Differential gene expression associated with migration of mesenchymal stem cells to conditioned medium from tumor cells or bone marrow cells

Mesenchymal Stem Cells in Cancer Therapy

The mesenchymal stem/stromal cells (MSCs) are multipotent cells that were initially discovered in the bone marrow in the late 1960s but have so far been discovered in almost all tissues of the body. The multipotent property of MSCs enables them to differentiate into various cell types and lineages, such as adipocytes, chondrocytes, and osteocytes. The immunomodulation capacity and tumor-targeting features of MSCs made their use crucial for cell-based therapies in cancer treatment, yet limited advancement could be observed in translational medicine prospects due to the need for more information regarding the controversial roles of MSCs in crosstalk tumors. In this review, we discuss the therapeutic potential of MSCs, the controversial roles played by MSCs in cancer progression, and the anticancer therapeutic strategies that are in association with MSCs. Finally, the clinical trials designed for the direct use of MSCs for cancer therapy or for their use in decreasing the side effects of other cancer therapies are also mentioned in this review to evaluate the current status of MSC-based cancer therapies.

Mesenchymal stromal cells as cancer promoters

Mesenchymal stromal cells (MSCs) are important cellular constituents of tumor stroma that play an active role in tumor development. Complex interactions between MSCs and cancer promote tumor progression by creating a favorable milieu for tumor cell proliferation, angiogenesis, motility, invasion, and metastasis. The cellular heterogeneity, source of origin, diversity in isolation methods, culture techniques and model systems of MSCs, together with the different tumor subtypes, add to the complexity of MSC-tumor interactions. In this review, we discuss the mechanisms of MSC-mediated tumor promotion and evaluate cell-stromal interactions between cancer cells, MSCs, cells of the tumor microenvironment (TME), and the extracellular matrix (ECM). A more thorough understanding of tumor-MSC interactions is likely to lead to better cancer management.

Syngeneic mesenchymal stem cells loaded with telomerase-dependent oncolytic adenoviruses enhance anti-metastatic efficacy

Oncolytic adenoviruses have emerged as a promising therapeutic approach for cancer therapy. However, systemic delivery of the viruses to metastatic tumors remains a major challenge. Mesenchymal stem cells (MSCs) possess tumor tropism property and can be used as cellular vehicles for delivering oncolytic adenoviruses to tumor sites. Since telomerase activity is found in ~90% of human carcinomas, but undetected in normal adult cells, the human telomerase reverse transcriptase gene (TERT) promoter can be exploited for regulating the replication of oncolytic adenoviruses. Here, we evaluated the antitumor effects of syngeneic murine MSCs loaded with the luciferase-expressing, telomerase-dependent oncolytic adenovirus Ad.GS2 (MSC-Ad.GS2) and Ad.GS2 alone on metastatic MBT-2 bladder tumors. MSCs supported a low degree of Ad.GS2 replication, which could be augmented by coculture with MBT-2 cells or tumor-conditioned medium (TCM), suggesting that viral replication is increased when MSC-Ad.GS2 migrates to tumor sites. MBT-2 cells and TCM enhanced viral replication in Ad.GS2-infected MSCs. SDF-1 is a stem cell homing factor. Our results suggest that the SDF-1/STAT3/TERT signaling axis in MSCs in response to the tumor microenvironment may contribute to the enhanced replication of Ad.GS2 carried by MSCs. Notably, we demonstrate the potent therapeutic efficacy of systemically delivered MSC-Ad.GS2 in pleural disseminated tumor and experimental metastasis models using intrapleural and tail vein injection of MBT-2 cells, respectively. Treatment with MSC-Ad.GS2 significantly reduced tumor growth and prolonged the survival of mice bearing metastatic bladder tumors. Since telomerase is expressed in a broad spectrum of cancers, this therapeutic strategy may be broadly applicable.

Human umbilical cord blood mononuclear cells ameliorate ischemic brain injury via promoting microglia/macrophages M2 polarization in MCAO Rats

Cerebral infarction is one of the most prevalent cerebrovascular disorders. Microglia and infiltrating macrophages play a key role in regulating the inflammatory response after ischemic stroke. Regulation of microglia/macrophages polarization contributes to the recovery of neurological function in cerebral infarction. In recent decades, human umbilical cord blood mononuclear cells (hUCBMNCs) have been considered a potential therapeutic alternative. However, the mechanism of action is yet unclear. Our study aimed to explore whether hUCBMNCs treatment for cerebral infarction is via regulation of microglia/macrophages polarization. Adult male Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO) and were treated by intravenous routine with or without hUCBMNCs at 24 h following MCAO. We evaluated the therapeutic effects of hUCBMNCs on cerebral infarction by measuring animal behavior and infarct volume, and further explored the possible mechanisms of hUCBMNCs for cerebral infarction by measuring inflammatory factors and microglia/macrophages markers using Elisa and immunofluorescence staining, respectively. We found that administration with hUCBMNCs improved behavioral functions and reduced infarct volume. Rats treated with hUCBMNCs showed a significant reduction in the level of IL-6, and TNF-α and increased the level of IL-4 and IL-10 compared to those treated without hUCBMNCs. Furthermore, hUCBMNCs inhibited M1 polarization and promoted M2 polarization of microglia/macrophages after MCAO. We conclude that hUCBMNCs could ameliorate cerebral brain injury by promoting microglia/macrophages M2 polarization in MCAO Rats. This experiment provides evidence that hUCBMNCs represent a promising therapeutic option for ischemic stroke.

The effects of mesenchymal stem cells on the chemotherapy of colorectal cancer

Colorectal cancer (CRC) has been the third commonest cancer in the world. The prognosis of patients with CRC is related to the molecular subtypes and gene mutations, which is prone to recurrence, metastasis, and drug resistance. Mesenchymal stem cells (MSCs) are a group of progenitor ones with the capabilities of self-renewal， multi-directional differentiation, and tissue re-population, which could be isolated from various kinds of tissues and be differentiated into diverse cell types. In recent years, MSCs are applied for mechanisms study of tissue repairing, graft-versus-host disease (GVHD) and autoimmune-related disease, and tumor development, with the advantages of anti-inflammation, multi-lineage differentiation, and homing capability. Integrating the chemotherapy and MSCs therapy might provide a novel treatment approach for CRC patients. In this review, we summarize the current progress in the integrated treatment of integrating the MSCs and chemotherapy for CRC.

Active Hydrophilic Graphene Oxide Nanocomposites Delivery Mediated by Adipose-Derived Stem Cell for Elevated Photothermal Therapy of Breast Cancer

Purpose

Graphene oxide (GO) and its derivatives have recently been identified as promising candidates for early disease diagnosis and therapy. However, the physiological stability and precise launch requirements present limitations on further clinical practices. Adipose-derived stem cells (ADSCs) were employed as an unobstructed biological vehicle to address the validate this ADSC-based tumor-targeting system for highly efficient GO delivery combined with two-stage NIR radiation for superior tumor ablation.

Methods

GO was modified with poly-ethylene glycol (PEG) and folic acid (FA). Afterward, the GO nanocomposite was internalized into ADSCs. The GO-PEG-FA-laden ADSCs were injected into the tail veins of the tumor-bearing mice. Subsequently, first-stage NIR radiation was utilized to disrupt the ADSCs for GO-PEG-FA release. After this, the heat generated by secondary-stage NIR radiation destroy the malignant cells and shrink the tumor, and the cascade process could be recycled until complete tumor ablation if necessary.

Results

The GO-PEG-FA nanocomposite exhibited negligible cytotoxicity and could be internalized into ADSCs to target specific tumor sites after 32 days of intravenous injection. The nanocomposite was released from the ADSCs and taken up into cancer cells again with the assistance of FA after the first dose of near-infrared radiation. Then, the second radiation dose could directly strike the cancer cell for cancer ablation.

Conclusion

In summary, we reported a stem cell-based anticancer system that used GO-PEG-FA-laden ADSCs for breast cancer therapy through NIR treatment in mice potentially opens a new avenue not only to address precise drug targeting in tumor therapy, but also future clinical practice in diverse areas.

Ferroptosis Inducers Kill Mesenchymal Stem Cells Affected by Neuroblastoma

Bone marrow (BM) is the most common site of neuroblastoma (NB) metastasis, and its involvement represents poor patient prognosis. In accordance with the "seed and soil" theory of tumor metastasis, BM provides a favorable environment for NB metastasis while bone marrow mesenchymal stem cells (BMSCs) have been recognized as a central part of tumor stroma formation. Yet, there is currently no effective method for intervening these BMSCs. We found that BMSCs affected by NB (NB-BMSCs) could significantly promote NB growth and migration. Additionally, tumor cell-endowed BMSCs showed stronger resistance to several chemotherapeutic agents. Surprisingly, NB-BMSCs were more sensitive to ferroptosis than normal BMSCs. NB-BMSCs had lower levels of intracellular free iron while synthesizing more iron-sulfur clusters and heme. Moreover, the Xc^-/glutathione/glutathione peroxidase 4 (Xc^-/GSH/GPX4) pathway of the anti-ferroptosis system was significantly downregulated. Accordingly, ferroptosis inducers erastin and RAS-selective lethal 3 (RSL3) could significantly kill NB-BMSCs with limited effects on normal BMSCs. BMSCs from NB patients with BM metastasis also showed poor anti-ferroptosis ability compared with those from NB patients without BM metastasis. In vivo studies suggested that co-injection of mice with BMSCs and NB cells could significantly promote the growth of tumor tissues compared with injecting NB cells alone. However, treatment with erastin or RSL3 resulted in the opposite effect to some extent. Our results revealed that NB-BMSCs were vulnerable to ferroptosis from downregulation of the Xc^-/GSH/GPX4 pathway. Ferroptosis inducers could effectively kill NB-BMSCs, but not normal BMSCs. This study provides possible new ideas for the treatment of tumor-associated BMSCs in NB patients.

The Role of Mesenchymal Stem Cells and Exosomes in Tumor Development and Targeted Antitumor Therapies

Mesenchymal stem cells (MSCs) can be isolated from various tissues in adults and differentiated into cells of the osteoblasts, adipocytes, chondrocytes, and myocytes. Recruitments of MSCs towards tumors have a crucial contribution to tumor development. However, the role of MSCs in the tumor microenvironment is uncertain. In addition, due to its tropism to the tumor and low immunogenic properties, more and more pieces of evidence indicate that MSCs may be an ideal carrier for antitumor biologics such as cytokines, chemotherapeutic agents, and oncolytic viruses. Here, we review the existing knowledge on the anti- and protumorigenic effect of MSCs and their extracellular vesicles and exosomes, the role of MSCs, and their extracellular vesicles and exosomes as antitumor vectors.

Stem Cells for Cancer Therapy: Translating the Uncertainties and Possibilities of Stem Cell Properties into Opportunities for Effective Cancer Therapy

Cancer recurrence and drug resistance following treatment, as well as metastatic forms of cancer, are trends that are commonly encountered in cancer management. Amidst the growing popularity of personalized medicine and targeted therapy as effective cancer treatment, studies involving the use of stem cells in cancer therapy are gaining ground as promising translational treatment options that are actively pursued by researchers due to their unique tumor-homing activities and anti-cancer properties. Therefore, this review will highlight cancer interactions with commonly studied stem cell types, namely, mesenchymal stroma/stem cells (MSC), induced pluripotent stem cells (iPSC), iPSC-derived MSC (iMSC), and cancer stem cells (CSC). A particular focus will be on the effects of paracrine signaling activities and exosomal miRNA interaction released by MSC and iMSCs within the tumor microenvironment (TME) along with their therapeutic potential as anti-cancer delivery agents. Similarly, the role of exosomal miRNA released by CSCs will be further discussed in the context of its role in cancer recurrence and metastatic spread, which leads to a better understanding of how such exosomal miRNA could be used as potential forms of non-cell-based cancer therapy.

Visualizing Activated Myofibroblasts Resulting from Differentiation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are multipotent cells that exhibit two main characteristics which define stem cells: self-renewal and differentiation. MSCs can migrate to sites of injury, inflammation, and tumor. Moreover, MSCs undergo myofibroblast-like differentiation, including increased production of α-SMA in response to transforming growth factor-β (TGF-β), a growth factor commonly secreted by tumor cells to evade immune surveillance. Based on our previous findings, hMSCs become activated and resemble carcinoma-associated myofibroblasts upon prolonged exposure to a conditioned medium from MDAMB231 human breast cancer cells. In this section, we show using immunofluorescence that keratinocyte-conditioned medium (KCM) induces differentiation of MSCs to resemble dermal myofibroblast-like cells with punctate vinculin staining and F-actin filaments.

Immunotherapy by mesenchymal stromal cell delivery of oncolytic viruses for treating metastatic tumors

Oncolytic viruses (OVs) have emerged as a very promising anti-cancer therapeutic strategy in the past decades. However, despite their pre-clinical promise, many OV clinical evaluations for cancer therapy have highlighted the continued need for their improved delivery and targeting. Mesenchymal stromal cells (MSCs) have emerged as excellent candidate vehicles for the delivery of OVs due to their tumor-homing properties and low immunogenicity. MSCs can enhance OV delivery by protecting viruses from rapid clearance following administration and also by more efficiently targeting tumor sites, consequently augmenting the therapeutic potential of OVs. MSCs can function as “biological factories,” enabling OV amplification within these cells to promote tumor lysis following MSC-OV arrival at the tumor site. MSC-OVs can promote enhanced safety profiles and therapeutic effects relative to OVs alone. In this review we explore the general characteristics of MSCs as delivery tools for cancer therapeutic agents. Furthermore, we discuss the potential of OVs as immune therapeutics and highlight some of the promising applications stemming from combining MSCs to achieve enhanced delivery and anti-tumor effectiveness of OVs at different pre-clinical and clinical stages. We further provide potential pitfalls of the MSC-OV platform and the strategies under development for enhancing the efficacy of these emerging therapeutics.

Metabolic Interactions Between Tumor and Stromal Cells in the Tumor Microenvironment

In this chapter, we provide information about metabolic reprogramming in cancer cells, molecular interactions between tumor and stromal cells in the tumor microenvironment, focusing primarily on CAFs and tumor cell interaction. We have covered the role of cytokines, chemokines, and lactate in driving tumor-stroma interactions in the microenvironment. Here, we have discussed the pro-tumorigenic molecular interactions in between tumor cells and CAFs mediated via altered signaling pathways, cytokines, chemokines, and lactate in the tumor vicinity. A better understanding of the complex cancer cell-CAF interactions will help in designing successful therapeutic strategies targeting the stromal-rich tumors in the clinic.

The Extracellular Matrix in Pancreatic Cancer: Description of a Complex Network and Promising Therapeutic Options

The stroma is a relevant player in driving and supporting the progression of pancreatic ductal adenocarcinoma (PDAC), and a large body of evidence highlights its role in hindering the efficacy of current therapies. In fact, the dense extracellular matrix (ECM) characterizing this tumor acts as a natural physical barrier, impairing drug penetration. Consequently, all of the approaches combining stroma-targeting and anticancer therapy constitute an appealing option for improving drug penetration. Several strategies have been adopted in order to target the PDAC stroma, such as the depletion of ECM components and the targeting of cancer-associated fibroblasts (CAFs), which are responsible for the increased matrix deposition in cancer. Additionally, the leaky and collapsing blood vessels characterizing the tumor might be normalized, thus restoring blood perfusion and allowing drug penetration. Even though many stroma-targeting strategies have reported disappointing results in clinical trials, the ECM offers a wide range of potential therapeutic targets that are now being investigated. The dense ECM might be bypassed by implementing nanoparticle-based systems or by using mesenchymal stem cells as drug carriers. The present review aims to provide an overview of the principal mechanisms involved in the ECM remodeling and of new promising therapeutic strategies for PDAC.

Safety and Homing of Human Dental Pulp Stromal Cells in Head and Neck Cancer

BACKGROUND

Head and neck cancer (HNC) is one of the most common cancers, associated with a huge mortality and morbidity. In order to improve patient outcomes, more efficient and targeted therapies are essential. Bone marrow-derived mesenchymal stromal cells (BM-MSCs) express tumour homing capacity, which could be exploited to target anti-cancer drug delivery to the tumour region and reduce adverse side-effects. Nevertheless, dental pulp stromal cells (DPSCs), an MSC-like population present in teeth, could offer important clinical benefits because of their easy isolation and superior proliferation compared to BM-MSCs. Therefore, we aimed to elucidate the tumour homing and safe usage of DPSCs to treat HNC.

METHODS

The in vivo survival as well as the effect of intratumourally administered DPSCs on tumour aggressiveness was tested in a HNC xenograft mouse model by using bioluminescence imaging (BLI), (immuno)histology and qRT-PCR. Furthermore, the in vitro and in vivo tumour homing capacity of DPSCs towards a HNC cell line were evaluated by a transwell migration assay and BLI, respectively.

RESULTS

Intratumourally injected DPSCs survived for at least two weeks in the tumour micro-environment and had no significant influence on tumour morphology, growth, angiogenesis and epithelial-to-mesenchymal transition. In addition, DPSCs migrated towards tumour cells in vitro, which could not be confirmed after their in vivo intravenous, intraperitoneal or peritumoural injection under the tested experimental conditions.

CONCLUSIONS

Our research suggests that intratumourally delivered DPSCs might be used as safe factories for the continuous delivery of anti-cancer drugs in HNC. Nevertheless, further optimization as well as efficacy studies are necessary to understand and improve in vivo tumour homing and determine the optimal experimental set-up of stem cell-based cancer therapies, including dosing and timing.

Neural Stem Cell-Based Therapies and Glioblastoma Management: Current Evidence and Clinical Challenges

Gliomas, which account for nearly a quarter of all primary CNS tumors, present significant contemporary therapeutic challenges, particularly the highest-grade variant (glioblastoma multiforme), which has an especially poor prognosis. These difficulties are due to the tumor's aggressiveness and the adverse effects of radio/chemotherapy on the brain. Stem cell therapy is an exciting area of research being explored for several medical issues. Neural stem cells, normally present in the subventricular zone and the hippocampus, preferentially migrate to tumor masses. Thus, they have two main advantages: They can minimize the side effects associated with systemic radio/chemotherapy while simultaneously maximizing drug delivery to the tumor site. Another feature of stem cell therapy is the variety of treatment approaches it allows. Stem cells can be genetically engineered into expressing a wide variety of immunomodulatory substances that can inhibit tumor growth. They can also be used as delivery vehicles for oncolytic viral vectors, which can then be used to combat the tumorous mass. An alternative approach would be to combine stem cells with prodrugs, which can subsequently convert them into the active form upon migration to the tumor mass. As with any therapeutic modality still in its infancy, much of the research regarding their use is primarily based upon knowledge gained from animal studies, and a number of ongoing clinical trials are currently investigating their effectiveness in humans. The aim of this review is to highlight the current state of stem cell therapy in the treatment of gliomas, exploring the different mechanistic approaches, clinical applicability, and the existing limitations.

Combination treatment with VPA and MSCs‑TRAIL could increase anti‑tumor effects against intracranial glioma

Human bone marrow-derived mesenchymal stem cells secreting tumor necrosis factor-related apoptosis-inducing ligand (MSCs-TRAIL) have demonstrated effective anti-tumor activity against various tumors including lung, pancreatic and prostate tumors, although several tumor types are not responsive. In such case, other reagents may decrease tumor growth via TRAIL-mediated cell death. The present study aimed to examine the effectiveness of valproic acid (VPA) in enhancing the efficacy of TRAIL, which was delivered using MSCs. Moreover, the present study examined the induced tumor tropism of MSCs via cell viability and migration assays. Combination treatment with VPA and MSCs-TRAIL enhanced the glioma therapeutic effect by increasing death receptor 5 and caspase activation. Migration assays identified increased MSC migration in VPA and MSCs-TRAIL-treated glioma cells and in the tumor site in glioma-bearing mice compared with VPA or MSC-TRAIL treatment alone. In vivo experiments demonstrated that MSC-based TRAIL gene delivery to VPA-treated tumors had greater therapeutic efficacy compared with treatment with each agent alone. These findings suggested that VPA treatment increased the therapeutic efficacy of MSC-TRAIL via TRAIL-induced apoptosis and enhanced tropism of MSCs, which may offer a useful strategy for tumor gene therapy.

KSHV enhances mesenchymal stem cell homing and promotes KS-like pathogenesis

Kaposi's sarcoma (KS) tends to occur in injured or inflamed sites of the body, which is described as the "Koebner phenomenon". KS is also unique in its extraordinary angio-hyperplastic inflammatory phenotype. Recently, evidence has accrued indicating that KS may derive from KSHV-infected mesenchymal stem cells (MSCs), which possess enhanced migration and homing ability. Inspired by these findings, we hypothesized that KS may arise from KSHV-infected MSCs that chemotactically migrate to preexisting inflammatory or injured sites. Here we report that KSHV infection of human MSCs significantly up-regulated expression of several chemokine receptors and enhanced cell migration ability in vitro. Furthermore, using a wound mouse model, we demonstrated that KSHV infection dramatically promotes MSCs migrating and settling in the wound sites. In addition, two mice in the KSHV-infected group showed purpura and tumors with KS-like features. Taken together, KSHV-enhanced MSC migration ability and inflammatory microenvironment play crucial roles in KS development.

Past, Present, and Future of Anticancer Nanomedicine

This review aims to summarize the methods that have been used till today, highlight methods that are currently being developed, and predict the future roadmap for anticancer therapy. In the beginning of this review, established approaches for anticancer therapy, such as conventional chemotherapy, hormonal therapy, monoclonal antibodies, and tyrosine kinase inhibitors are summarized. To counteract the side effects of conventional chemotherapy and to increase limited anticancer efficacy, nanodrug- and stem cell-based therapies have been introduced. However, current level of understanding and strategies of nanodrug and stem cell-based therapies have limitations that make them inadequate for clinical application. Subsequently, this manuscript reviews methods with fewer side effects compared to those of the methods mentioned above which are currently being investigated and are already being applied in the clinic. The newer strategies that are already being clinically applied include cancer immunotherapy, especially T cell-mediated therapy and immune checkpoint inhibitors, and strategies that are gaining attention include the manipulation of the tumor microenvironment or the activation of dendritic cells. Tumor-associated macrophage repolarization is another potential strategy for cancer immunotherapy, a method which activates macrophages to immunologically attack malignant cells. At the end of this review, we discuss combination therapies, which are the future of cancer treatment. Nanoparticle-based anticancer immunotherapies seem to be effective, in that they effectively use nanodrugs to elicit a greater immune response. The combination of these therapies with others, such as photothermal or tumor vaccine therapy, can result in a greater anticancer effect. Thus, the future of anticancer therapy aims to increase the effectiveness of therapy using various therapies in a synergistic combination rather than individually.

Nicotine does not affect stem cell properties requisite for suicide gene therapy against glioma

OBJECTIVE: 

Glioblastoma is one of the most lethal tumors in adult central nervous system with a median survival of a year and half and effective therapeutic strategy is urgently needed. For that reason, stem cell-based suicide gene therapies have attracted much interest because of potent tumor tropism of stem cells and bystander effect. In this current clinical situation, stem cells are promising delivery tool of suicide genes for glioma therapy. Since habitual cigarette smoking still prevails worldwide, we investigated the effect of nicotine on stem cell tropism toward glioma and gap junctional intercellular communication (GJIC) function between glioma and stem cells, both of which are important for suicide gene therapies. Methods: Mouse induced pluripotent stem cell-derived neural stem cells (iPS-NSCs) and human dental pulp mesenchymal stem cells (DPSCs) were used. The effect of nicotine on tumor tropism to glioma-conditioned medium (CM) at a non-cytotoxic concentration was assessed with Matrigel invasion assay. Nicotine effect on GJIC was assessed with the scrape loading/dye transfer (SL/DT) assay for co-culture of glioma and stem cells and the parachute assay among glioma cells using high-content analysis. Results: Tumor tropism of iPS-NSCs toward GL261-CM and DPSCs toward U251-CM was not affected by nicotine (0.1 and 1 µM). Nicotine at the concentrations equivalent to habitual smoking (1 µM) did not affect GJIC of iPS-NSC/GL261 and DPSC/U251 and GJIC among each glioma cells. Conclusions: The study demonstrated that non-cytotoxic concentrations of nicotine did not significantly change the stem cell properties requisite for stem cell-based suicide gene therapy.

The Endosteal Niche in Breast Cancer Bone Metastasis

The establishment of bone metastasis remains one of the most frequent complications of patients suffering from advanced breast cancer. Patients with bone metastases experience high morbidity and mortality caused by excessive, tumor-induced and osteoclast-mediated bone resorption. Anti-resorptive treatments, such as bisphosphonates, are available to ease skeletal related events including pain, increased fracture risk, and hypercalcemia. However, the disease remains incurable and 5-year survival rates for these patients are below 25%. Within the bone, disseminated breast cancer cells localize in “metastatic niches,” special microenvironments that are thought to regulate cancer cell colonization and dormancy as well as tumor progression and subsequent development into overt metastases. Precise location and composition of this “metastatic niche” remain poorly defined. However, it is thought to include an “endosteal niche” that is composed of key bone cells that are derived from both, hematopoietic stem cells (osteoclasts), and mesenchymal stromal cells (osteoblasts, fibroblasts, adipocytes). Our knowledge of how osteoclasts drive the late stage of the disease is well-established. In contrast, much less is known about the interaction between osteogenic cells and disseminated tumor cells prior to the initiation of the osteolytic phase. Recent studies suggest that mesenchymal-derived cells, including osteoblasts and fibroblasts, play a key role during the early stages of breast cancer bone metastasis such as tumor cell homing, bone marrow colonization, and tumor cell dormancy. Hence, elucidating the interactions between breast cancer cells and mesenchymal-derived cells that drive metastasis progression could provide novel therapeutic approaches and targets to treat breast cancer bone metastasis. In this review we discuss evidences reporting the interaction between tumor cells and endosteal niche cells during the early stages of breast cancer bone metastasis, with a particular focus on mesenchymal-derived osteoblasts and fibroblasts.

Pathological Crosstalk between Metastatic Breast Cancer Cells and the Bone Microenvironment

Bone is the most common metastatic site in breast cancer. Upon arrival to the bone, disseminated tumor cells can undergo a period of dormancy but often eventually grow and hijack the bone microenvironment. The bone marrow microenvironment consists of multiple cell types including the bone cells, adipocytes, endothelial cells, and nerve cells that all have crucial functions in the maintenance of bone homeostasis. Tumor cells severely disturb the tightly controlled cellular and molecular interactions in the bone marrow fueling their own survival and growth. While the role of bone resorbing osteoclasts in breast cancer bone metastases is well established, the function of other bone cells, as well as adipocytes, endothelial cells, and nerve cells is less understood. In this review, we discuss the composition of the physiological bone microenvironment and how the presence of tumor cells influences the microenvironment, creating a pathological crosstalk between the cells. A better understanding of the cellular and molecular events that occur in the metastatic bone microenvironment could facilitate the identification of novel cellular targets to treat this devastating disease.

Cell-Based Nanoparticles Delivery Systems for Targeted Cancer Therapy: Lessons from Anti-Angiogenesis Treatments

The main strategy of cancer treatment has focused on attacking the tumor cells. Some cancers initially responsive to chemotherapy become treatment-resistant. Another strategy is to block the formation of tumor vessels. However, tumors also become resistant to anti-angiogenic treatments, mostly due to other cells and factors present in the tumor microenvironment, and hypoxia in the central part of the tumor. The need for new cancer therapies is significant. The use of nanoparticle-based therapy will improve therapeutic efficacy and targeting, while reducing toxicity. However, due to inefficient accumulation in tumor sites, clearance by reticuloendothelial organs and toxicity, internalization or conjugation of drug-loaded nanoparticles (NPs) into mesenchymal stem cells (MSCs) can increase efficacy by actively delivering them into the tumor microenvironment. Nanoengineering MSCs with drug-loaded NPs can increase the drug payload delivered to tumor sites due to the migratory and homing abilities of MSCs. However, MSCs have some disadvantages, and exosomes and membranes from different cell types can be used to transport drug-loaded NPs actively to tumors. This review gives an overview of different cancer approaches, with a focus on hypoxia and the emergence of NPs as drug-delivery systems and MSCs as cellular vehicles for targeted delivery due to their tumor-homing potential.

Biointerface engineering nanoplatforms for cancer-targeted drug delivery

Over the past decade, nanoparticle-based therapeutic modalities have become promising strategies in cancer therapy. Selective delivery of anticancer drugs to the lesion sites is critical for elimination of the tumor and an improved prognosis. Innovative design and advanced biointerface engineering have promoted the development of various nanocarriers for optimized drug delivery. Keeping in mind the biological framework of the tumor microenvironment, biomembrane-camouflaged nanoplatforms have been a research focus, reflecting their superiority in cancer targeting. In this review, we summarize the development of various biomimetic cell membrane-camouflaged nanoplatforms for cancer-targeted drug delivery, which are classified according to the membranes from different cells. The challenges and opportunities of the advanced biointerface engineering drug delivery nanosystems in cancer therapy are discussed.

Multiple Targets of the Canonical WNT/β-Catenin Signaling in Cancers

Canonical WNT/β-catenin signaling is involved in most of the mechanisms that lead to the formation and development of cancer cells. It plays a central role in three cyclic processes, which are the cell division cycle, the immune cycle, and circadian rhythms. When the canonical WNT pathway is upregulated as in cancers, the increase in β-catenin in the nucleus leads to activation of the expression of numerous genes, in particular CYCLIN D1 and cMYC, where the former influences the G1 phase of the cell division cycle, and the latter, the S phase. Every stage of the immune cycle is disrupted by the canonical WNT signaling. In numerous cancers, the dysfunction of the canonical WNT pathway is accompanied by alterations of the circadian genes (CLOCK, BMAL1, PER). Induction of these cyclic phenomena leads to the genesis of thermodynamic mechanisms that operate far from equilibrium, and that have been called “dissipative structures.” Moreover, upregulation of the canonical WNT/β-catenin signaling is important in the myofibroblasts of the cancer stroma. Their differentiation is controlled by the canonical WNT /TGF-β1 signaling. Myofibroblasts present ultraslow contractile properties due to the presence of the non-muscle myosin IIA. Myofibroblats also play a role in the inflammatory processes, often found in cancers and fibrosis processes. Finally, upregulated canonical WNT deviates mitochondrial oxidative phosphorylation toward the Warburg glycolysis metabolism, which is characteristic of cancers. Among all these cancer-generating mechanisms, the upregulated canonical WNT pathway would appear to offer the best hope as a therapeutic target, particularly in the field of immunotherapy.

The multifaceted role of mesenchymal stem cells in cancer

Mesenchymal stem cells (MSCs) are multipotent stem cells derived from the mesoderm that give rise to several mesenchymal lineages, including osteoblasts, adipocytes, chondrocytes and myocytes. Their potent ability to home to tumors coupled with their differentiation potential and immunosuppressive function positions MSCs as key regulators of tumor fate. Here we review the existing knowledge on the involvement of MSCs in multiple tumor-promoting processes, including angiogenesis, epithelial-mesenchymal transition, metastasis, immunosuppression and therapy resistance. We also discuss the clinical potential of MSC-based therapy for cancer.

Adipose-Derived Stromal Vascular Fraction and Cultured Stromal Cells as Trophic Mediators for Tendon Healing

Adipose-derived stromal vascular fraction (SVF) is a heterogeneous population of cells that yields a homogeneous population of plastic-adherent adipose tissue-derived stromal cells (ASC) when culture-expanded. SVF and ASC have been used clinically to improve tendon healing, yet their mechanism of action is not fully elucidated. The objective of this study was to investigate the potential for ASC to act as trophic mediators for tendon healing. Flexor digitorum superficialis tendons and adipose tissue were harvested from adult horses to obtain SVF, ASC, and tenocytes. Growth factor gene expression was quantified in SVF and ASC in serial passages and growth factors were quantified in ASC-conditioned medium (CM). Microchemotaxis assays were performed using ASC-CM. Tenocytes were grown in co-culture with autologous ASC or allogeneic SVF. Gene expression for insulin-like growth factor 1 (IGF-1), stromal cell-derived factor-1α (SDF-1α), transforming growth factor-β1 (TGF-β1) and TGF-β3 was significantly higher in SVF compared to ASC. Concentrations were significantly increased in ASC-CM compared to controls for IGF-1 (4-fold) and SDF-1α (6-fold). Medium conditioned by ASC induced significant cell migration in a dose-dependent manner. Gene expression for collagen types I and III, decorin, and cartilage oligomeric matrix protein was modestly, but significantly increased following co-culture of tenocytes with autologous ASC. Our findings support the ability of SVF and ASC to act as trophic mediators in tendon healing, particularly through chemotaxis, which stands to critically impact the intrinsic healing response. In vivo studies to further delineate the potential for SVF and/or ASC to improve tendon healing are warranted. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1429-1439, 2019.

Mesenchymal stem cells: From regeneration to cancer

Mesenchymal stem cells (MSCs) are multipotent tissue stem cells that differentiate into a number of mesodermal tissue types, including osteoblasts, adipocytes, chondrocytes and myofibroblasts. MSCs were originally identified in the bone marrow (BM) of humans and other mammals, but recent studies have shown that they are multilineage progenitors in various adult organs and tissues. MSCs that localize at perivascular sites function to rapidly respond to external stimuli and coordinate with the vascular and immune systems to accomplish the wound healing process. Cancer, considered as wounds that never heal, is also accompanied by changes in MSCs that parallels the wound healing response. MSCs are now recognized as key players at distinct steps of tumorigenesis. In this review, we provide an overview of the function of MSCs in wound healing and cancer progression with the goal of providing insight into the development of novel MSC-manipulating strategies for clinical cancer treatment.

Mesenchymal stem cell therapies in brain disease

As treatments for diseases throughout the body progress, treatment for many brain diseases has been at a standstill due to difficulties in drug delivery. While new drugs are being discovered in vitro, these therapies are often hindered by inefficient tissue distribution and, more commonly, an inability to cross the blood brain barrier. Mesenchymal stem cells are thus being investigated as a delivery tool to directly target therapies to the brain to treat wide array of brain diseases. This review discusses the use of mesenchymal stem cells in hypoxic disease (hypoxic ischemic encephalopathy), an inflammatory neurodegenerative disease (multiple sclerosis), and a malignant condition (glioma).

Human Bone Marrow Mesenchymal Stem Cells Functionalized by Hybrid Baculovirus-Adeno-Associated Viral Vectors for Targeting Hypopharyngeal Carcinoma

Hypopharyngeal carcinoma is a common malignant tumor of the head and neck with a very poor prognosis; the median survival time for curatively treated patients was 17.2 months in India. However, cell-based gene therapy holds promise to improve patient outcomes. In this study, we investigated whether human bone marrow mesenchymal stem cells (BMSCs) possess potential homing capacity for hypopharyngeal carcinoma. To monitor the efficiency of BMSC transplantation therapy through reporter gene imaging, we employed a hybrid baculovirus vector containing the Luc-P2A-eGFP fusion or sodium iodide symporter (NIS) sequence under the control of the cytomegalovirus promoter. To enhance the transfection efficiency, baculovirus vectors (Bac-CMV-Luc-P2A-eGFP-ITR and Bac-CMV-NIS-ITR) were flanked by inverted terminal repeats (ITRs), which are key elements of adeno-associated viruses. The infection efficiency of Bac-CMV-Luc-P2A-eGFP-ITR in BMSCs was as high as 92.84 ± 1.14% with no obvious toxic effects at a multiplicity of infection of 400. Moreover, Bac-CMV-NIS-ITR-infected BMSCs showed highly efficient radioactive iodide (¹²⁵I) uptake; these high uptake levels were maintained for at least 2 h. Transwell migration assays further demonstrated the chemotaxis of BMSCs to hypopharyngeal carcinoma cells (FaDu cells) in vitro. BMSCs modified by firefly luciferase report gene or NIS were injected into nude mice with hypopharyngeal carcinoma, and changes in the localization of the BMSCs were successfully tracked with bioluminescent imaging and micro-single-photon emission computed tomography imaging. These data indicate the potential utility of BMSCs as a promising targeted-delivery vehicle for hypopharyngeal carcinoma gene therapy. Importantly, BMSCs may represent a promising targeting vector for general tumor radionuclide therapy.

Adipose‑derived mesenchymal stem cells exhibit tumor tropism and promote tumorsphere formation of breast cancer cells

Mesenchymal stem cells reportedly have a marked effect on tumor growth or suppression. However, it remains uncertain whether adipose-derived mesenchymal stem cells (ADSCs) from grafted fat can contribute to breast cancer growth and recurrence. In the present study, interactions between ADSCs and MCF-7 breast cancer cells were evaluated in a Matrigel co-culture system and in an in vivo nude mouse model. Results suggested that MCF-7 cells exerted tumor tropism effects on ADSCs and this may be regulated by chemokines, such as the macrophage inflammatory protein (MIP)-1δ and MIP-3α. Additionally, ADSCs significantly induced tumorsphere formation in vitro and promoted tumorigenicity in vivo. RT-qPCR analysis indicated that tumorsphere formation by MCF-7 cells was associated with the induction of stem-like properties, which was mediated by epithelial-mesenchymal transition. Together, the present findings indicated that ADSCs exhibit tropism and induce tumorsphere formation of MCF-7 cells.

Enhancer Domains in Gastrointestinal Stromal Tumor Regulate KIT Expression and Are Targetable by BET Bromodomain Inhibition

Gastrointestinal stromal tumor (GIST) is a mesenchymal neoplasm characterized by activating mutations in the related receptor tyrosine kinases KIT and PDGFRA. GIST relies on expression of these unamplified receptor tyrosine kinase (RTK) genes through a large enhancer domain, resulting in high expression levels of the oncogene required for tumor growth. Although kinase inhibition is an effective therapy for many patients with GIST, disease progression from kinase-resistant mutations is common and no other effective classes of systemic therapy exist. In this study, we identify regulatory regions of the KIT enhancer essential for KIT gene expression and GIST cell viability. Given the dependence of GIST upon enhancer-driven expression of RTKs, we hypothesized that the enhancer domains could be therapeutically targeted by a BET bromodomain inhibitor (BBI). Treatment of GIST cells with BBIs led to cell-cycle arrest, apoptosis, and cell death, with unique sensitivity in GIST cells arising from attenuation of the KIT enhancer domain and reduced KIT gene expression. BBI treatment in KIT-dependent GIST cells produced genome-wide changes in the H3K27ac enhancer landscape and gene expression program, which was also seen with direct KIT inhibition using a tyrosine kinase inhibitor (TKI). Combination treatment with BBI and TKI led to superior cytotoxic effects in vitro and in vivo, with BBI preventing tumor growth in TKI-resistant xenografts. Resistance to select BBI in GIST was attributable to drug efflux pumps. These results define a therapeutic vulnerability and clinical strategy for targeting oncogenic kinase dependency in GIST. SIGNIFICANCE: Expression and activity of mutant KIT is essential for driving the majority of GIST neoplasms, which can be therapeutically targeted using BET bromodomain inhibitors.

Mesenchymal stem cells in preclinical cancer cytotherapy: a systematic review

Mesenchymal stem cells (MSC) comprise a heterogeneous population of rapidly proliferating cells that can be isolated from adult (e.g., bone marrow, adipose tissue) as well as fetal (e.g., umbilical cord) tissues (termed bone marrow (BM)-, adipose tissue (AT)-, and umbilical cord (UC)-MSC, respectively) and are capable of differentiation into a wide range of non-hematopoietic cell types. An additional, unique attribute of MSC is their ability to home to tumor sites and to interact with the local supportive microenvironment which rapidly conceptualized into MSC-based experimental cancer cytotherapy at the turn of the century. Towards this purpose, both naïve (unmodified) and genetically modified MSC (GM-MSC; used as delivery vehicles for the controlled expression and release of antitumorigenic molecules) have been employed using well-established in vitro and in vivo cancer models, albeit with variable success. The first approach is hampered by contradictory findings regarding the effects of naïve MSC of different origins on tumor growth and metastasis, largely attributed to inherent biological heterogeneity of MSC as well as experimental discrepancies. In the second case, although the anti-cancer effect of GM-MSC is markedly improved over that of naïve cells, it is yet apparent that some protocols are more efficient against some types of cancer than others. Regardless, in order to maximize therapeutic consistency and efficacy, a deeper understanding of the complex interaction between MSC and the tumor microenvironment is required, as well as examination of the role of key experimental parameters in shaping the final cytotherapy outcome. This systematic review represents, to the best of our knowledge, the first thorough evaluation of the impact of experimental anti-cancer therapies based on MSC of human origin (with special focus on human BM-/AT-/UC-MSC). Importantly, we dissect the commonalities and differences as well as address the shortcomings of work accumulated over the last two decades and discuss how this information can serve as a guide map for optimal experimental design implementation ultimately aiding the effective transition into clinical trials.

Regulation of plasticity and biological features of endothelial progenitor cells by MSC-derived SDF-1

Bone marrow (BM) is a source of mesenchymal stromal cells (MSCs) and endothelial progenitor cells (EPCs). MSCs provide a specific niche in the BM and biological features of EPCs may be changed with this niche. Stromal cell-derived factor 1 (SDF-1) secreted from primary BM-MSCs and biological features of this niche on EPC development are still yet to be understood. The aim of this study was to evaluate the role of SDF-1 produced by MSCs on EPC development. We applied the CRISPR/Cas9 system for the knock-out of the SDF-1 gene in BM-derived MSCs. BM-derived EPCs were then cocultured with MSCs^SDF-1-/- or MSCs^SDF-1+/+ to identify the role of MSC-derived SDF-1α on proliferation, migration and angiogenic activity of EPCs. Next, pre-expanded EPCs were harvested and co-transplanted with MSCs^SDF-1-/- or MSCs^SDF-1+/+ into sublethally irradiated mice to analyze the potency of these cells for marrow reconstitution. Our results revealed that proliferation, colony formation, migration and angiogenic activity of EPCs was significantly increased after coculture with MSCs^SDF-1+/+. We also found that co-transplantation of EPCs with MSCs^SDF-1+/+, in contrast to MSCs^SDF-1-/-, into irradiated mice resulted in marrow repopulation and hematologic recovery, leading to improved survival of transplanted mice. In conclusions, MSC-derived SDF-1 niche plays an important role in the development of EPCs and this niche is essential for bone marrow repopulation by these cells and can enhance the efficiency of EPC therapy for ischemic diseases.

Tumor-Targeted Immunotherapy by Using Primary Adipose-Derived Stem Cells and an Antigen-Specific Protein Vaccine

Cancer is a leading cause of mortality and a major public health problem worldwide. For biological therapy against cancer, we previously developed a unique immunotherapeutic platform by combining mesenchymal stem cells with an antigen-specific protein vaccine. However, this system possesses a few limitations, such as improperly immortalized mesenchymal stem cells (MSCs) along with transfected oncogenic antigens in them. To overcome the limitations of this platform for future clinical application, we freshly prepared primary adipose-derived stem cells (ADSCs) and modified the E7' antigen (E7') as a non-oncogenic protein. Either subcutaneously co-inoculated with cancer cells or systemically administered after tumor growth, ADSC labeled with enhanced green fluorescent protein (eGFP) and combined with modified E7' (ADSC-E7'-eGFP) cells showed significant antitumor activity when combined with the protein vaccine in both colon and lung cancer in mice. Specifically, this combined therapy inhibited tumor through inducing cell apoptosis. The significantly reduced endothelial cell markers, CD31 and vascular endothelial growth factor (VEGF), indicated strongly inhibited tumor angiogenesis. The activated immune system was demonstrated through the response of CD4+ T and natural killer (NK) cells, and a notable antitumor activity might be contributed by CD8+ T cells. Conclusively, these evidences imply that this promising immunotherapeutic platform might be a potential candidate for the future clinical application against cancer.

The Dynamic Roles of Mesenchymal Stem Cells in Colon Cancer

Colon cancer is still one of the most common causes of cancer in human and is characterized by lymphocyte infiltrates and originates from the epithelial cells found in the lining of colon or rectum of the gastrointestinal tract. Mesenchymal stem cells (MSCs) are composed of the multipotent stem cell group of stroma and can be differentiated as various cell lineages, such as fibroblasts, osteoblasts, and adipocytes. MSCs provide mechanical and structural support and have potential functions during tumor growth and metastasis. The efficacy of MSC-based therapies is partly dependent on the migration and homing of MSCs to tumors and metastatic sites. However, their migratory and engraftment potential is poorly understood. In this review, the characteristics and mechanisms of MSC's dynamic interaction with colon cancer were summarized, particularly the potential functions of MSCs on colon cancer, including its role in improving tumor growth and as a potential candidate for tumor therapy. Understanding MSC homing provides new insights into the manipulation of MSC and the improvement of their efficacy for colon cancer therapy.

The Use of Normal Stem Cells and Cancer Stem Cells for Potential Anti-Cancer Therapeutic Strategy

BACKGROUND

Despite recent advance in conventional cancer therapies including surgery, radiotherapy, chemotherapy, and immunotherapy to reduce tumor size, unfortunately cancer mortality and metastatic cancer incidence remain high. Along with a deeper understanding of stem cell biology, cancer stem cell (CSC) is important in targeted cancer therapy. Herein, we review representative patents using not only normal stem cells as therapeutics themselves or delivery vehicles, but also CSCs as targets for anti-cancer strategy.

METHODS

Relevant patent literatures published between 2005 and 2017 are discussed to present developmental status and experimental results on using normal stem cells and CSCs for cancer therapy and explore potential future directions in this field.

RESULTS

Stem cells have been considered as important element of regenerative therapy by promoting tissue regeneration. Particularly, there is a growing trend to use stem cells as a target drug-delivery system to reduce undesirable side effects in non-target tissues. Noteworthy, studies on CSC-specific markers for distinguishing CSCs from normal stem cells and mature cancer cells have been conducted as a selective anti-cancer therapy with few side effects. Many researchers have also reported the development of various substances with anticancer effects by targeting CSCs from cancer tissues.

CONCLUSION

There has been a continuing increase in the number of studies on therapeutic stem cells and CSC-specific markers for selective diagnosis and therapy of cancer. This review focuses on the current status in the use of normal stem cells and CSCs for targeted cancer therapy. Future direction is also proposed.

Mutual Destruction of Deep Lung Tumor Tissues by Nanodrug-Conjugated Stealth Mesenchymal Stem Cells

Lung cancer is a highly malignant tumor, and targeted delivery of anti-cancer drugs to deep lung tumor tissue remains a challenge in drug design. Here, it is demonstrated that bone marrow mesenchymal stem cells armed with nanodrugs are highly targeted and mutually destructive with malignant lung cancer cells and successfully eradicate lung tumors tissues. Using this approach, the current clinical dose of anti-cancer drugs for the treatment of malignant lung tumors can be decreased by more than 100-fold without triggering immunotoxicity.

Enhanced tumor growth inhibition by mesenchymal stem cells derived from iPSCs with targeted integration of interleukin24 into rDNA loci

Induced pluripotent stem cells (iPSCs) are a promising source of mesenchymal stem cells (MSCs) for clinical applications. In this study, we transformed human iPSCs using a non-viral vector carrying the IL24 transgene pHrn-IL24. PCR and southern blotting confirmed IL24 integration into the rDNA loci in four of 68 iPSC clones. We then differentiated a high expressing IL24-iPSC clone into MSCs (IL24-iMSCs) that showed higher expression of IL24 in culture supernatants and in cell lysates than control iMSCs. IL24-iMSCs efficiently differentiated into osteoblasts, chondrocytes and adipocytes. Functionally, IL24-iMSCs induced in vitro apoptosis in B16-F10 melanoma cells more efficiently than control iMSCs when co-cultured in Transwell assays. In vivo tumor xenograft studies in mice demonstrated that IL24-iMSCs inhibited melanoma growth more than control iMSCs did. Immunofluorescence and histochemical analysis showed larger necrotic areas and cell nuclear aggregation in tumors with IL24-iMSCs than control iMSCs, indicating that IL24-iMSCs inhibited tumor growth by inducing apoptosis. These findings demonstrate efficient transformation of iPSCs through gene targeting with non-viral vectors into a rDNA locus. The ability of these genetically modified MSCs to inhibit in vivo melanoma growth is suggestive of the clinical potential of autologous cell therapy in cancer.

Mesenchymal Stromal Cells: Emerging Roles in Bone Metastasis

Bone metastasis is the most advanced stage of many cancers and indicates a poor prognosis for patients due to resistance to anti-tumor therapies. The establishment of metastasis within the bone is a multistep process. To ensure survival within the bone marrow, tumor cells must initially colonize a niche in which they can enter dormancy. Subsequently, reactivation permits the proliferation and growth of the tumor cells, giving rise to a macro-metastasis displayed clinically as a bone metastatic lesion. Here, we review the evidences that suggest mesenchymal stromal cells play an important role in each of these steps throughout the development of bone metastasis. Similarities between the molecular mechanisms implicated in these processes and those involved in the homeostasis of the bone indicate that the metastatic cells may exploit the homeostatic processes to their own advantage. Identifying the molecular interactions between the mesenchymal stromal cells and tumor cells that promote tumor development may offer insight into potential therapeutic targets that could be utilized to treat bone metastasis.

Interleukin 6 Plays a Role in the Migration of Magnetically Levitated Mesenchymal Stem Cells Spheroids

Mesenchymal stem cells (MSCs) reside quiescently within a specialised ‘niche’ environment in the bone marrow. However, following appropriate signalling cues, MSCs mobilise and migrate out from the niche, typically toward either sites of injury (a regenerative response) or toward primary tumours (an intrinsic homing response, which promotes MSCs as cellular vectors for therapeutic delivery). To date, very little is known about MSC mobilisation. By adopting a 3D MSC niche model, whereby MSC spheroids are cultured within a type I collagen gel, recent studies have highlighted interleukin-6 (IL-6) as a key cytokine involved in MSC migration. Herein, the ability of IL-6 to induce MSC migration was further investigated, and the key matrix metalloproteinases used to effect cell mobilisation were identified. Briefly, the impact of IL-6 on the MSC migration in a two-dimensional model systems was characterised—both visually using an Ibidi chemotaxis plate array (assessing for directional migration) and then via a standard 2D monolayer experiment, where cultured cells were challenged with IL-6 and extracted media tested using an Abcam Human MMP membrane antibody array. The 2D assay displayed a strong migratory response toward IL-6 and analysis of the membrane arrays data showed significant increases of several key MMPs. Both data sets indicated that IL-6 is important in MSC mobilisation and migration. We also investigated the impact of IL-6 induction on MSCs in 3D spheroid culture, serving as a simplistic model of the bone marrow niche, characterised by fluorescently tagged magnetic nanoparticles and identical membrane antibody arrays. An increase in MMP levels secreted by cells treated with 1 ng/mL IL-6 versus control conditions was noted in addition to migration of cells away from the central spheroid mass.

Secreted factors from metastatic prostate cancer cells stimulate mesenchymal stem cell transition to a pro-tumourigenic 'activated' state that enhances prostate cancer cell migration

Mesenchymal stem cells (MSCs) are a heterogeneous population of multipotent cells that are capable of differentiating into osteocytes, chondrocytes and adipocytes. Recently, MSCs have been found to home to the tumour site and engraft in the tumour stroma. However, it is not yet known whether they have a tumour promoting or suppressive function. We investigated the interaction between prostate cancer cell lines 22Rv1, DU145 and PC3, and bone marrow-derived MSCs. MSCs were 'educated' for extended periods in prostate cancer cell conditioned media and PC3-educated MSCs were found to be the most responsive with a secretory profile rich in pro-inflammatory cytokines. PC3-educated MSCs secreted increased osteopontin (OPN), interleukin-8 (IL-8) and fibroblast growth factor-2 (FGF-2) and decreased soluble fms-like tyrosine kinase-1 (sFlt-1) compared to untreated MSCs. PC3-educated MSCs showed a reduced migration and proliferation capacity that was dependent on exposure to PC3-conditioned medium. Vimentin and α-smooth muscle actin (αSMA) expression was decreased in PC3-educated MSCs compared to untreated MSCs. PC3 and DU145 education of healthy donor and prostate cancer patient-derived MSCs led to a reduced proportion of FAP+ αSMA+ cells contrary to characteristics commonly associated with cancer associated fibroblasts (CAFs). The migration of PC3 cells was increased toward both PC3-educated and DU145-educated MSCs compared to untreated MSCs, while DU145 migration was only enhanced toward patient-derived MSCs. In summary, MSCs developed an altered phenotype in response to prostate cancer conditioned medium which resulted in increased secretion of pro-inflammatory cytokines, modified functional activity and the chemoattraction of prostate cancer cells.

pIL6-TRAIL-engineered umbilical cord mesenchymal/stromal stem cells are highly cytotoxic for myeloma cells both in vitro and in vivo

Background

Mesenchymal/stromal stem cells (MSCs) are favorably regarded in anti-cancer cytotherapies for their spontaneous chemotaxis toward inflammatory and tumor environments associated with an intrinsic cytotoxicity against tumor cells. Placenta-derived or TRAIL-engineered adipose MSCs have been shown to exert anti-tumor activity in both in-vitro and in-vivo models of multiple myeloma (MM) while TRAIL-transduced umbilical cord (UC)-MSCs appear efficient inducers of apoptosis in a few solid tumors. However, apoptosis is not selective for cancer cells since specific TRAIL receptors are also expressed by a number of normal cells. To overcome this drawback, we propose to transduce UC-MSCs with a bicistronic vector including the TRAIL sequence under the control of IL-6 promoter (pIL6) whose transcriptional activation is promoted by the MM milieu.

Methods

UC-MSCs were transduced with a bicistronic retroviral vector (pMIGR1) encoding for green fluorescent protein (GFP) and modified to include the pIL6 sequence upstream of the full-length human TRAIL cDNA. TRAIL expression after stimulation with U-266 cell conditioned medium, or IL-1α/IL-1β, was evaluated by flow cytometry, confocal microscopy, real-time PCR, western blot analysis, and ELISA. Apoptosis in MM cells was assayed by Annexin V staining and by caspase-8 activation. The cytotoxic effect of pIL6-TRAIL⁺-GFP⁺-UC-MSCs on MM growth was evaluated in SCID mice by bioluminescence and ex vivo by caspase-3 activation and X-ray imaging. Statistical analyses were performed by Student’s t test, ANOVA, and logrank test for survival curves.

Results

pIL6-TRAIL⁺-GFP⁺-UC-MSCs significantly expressed TRAIL after stimulation by either conditioned medium or by IL-1α/IL-1β, and induced apoptosis in U-266 cells. Moreover, when systemically injected in SCID mice intratibially xenografted with U-266, those cells underwent within MM tibia lesions and significantly reduced the tumor burden by specific induction of apoptosis in MM cells as revealed by caspase-3 activation.

Conclusions

Our tumor microenvironment-sensitive model of anti-MM cytotherapy is regulated by the axis pIL6/IL-1α/IL-1β and appears suitable for further preclinical investigation not only in myeloma bone disease in which UC-MSCs would even participate to bone healing as described, but also in other osteotropic tumors whose milieu is enriched of cytokines triggering the pIL6.

Mesenchymal stroma: Role in osteosarcoma progression

The initiation and progression of malignant tumors are supported by their microenvironment: cancer cells per se cannot explain growth and formation of the primary or metastasis, and a combination of proliferating tumor cells, cancer stem cells, immune cells mesenchymal stromal cells and/or cancer-associated fibroblasts all contribute to the tumor bulk. The interaction between these multiple players, under different microenvironmental conditions of biochemical and physical stimuli (i.e. oxygen tension, pH, matrix mechanics), regulates the production and biological activity of several soluble factors, extracellular matrix components, and extracellular vesicles that are needed for growth, maintenance, chemoresistance and metastatization of cancer. In osteosarcoma, a very aggressive cancer of young adults characterized by the extensive need for more effective therapies, this aspect has been only recently explored. In this view, we will discuss the role of stroma, with a particular focus on the mesenchymal stroma, contributing to osteosarcoma progression through inherent features for homing, neovascularization, paracrine cross-feeding, microvesicle secretion, and immune modulation, and also by responding to the changes of the microenvironment that are induced by tumor cells. The most recent advances in the molecular cues triggered by cytokines, soluble factors, and metabolites that are partially beginning to unravel the axis between stromal elements of mesenchymal origin and osteosarcoma cells, will be reviewed providing insights likely to be used for novel therapeutic approaches against sarcomas.

Ultrasound-Mediated Mesenchymal Stem Cells Transfection as a Targeted Cancer Therapy Platform

Mesenchymal stem cells (MSCs) hold tremendous potential as a targeted cell-based delivery platform for inflammatory and cancer therapy. Genetic manipulation of MSCs, however, is challenging, and therefore, most studies using MSCs as therapeutic cell carriers have utilized viral vectors to transduce the cells. Here, we demonstrate, for the first time, an alternative approach for the efficient transfection of MSCs; therapeutic ultrasound (TUS). Using TUS with low intensities and moderate frequencies, MSCs were transfected with a pDNA encoding for PEX, a protein that inhibits tumor angiogenesis, and studied as a cell vehicle for in vivo tumor therapy. TUS application did not alter the MSCs' stemness or their homing capabilities, and the transfected MSCs transcribed biologically active PEX. Additionally, in a mouse model, 70% inhibition of prostate tumor growth was achieved following a single I.V. administration of MSCs that were TUS-transfected with pPEX. Further, the repeated I.V. administration of TUS-pPEX transfected-MSCs enhanced tumor inhibition up to 84%. Altogether, these results provide a proof of concept that TUS-transfected MSCs can be effectively used as a cell-based delivery approach for the prospective treatment of cancer.

Activation and Differentiation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are multipotent cells and exhibit two main characteristics that define stem cells: self-renewal and differentiation. MSCs can migrate to sites of injury, inflammation, and tumor. Moreover, MSCs undergo myofibroblast like differentiation, including increased production of α-SMA in response to transforming growth factor-β (TGF-β), a growth factor commonly secreted by tumor cells to evade immune surveillance. Based on our previous finding hMSCs become activated and resemble carcinoma-associated myofibroblasts upon prolonged exposure to conditioned medium from MDAMB231 human breast cancer cells. Here, we show that keratinocyte conditioned medium (KCM) induces differentiation of MSCs to resemble dermal myofibroblast like cells using immunofluorescence techniques demonstrating punctate vinculin staining, and F-actin filaments.