Effect of Human Skin-Derived Stem Cells on Vessel Architecture, Tumor Growth, and Tumor Invasion in Brain Tumor Animal Models

Differential Angiogenic Induction Impacts Nasal Polyp Tissue Growth

In chronic rhinosinusitis with nasal polyps, inflammatory edema drives tissue remodeling favoring anomalous growth of the nasal mucosa, but a proangiogenic contribution of nasal polyp in support of tissue growth is still controversial. The chorioallantoic membrane of chicken embryo model was employed to address the potentiality of nasal tissue fragments to modulate angiogenesis. Fifty-seven fertilized eggs were implanted with polyp or healthy nasal mucosa tissue or were kept as non-implanted controls. The embryos' size, length, and development stage, and chorioallantoic membrane vasculature morphology were evaluated after 48 h. Quantitative computer vision techniques applied to digital chorioallantoic membrane images automatically calculated the branching index as the ratio between the areas of the convex polygon surrounding the vascular tree and the vessels' area. Ethics approval and consent to participate: the study was approved by the Human Research Ethics Committee of the Federal University of São Paulo (CAAE number: 80763117.1.0000.5505) and by the Animal Research Ethics Committee of University of São Paulo (nº CEUA 602-2019). Mucosal, but not polyp tissue implants, hampered embryo development and induced underdeveloped chorioallantoic membranes with anastomosed, interrupted, and regressive vessels. Vessels' areas and branching indexes were higher among the chorioallantoic membranes with polyp implants and controls than among those with healthy mucosa implants. Nasal polyp presents differential angiogenic induction that impacts tissue growth.

Rat Adipose-Derived Stromal Cells (ADSCs) Increases the Glioblastoma Growth and Decreases the Animal Survival

Many studies have shown that mesenchymal stromal cells (MSCs) and their secreted factors may modulate the biology of tumor cells. However, how these interactions happen in vivo remains unclear. In the present study, we investigated the effects of rat adipose-derived stromal cells (ADSCs) and their conditioned medium (ADSC-CM) in glioma tumor growth and malignancy in vivo. Our results showed that when we co-injected C6 cells plus ADSCs into the rat brains, the tumors generated were larger and the animals exhibited shorter survival, when compared with tumors of the animals that received only C6 cells or C6 cells pre-treated with ADSC-CM. We further showed that the animals that received C6 plus ADSC did not present enhanced expression of CD73 (a gene highly expressed in ADSCs), indicating that the tumor volume observed in these animals was not a mere consequence of the higher density of cells administered in this group. Finally, we showed that the animals that received C6 + ADSC presented tumors with larger necrosis areas and greater infiltration of immune cells. These results indicate that the immunoregulatory properties of ADSCs and its contribution to tumor stroma can support tumor growth leading to larger zones of necrosis, recruitment of immune cells, thus facilitating tumor progression. Our data provide new insights into the way by which ADSCs and tumor cells interact and highlight the importance of understanding the fate and roles of MSCs in tumor sites in vivo, as well as their intricate crosstalk with cancer cells.

Ubiquitination Destabilizes Protein Sphingosine Kinase 2 to Regulate Glioma Malignancy

Gliomas are the most common and lethal malignant tumor in the central nervous system. The tumor oncogene sphingosine kinase 2 (SphK2) was previously found to be upregulated in glioma tissues and enhance glioma cell epithelial-to-mesenchymal transition through the AKT/β-catenin pathway. Nevertheless, ubiquitination of SphK2 protein has yet to be well elucidated. In this study, mass spectrometry analysis was performed to identify proteins that interacted with SphK2 protein. Co-immunoprecipitation (co-IP) and immunoblotting (IB) were used to prove the specific interaction between SphK2 protein and the neural precursor cell-expressed developmentally downregulated 4-like (NEDD4L) protein. Fluorescence microscopy was used for detecting the distribution of related proteins. Ubiquitylation assay was utilized to characterize that SphK2 was ubiquitylated by NEDD4L. Cell viability assay, flow cytometry assay, and transwell invasion assay were performed to illustrate the roles of NEDD4L-mediated SphK2 ubiquitination in glioma viability, apoptosis, and invasion, respectively. We found that NEDD4L directly interacted with SphK2 and ubiquinated it for degradation. Ubiquitination of SphK2 mediated by NEDD4L overexpression suppressed glioma cell viability and invasion but promoted glioma apoptosis. Knockdown of NEDD4L presented opposite results. Moreover, further results suggested that ubiquitination of SphK2 regulated glioma malignancy via the AKT/β-catenin pathway. in vivo assay also supported the above findings. This study reveals that NEDD4L mediates SphK2 ubiquitination to regulate glioma malignancy and may provide some meaningful suggestions for glioma treatment.

Adipose-derived stromal cell secretome disrupts autophagy in glioblastoma

Mesenchymal stromal cells (MSCs) are frequently recruited to tumor sites to play a part in the tumor microenvironment (TME). However, their real impact on cancer cell behavior remains obscure. Here we investigated the effects of human adipose-derived stromal cell (hADSC) secretome in autophagy of glioblastoma (GBM), as a way to better comprehend how hADSCs influence the TME. GBM U-87 MG cells were treated with conditioned medium (CM) from hADSCs and autophagic flux was evaluated. hADSC CM treatment blocked the autophagic flux in tumor cells, as indicated by the accumulation of autophagosomes in the cytosol, the high LC3-II and p62/SQSTM1 protein levels, and the lack of increase in the amount of acidic vesicular organelles. These effects were further detected in other GBM cell lines tested and also in co-cultures of hADSCs and U-87 MG. hADSC CM did not compromise lysosomal acidification; however, it was able to activate mTORC1 signaling and, as a consequence, led to a decrease in the nuclear translocation of TFEB, a master transcriptional regulator of lysosomal biogenesis and autophagy, thereby contributing to a defective autophagic process. hADSCs secrete transforming growth factor beta 1 (TGFβ1) and this cytokine is an important mediator of CM effects on autophagy. A comprehensive knowledge of MSC roles in tumor biology is of great importance to shed light on the complex dialog between these cells and to explore such interactions therapeutically. The present results help to elucidate the paracrine effects of MSCs in tumors and bring attention to the potential to be explored in MSC secretome. KEY MESSAGES: hADSC secretome specifically affects the biology of GBM cells. hADSCs block the late steps of autophagic flux in GBM cells. hADSC secretome activates mTORC1 signaling and reduces TFEB nuclear translocation in GBM cells.

LncRNA-ATB promotes TGF-β-induced glioma cells invasion through NF-κB and P38/MAPK pathway

Glioma constitutes the most aggressive primary intracranial malignancy in adults. We previously showed that long noncoding RNA activated by TGF-β (lncRNA-ATB) promoted the glioma cells invasion. However, whether lncRNA-ATB is involved in TGF-β-mediated invasion of glioma cells remains unknown. In this study, quantitative real-time polymerase chain reaction and western blot analysis were used for detecting the mRNA and protein expression of related genes, respectively. Transwell assay was performed to assess the impact of lncRNA-ATB on TGF-β-induced glioma cells migration and invasion. Immunofluorescence staining was utilized to characterize related protein distribution. Results showed that TGF-β upregulated lncRNA-ATB expression in glioma LN-18 and U251 cells. Overexpression of lncRNA-ATB activated nuclear factor-κB (NF-κB) pathway and promoted P65 translocation into the nucleus, thus facilitated glioma cells invasion stimulated by TGF-β. Similarly, lncRNA-ATB markedly enhanced TGF-β-mediated invasion of glioma cells through activation P38 mitogen-activated protein kinase (P38/MAPK) pathway. Moreover, both the NF-κB selected inhibitor pyrrolidinedithiocarbamate ammonium and P38/MAPK specific inhibitor SB203580 partly reversed lncRNA-ATB induced glioma cells invasion mediated by TGF-β. Collectively, this study revealed that lncRNA-ATB promotes TGF-β-induced glioma cell invasion through NF-κB and P38/MAPK pathway and established a detailed framework for understanding the way how lncRNA-ATB performs its function in TGF-β-mediated glioma invasion.

Boosting Antitumor Drug Efficacy with Chemically Engineered Multidomain Proteins

A facile chemical approach integrating supramolecular chemistry, site-selective protein chemistry, and molecular biology is described to engineer synthetic multidomain protein therapeutics that sensitize cancer cells selectively to significantly enhance antitumor efficacy of existing chemotherapeutics. The desired bioactive entities are assembled via supramolecular interactions at the nanoscale into structurally ordered multiprotein complexes comprising a) multiple copies of the chemically modified cyclic peptide hormone somatostatin for selective targeting and internalization into human A549 lung cancer cells expressing SST-2 receptors and b) a new cysteine mutant of the C3bot1 (C3) enzyme from Clostridium botulinum, a Rho protein inhibitor that affects and influences intracellular Rho-mediated processes like endothelial cell migration and blood vessel formation. The multidomain protein complex, SST3-Avi-C3, retargets C3 enzyme into non-small cell lung A549 cancer cells and exhibits exceptional tumor inhibition at a concentration ≈100-fold lower than the clinically approved antibody bevacizumab (Avastin) in vivo. Notably, SST3-Avi-C3 increases tumor sensitivity to a conventional chemotherapeutic (doxorubicin) in vivo. These findings show that the integrated approach holds vast promise to expand the current repertoire of multidomain protein complexes and can pave the way to important new developments in the area of targeted and combination cancer therapy.

Consensus guidelines for the use and interpretation of angiogenesis assays

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference.

Eminent Sources of Adult Mesenchymal Stem Cells and Their Therapeutic Imminence

In the recent times, stem cell biology has garnered the attention of the scientific fraternity and the general public alike due to the immense therapeutic potential that it holds in the field of regenerative medicine. A breakthrough in this direction came with the isolation of stem cells from human embryo and their differentiation into cell types of all three germ layers. However, the isolation of mesenchymal stem cells from adult tissues proved to be advantageous over embryonic stem cells due to the ethical and immunological naivety. Mesenchymal Stem Cells (MSCs) isolated from the bone marrow were found to differentiate into multiple cell lineages with the help of appropriate differentiation factors. Furthermore, other sources of stem cells including adipose tissue, dental pulp, and breast milk have been identified. Newer sources of stem cells have been emerging recently and their clinical applications are also being studied. In this review, we examine the eminent sources of Mesenchymal Stem Cells (MSCs), their immunophenotypes, and therapeutic imminence.

Impact of mesenchymal stem cells' secretome on glioblastoma pathophysiology

Background

Glioblastoma (GBM) is a highly aggressive primary brain cancer, for which curative therapies are not available. An emerging therapeutic approach suggested to have potential to target malignant gliomas has been based on the use of multipotent mesenchymal stem cells (MSCs), either unmodified or engineered to deliver anticancer therapeutic agents, as these cells present an intrinsic capacity to migrate towards malignant tumors. Nevertheless, it is still controversial whether this innate tropism of MSCs towards the tumor area is associated with cancer promotion or suppression. Considering that one of the major mechanisms by which MSCs interact with and modulate tumor cells is via secreted factors, we studied how the secretome of MSCs modulates critical hallmark features of GBM cells.

Methods

The effect of conditioned media (CM) from human umbilical cord perivascular cells (HUCPVCs, a MSC population present in the Wharton’s jelly of the umbilical cord) on GBM cell viability, migration, proliferation and sensitivity to temozolomide treatment of U251 and SNB-19 GBM cells was evaluated. The in vivo chicken chorioallantoic membrane (CAM) assay was used to evaluate the effect of HUCPVCs CM on tumor growth and angiogenesis. The secretome of HUCPVCs was characterized by proteomic analyses.

Results

We found that both tested GBM cell lines exposed to HUCPVCs CM presented significantly higher cellular viability, proliferation and migration. In contrast, resistance of GBM cells to temozolomide chemotherapy was not significantly affected by HUCPVCs CM. In the in vivo CAM assay, CM from HUCPVCs promoted U251 and SNB-19 tumor cells growth. Proteomic analysis to characterize the secretome of HUCPVCs identified several proteins involved in promotion of cell survival, proliferation and migration, revealing novel putative molecular mediators for the effects observed in GBM cells exposed to HUCPVCs CM.

Conclusions

These findings provide novel insights to better understand the interplay between GBM cells and MSCs, raising awareness to potential safety issues regarding the use of MSCs as stem-cell based therapies for GBM.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1303-8) contains supplementary material, which is available to authorized users.

Radicol, a Novel Trinorguaiane-Type Sesquiterpene, Induces Temozolomide-Resistant Glioma Cell Apoptosis via ER Stress and Akt/mTOR Pathway Blockade

Glioblastoma multiforme (GBM) is the most frequent, lethal and aggressive tumour of the central nervous system (CNS) in adults. Multidrug resistance (MDR) results in undesirable prognosis during GBM chemotherapy. In this study, we determined that Radicol (RAD), a novel trinorguaiane-type sesquiterpene originally isolated from the root of Dictamnus radicis Cortex, exhibited potently cytotoxic effect on temozolomide (TMZ)-resistant GBM cell lines in a dose-dependent manner. Radicol-induced apoptosis was confirmed with Hoechst 33342/propidium iodide and terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end-labelling (TUNEL) staining. Studies investigating the mechanism revealed that RAD triggered an attenuation of protein disulphide isomerase (PDI) and induced the unmitigated unfolded protein response (UPR) and lethal endoplasmic reticulum (ER) stress. Simultaneously, we further demonstrated that RAD suppressed the activation of Akt/mTOR/p70S6K phosphorylation by up-regulating the induction of glycogen synthase kinase-3β (GSK-3β). These results established a link between RAD-induced ER stress and inhibition of the Akt/mTOR/p70S6K pathway, and the attenuation of PDI and activation of GSK-3β might be the synergistic target of antineoplastic effects during RAD-induced apoptosis. These findings suggested that RAD, possessing multiple cytotoxicity targets, low molecular weight and high lipid solubility, could be a promising agent for the treatment of malignant gliomas. Copyright © 2017 John Wiley & Sons, Ltd.

Correlation of micro vessel density and c-Myc expression in breast tumor of mice following mesenchymal stem cell therapy

Stem cell therapy for degenerative diseases has been established; however there are controversies over the treatment of solid tumors with stem cell transplantation. In the present study, the anti-tumor action of mesenchymal stem cells (MSCs) has been examined in a mouse model of breast cancer with emphasize on tumor growth, angiogenesis and c-Myc expression in breast tumors. For this purpose, MSCs were isolated from bone marrow of Balb/c mice and characterized. A Balb/c mouse model of breast cancer was developed and subjected to cell therapy intra venous (I.V) or intra tumor (I.T) with MSCs. Tumor growth was measured using a digital caliber for until the end of experiment (30days). Then the mice were sacrificed and their tumors were removed and processed for histopathological examination, immunohistochemical assay of CD31 and measuring of c-Myc expression using quantitative PCR. Detection of the labeled-MSCs in tumors following injection of the cells (I.V or I.T) clearly showed the homing of MSCs into tumors. Tumor growth in case of MSC-treated mice by I.V and I.T routes was inhibited by approximately 28% and 34% respectively compared to controls. The suppression of angiogenesis was reflected in Micro Vessel Density (MVD) following I.V or I.T delivery of the MSCs. c-Myc gene expression in tumor tissues of mice treated I.V or IT with MSCs was down-regulated to 28.0% and 16.0% respectively compare to control groups. In conclusion, growth inhibition of breast tumors in mice due to MSC therapy is associated with modulation of c-Myc activation and angiogenesis markers.

Analysis of the safety of mesenchymal stromal cells secretome for glioblastoma treatment

BACKGROUND AIMS

The purpose of this study was to investigate whether the secretome of human adipose-derived stem cells (hADSC) affects human glioblastoma (GBM) cancer stem cell (CSC) subpopulation or has any influence on drug resistance and cell migration, evaluating the safety of hADSCs for novel cancer therapies.

METHODS

hADSCs were maintained in contact with fresh culture medium to produce hADSCs conditioned medium (CM). GBM U87 cells were cultured with CM and sphere formation, expression of genes related to resistance and CSCs-MGMT, OCT4, SOX2, NOTCH1, MSI1-and protein expression of OCT4 and Nanog were analyzed. The influence of hADSC CM on GBM resistance to temozolomide (TMZ) was evaluated by measuring cumulative population doubling and hADSC CM influence on tumor cell migration was analyzed using transwell assay.

RESULTS

hADSC CM did not alter CSC-related features such as sphere-forming capacity and expression of genes related to CSC. hADSC CM treatment alone did not change proliferation rate of U87 cells and, most important, did not alter the response of tumor cells to TMZ. However, hADSC CM secretome increased the migration capacity of glioblastoma cells.

DISCUSSION

hADSC CM neither induced an enrichment of CSCs in U87 cells population nor interfered in the response to TMZ in culture. Nevertheless, paracrine factors released by hADSCs were able to modulate glioblastoma cells migration. These findings provide novel information regarding the safety of using hADSCs against cancer and highlight the importance of considering hADSC-tumor cells interactions in tumor microenvironment in the design of novel cell therapies.

Wharton's Jelly-Derived Mesenchymal Stromal Cells and Fibroblast-Derived Extracellular Matrix Synergistically Activate Apoptosis in a p21-Dependent Mechanism in WHCO1 and MDA MB 231 Cancer Cells In Vitro

The tumour microenvironment plays a crucial role in tumour progression and comprises tumour stroma which is made up of different cell types and the extracellular matrix (ECM). Mesenchymal stromal cells (MSCs) are part of the tumour stroma and may have conflicting effects on tumour growth. In this study we investigated the effect of Wharton's Jelly-derived MSCs (WJ-MSCs) and a fibroblast-derived ECM (fd-ECM) on esophageal (WHCO1) and breast (MDA MB 231) cancer cells in vitro. Both WJ-MSCs and the fd-ECM, alone or in combination, downregulate PCNA, cyclin D1, Bcl-2, Bcl-xL, and MMPs and upregulate p53 and p21. p21 induction resulted in G2 phase cell cycle arrest and induced apoptosis in vitro. Our data suggest that p21 induction is via p53-dependent and p53-independent mechanisms in WHCO1 and MDA MB 231 cells, respectively. Vascular endothelial growth factor, Akt, and Nodal pathways were downregulated in cancer cells cocultured with WJ-MSCs. We also demonstrate that WJ-MSCs effects on cancer cells appear to be short-lived whilst the fd-ECM effect is long-lived. This study shows the influence of tumour microenvironment on cancer cell behaviour and provides alternative therapeutic targets for potential regulation of tumour cells.

Use of genetically engineered stem cells for glioma therapy

Glioblastoma, the most common and most malignant type of primary brain tumor, is associated with poor prognosis, even when treated using combined therapies, including surgery followed by concomitant radiotherapy with temozolomide-based chemotherapy. The invasive nature of this type of tumor is a major reason underlying treatment failure. The tumor-tropic ability of neural and mesenchymal stem cells offers an alternative therapeutic approach, where these cells may be used as vehicles for the invasion of tumors. Stem cell-based therapy is particularly attractive due to its tumor selectivity, meaning that the stem cells are able to target tumor cells without harming healthy brain tissue, as well as the extensive tumor tropism of stem cells when delivering anti-tumor substances, even to distant tumor microsatellites. Stem cells have previously been used to deliver cytokine genes, suicide genes and oncolytic viruses. The present review will summarize current trends in experimental studies of stem cell-based gene therapy against gliomas, and discuss the potential concerns for translating these promising strategies into clinical use.

Multifunctional properties of chicken embryonic prenatal mesenchymal stem cells- pluripotency, plasticity, and tumor suppression

The chick embryo represents an accessible and economical in vivo model, which has long been used in developmental biology, gene expression analysis, and loss/gain of function experiments. In the present study, we assessed and characterized bone marrow derived mesenchymal stem cells from prenatal day 13 chicken embryos (chBMMSCs) and determined some novel properties. After assessing the mesenchymal stem cell (MSC) properties of these cells by the presence of their signature markers (CD 44, CD 73, CD 90, CD 105, and vimentin), we ascertained a very broad spectrum of multipotentiality as these MSCs not only differentiated into the classic tri-lineages of MSCs but also into ectodermal, endodermal, and mesodermal lineages such as neuron, hepatocyte, islet cell, and cardiac. In addition to wide plasticity, we detected the presence of several pluripotent markers such as Oct4, Sox2, and Nanog. This is the first study characterizing prenatal chBMMSCs and their ability to not only differentiate into mesenchymal lineages but also into all the germ cell layer lineages. Furthermore, our studies indicate that prenatal chBMMSCs derived from the chick provide an excellent model for multi-lineage development studies because of their broad plasticity and faithful reproduction of MSC traits as seen in the human. Here, we also present evidence for the first time that media derived from prenatal chBMMSC cultures have an anti-tumorigenic, anti-migratory, and pro-apoptotic effect on human tumors cells acting through the Wnt-ß-catenin pathway. These data confirm that chBMMSCs are enriched with factors in their secretome that are able to destroy tumor cells. This suggests a commonality of properties of MSCs across species between human and chicken.

Endometrial stem cells in regenerative medicine

First described in 2004, endometrial stem cells (EnSCs) are adult stem cells isolated from the endometrial tissue. EnSCs comprise of a population of epithelial stem cells, mesenchymal stem cells, and side population stem cells. When secreted in the menstrual blood, they are termed menstrual stem cells or endometrial regenerative cells. Mounting evidence suggests that EnSCs can be utilized in regenerative medicine. EnSCs can be used as immuno-modulatory agents to attenuate inflammation, are implicated in angiogenesis and vascularization during tissue regeneration, and can also be reprogrammed into induced pluripotent stem cells. Furthermore, EnSCs can be used in tissue engineering applications and there are several clinical trials currently in place to ascertain the therapeutic potential of EnSCs. This review highlights the progress made in EnSC research, describing their mesodermal, ectodermal, and endodermal potentials both in vitro and in vivo.

Inhibitory effect and mechanism of mesenchymal stem cells on liver cancer cells

Mesenchymal stem cells (MSCs), with their capacity for self-renewal and differentiation into various cell types, are important seed cells for stem cell therapy. MSCs exhibit potent pathotropic migratory properties that make them attractive for use in tumor prevention and therapy. However, little is known about the underlying molecular mechanisms that link MSCs to the targeted tumor cells. This study investigated the inhibitory effect and mechanism of MSCs on human hepatoma HepG2 cells using co-culture and conditioned medium system and animal transplantation model. The HepG2 cells were co-cultured with MSCs or treated with conditional media derived from MSCs cultures in vitro. Results of methylthiazolyldiphenyl tetrazolium assay and flow cytometric assay showed that the proliferation and apoptosis of HepG2 cells decreased and increased, respectively. Reverse transcription polymerase chain reaction analysis showed that the expression levels of bcl-2, c-Myc, β-catenin, and survivin were downregulated. The results of enzyme-linked immunosorbent assay and Western blot proved that MSCs secreted Dkk-1 to inhibit the expression of Wnt signaling pathway-related factors (bcl-2, c-Myc, β-catenin, and survivin) in tumor cells, consequently inhibiting the proliferation and promoting the apoptosis of HepG2 cells. Animal transplantation experiment showed that tumor growth was significantly inhibited when HepG2 cells were co-injected with MSCs into nude mice. These results suggested that MSCs inhibited the growth and promoted the apoptosis of HepG2 cells in a dose-dependent manner. This study provided a new approach and experimental basis for cancer therapy. This study also proved that the Wnt signaling pathway may have a function in MSC-mediated tumor cell inhibition.

Effect of mesenchymal stem cells and a novel curcumin derivative on Notch1 signaling in hepatoma cell line

This study was conducted to evaluate the effect of mesenchymal stem cells (MSCs) and a novel curcumin derivative (NCD) on HepG2 cells (hepatoma cell line) and to investigate their effect on Notch1 signaling pathway target genes. HepG2 cells were divided into HepG2 control group, HepG2 cells treated with MSC conditioned medium (MSCs CM), HepG2 cells treated with a NCD, HepG2 cells treated with MSCs CM and NCD, and HepG2 cells treated with MSCs CM (CM of MSCs pretreated with a NCD). Expression of Notch1, Hes1, VEGF, and cyclin D1 was assessed by real-time, reverse transcription-polymerase chain reaction (RT-PCR) in HepG2 cells. In addition, HepG2 proliferation assay was performed in all groups. Notch1 and its target genes (Hes1 and cyclin D1) were downregulated in all treated groups with more suppressive effect in the groups treated with both MSCs and NCD. Also, treated HepG2 cells showed significant decrease in cell proliferation rate. These data suggest that modulation of Notch1 signaling pathway by MSCs and/or NCD can be considered as a therapeutic target in HCC.

The uncertain role of unmodified mesenchymal stem cells in tumor progression: what master switch?

Mesenchymal stem cells (MSCs) are emerging as promising gene vectors for cancer therapy because of their unique characteristics, including the ease of their expansion and genetic modification and their remarkable tumor-tropic properties. However, there remains a concern that MSCs may promote cancer progression. Surprisingly, there are conflicting reports within the literature describing both the promotion and inhibition of cancer progression by MSCs. The reasons for this discrepancy are still unknown. The surface markers, differentiation ability, and tumorigenic roles of MSCs, as well as their effect on immunoregulation, produce heterogeneity. In this review, we describe the heterogeneity of MSCs by the species from which they are derived, the methodology for their isolation and the context of their interactions with cancer cells. The conflicting roles of MSCs in tumor progression may be attributable to the bimodal effect of unmodified MSCs on immunoregulation. MSCs have been reported to suppress T-cell function and inhibit graft-versus-host disease (GVHD). On the other hand, MSCs elicit the graft-versus-tumor (GVT) effect in some cases. Selective allodepletion may be used to dissociate GVHD from the GVT effect. Understanding the conditions that balance GVHD and the GVT effect of MSCs may be crucial to advance cancer therapy research with respect to MSCs.

Skin-derived multipotent stromal cells--an archrival for mesenchymal stem cells

Progenitor stem cells have been identified, isolated and characterized in numerous tissues and organs. However, their therapeutic potential and the use of these stem cells remain elusive except for a few progenitor cells from bone marrow, umbilical cord blood, eyes and dental pulp. The use of bone marrow-derived hematopoietic stem cells (HSC) or mesenchymal stem cells (MSCs) is restricted due to their extreme invasive procedures, low differentiation potential with age and rejection. Thus, we need a clinical grade alternative to progenitor stem cells with a high potential to differentiate, naïve and is relatively easy in in vitro propagation. In this review, we summarize cell populations of adherent and floating spheres derived from different origins of skin, or correctly foreskin, by enzymatic digestion compared with established MSCs. The morphology, phenotype, differentiation capability and immunosuppressive property of the adherent cell populations are comparable with MSCs. Serum-free cultured floating spheres have limited mesodermal but higher neurogenic differentation potential, analogous to neural crest stem cells. Both the populations confirmed their plethora potential in in vitro. Together, it may be noted that the skin-derived adherent cell populations and floating cells can be good alternative sources of progenitor cells especially in cosmetic, plastic and sports regenerative medicine.

Stem cell-based therapy for malignant glioma

Stem cells have been extensively investigated as tumour-tropic vectors for gene delivery to solid tumours. In this review, we discuss the potential for using stem cells as cellular vector systems in gene therapy for malignant gliomas, with a focus on neural stem cells, and multipotent mesenchymal stromal cells. Tumour cell-derived substances and factors associated with tumour-induced inflammation and tumour neovascularisation can specifically attract stem cells to invasive gliomas. Injected stem cells engineered to produce anti-tumour substances have shown strong therapeutic effects in experimental glioma models. However, the potential caveats include the immunosuppressive functions of multipotent mesenchymal stromal cells, the contribution of stem cells to the pro-tumourigenic stroma, and the malignant transformation of implanted stem cells. In addition, it is not yet known which stem cell types and therapeutic genes will be most effective for the treatment of glioma patients. Here, we highlight the possibilities and problems for translating promising experimental findings in glioma models into the clinic.

Autologous bone marrow cell infusions suppress tumor initiation in hepatocarcinogenic mice with liver cirrhosis

We have previously reported the efficacy and safety of autologous bone marrow cell infusion (ABMi) therapy for liver cirrhosis patients without hepatocellular carcinoma in a multicenter clinical trial. However, since liver cirrhosis is highly oncogenic, evaluation of the effects of ABMi on the mechanisms of hepatocarcinogenesis is of great importance. Therefore, frequent ABMi was performed in hepatocarcinogenic mice, and its effects on hepatocarcinogenesis were analyzed. The N-nitrosodiethylamine (DEN)/green fluorescent protein (GFP)-carbon tetrachloride (CCl(4) ) model was developed by administering DEN once, followed by repeated administration of CCl(4) intraperitoneally as for the control group. In the administration (ABMi) group, GFP-positive bone marrow cells were infused through a tail vein. The kinetics of hepatocarcinogenesis were evaluated histologically 4.5 months after DEN treatment. At 4.5 months, there was significantly lower incidence of foci and tumors in the ABMi group, and they were smaller in number, while their size was almost equal. No GFP-positive tumors were found in ABMi livers. Moreover, ABMi livers showed significantly reduced liver fibrosis, consistent with significantly lower 8-hydroxy-2'-deoxyguanosine levels, higher superoxide dismutase activity, and increased nuclear translocation of nuclear factor-erythroid 2 p45-related factor 2. These results demonstrate that frequent ABMi might contribute to suppressed tumor initiation during stages of hepatocarcinogenesis, consistent with improvements in liver fibrosis and stabilization of redox homeostasis.

Mesenchymal stem cells and glioma cells form a structural as well as a functional syncytium in vitro

The interaction of human mesenchymal stem cells (hMSCs) and tumor cells has been investigated in various contexts. HMSCs are considered as cellular treatment vectors based on their capacity to migrate towards a malignant lesion. However, concerns about unpredictable behavior of transplanted hMSCs are accumulating. In malignant gliomas, the recruitment mechanism is driven by glioma-secreted factors which lead to accumulation of both, tissue specific stem cells as well as bone marrow derived hMSCs within the tumor. The aim of the present work was to study specific cellular interactions between hMSCs and glioma cells in vitro. We show, that glioma cells as well as hMSCs differentially express connexins, and that they interact via gap-junctional coupling. Besides this so-called functional syncytium formation, we also provide evidence of cell fusion events (structural syncytium). These complex cellular interactions led to an enhanced migration and altered proliferation of both, tumor and mesenchymal stem cell types in vitro. The presented work shows that glioma cells display signs of functional as well as structural syncytium formation with hMSCs in vitro. The described cellular phenomena provide new insight into the complexity of interaction patterns between tumor cells and host cells. Based on these findings, further studies are warranted to define the impact of a functional or structural syncytium formation on malignant tumors and cell based therapies in vivo.

Anti-tumor effects of canine adipose tissue-derived mesenchymal stromal cell-based interferon-β gene therapy and cisplatin in a mouse melanoma model

BACKGROUND AIMS

Adipose tissue (AT)-derived mesenchymal stromal cells (MSC) (AT-MSC) represent a novel tool for delivering therapeutic genes to tumor cells. Interferon (IFN)-β is a cytokine with pleiotropic cellular functions, including anti-proliferative, immunomodulatory and anti-angiogenic activities. The purpose of this study was to engineer canine AT-MSC (cAT-MSC) producing IFN-β and to evaluate the anti-tumor effect of cAT-MSC-IFN-β combined with cisplatin in mouse melanoma model.

METHODS

cAT-MSC engineered to express mouse IFN-β were generated using a lentiviral vector (cAT-MSC-IFN-β) and the secreted IFN-β-induced inhibition of tumor cell growth and apoptosis on B16F10 cells was investigated in vitro prior to in vivo studies. Melanoma-bearing mouse was developed by injecting B16F10 cells subcutaneously into 6-week-old C57BL/6 mice. After 14 days, cisplatin (10 mg/kg) was injected intratumorally, and 3 days later the engineered cAT-MSC were injected subcutaneously every 3 days to death. Tumor volume and survival times were measured.

RESULTS

The combination treatment of cAT-MSC-IFN-β with cisplatin was more effective in inhibiting the growth of melanoma and resulted in significantly extended survival time than both an unengineered cAT-MSC-cisplatin combination group and a cisplatin-alone group. Interestingly, subcutaneously injected cAT-MSC-IFN-β were migrated to tumor sites.

CONCLUSIONS

Our data suggest that canine AT-MSC could serve as a powerful cell-based delivery vehicle for releasing therapeutic proteins to tumor lesions. Maximal anti-tumor effects were seen when this therapy was combined with a DNA-damaging chemotherapeutic agent. This study demonstrates the possible applicability of AT-MSC-mediated IFN-β in treating canine and human cancer patients.

Mesenchymal stem cell-mediated cancer therapy: A dual-targeted strategy of personalized medicine

Cancer remains one of the leading causes of mortality and morbidity throughout the world. To a significant extent, current conventional cancer therapies are symptomatic and passive in nature. The major obstacle to the development of effective cancer therapy is believed to be the absence of sufficient specificity. Since the discovery of the tumor-oriented homing capacity of mesenchymal stem cells (MSCs), the application of specific anticancer gene-engineered MSCs has held great potential for cancer therapies. The dual-targeted strategy is based on MSCs' capacity of tumor-directed migration and incorporation and in situ expression of tumor-specific anticancer genes. With the aim of translating bench work into meaningful clinical applications, we describe the tumor tropism of MSCs and their use as therapeutic vehicles, the dual-targeted anticancer potential of engineered MSCs and a putative personalized strategy with anticancer gene-engineered MSCs.

Convergence of normal stem cell and cancer stem cell developmental stage: Implication for differential therapies

Increased evidence shows that normal stem cells may contribute to cancer development and progression by acting as cancer-initiating cells through their interactions with abnormal environmental elements. We postulate that normal stem cells and cancer stem cells (CSC) possess similar mechanisms of self-renewal and differentiation. CSC can be the key to the elaboration of anti-cancer-based therapy. In this article, we focus on a controversial new theme relating to CSC. Tumorigenesis may have a critical stage characterized as a "therapeutic window", which can be identified by association of molecular, biochemical and biological events. Identifying such a stage can allow the production of more effective therapies (e.g. manipulated stem cells) to treat several cancers. More importantly, confirming the existence of a similar therapeutic window during the conversion of normal stem cells to malignant CSC may lead to targeted therapy specifically against CSC. This conversion information may be derived from investigating the biological behaviour of both normal stem cells and cancerous stem cells. Currently, there is little knowledge about the cellular and molecular mechanisms that govern the initiation and maintenance of CSC. Studies on co-evolution and interdependence of cancer with normal tissues may lead to a useful treatment paradigm of cancer. The crosstalk between normal stem cells and cancer formation may converge developmental stages of different types of stem cells (e.g. normal stem cells, CSC and embryonic stem cells). The differential studies of the convergence may result in novel therapies for treating cancers.

The possible roles of brain pericytes in brain ischemia and stroke

Brain pericytes regulate a variety of functions, such as microcirculation, angiogenesis, and the blood brain barrier in the brain. Recent studies have also shown that they are pluripotent in a manner similar to mesenchymal stem cells. Since, brain pericytes actively control these functions, these cells probably play an important role not only during brain ischemia, but also in the post-stroke period.

The role of stem cells in tumor targeting and growth suppression of gliomas

Glioma remains the most challenging solid organ tumor to treat successfully. Based on the capacity of stem cells to migrate extensively and target invading glioma cells, the transplantation of stem cells as a cell-based delivery system may provide additional tools for the treatment of gliomas. In addition to the use of modified stem cells for the delivery of therapeutic agents, unmodified stem cells have been shown to have growth-suppressing effects on tumors in vitro and in vivo. This review outlines the probable factors involved in tumor tropism and tumor growth suppression, with a specific focus on the use of unmodified stem cells in the treatment of gliomas. Based on these and further future data, clinical trials may be justified.

Platelet-derived growth factor (PDGF)-PDGF receptor interaction activates bone marrow-derived mesenchymal stromal cells derived from chronic lymphocytic leukemia: implications for an angiogenic switch

Malignant cells are capable of influencing the microenvironment in a manner that facilitates tumor cell survival. Bidirectional crosstalk between chronic lymphocytic leukemic (CLL) cells and marrow-derived mesenchymal stromal cells (MSCs) activates both cell types. In this study, we observed that the conditioned medium (CM) obtained from CLL cells was able to induce Akt activation in MSC. Subsequent studies investigated the mechanism of MSC activation mediated by CLL-CM. Platelet-derived growth factor receptors (PDGFRs) were selectively activated in MSCs by CLL-CM and found to be critical receptors for CLL-CM-driven MSC proliferation and MSC Akt activation. The known ligands of PDGFR, platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF), were detected in CLL-CM, but PDGF was the predominant ligand involved in the CM-mediated PDGFR activation. Both PDGF and VEGF were found to be elevated in the plasma of CLL patients with a positive association for high-risk factors and more advanced stage. Finally, we demonstrated that PDGF induced MSC VEGF production through a phosphatidylinositol 3-kinase (PI3K)-dependent mechanism. These results show that PDGF-PDGFR signaling influences at least the MSC in the microenvironment of CLL and may play a role in the induction of an angiogenic switch known to be permissive for disease progression.

Toward brain tumor gene therapy using multipotent mesenchymal stromal cell vectors

Gene therapy of solid cancers has been severely restricted by the limited distribution of vectors within tumors. However, cellular vectors have emerged as an effective migratory system for gene delivery to invasive cancers. Implanted and injected multipotent mesenchymal stromal cells (MSCs) have shown tropism for several types of primary tumors and metastases. This capacity of MSCs forms the basis for their use as a gene vector system in neoplasms. Here, we review the tumor-directed migratory potential of MSCs, mechanisms of the migration, and the choice of therapeutic transgenes, with a focus on malignant gliomas as a model system for invasive and highly vascularized tumors. We examine recent findings demonstrating that MSCs share many characteristics with pericytes and that implanted MSCs localize primarily to perivascular niches within tumors, which might have therapeutic implications. The use of MSC vectors in cancer gene therapy raises concerns, however, including a possible MSC contribution to tumor stroma and vasculature, MSC-mediated antitumor immune suppression, and the potential malignant transformation of cultured MSCs. Nonetheless, we highlight the novel prospects of MSC-based tumor therapy, which appears to be a promising approach.

Differentiation of dermal multipotent cells into odontogenic lineage induced by embryonic and neonatal tooth germ cell-conditioned medium

Stem cell-based therapy represents a novel and more advantageous modality of treatment for tooth defect or loss. However, this strategy is challenged in the circumstances where tooth-derived stem cells are not readily accessible. In present study we sought to explore the possibility of utilizing dermal multipotent cells (DMCs) easily available from skin tissue for odontogenic induction. Using the limiting dilution technique, colony-forming cell population was isolated and characterized by proliferative activity and multilineage differentiation potential. By exposure to conditioned medium of embryonic and neonatal tooth germ cells in culture, the proliferation and mineralization activity of DMCs was elevated, while the embryonic tooth germ cell-conditioned medium (ETGC-CM) produced more significant effects. Meanwhile, ETGC-CM-treated DMCs phenocopied the odontoblasts in vitro as indicated by specific lineage markers. Following in vivo transplantation as cell pellet, ETGC-CM-treated DMCs were capable of producing blocks of mineralized tissues, which resembled those of dental pulp stem cell (DPSC) explants in the same subcutaneous pockets environment. These observations suggest that although more sufficient and continuous inductive microenvironment may be needed for undifferentiated DMCs to perform as odontoblasts, ETGC-CM-treated DMCs indeed acquire properties as those of DPSCs. Our work highlights the potential utility of DMCs as an alternative candidate cell source in hopes of developing more practical strategy of tooth regeneration research and offering promising opportunities for therapeutic approach.

Applications of neural and mesenchymal stem cells in the treatment of gliomas

In addition to stem cells providing a better understanding about the biology and origins of gliomas, new therapeutic approaches have been developed based on the use of stem cells as delivery vehicles. The unique ability of stem cells to track down tumor cells makes them a very appealing therapeutic modality. This review introduces neural and mesenchymal stem cells, discusses the advances that have been made in the utilization of these stem cells as therapies and in diagnostic imaging (to track the advancement of the stem cells towards the tumor cells), and concludes by addressing various challenges and concerns regarding these therapies.

Identification of multipotent mesenchymal stromal cells in the reactive stroma of a prostate cancer xenograft by side population analysis

Cancer stem cells are a distinct cellular population that is believed to be responsible for tumor initiation and maintenance. Recent data suggest that solid tumors also contain another type of stem cells, the mesenchymal stem cells or multipotent mesenchymal stromal cells (MSCs), which contribute to the formation of tumor-associated stroma. The Hoechst 33342 efflux assay has proved useful to identify a rare cellular fraction, named Side Population (SP), enriched in cells with stem-like properties. Using this assay, we identified SP cells in a prostate cancer xenograft containing human prostate cancer cells and mouse stromal cells. The SP isolation, subculture and sequential sorting allowed the generation of single-cell-derived clones of murine origin that were recognized as MSC by their morphology, plastic adherence, proliferative potential, adipogenic and osteogenic differentiation ability and immunophenotype (CD45(-), CD81(+) and Sca-1(+)). We also demonstrated that SP clonal cells secrete transforming growth factor beta1 (TGF-beta1) and that their inhibition reduces proliferation and accelerates differentiation. These results reveal the existence of SP cells in the stroma of a cancer xenograft, and provide evidence supporting their MSC nature and the role of TGF-beta1 in maintaining their proliferation and undifferentiated status. Our data also reveal the usefulness of the SP assay to identify and isolate MSC cells from carcinomas.

CXCR4 antagonists: targeting the microenvironment in leukemia and other cancers

Hematopoietic and epithelial cancer cells express CXCR4, a seven-transmembrane G-protein-coupled chemokine receptor. Stromal cells within the bone marrow microenvironment constitutively secrete stromal cell-derived factor-1 (SDF-1/CXCL12), the ligand for CXCR4. Activation of CXCR4 induces leukemia cell trafficking and homing to the marrow microenvironment, where CXCL12 retains leukemia cells in close contact with marrow stromal cells that provide growth and drug resistance signals. CXCR4 antagonists, such as Plerixafor (AMD3100) and T140 analogs, can disrupt adhesive tumor-stroma interactions and mobilize leukemia cells from their protective stromal microenvironment, making them more accessible to conventional drugs. Therefore, targeting the CXCR4-CXCL12 axis is a novel, attractive therapeutic approach that is explored in ongoing clinical trials in leukemia patients. Initially, CXCR4 antagonists were developed for the treatment of HIV, where CXCR4 functions as a co-receptor for virus entry into T cells. Subsequently, CXCR4 antagonists were noticed to induce leukocytosis, and are currently used clinically for mobilization of hematopoietic stem cells. However, because CXCR4 plays a key role in cross-talk between leukemia cells (and a variety of other tumor cells) and their microenvironment, cancer treatment may become the ultimate application of CXCR4 antagonists. Here, we summarize the development of CXCR4 antagonists and their preclinical and clinical activities, focusing on leukemia and other cancers.

The new challenge of stem cell: brain tumour therapy

The surprising similarity of much brain tumour behavior to the intrinsic properties of the neural stem/progenitor cell has triggered a recent interest in both arming stem cells to track and help eradicate tumours and in viewing stem cell biology as somehow integral to the emergence and/or production of the neoplasm itself. Moreover, based on the unique capacity of neural stem cells (NSCs) to migrate throughout the brain and to target invading tumour cells, the transplantation of NSCs offers a new potential therapeutic approach as a cell-based delivery system for gene therapy in brain tumours. On the one hand, both stem cells and cancer cells are thought to be capable of unlimited proliferation. While on the other, many tumours and cancer cell lines express stem cell markers, suggesting either that cancer cells resemble stem cells or that cancers contain stem-like cells. In this review we highlight the close relationship between normal neural stem cells and brain tumour stem cells and also suggest the possible clinical implications that these similarities could offer.

Concise review: adult multipotent stromal cells and cancer: risk or benefit?

This review focuses on the interaction between multipotent stromal cells (MSCs) and carcinoma and the possible use of MSCs in cell-based anticancer therapies. MSCs are present in multiple tissues and are defined as cells displaying the ability to differentiate in multiple lineages, including chondrocytes, osteoblasts, and adipocytes. Recent evidence also suggests that they could play a role in the progression of carcinogenesis and that MSCs could migrate toward primary tumors and metastatic sites. It is possible that MSCs could also be involved in the early stages of carcinogenesis through spontaneous transformation. In addition, it is thought that MSCs can modulate tumor growth and metastasis, although this issue remains controversial and not well understood. The immunosuppressive properties and proangiogenic properties of MSCs account, at least in part, for their effects on cancer development. On the other hand, cancer cells also have the ability to enhance MSC migration. This complex dialog between MSCs and cancer cells is certainly critical for the outcome of tumor development. Interestingly, several studies have shown that MSCs engineered to express antitumor factors could be an innovative choice as a cell-mediated gene therapy to counteract tumor growth. More evidence will be needed to understand how MSCs positively or negatively modulate carcinogenesis and to evaluate the safety of MSC use in cell-mediated gene strategies. Disclosure of potential conflicts of interest is found at the end of this article.

Cytotoxicity of human umbilical cord blood-derived mesenchymal stem cells against human malignant glioma cells

BACKGROUND

Mesenchymal stem cells (MSCs) represent a potential useful source for cell-based glioma therapies because these cells evidence both orthodox and unorthodox plasticity and also show tropism for cancer. In this study, the authors attempted to access the cytotoxicity of human umbilical cord blood (hUCB)-derived MSCs, with or without cytokine activations against malignant glioma cells.

MATERIALS AND METHODS

hUCB-derived MSCs were activated by interleukin-2, interleukin-15, granulocyte macrophage colony-stimulating factor, and combinations. The hUCB-derived MSCs and activated hUCB-derived MSCs were effector cells. The cytotoxicity of the unactivated hUCB-derived MSCs and activated hUCB-derived MSCs against the target cells (human malignant glioma cells) was estimated via visual survival cell assays and transwell inserts. Phenotypic changes occurring in these hUCB-derived MSCs before and after cytokine activation were determined via flow cytometry. The secreted proteins from these effector cells were estimated via enzyme-linked immunosorbent assays.

RESULTS

We noted a significant cytotoxicity of hUCB-derived MSCs against malignant glioma cells. In addition, the hUCB-derived MSCs activated with cytokines evidenced significantly higher cytotoxicity than that observed with unactivated hUCB-derived MSCs. Differentiated immune effectors cells from the hUCB-derived MSCs after cytokine activation were not shown to have increased in number. However, the activated hUCB-derived MSCs secreted more immune response-related proteins (interleukin 4, interferon-gamma) than did the unactivated hUCB-derived MSCs.

CONCLUSION

The data collected herein confirm for the first time that hUCB-derived MSCs, with or without activation, evidence significant cytotoxicity against human malignant glioma cells, and the immune response-related proteins secreted in this process may perform relevant functions.