Mesenchymal stem cells (MSC) exhibit tropism for sites of tissue damage as well as the tumor microenvironment. Many of the same inflammatory mediators that are secreted by wounds are found in the ...tumor microenvironment and are thought to be involved in attracting MSC to these sites. Cell migration is dependent on a multitude of signals ranging from growth factors to chemokines secreted by injured cells and/or respondent immune cells. MSC are likely to have chemotactic properties similar to other immune cells that respond to injury and sites of inflammation. Thus, the well-described model of leukocyte migration can serve as a reasonable example to facilitate the identification of factors involved in MSC migration. Understanding the factors involved in regulating MSC migration to tumors is essential to ultimately develop novel clinical strategies aimed at using MSC as vehicles to deliver antitumor proteins or suppress MSC migration to reduce tumor growth. For example, radiation enhances inflammatory signaling in the tumor microenvironment and may be used to potentiate site-specific MSC migration. Alternatively, restricting the migration of the MSC to the tumor microenvironment may prevent competent tumor-stroma formation, thereby hindering the growth of the tumor. In this review, we will discuss the role of inflammatory signaling in attracting MSC to tumors.
The epithelial-mesenchymal transition (EMT) bestows cancer cells with increased stem cell properties and metastatic potential. To date, multiple extracellular stimuli and transcription factors have ...been shown to regulate EMT. Many of them are not druggable and therefore it is necessary to identify targets, which can be inhibited using small molecules to prevent metastasis. Recently, we identified the ganglioside GD2 as a novel breast cancer stem cell marker. Moreover, we found that GD3 synthase (GD3S)--an enzyme involved in GD2 biosynthesis--is critical for GD2 production and could serve as a potential druggable target for inhibiting tumor initiation and metastasis. Indeed, there is a small molecule known as triptolide that has been shown to inhibit GD3S function. Accordingly, in this manuscript, we demonstrate that the inhibition of GD3S using small hairpin RNA or triptolide compromises the initiation and maintenance of EMT instigated by various signaling pathways, including Snail, Twist and transforming growth factor-β1 as well as the mesenchymal characteristics of claudin-low breast cancer cell lines (SUM159 and MDA-MB-231). Moreover, GD3S is necessary for wound healing, migration, invasion and stem cell properties in vitro. Most importantly, inhibition of GD3S in vivo prevents metastasis in experimental as well as in spontaneous syngeneic wild-type mouse models. We also demonstrate that the transcription factor FOXC2, a central downstream effector of several EMT pathways, directly regulates GD3S expression by binding to its promoter. In clinical specimens, the expression of GD3S correlates with poor prognosis in triple-negative human breast tumors. Moreover, GD3S expression correlates with activation of the c-Met signaling pathway leading to increased stem cell properties and metastatic competence. Collectively, these findings suggest that the GD3S-c-Met axis could serve as an effective target for the treatment of metastatic breast cancers.
MicroRNAs (miRNAs) are small non-coding RNAs of 19-25 nucleotides that are involved in the regulation of critical cell processes such as apoptosis, cell proliferation and differentiation. However, ...little is known about the role of miRNAs in granulopoiesis. Here, we report the expression of miRNAs in acute promyelocytic leukemia patients and cell lines during all-trans-retinoic acid (ATRA) treatment by using a miRNA microarrays platform and quantitative real time-polymerase chain reaction (qRT-PCR). We found upregulation of miR-15a, miR-15b, miR-16-1, let-7a-3, let-7c, let-7d, miR-223, miR-342 and miR-107, whereas miR-181b was downregulated. Among the upregulated miRNAs, miR-107 is predicted to target NFI-A, a gene that has been involved in a regulatory loop involving miR-223 and C/EBPa during granulocytic differentiation. Indeed, we have confirmed that miR-107 targets NF1-A. To get insights about ATRA regulation of miRNAs, we searched for ATRA-modulated transcription factors binding sites in the upstream genomic region of the let-7a-3/let-7b cluster and identified several putative nuclear factor-kappa B (NF-kappaB) consensus elements. The use of reporter gene assays, chromatin immunoprecipitation and site-directed mutagenesis revealed that one proximal NF-kappaB binding site is essential for the transactivation of the let-7a-3/let-7b cluster. Finally, we show that ATRA downregulation of RAS and Bcl2 correlate with the activation of known miRNA regulators of those proteins, let-7a and miR-15a/miR-16-1, respectively.
Electrical impedance tomography (EIT) with indicator dilution may be clinically useful to measure relative lung perfusion, but there is limited information on the performance of this technique.
...Thirteen pigs (50–66 kg) were anaesthetised and mechanically ventilated. Sequential changes in ventilation were made: (i) right-lung ventilation with left-lung collapse, (ii) two-lung ventilation with optimised PEEP, (iii) two-lung ventilation with zero PEEP after saline lung lavage, (iv) two-lung ventilation with maximum PEEP (20/25 cm H2O to achieve peak airway pressure 45 cm H2O), and (v) two-lung ventilation under unilateral pulmonary artery occlusion. Relative lung perfusion was assessed with EIT and central venous injection of saline 3%, 5%, and 10% (10 ml) during breath holds. Relative perfusion was determined by positron emission tomography (PET) using 68Gallium-labelled microspheres. EIT and PET were compared in eight regions of equal ventro-dorsal height (right, left, ventral, mid-ventral, mid-dorsal, and dorsal), and directional changes in regional perfusion were determined.
Differences between methods were relatively small (95% of values differed by less than 8.7%, 8.9%, and 9.5% for saline 10%, 5%, and 3%, respectively). Compared with PET, EIT underestimated relative perfusion in dependent, and overestimated it in non-dependent, regions. EIT and PET detected the same direction of change in relative lung perfusion in 68.9–95.9% of measurements.
The agreement between EIT and PET for measuring and tracking changes of relative lung perfusion was satisfactory for clinical purposes. Indicator-based EIT may prove useful for measuring pulmonary perfusion at bedside.
Tyrosine kinase inhibitor (TKI) resistance and progression to blast crisis (BC), both related to persistent β-catenin activation, remain formidable challenges for chronic myeloid leukemia (CML). We ...observed overexpression of β-catenin in BC-CML stem/progenitor cells, particularly in granulocyte-macrophage progenitors, and highest among a novel CD34
CD38
CD123
Tim-3
subset as determined by CyTOF analysis. Co-culture with mesenchymal stromal cells (MSCs) induced the expression of β-catenin and its target CD44 in CML cells. A novel Wnt/β-catenin signaling modulator, C82, and nilotinib synergistically killed KBM5
and TKI-resistant primary BC-CML cells with or without BCR-ABL kinase mutations even under leukemia/MSC co-culture conditions. Silencing of β-catenin by short interfering RNA restored sensitivity of primary BCR-ABL
BC-CML cells to nilotinib. Combining the C82 pro-drug, PRI-724, with nilotinib significantly prolonged the survival of NOD/SCID/IL2Rγ null mice injected with primary BCR-ABL
BC-CML cells. The combined treatment selectively targeted CML progenitors and inhibited CD44, c-Myc, survivin, p-CRKL and p-STAT5 expression. In addition, pretreating primary BC-CML cells with C82, or the combination, but not with nilotinib alone, significantly impaired their engraftment potential in NOD/SCID/IL2Rγ-null-3/GM/SF mice and significantly prolonged survival. Our data suggest potential benefit of concomitant β-catenin and Bcr-Abl inhibition to prevent or overcome Bcr-Abl kinase-dependent or -independent TKI resistance in BC-CML.
Nur77 and Nor1 are highly conserved orphan nuclear receptors. We have recently reported that nur77(-/-)nor1(-/-) mice rapidly develop acute myeloid leukemia (AML) and that Nur77 and Nor1 transcripts ...were universally downregulated in human AML blasts. These findings indicate that Nur77 and Nor1 function as leukemia suppressors. We further demonstrated silencing of Nur77 and Nor1 in leukemia stem cells (LSCs). We here report that inhibition of histone deacetylase (HDAC) using the specific class I HDAC inhibitor SNDX-275 restored the expression of Nur77/Nor1 and induced expression of activator protein 1 transcription factors c-Jun and JunB, and of death receptor TRAIL, in AML cells and in CD34(+)/38(-) AML LSCs. Importantly, SNDX-275 induced extensive apoptosis in AML cells, which could be suppressed by silencing nur77 and nor1. In addition, pro-apoptotic proteins Bim and Noxa were transcriptionally upregulated by SNDX-275 in AML cells and in LSCs. Our present work is the first report of a novel mechanism of HDAC inhibitor-induced apoptosis in AML that involves restoration of the silenced nuclear receptors Nur77 and Nor1, activation of activator protein 1 transcription factors, a death receptor and pro-apoptotic proteins.
Background: High concentrations of interferon beta (IFN-β) inhibit malignant cell growth in vitro. However, the therapeutic utility of IFN-β in vivo is limited by its excessive toxicity when ...administered systemically at high doses. Mesenchymal stem cells (MSC) can be used to target delivery of agents to tumor cells. We tested whether MSC can deliver IFN-β to tumors, reducing toxicity. Methods: Human MSC were transduced with an adenoviral expression vector carrying the human IFN-β gene (MSC-IFN-β cells). Flow cytometry was used to measure tumor cell proliferation among in vitro co-cultures of MSC-IFN-β cells and human MDA 231 breast carcinoma cells or A375SM melanoma cells. We used a severe combined immunodeficiency mouse xenograft model (4–10 mice per group) to examine the effects of injected MSC-IFN-β cells and human recombinant IFN-β on the growth of MDA 231- and A375SM-derived pulmonary metastases in vivo and on survival. All statistical tests were two-sided. Results: Co-culture of MSC-IFN-β cells with A375SM cells or MDA 231 cells inhibited tumor cell growth as compared with growth of the tumor cells cultured alone (differences in mean percentage of control cell growth: −94.0% 95% confidence interval {CI} = −81.2% to −106.8%; P<.001 and −104.8% 95% CI = −82.1% to −127.5%; P<.001, respectively). Intravenous injection of MSC-IFN-β cells into mice with established MDA 231 or A375SM pulmonary metastases led to incorporation of MSC in the tumor architecture and, compared with untreated control mice, to prolonged mouse survival (median survival for MDA 231–injected mice: 60 and 37 days for MSC-injected and control mice, respectively difference = 23.0 days (95% CI = 14.5 to 34.0 days; P<.001; median survival for A375SM-injected mice: 73.5 and 30.0 days for MSC-injected and control mice, respectively difference = 43.5 days (95% CI = 37.0 to 57.5 days; P<.001). By contrast, intravenous injection of recombinant IFN-β did not prolong survival in the same models (median survival for MDA 231–injected mice: 41.0 and 37.0 days for IFN-β–injected and control mice, respectively difference = 4 days, 95% CI = −5 to 10 days; P = .308; median survival for A375SM-injected mice: 32.0 and 30.0 days for IFN-β–injected and control mice, respectively difference = 2 days, 95% CI = 0 to 4.5 days; P = .059). Conclusions: Injected MSC-IFN-β cells suppressed the growth of pulmonary metastases, presumably through the local production of IFN-β in the tumor microenvironment. MSC may be an effective platform for the targeted delivery of therapeutic proteins to cancer sites.
MicroRNAs (miRNAs) are a family of 19-24 nucleotide noncoding RNAs (ncRNAs) with posttranscriptional regulatory functions. Increasing evidences from the literature show that miRNAs play a pivotal ...role in human tumorigenesis. Many studies have addressed the role of miRNAs in normal hematopoiesis, giving an interpretative key to the aberrancies of expression observed in human hematological malignancies. Moreover, the recent demonstration that other ncRNAs, the ultraconserved genes (UCGs) or transcribed ultraconserved regions (T-UCRs), are involved in human cancerogenesis, suggests that the wider family of ncRNAs (including both miRNAs and UCGs) could contribute to the development of the malignant phenotype. Here we review the main studies investigating the role of miRNAs and UCRs in both normal hemopoiesis and hematological malignancies, and identify the molecular, clinical and therapeutic implications of these recent findings.
Disease recurrence is the major problem in the treatment of acute myeloid leukemia (AML). Relapse is driven by leukemia stem cells, a chemoresistant subpopulation capable of re-establishing disease. ...Patients with p53 mutant AML are at an extremely high risk of relapse. B-cell-specific Moloney murine leukemia virus integration site 1 (BMI-1) is required for the self-renewal and maintenance of AML stem cells. Here we studied the effects of a novel small molecule inhibitor of BMI-1, PTC596, in AML cells. Treatment with PTC596 reduced MCL-1 expression and triggered several molecular events consistent with induction of mitochondrial apoptosis: loss of mitochondrial membrane potential, BAX conformational change, caspase-3 cleavage and phosphatidylserine externalization. PTC596 induced apoptosis in a p53-independent manner. PTC596 induced apoptosis along with the reduction of MCL-1 and phosphorylated AKT in patient-derived CD34
CD38
stem/progenitor cells. Mouse xenograft models demonstrated in vivo anti-leukemia activity of PTC596, which inhibited leukemia cell growth in vivo while sparing normal hematopoietic cells. Our results indicate that PTC596 deserves further evaluation in clinical trials for refractory or relapsed AML patients, especially for those with unfavorable complex karyotype or therapy-related AML that are frequently associated with p53 mutations.
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