Downregulation Of CXCL12 Research Articles

Adipose-derived mesenchymal stem cells suppress fibroblast proliferation of hypertrophic scar through CCL5 and CXCL12.

Adipose-derived mesenchymal stem cells (ADSCs) can accelerate wound healing, reduce scar formation, and inhibit hypertrophic scar (HTS). ADSCs can secrete a large amount of CCL5, and CCL5 has been proved to be pro-inflammatory and pro-fibrotic. CXCL12 (SDF-1) is a key chemokine that promotes stem cell migration and survival. Therefore, this study selected normal skin and HTS conditioned medium to simulate different microenvironments, and analyzed the effects of different microenvironments on the expression of CCL5 and CXCL12 in human ADSCs (hADSCs). hADSCs with silenced expression of CCL5 and CXCL12 were co-cultured with hypertrophic scar fibroblasts to verify the effects of CCL5 and CXCL12 in hADSCs on the proliferation ability of hypertrophic scar fibroblasts. A mouse model of hypertrophic scar was established to further confirm the effect of CCL5 and CXCL12 in hADSCs on hypertrophic scar formation. CCL5 level was found to be significantly high in hADSCs cultured in HTS conditioned medium. CXCL12 in HTS group was prominently lowly expressed compared with the normal group. Inhibition of CCL5 in hADSCs enhanced the effects of untreated hADSCs on proliferation of HTS fibroblasts while CXCL12 knockdown exerted the opposite function. Inhibition of CCL5 in hADSCs increased the percentage of HTS fibroblasts in the G0/G1 phase while down-regulation of CXCL12 decreased those. Meanwhile, the down-regulated levels of fibroblast markers including collagen I, collagen III, and α-SMA induced by CCL5 knockdown were significantly up-regulated by CXCL12 inhibition. hADSCs alleviate the HTS of mice through CCL5 and CXCL12. In summary, our results demonstrated that hADSCs efficiently cured HTS by suppressing proliferation of HTS fibroblasts, which may be related to the inhibition of CXCL12 and elevation of CCL5 in hADSCs, suggesting that hADSCs may provide an alternative therapeutic approach for the treatment of HTS.

SPI1-mediated CXCL12 expression in bladder cancer affects the recruitment of tumor-associated macrophages.

Bladder cancer (BC) originates principally from the epithelial compartment of the bladder. The immune system and its diverse players, chemokines, in particular, have been related to the responses against BC. The goal of the study here was to examine if C-X-C motif chemokine 12 (CXCL12) in BC cells could manipulate protumorigenic properties of tumor-associated macrophages (TAMs) which affects anticancer immunity supporting tumor development in the tumor microenvironment. CXCL12 was found to be overexpressed in BC and predicted poor survival. CXCL12 in BC was associated with multiple immune cell infiltrations, with TAM infiltration playing a key role. CXCL12 elevated chemotaxis of TAMs. CXCL12 downregulation inhibited cellular activity and TAM and suppressed the ability of TAMs to secrete inflammatory factors and MMP9. Furthermore, chromatin immunoprecipitation analysis revealed that SPI1 was localized to the CXCL12 promoter in BC cells, suggesting that CXCL12 serves a direct target of SPI1, which was consistent with the fact that SPI1 reversed the repressive effects of si-CXCL12 on BC cell activity and TAM recruitment in vitro and in vivo. Collectively, these findings suggest that SPI1 is involved in modulating TAM recruitment, representing a new mechanism through which it may influence tumor growth. This may be partly mediated by regulating CXCL12 expression.

CXCL12/CXCR4/CXCR7 axis in placenta tissues of patients with placenta previa.

CXCR4 and CXCR7 have been revealed to be receptors of CXCL12. This research was designed to probe the expression of chemokine CXCL12 and its receptors CXCR4 and CXCR7 in placental tissues of patients with placenta previa and the effect of CXCL12/CXCR4/CXCR7 axis on the biological functions of human trophoblast cells. CXCL12, CXCR4, and CXCR7 expression in placental tissue from patients with placenta previa and healthy puerperae was detected. CXCL12, CXCR4, and CXCR7 expression in human trophoblast cell lines (HTR8/SVneo cells) was assessed after suppression or overexpression of CXCL12, CXCR4, and CXCR7. The cell proliferative, invasive, and migratory capacities were also evaluated in HTR8/SVneo cells after suppression or overexpression of CXCL12, CXCR4, and CXCR7. CXCL12, CXCR4, and CXCR7 expression was elevated in placental tissues from patients with placenta previa. Downregulation of CXCL12, CXCR4, and CXCR7 could lead to decreased mRNA levels of CXCL12, CXCR4, and CXCR7 in HTR-8/SVneo cells, which was accompanied by diminished cell proliferative, migratory, and invasive capabilities. Overexpression of CXCL12, CXCR4, and CXCR7 genes presented an opposite tendency. CXCL12, CXCR4, and CXCR7 are highly expressed in placental tissues of patients with placenta previa and induce the biological activities of HTR8/SVneo cells.

CXCL12, a potential modulator of tumor immune microenvironment (TIME) of bladder cancer: From a comprehensive analysis of TCGA database.

Tumor immune microenvironment (TIME) plays a significant role in the initiation and progression of bladder urothelial carcinoma (BLCA). However, there are only a few researches regarding the association between immune-related genes and tumor-infiltrating immune cells (TICs) in TIME of BLCA. We calculated the proportion of immune/stromal component and TICs of 414 BLCA samples and 19 normal samples downloaded from TCGA database with the help of ESTIMATE and CIBERSORT algorithms. Differentially expressed genes (DEGs) were obtained from the comparison between Stromal and Immune Score and further analyzed by GO and KEGG enrichment analysis, as well as PPI network and COX regression analysis. CXCL12 was overlapping among the above analyses. Single gene analysis of CXCL12 was carried out through difference analysis, paired analysis and GSEA. The association between CXCL12 and TICs was assessed by difference analysis and correlation analysis. Immune and stromal component in TIME of BLCA were associated with patients' clinicopathological characteristics. 284 DEGs were primarily enriched in immune-associated activities, among which CXCL12 was the most significant gene sharing the leading nodes in PPI network and being closely related with patients' survival. Single gene analysis and immunohistochemistry revealed that CXCL12 was down-regulated in BLCA samples and significantly related with the clinicopathological characteristics of patients. Further analysis suggested that CXCL12 was involved in the immune-associated activities probably through its close cross-talk with TICs. CXCL12 down-regulation could be a potential biomarker to predict the unbalanced immune status of TIME of BLCA, which might provide an extra insight for the immunotherapy of BLCA.

Loss of bone morphogenetic protein signaling in fibroblasts results in CXCL12-driven serrated polyp development

Mutations in Bone Morphogenetic Protein (BMP) Receptor (BMPR)1A and SMAD4 are detected in 50% of juvenile polyposis syndrome (JPS) patients, who develop stroma-rich hamartomatous polyps. The established role of stromal cells in regulating BMP activity in the intestine implies a role for stromal cells in polyp development. We used conditional Cre-LoxP mice to investigate how specific loss of BMPR1A in endothelial cells, fibroblasts, or myofibroblasts/smooth muscle cells affects intestinal homeostasis. Selective loss of BMPR1A in fibroblasts causes severe histological changes in the intestines with a significant increase in stromal cell content and epithelial cell hyperproliferation, leading to numerous serrated polyps. This phenotype suggests that crucial changes occur in the fibroblast secretome that influences polyp development. Analyses of publicly available RNA expression databases identified CXCL12 as a potential candidate. RNAscope in situ hybridization showed an evident increase of Cxcl12-expressing fibroblasts. In vitro, stimulation of fibroblasts with BMPs resulted in downregulation of CXCL12, while inhibition of the BMP pathway resulted in gradual upregulation of CXCL12 over time. Moreover, neutralization of CXCL12 in vivo in the fibroblast-specific BMPR1A KO mice resulted in a significant decrease in polyp formation. Finally, in CRC patient specimens, mRNA-expression data showed that patients with high GREMLIN1 and CXCL12 expression had a significantly poorer overall survival. Significantly higher GREMLIN1, NOGGIN, and CXCL12 expression were detected in the Consensus Molecular Subtype 4 (CMS4) colorectal cancers, which are thought to arise from serrated polyps. Taken together, these data imply that fibroblast-specific BMP signaling–CXCL12 interaction could have a role in the etiology of serrated polyp formation.

Soluble guanylate cyclase stimulator praliciguat promotes ischemic leg reperfusion in db/db mice

Lower-limb peripheral artery disease (PAD) is a prevalent and challenging complication of diabetes, requiring innovating therapies. Praliciguat is an orally available stimulator of soluble guanylate cyclase (sGC) reported to have favorable effects on metabolic and hemodynamic endpoints in preclinical and clinical studies, suggesting the potential for benefit in PAD. We evaluated the effect of praliciguat on hindlimb ischemia recovery in a mouse model of diabetes and investigated the molecular mechanism of sGC stimulation. Hindlimb ischemia was induced in db/db mice by ligation and excision of the left femoral artery. Praliciguat 10 mg/kg/day ( n = 10 mice) or vehicle ( n = 10) were administered in the diet for 31 days starting 3 days before surgery. Foot perfusion was assessed with a Laser Doppler Imager and reported as a ratio in the ischemic versus non-ischemic limb. Ischemic leg function was assessed with a 4-point scale: 0, plantar/toe flexion in response to tail traction; 1, plantar but not toe flexion; 2, no flexion; 3, foot dragging. Ischemic foot perfusion and function were better 28 days after surgery in praliciguat than in vehicle treated mice (mean ± SD: perfusion 1.05 ± 0.23 vs. 0.38 ± 0.16; P < 0.0001; function 1.14 ± 0.36 vs. 1.73 ± 0.80; P = 0.03). Praliciguat did not impact angiogenesis. Arteriolar diameter was higher (9.88 ± 0.96 vs. 8.57 ± 0.64 μm; P = 0.004) and ICAM-1 expression lower (186 ± 41 vs. 403 ± 177% of healthy muscle; P = 0.005) in the ischemic limb of mice treated with praliciguat than with vehicle. Praliciguat attenuated accumulation of oxidative pro-angiogenic and pro-inflammatory muscle fibers. In cultured myoblasts praliciguat significantly downregulated Myh2 and Cxcl12 mRNA expression. Conditioned medium from praliciguat-treated myoblast decreased ICAM-1 mRNA expression in HUVECs. These results suggest that praliciguat restored perfusion and function in the ischemic muscle of db/db mice by increasing arteriolar diameter and decreasing ICAM-1 expression in endothelial cells via downregulation of Cxcl12 in myocytes.

450-P: Soluble Guanylate Cyclase Stimulator Praliciguat Promotes Ischemic Leg Reperfusion in db/db Mice

Background: Lower-limb peripheral artery disease (PAD) is a prevalent and challenging complication of diabetes, requiring innovating therapies. Praliciguat is an orally available stimulator of soluble guanylate cyclase reported to have favorable effects on metabolic and hemodynamic endpoints in preclinical and clinical studies, suggesting the potential for benefit in PAD. We evaluated the effect of praliciguat on hindlimb ischemia recovery in a mouse model of diabetes. Methods: Hindlimb ischemia was induced in db/db mice by ligation and excision of the left femoral artery. Praliciguat 10mg/kg/day (N=mice) or vehicle (N=10) were administered in the diet for 31 days. Foot perfusion was assessed with a Laser Doppler Imager and reported as a ratio in the ischemic versus non-ischemic limb. Ischemic leg function was assessed with a 4-point scale: 0, plantar/toe flexion in response to tail traction; 1, plantar but not toe flexion; 2, no flexion; 3, foot dragging. Results: Ischemic foot perfusion and function were better 28 days after surgery in praliciguat than in vehicle treated mice (mean ± SD: perfusion 1.± 0.23 vs. 0.38 ± 0.16; p&amp;lt;0.0001; function 1.14 ± 0.36 vs. 1.73 ± 0.80; p=0.03) . Praliciguat did not impact angiogenesis. Arteriolar diameter was higher (9.88 ± 0.96 vs. 8.57 ± 0.64 µm; p=0.004) and ICAM-1 expression lower (186 ± 41 vs. 403 ± 177 % of healthy muscle; p=0.005) in the ischemic limb of mice treated with praliciguat than with vehicle. Praliciguat attenuated accumulation of oxidative pro-angiogenic and pro-inflammatory muscle fibers. In cultured myoblasts praliciguat significantly downregulated Myh2 and Cxcl12 mRNA expression. Conditioned medium from praliciguat-treated myoblast decreased ICAM-1 mRNA expression in HUVECs. Conclusion: These results suggest that praliciguat restored perfusion and function in the ischemic muscle of db/db mice by increasing arteriolar diameter and decreasing ICAM-1 expression in endothelial cells via downregulation of Cxcl12 in myocytes. Disclosure N.Foussard: None. E.S.Buys: Employee; Cyclerion Therapeutics, Inc. K.Mohammedi: Board Member; Lilly, Novo Nordisk, Sanofi, Research Support; Cyclerion Therapeutics, Inc., Speaker's Bureau; Abbott, AstraZeneca. M.Renault: None.

Retracted] miR‑137 acts as a tumor suppressor in papillary thyroid carcinoma by targeting CXCL12.

Following the publication of this paper, it was drawn to the Editors' attention by a concerned reader that certain of the western blotting data shown in Figs.4D and 5B were strikingly similar to data appearing in different form in other articles by different authors. Owing to the fact that the contentious data in the above article had already been published elsewhere prior to its submission to Oncology Reports, the Editor has decided that this paper should be retracted from the Journal. After having been in contact with the authors, they agreed with the decision to retract the paper. The Editor apologizes to the readership for any inconvenience caused. [the original article was published in Oncology Reports 35: 2151-2158, 2016; DOI: 10.3892/or.2016.4604].

Bortezomib enhances G-CSF-induced hematopoietic stem cell mobilization by decreasing CXCL12 levels and increasing vascular permeability

Bortezomib (BTZ) is known to enhance the mobilization of hematopoietic stem and progenitor cells (HSPCs) induced by granulocyte colony-stimulating factor (G-CSF). However, the most effective time at which to administer BTZ to produce this enhancing effect remains debatable, and the precise mechanism underlying the effect of BTZ is poorly understood. We addressed these questions in this article by performing animal experiments. First, in agreement with previous studies, BTZ administration 12 hours before blood collection was most effective for HSPC mobilization; in contrast, BTZ administration 3 days before blood collection negatively affected HSPC harvesting. Next, in terms of the mechanism of action, G-CSF, but not BTZ, downregulated the expression of very late antigen-4 on HSPCs and vascular cell adhesion molecule-1 on bone marrow (BM) stromal cells; however, intriguingly, both G-CSF and BTZ downregulated CXCL12 chemokine expression in BM. Notably, BTZ treatment also increased BM vascular permeability. These results suggest that the pro-mobilization effect of BTZ could involve the dissociation of HSPCs from BM stromal cells triggered by G-CSF, vascular hyperpermeability elicited by BTZ, and downregulation of CXCL12 concomitantly induced by G-CSF and BTZ.

Apigenin Nanoparticle Attenuates Renal Ischemia/Reperfusion Inflammatory Injury by Regulation of miR-140-5p/CXCL12/NF-κB Signaling Pathway.

Apigenin as a natural flavonoid product has been proved previously to play a renoprotective effect during ischemia/reperfusion injury (IRI), but the particular mechanisms involving the positive effects of apigenin remain totally unclear. The study investigated apigenin's roles and underlying biological mechanisms in IR-induced acute kidney injury (AKI). Thirty-six mice received a right nephrectomy and clamping of the left renal artery for 30 minutes, and then perfusion for 24 h. Apigenin was loaded onto a biodegradable polymer carrier (nanoparticle) to enhance its bioavailability. Mice were subjected to intraperitoneally injection with apigenin (5, 10 or 20 mg/kg) for 24 h before surgery. For in vitro experiments, mouse renal tubular epithelial cells (mRTECs) and miR-140-5p mimic/inhibitor transfected mRTECs were subjected to hypoxia/reoxygenation in the presence or absence of apigenin. In vitro, we uncovered that hypoxia/reoxygenation stimulation caused inflammatory injury in mRTECs. Apigenin reduced the hypoxia/reoxygenation-induced cell inflammatory injury and NF- B p65 nuclear translocation from cytoplasm and activation. Moreover, apigenin reduced hypoxia/reoxygenationtriggered miR-140-5p down-regulation. What's more, the luciferase reporter system revealed that miR-140-5p negatively regulates CXCL12, which is its direct target of action. CXCL12 exhibited an inhibitory effect on the apigenin-induced inactivation of NF- B signaling pathway. Furthermore, we observed that apigenin pretreatment attenuated the IR-triggered up-regulation of serum creatinine and blood urea nitrogen, elevation of pro-inflammatory cytokines secretion and tubular cell apoptosis, enhancement of CXCL12 and decline of miR-140-5p in vivo. Our studies show that apigenin protects against IR-triggered renal cell inflammatory injury in vivo and in vitro by miR-140-5p up-regulation and CXCL12 downregulation via quenching the NF- B pathway activation. Apigenin may be an encouraging therapeutic agent for patients with IR-associated kidney injury.

Persistent DNA Damage and Senescence in the Placenta Impacts Developmental Outcomes of Embryos.

Cohesin is an evolutionarily conserved chromosome-associated protein complex essential for chromosome segregation, gene expression, and repair of DNA damage. Mutations that affect this complex cause the human developmental disorder Cornelia de Lange syndrome (CdLS), thought to arise from defective embryonic transcription. We establish a significant role for placental defects in the development of CdLS mouse embryos (Nipbl and Hdac8). Placenta is a naturally senescent tissue; we demonstrate that persistent DNA damage potentiates senescence and activates cytokine signaling. Mutant embryo developmental outcomes are significantly improved in the context of a wild-type placenta or by genetically restricting cytokine signaling. Our study highlights that cohesin is required for maintaining ploidy and the repair of spontaneous DNA damage in placental cells, suggesting that genotoxic stress and ensuing placental senescence and cytokine production could represent a broad theme in embryo health and viability.

Knock-out of Hopx disrupts stemness and quiescence of hematopoietic stem cells in mice.

HOPX is a stem cell marker in hair follicles and intestines. It was shown critical for primitive hematopoiesis. We previously showed an association between higher HOPX expression and clinical characteristics related to stemness and quiescence of leukemic cells in acute myeloid leukemia (AML) patients. To further explore its physiologic functions in hematopoietic system, we generated a mouse model with hematopoietic cell-specific knockout of Hopx (Hopx-/-). In young Hopx-/- mice, the hematopoietic stem cells (HSC) showed decreased reconstitution ability after serial transplantation. Further transcriptomic study revealed decreased HSC signatures in long-term HSCs from the Hopx-/- mice. At 18 months of age, half of the Hopx-/- mice developed cytopenia and splenomegaly. Bone marrow (BM) from the sick mice showed myeloid hyperplasia with predominant mature neutrophils, and decreased progenitor cells and lymphocytes. These phenotypes suggested critical functions of Hopx in maintaining HSC quiescence. Transcriptomic study of the Hopx-/- marrow cells showed significant downregulation of the Cxcl12-Cxcr4 axis, which is critical for maintenance of HSC quiescence. We next examined the role of Hopx in AML by using the MN1 overexpression murine leukemia model. Mice transplanted with MN1-overexpressed Hopx-/- BM cells developed AML with more aggressive phenotypes compared with those transplanted with MN1-overexpressed Hopx-wild cells. Hopx-/- MN1-overexpressed leukemia cells showed higher proliferation rate and downregulation of Cxcl12 and Cxcr4. Furthermore, in human AML, BM plasma CXCL12 levels were lower in patients with lower HOPX expression. In conclusion, our study highlights the roles of Hopx in maintenance of quiescence of the hematopoietic stem cells through CXCL12 pathway in vivo and provides implication of this protein in normal and malignant hematopoiesis.

Circular RNA circ_0020710 drives tumor progression and immune evasion by regulating the miR-370-3p/CXCL12 axis in melanoma

BackgroundCircular RNAs (circRNAs) have been reported to have critical regulatory roles in tumor biology. However, their contribution to melanoma remains largely unknown.MethodsCircRNAs derived from oncogene CD151 were detected and verified by analyzing a large number of melanoma samples through quantitative real-time polymerase chain reaction (qRT-PCR). Melanoma cells were stably transfected with lentiviruses using circ_0020710 interference or overexpression plasmid, and then CCK-8, colony formation, wound healing, transwell invasion assays, and mouse xenograft models were employed to assess the potential role of circ_0020710. RNA immunoprecipitation, luciferase reporter assay and fluorescence in situ hybridization were used to evaluate the underlying mechanism of circ_0020710.ResultsOur findings indicated that circ_0020710 was generally overexpressed in melanoma tissues, and high level of circ_0020710 was positively correlated with malignant phenotype and poor prognosis of melanoma patients. Elevated circ_0020710 promoted melanoma cell proliferation, migration and invasion in vitro as well as tumor growth in vivo. Mechanistically, we found that high level of circ_0020710 could upregulate the CXCL12 expression via sponging miR-370-3p. CXCL12 downregulation could reverse the malignant behavior of melanoma cells conferred by circ_0020710 over expression. Moreover, we also found that elevated circ_0020710 was correlated with cytotoxic lymphocyte exhaustion, and a combination of AMD3100 (the CXCL12/CXCR4 axis inhibitor) and anti-PD-1 significantly attenuated tumor growth.ConclusionsElevated circ_0020710 drives tumor progression via the miR-370-3p/CXCL12 axis, and circ_0020710 is a potential target for melanoma treatment.

Common and different alterations of bone marrow mesenchymal stromal cells in myelodysplastic syndrome and multiple myeloma.

ObjectiveThe objective of this study was to explore characteristics of bone marrow mesenchymal stromal cells (BM‐MSCs) derived from patients with myelodysplastic syndrome (MDS) and multiple myeloma (MM).MethodsBM‐MSCs were recovered from 17 of MDS patients, 23 of MM patients and 9 healthy donors and were passaged until proliferation stopped. General characteristics and gene expression profiles of MSCs were analysed. In vitro, ex vivo coculture, immunohistochemistry and knockdown experiments were performed to verify gene expression changes.ResultsBM‐MSCs failed to culture in 35.0% of patients and 50.0% of recovered BM‐MSCs stopped to proliferate before passage 6. MDS‐ and MM‐MSCs shared characteristics including decreased osteogenesis, increased angiogenesis and senescence‐associated molecular pathways. In vitro and ex vivo experiments showed disease‐specific changes such as neurogenic tendency in MDS‐MSCs and cardiomyogenic tendency in MM‐MSCs. Although the age of normal control was younger than patients and telomere length was shorter in patient's BM‐MSCs, they were not different according to disease category nor degree of proliferation. Specifically, poorly proliferation BM‐MSCs showed CDKN2A overexpression and CXCL12 downregulation. Immunohistochemistry of BM biopsy demonstrated that CDKN2A was intensely accumulation in perivascular BM‐MSCs failed to culture. Interestingly, patient's BM‐MSCs revealed improved proliferation activity after CDKN2A knockdown.ConclusionThese results collectively indicate that MDS‐MSCs and MM‐MSCs have common and different alterations at various degrees. Hence, it is necessary to evaluate their alteration status using representative markers such as CDKN2A expression.

Loss of CXCL12/CXCR4 signalling impacts several aspects of cardiovascular development but does not exacerbate Tbx1 haploinsufficiency

The CXCL12-CXCR4 pathway has crucial roles in stem cell homing and maintenance, neuronal guidance, cancer progression, inflammation, remote-conditioning, cell migration and development. Recently, work in chick suggested that signalling via CXCR4 in neural crest cells (NCCs) has a role in the 22q11.2 deletion syndrome (22q11.2DS), a disorder where haploinsufficiency of the transcription factor TBX1 is responsible for the major structural defects. We tested this idea in mouse models. Our analysis of genes with altered expression in Tbx1 mutant mouse models showed down-regulation of Cxcl12 in pharyngeal surface ectoderm and rostral mesoderm, both tissues with the potential to signal to migrating NCCs. Conditional mutagenesis of Tbx1 in the pharyngeal surface ectoderm is associated with hypo/aplasia of the 4th pharyngeal arch artery (PAA) and interruption of the aortic arch type B (IAA-B), the cardiovascular defect most typical of 22q11.2DS. We therefore analysed constitutive mouse mutants of the ligand (CXCL12) and receptor (CXCR4) components of the pathway, in addition to ectodermal conditionals of Cxcl12 and NCC conditionals of Cxcr4. However, none of these typical 22q11.2DS features were detected in constitutively or conditionally mutant embryos. Instead, duplicated carotid arteries were observed, a phenotype recapitulated in Tie-2Cre (endothelial) conditional knock outs of Cxcr4. Previous studies have demonstrated genetic interaction between signalling pathways and Tbx1 haploinsufficiency e.g. FGF, WNT, SMAD-dependent. We therefore tested for possible epistasis between Tbx1 and the CXCL12 signalling axis by examining Tbx1 and Cxcl12 double heterozygotes as well as Tbx1/Cxcl12/Cxcr4 triple heterozygotes, but failed to identify any exacerbation of the Tbx1 haploinsufficient arch artery phenotype. We conclude that CXCL12 signalling via NCC/CXCR4 has no major role in the genesis of the Tbx1 loss of function phenotype. Instead, the pathway has a distinct effect on remodelling of head vessels and interventricular septation mediated via CXCL12 signalling from the pharyngeal surface ectoderm and second heart field to endothelial cells.

Mesenchymal stromal cells induce a permissive state in the bone marrow that enhances G-CSF-induced hematopoietic stem cell mobilization in mice

Mesenchymal stromal cells (MSCs) support hematopoietic stem cells (HSCs) in vivo and enhance HSC engraftment and hematopoietic recovery upon cotransplantation with HSCs. These data have led to the hypothesis that MSCs may affect the HSC niche, leading to changes in HSC retention and trafficking. We studied the effect of MSC administration on the HSC compartment in the bone marrow (BM) in mice. After injection of MSCs, HSC numbers in the BM were decreased coinciding with an increased cell cycle activity compared with phosphate-buffered saline (PBS)-injected controls. Furthermore, the frequency of macrophages was significantly reduced and niche factors including Cxcl12, Scf, and Vcam were downregulated in endosteal cells. These BM changes are reminiscent of events associated with granulocyte colony-stimulating factor (G-CSF)-induced hematopoietic stem and progenitor cell (HSPC) mobilization. Interestingly, coadministration of MSCs and G-CSF resulted in a twofold increase in peripheral blood HSPC release compared with injection of G-CSF alone, whereas injection of MSCs alone did not induce HSPC mobilization. After intravenous administration, MSCs were only observed in the lungs, suggesting that they exert their effect on the HSC niche through a soluble mediator. Therefore, we tested the hypothesis that MSC-derived extracellular vesicles (EVs) are responsible for the observed changes in the HSC niche. Indeed, administration of EVs resulted in downregulation of Cxcl12, Scf, and Vcam and enhanced G-CSF-induced HSPC mobilization at similar levels as MSCs and G-CSF. Together, these data indicate that MSCs induce a permissive state in the BM, enhancing HSPC mobilization through the release of EVs.

Abstract 057: Adenosine Kinase Epigenetically Regulates Abdominal Aortic Aneurysm Formation

Objectives: Abdominal aortic aneurysm (AAA) is a major cause of morbidity and mortality worldwide; however, the molecular mechanisms involved in AAA formation are not well understood. The nucleoside adenosine plays important roles in modulating vascular homeostasis. In this study, we sought to determine whether adenosine kinase (ADK), the adenosine-metabolizing enzyme, modulates AAA formation via control of intracellular adenosine level and investigate the involvement of ADK-mediated epigenetic mechanism in this aortic disease. Methods and results: ADK expression and activity were increased in murine AAA models, including calcium chloride-stimulated AAA and angiotensin II-induced AAA. Using a loss-of-function genetic mouse model, we demonstrated that genetic ADK knockout mice led to increased Intracellular adenosine level in macrophages and vascular cells and developed significantly smaller aortic expansion when subjected to AAA inductions. Notably, knockout of ADK alleviated arterial inflammation and diminished infiltration of macrophages, as well as suppressed arterial extracellular matrix degradation, which was associated with down-regulation of CXCL12, MMP2/9 and adhesion molecule expression. Mechanistically, elevation of intracellular adenosine by genetic inactivation of ADK or exogenous adenosine reduces activation of the transmethylation pathway via inactivation of SAH hydrolase (SAHH) and histone H3K4 methyltransferase (HMT), thus down-regulating expression and signaling of mitogen-activated protein kinases in activated macrophages and vascular cells with pro-inflammatory stimuli. Blocking of the H3K4 transmethylation pathway by knockdown of WDR5, a core subunit of HMT complex, abrogated the beneficial effects of ADK inactivation. Conclusions: Our findings reveal a previously unrecognized role of ADK mediated epigenetic pathways in the pathogenesis of AAA and provides a therapeutic target for the prevention of AAA.

Histone hypoacetylation contributes to CXCL12 downregulation in colon cancer: impact on tumor growth and cell migration.

CXCL12 has been shown to be involved in colon cancer metastasis, but its expression level and molecular mechanisms regulating its expression remain controversial. We thus evaluated CXCL12 expression in a large cohort of colon adenomas and carcinomas, investigated for an epigenetic mechanism controlling its expression and evaluated the impact of CXCL12 levels on cell migration and tumor growth. CXCL12 expression was measured in human colon adenomas and carcinomas with transcriptome array and RT-qPCR. The promoter methylation was analyzed with whole-genome DNA methylation chips and protein expression by immunohistochemistry. We confirm a reduced expression of CXCL12 in 75% of MSS carcinomas and show that the decrease is an early event as already present in adenomas. The methylome analysis shows that the CXCL12 promoter is methylated in only 30% of microsatellite-stable tumors. In vitro, treatments with HDAC inhibitors, butyrate and valproate restored CXCL12 expression in three colon cell lines, increased acetylation of histone H3 within the CXCL12 promoter and inhibited cell migration. In vivo, valproate diminished (65%) the number of intestinal tumors in APC mutant mice, slowed down xenograft tumor growth concomitant to restored CXCL12 expression. Finally we identified loss of PCAF expression in tumor samples and showed that forced expression of PCAF in colon cancer cell lines restored CXCL12 expression. Thus, reduced PCAF expression may participate to CXCL12 promoter hypoacetylation and its subsequent loss of expression. Our study is of potential clinical interest because agents that promote or maintain histone acetylation through HDAC inhibition and/or HAT stimulation, may help to lower colon adenoma/carcinoma incidence, especially in high-risk families, or could be included in therapeutic protocols to treat advanced colon cancer.

CXCL12 methylation-mediated epigenetic regulation of gene expression in papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer, and its incidence rate is rapidly growing. It is necessary to understand the pathogenesis of PTC to develop effective diagnosis methods. Promoter methylation has been recognized to contribute to the alterations in gene expression observed in tumorigenesis. Our RNA-seq data identified 1191 differentially expressed mRNAs and 147 differentially expressed lncRNAs in PTC. Next, promoter methylation of these genes was detected by reduced representation bisulfite sequencing (RRBS) technology and comprehensively analyzed to identify differential methylation. In total, 14 genes (13 mRNAs and 1 lncRNA), in which methylation was intimately involved in regulating gene expression, were proposed as novel diagnostic biomarkers. To gain insights into the relationships among these 14 genes, a core co-function network was constructed based on co-expression, co-function and co-methylation data. Notably, CXCL12 was identified as an essential gene in the network that was closely connected with the other genes. These data suggested that CXCL12 down-regulation in PTC may be caused by promoter hypermethylation. Our study was the first to perform an RRBS analysis for PTC and suggested that CXCL12 may contribute to PTC development by methylation-mediated epigenetic regulation of gene expression.

Downregulation of CXCL12 in mesenchymal stromal cells by TGF\u03b2 promotes breast cancer metastasis

Mesenchymal stromal cells (MSCs) are one of major components of the tumour microenvironment. Recent studies have shown that MSC tumour residence and their close interactions with inflammatory factors are important factors that affect tumour progression. Among tumour-associated inflammatory factors, transforming growth factor β (TGFβ) is regarded as a key determinant of malignancy. By employing a lung metastasis model of a murine breast cancer, we show here that the prometastatic effect of MSCs was dependent on their response to TGFβ. Interestingly, we found that MSC-produced CXCL12, an important chemokine in tumour metastasis, was markedly inhibited by TGFβ. Furthermore, silencing of CXCL12 in TGFβ-unresponsive MSCs restored their ability to promote tumour metastasis. We found that 4T1 breast cancer cells expressed high levels of CXCR7, but not of CXCR4, both of which are CXCL12 receptors. In presence of CXCL12, CXCR7 expression on tumour cells was decreased. Indeed, when CXCR7 was silenced in breast cancer cells, their metastatic ability was inhibited. Therefore, our data demonstrated that sustained expression of CXCL12 by MSCs in the primary tumour site inhibits metastasis through reduction of CXCR7, while, in the presence of TGFβ, this CXCL12 effect of MSCs on tumour cells is relieved. Importantly, elevated CXCR7 and depressed CXCL12 expression levels were prominent features of clinical breast cancer lesions and were related significantly with poor survival. Our findings reveal a novel mechanism of MSC effects on malignant cells through which crosstalk between MSCs and TGFβ regulates tumour metastasis.