Effects of inflammatory factors on mesenchymal stem cells and their role in the promotion of tumor angiogenesis in colon cancer

The GroEL protein of Porphyromonas gingivalis accelerates tumor growth by enhancing endothelial progenitor cell function and neovascularization

Porphyromonas gingivalis is a bacterial species that causes destruction of periodontal tissues. Additionally, previous evidence indicates that GroEL from P. gingivalis may possess biological activities involved in systemic inflammation, especially inflammation involved in the progression of periodontal diseases. The literature has established a relationship between periodontal disease and cancer. However, it is unclear whether P. gingivalis GroEL enhances tumor growth. Here, we investigated the effects of P. gingivalis GroEL on neovasculogenesis in C26 carcinoma cell-carrying BALB/c mice and chick eggs in vivo as well as its effect on human endothelial progenitor cells (EPC) in vitro. We found that GroEL treatment accelerated tumor growth (tumor volume and weight) and increased the mortality rate in C26 cell-carrying BALB/c mice. GroEL promoted neovasculogenesis in chicken embryonic allantois and increased the circulating EPC level in BALB/c mice. Furthermore, GroEL effectively stimulated EPC migration and tube formation and increased E-selectin expression, which is mediated by eNOS production and p38 mitogen-activated protein kinase activation. Additionally, GroEL may enhance resistance against paclitaxel-induced cell cytotoxicity and senescence in EPC. In conclusion, P. gingivalis GroEL may act as a potent virulence factor, contributing to the neovasculogenesis of tumor cells and resulting in accelerated tumor growth.

Peripheral Blood-Derived Mesenchymal Stromal Cells Promote Angiogenesis via Paracrine Stimulation of Vascular Endothelial Growth Factor Secretion in the Equine Model

Mesenchymal stromal cells (MSCs) have received much attention as a potential treatment of ischemic diseases, including ischemic tissue injury and cardiac failure. The beneficial effects of MSCs are thought to be mediated by their ability to provide proangiogenic factors, creating a favorable microenvironment that results in neovascularization and tissue regeneration. To study this in more detail and to explore the potential of the horse as a valuable translational model, the objectives of the present study were to examine the presence of angiogenic stimulating factors in the conditioned medium (CM) of peripheral blood-derived equine mesenchymal stromal cells (PB-MSCs) and to study their in vitro effect on angiogenesis-related endothelial cell (EC) behavior, including proliferation and vessel formation. Our salient findings were that CM from PB-MSCs contained significant levels of several proangiogenic factors. Furthermore, we found that CM could induce angiogenesis in equine vascular ECs and confirmed that endothelin-1, insulin growth factor binding protein 2, interleukin-8, and platelet-derived growth factor-AA, but not urokinase-type plasminogen activator, were responsible for this enhanced EC network formation by increasing the expression level of vascular endothelial growth factor-A, an important angiogenesis stimulator.

Cell-based therapy for acute and chronic liver failures: distinct diseases, different choices

Cell-based therapies (CBTs) are considered the effective approaches to treat liver failure. However, which cell type is the most suitable source of CBTs for acute liver failure (ALF) or chronic liver failure (CLF) remains unclear. To investigate this, mature hepatocytes in adult liver (adult HCs), fetal liver cells (FLCs), induced hepatic stem cells (iHepSCs) and bone marrow derived mesenchymal stromal cells (BMSCs) were used to CBTs for ConA-induced ALF and Fah-deficient induced CLF in mice. The results showed that only BMSCs remitted liver damage and rescued ALF in ConA-treated mice. In this process, BMSCs inhibited ConA-induced inflammatory response by decreasing the mRNA expressions of TNF-α, IFN-γ and FasL and increasing IL-10 mRNA expression. However, in the CLF model, not BMSCs but adult HCs transplantation lessened liver injury, recovered liver function and rescued the life of Fah-/- mice after NTBC withdrawal. Further study showed that adult HCs offered more effective liver regeneration compared to other cells in Fah-/- mice without NTBC. These results demonstrated that BMSCs and adult HCs are the optimal sources of CBTs for ConA-induced ALF and Fah-deficient induced CLF in mice, respectively. This finding deepens our understanding about how to select a proper CBT for different liver failure.

CD133-positive cancer stem cells from Colo205 human colon adenocarcinoma cell line show resistance to chemotherapy and display a specific metabolomic profile

During the past decade, cancer stem-like cells (CSCs) have drawn substantial interest in cancer research since they have been described as major targets to improve treatment of tumors and to prevent recurrence and metastasis. In this paper, we report on the search for CSCs within the Colo205 human adenocarcinoma cell line. We describe that CD133 (prominin) was the only reliable marker for the isolation and characterization of CSCs within a Colo205 cell population. CD133-positive cells displayed many CSC characteristics, such as tumorsphere formation ability, expression of early-stage development markers, high invasiveness, raised tumor initiation potential and resistance to cisplatin chemotherapy treatment. In vitro analyses also highlighted a specific metabolomic profile of CD133-positive cells and we concluded that the chemotherapy resistance of CSCs could be related to the quiescence of such cells associated with their reduced metabolism. Furthermore, in vivo metabolome analyses suggested that a high level of circulating glutathione molecules could also promote treatment resistance. From the perspective of metabolomics, we also discuss the controversial use of serum-free in vitro cultures for CSC enrichment prior to further phenotype characterization.

Bone marrow-derived mesenchymal stem cells drive lymphangiogenesis

It is now well accepted that multipotent Bone-Marrow Mesenchymal Stem Cells (BM-MSC) contribute to cancer progression through several mechanisms including angiogenesis. However, their involvement during the lymphangiogenic process is poorly described. Using BM-MSC isolated from mice of two different backgrounds, we demonstrate a paracrine lymphangiogenic action of BM-MSC both in vivo and in vitro. Co-injection of BM-MSC and tumor cells in mice increased the in vivo tumor growth and intratumoral lymphatic vessel density. In addition, BM-MSC or their conditioned medium stimulated the recruitment of lymphatic vessels in vivo in an ear sponge assay, and ex vivo in the lymphatic ring assay (LRA). In vitro, MSC conditioned medium also increased the proliferation rate and the migration of both primary lymphatic endothelial cells (LEC) and an immortalized lymphatic endothelial cell line. Mechanistically, these pro-lymphangiogenic effects relied on the secretion of Vascular Endothelial Growth Factor (VEGF)-A by BM-MSC that activates VEGF Receptor (VEGFR)-2 pathway on LEC. Indeed, the trapping of VEGF-A in MSC conditioned medium by soluble VEGF Receptors (sVEGFR)-1, -2 or the inhibition of VEGFR-2 activity by a specific inhibitor (ZM 323881) both decreased LEC proliferation, migration and the phosphorylation of their main downstream target ERK1/2. This study provides direct unprecedented evidence for a paracrine lymphangiogenic action of BM-MSC via the production of VEGF-A which acts on LEC VEGFR-2.

Human mesenchymal stromal cells transiently increase cytokine production by activated T cells before suppressing T-cell proliferation: effect of interferon-γ and tumor necrosis factor-α stimulation

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) suppress T-cell proliferation, especially after activation with inflammatory cytokines. We compared the dynamic action of unprimed and interferon (IFN)-γ plus tumor necrosis factor (TNF)-α-pretreated human bone marrow-derived MSCs on resting or activated T cells.

METHODS

MSCs were co-cultured with allogeneic peripheral blood mononuclear cells (PBMCs) at high MSC-to-PBMC ratios in the absence or presence of concomitant CD3/CD28-induced T-cell activation. The kinetic effects of MSCs on cytokine production and T-cell proliferation, cell cycle and apoptosis were assessed.

RESULTS

Unprimed MSCs increased the early production of IFN-γ and interleukin (IL)-2 by CD3/CD28-activated PBMCs before suppressing T-cell proliferation. In non-activated PBMC co-cultures, low levels of IL-2 and IL-10 synthesis were observed with MSCs in addition to low levels of CD69 expression by T cells and no T-cell proliferation. MSCs also decreased apoptosis in resting and activated T cells and inhibited the transition of these cells into the sub-G0/G1 and the S phases. With inhibition of indoleamine 2,3 dioxygenase, MSCs increased CD3/CD28-induced T-cell proliferation. After priming with IFN-γ plus TNF-α, MSCs were less potent at increasing cytokine production by CD3/CD28-activated PBMCs and more effective at inhibiting T-cell proliferation but had preserved anti-apoptotic functions.

CONCLUSIONS

Unprimed MSCs induce a transient increase in IFN-γ and IL-2 synthesis by activated T cells. Pre-treatment of MSCs with IFN-γ plus TNF-α may increase their effectiveness and safety in vivo.

TNFα and IL-1β influence the differentiation and migration of murine MSCs independently of the NF-κB pathway

INTRODUCTION

Mesenchymal stem cells (MSCs) have the ability to repair and regenerate tissue, home to sites of inflammation, and evade the host immune system. As such, they represent an attractive therapy for the treatment of autoimmune inflammatory diseases. However, results from in vivo murine studies in inflammatory arthritis have been conflicting, and this may be due to the genetic background of the MSCs used. It is known that the inflammatory milieu may influence properties of MSCs and that, in the case of human bone marrow-derived MSCs, this may be mediated by the nuclear factor-kappa-B (NF-κB) pathway. We sought to determine whether pro-inflammatory cytokines altered the differentiation and migration capacity of murine MSCs from different mouse strains and whether this was mediated by NF-κB.

METHODS

The differentiation and migration of FVB and BALB/c MSCs were carried out in the presence of varying concentrations of tumor necrosis factor-alpha (TNFα) and interleukin (IL)-1β, and the NF-κB pathway was inhibited in one of two ways: either by transduction of MSCs with an adenoviral vector expressing a super-repressor of NF-κB or by the addition of curcumin to culture media.

RESULTS

Both BALB/c and FVB MSCs were sensitive to the effect of pro-inflammatory cytokines in vitro. TNFα and IL-1β suppressed BALB/c osteogenesis and adipogenesis and FVB osteogenesis. The migration of both cell types toward media containing fetal bovine serum was augmented by pre-stimulation with either cytokine. In neither cell type were the cytokine effects reversed by abrogation of the NF-κB pathway.

CONCLUSIONS

These data show that murine MSCs from different genetic backgrounds may be influenced by an inflammatory milieu in a manner that is not mediated by NF-κB, as is the case for human MSCs. This is not mediated by NF-κB. These findings are important and should influence how in vivo trials of murine MSCs are interpreted and the future development of pre-clinical studies in inflammatory diseases.

Bone marrow mesenchymal stem cells ameliorate colitis-associated tumorigenesis in mice

BACKGROUND AND AIMS

Bone marrow-derived mesenchymal stem cell (MSC) is widely studied in inflammatory bowel disease (IBD) in basic and clinical research. However, patients with IBD have higher risk of developing colorectal cancer and MSC has dual effect on tumorigenesis. This study aims to evaluate the role of MSC on tumorigenesis of IBD.

METHODS

MSCs were isolated from the bone marrow of allogenic mice and identified by flow cytometry. Mice in the model of colitis-associated tumorigenesis induced by azoxymethane and dextran sulfate sodium were injected with MSCs. Colon length, spleen size and tumors formation were assessed macroscopically. Pro-inflammatory cytokines and STAT3 phosphorylation in colon tissues were analyzed.

RESULTS

MSCs ameliorated the severity of colitis associated tumorigenesis compared with PBS control, with attenuated weight loss, longer colons and smaller spleens. Tumor number and tumor load were significantly less in the MSC group while tumor size remained comparable. Histological assessment indicated MSCs could reduce histological damage of the colon tissue. Decreased expression of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6), and down-regulation of STAT3 phosphorylation in colon tissue were found after MSC treatment.

CONCLUSION

MSCs might ameliorate the tumorigenesis of inflammatory bowel disease by suppression of expression of pro-inflammatory cytokines and STAT3 activation.

Interferon-γ produced by tumor-infiltrating NK cells and CD4+ T cells downregulates TNFSF15 expression in vascular endothelial cells

Endothelial cells in an established vasculature secrete tumor necrosis factor superfamily-15 (TNFSF15; VEGI; TL1A) that functions as a negative modulator of neovascularization to maintain blood vessel stability. TNFSF15 gene expression diminishes at angiogenesis and inflammation sites such as in cancers and wounds. We reported previously that vascular endothelial growth factor and monocyte chemotactic protein-1 contribute to TNFSF15 downmodulation in ovarian cancer. Here we show that interferon-γ (IFNγ) suppresses TNFSF15 expression in human umbilical vein endothelial cells. This activity is mediated by IFNγ receptor and the transcription factor STAT1. Immunohistochemical analysis of ovarian cancer clinical specimens indicates that TNFSF15 expression diminishes while tumor vascularity increases in specimens with high-grades of IFNγ expression. Since tumor-infiltrating NK and CD4(+) T cells are the main sources of IFNγ in tumor lesions, we isolated these cells from peripheral blood of healthy individuals, treated the cells with ovarian cancer OVCAR3 cell-conditioned media, and found a onefold and tenfold increase of IFNγ production in NK and CD4(+) T cells, respectively, compared with that in vehicle-treated cells. These findings support the view that tumor-infiltrating NK and CD4(+) T cells under the influence of cancer cells significantly increase the production of IFNγ, which in turn inhibits TNFSF15 expression in vascular endothelial cells, shifting the balance of pro- and anti-angiogenic factors toward escalated angiogenesis potential in the tumor.

Mesenchymal stem cells contribute to the chemoresistance of hepatocellular carcinoma cells in inflammatory environment by inducing autophagy

BACKGROUND

Mesenchymal stem cells (MSCs) have been reported to play an important role in tumor growth. Inflammation is an important feature of hepatocellular carcinoma (HCC). Certain inflammatory cytokines produced in tumor microenvironment modulate functional activities of MSCs. At the present time, however, the role of MSCs in the development of HCC cell resistance to chemotherapy in the inflammatory microenvironment during tumor growth has not yet been identified.

METHODS

MTT and PI/Annexin V-FITC assay were employed to examine the proliferation and apoptosis of HCC cell lines. The expression of TGF-β are detected by Realtime PCR and Western blot. GFP tagged LC3 expression vector and electron microscopy are utilized to demonstrate the occurrence of autophagy.

RESULTS

We observed that MSCs pretreated with the combination of IFN-γ and TNF-α induced resistance to chemotherapy in HCC cell lines in both the in vitro and in vivo circumstances. Following exposure to conditioned medium of MSCs that were pre-treated with IFN-γ plus TNF-α, HCC cell line cells underwent autophagy which serves as a protective mechanism for HCC cells to resist the cell toxicity of chemotherapeutic agents. Treatment of HCC cell line cells with autophagy inhibitor effectively reversed the MSCs-induced resistance to chemotherapy in these cells. Stimulation with the combination of IFN-γ and TNF-α provoked expression of TGF-β by MSCs. MSCs-induced chemoresistance in HCC cell lines was correlated with the up-regulation of TGF-β expression by MSCs. Knockdown of TGF-β expression by MSCs with siRNA attenuated MSCs-induced chemoresistance in HCC cells.

CONCLUSIONS

These results suggest that increase in TGF-β expression by MSCs in the inflammatory microenvironment of HCC promotes the development of chemoresistance in HCC cells.

Oncogenic transformation tunes the cross-talk between mesenchymal stem cells and T lymphocytes

Stem cells from mesenchymal origin (MSC) exert a plethora of immunomodulatory effects. We created a neoplastic model based on in vitro step-wise transformation to assess whether oncogenic pathways have the capacity to mould the cross-talk of MSC and lymphocytes. Neoplastic MSC exhibit an increased inhibitory effect on T cell proliferation, either directly or mediated by myeloid derived suppressor cells. Additionally, transformation of MSC enhances T cell apoptosis without reducing either the percentage of CD25 expressing cells or the level of this protein expression. Malignant transformation drives MSC to lose dependency on nitric oxide for immunosuppression whilst increasing the constitutive production of PGE2. Our results indicate that oncogenesis tunes the interplay between MSC and immune cells, favoring cancer immune evasion.

Hallmarks in colorectal cancer: Angiogenesis and cancer stem-like cells

Carcinogenesis is a multistep process that requires the accumulation of various genetic and epigenetic aberrations to drive the progressive malignant transformation of normal human cells. Two major hallmarks of carcinogenesis that have been described are angiogenesis and the stem cell characteristic of limitless replicative potential. These properties have been targeted over the past decade in the development of therapeutic treatments for colorectal cancer (CRC), one of the most commonly diagnosed and lethal cancers worldwide. The treatment of solid tumor cancers such as CRC has been challenging due to the heterogeneity of the tumor itself and the chemoresistance of the malignant cells. Furthermore, the same microenvironment that maintains the pool of intestinal stem cells that contribute to the continuous renewal of the intestinal epithelia also provides the necessary conditions for proliferative growth of cancer stem-like cells. These cancer stem-like cells are responsible for the resistance to therapy and cancer recurrence, though they represent less than 2.5% of the tumor mass. The stromal environment surrounding the tumor cells, referred to as the tumor niche, also supports angiogenesis, which supplies the oxygen and nutrients needed for tumor development. Anti-angiogenic therapy, such as with bevacizumab, a monoclonal antibody against vascular-endothelial growth factor, significantly prolongs the survival of metastatic CRC patients. However, such treatments are not completely curative, and a large proportion of patient tumors retain chemoresistance or show recurrence. This article reviews the current knowledge regarding the molecular phenotype of CRC cancer cells, as well as discusses the mechanisms contributing to their maintenance. Future personalized therapeutic approaches that are based on the interaction of the carcinogenic hallmarks, namely angiogenic and proliferative attributes, could improve survival and decrease adverse effects induced by unnecessary chemotherapy.

Interleukin-18 produced by bone marrow-derived stromal cells supports T-cell acute leukaemia progression

Development of novel therapies is critical for T-cell acute leukaemia (T-ALL). Here, we investigated the effect of inhibiting the MAPK/MEK/ERK pathway on T-ALL cell growth. Unexpectedly, MEK inhibitors (MEKi) enhanced growth of 70% of human T-ALL cell samples cultured on stromal cells independently of NOTCH activation and maintained their ability to propagate in vivo. Similar results were obtained when T-ALL cells were cultured with ERK1/2-knockdown stromal cells or with conditioned medium from MEKi-treated stromal cells. Microarray analysis identified interleukin 18 (IL-18) as transcriptionally up-regulated in MEKi-treated MS5 cells. Recombinant IL-18 promoted T-ALL growth in vitro, whereas the loss of function of IL-18 receptor in T-ALL blast cells decreased blast proliferation in vitro and in NSG mice. The NFKB pathway that is downstream to IL-18R was activated by IL-18 in blast cells. IL-18 circulating levels were increased in T-ALL-xenografted mice and also in T-ALL patients in comparison with controls. This study uncovers a novel role of the pro-inflammatory cytokine IL-18 and outlines the microenvironment involvement in human T-ALL development.

Tpl2 inhibitors thwart endothelial cell function in angiogenesis and peritoneal dissemination

Angiogenesis is critical in the development of cancer, which involves several angiogenic factors in its peritoneal dissemination. The role of protein tumor progression locus 2 (Tpl2) in angiogenic factor-related endothelial cell angiogenesis is still unclear. To understand the precise mechanism(s) of Tpl2 inhibition in endothelial cells, this study investigated the role of Tpl2 in mediating angiogenic signals using in vitro, in vivo, and ex vivo models. Results showed that inhibition of Tpl2 inhibitor significantly reduced peritoneal dissemination in a mouse model by positron emission tomography/computed tomography imaging. Simultaneously, inhibiting Tpl2 blocked angiogenesis in tumor nodules and prevented angiogenic factor-induced proliferating cell nuclear antigen (PCNA) in endothelial cells. Vascular endothelial growth factor (VEGF) or chemokine (C-X-C motif) ligand 1 (CXCL1) increased Tpl2 kinase activity and phosphorylation in a dose- and time-dependent manner. Furthermore, Tpl2 inhibition or ablation by siRNA prevented the angiogenic signal-induced tube formation in Matrigel plug assay or aortic ring assay. Inhibiting Tpl2 also prevented the angiogenic factor-induced chemotactic motility and migration of endothelial cells. Tpl2 inhibition by CXCL1 or epidermal growth factor in endothelial cells was associated with inactivation of CCAAT/enhancer binding protein β, nuclear factor κ light-chain enhancer of activated B cells, and activating protein 1 and suppression of VEGF expression. Thus, Tpl2 inhibitors thwart Tpl2-regulated VEGF by inactivating transcription factors involved in angiogenic factor-triggered endothelial cell angiogenesis. These results suggest that the therapeutic inhibition of Tpl2 may extend beyond cancer and include the treatment of other diseases involving pathologic angiogenesis.

Gene expression profile of dermal mesenchymal stem cells from patients with psoriasis

BACKGROUND

Mesenchymal stem cells (MSCs) are likely involved in pathological processes of immune-related diseases, including psoriasis because of their immunoregulatory and pro-angiogenic effects, and the vascular proliferation, angiectasis and perivascular lymphocyte infiltration are known to be predominantly responsible for the pathological alterations in psoriasis.

OBJECTIVE

This study aimed to investigate the gene expression profile of dermal MSCs from patients with psoriasis.

METHODS

We isolated and expanded dermal MSCs from psoriatic patients and normal controls by using the attachment assay and conducted mRNA expression profile and gene ontology analyses using microarray.

RESULTS

The gene expression profile of MSCs from psoriatic derma was markedly different from the normal derma-derived MSCs; the angiogenesis-related genes such as vascular endothelial growth factor A, insulin-like growth factor-binding protein-5, and GATA6 showed significant differential expression.

CONCLUSIONS

These results indicate that MSCs from the derma of psoriasis patients might be involved in the early development of psoriasis because of their pro-angiogenic potential as well as the immunoregulatory effect.

Mesenchymal stem/stromal cells as a pharmacological and therapeutic approach to accelerate angiogenesis

Mesenchymal stem cells or multipotent stromal cells (MSCs) have initially captured attention in the scientific world because of their differentiation potential into osteoblasts, chondroblasts and adipocytes and possible transdifferentiation into neurons, glial cells and endothelial cells. This broad plasticity was originally hypothesized as the key mechanism of their demonstrated efficacy in numerous animal models of disease as well as in clinical settings. However, there is accumulating evidence suggesting that the beneficial effects of MSCs are predominantly caused by the multitude of bioactive molecules secreted by these remarkable cells. Numerous angiogenic factors, growth factors and cytokines have been discovered in the MSC secretome, all have been demonstrated to alter endothelial cell behavior in vitro and induce angiogenesis in vivo. As a consequence, MSCs have been widely explored as a promising treatment strategy in disorders caused by insufficient angiogenesis such as chronic wounds, stroke and myocardial infarction. In this review, we will summarize into detail the angiogenic factors found in the MSC secretome and their therapeutic mode of action in pathologies caused by limited blood vessel formation. Also the application of MSC as a vehicle to deliver drugs and/or genes in (anti-)angiogenesis will be discussed. Furthermore, the literature describing MSC transdifferentiation into endothelial cells will be evaluated critically.

The roles of mesenchymal stem cells in tumor inflammatory microenvironment

Tumor behavior is not entirely determined by tumor cells. Studies have demonstrated that a variety of non-tumor cells in the tumor microenvironment affect tumor behavior; thus, a new focus of cancer research has been the development of novel cancer treatment ideas and therapeutic targets based on the effects of these cells. Mesenchymal stem cells (MSCs) are an important component of the tumor microenvironment; however, previous studies have produced controversial results regarding whether MSCs promote or inhibit tumor growth and progression. In particular, Naïve MSCs and tumor-derived MSCs (T-MSCs) have different functions. Naïve MSCs could exert bidirectional effects on tumors because these cells can both promote and inhibit tumor progression while T-MSCs promote tumor progression due to influences from the tumor itself and from the inflammatory tumor microenvironment. As an unhealed wound, tumor produces a continuous source of inflammatory mediators and causes aggregation of numerous inflammatory cells, which constitute an inflammatory microenvironment. Inflammatory factors can induce homing of circulating MSCs and MSCs in adjacent tissues into tumors, which are then being “educated” by the tumor microenvironment to support tumor growth. T-MSCs could recruit more immune cells into the tumor microenvironment, increase the proportion of cancer stem cells and promote tumor angiogenesis, further supporting tumor progression. However, as plasticity is a fundamental feature of MSCs, MSCs can also inhibit tumors by activating various MSC-based signaling pathways. Studies of the mechanisms by which interactions among tumors, MSCs, and the inflammatory microenvironment occur and methods to disrupt these interactions will likely reveal new targets for cancer therapy.

Mesenchymal stromal cells induce epithelial-to-mesenchymal transition in human colorectal cancer cells through the expression of surface-bound TGF-β

Mesenchymal stem/stromal cells (MSC) are multipotent precursors endowed with the ability to home to primary and metastatic tumor sites, where they can integrate into the tumor-associated stroma. However, molecular mechanisms and outcome of their interaction with cancer cells have not been fully clarified. In this study, we investigated the effects mediated by bone marrow-derived MSC on human colorectal cancer (CRC) cells in vitro and in vivo. We found that MSC triggered epithelial-to-mesenchymal transition (EMT) in tumor cells in vitro, as indicated by upregulation of EMT-related genes, downregulation of E-cadherin and acquisition of mesenchymal morphology. These effects required cell-to-cell contact and were mediated by surface-bound TGF-β newly expressed on MSC upon coculture with tumor cells. In vivo tumor masses formed by MSC-conditioned CRC cells were larger and characterized by higher vessel density, decreased E-cadherin expression and increased expression of mesenchymal markers. Furthermore, MSC-conditioned tumor cells displayed increased invasiveness in vitro and enhanced capacity to invade peripheral tissues in vivo. Thus, by promoting EMT-related phenomena, MSC appear to favor the acquisition of an aggressive phenotype by CRC cells.

The response of breast cancer cells to mesenchymal stem cells: a possible role of inflammation by breast implants

BACKGROUND

Breast implants are widely used and at times might cause inflammation as a foreign body, followed by fibrous capsule formation around the implant. In cancer, the inflamed stroma is essential for preservation of the tumor. Mesenchymal stem cells can be recruited to sites of inflammation, and their role in cancer development is debated. The authors assessed the effects of inflammation caused by breast implants' effects on tumor.

METHODS

Mesenchymal stem cells were isolated from the fibrous capsules of women who underwent a second operation after 1 year (presenting inflammation) or after 20 years (not presenting inflammation) since initial surgery. After characterization, cells were co-cultured with MCF7, a breast cancer cell line. The expression of genes involved in oncogenesis, proliferation, and epithelial-to-mesenchymal transition was investigated, followed by Western blot analyses.

RESULTS

After co-culture with mesenchymal stem cells from the inflamed capsule, MCF7 induced a dose- and time-dependent increase in proliferation. Polymerase chain reaction analyses revealed a dysregulation of genes involved in oncogenesis, proliferation, and epithelial-to-mesenchymal transition. The subsequent evaluation by Western blot did not confirm these results, showing only a modest decrease in the expression of E-cadherin after co-culture with mesenchymal stem cells (both derived from inflamed or control capsules).

CONCLUSION

These data indicate that inflammation caused by breast implants partially affects proliferation of MCF7 but does not influence key mechanisms of tumor development.

Tumor-conditioned Gr-1(+)CD11b(+) myeloid cells induce angiogenesis through the synergistic action of CCL2 and CXCL16 in vitro

Gr-1(+)CD11b(+) cells can suppress innate and adaptive immunity, and the functional immunosuppressive characteristics of these cells can be modulated by the tumor microenvironment. Since Gr-1(+)CD11(+) cells are also involved in tumor-associated angiogenesis, we hypothesized that the angiogenic nature of Gr-1(+)CD11b(+) cells could be regulated by the tumor milieu. To address this hypothesis, we imitated a tumor microenvironment by exposing Gr-1(+)CD11b(+) cells isolated from spleen of 4T1 mammary carcinoma-bearing mice to tumor-conditioned medium. Supernatants from tumor-conditioned Gr-1(+)CD11b(+) cells significantly induced capillary-like tube formation and migration of human umbilical vein endothelial cells (HUVECs) compared to naive Gr-1(+)CD11b(+) cells. Incubation of Gr-1(+)CD11b(+) cells with tumor-conditioned medium induced production of pro-angiogenic chemokines CCL2 and CXCL16. Pretreatment with an anti-CCL2 antibody, but not an anti-CXCL16 antibody, suppressed the angiogenic effects of tumor-conditioned Gr-1(+)CD11b(+) cells on HUVECs. Simultaneous neutralization of CCL2 and CXCL16 significantly inhibited tube formation and migration of HUVECs compared to the sole neutralization against CCL2. Supernatants from tumor-conditioned Gr-1(+)CD11b(+) cells induced phosphorylation of ERK1/2 in HUVECs, and inhibition of the ERK pathway blocked angiogenic effects. ERK pathway activity was partially abrogated by neutralization of CCL2 and more suppressed by simultaneous neutralization of CCL2 and CXCL16. These results collectively indicate that CCL2 and CXCL16 chemokines produced by tumor-conditioned Gr-1(+)CD11b(+) myeloid cells synergistically induce angiogenesis in vitro by stimulating the ERK1/2 signaling pathway. Thus, regulation of Gr-1(+)CD11b(+) cells in the tumor microenvironment may contribute to angiogenesis through the secretion of pro-angiogenic chemokines.

Mechanisms of T-cell immunosuppression by mesenchymal stromal cells: what do we know so far?

Mesenchymal stromal cells (MSCs) are multipotent cells, which can give rise to several cell types including osteoblasts, adipocytes, and chondroblasts. These cells can be found in a variety of adult and fetal tissues, such as bone marrow, adipose tissue, cord blood, and placenta. In recent years, the biological properties of MSCs have attracted the attention of researchers worldwide due to their potential application for treating a series of clinical situations. Among these properties, special attention should be given to the immunoregulatory potential of those cells. MSCs are able to act on all cells of the immune system, which includes the capacity to inhibit the proliferation and function of T-cells. This feature renders them natural candidates to treat several diseases in which cellular immune response is exacerbated. In this review, we outline the main mechanisms by which MSCs immunosuppress T-cell response, focusing on cell-cell contact, secretion of soluble factors, and regulatory T-cell generation. The influence of surface markers in the immunosuppression process and features of MSCs isolated from different sources are also discussed. Finally, the influences of toll-like receptors and cytokines on the inflammatory microenvironment are highlighted regarding the activation of MSCs to exert their immunoregulatory function.

Recruitment of mesenchymal stem cells into prostate tumours promotes metastasis

Tumors recruit mesenchymal stem cells (MSCs) to facilitate healing, which induces their conversion into cancer-associated fibroblasts that facilitate metastasis. However, this process is poorly understood on the molecular level. Here we show that the CXCR6 ligand CXCL16 facilitates MSC or Very Small Embryonic-Like (VSEL) cells recruitment into prostate tumors. CXCR6 signaling stimulates the conversion of MSCs into cancer-associated fibroblasts, which secrete stromal-derived factor-1, also known as CXCL12. CXCL12 expressed by cancer-associated fibroblasts then binds to CXCR4 on tumor cells and induces an epithelial to mesenchymal transition, which ultimately promotes metastasis to secondary tumor sites. Our results provide the molecular basis for MSC recruitment into tumors and how this process leads to tumor metastasis.

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

Tumor progression is a multistep phenomenon in which tumor-associated stromal cells perform an intricate cross-talk with tumor cells, supplying appropriate signals that may promote tumor aggressiveness. Among several cell types that constitute the tumor stroma, the discovery that bone marrow-derived mesenchymal stem cells (BM-MSC) have a strong tropism for tumors has achieved notoriety in recent years. Not only are the BM-MSC recruited, but they can also engraft at tumor sites and transdifferentiate into cells such as activated fibroblasts, perivascular cells and macrophages, which will perform a key role in tumor progression. Whether the BM-MSC and their derived cells promote or suppress the tumor progression is a controversial issue. Recently, it has been proposed that proinflammatory stimuli can be decisive in driving BM-MSC polarization into cells with either tumor-supportive or tumor-repressive phenotypes (MSC1/MSC2). These considerations are extremely important both to an understanding of tumor biology and to the putative use of BM-MSC as "magic bullets" against tumors. In this review, we discuss the role of BM-MSC in many steps in tumor progression, focusing on the factors that attract BM-MSC to tumors, BM-MSC differentiation ability, the role of BM-MSC in tumor support or inhibition, the immunomodulation promoted by BM-MSC and metastatic niche formation by these cells.

DNA methylation of dermal MSCs in psoriasis: identification of epigenetically dysregulated genes

BACKGROUND

Mesenchymal stem cells (MSCs) are likely involved in pathological processes of immune-related diseases, including psoriasis, because of their immunoregulatory and pro-angiogenic effects. DNA methylation plays an essential role in regulating gene expression and maintaining cell function.

OBJECTIVE

This study aimed to investigate the gene methylation profile of dermal MSCs from patients with psoriasis.

METHODS

We isolated and expanded dermal MSCs from psoriatic patients and normal controls using the attachment assay and conducted genome-wide DNA methylation profile and gene ontology analyses using microarray.

RESULTS

The cultured cells were indentified as MSCs by surface marker and differentiation assays. The genome-wide promoter methylation profile of MSCs from psoriatic derma was markedly different from the normal derma derived MSCs. Genes involved in cell communication, surface receptor signaling pathway, cellular response to stimulus, and cell migration were differently methylated. Several aberrantly methylated genes related epidermal proliferation, angiogenesis, and inflammation were found differently expressed in psoriatic patients.

CONCLUSIONS

These results indicated that the MSCs from dermal of psoriasis are probably participant in the pathogenesis and development of psoriasis through an extraordinarily complex mechanism.

Human bone marrow-derived mesenchymal stem cells suppress human glioma growth through inhibition of angiogenesis

Tumor tropism of human bone marrow-derived mesenchymal stem cells (MSC) has been exploited for the delivery of therapeutic genes for anticancer therapy. However, the exact contribution of these cells in the tumor microenvironment remains unknown. In this study, we examined the biological effect of MSC on tumor cells. The results showed that MSC inhibited the growth of human glioma cell lines and patient-derived primary glioma cells in vitro. Coadministration of MSC and glioma cells resulted in significant reduction in tumor volume and vascular density, which was not observed when glioma was injected with immortalized normal human astrocytes. Using endothelial progenitor cells (EPC) from healthy donors and HUVEC endothelial cells, the extent of EPC recruitment and capacity to form endothelial tubes was significantly impaired in conditioned media derived from MSC/glioma coculture, suggesting that MSC suppressed tumor angiogenesis through the release of antiangiogenic factors. Further studies using antibody array showed reduced expression of platelet-derived growth factor (PDGF)-BB and interleukin (IL)-1β in MSC/glioma coculture when compared with controls. In MSC/glioma coculture, PDGF-BB mRNA and the corresponding proteins (soluble and membrane bound forms) as well as the receptors were found to be significantly downregulated when compared with that of glioma cocultured with normal human astrocytes or glioma monoculture. Furthermore, IL-1β, phosphorylated Akt, and cathepsin B proteins were also reduced in MSC/glioma. Taken together, these data indicated that the antitumor effect of MSC may be mediated through downregulation of PDGF/PDGFR axis, which is known to play a key role in glioma angiogenesis. STEM Cells2013;31:146-155.

Bone marrow-derived mesenchymal stem cells promote growth and angiogenesis of breast and prostate tumors

INTRODUCTION

Mesenchymal stem cells (MSCs) are known to migrate to tumor tissues. This behavior of MSCs has been exploited as a tumor-targeting strategy for cell-based cancer therapy. However, the effects of MSCs on tumor growth are controversial. This study was designed to determine the effect of MSCs on the growth of breast and prostate tumors.

METHODS

Bone marrow-derived MSCs (BM-MSCs) were isolated and characterized. Effects of BM-MSCs on tumor cell proliferation were analyzed in a co-culture system with mouse breast cancer cell 4T1 or human prostate cancer cell DU145. Tumor cells were injected into nude mice subcutaneously either alone or coupled with BM-MSCs. The expression of cell proliferation and angiogenesis-related proteins in tumor tissues were immunofluorescence analyzed. The angiogenic effect of BM-MSCs was detected using a tube formation assay. The effects of the crosstalk between tumor cells and BM-MSCs on expression of angiogenesis related markers were examined by immunofluorescence and real-time PCR.

RESULTS

Both co-culturing with mice BM-MSCs (mBM-MSCs) and treatment with mBM-MSC-conditioned medium enhanced the growth of 4T1 cells. Co-injection of 4T1 cells and mBM-MSCs into nude mice led to increased tumor size compared with injection of 4T1 cells alone. Similar experiments using DU145 cells and human BM-MSCs (hBM-MSCs) instead of 4T1 cells and mBM-MSCs obtained consistent results. Compared with tumors induced by injection of tumor cells alone, the blood vessel area was greater in tumors from co-injection of tumor cells with BM-MSCs, which correlated with decreased central tumor necrosis and increased tumor cell proliferation. Furthermore, both conditioned medium from hBM-MSCs alone and co-cultures of hBM-MSCs with DU145 cells were able to promote tube formation ability of human umbilical vein endothelial cells. When hBM-MSCs are exposed to the DU145 cell environment, the expression of markers associated with neovascularization (macrophage inflammatory protein-2, vascular endothelial growth factor, transforming growth factor-beta and IL-6) was increased.

CONCLUSION

These results indicate that BM-MSCs promote tumor growth and suggest that the crosstalk between tumor cells and BM-MSCs increased the expression of pro-angiogenic factors, which may have induced tumor cell proliferation and angiogenesis thereby increasing solid tumor growth.

Mesenchymal stem cells: a new trend for cell therapy

Mesenchymal stem cells (MSCs), the major stem cells for cell therapy, have been used in the clinic for approximately 10 years. From animal models to clinical trials, MSCs have afforded promise in the treatment of numerous diseases, mainly tissue injury and immune disorders. In this review, we summarize the recent opinions on methods, timing and cell sources for MSC administration in clinical applications, and provide an overview of mechanisms that are significant in MSC-mediated therapies. Although MSCs for cell therapy have been shown to be safe and effective, there are still challenges that need to be tackled before their wide application in the clinic.

Impact of mesenchymal stem cell secreted PAI-1 on colon cancer cell migration and proliferation

Mesenchymal Stem Cells are known to engraft and integrate into the architecture of colorectal tumours, with little known regarding their fate following engraftment. This study aimed to investigate mediators of Mesenchymal Stem Cell (MSC) and colon cancer cell (CCC) interactions. Mesenchymal Stem Cells and colon cancer cells (HT29 and HCT-116) were cultured individually or in co-culture on 3-dimensional scaffolds. Conditioned media containing all secreted factors was harvested at day 1, 3 and 7. Chemokine secretion and expression were analyzed by Chemi-array, ELISA (Macrophage migration inhibitory factor (MIF), plasminogen activator inhibitor type 1 (PAI-1)) and RQ-PCR. Colon cancer cell migration and proliferation in response to recombinant PAI-1, MSCs and MSCs+antibody to PAI-1 was analyzed using Transwell inserts and an MTS proliferation assay respectively. Chemi-array revealed secretion of a wide range of factors by each cell population, including PAI-1 and MIF. ELISA analysis revealed Mesenchymal Stem Cells to secrete the highest levels of PAI-1 (MSC mean 10.6 ng/mL, CCC mean 1.01 ng/mL), while colon cancer cells were the principal source of MIF. MSC-secreted PAI-1 stimulated significant migration of both CCC lines, with an antibody to the chemokine shown to block this effect (67-88% blocking,). A cell-line dependant effect on CCC proliferation was shown for Mesenchymal Stem Cell-secreted PAI-1 with HCT-116 cells showing decreased proliferation at all concentrations, and HT29 cells showing increased proliferation in the presence of higher PAI-1 levels. This is the first study to identify PAI-1 as an important mediator of Mesenchymal Stem Cell/colon cancer cell interactions and highlights the significant functional impact of Mesenchymal Stem Cell-secreted PAI-1 on colon cancer cells.

Mesenchymal stem cells in the tumor microenvironment

Mesenchymal stem cells (MSCs) are non-hematopoietic, multipotent cells, which are able to differentiate to bone, adipose and cartilage tissue. MSCs have the characteristic of migration to injured areas or tumor microenvironment following induction by chemokines or inflammatory factors. An increasing number of studies have reported that MSCs recruited to the tumor microenvironment play various roles in tumor cell development and tumor progression. In this study, we reviewed the studies related to the tumor-promoting roles of MSCs from several aspects, such as increasing stemness of tumor cells, mediating migration, promoting angiogenesis, suppressing immune response and inducing drug resistance.

Inflammation-mediated genetic and epigenetic alterations drive cancer development in the neighboring epithelium upon stromal abrogation of TGF-β signaling

Deletion of tumor suppressor genes in stromal fibroblasts induces epithelial cancer development, suggesting an important role of stroma in epithelial homoeostasis. However, the underlying mechanisms remain to be elucidated. Here we report that deletion of the gene encoding TGFβ receptor 2 (Tgfbr2) in the stromal fibroblasts (Tgfbr2^fspKO) induces inflammation and significant DNA damage in the neighboring epithelia of the forestomach. This results in loss or down-regulation of cyclin-dependent kinase inhibitors p15, p16, and p21, which contribute to the development of invasive squamous cell carcinoma (SCC). Anti-inflammation treatment restored p21 expression, delayed tumorigenesis, and increased survival of Tgfbr2^fspKO mice. Our data demonstrate for the first time that inflammation is a critical player in the epigenetic silencing of p21 in tumor progression. Examination of human esophageal SCC showed a down-regulation of TGFβ receptor 2 (TβRII) in the stromal fibroblasts, as well as increased inflammation, DNA damage, and loss or decreased p15/p16 expression. Our study suggests anti-inflammation may be a new therapeutic option in treating human SCCs with down-regulation of TβRII in the stroma.

Cancer is no longer regarded as a problem of solely cancer cells. The development and metastasis of cancers clearly involves many aspects of the host. We sought to identify the molecular mechanisms underlying epithelial cancer development due to alterations in stromal cells. Using an animal model in which TGF-β signaling is deleted in stromal fibroblasts, we found that inflammation and DNA damage are induced in the epithelial compartment and are responsible for the loss of cell cycle–dependent kinase inhibitors, leading to the compromise of epithelial cell cycle control. These results are important in understanding the stromal-tumor cross talk which has been an important focus in cancer biology in recent years. Our findings suggest that careful examination of the stromal compartment is important and that anti-inflammation therapy may be a new chemoprevention option for epithelial cancer development.

Biological and clinical availability of adipose-derived stem cells for pelvic dead space repair

Adipose-derived stem cells (ADSCs) are a very attractive cell source for regenerative and reconstructive medicine. Although ADSCs have already been used in cardiovascular disease and cosmetic surgery, they have not yet been used in gastroenterological surgery. In this study, we clarified the utility of the combined application of ADSCs and resected intraperitoneal fatty tissues as a sealant for the pelvic dead space that sometimes causes severe and fatal complications in colorectal and gynecological surgeries. In pelvic dead space model mice, mouse ADSCs efficiently maintained transplanted intraperitoneal fatty tissues without any incidence of adhesion to surrounding organs. In vivo and in vitro analyses revealed that transplanted ADSCs differentiated into endothelial cells by expressing the angiogenic factors vascular endothelial growth factor and hepatocyte growth factor. Mouse and human ADSCs contained a CD45(-)CD34(+) subset possessing high colony formation and sphere formation abilities. In addition, the CD45(-)CD34(+) subset consisted of two characteristic subsets: the CD34(+)CD90(+) angiogenic subset and the CD34(+)CD90(-) adipogenic subset. Grafts of human ADSCs with fat transplanted into mice were efficiently maintained for more than 12 months without volume reductions. A comparative study of graft maintenance efficacy between cultured human ADSCs and freshly isolated ADSCs indicated that the cultivation of ADSCs decreased their graft maintenance ability. These findings suggested that the angiogenic and adipogenic subsets act in coordination with each other and are essential for efficient graft maintenance.

Mesenchymal stem cells promote growth and angiogenesis of tumors in mice

Though the early integration of mesenchymal stem cells (MSCs) into tumor-associated stroma of cancer has been demonstrated, the functional contributions and underlying mechanisms of these cells to tumor growth and angiogenesis remain to be clarified. Using a xenograft model, human colorectal cancer cells, MSCs, and their cell mixture were introduced to a subcutaneous site of immunodeficient mice. The tumor growth rate and angiogenesis of each transplantation was then compared. We demonstrate that a variety of colorectal cancer cells, when mixed with otherwise non-tumorigenic MSCs, increase the tumor growth rate and angiogenesis more than that when mixed with carcinoma-associated fibroblasts or normal colonic fibroblasts. The secretion of interleukin-6 (IL-6) from MSCs increases the secretion of endothelin-1 (ET-1) in cancer cells, which induces the activation of Akt and ERK in endothelial cells, thereby enhancing their capacities for recruitment and angiogenesis to tumor. The IL-6/ET-1/Akt or ERK pathway of tumor-stroma interaction can be targeted by an antibody against IL-6 or Lentiviral-mediated RNAi against IL-6 in MSCs, by inhibition or knockdown of ET-1 in cancer cells, or by inhibition of ERK and Akt in host endothelial cells. These demonstrate that attempts to interrupt the interaction of MSCs and cancer cells help to abrogate angiogenesis and inhibit tumor growth in tumors formed by cancer cells admixed with MSCs. These data demonstrate that the tumor microenvironment, namely, MSCs-secreted IL-6, may enrich the proangiognic factors secreted by cancer cells to increase angiogenesis and tumor growth and that targeting this interaction may lead to novel therapeutic and preventive strategies.

Assessing the in vivo efficacy of biologic antiangiogenic therapies

PURPOSE

To review key clinical issues underlying the assessment of in vivo efficacy when using antiangiogenic therapies for cancer treatment.

METHODS

Literature relevant to use of antiangiogenic therapies in cancer was reviewed, with particular emphasis on the assessment of in vivo efficacy of these agents, as well as additional angiogenic factors that could play a role in escape from angiogenesis inhibition.

RESULTS

In order to grow and metastasize, tumors need to continually acquire new blood supplies; therefore, therapeutic inhibition of angiogenesis has become a component of anticancer treatment for many tumor types. Bevacizumab, a humanized monoclonal antibody directed at vascular endothelial growth factor A (VEGF-A), has shown activity in combination with chemotherapy in metastatic colorectal cancer. Nevertheless, the use of antiangiogenic therapies remains suboptimal; specifically, optimal dose, duration of therapy, and combination of agents remain unknown. Also, at present, it is not possible to determine which patients are most likely to respond to a given form of antiangiogenic therapy. There has been increased recognition of alternative pathways possibly associated with disease progression in patients undergoing antiangiogenic therapy targeted at VEGF-A. Multiligand-targeted antiangiogenic therapies, such as ziv-aflibercept (formerly known as aflibercept, VEGF Trap), are currently undergoing clinical evaluation. Ziv-aflibercept forms monomeric complexes with VEGF-A, VEGF-B, and PlGF, which have a long half-life, allowing optimization of ziv-aflibercept doses and angiogenic blockage.

CONCLUSIONS

Although antiangiogenic therapies have increased treatment options for cancer patients, their use is limited by a lack of established and standardized methodology to evaluate their efficacy in vivo. Circulating endothelial cells, hypertension, and several molecular and imaging-based markers have potential for use as biomarkers in these patients and may better define appropriate patient populations.

Adipose tissue regeneration: a state of the art

Adipose tissue pathologies and defects have always represented a reconstructive challenge for plastic surgeons. In more recent years, several allogenic and alloplastic materials have been developed and used as fillers for soft tissue defects. However, their clinical use has been limited by further documented complications, such as foreign-body reactions potentially affecting function, degradation over time, and the risk for immunogenicity. Tissue-engineering strategies are thus being investigated to develop methods for generating adipose tissue. This paper will discuss the current state of the art in adipose tissue engineering techniques, exploring the biomaterials used, stem cells application, culture strategies, and current regulatory framework that are in use are here described and discussed.

Opposing roles for complement component C5a in tumor progression and the tumor microenvironment

Promoting complement (C) activation may enhance immunological mechanisms of anti-tumor Abs for tumor destruction. However, C activation components, such as C5a, trigger inflammation, which can promote tumor growth. We addressed the role of C5a on tumor growth by transfecting both human carcinoma and murine lymphoma with mouse C5a. In vitro growth kinetics of C5a, control vector, or parental cells revealed no significant differences. Tumor-bearing mice with C5a-transfected xenografted tumor cells had significantly less tumor burden as compared with control vector tumors. NK cells and macrophages infiltrated C5a-expressing tumors with significantly greater frequency, whereas vascular endothelial growth factor, arginase, and TNF-α production were significantly less. Tumor-bearing mice with high C5a-producing syngeneic lymphoma cells had significantly accelerated tumor progression with more Gr-1+CD11b+ myeloid cells in the spleen and overall decreased CD4+ and CD8+ T cells in the tumor, tumor-draining lymph nodes, and the spleen. In contrast, tumor-bearing mice with low C5a-producing lymphoma cells had a significantly reduced tumor burden with increased IFN-γ-producing CD4+ and CD8+ T cells in the spleen and tumor-draining lymph nodes. These studies suggest concentration of local C5a within the tumor microenvironment is critical in determining its role in tumor progression.

Mesenchymal stem cells in the colorectal tumor microenvironment: recent progress and implications

Mesenchymal stem cells (MSCs) are nonhematopoietic multipotent adult stem cells. They have been shown to have a natural tropism for many tumors types, including colorectal, and are capable of escaping host immune surveillance. MSCs are known to engraft at tumors and integrate into their architecture, potentially as carcinoma-associated fibroblasts. In contrast with other malignancies, our understanding of the interactions between colorectal cancer cells and MSCs remains limited. Considering the established importance of inflammation in the colorectal cancer primary tumor microenvironment and the role of stromal cells in this process, there is a potential wealth of information to be gleaned from further investigation of interactions between these cell populations. Epithelial-mesenchymal transition is central to colorectal cancer progression and MSCs have also been implicated in this process. This review explores the current knowledge (both in vitro and in vivo) of interactions between colorectal cancer cells and MSCs. It highlights potential effects of cell source, number and ratio on outcome of in vivo studies and explores strategies to more accurately explore their role in the primary tumor microenvironment. As our understanding of the underlying molecular processes in colorectal cancer develops, elucidation of these interactions will be central to development of novel therapeutic strategies for this prevalent disease.

Sarcomas as a mise en abyme of mesenchymal stem cells: exploiting interrelationships for cell mediated anticancer therapy

Mise en abyme meaning "placed into abyss or infinite recurrence" is an apt paradigm for the relentless growth of sarcoma cells. Its alternative meaning, "self-reflexive embedding" fits the central role attributed to cancer stem cells (CSCs). Diversely sourced and defined, mesenchymal stem cells (MSCs) may be the cells of sarcoma origin, evolve a CSC phenotype and/or contribute to tumor growth through inherent qualities for homing, neovascularization, paracrine cross-feeding, microvesicle secretion, cell fusion, entosis and immune modulation. Exploiting these qualities, MSC expressing modified forms of the TNF-related apoptosis-inducing ligand (Apo2L/TRAIL) are being developed to complement more conventional radiation and chemotherapy.

miR-21 modulates tumor outgrowth induced by human adipose tissue-derived mesenchymal stem cells in vivo

Mesenchymal stem cells (MSCs) have generated a great deal of interest in clinical situations, due principally to their potential use in regenerative medicine and tissue engineering applications. However, the therapeutic application of MSCs remains limited, unless the favorable effects of MSCs on tumor growth in vivo, and the long-term safety of the clinical applications of MSCs, can be more thoroughly understood. In this study, we determined whether microRNAs can modulate MSC-induced tumor outgrowth in BALB/c nude mice. Overexpression of miR-21 in human adipose-derived stem cells (hADSCs) inhibited hADSC-induced tumor growth, and inhibition of miR-21 increased it. Downregulation of transforming growth factor beta receptor II (TGFBR2), but not of signal transducer and activator of transcription 3, in hADSCs showed effects similar to those of miR-21 overexpression. Downregulation of TGFBR2 and overexpression of miR21 decreased tumor vascularity. Inhibition of miR-21 and the addition of TGF-β increased the levels of vascular endothelial growth factor and interleukin-6 in hADSCs. Transplantation of miR-21 inhibitor-transfected hADSCs increased blood flow recovery in a hind limb ischemia model of nude mice, compared with transplantation of control oligo-transfected cells. These findings indicate that MSCs might favor tumor growth in vivo. Thus, it is necessary to study the long-term safety of this technique before MSCs can be used as therapeutic tools in regenerative medicine and tissue engineering.

Mesenchymal stem cells in tumor development: emerging roles and concepts

Mesenchymal stem cells (MSCs) are multipotent progenitor cells that participate in the structural and functional maintenance of connective tissues under normal homeostasis. They also act as trophic mediators during tissue repair, generating bioactive molecules that help in tissue regeneration following injury. MSCs serve comparable roles in cases of malignancy and are becoming increasingly appreciated as critical components of the tumor microenvironment. MSCs home to developing tumors with great affinity, where they exacerbate cancer cell proliferation, motility, invasion and metastasis, foster angiogenesis, promote tumor desmoplasia and suppress anti-tumor immune responses. These multifaceted roles emerge as a product of reciprocal interactions occurring between MSCs and cancer cells and serve to alter the tumor milieu, setting into motion a dynamic co-evolution of both tumor and stromal tissues that favors tumor progression. Here, we summarize our current knowledge about the involvement of MSCs in cancer pathogenesis and review accumulating evidence that have placed them at the center of the pro-malignant tumor stroma.

Relationships among the concentrations of 25 inflammation-associated proteins during the first postnatal weeks in the blood of infants born before the 28th week of gestation

BACKGROUND

Inflammation appears to be involved in processes leading to organ damage in preterm newborns, yet little is known about the relationships among elevated concentrations of inflammation-associated proteins in the blood of preterm newborns.

METHODS

In this exploratory study, we used an electrochemiluminescence method to measure 25 proteins in blood obtained on postnatal day 1 (range 1-3), day 7 (range 5-8), and day 14 (range 12-15) from 939 children born before the 28th week of gestation and evaluated to what extent those whose concentration of each protein was elevated (defined as in the highest quartile for gestational age and day the specimen was obtained) also had an elevated concentration of every other protein the same day or on a day 1 or 2 weeks later (p<.0001).

RESULTS

On each of the 3 days assessed, elevated concentrations of 17 proteins were associated with elevated concentrations of 15 or more of the other 24 proteins. VEGF, VEGF-R1, VEGF-R2 were among these proteins, while IGFBP-1 was associated with 13 other proteins on day 7. An elevated concentration of eight proteins on day 1 predicted an elevated concentration of 10 or more proteins on day 7, while an elevated concentration of only two proteins on day 7 were associated with elevated concentrations of 10 or more proteins on day-14. Few associations were seen between days 1 and 14. CONCLUSIONS/INFERENCES: Inflammation is a diffuse process in ELGANs, with elevated concentrations of cytokines, chemokines, adhesion molecules, matrix metalloproteinases, a growth factor and its receptors, as well as a growth factor binding protein associated with each other the same day, as well as on subsequent days.