with specific cell surface markers. CD45(+) hematopoietic cells were readily detected in tumor, spleen, bone marrow, blood and lung at both time points. Within these CD45(+) cell populations, preferential accumulation in the tumor was observed of cells expressing Sca-1, c-kit, NK1.1, Thy1.2, CD14, Mac-3 and/or CD11c. Lymphodepletion increased homing to spleen and bone marrow, but not to tumors. We have used an in vivo screen to identify populations of BM-derived donor cells which accumulate within tumors. These studies will direct rational selection of specific cell types which can be tested in standardized assays of cell carrier efficiency for the treatment of metastatic tumors.

Carrier cell‐mediated delivery of oncolytic parvoviruses for targeting metastases

Over the last few years, naturally occurring or genetically manipulated oncolytic viruses gained increasing attention as novel therapeutics for cancer treatment. The present work provides proof of principle that an organotropic cell-based carrier system is suitable to deliver oncolytic parvoviruses to a tissue known to be a target for the formation of metastases. Carrier cells were inactivated by gamma-irradiation after infection, which was found not to affect the production and release of parvoviruses that were capable of lysing cocultured target neoplastic cells. Although systemically administered parvovirus H-1 showed a pronounced therapeutic effect against the development of established Morris hepatoma (MH3924A) lung metastases, the carrier cell strategy offered a number of advantages. Infected carriers were able to sustain H-1 virus expression for 6 days in the lungs of rats affected by metastatic disease and to reduce the spreading of the virus to peripheral organs. Compared to direct virus injection, the carrier cell protocol led to an improved therapeutic effect (metastases suppression) and a lesser generation of virus-neutralizing antibodies. These data support the use of carrier cells to deliver oncolytic viruses and/or viral vectors locally in tumors and, more particularly, metastases.