In-silico identification and prioritization of therapeutic targets of asthma.

Asthma is a "common chronic disorder that affects the lungs causing variable and recurring symptoms like repeated episodes of wheezing, breathlessness, chest tightness and underlying inflammation. The interaction of these features of asthma determines the clinical manifestations and severity of asthma and the response to treatment" [cited from: National Heart, Lung, and Blood Institute. Expert Panel 3 Report. Guidelines for the Diagnosis and Management of Asthma 2007 (EPR-3). Available at: https://www.ncbi.nlm.nih.gov/books/NBK7232/ (accessed on January 3, 2023)]. As per the WHO, 262 million people were affected by asthma in 2019 that leads to 455,000 deaths ( https://www.who.int/news-room/fact-sheets/detail/asthma ). In this current study, our aim was to evaluate thousands of scientific documents and asthma associated omics datasets to identify the most crucial therapeutic target for experimental validation. We leveraged the proprietary tool Ontosight® Discover to annotate asthma associated genes and proteins. Additionally, we also collected and evaluated asthma related patient datasets through bioinformatics and machine learning based approaches to identify most suitable targets. Identified targets were further evaluated based on the various biological parameters to scrutinize their candidature for the ideal therapeutic target. We identified 7237 molecular targets from published scientific documents, 2932 targets from genomic structured databases and 7690 dysregulated genes from the transcriptomics and 560 targets from genomics mutational analysis. In total, 18,419 targets from all the desperate sources were analyzed and evaluated though our approach to identify most promising targets in asthma. Our study revealed IL-13 as one of the most important targets for asthma with approved drugs on the market currently. TNF, VEGFA and IL-18 were the other top targets identified to be explored for therapeutic benefit in asthma but need further clinical testing. HMOX1, ITGAM, DDX58, SFTPD and ADAM17 were the top novel targets identified for asthma which needs to be validated experimentally.

Phase I, first-in-human trial of Bruton's tyrosine kinase inhibitor M7583 in patients with B-cell malignancies.

M7583 is a potent, highly selective, covalent BTK inhibitor in development. In this phase I, first-in-human, open label, multicenter dose-escalation trial, M7583 was given at 80 mg (three days)/160 mg (full 28-day cycle), then 300 mg/day, 600 mg/day, 900 mg/day, and 300 mg twice daily to 18 patients (median age 63 years) with refractory/resistant, stage III/IV B-cell malignancies who failed prior therapy (NCT02825836). No dose-limiting toxicities were reported. Treatment-emergent adverse events (AEs) occurred in 89% of patients, treatment-related AEs in 78%, and treatment-related grade ≥3 AEs in 17%. Common AEs were diarrhea (33%), fatigue (22%), and vomiting (17%). M7583 was rapidly absorbed and exposure was dose-proportional. BTK occupancy was >95% in the 300 mg twice daily and 900 mg/day cohorts. Objective response rate was 50% and disease control rate 78%, supporting a favorable benefit:risk profile. Fasted doses up to 900 mg once daily and 300 mg twice daily were well tolerated and may be tested in future clinical studies.

Tepotinib plus gefitinib in patients with EGFR-mutant non-small-cell lung cancer with MET overexpression or MET amplification and acquired resistance to previous EGFR inhibitor (INSIGHT study): an open-label, phase 1b/2, multicentre, randomised trial.

BACKGROUND: We evaluated the efficacy and safety of tepotinib, a potent and highly selective oral MET inhibitor, plus gefitinib in patients with epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancer (NSCLC) with MET overexpression (immunohistochemistry [IHC]2+ or IHC3+) or MET amplification having acquired resistance to EGFR inhibition. METHODS: In this open-label, phase 1b/2, multicentre, randomised trial (the INSIGHT study), we enrolled adult patients (≥18 years) with advanced or metastatic NSCLC, and Eastern Cooperative Oncology Group performance status of 0 or 1, from academic medical centres and community clinics in six Asian countries. In phase 1b, patients received oral tepotinib 300 mg or 500 mg plus gefitinib 250 mg once daily. In phase 2, patients with EGFR-mutant, T790M-negative NSCLC MET overexpression or MET amplification were randomly assigned (initially in a 1:1 ratio and then 2:1 following a protocol amendment) to tepotinib plus gefitinib at the recommended phase 2 dose or to standard platinum doublet chemotherapy. Randomisation was done centrally via an interactive voice-response system. The primary endpoint was investigator-assessed progression-free survival (PFS). Secondary endpoints included overall survival (OS) and safety. Subgroup analyses were preplanned in patients with high MET overexpression (IHC3+) or MET amplification (mean gene copy number ≥5 or MET to centromere of chromosome 7 ratio ≥2). Efficacy and patient characteristics were assessed on an intention-to-treat basis and safety was assessed for all patients who received at least one dose of study medication. Low recruitment led to early termination of phase 2, so all analyses are considered to be exploratory. This study is registered with ClinicalTrials.gov, NCT01982955, and the European Union Drug Regulating Authorities Clinical Trials Database, Eudra-CT 2016-001604-28. FINDINGS: From Dec 23, 2013, to May 25, 2017, 18 patients were enrolled in phase 1b (n=6 in the 300 mg tepotinib group; n=12 in the 500 mg tepotinib group) and 55 patients in phase 2 (n=31 in the tepotinib plus gefitinib group; n=24 in the chemotherapy group). No dose-limiting toxicities were observed in phase 1b, so tepotinib 500 mg was used as the recommended phase 2 dose. In phase 2, survival outcomes were similar between groups: median PFS was 4·9 months in the tepotinib plus gefitinib group (90% CI 3·9-6·9) versus 4·4 months in the chemotherapy group (90% CI 4·2-6·8; hazard ratio [HR] 0·67, 90% CI 0·35-1·28). Median OS was 17·3 months in the tepotinib plus gefitinib group (12·1-37·3) versus 18·7 months in the chemotherapy group (15·9-20·7; HR 0·69, 0·34-1·41). PFS and OS were longer with tepotinib plus gefitinib than with chemotherapy in patients with high (IHC3+) MET overexpression (n=34; median PFS 8·3 months [4·1-16·6] vs 4·4 months [4·1-6·8]; HR 0·35, 0·17-0·74; median OS 37·3 months [90% CI 24·2-37·3] vs 17·9 months [12·0-20·7]; HR 0·33, 0·14-0·76) or MET amplification (n=19; median PFS 16·6 months [8·3-not estimable] vs 4·2 months [1·4-7·0]; HR 0·13, 0·04-0·43; median OS 37·3 months [90% CI not estimable] vs 13·1 months [3·25-not estimable]; HR 0·08, 0·01-0·51). The most frequent treatment-related grade 3 or worse adverse events were increased amylase (5 [16%] of 31 patients) and lipase (4 [13%]) concentrations in the tepotinib plus gefitinib group and anaemia (7 [30%] of 23 patients) and decreased neutrophil count (3 [13%]) in the chemotherapy group. INTERPRETATION: Despite early study termination, in a preplanned subgroup analysis, our findings suggest improved anti activity for tepotinib plus gefitinib compared with standard chemotherapy in patients with EGFR-mutant NSCLC and MET amplification, warranting further exploration. FUNDING: Merck KGaA.

Tepotinib in Non-Small-Cell Lung Cancer with MET Exon 14 Skipping Mutations.

BACKGROUND: A splice-site mutation that results in a loss of transcription of exon 14 in the oncogenic driver MET occurs in 3 to 4% of patients with non-small-cell lung cancer (NSCLC). We evaluated the efficacy and safety of tepotinib, a highly selective MET inhibitor, in this patient population. METHODS: In this open-label, phase 2 study, we administered tepotinib (at a dose of 500 mg) once daily in patients with advanced or metastatic NSCLC with a confirmed MET exon 14 skipping mutation. The primary end point was the objective response by independent review among patients who had undergone at least 9 months of follow-up. The response was also analyzed according to whether the presence of a MET exon 14 skipping mutation was detected on liquid biopsy or tissue biopsy. RESULTS: As of January 1, 2020, a total of 152 patients had received tepotinib, and 99 patients had been followed for at least 9 months. The response rate by independent review was 46% (95% confidence interval [CI], 36 to 57), with a median duration of response of 11.1 months (95% CI, 7.2 to could not be estimated) in the combined-biopsy group. The response rate was 48% (95% CI, 36 to 61) among 66 patients in the liquid-biopsy group and 50% (95% CI, 37 to 63) among 60 patients in the tissue-biopsy group; 27 patients had positive results according to both methods. The investigator-assessed response rate was 56% (95% CI, 45 to 66) and was similar regardless of the previous therapy received for advanced or metastatic disease. Adverse events of grade 3 or higher that were considered by investigators to be related to tepotinib therapy were reported in 28% of the patients, including peripheral edema in 7%. Adverse events led to permanent discontinuation of tepotinib in 11% of the patients. A molecular response, as measured in circulating free DNA, was observed in 67% of the patients with matched liquid-biopsy samples at baseline and during treatment. CONCLUSIONS: Among patients with advanced NSCLC with a confirmed MET exon 14 skipping mutation, the use of tepotinib was associated with a partial response in approximately half the patients. Peripheral edema was the main toxic effect of grade 3 or higher. (Funded by Merck [Darmstadt, Germany]; VISION ClinicalTrials.gov number, NCT02864992.).

Bispecific T-Cell Engager (BiTE) Antibody Construct Blinatumomab for the Treatment of Patients With Relapsed/Refractory Non-Hodgkin Lymphoma: Final Results From a Phase I Study.

PURPOSE: Blinatumomab is a CD19/CD3 BiTE (bispecific T-cell engager) antibody construct for the treatment of Philadelphia chromosome-negative acute B-lymphoblastic leukemia. We evaluated blinatumomab in relapsed/refractory B-cell non-Hodgkin lymphoma (NHL). PATIENTS AND METHODS: This 3 + 3 design, phase I dose-escalation study determined adverse events and the maximum tolerated dose (MTD) of continuous intravenous infusion blinatumomab in patients with relapsed/refractory NHL. Blinatumomab was administered over 4 or 8 weeks at seven different dose levels (0.5 to 90 µg/m(2)/day). End points were incidence of adverse events, pharmacokinetics, pharmacodynamics, and overall response rate. RESULTS: Between 2004 and 2011, 76 heavily pretreated patients with relapsed/refractory NHL, who included 14 with diffuse large B-cell lymphoma, were enrolled; 42 received treatment in the formal dose-escalation phase. Neurologic events were dose limiting, and 60 µg/m(2)/day was established as the MTD. Thirty-four additional patients were recruited to evaluate antilymphoma activity and strategies for mitigating neurologic events at a prespecified MTD. Stepwise dosing (5 to 60 µg/m(2)/day) plus pentosan polysulfate SP54 (n = 3) resulted in no treatment discontinuations; single-step (n = 5) and double-step (n = 24) dosing entailed two and seven treatment discontinuations due to neurologic events, respectively. Grade 3 neurologic events occurred in 22% of patients (no grade 4/5). Among patients treated at 60 µg/m(2)/day (target dose; n = 35), the overall response rate was 69% across NHL subtypes and 55% for diffuse large B-cell lymphoma (n = 11); median response duration was 404 days (95% CI, 207 to 1,129 days). CONCLUSION: In this phase I study of relapsed/refractory NHL, continuous infusion with CD19-targeted immunotherapy blinatumomab at various doses and schedules was feasible, with an MTD of 60 µg/m(2)/day. Single-agent blinatumomab showed antilymphoma activity.

The side population phenomenon enriches for designated adrenocortical progenitor cells in mice.

Somatic adrenal stem cells are believed to reside in the periphery of the adrenal cortex throughout life for organ maintenance. Herein, we used the side population (SP) phenomenon to enrich for these progenitors, which made up to 0.01-0.64% of the total cell count. Microarray analysis revealed an expression profile of SP cells, which clearly differed from that of non-SP cells. However, a promising adrenal specific stem cell marker could not be identified. In vitro, SP cells could be maintained in long-term culture, whereas non-SP cells did not proliferate. After 4 weeks of culturing, immunohistochemistry revealed the expression of steroidogenic enzymes such as 3ß-HSD, StAR, and P450SCC, suggesting spontaneous differentiation. Interestingly, the quantity of SP cells was significantly diminished in Pbx1 haploinsufficient mice, suggesting a stem cell deficit. By contrast, the subcapsular zone of ACTH-deficient Tpit(-/-) mice was significantly wider compared with wild-type adrenals (Tpit(-/-) 259±10.7 vs Tpit(+/-) 100±12.3%; P<0.01). Accordingly, the number of SP cells in these mice was significantly higher (Tpit(-/-) 0.45±0.16 vs Tpit(+/-) 0.13±0.04%; P<0.004). ACTH treatment of these animals reverted the subcapsular zone width and the SP fraction back to normal (130±10.2%; P=0.33 and 0.09%), providing indirect evidence for a stem cell 'arrest' in Tpit(-/-) mice and the role of ACTH in adrenocortical stem cell modulation and differentiation.

Rap1a deficiency modifies cytokine responses and MAPK-signaling in vitro and impairs the in vivo inflammatory response.

Rap1, which is closely related to ras, plays a key role in T-cell receptor (TCR)-signaling. TCR-stimulation without costimulation leads to constitutively activated rap1, which may mediate T-cell anergy via inhibition of ras-dependent induction of extracellular signal-regulated kinases (ERK). This activation is mediated by a second protein kinase b-Raf. Rap1-GTP is thought to activate ERK in a ras-independent manner by binding b-raf. Generally, T cells do not express b-raf while they express the adaptor protein raf-1, which is usually sequestered by rap1 leading to inhibition of ras-mediated ERK activation. In this study, we demonstrate that in rap1-deficient T cells, signaling by the ERK and p38 kinases is increased following activation by different stimuli leading to increased intracellular accumulation and secretion of cytokines. In addition, in a hypersensitivity model rap1-deficient mice demonstrated reduced contact dermatitis compared to wildtype mice, demonstrating the impact of rap1-deficiency on the inflammatory response in vivo.

Clinical response to Auron Misheil Therapy in a man with advanced multifocal hepatocellular carcinoma: A case report.

INTRODUCTION: Auron Misheil Therapy was developed based on similarities between carcinogenesis and inflammation. Auron Misheil Therapy is a combination of natural and synthetic compounds, including anti-inflammatory drugs and insulin, expected to exhibit synergistic effects. CASE PRESENTATION: Here, we report the case of a 78-year-old Caucasian male patient who presented with multifocal hepatocellular carcinoma and chronic hepatitis C virus infection. Over a four-year period our patient was treated with radiofrequency ablation and transarterial chemoembolization. After these treatments there was tumor progression, with new hyperperfused lesions without evidence of extrahepatic tumor involvement. Our patient refused sorafenib therapy. Therefore, he received twice daily intramuscular injections of Auron Misheil Therapy on an outpatient basis for two months. Partial remission of the hepatic lesions was observed eight weeks after the start of treatment, and confirmed four weeks later. Unfortunately, at that time our patient refused therapy due to dizziness. During follow-up two target lesions remained stable, but one lesion increased in size. At the latest follow-up, one year later, there was still tumor control. CONCLUSION: While the mechanisms underlying the antitumor effects of Auron Misheil Therapy are not fully understood, stable disease and remissions have been observed in different types of tumors, including hepatocellular carcinoma.

Effects of Auron-Misheil-Therapy in human in vitro skin models.

Auron-Misheil-Therapy (AMT) is currently under development as an anticancer treatment. The aim of the present study was the identification of possible effects and properties of AMT with regard to human skin. The study consisted of three experimental phases. Phase 1 assessed the effects of AMT on the viability of 2-D evaluated and accredited cell cultures of three cell types of human skin, namely: keratinocytes, melanocytes and fibroblasts. Three separate assays were used in this phase. Phase 2 was designed to clarify the effects of AMT on cell viability to investigate the mode of action of AMT. Two possible modes of action were investigated: proliferation inhibition and apoptosis. There was one assay to assess proliferation, and two independent assays to assess apoptosis. The third phase assessed the effects of AMT on two different types of 3-D skin models, an ex vivo model and a de novo reconstituted model. In the phase 1 tests, reduction of cell viability by AMT was demonstrated in all three cell types. In phase 2, the cell proliferation assay showed decreased proliferation rates in the presence of AMT in three out of four cell populations. In phase 3, histochemical investigations with 3-D models indicated that AMT induces desquamation, most likely as the result of apoptosis of epidermal cells. The experiments generally showed that AMT does not harm human skin at concentrations up to 3%.

Novel integrin-dependent platelet malfunction in siblings with leukocyte adhesion deficiency-III (LAD-III) caused by a point mutation in FERMT3.

Leukocyte adhesion deficiency-III (LAD-III) also called leukocyte adhesion deficiency-1/variant (LAD1v) is a rare congenital disease caused by defective integrin activation of leukocytes and platelets. Patients with LAD-III present with non-purulent infections and increased bleeding symptoms. We report on a novel integrin-dependent platelet dysfunction in two brothers with LAD-III syndrome caused by a homozygous mutation 1717C>T in the FERMT3 gene leading to a premature stop codon R573X in the focal adhesion protein kindlin-3. Stimulation of patients platelets with all used agonists resulted in a severely decreased binding of soluble fibrinogen indicating a defect in inside-out activation of the integrin alpha(IIb) beta(3) (GPIIb/IIIa). Patients platelets did not respond to the alpha(2)beta(1)-integrin agonist aggretin-A at all. Our data on granula secretion indicate for the first time that the thrombin receptor PAR-4 but not PAR-1 may be important in integrin-triggered granule secretion in response to thrombin. In contrast, collagen mediated platelet granule secretion was not affected in LAD-III-patients. Thus, integrin-signalling may be not essential in collagen-induced granule secretion. The patients' peripheral blood mononuclear cells showed a severe loss of adhesion capacity to VCAM-1 and to endothelial cells compared to cells from healthy donors. Rap-1 activation after PMA stimulation could be observed in controls but not in patients cells. After haematogenesis stem cell transplantation (HSCT) the brothers showed no symptoms of bleeding or immunodeficiency and the integrin-dependent platelet and leukocyte functions normalised.

Retrotransposition and mutation events yield Rap1 GTPases with differential signalling capacity.

BACKGROUND: Retrotransposition of mRNA transcripts gives occasionally rise to functional retrogenes. Through acquiring tempero-spatial expression patterns distinct from their parental genes and/or functional mutations in their coding sequences, such retrogenes may in principle reshape signalling networks. RESULTS: Here we present evidence for such a scenario, involving retrogenes of Rap1 belonging to the Ras family of small GTPases. We identified two murine and one human-specific retrogene of Rap1A and Rap1B, which encode proteins that differ by only a few amino acids from their parental Rap1 proteins. Markedly, human hRap1B-retro and mouse mRap1A-retro1 acquired mutations in the 12th and 59th amino acids, respectively, corresponding to residues mutated in constitutively active oncogenic Ras proteins. Statistical and structural analyses support a functional evolution scenario, where Rap1 isoforms of retrogenic origin are functionally distinct from their parental proteins. Indeed, all retrogene-encoded GTPases have an increased GTP/GDP binding ratio in vivo, indicating that their conformations resemble that of active GTP-bound Rap1. We furthermore demonstrate that these three Rap1 isoforms exhibit distinct affinities for the Ras-binding domain of RalGDS. Finally, when tested for their capacity to induce key cellular processes like integrin-mediated cell adhesion or cell spreading, marked differences are seen. CONCLUSIONS: Together, these data lend strong support for an evolution scenario, where retrotransposition and subsequent mutation events generated species-specific Rap1 isoforms with differential signaling potential. Expression of the constitutively active human Rap1B-retro in cells like those derived from Ramos Burkitt's lymphoma and bone marrow from a patient with myelodysplastic syndrome (MDS) warrants further investigation into its role in disease development.

Anti-tumor effects of AMT in the renal cell carcinoma model.

Auron-Misheil-Therapy (AMT) is a defined but unique combination of approved pharmaceuticals. It consists of insulin, chlorpheniramine and an aqueous camomile extract, and it has been successfully applied clinically in late-stage cancer patients. The purpose of this study was to elucidate the anti-tumor efficacy of AMT in a validated murine renal cell carcinoma animal model (RENCA). There were two independent studies; each animal group consisted of 16 mice. During a 6-week pretreatment period, vehicle (group A) and AMT (1.6 mg/kg/d) (group B) were administered once daily in a 5 days/week schedule either intramuscularly or subcutaneously. Tumor challenge at day 0 was followed by a 3-week treatment period (either vehicle or AMT once daily intramuscularly for 21 days consecutively). In study 2 the AMT dosage was increased up to 4-fold by doubling individual doses and switching to a twice daily schedule. The injections were all intramuscular. With the exception of group D, a six-week pretreatment period preceded the tumor challenge at day 0. Tumor challenge was followed by a 3-week treatment period (vehicle, AMT at either 3.2 mg/kg/d) (group A) or 6.4 mg/kg/d (group B), or AMT0, an AMT preparation which does not stimulate IL-6 secretion (6.4 mg/kg/d, group C) continuously for 21 days. AMT administration for group D (6.4 mg/kg/d) was limited to the treatment period from day 1 to 21. All mice were sacrificed 21 days after tumour transplantation. AMT administration was safe and well tolerated, and significantly reduced primary tumor volume in pretreated animals. The effective route of application was intramuscular, with dose escalation resulting in an improved anti-tumor effect. This is the first demonstration of a significant anti-tumorigenic effect of AMT in a validated tumor model.

A pilot study of Auron Misheil Therapy in patients with advanced cervical cancer: tumor response and its correlation with clinical benefit response, and preliminary quality of life data.

This pilot study of Auron Misheil Therapy (AMT) in women with advanced cervical cancer was an open-label, single arm study to collect initial safety, efficacy, and quality of life data. Fifteen women with stage IIIb or IVa cervical cancer were given twice daily intramuscular injections of AMT (insulin, chlorpheniramine and camomile extract) for 3 months. Objective tumor response was evaluated using CT scans and analyzing the data according to the WHO RECIST criteria. Clinical Benefit Response (CBR) was assessed using a composite score comprising Karnovsky performance status, pain intensity and body weight. Safety and tolerability parameters were monitored. Quality of life was evaluated using the European Organization for Research and Treatment of Cancer Core Quality of Life Questionnaire (EORTC C-30). Eight out of 15 patients were rated as clinical responders (CBR) at 12 weeks. One patient had a partial response and 11 stable disease (WHO RECIST criteria). AMT was well tolerated. An initial analysis showed improvement in quality of life (EORTC C-30). Promising response rates, early indications of improved quality of life, and no significant safety issues mean that the second, randomized phase of the trial can be initiated with a longer treatment duration. Patients with advanced cervical cancer showed positive clinical responses to Auron Misheil Therapy. The treatment was well tolerated, with indications of improved quality of life.

AMT: preclinical pharmacology studies.

Auron-Misheil-Therapy (AMT) consisting of aqueous camomile extract supplemented with calcium, vitamins, the antihistamine chlorpheniramine and human insulin is under development as anti-cancer treatment. AMT was preclinically investigated in tumour cell lines and tumour xenografts to guide clinical phase I/II studies. AMT was tested against 56 human tumour cell lines, in a clonogenic assay in 98 patient-derived xenografts and in in vivo studies. AMT showed in vitro cytotoxic activity with highest susceptibility in cervical cancer, glioblastoma and colon cancers. In the clonogenic assay, anti- cancer activity of AMT was most active in cervical and uterine tumours, in colon cancer, glioblastoma, leukaemia, melanoma and pancreatic cancer. In vivo, AMT showed slight activity in tumour xenograft models of colon and mammary cancer. It also showed immune stimulatory effects by induction of IL-6- and TNF-alpha secretion in human PBMCs. The immune stimulatory potential of AMT, together with slight anti-tumour efficacy observed in the present study, indicates a role of AMT in tumour therapy.

The Spt-Ada-Gcn5-acetyltransferase complex interaction motif of E2a is essential for a subset of transcriptional and oncogenic properties of E2a-Pbx1.

The oncogene E2a-Pbx1 is formed by the t(1;19) translocation, which joins the N-terminal transactivation domain of E2a with the C-terminal homeodomain of PBX1. The goal of this work was to elucidate the mechanisms by which E2a-Pbx1 can lead to deregulated target gene expression. For reporter constructs it was shown that E2a-Pbx1 can activate transcription through homodimer elements (TGATTGAT) or through heterodimer elements with Hox proteins (e.g. TGATTAAT). We show a novel mechanism by which E2a-Pbx1 activates transcription of EF-9 using a promoter in intron 1 of the EF-9 gene, resulting in an aminoterminal truncated transcript. Our results indicate that the LDFS motif of E2a is essential for the transactivation of EF-9, but dispensable for transactivation of fibroblast growth factor 15. The E2a LDFS motif was also essential for proliferation of NIH3T3 fibroblasts but was dispensable for the E2a-Pbx1-induced differentiation arrest of myeloid progenitors.

PBX1 is dispensable for neural commitment of RA-treated murine ES cells.

Experimentation with PBX1 knockout mice has shown that PBX1 is necessary for early embryogenesis. Despite broad insight into PBX1 function, little is known about the underlying target gene regulation. Utilizing the Cre-loxP system, we targeted a functionally important part of the homeodomain of PBX1 through homozygous deletion of exon-6 and flanking intronic regions leading to exon 7 skipping in embryonic stem (ES) cells. We induced in vitro differentiation of wild-type and PBX1 mutant ES cells by aggregation and retinoic acid (RA) treatment and compared their profiles of gene expression at the ninth day post-reattachment to adhesive media. Our results indicate that PBX1 interactions with HOX proteins and DNA are dispensable for RA-induced ability of ES to express neural genes and point to a possible involvement of PBX1 in the regulation of imprinted genes.

Shear stress-mediated adhesion of acute myeloid leukemia and KG-1 cells to endothelial cells involves functional P-selectin.

Acute myeloid leukemia (AML) shows malignant behavior through the ability of immature cells to circulate in blood and to invade peripheral tissues. Whereas binding of human AML cells to endothelial cells (ECs) through E-selectin has been shown to occur using classical adhesion assays, little is known about the ability of endothelial P-selectin to support this process. We therefore characterized the ability of AML blasts and KG-1 cells to bind to endothelial selectin type ligands. Flow cytometry revealed that, in addition to various integrin adhesion receptors, AML cells regularly express the P-selectin glycoprotein ligand (PSGL)-1, a ligand for P- and E-selectin on ECs. In parallel flow chambers, AML cells both rolled and adhered to TNF-alpha pretreated human umbilical vein endothelial cells (HUVECs). Pretreatment of HUVECs with anti-P- or anti-E-selectin function blocking antibodies significantly reduced both, rolling and subsequent arrest of primary AML cells. Intravital microscopy of i.v. injected fluorescence-labeled KG-1 cells into P-selectin deficient or wild type mice confirmed a significant role of endothelial P-selectin in the binding of human primary AML cells to ECs also in vivo. Thus, the currently available data suggest a role of P- and E-selectin in coordinated circulation of AML cells. Thus, P- or E-selectin mediated adhesion of AML cells may provide a target for the development anti-leukemic therapies.

Role of the small GTPase Rap1 for integrin activity regulation in endothelial cells and angiogenesis.

Ras-associated protein 1 (Rap1), a small GTPase, attracted attention because of its involvement in several aspects of cell adhesion, including integrin- and cadherin-mediated adhesion. Yet, the role of Rap1 genes and of Rap1 effectors for angiogenesis has not been investigated. Human umbilical vein endothelial cells (HUVECs) express Rap1a and Rap1b mRNA. To determine the contribution of Rap1 activity for angiogenesis, we overexpressed Rap1GAP1, a GTPase-activating protein that inhibits Rap1 activity. Overexpression of Rap1GAP1 significantly blocked angiogenic sprouting and tube-forming activity of HUVECs as well as migration and integrin-dependent adhesion. Silencing of Rap1a, Rap1b, or both significantly blocked HUVECs sprouting under basal and basic fibroblast growth factor-stimulated conditions and reduced HUVEC migration and integrin-dependent adhesion. We found that Rap1a and Rap1b are essential for the conformational activation of beta(1)-integrins in endothelial cells. Furthermore, silencing of Rap1a and Rap1b prevented phosphorylation of tyrosine 397 in focal adhesion kinase (FAK) and vascular endothelial growth factor-induced Akt1-activation. Rap1a(-/-)-deficient and Rap1a(+/-) heterozygote mice displayed reduced neovascularization after hind limb ischemia compared with wild-type mice. Silencing of RAPL significantly blocked the Rap1-induced sprouting of HUVECs, suggesting that the angiogenic activity of Rap1 is partly mediated by RAPL. Our data demonstrate a critical role of Rap1 in the regulation of beta(1)-integrin affinity, adhesion, and migration in endothelial cells and in postnatal neovascularization.

Pre-B-cell transcription factor 1 and steroidogenic factor 1 synergistically regulate adrenocortical growth and steroidogenesis.

A variety of transcription factors including Wilms tumor gene (Wt-1), steroidogenic factor 1 (Sf-1), dosage-sensitive sex reversal, adrenal hypoplasia congenita on the X-chromosome, Gene 1 (Dax-1), and pre-B-cell transcription factor 1 (Pbx1) have been defined as necessary for regular adrenocortical development. However, the role of Pbx1 for adrenal growth and function in the adult organism together with the molecular relationship between Pbx1 and these other transcription factors have not been characterized. We demonstrate that Pbx haploinsufficiency (Pbx1(+/-)) in mice is accompanied by a significant lower adrenal weight in adult animals compared with wild-type controls. Accordingly, baseline proliferating cell nuclear antigen levels are lower in Pbx1(+/-) mice, and unilateral adrenalectomy results in impaired contralateral compensatory adrenal growth, indicating a lower proliferative potential in the context of Pbx1 haploinsufficiency. In accordance with the key role of IGFs in adrenocortical proliferation and development, real-time RT-PCR demonstrates significant lower expression levels of the IGF-I receptor, and up-regulation of IGF binding protein-2. Functionally, Pbx1(+/-) mice display a blunted corticosterone response after ACTH stimulation coincident with lower adrenal expression of the ACTH receptor (melanocortin 2 receptor, Mc2-r). Mechanistically, in vitro studies reveal that Pbx1 and Sf-1 synergistically stimulates Mc2-r promoter activity. Moreover, Sf-1 directly activates the Pbx1 promoter activity in vitro and in vivo. Taken together, these studies provide evidence for a role of Pbx1 in the maintenance of a functional adrenal cortex mediated by synergistic actions of Pbx1 and Sf-1 in the transcriptional regulation of the critical effector of adrenocortical differentiation, the ACTH receptor.

Rap1A-deficient T and B cells show impaired integrin-mediated cell adhesion.

Studies in tissue culture cells have demonstrated a role for the Ras-like GTPase Rap1 in the regulation of integrin-mediated cell-matrix and cadherin-mediated cell-cell contacts. To analyze the function of Rap1 in vivo, we have disrupted the Rap1A gene by homologous recombination. Mice homozygous for the deletion allele are viable and fertile. However, primary hematopoietic cells isolated from spleen or thymus have a diminished adhesive capacity on ICAM and fibronectin substrates. In addition, polarization of T cells from Rap1-/- cells after CD3 stimulation was impaired compared to that of wild-type cells. Despite this, these defects did not result in hematopoietic or cell homing abnormalities. Although it is possible that the relatively mild phenotype is a consequence of functional complementation by the Rap1B gene, our genetic studies confirm a role for Rap1A in the regulation of integrins.