Therapeutic targeting of subdural medulloblastomas using human neural stem cells expressing carboxylesterase

Anti-Cancer Effect of Neural Stem Cells Transfected with Carboxylesterase and sTRAIL Genes in Animals with Brain Lesions of Lung Cancer

A metastatic brain tumor is the most common type of malignancy in the central nervous system, which is one of the leading causes of death in patients with lung cancer. The purpose of this study is to evaluate the efficacy of a novel treatment for metastatic brain tumors with lung cancer using neural stem cells (NSCs), which encode rabbit carboxylesterase (rCE) and the secretion form of tumor necrosis factor-related apoptosis-inducing ligand (sTRAIL). rCE and/or sTRAIL were transduced in immortalized human fetal NSCs, HB1.F3. The cytotoxic effects of the therapeutic cells on human lung cancer cells were evaluated in vitro with the ligands and decoy receptor expression for sTRAIL in the presence of CPT-11. Human NSCs encoding rCE (F3.CE and F3.CE.sTRAIL) significantly inhibited the growth of lung cancer cells in the presence of CPT-11 in vitro. Lung cancer cells were inoculated in immune-deficient mice, and therapeutic cells were transplanted systematically through intracardiac arterial injection and then treated with CPT-11. In resting state, DR4 expression in lung cancer cells and DcR1 in NSCs increased to 70% and 90% after CPT-11 addition, respectively. The volumes of the tumors in immune-deficient mice were reduced significantly in mice with F3.CE.sTRAIL transplantation and CPT-11 treatment. The survival was also significantly prolonged with treatment with F3.sTRAIL and F3.CE plus CPT-11 as well as F3.CE.sTRAIL plus CPT-11. NSCs transduced with rCE and sTRAIL genes showed a significant anti-cancer effect on brain metastatic lung cancer in vivo and in vitro, and the effect may be synergistic when rCE/CPT-11 and sTRAIL are combined. This stem-cell-based study using two therapeutic genes of different biological effects can be translatable to clinical application.

Nanomedicines and cell-based therapies for embryonal tumors of the nervous system

Embryonal tumors of the nervous system are neoplasms predominantly affecting the pediatric population. Among the most common and aggressive ones are neuroblastoma (NB) and medulloblastoma (MB). NB is a sympathetic nervous system tumor, which is the most frequent extracranial solid pediatric cancer, usually detected in children under two. MB originates in the cerebellum and is one of the most lethal brain tumors in early childhood. Their tumorigenesis presents some similarities and both tumors often have treatment resistances and poor prognosis. High-risk (HR) patients require high dose chemotherapy cocktails associated with acute and long-term toxicities. Nanomedicine and cell therapy arise as potential solutions to improve the prognosis and quality of life of children suffering from these tumors. Indeed, nanomedicines have been demonstrated to efficiently reduce drug toxicity and improve drug efficacy. Moreover, these systems have been extensively studied in cancer research over the last few decades and an increasing number of anticancer nanocarriers for adult cancer treatment has reached the clinic. Among cell-based strategies, the clinically most advanced approach is chimeric-antigen receptor (CAR) T therapy for both pathologies, which is currently under investigation in phase I/II clinical trials. However, pediatric drug research is especially hampered due not only to ethical issues but also to the lack of efficient pre-clinical models and the inadequate design of clinical trials. This review provides an update on progress in the treatment of the main embryonal tumors of the nervous system using nanotechnology and cell-based therapies and discusses key issues behind the gap between preclinical studies and clinical trials in this specific area. Some directions to improve their translation into clinical practice and foster their development are also provided.

Development of next-generation tumor-homing induced neural stem cells to enhance treatment of metastatic cancers

Engineered tumor-homing neural stem cells (NSCs) have shown promise in treating cancer. Recently, we transdifferentiated skin fibroblasts into human-induced NSCs (hiNSC) as personalized NSC drug carriers. Here, using a SOX2 and spheroidal culture-based reprogramming strategy, we generated a new hiNSC variant, hiNeuroS, that was genetically distinct from fibroblasts and first-generation hiNSCs and had significantly enhanced tumor-homing and antitumor properties. In vitro, hiNeuroSs demonstrated superior migration to human triple-negative breast cancer (TNBC) cells and in vivo rapidly homed to TNBC tumor foci following intracerebroventricular (ICV) infusion. In TNBC parenchymal metastasis models, ICV infusion of hiNeuroSs secreting the proapoptotic agent TRAIL (hiNeuroS-TRAIL) significantly reduced tumor burden and extended median survival. In models of TNBC leptomeningeal carcinomatosis, ICV dosing of hiNeuroS-TRAIL therapy significantly delayed the onset of tumor formation and extended survival when administered as a prophylactic treatment, as well as reduced tumor volume while prolonging survival when delivered as established tumor therapy.

Neural Stem Cells

Neural stem cell (NSC) transplantation has provided the basis for the development of potentially powerful new therapeutic cell-based strategies for a broad spectrum of clinical diseases, including stroke, psychiatric illnesses such as fetal alcohol spectrum disorders, and cancer. Here, we discuss pertinent preclinical investigations involving NSCs, including how NSCs can ameliorate these diseases, the current barriers hindering NSC-based treatments, and future directions for NSC research. There are still many translational requirements to overcome before clinical therapeutic applications, such as establishing optimal dosing, route of delivery, and timing regimens and understanding the exact mechanism by which transplanted NSCs lead to enhanced recovery. Such critical lab-to-clinic investigations will be necessary in order to refine NSC-based therapies for debilitating human disorders.

Tumor-specific gene therapy for pancreatic cancer using human neural stem cells encoding carboxylesterase

Advanced pancreatic cancer is one of the most lethal malignant human diseases lacking effective treatment. Its extremely low survival rate necessitates development of novel therapeutic approach. Human neural stem cells (NSCs) are known to have tumor-tropic effect. We genetically engineered them to express rabbit carboxyl esterase (F3.CE), which activates prodrug CPT-11(irinotecan) into potent metabolite SN-38. We found significant inhibition of the growth of BxPC3 human pancreatic cancer cell line in vitro by F3.CE in presence of CPT-11. Apoptosis was also markedly increased in BxPC3 cells treated with F3.CE and CPT-11. The ligand VEGF and receptor VEGF-1(Flt1) were identified to be the relevant tumor-tropic chemoattractant. We confirmed in vivo that in mice injected with BxPC3 on their skin, there was significant reduction of tumor size in those treated with both F3.CE and BxPC3 adjacent to the cancer mass. Administration of F3.CE in conjunction with CPT-11 could be a new possibility as an effective treatment regimen for patients suffering from advanced pancreatic cancer.

In vivo bioluminescence imaging for leptomeningeal dissemination of medulloblastoma in mouse models

Background

The primary cause of treatment failure in medulloblastomas (MB) is the development of leptomeningeal dissemination (seeding). For translational research on MB seeding, one of the major challenges is the development of reliable experimental models that simulate the seeding and growth characteristics of MBs. To overcome this obstacle, we improved an experimental mouse model by intracisternal inoculation of human MB cells and monitoring with in vivo live images.

Methods

Human MB cells (UW426, D283 and MED8A) were transfected with a firefly luciferase gene and a Thy1.1 (CD90.1) marker linked with IRES under the control of the CMV promoter in a retroviral DNA backbone (effLuc). The MB-effLuc cells were injected into the cisterna magna using an intrathecal catheter, and bioluminescence images were captured. We performed histopathological analysis to confirm the extent of tumor seeding.

Results

The luciferase activity of MB-effLuc cells displayed a gradually increasing pattern, which correlated with a quantitative luminometric assay. Live imaging showed that the MB-effLuc cells were diffusely distributed in the cervical spinal cord and the lumbosacral area. All mice injected with UW426-effLuc, D283-effLuc and MED8A-effLuc died within 51 days. The median survival was 22, 41 and 12 days after injection of 1.2 × 10⁶ UW426-effLuc, D283-effLuc and MED8A-effLuc cells, respectively. The histopathological studies revealed that the MB-effLuc cells spread extensively and diffusely along the leptomeninges of the brain and spinal cord, forming tumor cell-coated layers. The tumor cells in the subarachnoid space expressed a human nuclei marker and Ki-67. Compared with the intracerebellar injection method in which the subfrontal area and distal spinal cord were spared by tumor cell seeding in some mice, the intracisternal injection model more closely resembled the widespread leptomeningeal seeding observed in MB patients.

Conclusion

The results and described method are valuable resources for further translational research to overcome MB seeding.

Human Neural Stem Cells Overexpressing a Carboxylesterase Inhibit Bladder Tumor Growth

Bladder cancer is a significant clinical and economic problem. Despite intravesical chemotherapy and immunotherapy, up to 80% of patients with non-muscle-invasive bladder cancer develop recurrent tumors, of which 20% to 30% evolve into more aggressive, potentially lethal tumors. Recently, bladder cancer cells are considered to be mediators of resistance to current therapies and therefore represent strong candidates as biologic targets. No effective chemotherapy has yet been developed for advanced bladder cancer. It is desirable that a drug can be delivered directly and specifically to bladder cancer cells. Stem cells have selective migration ability toward cancer cells, and therapeutic genes can be easily transduced into stem cells. In suicide gene therapy for cancer, stem cells carry a gene encoding a carboxylesterase (CE) enzyme that transforms an inert CPT-11 prodrug into a toxic SN-38 product, a topoisomerase 1 inhibitor. In immunodeficient mice, systemically transplanted HB1.F3.CE stem cells migrated toward the tumor implanted by the TCCSUP bladder cancer cell line, and, in combination with CPT-11, the volume of tumors was significantly reduced. These findings may contribute to the development of a new selective chemotherapeutic strategy against bladder cancer. Mol Cancer Ther; 15(6); 1201-7. ©2016 AACR.

Mesenchymal stem cells secretome as a modulator of the neurogenic niche: basic insights and therapeutic opportunities

Neural stem cells (NSCs) and mesenchymal stem cells (MSCs) share few characteristics apart from self-renewal and multipotency. In fact, the neurogenic and osteogenic stem cell niches derive from two distinct embryonary structures; while the later originates from the mesoderm, as all the connective tissues do, the first derives from the ectoderm. Therefore, it is highly unlikely that stem cells isolated from one niche could form terminally differentiated cells from the other. Additionally, these two niches are associated to tissues/systems (e.g., bone and central nervous system) that have markedly different needs and display diverse functions within the human body. Nevertheless they do share common features. For instance, the differentiation of both NSCs and MSCs is intimately associated with the bone morphogenetic protein family. Moreover, both NSCs and MSCs secrete a panel of common growth factors, such as nerve growth factor (NGF), glial derived neurotrophic factor (GDNF), and brain derived neurotrophic factor (BDNF), among others. But it is not the features they share but the interaction between them that seem most important, and worth exploring; namely, it has already been shown that there are mutually beneficially effects when these cell types are co-cultured in vitro. In fact the use of MSCs, and their secretome, become a strong candidate to be used as a therapeutic tool for CNS applications, namely by triggering the endogenous proliferation and differentiation of neural progenitors, among other mechanisms. Quite interestingly it was recently revealed that MSCs could be found in the human brain, in the vicinity of capillaries. In the present review we highlight how MSCs and NSCs in the neurogenic niches interact. Furthermore, we propose directions on this field and explore the future therapeutic possibilities that may arise from the combination/interaction of MSCs and NSCs.

Human Adipose Tissue-Derived Mesenchymal Stem Cells Target Brain Tumor-Initiating Cells

In neuro-oncology, the biology of neural stem cells (NSCs) has been pursued in two ways: as tumor-initiating cells (TICs) and as a potential cell-based vehicle for gene therapy. NSCs as well as mesenchymal stem cells (MSCs) have been reported to possess tumor tropism capacities. However, there is little data on the migratory capacity of MSCs toward brain tumor-initiating cells (BTICs). This study focuses on the ability of human adipose tissue derived MSCs (hAT-MSCs) to target BTICs and their crosstalk in the microenvironment. BTICs were isolated from three different types of brain tumors. The migration capacities of hAT-MSCs toward BTICs were examined using an in vitro migration assay and in vivo bioluminescence imaging analysis. To investigate the crosstalk between hAT-MSCs and BTICs, we analyzed the mRNA expression patterns of cyto-chemokine receptors by RT-qPCR and the protein level of their ligands in co-cultured medium. The candidate cyto-chemokine receptors were selectively inhibited using siRNAs. Both in vitro and in vivo experiments showed that hAT-MSCs possess migratory abilities to target BTICs isolated from medulloblastoma, atypical teratoid/rhabdoid tumors (AT/RT) and glioblastoma. Different types of cyto-chemokines are involved in the crosstalk between hAT-MSCs and BTICs (medulloblastoma and AT/RT: CXCR4/SDF-1, CCR5/RANTES, IL6R/IL-6 and IL8R/IL8; glioblastoma: CXCR4/SDF-1, IL6R/IL-6, IL8R/IL-8 and IGF1R/IGF-1). Our findings demonstrated the migratory ability of hAT-MSCs for BTICs, implying the potential use of MSCs as a delivery vehicle for gene therapy. This study also confirmed the expression of hAT-MSCs cytokine receptors and the BTIC ligands that play roles in their crosstalk.

Prodrug enzymes and their applications in image-guided therapy of cancer: tracking prodrug enzymes to minimize collateral damage

Many cytotoxic therapies are available to kill cancer cells. Unfortunately, these also inflict significant damage on normal cells. Identifying highly effective cancer treatments that have minimal or no side effects continues to be a major challenge. One of the strategies to minimize damage to normal tissue is to deliver an activating enzyme that localizes only in the tumor and converts a nontoxic prodrug to a cytotoxic agent locally in the tumor. Such strategies have been previously tested but with limited success due in large part to the uncertainty in the delivery and distribution of the enzyme. Imaging the delivery of the enzyme to optimize timing of the prodrug administration to achieve image-guided prodrug therapy would be of immense benefit for this strategy. Here, we have reviewed advances in the incorporation of image guidance in the applications of prodrug enzymes in cancer treatment. These advances demonstrate the feasibility of using clinically translatable imaging in these prodrug enzyme strategies.

Delivery of RNA nanoparticles into colorectal cancer metastases following systemic administration

The majority of deaths from all cancers, including colorectal cancer (CRC), is a result of tumor metastasis to distant organs. To date, an effective and safe system capable of exclusively targeting metastatic cancers that have spread to distant organs or lymph nodes does not exist. Here, we constructed multifunctional RNA nanoparticles, derived from the three-way junction (3WJ) of bacteriophage phi29 motor pRNA, to target metastatic cancer cells in a clinically relevant mouse model of CRC metastasis. The RNA nanoparticles demonstrated metastatic tumor homing without accumulation in normal organ tissues surrounding metastatic tumors. The RNA nanoparticles simultaneously targeted CRC cancer cells in major sites of metastasis, such as liver, lymph nodes, and lung. Our results demonstrate the therapeutic potential of these RNA nanoparticles as a delivery system for the treatment of CRC metastasis.

Cerebral angiogenesis during development: who is conducting the orchestra?

Blood vessels provide the brain with the oxygen and the nutrients it requires to develop and function. Endothelial cells (ECs) are the principal cell type forming the vascular system and driving its development and remodeling. All vessels are lined by a single EC layer. Larger blood vessels are additionally enveloped by vascular smooth muscle cells (VSMCs) and pericytes, which increase their stability and regulate their perfusion and form the blood-brain barrier (BBB). The development of the vascular system occurs by two processes: (1) vasculogenesis, the de novo assembly of the first blood vessels, and (2) angiogenesis, the creation of new blood vessels from preexisting ones by sprouting from or by division of the original vessel. The walls of maturing vessels produce a basal lamina and recruit pericytes and vascular smooth muscle cells for structural support. Whereas the process of vasculogenesis seems to be genetically programmed, angiogenesis is induced mainly by hypoxia in development and disease. Both processes and the subsequent vessel maturation are further orchestrated by a complex interplay of inhibiting and stimulating growth factors and their respective receptors, many of which are hypoxia-inducible. This chapter intends to give an overview about the array of factors directing the development and maintenance of the brain vasculature and their interdependent actions.

Advances in stem cell therapy against gliomas

Malignant gliomas are one of the most lethal cancers, and despite extensive research very little progress has been made in improving prognosis. Multimodality treatment combining surgery, radiation, and chemotherapy is the current gold standard, but effective treatment remains difficult due to the invasive nature and high recurrence of gliomas. Stem cell-based therapy using neural, mesenchymal, or hematopoietic stem cells may be an alternative approach because it is tumor selective and allows targeted therapy that spares healthy brain tissue. Stem cells can be used to establish a long-term antitumor response by stimulating the immune system and delivering prodrug, metabolizing genes, or oncolytic viruses. In this review, we discuss current trends and the latest developments in stem cell therapy against malignant gliomas from both the experimental laboratory and the clinic.

Progress from clinical trials and emerging non-conventional therapies for the treatment of Medulloblastomas

Medulloblastomas are highly aggressive tumors of the cerebellum with an embryonal origin. Despite current treatment modalities which include a combination of surgery, chemotherapy and/or radiation, challenges still exist to effectively treat some patients, especially those within the younger age group. In an effort to find improved therapies, ongoing research led by world-wide teams have explored non-conventional therapeutic strategies, as well as examined the efficacy of several drugs in clinical trials among patients with Medulloblastomas. We outline in this article, recent advances on the efficacy and toxicity of numerous therapeutic agents including those that are DNA damaging agents, microtubules binding compounds, and those that are inhibitors of Topoisomerase and of the Notch and Hedgehog signaling pathway, which were assessed in recent Phase I and II clinical trials. Among these clinical trials, it is unfortunate that the outcomes were dismal with the majority of the patients with Medulloblastomas still succumbing to relapse after conventional therapies. Furthermore, it is yet to be established clearly the clinical efficacy of non-conventional therapies such as immunotherapy and gene therapy. Moreover, there is growing interest in proton therapy as a potential replacement for photon therapy, while high dose chemotherapy and autologous stem cell rescue may improve therapeutic efficacies. However, further research is needed to resolve the inherent toxicity from these novel therapeutic methods. In conclusion, novel therapies based on a better understanding of the biology of Medulloblastomas are pivotal in improving non-conventional therapies in the treatment of this deadly disease.

Neural stem cell-mediated CE/CPT-11 enzyme/prodrug therapy in transgenic mouse model of intracerebellar medulloblastoma

Medulloblastoma is a heterogeneous diffuse neoplasm that can be highly disseminated, and is the most common malignant childhood brain tumor. Although multimodal treatments have improved survival rates for patients with medulloblastoma, these tumors are associated with high morbidity and mortality. New treatment strategies are urgently needed to improve cure rates and, importantly, to spare normal brain tissue from neurotoxicity and patients from life-long cognitive and functional deficits associated with current therapies. In numerous preclinical brain tumor models, neural stem cells (NSCs) have shown great promise as delivery vehicles for therapeutic genes. Here, we have used an established, genetically modified human NSC line (HB1.F3.CD) to deliver carboxylesterase (CE) to cerebellar tumor foci and locally activate the prodrug CPT-11 (Irinotecan) to the potent topoisomerase I inhibitor SN-38. HB1.F3.CD NSC tumor tropism, intratumoral distribution and therapeutic efficacy were investigated in clinically relevant experimental models. Magnetic resonance imaging was used for in vivo tracking of iron nanoparticle-labeled NSCs, and to assess the therapeutic efficacy of CE-expressing HB1.F3.CD cells. As compared to controls, a significant decrease in tumor growth rate was seen in mice that received both NSCs and CPT-11 as their treatment regimen. Thus, this study provides proof-of-concept for NSC-mediated CE/CPT-11 treatment of medulloblastoma, and serves as a foundation for further studies toward potential clinical application.