Inhibition of neuronal nitric oxide synthase activity promotes migration of human-induced pluripotent stem cell-derived neural stem cells toward cancer cells

Gasotransmitters in the tumor microenvironment: Impacts on cancer chemotherapy (Review)

Nitric oxide, carbon monoxide and hydrogen sulfide are three endogenous gasotransmitters that serve a role in regulating normal and pathological cellular activities. They can stimulate or inhibit cancer cell proliferation and invasion, as well as interfere with cancer cell responses to drug treatments. Understanding the molecular pathways governing the interactions between these gases and the tumor microenvironment can be utilized for the identification of a novel technique to disrupt cancer cell interactions and may contribute to the conception of effective and safe cancer therapy strategies. The present review discusses the effects of these gases in modulating the action of chemotherapies, as well as prospective pharmacological and therapeutic interfering approaches. A deeper knowledge of the mechanisms that underpin the cellular and pharmacological effects, as well as interactions, of each of the three gases could pave the way for therapeutic treatments and translational research.

Arginine Metabolism and Its Potential in Treatment of Colorectal Cancer

Colorectal cancer is the leading cause of death from cancer globally. The current treatment protocol still heavily relies on early detection and surgery. The molecular mechanisms underlying development of colorectal cancer are clinically important and determine the prognosis and treatment response. The arginine metabolism pathway is hyperactive in colorectal cancer and several molecules involved in the pathway are potential targets for chemoprevention and targeted colorectal cancer therapy. Endothelial nitric oxide synthase (eNOS), argininosuccinate synthetase and ornithine decarboxylase (ODC) are the main enzymes for arginine metabolism. Limiting arginine-rich meat consumption and inhibiting ODC activity largely reduces polyamine synthesis and the incidence of colorectal cancer. Arginine transporter CAT-1 and Human member 14 of the solute carrier family 6 (SLC6A14) are overexpressed in colorectal cancer cells and contributes to intracellular arginine levels. Human member 9 of the solute carrier family 38 (SLC38A9) serves as a component of the lysosomal arginine-sensing machinery. Pharmaceutical inhibition of single enzyme or arginine transporter is hard to meet requirement of restoring of abnormal arginine metabolic network. Apart from application in early screening for colorectal cancer, microRNA-based therapeutic strategy that simultaneously manipulating multiple targets involved in arginine metabolism brings promising future in the treatment of colorectal cancer.

Effect of leukocyte inhibitory factor on neuron differentiation from human induced pluripotent stem cell-derived neural precursor cells

Direct derivation of human induced pluripotent stem cells into neural precursor cells and differentiation of these into neurons holds great promise in the cell therapy of neuro-degenerative diseases. However, the availability and survival rate of neurons requires improvement. In the present study, it was found that the addition of 5 ng/ml leukocyte inhibitory factor (LIF) during the process of differentiation significantly improved the expression of neuron-specific class III β-tubulin (TUJ1) and microtubule-associated protein 2 (MAP2), as detected by immunofluorescence and western blotting. In addition, LIF improved the cell viability, increased the expression of phosphorylated-protein kinase B (AKT), downregulated the expression of proinflammatory cytokines, including interleukin-1α (IL-1α) and tumor necrosis factor-α (TNF-α), and upregulated the expression of anti-inflammatory cytokines, including interleukin-10 (IL-10) and transforming growth factor-β (TGF-β). After adding the phosphatidylinositol 3-kinase (PI3K)/AKT signaling inhibitor LY294002 or wortmannin to the LIF differentiation group, LIF-induced changes in the protein expression of TUJ1 and MAP2 were reversed, but this effect could not be prevented by rapamycin, a mechanistic target of rapamycin signaling inhibitor. The expression of cytokines associated with inflammation and cell viability was reversed by LY294002 and wortmannin, but not by rapamycin. In conclusion, LIF could improve neuronal differentiation and survival through the activation of PI3K/AKT signaling and the anti-inflammatory effect. The anti-inflammatory effect may be mediated by the activation of PI3K/AKT.

Nitric Oxide Modulates Postnatal Bone Marrow-Derived Mesenchymal Stem Cell Migration

Nitric oxide (NO) is a small free-radical gas molecule, which is highly diffusible and can activate a wide range of downstream effectors, with rapid and widespread cellular effects. NO is a versatile signaling mediator with a plethora of cellular functions. For example, NO has been shown to regulate actin, the microfilament, dependent cellular functions, and also acts as a putative stem cell differentiation-inducing agent. In this study, using a wound-healing model of cellular migration, we have explored the effect of exogenous NO on the kinetics of movement and morphological changes in postnatal bone marrow-derived mesenchymal stem cells (MSCs). Cellular migration kinetics and morphological changes of the migrating MSCs were measured in the presence of an NO donor (S-Nitroso-N-Acetyl-D,L-Penicillamine, SNAP), especially, to track the dynamics of single-cell responses. Two experimental conditions were assessed, in which SNAP (200 μM) was applied to the MSCs. In the first experimental group (SN-1), SNAP was applied immediately following wound formation, and migration kinetics were determined for 24 h. In the second experimental group (SN-2), MSCs were pretreated for 7 days with SNAP prior to wound formation and the determination of migration kinetics. The generated displacement curves were further analyzed by non-linear regression analysis. The migration displacement of the controls and NO treated MSCs (SN-1 and SN-2) was best described by a two parameter exponential functions expressing difference constant coefficients. Additionally, changes in the fractal dimension (D) of migrating MSCs were correlated with their displacement kinetics for all the three groups. Overall, these data suggest that NO may evidently function as a stop migration signal by disordering the cytoskeletal elements required for cell movement and proliferation of MSCs.

Targeted Inhibition of the miR-199a/214 Cluster by CRISPR Interference Augments the Tumor Tropism of Human Induced Pluripotent Stem Cell-Derived Neural Stem Cells under Hypoxic Condition

The human induced pluripotent stem cell (hiPSC) provides a breakthrough approach that helps overcoming ethical and allergenic challenges posed in application of neural stem cells (NSCs) in targeted cancer gene therapy. However, the tumor-tropic capacity of hiPSC-derived NSCs (hiPS-NSCs) still has much room to improve. Here we attempted to promote the tumor tropism of hiPS-NSCs by manipulating the activity of endogenous miR-199a/214 cluster that is involved in regulation of hypoxia-stimulated cell migration. We first developed a baculovirus-delivered CRISPR interference (CRISPRi) system that sterically blocked the E-box element in the promoter of the miR-199a/214 cluster with an RNA-guided catalytically dead Cas9 (dCas9). We then applied this CRISPRi system to hiPS-NSCs and successfully suppressed the expression of miR-199a-5p, miR-199a-3p, and miR-214 in the microRNA gene cluster. Meanwhile, the expression levels of their targets related to regulation of hypoxia-stimulated cell migration, such as HIF1A, MET, and MAPK1, were upregulated. Further migration assays demonstrated that the targeted inhibition of the miR-199a/214 cluster significantly enhanced the tumor tropism of hiPS-NSCs both in vitro and in vivo. These findings suggest a novel application of CRISPRi in NSC-based tumor-targeted gene therapy.

The Use of Patient-Specific Induced Pluripotent Stem Cells (iPSCs) to Identify Osteoclast Defects in Rare Genetic Bone Disorders

More than 500 rare genetic bone disorders have been described, but for many of them only limited treatment options are available. Challenges for studying these bone diseases come from a lack of suitable animal models and unavailability of skeletal tissues for studies. Effectors for skeletal abnormalities of bone disorders may be abnormal bone formation directed by osteoblasts or anomalous bone resorption by osteoclasts, or both. Patient-specific induced pluripotent stem cells (iPSCs) can be generated from somatic cells of various tissue sources and in theory can be differentiated into any desired cell type. However, successful differentiation of hiPSCs into functional bone cells is still a challenge. Our group focuses on the use of human iPSCs (hiPSCs) to identify osteoclast defects in craniometaphyseal dysplasia. In this review, we describe the impact of stem cell technology on research for better treatment of such disorders, the generation of hiPSCs from patients with rare genetic bone disorders and current protocols for differentiating hiPSCs into osteoclasts.

A Double-Switch Cell Fusion-Inducible Transgene Expression System for Neural Stem Cell-Based Antiglioma Gene Therapy

Recent progress in neural stem cell- (NSC-) based tumor-targeted gene therapy showed that NSC vectors expressing an artificially engineered viral fusogenic protein, VSV-G H162R, could cause tumor cell death specifically under acidic tumor microenvironment by syncytia formation; however, the killing efficiency still had much room to improve. In the view that coexpression of another antitumoral gene with VSV-G can augment the bystander effect, a synthetic regulatory system that triggers transgene expression in a cell fusion-inducible manner has been proposed. Here we have developed a double-switch cell fusion-inducible transgene expression system (DoFIT) to drive transgene expression upon VSV-G-mediated NSC-glioma cell fusion. In this binary system, transgene expression is coregulated by a glioma-specific promoter and targeting sequences of a microRNA (miR) that is highly expressed in NSCs but lowly expressed in glioma cells. Thus, transgene expression is "switched off" by the miR in NSC vectors, but after cell fusion with glioma cells, the miR is diluted and loses its suppressive effect. Meanwhile, in the syncytia, transgene expression is "switched on" by the glioma-specific promoter. Our in vitro and in vivo experimental data show that DoFIT successfully abolishes luciferase reporter gene expression in NSC vectors but activates it specifically after VSV-G-mediated NSC-glioma cell fusion.

Cells as delivery vehicles for cancer therapeutics

Cell-based therapeutics have advanced significantly over the past decade and are poised to become a major pillar of modern medicine. Three cell types in particular have been studied in detail for their ability to home to tumors and to deliver a variety of different payloads. Neural stem cells, mesenchymal stem cells and monocytes have each been shown to have great potential as future delivery systems for cancer therapy. A variety of other cell types have also been studied. These results demonstrate that the field of cell-based therapeutics will only continue to grow.

Induced pluripotent stem cell reprogramming by integration-free Sendai virus vectors from peripheral blood of patients with craniometaphyseal dysplasia

Studies of rare genetic bone disorders are often limited due to unavailability of tissue specimens and the lack of animal models fully replicating phenotypic features. Craniometaphyseal dysplasia (CMD) is a rare monogenic disorder characterized by hyperostosis of craniofacial bones concurrent with abnormal shape of long bones. Mutations for autosomal dominant CMD have been identified in the ANK gene (ANKH). Here we describe a simple and efficient method to reprogram adherent cells cultured from peripheral blood to human induced pluripotent stem cells (hiPSCs) from eight CMD patients and five healthy controls. Peripheral blood mononuclear cells (PBMCs) were separated from 5-7 mL of whole blood by Ficoll gradient, expanded in the presence of cytokines and transduced with Sendai virus (SeV) vectors encoding OCT3/4, SOX2, KLF4, and c-MYC. SeV vector, a cytoplasmic RNA vector, is lost from host cells after propagation for 10-13 passages. These hiPSCs express stem cell markers, have normal karyotypes, and are capable of forming embryoid bodies in vitro as well as teratomas in vivo. Further differentiation of these patient-specific iPSCs into osteoblasts and osteoclasts can provide a useful tool to study the effects CMD mutations on bone, and this approach can be applied for disease modeling of other rare genetic musculoskeletal disorders.