Tumor microenvironment: bone marrow-mesenchymal stem cells as key players

Self-assembling nanoparticles encapsulating zoledronic acid inhibit mesenchymal stromal cells differentiation, migration and secretion of proangiogenic factors and their interactions with prostate cancer cells

Zoledronic Acid (ZA) rapidly concentrates into the bone and reduces skeletal-related events and pain in bone metastatic prostate cancer (PCa), but exerts only a limited or absent impact as anti-cancer activity. Recently, we developed self-assembling nanoparticles (NPS) encapsulating zoledronic acid (NZ) that allowed a higher intratumor delivery of the drug compared with free zoledronic acid (ZA) in in vivo cancer models of PCa. Increasing evidence suggests that Bone Marrow (BM) Mesenchymal stromal cells (BM-MSCs) are recruited into the stroma of developing tumors where they contribute to progression by enhancing tumor growth and metastasis.

We demonstrated that treatment with NZ decreased migration and differentiation into adipocytes and osteoblasts of MSCs and inhibited osteoclastogenesis. Treatment with NZ reduced the capability of MSCs to promote the migration and the clonogenic growth of the prostate cancer cell lines PC3 and DU145. The levels of Interleukin-6 and of the pro-angiogenic factors VEGF and FGF-2 were significantly reduced in MSC-CM derived from MSCs treated with NZ, and CCL5 secretion was almost totally abolished. Moreover, treatment of MSCs with supernatants from PC3 cells, leading to tumor-educated MSCs (TE-MSCs), increased the secretion of IL-6, CCL5, VEGF and FGF-2 by MSCs and increased their capability to increase PC3 cells clonogenic growth. Treatment with NZ decreased cytokine secretion and the pro-tumorigenic effects also of TE-MSCS. In conclusion, demonstrating that NZ is capable to inhibit the cross talk between MSCs and PCa, this study provides a novel insight to explain the powerful anticancer activity of NZ on PCa.

Mesenchymal Stromal Cells-Derived β2-Microglobulin Promotes Epithelial-Mesenchymal Transition of Esophageal Squamous Cell Carcinoma Cells

Mesenchymal stromal cells (MSCs) have been considered as one of the pivotal type of cells composing the tumor microenvironment. Although contact-dependent mechanisms and paracrine factors are thought to collaborate in governing the MSCs-based effects on tumors progression, the underlying mechanisms remain largely unknown. In particular, the involvement of MSCs-derived cytokines in the epithelial-mesenchymal transition (EMT) of esophageal squamous cell carcinoma (ESCC) has not been clarified. In this study, we observed that β2-Microglobulin (B2M) is highly expressed in MSCs but scarcely in ESCC cells. Based on the previously described EMT promoting effect of B2M, we investigated the in vitro effect of MSCs-derived B2M on the EMT of ESCC cells, and discovered its subsequent enhancing effects on cell mobility and tumor-initiation. Further xenograft transplantation experiments confirmed the in vivo induction of tumor-initiation by MSCs-derived B2M. Noteworthy, we showed that the B2M expression positively correlated with poor prognosis. The fact that B2M is primarily expressed by the stroma of the ESCC tissue strengthens our hypothesis that in ESCC, MSCs-derived B2M promotes tumor-initiation and invasion via enhancing EMT, resulting in an adverse prognosis for the patients. Our results will be valuable for the prediction of the development and treatment of ESCC.

Bone marrow-derived mesenchymal stem cells promote invasiveness and transendothelial migration of osteosarcoma cells via a mesenchymal to amoeboid transition

There is growing evidence to suggest that bone marrow‐derived mesenchymal stem cells (BM‐MSCs) are key players in tumour stroma. Here, we investigated the cross‐talk between BM‐MSCs and osteosarcoma (OS) cells. We revealed a strong tropism of BM‐MSCs towards these tumour cells and identified monocyte chemoattractant protein (MCP)‐1, growth‐regulated oncogene (GRO)‐α and transforming growth factor (TGF)‐β1 as pivotal factors for BM‐MSC chemotaxis. Once in contact with OS cells, BM‐MSCs trans‐differentiate into cancer‐associated fibroblasts, further increasing MCP‐1, GRO‐α, interleukin (IL)‐6 and IL‐8 levels in the tumour microenvironment. These cytokines promote mesenchymal to amoeboid transition (MAT), driven by activation of the small GTPase RhoA, in OS cells, as illustrated by the in vitro assay and live imaging. The outcome is a significant increase of aggressiveness in OS cells in terms of motility, invasiveness and transendothelial migration. In keeping with their enhanced transendothelial migration abilities, OS cells stimulated by BM‐MSCs also sustain migration, invasion and formation of the in vitro capillary network of endothelial cells. Thus, BM‐MSC recruitment to the OS site and the consequent cytokine‐induced MAT are crucial events in OS malignancy.

Distinct protein signatures of acute myeloid leukemia bone marrow-derived stromal cells are prognostic for patient survival

Mesenchymal stromal cells (MSC) support acute myeloid leukemia (AML) cell survival in the bone marrow (BM) microenvironment. Protein expression profiles of AML-derived MSC are unknown. Reverse phase protein array analysis was performed to compare expression of 151 proteins from AML-MSC (n=106) with MSC from healthy donors (n=71). Protein expression differed significantly between the two groups with 19 proteins over-expressed in leukemia stromal cells and 9 over-expressed in normal stromal cells. Unbiased hierarchical clustering analysis of the samples using these 28 proteins revealed three protein constellations whose variation in expression defined four MSC protein expression signatures: Class 1, Class 2, Class 3, and Class 4. These cell populations appear to have clinical relevance. Specifically, patients with Class 3 cells have longer survival and remission duration compared to other groups. Comparison of leukemia MSC at first diagnosis with those obtained at salvage (i.e. relapse/refractory) showed differential expression of 9 proteins reflecting a shift toward osteogenic differentiation. Leukemia MSC are more senescent compared to their normal counterparts, possibly due to the overexpressed p53/p21 axis as confirmed by high β-galactosidase staining. In addition, overexpression of BCL-X_L in leukemia MSC might give survival advantage under conditions of senescence or stress and overexpressed galectin-3 exerts profound immunosuppression. Together, our findings suggest that the identification of specific populations of MSC in AML patients may be an important determinant of therapeutic response.

Mesenchymal stem cells promote osteosarcoma cell survival and drug resistance through activation of STAT3

Increasing evidence suggests that the tumor microenvironment plays a key role in the development of drug resistant tumor cells. In this study, we tried to determine whether the mesenchymal stem cells (MSCs) in the tumor microenvironment contribute to the increased chemoresistance of osteosarcoma. We found that exposure of Saos-2 and U2-OS cells to MSCs conditioned medium (CM) increased the viable cells in the presence of therapeutic concentrations of doxorubicin or cisplatin. Meanwhile, the MSC CM-associated pro-proliferative effects were accompanied by reduced caspase 3/7 activity and Annexin V binding. We confirmed that STAT3 activation by IL-6 regulates MSCs-induced chemoresistance. Blockade of this signal re-sensitized drug-resistant Saos-2 cells to drug treatment. Using a osteosarcoma mouse model with co-injection of MSCs with Saos-2cells, we found that inhibition of STAT3 prolonged the survival time of tumor bearing mice by suppressing tumor growth and increasing the sensitivity of tumor cells to doxorubicin. Finally, we demonstrated that increased expression of p-STAT3, multidrug resistance protein (MRP) and P-glycoprotein (MDR-1) was associated with high chemotherapy resistance in clinical osteosarcoma samples. Collectively, our findings suggest that MSCs within the tumor microenvironment may represent a new target to enhance chemotherapeutic efficacy in osteosarcoma patients.

Human colorectal cancer-derived mesenchymal stem cells promote colorectal cancer progression through IL-6/JAK2/STAT3 signaling

Mesenchymal stem cells (MSCs) have been reported to localize in colorectal carcinomas, and participate in the formation of the tumor microenvironment. They have recently been isolated from colorectal cancer tissues, and are implicated in the growth, invasion, and metastasis of cancer cells. However, the roles and detailed mechanisms associated with human colorectal cancer-derived MSCs (CC-MSCs) have not been fully addressed. In this study, we found that CC-MSCs increased the migration and invasion of colorectal cancer cells and promoted the tumorigenesis of colorectal cancer through epithelial-to-mesenchymal transition (EMT) in vitro. We also found that CC-MSCs enhanced the growth and metastasis of colorectal cancer in vivo. Mechanistically, we determined that interleukin-6 (IL-6) was the most highly expressed cytokine in the CC-MSC conditioned medium, and promoted the progression of colorectal cancer cells through IL-6/JAK2/STAT3 signaling, which activated PI3K/AKT signaling. We used anti-IL-6 antibody to target IL-6. Collectively, these results reveal that the IL-6 secreted by CC-MSCs enhances the progression of colorectal cancer cells through IL-6/JAK2/STAT3 signaling, and could provide a novel therapeutic or preventive target.

Targeting the IL-17/IL-6 axis can alter growth of Chronic Lymphocytic Leukemia in vivo/in vitro

The tumor microenvironment (TME) is critical to the longevity of tumor B cells in chronic lymphocytic leukemia (CLL). Bone marrow mesenchymal stem cells (BMMSCs) and the cytokines they produce including IL-6 are important components of the TME in CLL. We found BMMSCs supported the survival of CLL cells in vitro through an IL-6 dependent mechanism. IL-17 which induces IL-6 generation in a variety of cells increased production of IL-6 both in CLL cells and BMMSCs in vitro. In a xenograft CLL mouse model, BMMSCs and the culture supernatant of BMMSCs increased engraftment of CLL cells through an IL-6 mediated mechanism with human recombinant IL-6 showing similar effects in vivo. Human recombinant IL-17 treatment also increased CLL engraftment in mice through an IL-6 mediated mechanism. Plasma of CLL patients showed elevated levels of both IL-6 and IL-17 by ELISA compared with healthy controls, with levels of IL-6 linearly correlated with IL-17 levels. CLL patients requiring fludarabine based chemotherapy expressed higher levels of IL-6 and IL-17, while CLL patients with the lowest levels of IgA/IgM had higher levels of IL-6, but not IL-17. These data imply an important role for the IL-17/IL-6 axis in CLL which could be therapeutic targets.

miR-155-5p inhibition promotes the transition of bone marrow mesenchymal stem cells to gastric cancer tissue derived MSC-like cells via NF-κB p65 activation

Gastric cancer tissue-derived MSC-like cells (GC-MSC) share similar characteristics to bone marrow MSC (BM-MSC); however, the phenotypical and functional differences and the molecular mechanism of transition between the two cell types remain unclear. Compared to BM-MSC, GC-MSC exhibited the classic phenotype of reactive stroma cells, a stronger gastric cancer promoting capacity and lower expression of miR-155-5p. Inhibition of miR-155-5p by transfecting miRNA inhibitor induced a phenotypical and functional transition of BM-MSC into GC-MSC-like cells, and the reverse experiment deprived GC-MSC of tumor-promoting phenotype and function. NF-kappa B p65 (NF-κB p65) and inhibitor of NF-kappa B kinase subunit epsilon (IKBKE/IKKε) were identified as targets of miR-155-5p and important for miRNA inhibitor activating NF-κB p65 in the transition. Inactivation of NF-κB by pyrrolidine dithiocarbamic acid (PDTC) significantly blocked the effect of miR-155-5p inhibitor on BM-MSC. IKBKE, NF-κB p65 and phospho-NF-κB p65 proteins were highly enriched in MSC-like cells of gastric cancer tissues, and the latter two were correlated with the pathological progression of gastric cancer. In GC-MSC, the expression of miR-155-5p was downregulated and NF-κB p65 protein was increased and activated. NF-κB inactivation by PDTC or knockdown of its downstream cytokines reversed the phenotype and function of GC-MSC. Taken together, our findings revealed that miR-155-5p downregulation induces BM-MSC to acquire a GC-MSC-like phenotype and function depending on NF-κB p65 activation, which suggests a novel mechanism underlying the cancer associated MSC remodeling in the tumor microenvironment and offers an effective target and approach for gastric cancer therapy.

The key role of extracellular vesicles in the metastatic process

Extracellular vesicles (EVs), including exosomes, have a key role in the paracrine communication between organs and compartments. EVs shuttle virtually all types of biomolecules such as proteins, lipids, nucleic acids, metabolites and even pharmacological compounds. Their ability to transfer their biomolecular cargo into target cells enables EVs to play a key role in intercellular communication that can regulate cellular functions such as proliferation, apoptosis and migration. This has led to the emergence of EVs as a key player in tumor growth and metastasis through the formation of "tumor niches" in target organs. Recent data have also been shown that EVs may transform the microenvironment of primary tumors thus favoring the selection of cancer cells with a metastatic behavior. The release of EVs from resident non-malignant cells may contribute to the metastatic processes as well. However, cancer EVs may induce malignant transformation in resident mesenchymal stem cells, suggesting that the metastatic process is not exclusively due to circulating tumor cells. In this review, we outline and discuss evidence-based roles of EVs in actively regulating multiple steps of the metastatic process and how we can leverage EVs to impair metastasis.

In vivo tracking of the tropism of mesenchymal stem cells to malignant gliomas using reporter gene-based MR imaging

Mesenchymal stem cells (MSCs) have emerged as a promising cellular vehicle for gene therapy of malignant gliomas due to their property of tumor tropism. However, MSCs may show bidirectional and divergent effects on tumor growth. Therefore, a robust surveillance system with a capacity for noninvasive monitoring of the homing, distribution and fate of stem cells in vivo is highly desired for developing stem cell-based gene therapies for tumors. In this study, we used ferritin gene-based magnetic resonance imaging (MRI) to track the tumor tropism of MSCs in a rat orthotopic xenograft model of malignant glioma. MSCs were transduced with lentiviral vectors expressing ferritin heavy chain (FTH) and enhanced green fluorescent protein (eGFP). Intra-arterial, intravenous and intertumoral injections of these FTH transgenic MSCs (FTH-MSCs) were performed in rats bearing intracranial orthotopic C6 gliomas. The FTH-MSCs were detected as hypointense signals on T2- and T2*-weighted images on a 3.0 T clinical MRI. After intra-arterial injection, 17% of FTH-MSCs migrated toward the tumor and gradually diffused throughout the orthotopic glioma. This dynamic process could be tracked in vivo by MRI up to 10 days of follow-up, as confirmed by histology. Moreover, the tumor tropism of MSCs showed no appreciable impact on the progression of the tumor. These results suggest that FTH reporter gene-based MRI can be used to reliably track the tropism and fate of MSCs after their systemic transplantation in orthotopic gliomas. This real-time in vivo tracking system will facilitate the future development of stem cell-based therapies for malignant gliomas.

IL-8, GRO and MCP-1 produced by hepatocellular carcinoma microenvironment determine the migratory capacity of human bone marrow-derived mesenchymal stromal cells without affecting tumor aggressiveness

New therapies are needed for advanced hepatocellular carcinoma (HCC) and the use of mesenchymal stromal cells (MSCs) carrying therapeutic genes is a promising strategy. HCC produce cytokines recruiting MSCs to the tumor milieu and modifying its biological properties. Our aim was to study changes generated on human MSCs exposed to conditioned media (CM) derived from human HCC fresh samples and xenografts. All CM shared similar cytokines expression pattern including CXCL1-2-3/GRO, CCL2/MCP-1 and CXCL8/IL-8 being the latter with the highest concentration. Neutralizing and knockdown experiments of CCL2/MCP-1, CXCL8/IL-8, CXCR1 and CXCR2 reduced in vitro MSC migration of ≥20%. Simultaneous CXCR1 and CXCR2 neutralization resulted in 50% of MSC migration inhibition. MSC stimulated with CM (sMSC) from HuH7 or HC-PT-5 showed a 2-fold increase of migration towards the CM compared with unstimulated MSC (usMSC). Gene expression profile of sMSC showed ~500 genes differentially expressed compared with usMSC, being 46 genes related with cell migration and invasion. sMSC increased fibroblasts and endothelial cells chemotaxis. Finally, sMSC with HuH7 CM and then inoculated in HCC tumor bearing-mice did not modify tumor growth. In this work we characterized factors produced by HCC responsible for the changes in MSC chemotactic capacity with would have an impact on therapeutic use of MSCs for human HCC.

The Epithelial-to-Mesenchymal Transition in Breast Cancer: Focus on Basal-Like Carcinomas

Breast cancer is a heterogeneous disease that is characterized by a high grade of cell plasticity arising from the contribution of a diverse range of factors. When combined, these factors allow a cancer cell to transition from an epithelial to a mesenchymal state through a process of dedifferentiation that confers stem-like features, including chemoresistance, as well as the capacity to migrate and invade. Understanding the complex events that lead to the acquisition of a mesenchymal phenotype will therefore help to design new therapies against metastatic breast cancer. Here, we recapitulate the main endogenous molecular signals involved in this process, and their cross-talk with paracrine factors. These signals and cross-talk include the extracellular matrix; the secretome of cancer-associated fibroblasts, macrophages, cancer stem cells, and cancer cells; and exosomes with their cargo of miRNAs. Finally, we highlight some of the more promising therapeutic perspectives based on counteracting the epithelial-to-mesenchymal transition in breast cancer cells.

Mechano-Signal Transduction in Mesenchymal Stem Cells Induces Prosaposin Secretion to Drive the Proliferation of Breast Cancer Cells

In response to chemical stimuli from cancer cells, mesenchymal stem cells (MSC) can differentiate into cancer-associated fibroblasts (CAF) and promote tumor progression. How mechanical stimuli such as stiffness of the extracellular matrix (ECM) contribute to MSC phenotype in cancer remains poorly understood. Here, we show that ECM stiffness leads to mechano-signal transduction in MSC, which promotes mammary tumor growth in part through secretion of the signaling protein prosaposin. On a stiff matrix, MSC cultured with conditioned media from mammary cancer cells expressed increased levels of α-smooth muscle actin, a marker of CAF, compared with MSC cultured on a soft matrix. By contrast, MSC cultured on a stiff matrix secreted prosaposin that promoted proliferation and survival of mammary carcinoma cells but inhibited metastasis. Our findings suggest that in addition to chemical stimuli, increased stiffness of the ECM in the tumor microenvironment induces differentiation of MSC to CAF, triggering enhanced proliferation and survival of mammary cancer cells. Cancer Res; 77(22); 6179-89. ©2017 AACR.

Interleukin-6 blockade attenuates lung cancer tissue construction integrated by cancer stem cells

In the present study, we successfully generated lung cancer stem cell (CSC)-like cells by introducing a small set of transcription factors into a lung cancer cell line. In addition to properties that are conventionally referred to as CSC properties, the lung induced CSCs exhibited the ability to form lung cancer-like tissues in vitro with vascular cells and mesenchymal stem cells, which showed structures and immunohistological patterns that were similar to human lung cancer tissues. We named them “lung cancer organoids”. We found that interleukin-6 (IL-6), which was expressed in the lung induced CSCs, facilitates the formation of lung cancer organoids via the conversion of mesenchymal stem cells into alpha-smooth muscle actin (αSMA)-positive cells. Interestingly, the combination of anti-IL-6 antibody and cisplatin could destroy the lung cancer organoids, while cisplatin alone could not. Furthermore, IL-6 mRNA-positive cancer cells were found in clinical lung cancer samples. These results suggest that IL-6 could be a novel therapeutic target in lung cancer.

YAP signaling in gastric cancer-derived mesenchymal stem cells is critical for its promoting role in cancer progression

Cancer-associated mesenchymal stem cells (MSCs) are critically involved in tumor development and progression. However, the mechanisms of action for MSCs in cancer remain largely unknown. Herein, we reported that the expression of Yes-associated protein 1 (YAP) was higher in gastric cancer derived mesenchymal stem cells (GC-MSCs) than that in bone marrow derived MSCs (BM-MSCs). YAP knockdown not only inhibited the growth, migration and invasion, and stemness of GC-MSCs, but also suppressed their promoting effect on gastric cancer growth in vitro and in vivo. In addition, the interference of YAP expression in GC-MSCs also attenuated the promoting role of gastric cancer cells in endothelial cell tube formation and migration. Mechanistically, YAP knockdown reduced the activation of β-catenin and its target genes in gastric cancer cells by GC-MSCs. Taken together, these findings suggest that YAP activation in GC-MSCs plays an important role in promoting gastric cancer progression, which may represent a potential target for gastric cancer therapy.

Tumor-educated mesenchymal stem cells promote pro-metastatic phenotype

Multipotent mesenchymal stem cells (MSCs) are recruited into tumor microenvironment in response to multiple signals produced by cancer cells. Molecules involved in their homing to tumors are the same inflammatory mediators produced by injured tissues: chemokines, cytokines and growth factors. When MSCs arrive into the tumor microenvironment these are “educated” to have pro-metastatic behaviour. Firstly, they promote cancer immunosuppression modulating both innate and adaptive immune systems. Moreover, tumor associated-MSCs trans-differentiating into cancer-associated fibroblasts can induce epithelial-mesenchymal-transition program in tumor cells. This process determinates a more aggressive phenotype of cancer cells by increasing their motility and invasiveness and favoring their dissemination to distant sites. In addition, MSCs are involved in the formation and modelling of pre-metastatic niches creating a supportive environment for colonization of circulating tumor cells.

The development of novel therapeutic approaches targeting the different functions of MSCs in promoting tumor progression as well as the mechanisms underlying their activities could enhance the efficacy of conventional and immune anti-cancer therapies.

Furthermore, many studies report the use of MSCs engineered to express different genes or as vehicle to specifically deliver novel drugs to tumors exploiting their strong tropism. Importantly, this approach can enhance local therapeutic efficacy and reduce the risk of systemic side effects.

Metabolic Plasticity of Stem Cells and Macrophages in Cancer

In addition to providing essential molecules for the overall function of cells, metabolism plays an important role in cell fate and can be affected by microenvironmental stimuli as well as cellular interactions. As a specific niche, tumor microenvironment (TME), consisting of different cell types including stromal/stem cells and immune cells, is characterized by distinct metabolic properties. This review will be focused on the metabolic plasticity of mesenchymal stromal/stem cells (MSC) and macrophages in TME, as well as on how the metabolic state of cancer stem cells (CSC), as key drivers of oncogenesis, affects their generation and persistence. Namely, heterogenic metabolic phenotypes of these cell populations, which include various levels of dependence on glycolysis or oxidative phosphorylation are closely linked to their complex roles in cancer progression. Besides well-known extrinsic factors, such as cytokines and growth factors, the differentiation and activation states of CSC, MSC, and macrophages are coordinated by metabolic reprogramming in TME. The significance of mutual metabolic interaction between tumor stroma and cancer cells in the immune evasion and persistence of CSC is currently under investigation.

The pathological structure of the perivascular niche in different microvascular patterns of glioblastoma

The perivascular niche is critical for intercellular communication between resident cell types in glioblastoma (GBM), and it plays a vital role in maintaining the glioma stem cell (GSC) microenvironment. It is shown in abundant research that different microvascular patterns exist in GBM; and it can be implied that different microvascular patterns are associated with different pathological structures in the perivascular niche. However, the pathological structure of the perivascular niche is still not clear. Here, we investigated the distribution and biological characteristics of different microvascular pattern niches (MVPNs) in GBM by detecting the expression of CD34, CD133, Nestin, α-SMA, GFAP and CD14 in the perivascular niche using multiple -fluorescence. The four basic microvascular patterns are microvascular sprouting (MS), vascular cluster (VC), vascular garland (VG), and glomeruloid vascular proliferation (GVP). By analyzing the proportion of the area of each marker in four types of formations, the results indicated that the expression of CD34, CD133 and Nestin in MS and VC was significantly lower than that in VG and GVP (P<0.05). Furthermore, the results showed that α-SMA expression different in the MS, VC, VG and GVP (P<0.05). However, the expression of GFAP and CD14 in each type of formation exhibited no significant difference (P>0.05). According to the area distributions of different markers, we mapped four precise simulation diagrams to provide an effective foundation for the accurate simulation of glioblastoma in vitro.

Intravenous infusion of human bone marrow mesenchymal stromal cells promotes functional recovery and neuroplasticity after ischemic stroke in mice

Transplantation of human bone marrow mesenchymal stromal cells (hBM-MSC) promotes functional recovery after stroke in animal models, but the mechanisms underlying these effects remain incompletely understood. We tested the efficacy of Good Manufacturing Practices (GMP) compliant hBM-MSC, injected intravenously 3.5 hours after injury in mice subjected to transient middle cerebral artery occlusion (tMCAo). We addressed whether hBM-MSC are efficacious and if this efficacy is associated with cortical circuit reorganization using neuroanatomical analysis of GABAergic neurons (parvalbumin; PV-positive cells) and perineuronal nets (PNN), a specialized extracellular matrix structure which acts as an inhibitor of neural plasticity. tMCAo mice receiving hBM-MSC, showed early and lasting improvement of sensorimotor and cognitive functions compared to control tMCAo mice. Furthermore, 5 weeks post-tMCAo, hBM-MSC induced a significant rescue of ipsilateral cortical neurons; an increased proportion of PV-positive neurons in the perilesional cortex, suggesting GABAergic interneurons preservation; and a lower percentage of PV-positive cells surrounded by PNN, indicating an enhanced plastic potential of the perilesional cortex. These results show that hBM-MSC improve functional recovery and stimulate neuroprotection after stroke. Moreover, the downregulation of “plasticity brakes” such as PNN suggests that hBM-MSC treatment stimulates plasticity and formation of new connections in the perilesional cortex.

Tumor-Stroma Crosstalk in Bone Tissue: The Osteoclastogenic Potential of a Breast Cancer Cell Line in a Co-Culture System and the Role of EGFR Inhibition

Although bone metastases represent a major challenge in the natural history of breast cancer (BC), the complex interactions involved have hindered the development of robust in vitro models. The aim of this work is the development of a preclinical model of cancer and bone stromal cells to mimic the bone microenvironment. We studied the effects on osteoclastogenesis of BC cells and Mesenchymal stem cells (MSC) cultured alone or in combination. We also analyzed: (a) whether the blockade of the Epithelial Growth Factor Receptor (EGFR) pathway modified their influence on monocytes towards differentiation, and (b) the efficacy of bone-targeted therapy on osteoclasts. We evaluated the osteoclastogenesis modulation of human peripheral blood monocytes (PBMC) indirectly induced by the conditioned medium (CM) of the human BC cell line SCP2, cultured singly or with MSC. Osteoclastogenesis was evaluated by TRAP analysis. The effect of the EGFR blockade was assessed by treating the cells with gefitinib, and analyzed with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Western Blot (WB). We observed that SCP2 co-cultured with MSC increased the differentiation of PBMC. This effect was underpinned upon pre-treatment of the co-culture with gefitinib. Co-culture of SCP2 with MSC increased the expression of both the bone-related marker Receptor Activator of Nuclear Factor κB (RANK) and EGFR in BC cells. These upregulations were not affected by the EGFR blockade. The effects of the CM obtained by the cells treated with gefitinib in combination with the treatment of the preosteoclasts with the bone-targeted agents and everolimus enhanced the inhibition of the osteoclastogenesis. Finally, we developed a fully human co-culture system of BC cells and bone progenitor cells. We observed that the interaction of MSC with cancer cells induced in the latter molecular changes and a higher power of inducing osteoclastogenesis. We found that blocking EGFR signaling could be an efficacious strategy for breaking the interactions between cancer and bone cells in order to inhibit bone metastasis.

Drug-induced amino acid deprivation as strategy for cancer therapy

Cancer is caused by uncontrollable growth of neoplastic cells, leading to invasion of adjacent and distant tissues resulting in death. Cancer cells have specific nutrient(s) auxotrophy and have a much higher nutrient demand compared to normal tissues. Therefore, different metabolic inhibitors or nutrient-depleting enzymes have been tested for their anti-cancer activities. We review recent available laboratory and clinical data on using various specific amino acid metabolic pathways inhibitors in treating cancers. Our focus is on glutamine, asparagine, and arginine starvation. These three amino acids are chosen due to their better scientific evidence compared to other related approaches in cancer treatment. Amino acid-specific depleting enzymes have been adopted in different standard chemotherapy protocols. Glutamine starvation by glutaminase inhibitior, transporter inhibitor, or glutamine depletion has shown to have significant anti-cancer effect in pre-clinical studies. Currently, glutaminase inhibitor is under clinical trial for testing anti-cancer efficacy. Clinical data suggests that asparagine depletion is effective in treating hematologic malignancies even as a single agent. On the other hand, arginine depletion has lower toxicity profile and can effectively reduce the level of pro-cancer biochemicals in patients as shown by ours and others’ data. This supports the clinical use of arginine depletion as anti-cancer therapy but its exact efficacy in various cancers requires further investigation. However, clinical application of these enzymes is usually hindered by common problems including allergy to these foreign proteins, off-target cytotoxicity, short half-life and rapidly emerging chemoresistance. There have been efforts to overcome these problems by modifying the drugs in different ways to circumvent these hindrance such as (1) isolate human native enzymes to reduce allergy, (2) isolate enzyme isoforms with higher specificities and efficiencies, (3) pegylate the enzymes to reduce allergy and prolong the half-lives, and (4) design drug combinations protocols to enhance the efficacy of chemotherapy by drug synergy and minimizing resistance. These improvements can potentially lead to the development of more effective anti-cancer treatment with less adverse effects and higher therapeutic efficacy.

Microfluidics Enabled Bottom-Up Engineering of 3D Vascularized Tumor for Drug Discovery

Development of high-fidelity three-dimensional (3D) models to recapitulate the tumor microenvironment is essential for studying tumor biology and discovering anticancer drugs. Here we report a method to engineer the 3D microenvironment of human tumors, by encapsulating cancer cells in the core of microcapsules with a hydrogel shell for miniaturized 3D culture to obtain avascular microtumors first. The microtumors are then used as the building blocks for assembling with endothelial cells and other stromal cells to create macroscale 3D vascularized tumor. Cells in the engineered 3D microenvironment can yield significantly larger tumors in vivo than 2D-cultured cancer cells. Furthermore, the 3D vascularized tumors are 4.7 and 139.5 times more resistant to doxorubicin hydrochloride (a commonly used chemotherapy drug) than avascular microtumors and 2D-cultured cancer cells, respectively. Moreover, this high drug resistance of the 3D vascularized tumors can be overcome by using nanoparticle-mediated drug delivery. The high-fidelity 3D tumor model may be valuable for studying the effect of microenvironment on tumor progression, invasion, and metastasis and for developing effective therapeutic strategy to fight against cancer.

Cancer immunotherapy: how low-level ionizing radiation can play a key role

The cancer immunoediting hypothesis assumes that the immune system guards the host against the incipient cancer, but also "edits" the immunogenicity of surviving neoplastic cells and supports remodeling of tumor microenvironment towards an immunosuppressive and pro-neoplastic state. Local irradiation of tumors during standard radiotherapy, by killing neoplastic cells and generating inflammation, stimulates anti-cancer immunity and/or partially reverses cancer-promoting immunosuppression. These effects are induced by moderate (0.1-2.0 Gy) or high (>2 Gy) doses of ionizing radiation which can also harm normal tissues, impede immune functions, and increase the risk of secondary neoplasms. In contrast, such complications do not occur with exposures to low doses (≤0.1 Gy for acute irradiation or ≤0.1 mGy/min dose rate for chronic exposures) of low-LET ionizing radiation. Furthermore, considerable evidence indicates that such low-level radiation (LLR) exposures retard the development of neoplasms in humans and experimental animals. Here, we review immunosuppressive mechanisms induced by growing tumors as well as immunomodulatory effects of LLR evidently or likely associated with cancer-inhibiting outcomes of such exposures. We also offer suggestions how LLR may restore and/or stimulate effective anti-tumor immunity during the more advanced stages of carcinogenesis. We postulate that, based on epidemiological and experimental data amassed over the last few decades, whole- or half-body irradiations with LLR should be systematically examined for its potential to be a viable immunotherapeutic treatment option for patients with systemic cancer.

Contribution of neuroblastoma-derived exosomes to the production of pro-tumorigenic signals by bone marrow mesenchymal stromal cells

The bone marrow (BM) niche is a microenvironment promoting survival, dormancy and therapeutic resistance in tumor cells. Central to this function are mesenchymal stromal cells (MSCs). Here, using neuroblastoma (NB) as a model, we demonstrate that NB cells release an extracellular vesicle (EVs) whose protein cargo is enriched in exosomal proteins but lacks cytokines and chemokines. Using three different purification methods, we then demonstrate that NB-derived exosomes were captured by MSCs and induced the production of pro-tumorigenic cytokines and chemokines, including interleukin-6 (IL-6), IL-8/CXCL8, vascular endothelial cell growth factor and monocyte-chemotactic protein-1, with exosomes prepared by size exclusion chromatography having the highest activity. We found no correlation between the IL-6 and IL-8/CXCL8 stimulatory activity of exosomes from eight NB cell lines and their origin, degree of MYCN amplification, drug resistance and disease status. We then demonstrate that the uptake of NB exosomes by MSCs was associated with a rapid increase in ERK1/2 and AKT activation, and that blocking ERK1/2 but not AKT activation inhibited the IL-6 and IL-8/CXCL8 production by MSCs without affecting exosome uptake. Thus, we describe a new mechanism by which NB cells induce in MSCs an inflammatory reaction that contributes to a favorable microenvironment in the BM.

Breast Cancer Stem Cell Therapeutics, Multiple Strategies Versus Using Engineered Mesenchymal Stem Cells With Notch Inhibitory Properties: Possibilities and Perspectives

Relapse cases of cancers are more vigorous and difficult to control due to the preponderance of cancer stem cells (CSCs). Such CSCs that had been otherwise dormant during the first incidence of cancer gradually appear as radiochemoresistant cancer cells. Hence, cancer therapeutics aimed at CSCs would be an effective strategy for mitigating the cancers during relapse. Alternatively, CSC therapy can also be proposed as an adjuvant therapy, along-with the conventional therapies. As regenerative stem cells (RSCs) are known for their trophic effects, anti-tumorogenicity, and better migration toward an injury site, this review aims to address the use of adult stem cells such as dental pulp derived; cord blood derived pure populations of regenerative stem cells for targeting CSCs. Indeed, pro-tumorogenicity of RSCs is of concern and hence has also been dealt with in relation to breast CSC therapeutics. Furthermore, as notch signaling pathways are upregulated in breast cancers, and anti-notch antibody based and sh-RNA based therapies are already in the market, this review focuses the possibilities of engineering RSCs to express notch inhibitory proteins for breast CSC therapeutics. Also, we have drawn a comparison among various possibilities of breast CSC therapeutics, about, notch1 inhibition. J. Cell. Biochem. 119: 141-149, 2018. © 2017 Wiley Periodicals, Inc.

Co-Inflammatory Roles of TGFβ1 in the Presence of TNFα Drive a Pro-inflammatory Fate in Mesenchymal Stem Cells

High plasticity is a hallmark of mesenchymal stem cells (MSCs), and as such, their differentiation and activities may be shaped by factors of their microenvironment. Bones, tumors, and cardiomyopathy are examples of niches and conditions that contain MSCs and are enriched with tumor necrosis factor α (TNFα) and transforming growth factor β1 (TGFβ1). These two cytokines are generally considered as having opposing roles in regulating immunity and inflammation (pro- and anti-inflammatory, respectively). Here, we performed global gene expression analysis of human bone marrow-derived MSCs and identified overlap in half of the transcriptional programs that were modified by TNFα and TGFβ1. The two cytokines elevated the mRNA expression of soluble factors, including mRNAs of pro-inflammatory mediators. Accordingly, the typical pro-inflammatory factor TNFα prominently induced the protein expression levels of the pro-inflammatory mediators CCL2, CXCL8 (IL-8), and cyclooxygenase-2 (Cox-2) in MSCs, through the NF-κB/p65 pathway. In parallel, TGFβ1 did not elevate CXCL8 protein levels and induced the protein expression of CCL2 at much lower levels than TNFα; yet, TGFβ1 readily induced Cox-2 and acted predominantly via the Smad3 pathway. Interestingly, combined stimulation of MSCs by TNFα + TGFβ1 led to a cooperative induction of all three inflammatory mediators, indicating that TGFβ1 functioned as a co-inflammatory cytokine in the presence of TNFα. The cooperative activities of TNFα + TGFβ1 that have led to CCL2 and CXCL8 induction were almost exclusively dependent on p65 activation and were not regulated by Smad3 or by the upstream regulator TGFβ-activated kinase 1 (TAK1). In contrast, the TNFα + TGFβ1-induced cooperative elevation in Cox-2 was mostly dependent on Smad3 (demonstrating cooperativity with activated NF-κB) and was partly regulated by TAK1. Studies with MSCs activated by TNFα + TGFβ1 revealed that they release factors that can affect other cells in their microenvironment and induce breast tumor cell elongation, migration, and scattering out of spheroid tumor masses. Thus, our findings demonstrate a TNFα + TGFβ1-driven pro-inflammatory fate in MSCs, identify specific molecular mechanisms involved, and propose that TNFα + TGFβ1-stimulated MSCs influence the tumor niche. These observations suggest key roles for the microenvironment in regulating MSC functions, which in turn may affect different health-related conditions.

Prognostic significance of TRAIL-R3 and CCR-2 expression in tumor epithelial cells of patients with early breast cancer

Background

Tumor epithelial cells (TEpCs) and spindle-shaped stromal cells, not associated with the vasculature, of patients with early breast cancer express osteoprotegerin (OPG), tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), receptor activator of nuclear factor kappa B ligand, stromal cell derived factor-1, interleukin-6, macrophage colony stimulating factor, chemokine (C-C motif) ligand-2 (CCL-2) and their receptors at significantly higher levels compared with non-neoplastic breast tissues. We evaluated the clinicopathological significance of these ligands and receptors in TEpC and spindle-shaped stromal cells, not associated with the vasculature, to determine their impact on prognosis of patients with early-stage breast cancer.

Methods

We conducted immunohistochemical analyses of protein expression in primary tumors of patients with early breast cancer and analyzed their association with standard prognostic parameters and clinical outcomes, including local relapse, metastatic recurrence, disease-free survival (DFS), metastasis-free survival (MFS), and overall survival (OS).

Results

Elevated levels of TRAIL-R3 and chemokine (C-C motif) receptor 2 (CCR-2) in TEpCs and OPG and CCL-2 in stromal cells were significantly associated with a higher risk of metastasis (p = 0.032, p = 0.003, p = 0.038, and p = 0.049; respectively). Moreover, high expression of TRAIL-R3 and CCR-2 in TEpCs was associated with shorter DFS, MFS, and OS. High TRAIL-R3 expression in TEpCs was an independent prognostic factor for DFS and OS, and high CCR-2 expression in these cells was an independent prognostic factor for MFS.

Conclusions

High levels of TRAIL-R3 and CCR-2 expression in TEpCs identified patients with early breast cancer with poor outcomes.

Human carcinoma-associated mesenchymal stem cells promote ovarian cancer chemotherapy resistance via a BMP4/HH signaling loop

The tumor microenvironment is critical to cancer growth and therapy resistance. We previously characterized human ovarian carcinoma-associated mesenchymal stem cells (CA-MSCs). CA-MSCs are multi-potent cells that can differentiate into tumor microenvironment components including fibroblasts, myofibroblasts and adipocytes. We previously reported CA-MSCs, compared to normal MSCs, express high levels of BMP proteins and promote tumor growth by increasing numbers of cancer stem-like cells (CSCs). We demonstrate here that ovarian tumor cell-secreted Hedgehog (HH) induces CA-MSC BMP4 expression. CA-MSC-derived BMP4 reciprocally increases ovarian tumor cell HH expression indicating a positive feedback loop. Interruption of this loop with a HH pathway inhibitor or BMP4 blocking antibody decreases CA-MSC-derived BMP4 and tumor-derived HH preventing enrichment of CSCs and reversing chemotherapy resistance. The impact of HH inhibition was only seen in CA-MSC-containing tumors, indicating the importance of a humanized stroma. These results are reciprocal to findings in pancreatic and bladder cancer, suggesting HH signaling effects are tumor tissue specific warranting careful investigation in each tumor type. Collectively, we define a critical positive feedback loop between CA-MSC-derived BMP4 and ovarian tumor cell-secreted HH and present evidence for the further investigation of HH as a clinical target in ovarian cancer.

Activation, homing, and role of the mesenchymal stem cells in the inflammatory environment

Human mesenchymal stem cells (MSCs) are considered to be a promising source of cells in regenerative medicine. They have large potential to differentiate into various tissue-specific populations and may be isolated from diverse tissues in desired quantities. As cells of potential autologous origin, they allow recipients to avoid the alloantigen responses. They also have the ability to create immunomodulatory microenvironment, and thus help to minimize organ damage caused by the inflammation and cells activated by the immune system. Our knowledge about the reparative, regenerative, and immunomodulatory properties of MSCs is advancing. At present, there is a very comprehensible idea on how MSCs affect the immune system, particularly in relation to the tissue and organ damage on immunological basis. Hitherto a number of effective mechanisms have been described by which MSCs influence the immune responses. These mechanisms include a secretion of soluble bioactive agents, an induction of regulatory T cells, modulation of tolerogenic dendritic cells, as well as induction of anergy and apoptosis. MSCs are thus able to influence both innate and adaptive immune responses. Soluble factors that are released into local microenvironment with their subsequent paracrine effects are keys to the activation. As a result, activated MSCs contribute to the restoration of damaged tissues or organs through various mechanisms facilitating reparative and regenerative processes as well as through immunomodulation itself and differentiation into the cells of the target tissue.

Mesenchymal Stromal Cells Can Regulate the Immune Response in the Tumor Microenvironment

The tumor microenvironment is a good target for therapy in solid tumors and hematological malignancies. Indeed, solid tumor cells' growth and expansion can influence neighboring cells' behavior, leading to a modulation of mesenchymal stromal cell (MSC) activities and remodeling of extracellular matrix components. This leads to an altered microenvironment, where reparative mechanisms, in the presence of sub-acute inflammation, are not able to reconstitute healthy tissue. Carcinoma cells can undergo epithelial mesenchymal transition (EMT), a key step to generate metastasis; these mesenchymal-like cells display the functional behavior of MSC. Furthermore, MSC can support the survival and growth of leukemic cells within bone marrow participating in the leukemic cell niche. Notably, MSC can inhibit the anti-tumor immune response through either carcinoma-associated fibroblasts or bone marrow stromal cells. Experimental data have indicated their relevance in regulating cytolytic effector lymphocytes of the innate and adaptive arms of the immune system. Herein, we will discuss some of the evidence in hematological malignancies and solid tumors. In particular, we will focus our attention on the means by which it is conceivable to inhibit MSC-mediated immune suppression and trigger anti-tumor innate immunity.

Prolongation of Cardiac Allograft Survival by Endometrial Regenerative Cells: Focusing on B-Cell Responses

Endometrial regenerative cells (ERCs) have been recently evaluated as an attractive candidate source for emerging stem cell therapies in immunosuppression, but their role in immunoregulation is not fully understood. The present study was designed to investigate their effects, especially on B-cell responses in heart transplantation. In this study, ERCs were noninvasively obtained from menstrual blood. Heart transplantation was performed between C57BL/6 (H-2^b ) donor mice and BALB/c (H-2^d ) recipients. B-cell activation and antibody levels were determined using fluorescence-activated cell sorting, enzyme-linked immunosorbent assay and ELISpot. In this study, we demonstrated that ERCs negatively regulated B-cell maturation and activation in vitro without affecting their viability. ERC treatment prolonged cardiac allograft survival in mice, which was correlated with a decrease in IgM and IgG deposition and circulating antidonor antibodies, as well as with reduction in frequencies of antidonor antibody-secreting CD19⁺ B cells. In addition, upon ex vivo stimulation, B cells from ERC-treated heart transplant recipients had impaired proliferation capacity and produced less IgM and IgG antibody. Moreover, ERC treatment of mice receiving ovalbumin (OVA)-aluminum hydroxide vaccine resulted in significant lower numbers of anti-OVA IgG antibody-secreting splenic B cells and lower anti-OVA antibody titres. Our results indicate that therapeutic effects of ERCs may be attributed at least in part by their B-cell suppression and humoral response inhibition, suggesting the potential use of ERCs for attenuating antibody-mediated allograft rejection. Stem Cells Translational Medicine 2017;6:778-787.

Differentiation and transdifferentiation potentials of cancer stem cells

Tumor cells actively contribute to constructing their own microenvironment during tumorigenesis and tumor progression. The tumor microenvironment contains multiple types of stromal cells that work together with the extracellular matrix and local and systemic factors to coordinately contribute to tumor initiation and progression. Tumor cells and their stromal compartments acquire many genetic and/or epigenetic alternations to facilitate tumor growth and metastasis. The cancer stem cell (CSC) concept has been widely applied to interpreting tumor initiation, growth, metastasis, dormancy and relapse. CSCs have differentiation abilities to generate the original lineage cells that are similar to their normal stem cell counterparts. Interestingly, recent evidence demonstrates that CSCs also have the potential to transdifferentiate into vascular endothelial cells and pericytes, indicating that CSCs can transdifferentiate into other lineage cells for promoting tumor growth and metastasis in some tissue contexts instead of only recruiting stromal cells from local or distant tissues. Although the transdifferentiation of CSCs into tumor stromal cells provides a new dimension that explains tumor heterogeneity, many aspects of CSC transdifferentiation remain elusive. In this review, we summarize the multi-lineage differentiation and transdifferentiation potentials of CSCs as well as discuss their potential contributions to tumor heterogeneity and tumor microenvironment in tumor progression.

Engineered Mesenchymal Stem Cells as an Anti-Cancer Trojan Horse

Cell-based gene therapy holds a great promise for the treatment of human malignancy. Among different cells, mesenchymal stem cells (MSCs) are emerging as valuable anti-cancer agents that have the potential to be used to treat a number of different cancer types. They have inherent migratory properties, which allow them to serve as vehicles for delivering effective therapy to isolated tumors and metastases. MSCs have been engineered to express anti-proliferative, pro-apoptotic, and anti-angiogenic agents that specifically target different cancers. Another field of interest is to modify MSCs with the cytokines that activate pro-tumorigenic immunity or to use them as carriers for the traditional chemical compounds that possess the properties of anti-cancer drugs. Although there is still controversy about the exact function of MSCs in the tumor settings, the encouraging results from the preclinical studies of MSC-based gene therapy for a large number of tumors support the initiation of clinical trials.

Interleukin-6 receptor in spindle-shaped stromal cells, a prognostic determinant of early breast cancer

Spindle-shaped stromal cells, like carcinoma-associated fibroblasts and mesenchymal stem cells, influence tumor behavior and can serve as parameters in the clinical diagnosis, therapy, and prognosis of early breast cancer. Therefore, the aim of this study is to explore the clinicopathological significance of tumor necrosis factor-related apoptosis-induced ligand (TRAIL) receptors (Rs) 2 and 4 (TRAIL-R2 and R4), and interleukin-6 R (IL-6R) in spindle-shaped stromal cells, not associated with the vasculature, as prognostic determinants of early breast cancer patients. Receptors are able to trigger the migratory activity, among other functions, of these stromal cells. We conducted immunohistochemical analysis for the expression of these receptors in spindle-shaped stromal cells, not associated with the vasculature, of primary tumors from early invasive breast cancer patients, and analyzed their association with clinicopathological characteristics. Here, we demonstrate that the elevated levels of TRAIL-R2, TRAIL-R4, and IL-6R in these stromal cells were significantly associated with a higher risk of metastatic occurrence (p = 0.034, 0.026, and 0.006; respectively). Moreover, high expression of TRAIL-R4 was associated with shorter disease-free survival and metastasis-free survival (p = 0.013 and 0.019; respectively). Also, high expression of IL-6R was associated with shorter disease-free survival, metastasis-free survival, and overall survival (p = 0.003, 0.001, and 0.003; respectively). Multivariate analysis showed that IL-6R expression was an independent prognostic factor for disease-free survival and metastasis-free survival (p = 0.035). This study is the first to demonstrate that high levels of IL-6R expression in spindle-shaped stromal cells, not associated with the vasculature, could be used to identify early breast cancer patients with poor outcomes.

Harnessing mesenchymal stem cell homing as an anticancer therapy

INTRODUCTION

Mesenchymal stromal cells (MSCs) are non-hematopoietic progenitor cells that have been exploited as vehicles for cell-based cancer therapy. The general approach is based on the innate potential of adoptively applied MSC to undergo facilitated recruitment to malignant tissue. MSC from different tissue sources have been engineered using a variety of therapy genes that have shown efficacy in solid tumor models.

AREAS COVERED

In this review we will focus on the current developments of MSC-based gene therapy, in particular the diverse approaches that have been used for MSCs-targeted tumor therapy. We also discuss some outstanding issues and general prospects for their clinical application.

EXPERT OPINION

The use of modified mesenchymal stem cells as therapy vehicles for the treatment of solid tumors has progressed to the first generation of clinical trials, but the general field is still in its infancy. There are many questions that need to be addressed if this very complex therapy approach is widely applied in clinical settings. More must be understood about the mechanisms underlying tumor tropism and we need to identify the optimal source of the cells used. Outstanding issues also include the therapy transgenes used, and which tumor types represent viable targets for this therapy.

Extracellular vesicles derived from renal cancer stem cells induce a pro-tumorigenic phenotype in mesenchymal stromal cells

Renal carcinomas have been shown to contain a population of cancer stem cells (CSCs) that present self-renewing capacity and support tumor growth and metastasis. CSCs were shown to secrete large amount of extracellular vesicles (EVs) that can transfer several molecules (proteins, lipids and nucleic acids) and induce epigenetic changes in target cells. Mesenchymal Stromal Cells (MSCs) are susceptible to tumor signalling and can be recruited to tumor regions. The precise role of MSCs in tumor development is still under debate since both pro- and anti-tumorigenic effects have been reported. In this study we analysed the participation of renal CSC-derived EVs in the interaction between tumor and MSCs. We found that CSC-derived EVs promoted persistent phenotypical changes in MSCs characterized by an increased expression of genes associated with cell migration (CXCR4, CXCR7), matrix remodeling (COL4A3), angiogenesis and tumor growth (IL-8, Osteopontin and Myeloperoxidase). EV-stimulated MSCs exhibited in vitro an enhancement of migration toward the tumor conditioned medium. Moreover, EV-stimulated MSCs enhanced migration of renal tumor cells and induced vessel-like formation. In vivo, EV-stimulated MSCs supported tumor development and vascularization, when co-injected with renal tumor cells. In conclusion, CSC-derived EVs induced phenotypical changes in MSCs that are associated with tumor growth.

Decellularized spleen matrix for reengineering functional hepatic-like tissue based on bone marrow mesenchymal stem cells

BACKGROUND AND AIMS

Decellularized liver matrix (DLM) hold great potential for reconstructing functional hepatic-like tissue (HLT) based on reseeding of hepatocytes or stem cells, but the shortage of liver donors is still an obstacle for potential application. Therefore, an appropriate alternative scaffold is needed to expand the donor pool. In this study, we explored the effectiveness of decellularized spleen matrix (DSM) for culturing of bone marrow mesenchymal stem cells (BMSCs), and promoting differentiation into hepatic-like cells.

METHODS

Rats' spleen were harvested for DSM preparation by freezing/thawing and perfusion procedure. Then the mesenchymal stem cells derived from rat bone marrow were reseeded into DSM for dynamic culture and hepatic differentiation by a defined induction protocol.

RESULTS

The research found that DSM preserved a 3-dimensional porous architecture, with native extracellular matrix and vascular network which was similar to DLM. The reseeded BMSCs in DSM differentiated into functional hepatocyte-like cells, evidenced by cytomorphology change, expression of hepatic-associated genes and protein markers, glycogen storage, and indocyanine green uptake. The albumin production (2.74±0.42 vs. 2.07±0.28 pg/cell/day) and urea concentration (75.92±15.64 vs. 52.07±11.46 pg/cell/day) in DSM group were remarkably higher than tissue culture flasks (TCF) group over the same differentiation period, P< 0.05.

CONCLUSION

This present study demonstrated that DSM might have considerable potential in fabricating hepatic-like tissue, particularly because it can facilitate hepatic differentiation of BMSCs which exhibited higher level and more stable functions.

Melanoma educates mesenchymal stromal cells towards vasculogenic mimicry

Accumulating evidence suggests that mesenchymal stromal cells (MSCs) are recruited to the tumor, and promote tumor development and growth. The present study was performed to investigate the communication between aggressive melanoma and MSCs in vasculogenic mimicry (VM). Normal human MSCs plated on Matrigel were unable to form capillary-like structures (CLSs). By contrast, MSCs co-cultured with aggressive melanoma cell lines, namely, Mel Cher, Mel Kor and Mel P, generated CLSs. Significantly, MSCs co-cultured with poorly aggressive melanoma cells, namely, Mel Me, failed to form CLSs. To identify factors responsible for VM, the effects of vascular endothelial growth factor A (VEGFA), pro-epidermal growth factor, basic fibroblast growth factor and stromal cell-derived factor 1α on the formation of CLSs by MSCs were tested. VM was induced by the addition of VEGFA, whereas other cytokines were inefficient. To confirm the hypothesis that aggressive tumor cells can increase the vasculogenic ability of MSCs, a standard B16/F10 mouse melanoma test system was used. MSCs isolated from the adipose tissues of C57BL/6 mice with melanoma formed a vascular-like network on Matrigel, whereas MSCs from healthy mice failed to form such structures. This study provides the first direct evidence that melanoma tumors educate MSCs to engage in VM. The education may occur distantly. These findings offer promise for novel therapeutic directions in the treatment of metastatic melanoma.

Imaging of human glioblastoma cells and their interactions with mesenchymal stem cells in the zebrafish (Danio rerio) embryonic brain

BACKGROUND

An attractive approach in the study of human cancers is the use of transparent zebrafish (Danio rerio) embryos, which enable the visualization of cancer progression in a living animal.

MATERIALS AND METHODS

We implanted mixtures of fluorescently labeled glioblastoma (GBM) cells and bonemarrow-derived mesenchymal stem cells (MSCs) into zebrafish embryos to study the cellular pathways of their invasion and the interactions between these cells in vivo.

RESULTS

By developing and applying a carbocyanine-dye-compatible clearing protocol for observation of cells in deep tissues, we showed that U87 and U373 GBM cells rapidly aggregated into tumor masses in the ventricles and midbrain hemispheres of the zebrafish embryo brain, and invaded the central nervous system, often using the ventricular system and the central canal of the spinal cord. However, the GBM cells did not leave the central nervous system. With co-injection of differentially labeled cultured GBM cells and MSCs, the implanted cells formed mixed tumor masses in the brain. We observed tight associations between GBM cells and MSCs, and possible cell-fusion events. GBM cells and MSCs used similar invasion routes in the central nervous system.

CONCLUSIONS

This simple model can be used to study the molecular pathways of cellular processes in GBM cell invasion, and their interactions with various types of stromal cells in double or triple cell co-cultures, to design anti-GBM cell therapies that use MSCs as vectors.

Wnt5a-Ror2 signaling in mesenchymal stem cells promotes proliferation of gastric cancer cells by activating CXCL16-CXCR6 axis

Wnt5a‐Ror2 signaling has been shown to play important roles in promoting aggressiveness of various cancer cells in a cell‐autonomous manner. However, little is known about its function in cancer‐associated stromal cells, including mesenchymal stem cells (MSCs). Thus, we examined the role of Wnt5a‐Ror2 signaling in bone marrow‐derived MSCs in regulating proliferation of undifferentiated gastric cancer cells. Coculture of a gastric cancer cell line, MKN45, with MSCs either directly or indirectly promotes proliferation of MKN45 cells, and suppressed expression of Ror2 in MSCs prior to coculture inhibits enhanced proliferation of MKN45 cells. In addition, conditioned media from MSCs, treated with control siRNA, but not siRNAs against Ror2, can enhance proliferation of MKN45 cells. Interestingly, it was found that expression of CXCL16 in MSCs is augmented by Wnt5a‐Ror2 signaling, and that recombinant chemokine (C‐X‐C motif) ligand (CXCL)16 protein can enhance proliferation of MKN45 cells in the absence of MSCs. In fact, suppressed expression of CXCL16 in MSCs or an addition of a neutralizing antibody against CXCL16 fails to promote proliferation of MKN45 cells in either direct or indirect coculture with MSCs. Importantly, we show that MKN45 cells express chemokine (C‐X‐C motif) receptor (CXCR)6, a receptor for CXCL16, and that suppressed expression of CXCR6 in MKN45 cells results in a failure of its enhanced proliferation in either direct or indirect coculture with MSCs. These findings indicate that Wnt5a‐Ror2 signaling enhances expression of CXCL16 in MSCs and, as a result, enhanced secretion of CXCL16 from MSCs might act on CXCR6 expressed on MKN45, leading to the promotion of its proliferation.

BET protein inhibitor JQ1 inhibits growth and modulates WNT signaling in mesenchymal stem cells

BACKGROUND

Efficacy and safety of anticancer drugs are traditionally studied using cancer cell lines and animal models. The thienodiazepine class of BET inhibitors, such as JQ1, has been extensively studied for the potential treatment of hematological malignancies and several small molecules belonging to this class are currently under clinical investigation. While these compounds are well known to inhibit cancer cell growth and cause apoptosis, their effects on stem cells, particularly mesenchymal stem cells (MSCs), which are important for regeneration of damaged cells and tissues, are unknown. In this study we employed umbilical cord derived MSCs as a model system to evaluate the safety of JQ1.

METHODS

Cord derived MSCs were treated with various doses of JQ1 and subjected to cell metabolic activity, apoptosis, and cell cycle analyses using MTT assay, Annexin-V/FITC and PI staining, and flow cytometry, respectively. The effect of JQ1 on gene expression was determined using microarray and quantitative real-time reverse transcriptase polymerase chain reaction analysis. Furthermore, protein expression of apoptotic and neuronal markers was carried out using western blot and immunostaining, respectively.

RESULTS

Our results showed that JQ1 inhibited cell growth and caused cell cycle arrest in G1 phase but did not induce apoptosis or senescence. JQ1 also down-regulated genes involved in self-renewal, cell cycle, DNA replication, and mitosis, which may have negative implications on the regenerative potential of MSCs. In addition, JQ1 interfered with signaling pathways by down regulating the expression of WNT, resulting in limiting the self-renewal. These results suggest that anticancer agents belonging to the thienodiazepine class of BET inhibitors should be carefully evaluated before their use in cancer therapy.

CONCLUSIONS

This study revealed for the first time that JQ1 adversely affected MSCs, which are important for repair and regeneration. JQ1 specifically modulated signal transduction and inhibited growth as well as self-renewal. These findings suggest that perinatal MSCs could be used to supplement animal models for investigating the safety of anticancer agents and other drugs.

Role of a Preorganized Scaffold Presenting Four Residues of a GM-3 Lactone Mimetic on Melanoma Progression

Two tetravalent architectures, the glycocalix 7 and the RAFT 9, presenting four residues of a GM-3 ganglioside lactone mimetic, target the host compartment of melanoma and significantly abrogate the effect induced by cancer-associated fibroblasts (CAFs) contact + hypoxia in the motility and invasiveness of tumor cells. The data reported support the involvement of glycosphingolipids (GSLs) in hypoxia and show an interesting role played by compound 9 in targeting melanoma cells thereby interfering with melanoma progression. The unprecedented findings reported for the glycocluster 9 may contribute to the understanding of the critical and complex interactions between tumor cells and their local environment paving the way for new therapeutic agents.

Bone marrow microenvironment modulation of acute lymphoblastic leukemia phenotype

Acute lymphoblastic leukemia (ALL) treatment regimens have dramatically improved the survival of ALL patients. However, chemoresistant minimal residual disease that persists following cessation of therapy contributes to aggressive relapse. The bone marrow microenvironment (BMM) is an established "site of sanctuary" for ALL, as well as myeloid-lineage hematopoietic disease, with signals in this unique anatomic location contributing to drug resistance. Several models have been developed to recapitulate the interactions between the BMM and ALL cells. However, many in vitro models fail to accurately reflect the level of protection afforded to the most resistant subset of leukemic cells during coculture with BMM elements. Preclinical in vivo models have advantages, but can be costly, and are often not fully informed by optimal in vitro studies. We describe an innovative extension of 2-D coculture wherein ALL cells uniquely interact with bone marrow-derived stromal cells. Tumor cells in this model bury beneath primary human bone marrow-derived stromal cells or osteoblasts, termed "phase dim" ALL, and exhibit a unique phenotype characterized by altered metabolism, distinct protein expression profiles, increased quiescence, and pronounced chemotherapy resistance. Investigation focused on the phase dim subpopulation may more efficiently inform preclinical design and investigation of the minimal residual disease and relapse that arise from BMM-supported leukemic tumor cells.

Microencapsulation of Neuroblastoma Cells and Mesenchymal Stromal Cells in Collagen Microspheres: A 3D Model for Cancer Cell Niche Study

There is a growing trend for researchers to use in vitro 3D models in cancer studies, as they can better recapitulate the complex in vivo situation. And the fact that the progression and development of tumor are closely associated to its stromal microenvironment has been increasingly recognized. The establishment of such tumor supportive niche is vital in understanding tumor progress and metastasis. The mesenchymal origin of many cells residing in the cancer niche provides the rationale to include MSCs in mimicking the niche in neuroblastoma. Here we co-encapsulate and co-culture NBCs and MSCs in a 3D in vitro model and investigate the morphology, growth kinetics and matrix remodeling in the reconstituted stromal environment. Results showed that the incorporation of MSCs in the model lead to accelerated growth of cancer cells as well as recapitulation of at least partially the tumor microenvironment in vivo. The current study therefore demonstrates the feasibility for the collagen microsphere to act as a 3D in vitro cancer model for various topics in cancer studies.

Cancer associated fibroblasts in hematological malignancies

Tumor microenvironment plays an important role in cancer initiation and progression. In hematological malignancies, the bone marrow represents the paradigmatic anatomical site in which tumor microenvironment expresses its morphofunctional features. Among the cells participating in the composition of this microenvironment, cancer associated fibrobasts (CAFs) have received less attention in hematopoietic tumors compared to solid cancers. In this review article, we discuss the involvement of CAFs in progression of hematological malignancies and the potential targeting of CAFs in a therapeutic perspective.

Uncovering the dual role of RHAMM as an HA receptor and a regulator of CD44 expression in RHAMM-expressing mesenchymal progenitor cells

The interaction of hyaluronan (HA) with mesenchymal progenitor cells impacts trafficking and fate after tissue colonization during wound repair and these events contribute to diseases such as cancer. How this interaction occurs is poorly understood. Using 10T½ cells as a mesenchymal progenitor model and fluorescent (F-HA) or gold-labeled HA (G-HA) polymers, we studied the role of two HA receptors, RHAMM and CD44, in HA binding and uptake in non-adherent and adherent mesenchymal progenitor (10T½) cells to mimic aspects of cell trafficking and tissue colonization. We show that fluorescent labeled HA (F-HA) binding/uptake was high in non-adherent cells but dropped over time as cells became increasingly adherent. Non-adherent cells displayed both CD44 and RHAMM but only function-blocking anti-RHAMM and not anti-CD44 antibodies significantly reduced F-HA binding/uptake. Adherent cells, which also expressed CD44 and RHAMM, primarily utilized CD44 to bind to F-HA since anti-CD44 but not anti-RHAMM antibodies blocked F-HA uptake. RHAMM overexpression in adherent 10T½ cells led to increased F-HA uptake but this increased binding remained CD44 dependent. Further studies showed that RHAMM-transfection increased CD44 mRNA and protein expression while blocking RHAMM function reduced expression. Collectively, these results suggest that cellular microenvironments in which these receptors function as HA binding proteins differ significantly, and that RHAMM plays at least two roles in F-HA binding by acting as an HA receptor in non-attached cells and by regulating CD44 expression and display in attached cells. Our findings demonstrate adhesion-dependent mechanisms governing HA binding/ uptake that may impact development of new mesenchymal cell-based therapies.

Priming hMSCs with a putative anti-cancer compound, myrtucommulone-a: a way to harness hMSC cytokine expression via modulating PI3K/Akt pathway?

Tumour microenvironment is a key factor for cancer growth and metastasis. Tumour surrounding tissue is known to include high number of mesenchymal stem cells which have been thought to have a role in regulating cancer cell behaviour via paracrine signalling. Therefore, modulating human mesenchymal stem cell (hMSC) secretome is highly significant for controlling and treating disease. Since common therapeutic agents are known to enhance cancer resistance, there is a strong urge to define novel agents for developing cell-based therapies. In the present study, we aimed at investigating the effect of active compounds, myrtucommulone-A (MC-A) and thymoquinone (TQ), on hMSC cytokine expression. Our data revealed that MC-A treatment have significantly altered cytokine expression in hMSCs. Upon MC-A treatment, hMSCs decreased the expression levels of various cytokines including TNF-α, VEGF, IL-6, IL-8 and FGF-2. hMSC conditioned medium (CM) primed with MC-A decreased the proliferation, migration ability and clonogenicity of bladder cancer cells and breast cancer cells in comparison to non-primed hMSC medium and hMSC medium primed with TQ. To the best of our knowledge, this study is the first report showing the effects of active compounds, MC-A and TQ, on hMSCs and therefore valuable for highlighting the potential use of active compounds in combination with hMSCs for cell-based targeted cancer therapy.

Gastric cancer-derived mesenchymal stem cells prompt gastric cancer progression through secretion of interleukin-8

Background

Bone marrow mesenchymal stem cells (BM-MSCs) have been identified to be closely associated with tumor growth and progression. However, the roles of tumor-resident MSCs in cancer have not been thoroughly clarified. This study was to investigate the regulating effect of gastric cancer-derived MSCs (GC-MSCs) on gastric cancer and elucidate the underlying mechanism.

Methods

GC-MSCs were isolated from primary human gastric cancer tissues and characterized. The effect of GC-MSCs on gastric cancer cell proliferation was analyzed by MTT assay and colony formation assay. Transwell migration assay was performed to evaluate the influence of GC-MSCs in gastric cancer cell migration. The regulating effects of interactions between gastric cancer cells and GC-MSCs on their pro-angiogenic abilities were analyzed in a co-culture system, with the expression, and secretion of pro-angiogenic factors detected by RT-PCR and Luminex assay. Tube formation assay was used to further validate the angiogenic capability of gastric cancer cells or GC-MSCs. Cytokine profiles in the supernatant of GC-MSCs were screened by Luminex assay and neutralizing antibody was used to identify the key effective cytokines. The activations of Akt and Erk1/2 in gastric caner cells were detected by Western blot.

Results

GC-MSC treatment enhanced the proliferation and migration of BGC-823 and MKN-28 cells, which was more potently than MSCs from adjacent non-cancerous tissues (GCN-MSCs) or bone marrow (BM-MSCs). Higher expression levels of pro-angiogenic factors were detected in GC-MSCs than GCN-MSCs or BM-MSCs. After 10 % GC-MSC-CM treatment, BGC-823, and MKN-28 cells expressed increased levels of pro-angiogenic factors and facilitated tube formation more potently than cancer cells alone. Furthermore, GC-MSCs produced an extremely higher level of interleukin-8 (IL-8) than GCN-MSCs or BM-MSCs. Blockade of IL-8 by neutralizing antibody significantly attenuated the tumor-promoting effect of GC-MSCs. In addition, 10 % CM of IL-8-secreted GC-MSCs induced the activations of Akt or Erk1/2 pathway in BGC-823 and MKN-28 cells.

Conclusion

Tumor-resident GC-MSCs promote gastric cancer growth and progression more efficiently than GCN-MSCs or BM-MSCs through a considerable secretion of IL-8, which could be a possible target for gastric cancer therapy.

Human Mesenchymal Stromal Cells Transplantation May Enhance or Inhibit 4T1 Murine Breast Adenocarcinoma through Different Approaches

The use of Mesenchymal Stromal Cells (MSCs) aiming to treat cancer has shown very contradictory results. In an attempt to clarify the contradictory results reported in the literature and the possible role of human fallopian tube Mesenchymal Stromal Cells (htMSCs) against breast cancer, the aim of this study was to evaluate the clinical effect of htMSCs in murine mammary adenocarcinoma using two different approaches: (1) coinjections of htMSCs and 4T1 murine tumor cell lineage and (2) injections of htMSCs in mice at the initial stage of mammary adenocarcinoma development. Coinjected animals had a more severe course of the disease and a reduced survival, while tumor-bearing animals treated with 2 intraperitoneal injections of 10⁶ htMSCs showed significantly reduced tumor growth and increased lifespan as compared with control animals. Coculture of htMSCs and 4T1 tumor cells revealed an increase in IL-8 and MCP-1 and decreased VEGF production. For the first time, we show that MSCs isolated from a single source and donor when injected in the same animal model and tumor can lead to opposite results depending on the experimental protocol. Also, our results demonstrated that htMSCs can have an inhibitory effect on the development of murine mammary adenocarcinoma.