Abstract 473: Differential Regulation of Sk Channels by CamKII and Pyk2 Under Adrenergic Stimulation

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Radmila Terentyeva ◽  
Iuliia Polina ◽  
Shanna Hamilton ◽  
Karim Roder ◽  
Gideon Koren ◽  
...  
Keyword(s):  
Cardiac Disease ◽  
Tyrosine Kinases ◽  
Therapeutic Potential ◽  
Sk Channels ◽  
Adrenergic Stimulation ◽  
Negative Effects ◽  
Expression Levels ◽  
Repolarization Reserve ◽  
Voltage Dependent ◽  
Ca Sensitivity

Introduction: Small conductance calcium (Ca)-activated K (SK) channels present in the plasmalemma of ventricular cardiomyocytes (VCMs) are dormant in health and become functional in cardiac disease. We recently showed that SK channels contribute to VCM repolarization in a rat model of hypertrophy induced by thoracic aortic banding (TAB), despite reduced expression levels, suggestive of increased activity of the channels. However, the mechanisms responsible for disease-associated functional upregulation of the channels are yet to be defined. Hypothesis: Functional recruitment of SK channels in cardiac hypertrophy is caused by enhancement of adrenergic signaling cascades. Methods: The effects of α1 adrenergic stimulation by phenylephrine (10 μM) + propranolol (100 μM) were studied in patch-clamped rat VCMs overexpressing rat SK2 after 48 hrs in culture. Calcium transients were recorded simultaneously using confocal microscopy and were used as a ramp [Ca] to assess possible changes in Ca sensitivity of the channel. Phosphorylation of SKs by Ser/Thr and tyrosine kinases, phosphorylation of Calmodulin at Thr-79, expression levels and phosphorylation of CaMKII and tyrosine kinase Pyk2 were assessed in cultured rat VCMs and freshly isolated VCMs from TABs and Shams using Western blot analysis. Results: WB analysis showed increased Ser/Thr and Tyr phosphorylation of SK2 in TABs. Alpha1 stimulation of rat VCMs overexpressing rat SK2 mimicked this pattern, increasing I SK at high voltages in parallel with the increase in Ca transient amplitude and reduction in Ca sensitivity of the channels. Overexpression of Pyk2 inhibitor CRNK did not restore I SK despite reduction in Ca transient amplitude because of attenuating α1-agonist mediated decrease in Ca sensitivity of SKs. Application of CaMKII inhibitor KN93 fully reversed α1-mediated I SK increase at high voltages without affecting Ca sensitivity of the channel. Conclusion: Upregulation of SKs in hypertrophic hearts is likely caused by CaMKII-dependent phosphorylation which reduces voltage-dependent block of the channels. Pyk2 inhibition may present therapeutic potential by attenuating negative effects on SK Ca sensitivity thereby increasing repolarization reserve diminished in cardiac disease.

scholarly journals Small Conductance Ca2 +-Activated K+ (SK) Channel mRNA Expression in Human Atrial and Ventricular Tissue: Comparison Between Donor, Atrial Fibrillation and Heart Failure Tissue

2021 ◽  
Vol 12 ◽  
Author(s):  
Elisa Darkow ◽  
Thong T. Nguyen ◽  
Marina Stolina ◽  
Fabian A. Kari ◽  
Constanze Schmidt ◽  
...  
Keyword(s):  
Heart Failure ◽  
Atrial Fibrillation ◽  
Sinus Rhythm ◽  
Cardiac Disease ◽  
Differentially Expressed ◽  
Sk Channels ◽  
Expression Levels ◽  
Ventricular Tissue ◽  
Small Conductance ◽  
Selective Target

In search of more efficacious and safe pharmacological treatments for atrial fibrillation (AF), atria-selective antiarrhythmic agents have been promoted that target ion channels principally expressed in the atria. This concept allows one to engage antiarrhythmic effects in atria, but spares the ventricles from potentially proarrhythmic side effects. It has been suggested that cardiac small conductance Ca2+-activated K+ (SK) channels may represent an atria-selective target in mammals including humans. However, there are conflicting data concerning the expression of SK channels in different stages of AF, and recent findings suggest that SK channels are upregulated in ventricular myocardium when patients develop heart failure. To address this issue, RNA-sequencing was performed to compare expression levels of three SK channels (KCNN1, KCNN2, and KCNN3) in human atrial and ventricular tissue samples from transplant donor hearts (no cardiac disease), and patients with cardiac disease in sinus rhythm or with AF. In addition, for control purposes expression levels of several genes known to be either chamber-selective or differentially expressed in AF and heart failure were determined. In atria, as compared to ventricle from transplant donor hearts, we confirmed higher expression of KCNN1 and KCNA5, and lower expression of KCNJ2, whereas KCNN2 and KCNN3 were statistically not differentially expressed. Overall expression of KCNN1 was low compared to KCNN2 and KCNN3. Comparing atrial tissue from patients with AF to sinus rhythm samples we saw downregulation of KCNN2 in AF, as previously reported. When comparing ventricular tissue from heart failure patients to non-diseased samples, we found significantly increased ventricular expression of KCNN3 in heart failure, as previously published. The other channels showed no significant difference in expression in either disease. Our results add weight to the view that SK channels are not likely to be an atria-selective target, especially in failing human hearts, and modulators of these channels may prove to have less utility in treating AF than hoped. Whether targeting SK1 holds potential remains to be elucidated.

Wogonin preferentially kills malignant lymphocytes and suppresses T-cell tumor growth by inducing PLCγ1- and Ca2+-dependent apoptosis

Blood ◽  
2008 ◽  
Vol 111 (4) ◽  
pp. 2354-2363 ◽  
Author(s):  
Sven Baumann ◽  
Stefanie C. Fas ◽  
Marco Giaisi ◽  
Wolfgang W. Müller ◽  
Anette Merling ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Chinese Medicine ◽  
Traditional Chinese Medicine ◽  
Therapeutic Potential ◽  
Human T Cell ◽  
Voltage Dependent ◽  
Ca2 Channels ◽  
Malignant T Cells

Herbs have successfully been used in traditional Chinese medicine for centuries. However, their curative mechanisms remain largely unknown. In this study, we show that Wogonin, derived from the traditional Chinese medicine Huang-Qin (Scutellaria baicalensis Georgi), induces apoptosis in malignant T cells in vitro and suppresses growth of human T-cell leukemia xenografts in vivo. Importantly, Wogonin shows almost no toxicity on T lymphocytes from healthy donors. Wogonin induces prolonged activation of PLCγ1 via H2O2 signaling in malignant T cells, which leads to sustained elevation of cytosolic Ca2+ in malignant but not normal T cells. Subsequently, a Ca2+ overload leads to disruption of the mitochondrial membrane. The selective effect of Wogonin is due to its differential regulation of the redox status of malignant versus normal T cells. In addition, we show that the L-type voltage-dependent Ca2+ channels are involved in the intracellular Ca2+ mobilization in T cells. Furthermore, we show that malignant T cells possess elevated amounts of voltage-dependent Ca2+ channels compared with normal T cells, which further enhance the cytotoxicity of Wogonin for malignant T cells. Taken together, our data show a therapeutic potential of Wogonin for the treatment of hematologic malignancies.

GlcNAc is a mast-cell chromatin-remodeling oncometabolite that promotes systemic mastocytosis aggressiveness

Blood ◽  
2021 ◽  
Author(s):  
Julie Agopian ◽  
Quentin Da Costa ◽  
Quang Vo Nguyen ◽  
Giulia Scorrano ◽  
Paraskevi Kousteridou ◽  
...  
Keyword(s):  
Mouse Model ◽  
Tyrosine Kinases ◽  
Inflammatory Responses ◽  
Immunoglobulin E ◽  
Therapeutic Potential ◽  
Systemic Mastocytosis ◽  
High Plasma ◽  
Humanized Mouse Model ◽  
Acute Response ◽  
Genes Encoding

Systemic mastocytosis (SM) is a KIT-driven hematopoietic neoplasm characterized by the excessive accumulation of neoplastic mast cells (MCs) in various organs and, mainly, the bone marrow (BM). Multiple genetic and epigenetic mechanisms contribute to the onset and severity of SM. However, little is known to date about the metabolic underpinnings underlying SM aggressiveness, which has thus far impeded the development of strategies to leverage metabolic dependencies when existing KIT-targeted treatments fail. Here, we show that plasma metabolomic profiles were able to discriminate indolent from advanced forms of the disease. We identified N-acetyl-D-glucosamine (GlcNAc) as the most predictive metabolite of SM severity. High plasma levels of GlcNAc in patients with advanced SM correlated with the activation of the GlcNAc-fed hexosamine biosynthesis pathway (HBP) in patients BM aspirates and purified BM MCs. At the functional level, GlcNAc enhanced human neoplastic MCs proliferation and promoted rapid health deterioration in a humanized mouse model of SM. In addition, in the presence of GlcNAc, immunoglobulin E-stimulated MCs triggered enhanced release of proinflammatory cytokines and a stronger acute response in a mouse model of passive cutaneous anaphylaxis. Mechanistically, elevated GlcNAc levels promoted the transcriptional accessibility of chromatin regions that contain genes encoding mediators of receptor tyrosine kinases cascades and inflammatory responses, thus leading to a more aggressive phenotype. Therefore, GlcNAc is an oncometabolite driver of SM aggressiveness. This study suggests the therapeutic potential for targeting metabolic pathways in MC-related diseases to manipulate MCs effector functions.

scholarly journals Therapeutic Potential of Thrombomodulin in Renal Fibrosis of Nephrotoxic Serum Nephritis in Wistar-Kyoto Rats

2020 ◽  
Vol 45 (3) ◽  
pp. 391-406
Author(s):  
Nobuhiro Kanazawa ◽  
Masayuki Iyoda ◽  
Shohei Tachibana ◽  
Kei Matsumoto ◽  
Yukihiro Wada ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Renal Fibrosis ◽  
Therapeutic Potential ◽  
The Body ◽  
Expression Levels ◽  
Nephrotoxic Serum Nephritis ◽  
Collagen Iii ◽  
Wistar Kyoto ◽  
Mrna Expression Levels

Background: Recombinant human soluble thrombomodulin (rhTM) was approved in 2008 and has been used for treatment of disseminated intravascular coagulation in Japan. The antifibrotic effects of rhTM in acute exacerbation of idiopathic pulmonary fibrosis are well established, but the therapeutic potential of rhTM in renal fibrosis remains poorly understood. Methods: Nephrotoxic serum nephritis (NTS-N) was induced in 22 female Wistar-Kyoto (WKY) rats on day 0. Rats were administered either rhTM or vehicle intraperitoneally, every day from day 4 to day 55. Rats were sacrificed on day 56 when renal fibrosis was established and renal morphological investigations were performed. In vitro, rat renal fibroblasts (NRK-49F) were pretreated with rhTM or saline, and expression levels of profibrogenic gene induced by thrombin were analyzed by real-time reverse transcription polymerase chain reaction. Results: Compared to WKY-GN-vehicle rats, the body weights of WKY-GN-rhTM rats were significantly greater on day 55. By day 56, rhTM had significantly reduced serum creatinine levels in NTS-N. On the other hand, urinary protein excretion was comparable between the two treatment groups throughout the study. The percentage of Masson trichrome-positive areas in WKY-GN-rhTM rats was significantly lower compared to that in WKY-GN-vehicle rats. Glomerular fibrin deposition was significantly reduced in WKY-GN-rhTM rats. In addition, rhTM significantly reduced the renal cortical mRNA expression levels of TNF-α, Toll-like receptor 4, MYD88, TGF-β, αSMA, collagen I, collagen III, fibronectin, and protease-activated receptor 1 (PAR1), a thrombin receptor. In vitro, thrombin stimulation of NRK-49F cells significantly enhanced the mRNA expression levels of αSMA and PAR1, and these upregulations were significantly reduced by pretreatment with rhTM. Conclusions: Administration of rhTM after establishment of crescentic glomerulonephritis (GN) attenuated the subsequent development of renal fibrosis in NTS-N, possibly in part by inhibiting thrombin-mediated fibrogenesis. Our results suggest that rhTM may offer a therapeutic option for limiting the progression of chronic kidney disease in crescentic GN.

scholarly journals Ribosomal stress-surveillance: three pathways is a magic number

2020 ◽  
Vol 48 (19) ◽  
pp. 10648-10661 ◽  
Author(s):  
Anna Constance Vind ◽  
Aitana Victoria Genzor ◽  
Simon Bekker-Jensen
Keyword(s):  
Stress Response ◽  
Stress Responses ◽  
Map Kinases ◽  
Cell Function ◽  
Therapeutic Potential ◽  
Magic Number ◽  
Physiological Role ◽  
Negative Effects ◽  
Mitogen Activated Protein ◽  
Activation Mechanisms

Abstract Cells rely on stress response pathways to uphold cellular homeostasis and limit the negative effects of harmful environmental stimuli. The stress- and mitogen-activated protein (MAP) kinases, p38 and JNK, are at the nexus of numerous stress responses, among these the ribotoxic stress response (RSR). Ribosomal impairment is detrimental to cell function as it disrupts protein synthesis, increase inflammatory signaling and, if unresolved, lead to cell death. In this review, we offer a general overview of the three main translation surveillance pathways; the RSR, Ribosome-associated Quality Control (RQC) and the Integrated Stress Response (ISR). We highlight recent advances made in defining activation mechanisms for these pathways and discuss their commonalities and differences. Finally, we reflect on the physiological role of the RSR and consider the therapeutic potential of targeting the sensing kinase ZAKα for treatment of ribotoxin exposure.

scholarly journals ERK5 Phosphorylates Kv4.2 and Inhibits Inactivation of the A-Type Current in PC12 Cells

2018 ◽  
Vol 19 (7) ◽  
pp. 2008 ◽  
Author(s):  
Yurina Kashino ◽  
Yutaro Obara ◽  
Yosuke Okamoto ◽  
Takeo Saneyoshi ◽  
Yasunori Hayashi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Pc12 Cells ◽  
Sympathetic Neurons ◽  
Membrane Excitability ◽  
Expression Levels ◽  
Catecholamine Biosynthesis ◽  
Protein Levels ◽  
Whole Cell Patch Clamp ◽  
Gene And Protein Expression ◽  
Voltage Dependent

Extracellular signal-regulated kinase 5 (ERK5) regulates diverse physiological responses such as proliferation, differentiation, and gene expression. Previously, we demonstrated that ERK5 is essential for neurite outgrowth and catecholamine biosynthesis in PC12 cells and sympathetic neurons. However, it remains unclear how ERK5 regulates the activity of ion channels, which are important for membrane excitability. Thus, we examined the effect of ERK5 on the ion channel activity in the PC12 cells that overexpress both ERK5 and the constitutively active MEK5 mutant. The gene and protein expression levels of voltage-dependent Ca2+ and K+ channels were determined by RT-qPCR or Western blotting. The A-type K+ current was recorded using the whole-cell patch clamp method. In these ERK5-activated cells, the gene expression levels of voltage-dependent L- and P/Q-type Ca2+ channels did not alter, but the N-type Ca2+ channel was slightly reduced. In contrast, those of Kv4.2 and Kv4.3, which are components of the A-type current, were significantly enhanced. Unexpectedly, the protein levels of Kv4.2 were not elevated by ERK5 activation, but the phosphorylation levels were increased by ERK5 activation. By electrophysiological analysis, the inactivation time constant of the A-type current was prolonged by ERK5 activation, without changes in the peak current. Taken together, ERK5 inhibits an inactivation of the A-type current by phosphorylation of Kv4.2, which may contribute to the neuronal differentiation process.

Protein Kinase Gene Expression Profile in Adult Acute Lymphocytic Leukemia (ALL): Identification of Novel Therapeutic Targets.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1824-1824
Author(s):  
Monica Messina ◽  
Sabina Chiaretti ◽  
Simona Tavolaro ◽  
Irene Della Starza Miss ◽  
Antonella Vitale ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Targeted Therapies ◽  
Tyrosine Kinases ◽  
Acute Lymphocytic Leukemia ◽  
Lymphocytic Leukemia ◽  
High Expression ◽  
Expression Levels ◽  
Tk Inhibitors ◽  
B Lineage ◽  
The Impact

Abstract Background. Despite the recent improvements in the treatment of acute lymphocytic leukemia (ALL), adults still have a poor outcome. The future of ALL management is likely to rely in the progressive introduction of novel targeted therapies. Protein kinase (PK) deregulation has been frequently observed in cancer; therefore, PK are regarded as attractive targets for anti-tumor therapies. The majority of PK inhibitors currently used in clinical trials in onco-hematology targets tyrosine kinases (TK) and receptor tyrosine kinases (RTK). Methods. We evaluated the expression levels of PK genes in 133 adult ALL samples at the onset of the disease by oligonucleotide arrays (HGU133 Plus 2.0, Affymetrix). Leukemic cells from 91 samples were of B-cell origin and belonged to 4 molecular subgroups: BCR/ABL+ (40 pts), ALL1/AF4+ (5 pts), E2A/PBX+ (3 pts) and B-lineage ALL without known molecular abnormalities (43 pts), defined as B-NEG. The remaining 42 samples were of T-cell derivation. To compare the 5 ALL subgroups we performed an ANOVA analysis using a list of 1324 probesets coding for PK. The genes identified by ANOVA were further selected (mean expression values ≥300, fold change difference ≥1.5 in each group compared to every other group) to concentrate on distinguishing PK genes. This approach identified a set of distinctive PK for each ALL subgroup except for the B-NEG samples. To further investigate the B-NEG group we compared it with every other B-lineage ALL subset by t test using the aforementioned gene list and highlighted the genes that were overexpressed in this group when compared to at least two other subgroups. Results. ANOVA identified 290 probesets differentially expressed among the 5 ALL subgroups. The selection criteria applied allowed to identify the PK genes distinctive of each group and to highlight those of particular interest, as TK and RTK. T-ALL and E2A/PBX+ ALL were characterized by the specific expression of 18 PK genes. T-ALL showed a high expression of ZAP-70, LCK, ITK, EPHB6, FGFR1 and RYK. MERTK, BLK, TNK2 were distinctive of the E2A/PBX+ group. Fifteen genes were specific of the ALL1/AF4+ samples: among these, FLT3, ILK and LTK were selected. Only 8 genes were specifically overexpressed in the BCR/ABL+ samples; apart from ABL, this group showed high expression levels of FYN. Although no PK was exclusively upregulated in the B-NEG cases, a consistent number of PK genes was overexpressed in these samples. Conclusions. Our study indicates that each ALL subgroup shows a distinctive PK signature. The specific PK subsets identified include several TK and RTK genes - especially in T-ALL, and in the E2A/PBX+ and B-NEG groups - whose products may be suitable for targeted therapies. These results suggest that second generation TK inhibitors may be effective not only in BCR/ABL+ patients, but also in other ALL subsets, such as T-ALL, e2a/pbx+ and B-NEG ALL, and provide the rationale for testing the impact of currently available TK inhibitors in the management of adult ALL.

scholarly journals Tyrosine kinases play a permissive role in glucose-induced insulin secretion from adult rat islets

1999 ◽  
Vol 22 (1) ◽  
pp. 19-28 ◽  
Author(s):  
SJ Persaud ◽  
TE Harris ◽  
CJ Burns ◽  
PM Jones
Keyword(s):  
Insulin Secretion ◽  
Tyrosine Phosphorylation ◽  
Beta Cells ◽  
Tyrosine Kinases ◽  
Pancreatic Beta Cells ◽  
Tyrosine Phosphatase ◽  
Serine Threonine Kinase ◽  
Protein Tyrosine ◽  
Adult Rat ◽  
Voltage Dependent

The role(s) played by protein tyrosine kinases (PTKs) in the regulation of insulin secretion from pancreatic beta cells is not clear. We have examined the effects of glucose, the major physiological insulin secretagogue, on the tyrosine phosphorylation state of islet proteins, and assessed beta cell insulin secretory responses in the presence of PTK inhibitors. Under basal conditions islets contained many proteins phosphorylated on tyrosine residues, and glucose (20 mM; 5-15 min) was without demonstrable effect on the pattern of tyrosine phosphorylation, in either the absence or presence of the protein tyrosine phosphatase (PTP) inhibitor, sodium pervanadate (PV). PV alone (100 microM) increased tyrosine phosphorylation of several islet proteins. The PTK inhibitors genistein (GS) and tyrphostin A47 (TA47) inhibited islet tyrosine kinase activities and glucose-, 4alpha ketoisocaproic acid (KIC)- and sulphonylurea-stimulated insulin release, without affecting glucose metabolism. GS and TA47 also inhibited protein serine/threonine kinase activities to a limited extent, but had no effect on Ca2+, cyclic AMP- or phorbol myristate acetate (PMA)-induced insulin secretion from electrically permeabilised islets. These results suggest that PTK inhibitors exert their inhibitory effects on insulin secretion proximal to Ca2+ entry and it is proposed that they act at the site of the voltage-dependent Ca2+ channel which regulates Ca2+ influx into beta cells following nutrient- and sulphonylurea-induced depolarisation.

scholarly journals Prognostic value of α2δ1 in hypopharyngeal carcinoma: A retrospective study

Open Medicine ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. 1395-1402
Author(s):  
Qiang Liu ◽  
Yanbo Dong ◽  
Shuoqing Yuan ◽  
Minghang Yu ◽  
Liangfa Liu ◽  
...  
Keyword(s):  
Prognostic Value ◽  
Cox Regression ◽  
Progression Free Survival ◽  
Clinicopathological Characteristics ◽  
Hypopharyngeal Carcinoma ◽  
Free Survival ◽  
Expression Levels ◽  
Normal Tissues ◽  
Voltage Dependent ◽  
Tumor Types

Abstract Voltage-dependent calcium channel subunit alpha-2/delta-1 (α2δ1) has been identified as a marker of cancer stem cells in multiple malignant tumor types. However, α2δ1’s role in the prognosis of hypopharyngeal squamous cell carcinoma (HSCC) was not reported. In our study, ten pairs of HSCC and peritumoral normal tissues were used for immunohistochemistry assessment. And α2δ1 expression levels of 34 more HSCC samples were also evaluated, represented by the integral optic density using Image-Pro Plus. Clinicopathological associations and prognostic value of α2δ1 were analyzed. As a result, α2δ1 expression was frequently increased in HSCC tissues. Although the correlation between patients’ clinicopathological characteristics and their α2δ1 expression levels was not significant, α2δ1 expression was significantly correlated with unfavorable overall survival (OS) (P = 0.018) and progression-free survival (PFS) (P = 0.023). Univariate and multivariate cox regression analyses suggested α2δ1’s prognostic role for both OS and PFS (P = 0.013 and 0.011, respectively). This study specifically demonstrated that α2δ1 regularly increased in HSCC compared with peritumoral tissues, and α2δ1 could act as a promising prognostic marker in HSCC patients.

scholarly journals The Molecular Pathogenesis of Haemangioma

2021 ◽  
Author(s):  
◽  
Anasuya Vishvanath
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinases ◽  
Molecular Mechanisms ◽  
Therapeutic Potential ◽  
Primary Tumour ◽  
Treatment Options ◽  
Janus Kinase ◽  
Stem Cell Population ◽  
Induced Apoptosis

<p>Haemangioma is a primary tumour of the microvasculature characterised by active angiogenesis and endothelial cell (EC)  proliferation followed by slow regression or involution whereby the newly formed blood vessels are gradually replaced by fibrofatty tissue. These developmental changes have been arbitrarily divided into the proliferative, involuting and involuted phases. The cellular and molecular events that initiate and regulate the proliferation and spontaneous involution of haemangioma remain poorly understood. This study examined the expression of a number of genes known to be associated with angiogenesis. These include members of the signal transducers and activators of transcription (STAT) protein family of transcription factors, STAT-3 and STAT-1, and the endothelial receptor tyrosine kinases, VEGFR-1 and VEGFR-2. While STAT-3, STAT-1 and VEGFR-1 expression was detected in all phases of haemangioma, VEGFR-2 expression was found to be abundant only during the proliferative phase and decreased with ongoing involution. In this study the cellular structures that form capillary-like outgrowths in an in vitro haemangioma explant model were characterised as haemangioma-derived mesenchymal stem cells (HaemDMSCs) while the cells obtained directly from dissociated proliferative haemangioma tissue were defined as haemangioma-derived endothelial progenitor cells (HaemDEPCs). This investigation showed that although the vascular endothelial growth factor (VEGF), a key growth factor for ECs, was able to maintain HaemDEPCs morphology and immunophenotype for a limited period, these cells eventually differentiated into HaemDMSCs, which subsequently differentiated into adipocytes. Furthermore, while VEGF induced significant capillary-like sprouting from tissue explants, both capillary-like sprouting and HaemDMSCs proliferation was inhibited by the addition of AG490, a Janus kinase (JAK) inhibitor which has also been shown to inhibit the STAT protein pathway. These findings indicate that the development and differentiation of a progenitor cell and a stem cell population underlies the aethiopathogenesis of haemangioma and that VEGF and STAT signalling is involved in the programmed life-cycle of haemangioma. The in vitro explant model for haemangioma offers an opportunity to study and identify novel treatment options for haemangioma. Interferon-alpha (IFN ) has been used to treat steroid-resistant haemangioma but is associated with serious side-affects. The tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has been shown to specifically induce apoptosis of cancer cells while sparing normal cells. As IFN has previously been shown to sensitise cells to TRAIL-induced apoptosis, this study examined the efficacy of low dose IFN in combination with TRAIL in the in vitro explant model and also in the purified HaemDMSCs. Results showed that combining IFN with TRAIL led to synergistic inhibition of capillary-like outgrowth. These results indicate that IFN in combination with TRAIL serves as a potential treatment option for haemangioma. In contrast, HaemDMSCs were protected from TRAIL-induced killing. These cells were found to express high levels of the decoy receptors, osteoprotegerin (OPG) and decoy receptor 2 (DcR2). Increased OPG expression was also detected in the extracellular matrix and in the conditioned medium of HaemDMSCs. From these findings, we postulate that the increased level of extracellular OPG by HaemDMSCs is a stress response induced by their in vitro expansion and that secreted OPG functions as a protective shield preventing TRAIL action. The empirical and unsatisfactory nature of the current therapies for haemangioma underscores the importance of a scientific approach to this common tumour. A better understanding of the molecular mechanisms that govern haemangioma is of both clinical and biological interest as it may provide vital information with therapeutic potential for haemangioma and also for other angiogenesis-dependent conditions.</p>

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