Antitumor activities of human placenta-derived mesenchymal stem cells expressing endostatin on ovarian cancer

Mesenchymal Stromal Cell-Based Products: Challenges and Clinical Therapeutic Options

Mesenchymal stromal cell (MSC)-based advanced therapy medicinal products (ATMPs) are being tried in a vast range of clinical applications. These cells can be isolated from different donor tissues by using several methods, or they can even be derived from induced pluripotent stem cells or embryonic stem cells. However, ATMP heterogeneity may impact product identity and potency, and, consequently, clinical trial outcomes. In this review, we discuss these topics and the need to establish minimal criteria regarding the manufacturing of MSCs so that these innovative therapeutics may be better positioned to contribute to the advancement of regenerative medicine.

Signaling crosstalk between mesenchymal stem cells and tumor cells: Implications for tumor suppression or progression

Mesenchymal stem cells (MSCs) have been extensively used in various therapeutic applications over the last two decades, particularly in regenerative medicine and cancer treatment. MSCs have the ability to differentiate into mesodermal and non-mesodermal lineages, which makes them a popular choice in tissue engineering and regenerative medicine. Studies have shown that MSCs have inherent tumor-suppressive properties and can affect the behavior of multiple cells contributing to tumor development. Additionally, MSCs possess a tumor tropism property and have a hypoimmune nature. The intrinsic features of MSCs along with their potential to undergo genetic manipulation and be loaded with various anticancer therapeutics have motivated researchers to use them in different cancer therapy approaches without considering their complex dynamic biological aspects. However, despite their desirable features, several reports have shown that MSCs possess tumor-supportive properties. These contradictory results signify the sophisticated nature of MSCs and warn against the potential therapeutic applications of MSCs. Therefore, researchers should meticulously consider the biological properties of MSCs in preclinical and clinical studies to avoid any undesirable outcomes. This manuscript reviews preclinical studies on MSCs and cancer from the last two decades, discusses how MSC properties affect tumor progression and explains the mechanisms behind tumor suppressive and supportive functions. It also highlights critical cellular pathways that could be targeted in future studies to improve the safety and effectiveness of MSC-based therapies for cancer treatment. The insights obtained from this study will pave the way for further clinical research on MSCs and development of more effective cancer treatments.

Proliferative Effects of Mesenchymal Stromal Cells on Neuroblastoma Cell Lines: Are They Tumor Promoting or Tumor Inhibiting?

BACKGROUND

Neuroblastoma is a common pediatric malignancy with poor survival for high-risk disease. Mesenchymal stromal cells (MSCs) have innate tumor-homing properties, enabling them to serve as a cellular delivery vehicle, but MSCs have demonstrated variable effects on tumor growth. We compared how placental MSCs (PMSCs) and bone marrow-derived MSCs (BM-MSCs) affect proliferation of neuroblastoma (NB) cells in vitro.

METHODS

Indirect co-culture assessed proliferative effects of 18 MSCs (early-gestation PMSCs (n = 9), term PMSCs (n = 5), BM-MSCs (n = 4) on three high-risk NB cell lines (NB1643, SH-SY5Y, and CHLA90). Controls were NB cells cultured in media alone. Proliferation was assessed using MTS assay and measured by fold change (fc) over controls. PMSCs were sub-grouped by neuroprotective effect: strong (n = 7), intermediate (n = 3), and weak (n = 4). The relationship between MSC type, PMSC neuroprotection, and PMSC gestational age on NB cell proliferation was assessed.

RESULTS

NB cell proliferation varied between MSC groups. BM-MSCs demonstrated lower proliferative effects than PMSCs (fc 1.18 vs 1.44, p < 0.001). Neither gestational age nor neuroprotection significantly predicted degree of proliferation. Proliferative effects of MSCs varied among NB cell lines. BM-MSCs had less effect on CHLA90 (fc 1.01) compared to NB1643 (fc 1.33) and SH-SY5Y (fc 1.20). Only NB1643 showed a difference between early and term PMSCs (p = 0.04).

CONCLUSION

Effects of MSCs on NB cell proliferation vary by MSC source and NB cell line. BM-MSCs demonstrated lower proliferative effects than most PMSCs. MSC neuroprotection was not correlated with proliferation. Improved understanding of MSC proliferation-promoting mechanisms may provide valuable insight into selection of cells best suited as drug delivery vehicles.

LEVEL OF EVIDENCE

N/A.

TYPE OF STUDY

Original Research.

Current progress in engineered and nano-engineered mesenchymal stem cells for cancer: From mechanisms to therapy

Mesenchymal stem cells (MSCs), as self-renewing multipotent stromal cells, have been considered promising agents for cancer treatment. A large number of studies have demonstrated the valuable properties of MSC-based treatment, such as low immunogenicity and intrinsic tumor-trophic migratory properties. To enhance the potency of MSCs for therapeutic purposes, equipping MSCs with targeted delivery functions using genetic engineering is highly beneficial. Genetically engineered MSCs can express tumor suppressor agents such as pro-apoptotic, anti-proliferative, anti-angiogenic factors and act as ideal delivery vehicles. MSCs can also be loaded with nanoparticle drugs for increased efficacy and externally moderated targeting. Moreover, exosomes secreted by MSCs have important physiological properties, so they can contribute to intercellular communication and transfer cargo into targeted tumor cells. The precise role of genetically modified MSCs in tumor environments is still up for debate, but the beginning of clinical trials has been confirmed by promising results from preclinical investigations of MSC-based gene therapy for a wide range of malignancies. This review highlights the advanced techniques of engineering/nano-engineering and MSC-derived exosomes in tumor-targeted therapy.

Mesenchymal stem cells and ovarian cancer: Is there promising news?

Ovarian cancer (OC) is described as a heterogeneous complex condition with high mortality, weak prognosis, and late-stage presentation. OC has several subgroups based on different indices, like the origin and histopathology. The current treatments against OC include surgery followed by chemotherapy and radiotherapy; however, these methods have represented diverse side effects without enough effectiveness on OC. Recently, mesenchymal stem cell (MSC)-based therapy has acquired particular attention for treating diverse problems, such as cancer. These multipotent stem cells can be obtained from different sources, such as the umbilical cord, adipose tissues, bone marrow, and placenta, and their efficacy has been investigated against OC. Hence, in this narrative review, we aimed to review and discuss the present studies about the effects of various sources of MSCs on OC with a special focus on involved mechanisms.

Application of Perinatal Derivatives on Oncological Preclinical Models: A Review of Animal Studies

The increasing cancer incidence has certified oncological management as one of the most critical challenges for the coming decades. New anticancer strategies are still needed, despite the significant advances brought to the forefront in the last decades. The most recent, promising therapeutic approaches have benefitted from the application of human perinatal derivatives (PnD), biological mediators with proven benefits in several fields beyond oncology. To elucidate preclinical results and clinic outcomes achieved in the oncological field, we present a narrative review of the studies resorting to animal models to assess specific outcomes of PnD products. Recent preclinical evidence points to promising anticancer effects offered by PnD mediators isolated from the placenta, amniotic membrane, amniotic fluid, and umbilical cord. Described effects include tumorigenesis prevention, uncontrolled growth or regrowth inhibition, tumor homing ability, and adequate cell-based delivery capacity. Furthermore, PnD treatments have been described as supportive of chemotherapy and radiological therapies, particularly when resistance has been reported. However, opposite effects of PnD products have also been observed, offering support and trophic effect to malignant cells. Such paradoxical and dichotomous roles need to be intensively investigated. Current hypotheses identify as explanatory some critical factors, such as the type of the PnD biological products used or the manufacturing procedure to prepare the tissue/cellular treatment, the experimental design (including human-relevant animal models), and intrinsic pathophysiological characteristics. The effective and safe translation of PnD treatments to clinical practice relies on the collaborative efforts of all researchers working with human-relevant oncological preclinical models. However, it requires proper guidelines and consensus compiled by experts and health workers who accurately describe the methodology of tissue collection, PnD isolation, manufacturing, preservation, and delivery to the final user.

Anti-tumor effect of local injectable hydrogel-loaded endostatin alone and in combination with radiotherapy for lung cancer

Endostatin (ES) can effectively inhibit neovascularization in most solid tumors and has the potential to make oxygen delivery more efficient and increase the efficacy of radiotherapy (RT). With a short half-life, ES is mainly administered systemically, which leads to low intake in tumor tissue and often toxic systemic side effects. In this study, we used hyaluronic acid-tyramine as a carrier to synthesize an ES-loaded hydrogel drug (ES/HA-Tyr) that can be injected locally. ES/HA-Tyr has a longer half-life and fewer systemic toxic side effects, and it exerts a better anti-angiogenic effect and anti-tumor effect with RT. In vitro, ES/HA-Tyr showed sustained release in the release assay and a stronger ability to inhibit the proliferation of human umbilical vascular endothelial cells (HUVECs) in the MTT assay; it exhibited a more potent effect against HUVEC invasion and a stronger anti-angiogenic effect on HUVECs in tube formation. In vivo, ES/HA-Tyr increased local drug concentration, decreased blood drug concentration, and caused less systemic toxicity. Further, ES/HA-Tyr effectively reduced tumor microvessel density, increased tumor pericyte coverage, decreased tumor hypoxia, and increased RT response. ES/HA-Tyr + RT also had increased anti-tumor and anti-angiogenic effects in Lewis lung cancer (LLC) xenograft models. In conclusion, ES/HA-Tyr showed sustained release, lower systemic toxicity, and better anti-tumor effects than ES. In addition, ES/HA-Tyr + RT enhanced anti-angiogenic effects, reduced tumor hypoxia, and increased the efficacy of RT in LLC-bearing mice.

Prospects for Manipulation of Mesenchymal Stem Cells in Tumor Therapy: Anti-Angiogenesis Property on the Spotlight

The interactions between the tumor microenvironment and the tumor cells confers a condition that accelerate or decelerate the development of tumor. Of these cells, mesenchymal stem cells (MSCs) have the potential to modulate the tumor cells. MSCs have been established with double functions, whereby contribute to a tumorigenic or anti-tumor setting. Clinical studies have indicated the potential of MSCs to be used as tool in treating the human cancer cells. One of the advantageous features of MSCs that make them as a well-suited tool for cancer therapy is the natural tumor-trophic migration potential. A key specification of the tumor development has been stablished to be angiogenesis. As a result, manipulation of angiogenesis has become an attractive approach for cancer therapy. This review article will seek to clarify the anti-angiogenesis strategy in modulating the MSCs to treat the tumor cells.

Mesenchymal Stem Cells as a Gene Delivery Tool: Promise, Problems, and Prospects

The cell-based approach in gene therapy arises as a promising strategy to provide safe, targeted, and efficient gene delivery. Owing to their unique features, as homing and tumor-tropism, mesenchymal stem cells (MSCs) have recently been introduced as an encouraging vehicle in gene therapy. Nevertheless, non-viral transfer of nucleic acids into MSCs remains limited due to various factors related to the main stakeholders of the process (e.g., nucleic acids, carriers, or cells). In this review, we have summarized the main types of nucleic acids used to transfect MSCs, the pros and cons, and applications of each. Then, we have emphasized on the most efficient lipid-based carriers for nucleic acids to MSCs, their main features, and some of their applications. While a myriad of studies have demonstrated the therapeutic potential for engineered MSCs therapy in various illnesses, optimization for clinical use is an ongoing challenge. On the way of improvement, genetically modified MSCs have been combined with various novel techniques and tools (e.g., exosomes, spheroids, 3D-Bioprinting, etc.,) aiming for more efficient and safe applications in biomedicine.

Decreased Inhibition of Proliferation and Induction of Apoptosis in Breast Cancer Cell Lines (T47D and MCF7) from Treatment with Conditioned Medium Derived from Hypoxia-Treated Wharton's Jelly MSCs Compared with Normoxia-Treated MSCs

Background: Mesenchymal stem cells (MSCs) are an appealing source of adult stem cells for cell therapy due to the high rate of proliferation, self-renewal capability, and applicable therapy. Wharton’s jelly (WJ), the main component of the umbilical cord extracellular matrix, comprises multipotent stem cells with a high proliferation rate and self-renewal capability and has anti-cancer properties. MSCs have been reported to secrete a variety of cytokines that have a cytotoxic effect in various cancers. Oxygen tension affects MSCs proliferation, cytokines level but no in surface markers expression, MSCs’ differentiation.

We explored the cytotoxic effect and inducing apoptosis of Wharton’s jelly derived mesenchymal stem cells (WJMSCs) secretions from normoxic WJMSCs (WJMSCs-norCM) (CM: conditioned medium) and hypoxic WJMSCs (WJMSCs-hypoCM) in breast cancer cell lines (T47D and MCF7).

Materials and Methods: Cytotoxic activity was determined using the MTS assay. RT-PCR was performed to measure the expression of apoptosis-inducing genes, specifically P53, BAX, and CASP9, and the antiapoptotic gene BCL-2.

Results: WJMSCs-norCM and WJMSCs-hypoCM were potent inhibitors of the proliferation in both cell lines. WJMSCs-norCM had more anticancer activity in T47D and MCF7. The IC₅₀ value of WJMSCs-norCM on MCF7 was 42.34%, and on T47D was 42.36%. WJMSCs-norCM significantly induced the gene expression of apoptotic P53, BAX, and CASP9 and insignificantly decreased the antiapoptotic gene BCL-2 in both MCF7 and T47D cells. WJMSCs-CM has anticancer activity by inducing P53, BAX, and CASP9 apoptotic genes.

Conclusion: WJMSCs-norCM has more anticancer activity than WJMSCs-hypoCM.

The Current Status of Mesenchymal Stromal Cells: Controversies, Unresolved Issues and Some Promising Solutions to Improve Their Therapeutic Efficacy

Mesenchymal stromal cells (MSCs) currently constitute the most frequently used cell type in advanced therapies with different purposes, most of which are related with inflammatory processes. Although the therapeutic efficacy of these cells has been clearly demonstrated in different disease animal models and in numerous human phase I/II clinical trials, only very few phase III trials using MSCs have demonstrated the expected potential therapeutic benefit. On the other hand, diverse controversial issues on the biology and clinical applications of MSCs, including their specific phenotype, the requirement of an inflammatory environment to induce immunosuppression, the relevance of the cell dose and their administration schedule, the cell delivery route (intravascular/systemic vs. local cell delivery), and the selected cell product (i.e., use of autologous vs. allogeneic MSCs, freshly cultured vs. frozen and thawed MSCs, MSCs vs. MSC-derived extracellular vesicles, etc.) persist. In the current review article, we have addressed these issues with special emphasis in the new approaches to improve the properties and functional capabilities of MSCs after distinct cell bioengineering strategies.

Mesenchymal stem cells and cancer therapy: insights into targeting the tumour vasculature

A crosstalk established between tumor microenvironment and tumor cells leads to contribution or inhibition of tumor progression. Mesenchymal stem cells (MSCs) are critical cells that fundamentally participate in modulation of the tumor microenvironment, and have been reported to be able to regulate and determine the final destination of tumor cell. Conflicting functions have been attributed to the activity of MSCs in the tumor microenvironment; they can confer a tumorigenic or anti-tumor potential to the tumor cells. Nonetheless, MSCs have been associated with a potential to modulate the tumor microenvironment in favouring the suppression of cancer cells, and promising results have been reported from the preclinical as well as clinical studies. Among the favourable behaviours of MSCs, are releasing mediators (like exosomes) and their natural migrative potential to tumor sites, allowing efficient drug delivering and, thereby, efficient targeting of migrating tumor cells. Additionally, angiogenesis of tumor tissue has been characterized as a key feature of tumors for growth and metastasis. Upon introduction of first anti-angiogenic therapy by a monoclonal antibody, attentions have been drawn toward manipulation of angiogenesis as an attractive strategy for cancer therapy. After that, a wide effort has been put on improving the approaches for cancer therapy through interfering with tumor angiogenesis. In this article, we attempted to have an overview on recent findings with respect to promising potential of MSCs in cancer therapy and had emphasis on the implementing MSCs to improve them against the suppression of angiogenesis in tumor tissue, hence, impeding the tumor progression.

Enhancement of the Therapeutic Capacity of Mesenchymal Stem Cells by Genetic Modification: A Systematic Review

Background

The therapeutic capacity of mesenchymal stem cells (also known as mesenchymal stromal cells/MSCs) depends on their ability to respond to the need of the damaged tissue by secreting beneficial paracrine factors. MSCs can be genetically engineered to express certain beneficial factors. The aim of this systematic review is to compile and analyze published scientific literatures that report the use of engineered MSCs for the treatment of various diseases/conditions, to discuss the mechanisms of action, and to assess the efficacy of engineered MSC treatment.

Methods

We retrieved all published studies in PubMed/MEDLINE and Cochrane Library on July 27, 2019, without time restriction using the following keywords: “engineered MSC” and “therapy” or “manipulated MSC” and “therapy.” In addition, relevant articles that were found during full text search were added. We identified 85 articles that were reviewed in this paper.

Results

Of the 85 articles reviewed, 51 studies reported the use of engineered MSCs to treat tumor/cancer/malignancy/metastasis, whereas the other 34 studies tested engineered MSCs in treating non-tumor conditions. Most of the studies reported the use of MSCs in animal models, with only one study reporting a trial in human subjects. Thirty nine studies showed that the expression of beneficial paracrine factors would significantly enhance the therapeutic effects of the MSCs, whereas thirty three studies showed moderate effects, and one study in humans reported no effect. The mechanisms of action for MSC-based cancer treatment include the expression of “suicide genes,” induction of tumor cell apoptosis, and delivery of cytokines to induce an immune response against cancer cells. In the context of the treatment of non-cancerous diseases, the mechanism described in the reviewed papers included the expression of angiogenic, osteogenic, and growth factors.

Conclusion

The therapeutic capacity of MSCs can be enhanced by inducing the expression of certain paracrine factors by genetic modification. Genetically engineered MSCs have been used successfully in various animal models of diseases. However, the results should be interpreted cautiously because animal models might not perfectly represent real human diseases. Therefore, further studies are needed to explore the translational potential of genetically engineered MSCs.

Mesenchymal Stem Cells: The Past Present and Future

The biomedical applications of mesenchymal stem cells (MSCs) have gained expanding attention over the past three decades. MSCs are easily obtained from various tissue types (e.g. bone marrow, fat, cord blood, etc.), are capable of self-renewal, and could be induced to differentiate into several cell lineages for countless biomedical applications. In addition, when transplanted, MSCs are not detected by immune surveillance, thus do not lead to graft rejection. Moreover, they can home towards affected tissues and induce their therapeutic effect in a cell-base and/or a cell-free manner. These properties, and many others, have made MSCs appealing therapeutic cell candidates (for cell and/or gene therapy) in myriad clinical conditions. However, similar to any other therapeutic tool, MSCs still have their own limitations and grey areas that entail more research for better understanding and optimization. Herein, we present a brief overview of various pre-clinical/clinical applications of MSCs in regenerative medicine and discuss limitations and future challenges.

New Insights Into Implementation of Mesenchymal Stem Cells in Cancer Therapy: Prospects for Anti-angiogenesis Treatment

Tumor microenvironment interacts with tumor cells, establishing an atmosphere to contribute or suppress the tumor development. Among the cells which play a role in the tumor microenvironment, mesenchymal stem cells (MSCs) have been demonstrated to possess the ability to orchestrate the fate of tumor cells, drawing the attention to the field. MSCs have been considered as cells with double-bladed effects, implicating either tumorigenic or anti-tumor activity. On the other side, the promising potential of MSCs in treating human cancer cells has been observed from the clinical studies. Among the beneficial characteristics of MSCs is the natural tumor-trophic migration ability, providing facility for drug delivery and, therefore, targeted treatment to detach tumor and metastatic cells. Moreover, these cells have been the target of engineering approaches, due to their easily implemented traits, in order to obtain the desired expression of anti-angiogenic, anti-proliferative, and pro-apoptotic properties, according to the tumor type. Tumor angiogenesis is the key characteristic of tumor progression and metastasis. Manipulation of angiogenesis has become an attractive approach for cancer therapy since the introduction of the first angiogenesis inhibitor, namely bevacizumab, for metastatic colorectal cancer therapy. This review tries to conclude the approaches, with focus on anti-angiogenesis approach, in implementing the MSCs to combat against tumor cell progression.

Effect of mesenchymal stem cells-derived exosomes on tumor microenvironment: Tumor progression versus tumor suppression

Mesenchymal stem cells (MSCs) are multipotent cells with the potential to differentiate into different cell types. Owing to their immunosuppressive and anti-inflammatory properties, they are widely used in regenerative medicine, but they have a dual effect on cancer progression and exert both growth-stimulatory or -inhibitory effects on different cancer types. It has been proposed that these controversial effects of MSC in tumor microenvironment (TME) are mediated by their polarization to proinflammatory or anti-inflammatory phenotype. In addition, they can polarize the immune system cells that in turn influence tumor progression. One of the mechanisms involved in the TME communications is extracellular vesicles (EVs). MSCs, as one of cell populations in TME, produce a large amount of EVs that can influence tumor development. Similar to MSC, MSC-EVs can exert both anti- or protumorigenic effects. In the current study, we will investigate the current knowledge related to MSC role in cancer progression with a focus on the MSC-EV content in limiting tumor growth, angiogenesis, and metastasis. We suppose MSC-EVs can be used as safe vehicles for delivering antitumor agents to TME.

MRI tracking of polyethylene glycol-coated superparamagnetic iron oxide-labelled placenta-derived mesenchymal stem cells toward glioblastoma stem-like cells in a mouse model

Mesenchymal stem cells (MSCs) that display homing and infiltration properties towards tumor cells are a promising cellular targeting vector for brain tumor therapy but are limited to local-regional delivery in current preclinical models. Here, we investigated whether placenta-derived MSCs (P-MSCs) are a superior cellular vector for systemic targeting of glioblastoma stem-like cells (GSCs), with an imaging modality to real-time monitor the trafficking P-MSCs to glioblastoma sites. Results demonstrated that P-MSCs had greater migratory activity towards GSCs and across blood-brain barrier compared with bone marrow-derived MSCs, and this activity was enhanced by hypoxia precondition. Chemokine ligand 5 was identified as a chemoattractant responsible for the glioblastoma tropism of P-MSCs. Polyethylene glycol-coated superparamagnetic iron oxide (PEG-SPIO) was synthesized for cellular labelling and imaging P-MSCs, displaying high cellular uptake and no cytotoxic effect on P-MSCs cell proliferation or stemness property. The homing effects of intravenously administered PEG-SPIO-labelled P-MSCs towards intracerebral GSCs were able to be detected in mice models through T2-weighted magnetic resonance imaging (MRI). This study suggests the possibility of innovative systemic P-MSC-based cell therapy for aggressive GSCs, developing a state-of-the-art theranostic technique for real-time tracking of therapeutic P-MSCs tumor infiltration through cellular MRI.

Placenta-derived multipotent cells have no effect on the size and number of DMH-induced colon tumors in rats

Transplantation of placenta-derived multipotent cells (PDMCs) is a promising approach for cell therapy to treat inflammation-associated colon diseases. However, the effect of PDMCs on colon cancer cells remains unknown. The aim of the present study was to characterize PDMCs obtained from human (hPDMCs) and rat (rPDMCs) placentas and to evaluate their impact on colon cancer progression in rats. PDMCs were obtained from human and rat placentas by tissue explant culturing. Stemness- and trophoblast-related gene expression was studied using reverse transcription-polymerase chain reaction (RT-PCR), and surface markers and intracellular proteins were detected using flow cytometry and immunofluorescence, respectively. Experimental colon carcinogenesis was induced in male albino Wistar rats by injecting 20 mg/kg dimethylhydrazine (DMH) once a week for 20 consecutive weeks. The administration of rPDMCs and hPDMC was performed at week 22 after the initial DMH-injection. All animals were sacrificed through carbon dioxide asphyxiation at week 5 after cell transplantation. The number and size of each tumor lesion was calculated. The type of tumor was determined by standard histological methods. Cell engraftment was determined by PCR and immunofluorescence. Results demonstrated that rPDMCs possessed the immunophenotype and differentiation potential inherent in MSCs; however, hPDMCs exhibited a lower expression of cluster of differentiation 44 and did not express trophoblast-associated genes. The data of the present study indicated that PDMCs may engraft in different tissues but do not significantly affect DMH-induced tumor growth during short-term observations.

Metastatic Ovarian Cancer Can Be Efficiently Treated by Genetically Modified Mesenchymal Stromal Cells

Due to late diagnosis, often recurrence, formation of metastases and resistance to commonly used chemotherapeutics human ovarian carcinoma represents a serious disease with high mortality. Adipose tissue-derived mesenchymal stromal cells (AT-MSC) can serve as vehicles for therapeutic genes and we engineered AT-MSC to express either Herpes simplex virus thymidine kinase (HSVtk-MSC), which phosphorylates ganciclovir (GCV) to its toxic metabolites or yeast fused cytosine deaminase::uracil phosphoribosyltransferase (CD::UPRT-MSC), which converts 5-fluorocytosine (5-FC) to highly toxic 5-fluorouracil (5-FU). Here, we reported different responses of cytotoxicity mediated by CD::UPRT-MSC/5-FC treatment on human ovarian carcinoma cell lines-SKOV-3 and A2780 used in adherent or three-dimensional (3D) cell culture and we proved high potential of 3D model to predict results in our in vivo experiments. Both tumor cell lines showed similarly high chemosensitivity to the used treatment in adherent culture, but 3D model revealed severe discrepancy-only 36% of SKOV-3 cells but even 90% of A2780 cells were eliminated. This result served as a prognostic marker-we were able to achieve significantly decreased tumor volumes of subcutaneous xenografts of A2780 cells in nude mice and we prolonged tumor-free survival in 33% of animals bearing highly metastatic ovarian carcinoma after CD::UPRT-MSC/5-FC treatment.

Antitumor activity of pluripotent cell-engineered vaccines and their potential to treat lung cancer in relation to different levels of irradiation

Cancer stem cells (CSCs) are critical for tumor initiation/maintenance and recurrence or metastasis, so they may serve as a potential therapeutic target. However, CSC-established multitherapy resistance and immune tolerance render tumors resistant to current tumor-targeted strategies. To address this, renewable multiepitope-integrated spheroids based on placenta-derived mesenchymal stem cells (pMSCs) were X-ray-modified, at four different irradiation levels, including 80, 160, 240, and 320 Gy, as pluripotent biologics, to inoculate hosts bearing Lewis lung carcinoma (LL2) and compared with X-ray-modified common LL2 cells as control. We show that the vaccines at the 160/240 Gy irradiation levels could rapidly trigger tumor cells into the apoptosis loop and evidently prolong the tumor-bearing host's survival cycle, in contrast to vaccines irradiated at other levels (P<0.05), with tumor-sustaining stromal cell-derived factor-1/CXCR4 pathway being selectively blockaded. Meanwhile, almost no or minimal toxicity was detected in the vaccinated hosts. Importantly, 160/240 Gy-irradiated vaccines could provoke significantly higher killing of CSCs and non-CSCs, which may provide an access to developing a novel biotherapy against lung carcinoma.

Stem Cell-Based Therapies for Cancer

Stem cell-based therapeutic strategies have emerged as very attractive treatment options over the past decade. Stem cells are now being utilized as delivery vehicles especially in cancer therapy to deliver a number of targeted proteins and viruses. This chapter aims to shed light on numerous studies that have successfully employed these strategies to target various cancer types with a special emphasis on numerous aspects that are critical to the success of future stem cell-based therapies for cancer.

Stem cells' guided gene therapy of cancer: New frontier in personalized and targeted therapy

INTRODUCTION

Diagnosis and therapy of cancer remain to be the greatest challenges for all physicians working in clinical oncology and molecular medicine. The statistics speak for themselves with the grim reports of 1,638,910 men and women diagnosed with cancer and nearly 577,190 patients passed away due to cancer in the USA in 2012. For practicing clinicians, who treat patients suffering from advanced cancers with contemporary systemic therapies, the main challenge is to attain therapeutic efficacy, while minimizing side effects. Unfortunately, all contemporary systemic therapies cause side effects. In treated patients, these side effects may range from nausea to damaged tissues. In cancer survivors, the iatrogenic outcomes of systemic therapies may include genomic mutations and their consequences. Therefore, there is an urgent need for personalized and targeted therapies. Recently, we reviewed the current status of suicide gene therapy for cancer. Herein, we discuss the novel strategy: genetically engineered stem cells' guided gene therapy.

REVIEW OF THERAPEUTIC STRATEGIES IN PRECLINICAL AND CLINICAL TRIALS

Stem cells have the unique potential for self renewal and differentiation. This potential is the primary reason for introducing them into medicine to regenerate injured or degenerated organs, as well as to rejuvenate aging tissues. Recent advances in genetic engineering and stem cell research have created the foundations for genetic engineering of stem cells as the vectors for delivery of therapeutic transgenes. Specifically in oncology, the stem cells are genetically engineered to deliver the cell suicide inducing genes selectively to the cancer cells only. Expression of the transgenes kills the cancer cells, while leaving healthy cells unaffected. Herein, we present various strategies to bioengineer suicide inducing genes and stem cell vectors. Moreover, we review results of the main preclinical studies and clinical trials. However, the main risk for therapeutic use of stem cells is their cancerous transformation. Therefore, we discuss various strategies to safeguard stem cell guided gene therapy against iatrogenic cancerogenesis.

PERSPECTIVES

Defining cancer biomarkers to facilitate early diagnosis, elucidating cancer genomics and proteomics with modern tools of next generation sequencing, and analyzing patients' gene expression profiles provide essential data to elucidate molecular dynamics of cancer and to consider them for crafting pharmacogenomics-based personalized therapies. Streamlining of these data into genetic engineering of stem cells facilitates their use as the vectors delivering therapeutic genes into specific cancer cells. In this realm, stem cells guided gene therapy becomes a promising new frontier in personalized and targeted therapy of cancer.

Reduced expression of 11β-hydroxysteroid dehydrogenase type 2 in preeclamptic placentas is associated with decreased PPARγ but increased PPARα expression

Placental 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) is reduced in pregnancies complicated with preeclampsia (PE). Peroxisome proliferator-activated receptors β/δ (PPARβ/δ) have been shown to suppress 11β-HSD2 expression in human placental cells. Our objectives were to investigate whether the reduced 11β-HSD2 expression is associated with the changes in PPARs in PE placentas, and whether PPARα and PPARγ affect 11β-HSD2 expression in placental cells. PPARα and PPARβ/δ mRNA and protein expression was increased, whereas PPARγ mRNA and protein expression was decreased in PE placentas. 11β-HSD2 protein expression was inversely correlated with PPARβ/δ in normal placentas but correlated positively with PPARγ and inversely to PPARα in PE placentas. In cultured placental cells, PPARα agonist inhibited, whereas PPARγ agonist stimulated, 11β-HSD2 mRNA and protein expression and activity in a dose-dependent manner. Knockdown of retinoid X nuclear receptor α (RXRα) resulted in a loss of PPARγ effect but not PPARα effect on11β-HSD2. The PPARα effect remained, but the PPARγ effect was lost in the presence of the translational inhibitor cycloheximide. PPARγ agonist dose-dependently stimulated specificity protein 1 (Sp-1) protein expression. Inhibition or knockdown of Sp-1 resulted in a loss of the effects of PPARα and PPARγ. The Sp-1 protein level was not correlated with 11β-HSD2 and PPARs in normal placentas, whereas Sp-1 expression was correlated with 11β-HSD2, PPARγ, and PPARβ/δ in PE placentas. Our data indicate that 11β-HSD2 expression can be modulated by PPARα and PPARγ in placental trophoblasts through Sp-1. Decreased 11β-HSD2 expression in PE placenta might be associated with decreased PPARγ but increased PPARα expression.

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

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