Cabergoline treatment promotes myocardial recovery in peripartum cardiomyopathy.

AIMS: Peripartum cardiomyopathy (PPCM) is a rare heart disease, occurring in previously heart-healthy women during the last month of pregnancy or the first months after delivery due to left ventricular (LV) systolic dysfunction. A common pathomechanistic pathway of PPCM includes increased oxidative stress and the subsequent generation of a cleaved prolactin fragment (16 kDa PRL), which promotes the onset of heart failure (HF) in a microRNA (miR)-146a-dependent manner. Inhibition of prolactin secretion with the dopamine D2 receptor (D2R) agonist bromocriptine combined with standard HF therapy supports cardiac recovery. This study examined whether treatment with the more selective D2R agonist cabergoline prevents HF development in an experimental PPCM mouse model and might be used as an alternative treatment regime for PPCM. METHODS AND RESULTS: Postpartum (PP) female PPCM-prone mice with a cardiomyocyte restricted STAT3-deficiency (αMHC-Cretg/+ ; Stat3fl/fl ; CKO) were treated over two consecutive nursing periods with cabergoline (CKO Cab, 0.5 mg/kg/day) and were compared with bromocriptine treated CKO (CKO Br) and postpartum-matched WT and CKO mice. Cabergoline treatment in CKO PP mice preserved cardiac function [fractional shortening (FS): CKO Cab: 34.5 ± 9.4% vs. CKO: 22.1 ± 9%, P < 0.05] and prevented the development of cardiac hypertrophy, fibrosis, and inflammation as effective as bromocriptine therapy (FS: CKO Br: 33.4 ± 5.6%). The myocardial up-regulation of the PPCM biomarkers plasminogen inhibitor activator 1 (PAI-1) and miR-146a were prevented by both cabergoline and bromocriptine therapy. A small cohort of three PPCM patients from the German PPCM Registry was treated with cabergoline (1 mg per week for 2 weeks, followed by 0.5 mg per week for another 6 weeks) due to a temporary unavailability of bromocriptine. All PPCM patients initially presented with a severely reduced LV ejection fraction (LVEF: 26 ± 2%). However, at 6 months of follow-up, LV function (LVEF: 56 ± 2%) fully recovered in all three PPCM patients, and no adverse events were detected. CONCLUSIONS: In the experimental PPCM mouse model, the selective D2R agonist cabergoline prevents the onset of postpartum HF similar to bromocriptine. In PPCM patients, cabergoline treatment was safe and effective as all patients fully recovered. Cabergoline might serve as a promising alternative to bromocriptine. However, these findings are based on experimental data and a small case series and thus have to be interpreted with caution and should be validated in a larger clinical trial.

Chemotherapy-Free Targeted Anti-BCR-ABL+ Acute Lymphoblastic Leukemia Therapy May Benefit the Heart.

Targeted therapies are currently considered the best cost-benefit anti-cancer treatment. In hematological malignancies, however, relapse rates and non-hematopoietic side effects including cardiotoxicity remain high. Here, we describe significant heart damage due to advanced acute lymphoblastic leukemia (ALL) with t(9;22) encoding the bcr-abl oncogene (BCR-ABL+ ALL) in murine xenotransplantation models. Echocardiography reveals severe cardiac dysfunction with impaired left ventricular function and reduced heart and cardiomyocyte dimensions associated with increased apoptosis. This cardiac damage is fully reversible, but cardiac recovery depends on the therapy used to induce ALL remission. Chemotherapy-free combination therapy with dasatinib (DAS), venetoclax (VEN) (targeting the BCR-ABL oncoprotein and mitochondrial B-cell CLL/Lymphoma 2 (BCL2), respectively), and dexamethasone (DEX) can fully revert cardiac defects, whereas the depletion of otherwise identical ALL in a genetic model using herpes simplex virus type 1 thymidine kinase (HSV-TK) cannot. Mechanistically, dexamethasone induces a pro-apoptotic BCL2-interacting mediator of cell death (BIM) expression and apoptosis in ALL cells but enhances pro-survival B-cell lymphoma extra-large (BCLXL) expression in cardiomyocytes and clinical recovery with the reversion of cardiac atrophy. These data demonstrate that therapies designed to optimize apoptosis induction in ALL may circumvent cardiac on-target side effects and may even activate cardiac recovery. In the future, combining the careful clinical monitoring of cardiotoxicity in leukemic patients with the further characterization of organ-specific side effects and signaling pathways activated by malignancy and/or anti-tumor therapies seems reasonable.

A unique role of p53 haploinsufficiency or loss in the development of acute myeloid leukemia with FLT3-ITD mutation.

With an incidence of ~50%, the absence or reduced protein level of p53 is much more common than TP53 mutations in acute myeloid leukemia (AML). AML with FLT3-ITD (internal tandem duplication) mutations has an unfavorable prognosis and is highly associated with wt-p53 dysfunction. While TP53 mutation in the presence of FLT3-ITD does not induce AML in mice, it is not clear whether p53 haploinsufficiency or loss cooperates with FLT3-ITD in the induction of AML. Here, we generated FLT3-ITD knock-in; p53 knockout (heterozygous and homozygous) double-transgenic mice and found that both alterations strongly cooperated in the induction of cytogenetically normal AML without increasing the self-renewal potential. At the molecular level, we found the strong upregulation of Htra3 and the downregulation of Lin28a, leading to enhanced proliferation and the inhibition of apoptosis and differentiation. The co-occurrence of Htra3 overexpression and Lin28a knockdown, in the presence of FLT3-ITD, induced AML with similar morphology as leukemic cells from double-transgenic mice. These leukemic cells were highly sensitive to the proteasome inhibitor carfilzomib. Carfilzomib strongly enhanced the activity of targeting AXL (upstream of FLT3) against murine and human leukemic cells. Our results unravel a unique role of p53 haploinsufficiency or loss in the development of FLT3-ITD + AML.

Anthracycline-free tumor elimination in mice leads to functional and molecular cardiac recovery from cancer-induced alterations in contrast to long-lasting doxorubicin treatment effects.

Systemic effects of advanced cancer impact on the heart leading to cardiac atrophy and functional impairment. Using a murine melanoma cancer model (B16F10 melanoma cells stably transduced with a Ganciclovir (GCV)-inducible suicide gene), the present study analysed the recovery potential of cancer-induced cardiomyopathy with or without use of doxorubicin (Dox). After Dox-free tumor elimination and recovery for 70 ± 5 days, cancer-induced morphologic, functional, metabolic and molecular changes were largely reversible in mice previously bearing tumors. Moreover, grip strength and cardiac response to angiotensin II-induced high blood pressure were comparable with healthy control mice. In turn, addition of Dox (12 mg/kg BW) to melanoma-bearing mice reduced survival in the acute phase compared to GCV-alone induced recovery, while long-term effects on cardiac morphologic and functional recovery were similar. However, Dox treatment was associated with permanent changes in the cardiac gene expression pattern, especially the circadian rhythm pathway associated with the DNA damage repair system. Thus, the heart can recover from cancer-induced damage after chemotherapy-free tumor elimination. In contrast, treatment with the cardiotoxic drug Dox induces, besides well-known adverse acute effects, long-term subclinical changes in the heart, especially of circadian clock genes. Since the circadian clock is known to impact on cardiac repair mechanisms, these changes may render the heart more sensitive to additional stress during lifetime, which, at least in part, could contribute to late cardiac toxicity.

Impaired immune response mediated by prostaglandin E2 promotes severe COVID-19 disease.

The SARS-CoV-2 coronavirus has led to a pandemic with millions of people affected. The present study finds that risk-factors for severe COVID-19 disease courses, i.e. male sex, older age and sedentary life style are associated with higher prostaglandin E2 (PGE2) serum levels in blood samples from unaffected subjects. In COVID-19 patients, PGE2 blood levels are markedly elevated and correlate positively with disease severity. SARS-CoV-2 induces PGE2 generation and secretion in infected lung epithelial cells by upregulating cyclo-oxygenase (COX)-2 and reducing the PG-degrading enzyme 15-hydroxyprostaglandin-dehydrogenase. Also living human precision cut lung slices (PCLS) infected with SARS-CoV-2 display upregulated COX-2. Regular exercise in aged individuals lowers PGE2 serum levels, which leads to increased Paired-Box-Protein-Pax-5 (PAX5) expression, a master regulator of B-cell survival, proliferation and differentiation also towards long lived memory B-cells, in human pre-B-cell lines. Moreover, PGE2 levels in serum of COVID-19 patients lowers the expression of PAX5 in human pre-B-cell lines. The PGE2 inhibitor Taxifolin reduces SARS-CoV-2-induced PGE2 production. In conclusion, SARS-CoV-2, male sex, old age, and sedentary life style increase PGE2 levels, which may reduce the early anti-viral defense as well as the development of immunity promoting severe disease courses and multiple infections. Regular exercise and Taxifolin treatment may reduce these risks and prevent severe disease courses.

ERBB4 and Multiple MicroRNAs That Target ERBB4 Participate in Pregnancy-Related Cardiomyopathy.

BACKGROUND: Peripartum cardiomyopathy (PPCM) is a life-threatening disease in women without previously known cardiovascular disease. It is characterized by a sudden onset of heart failure before or after delivery. Previous studies revealed that the generation of a 16-kDa PRL (prolactin) metabolite, the subsequent upregulation of miR-146a, and the downregulation of the target gene Erbb4 is a common driving factor of PPCM. METHODS: miRNA profiling was performed in plasma of PPCM patients (n=33) and postpartum-matched healthy CTRLs (controls; n=36). Elevated miRNAs in PPCM plasma, potentially targeting ERBB4 (erythroblastic leukemia viral oncogene homolog 4), were overexpressed in cardiomyocytes using lentiviral vectors. Next, cardiac function, cardiac morphology, and PPCM phenotype were investigated after recurrent pregnancies of HZ (heterozygous) cardiomyocyte-specific Erbb4 mice (Erbb4F/+ αMHC-Cre+, n=9) with their age-matched nonpregnant CTRLs (n=9-10). RESULTS: Here, we identify 9 additional highly conserved miRNAs (miR-199a-5p and miR-199a-3p, miR-145a-5p, miR-130a-3p, miR-135a-5p, miR-221-3p, miR-222-3p, miR-23a-3p, and miR19b-3p) that target tyrosine kinase receptor ERBB4 and are over 4-fold upregulated in plasma of PPCM patients at the time of diagnosis. We confirmed that miR-146a, miR-199a-5p, miR-221-3p, miR-222-3p, miR-23a-3p, miR-130a-5p, and miR-135-3p overexpression decreases ERBB4 expression in cardiomyocytes (-29% to -50%; P<0.05). In addition, we demonstrate that genetic cardiomyocyte-specific downregulation of Erbb4 during pregnancy suffices to induce a variant of PPCM in mice, characterized by left ventricular dilatation (postpartum second delivery: left ventricular internal diameter in diastole, +19±7% versus HZ-CTRL; P<0.05), increased atrial natriuretic peptide (ANP) levels (4-fold increase versus HZ-CTRL mice, P<0.001), decreased VEGF (vascular endothelial growth factor) and VE-cadherin levels (-33±17%, P=0.07; -27±20%, P<0.05 versus HZ-CTRL), and histologically enlarged cardiomyocytes (+20±21%, versus HZ-CTRL, P<0.05) but without signs of myocardial apoptosis and inflammation. CONCLUSIONS: ERBB4 is essential to protect the maternal heart from peripartum stress. Downregulation of ERBB4 in cardiomyocytes induced by multiple miRNAs in the peripartum period may be crucial in PPCM pathophysiology. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT00998556.

Perhexiline treatment improves toxic effects of ß-adrenergic receptor stimulation in experimental peripartum cardiomyopathy.

AIMS: Peripartum cardiomyopathy (PPCM) is a pregnancy-associated cardiomyopathy that occurs in previously heart-healthy women towards the end of pregnancy or in the first months after delivery and is characterized by heart failure due to systolic dysfunction. The clinical course of PPCM differs between mild symptoms and severe forms with acute heart failure complicated by cardiogenic shock (CS). Treatment of CS complicating PPCM is challenging, as ß-adrenergic receptor (ß-AR) stimulation seems to be associated with progression of heart failure and adverse outcome. This experimental study aims to examine whether postpartum treatment with the glucose uptake-promoting drug perhexiline alone or as co-treatment with ß-AR stimulation prevents heart failure in the experimental PPCM mouse model. METHODS AND RESULTS: Postpartum (PP) female PPCM-prone mice with a cardiomyocyte-restricted STAT3-deficiency (αMHC-Cretg/+ ;Stat3fl/fl ; CKO) were treated with perhexiline over two to three pregnancies and nursing periods (2/3PP) or were co-treated with perhexiline after one pregnancy (1PP) under chronic ß-AR stimulation using isoproterenol (Iso) infusion. Perhexiline was not able to prevent onset of PPCM in CKO mice (FS: CKO Pexsig-2/3PP: 25 ± 12% vs. CKO Ctrl-2/3PP: 24 ± 9%, n.s.) but attenuated worsening of left ventricular function in response to treatment with the ß-AR agonist Iso (FS: CKO Pexsig-Iso-1PP: 19 ± 4% vs. CKO Ctrl-Iso-1PP: 11 ± 5%, P < 0.05). CONCLUSIONS: Treatment of PPCM patients with ß-AR agonists should be avoided whenever possible. In cases with CS complicating PPCM, when treatment with ß-AR agonists cannot be prevented, co-medication with perhexiline might help to reduce the cardiotoxic side effects of ß-AR stimulation. Clinical data are necessary to further validate this therapeutic approach.

Venetoclax and dexamethasone synergize with inotuzumab ozogamicin-induced DNA damage signaling in B-lineage ALL.

Adult patients with relapsed B-cell precursor acute lymphoblastic leukemia (BCP-ALL) have a dismal prognosis. To improve pharmacotherapy, we analyzed induction of apoptosis by venetoclax and inotuzumab ozogamicin in terms of cytotoxicity and mode of action. Flow cytometry-based analyses of mitochondrial outer membrane permeabilization (MOMP) and ataxia telangiectasia mutated activation demonstrate rapid induction of MOMP by venetoclax and DNA damage signaling by inotuzumab ozogamicin, respectively. In primary ALL samples and patient-derived xenograft (PDX) models, venetoclax and inotuzumab ozogamicin cooperated and synergized in combination with dexamethasone in vitro in all tested samples of ALL. In murine PDX models, inotuzumab ozogamicin, but not venetoclax, induced complete remission in a dose-dependent manner but constantly failed to achieve relapse-free survival. In contrast, combination therapy with venetoclax, dexamethasone, and inotuzumab ozogamicin induced long-term leukemia-free survival and treatment-free survival in all 3 ALL-PDX models tested. These data demonstrate synergistic and highly efficient pharmacotherapy in preclinical models that qualify for evaluation in clinical trials.

Increased prostaglandin-D2 in male STAT3-deficient hearts shifts cardiac progenitor cells from endothelial to white adipocyte differentiation.

Cardiac levels of the signal transducer and activator of transcription factor-3 (STAT3) decline with age, and male but not female mice with a cardiomyocyte-specific STAT3 deficiency conditional knockout (CKO) display premature age-related heart failure associated with reduced cardiac capillary density. In the present study, isolated male and female CKO-cardiomyocytes exhibit increased prostaglandin (PG)-generating cyclooxygenase-2 (COX-2) expression. The PG-degrading hydroxyprostaglandin-dehydrogenase-15 (HPGD) expression is only reduced in male cardiomyocytes, which is associated with increased prostaglandin D2 (PGD2) secretion from isolated male but not female CKO-cardiomyocytes. Reduced HPGD expression in male cardiomyocytes derive from impaired androgen receptor (AR)-signaling due to loss of its cofactor STAT3. Elevated PGD2 secretion in males is associated with increased white adipocyte accumulation in aged male but not female hearts. Adipocyte differentiation is enhanced in isolated stem cell antigen-1 (SCA-1)+ cardiac progenitor cells (CPC) from young male CKO-mice compared with the adipocyte differentiation of male wild-type (WT)-CPC and CPC isolated from female mice. Epigenetic analysis in freshly isolated male CKO-CPC display hypermethylation in pro-angiogenic genes (Fgfr2, Epas1) and hypomethylation in the white adipocyte differentiation gene Zfp423 associated with up-regulated ZFP423 expression and a shift from endothelial to white adipocyte differentiation compared with WT-CPC. The expression of the histone-methyltransferase EZH2 is reduced in male CKO-CPC compared with male WT-CPC, whereas no differences in the EZH2 expression in female CPC were observed. Clonally expanded CPC can differentiate into endothelial cells or into adipocytes depending on the differentiation conditions. ZFP423 overexpression is sufficient to induce white adipocyte differentiation of clonal CPC. In isolated WT-CPC, PGD2 stimulation reduces the expression of EZH2, thereby up-regulating ZFP423 expression and promoting white adipocyte differentiation. The treatment of young male CKO mice with the COX inhibitor Ibuprofen or the PGD2 receptor (DP)2 receptor antagonist BAY-u 3405 in vivo increased EZH2 expression and reduced ZFP423 expression and adipocyte differentiation in CKO-CPC. Thus, cardiomyocyte STAT3 deficiency leads to age-related and sex-specific cardiac remodeling and failure in part due to sex-specific alterations in PGD2 secretion and subsequent epigenetic impairment of the differentiation potential of CPC. Causally involved is the impaired AR signaling in absence of STAT3, which reduces the expression of the PG-degrading enzyme HPGD.

Neuraminidase-1 promotes heart failure after ischemia/reperfusion injury by affecting cardiomyocytes and invading monocytes/macrophages.

Neuraminidase (NEU)1 forms a multienzyme complex with beta-galactosidase (ß-GAL) and protective-protein/cathepsin (PPC) A, which cleaves sialic-acids from cell surface glycoconjugates. We investigated the role of NEU1 in the myocardium after ischemia/reperfusion (I/R). Three days after inducing I/R, left ventricles (LV) of male mice (3 months-old) displayed upregulated neuraminidase activity and increased NEU1, ß-GAL and PPCA expression. Mice hypomorphic for neu1 (hNEU1) had less neuraminidase activity, fewer pro-inflammatory (Lin-CD11b+F4/80+Ly-6Chigh), and more anti-inflammatory macrophages (Lin-CD11b+F4/80+Ly-6Clow) 3 days after I/R, and less LV dysfunction 14 days after I/R. WT mice transplanted with hNEU1-bone marrow (BM) and hNEU1 mice with WT-BM showed significantly better LV function 14 days after I/R compared with WT mice with WT-BM. Mice with a cardiomyocyte-specific NEU1 overexpression displayed no difference in inflammation 3 days after I/R, but showed increased cardiomyocyte hypertrophy, reduced expression and mislocalization of Connexin-43 in gap junctions, and LV dysfunction despite a similar infarct scar size to WT mice 14 days after I/R. The upregulation of NEU1 after I/R contributes to heart failure by promoting inflammation in invading monocytes/macrophages, enhancing cardiomyocyte hypertrophy, and impairing gap junction function, suggesting that systemic NEU1 inhibition may reduce heart failure after I/R.

Effective drug treatment identified by in vivo screening in a transplantable patient-derived xenograft model of chronic myelomonocytic leukemia.

To establish novel and effective treatment combinations for chronic myelomonocytic leukemia (CMML) preclinically, we hypothesized that supplementation of CMML cells with the human oncogene Meningioma 1 (MN1) promotes expansion and serial transplantability in mice, while maintaining the functional dependencies of these cells on their original genetic profile. Using lentiviral expression of MN1 for oncogenic supplementation and transplanting transduced primary mononuclear CMML cells into immunocompromised mice, we established three serially transplantable CMML-PDX models with disease-related gene mutations that recapitulate the disease in vivo. Ectopic MN1 expression was confirmed to enhance the proliferation of CMML cells, which otherwise did not engraft upon secondary transplantation. Furthermore, MN1-supplemented CMML cells were serially transplantable into recipient mice up to 5 generations. This robust engraftment enabled an in vivo RNA interference screening targeting CMML-related mutated genes including NRAS, confirming that their functional relevance is preserved in the presence of MN1. The novel combination treatment with azacitidine and the MEK-inhibitor trametinib additively inhibited ERK-phosphorylation and thus depleted the signal from mutated NRAS. The combination treatment significantly prolonged survival of CMML mice compared to single-agent treatment. Thus, we identified the combination of azacitidine and trametinib as an effective treatment in NRAS-mutated CMML and propose its clinical development.

In peripartum cardiomyopathy plasminogen activator inhibitor-1 is a potential new biomarker with controversial roles.

AIMS: Peripartum cardiomyopathy (PPCM) is a life-threatening heart disease occurring in previously heart-healthy women. A common pathomechanism in PPCM involves the angiostatic 16 kDa-prolactin (16 kDa-PRL) fragment, which via NF-κB-mediated up-regulation of microRNA-(miR)-146a induces vascular damage and heart failure. We analyse whether the plasminogen activator inhibitor-1 (PAI-1) is involved in the pathophysiology of PPCM. METHODS AND RESULTS: In healthy age-matched postpartum women (PP-Ctrl, n = 53, left ventricular ejection fraction, LVEF > 55%), PAI-1 plasma levels were within the normal range (21 ± 10 ng/mL), but significantly elevated (64 ± 38 ng/mL, P < 0.01) in postpartum PPCM patients at baseline (BL, n = 64, mean LVEF: 23 ± 8%). At 6-month follow-up (n = 23), PAI-1 levels decreased (36 ± 14 ng/mL, P < 0.01 vs. BL) and LVEF (49 ± 11%) improved. Increased N-terminal pro-brain natriuretic peptide and Troponin T did not correlate with PAI-1. C-reactive protein, interleukin (IL)-6 and IL-1ß did not differ between PPCM patients and PP-Ctrl. MiR-146a was 3.6-fold (P < 0.001) higher in BL-PPCM plasma compared with PP-Ctrl and correlated positively with PAI-1. In BL-PPCM serum, 16 kDa-PRL coprecipitated with PAI-1, which was associated with higher (P < 0.05) uPAR-mediated NF-κB activation in endothelial cells compared with PP-Ctrl serum. Cardiac biopsies and dermal fibroblasts from PPCM patients displayed higher PAI-1 mRNA levels (P < 0.05) than healthy controls. In PPCM mice (due to a cardiomyocyte-specific-knockout for STAT3, CKO), cardiac PAI-1 expression was higher than in postpartum wild-type controls, whereas a systemic PAI-1-knockout in CKO mice accelerated peripartum cardiac fibrosis, inflammation, heart failure, and mortality. CONCLUSION: In PPCM patients, circulating and cardiac PAI-1 expression are up-regulated. While circulating PAI-1 may add 16 kDa-PRL to induce vascular impairment via the uPAR/NF-κB/miR-146a pathway, experimental data suggest that cardiac PAI-1 expression seems to protect the PPCM heart from fibrosis. Thus, measuring circulating PAI-1 and miR-146a, together with an uPAR/NF-κB-activity assay could be developed into a specific diagnostic marker assay for PPCM, but unrestricted reduction of PAI-1 for therapy may not be advised.

NKL homeobox gene activities in normal and malignant myeloid cells.

Recently, we have documented a hematopoietic NKL-code mapping physiological expression patterns of NKL homeobox genes in early hematopoiesis and in lymphopoiesis, which spotlights genes deregulated in lymphoid malignancies. Here, we enlarge this map to include normal NKL homeobox gene expressions in myelopoiesis by analyzing public expression profiling data and primary samples from developing and mature myeloid cells. We thus uncovered differential activities of six NKL homeobox genes, namely DLX2, HHEX, HLX, HMX1, NKX3-1 and VENTX. We further examined public expression profiling data of 251 acute myeloid leukemia (AML) and 183 myelodysplastic syndrome (MDS) patients, thereby identifying 24 deregulated genes. These results revealed frequent deregulation of NKL homeobox genes in myeloid malignancies. For detailed analysis we focused on NKL homeobox gene NANOG, which acts as a stem cell factor and is correspondingly expressed alone in hematopoietic progenitor cells. We detected aberrant expression of NANOG in a small subset of AML patients and in AML cell line NOMO-1, which served as a model. Karyotyping and genomic profiling discounted rearrangements of the NANOG locus at 12p13. But gene expression analyses of AML patients and AML cell lines after knockdown and overexpression of NANOG revealed regulators and target genes. Accordingly, NKL homeobox genes HHEX, DLX5 and DLX6, stem cell factors STAT3 and TET2, and the NOTCH-pathway were located upstream of NANOG while NKL homeobox genes HLX and VENTX, transcription factors KLF4 and MYB, and anti-apoptosis-factor MIR17HG represented target genes. In conclusion, we have extended the NKL-code to the myeloid lineage and thus identified several NKL homeobox genes deregulated in AML and MDS. These data indicate a common oncogenic role of NKL homeobox genes in both lymphoid and myeloid malignancies. For misexpressed NANOG we identified an aberrant regulatory network, which contributes to the understanding of the oncogenic activity of NKL homeobox genes.

Stable depletion of RUNX1-ETO in Kasumi-1 cells induces expression and enhanced proteolytic activity of Cathepsin G and Neutrophil Elastase.

The oncogenic fusion protein RUNX1-ETO is a product of the t(8;21) translocation and consists of the hematopoietic transcriptional master regulator RUNX1 and the repressor ETO. RUNX1-ETO is found in 10-15% of acute myeloid leukemia and interferes with the expression of genes that are essential for myeloid differentiation. The neutrophil serine protease Cathepsin G is one of the genes suppressed by RUNX1-ETO, but little is known about its impact on the regulation of other lysosomal proteases. By lentiviral transduction of the t(8;21) positive cell line Kasumi-1 with an RUNX1-ETO specific shRNA, we analyzed long-term effects of stable RUNX1-ETO silencing on cellular phenotypes and target gene expression. Stable anti RUNX1-ETO RNAi reduces both proliferation and apoptosis in Kasumi-1 cells. In addition, long-term knockdown of RUNX1-ETO leads to an upregulation of proteolytic activity in Kasumi-1 cells, which may be released in vitro upon cell lysis leading to massive degradation of cellular proteins. We therefore propose that protein expression data of RUNX1-ETO-silenced Kasumi-1 cells must be analyzed with caution, as cell lysis conditions can heavily influence the results of studies on protein expression. Next, a mass spectrometry-based approach was used to identify protease cleavage patterns in RUNX1-ETO-depleted Kasumi-1 cells and Neutrophil Elastase has been identified as a RUNX1-ETO candidate target. Finally, proteolytic activity of Neutrophil Elastase and Cathepsin G was functionally confirmed by si/shRNA-mediated knockdown in Kasumi-1 cells.

Lipid nanoparticle-mediated siRNA delivery for safe targeting of human CML in vivo.

Efficient and safe delivery of siRNA in vivo is the biggest roadblock to clinical translation of RNA interference (RNAi)-based therapeutics. To date, lipid nanoparticles (LNPs) have shown efficient delivery of siRNA to the liver; however, delivery to other organs, especially hematopoietic tissues still remains a challenge. We developed DLin-MC3-DMA lipid-based LNP-siRNA formulations for systemic delivery against a driver oncogene to target human chronic myeloid leukemia (CML) cells in vivo. A microfluidic mixing technology was used to obtain reproducible ionizable cationic LNPs loaded with siRNA molecules targeting the BCR-ABL fusion oncogene found in CML. We show a highly efficient and non-toxic delivery of siRNA in vitro and in vivo with nearly 100% uptake of LNP-siRNA formulations in bone marrow of a leukemic model. By targeting the BCR-ABL fusion oncogene, we show a reduction of leukemic burden in our myeloid leukemia mouse model and demonstrate reduced disease burden in mice treated with LNP-BCR-ABL siRNA as compared with LNP-CTRL siRNA. Our study provides proof-of-principle that fusion oncogene specific RNAi therapeutics can be exploited against leukemic cells and promise novel treatment options for leukemia patients.

Electrophysiological abnormalities in induced pluripotent stem cell-derived cardiomyocytes generated from Duchenne muscular dystrophy patients.

Duchenne muscular dystrophy (DMD) is an X-linked progressive muscle degenerative disease, caused by mutations in the dystrophin gene and resulting in death because of respiratory or cardiac failure. To investigate the cardiac cellular manifestation of DMD, we generated induced pluripotent stem cells (iPSCs) and iPSC-derived cardiomyocytes (iPSC-CMs) from two DMD patients: a male and female manifesting heterozygous carrier. Dystrophin mRNA and protein expression were analysed by qRT-PCR, RNAseq, Western blot and immunofluorescence staining. For comprehensive electrophysiological analysis, current and voltage clamp were used to record transmembrane action potentials and ion currents, respectively. Microelectrode array was used to record extracellular electrograms. X-inactive specific transcript (XIST) and dystrophin expression analyses revealed that female iPSCs underwent X chromosome reactivation (XCR) or erosion of X chromosome inactivation, which was maintained in female iPSC-CMs displaying mixed X chromosome expression of wild type (WT) and mutated alleles. Both DMD female and male iPSC-CMs presented low spontaneous firing rate, arrhythmias and prolonged action potential duration. DMD female iPSC-CMs displayed increased beat rate variability (BRV). DMD male iPSC-CMs manifested decreased If density, and DMD female and male iPSC-CMs showed increased ICa,L density. Our findings demonstrate cellular mechanisms underlying electrophysiological abnormalities and cardiac arrhythmias in DMD.

Optimized induction of mitochondrial apoptosis for chemotherapy-free treatment of BCR-ABL+acute lymphoblastic leukemia.

BCR-ABL+acute lymphoblastic leukemia (ALL) in adults has a poor prognosis with allogeneic stem cell transplantation (SCT) considered the best curative option for suitable patients. We here characterize the curative potential of BH3-mimetics differentially targeting mitochondrial BCL2-family members using a combination therapy approach with dexamethasone and tyrosine kinase inhibitors targeting BCR-ABL. In BCR-ABL + ALL BH3-mimetics act by redistribution of mitochondrial activator BIM, which is strongly required for cytotoxicity of the BCL2-specific BH3-mimetic ABT-199, tyrosine kinase inhibitors (TKIs) and dexamethasone. BIM expression is enhanced by dexamethasone and TKIs and both synergize with ABT-199 in BCR-ABL + ALL. Triple combinations with ABT-199, dexamethasone and TKIs efficiently attenuate leukemia progression both in tissue culture and in primary cell xenotransplantation models. Notably, the dasatinib-containing combination led to treatment- and leukemia-free long-term survival in a BCR-ABL + mouse model. Finally, response to BH3-mimetics can be predicted for individual patients in a clinically relevant setting. These data demonstrate curative targeted and chemotherapy-free pharmacotherapy for BCR-ABL + ALL in a preclinical model. Clinical evaluation, in particular for patients not suitable for allogeneic SCT, is warranted.

A gene therapeutic approach to inhibit calcium and integrin binding protein 1 ameliorates maladaptive remodelling in pressure overload.

Aims: Chronic heart failure is becoming increasingly prevalent and is still associated with a high mortality rate. Myocardial hypertrophy and fibrosis drive cardiac remodelling and heart failure, but they are not sufficiently inhibited by current treatment strategies. Furthermore, despite increasing knowledge on cardiomyocyte intracellular signalling proteins inducing pathological hypertrophy, therapeutic approaches to target these molecules are currently unavailable. In this study, we aimed to establish and test a therapeutic tool to counteract the 22 kDa calcium and integrin binding protein (CIB) 1, which we have previously identified as nodal regulator of pathological cardiac hypertrophy and as activator of the maladaptive calcineurin/NFAT axis. Methods and results: Among three different sequences, we selected a shRNA construct (shCIB1) to specifically down-regulate CIB1 by 50% upon adenoviral overexpression in neonatal rat cardiomyocytes (NRCM), and upon overexpression by an adeno-associated-virus (AAV) 9 vector in mouse hearts. Overexpression of shCIB1 in NRCM markedly reduced cellular growth, improved contractility of bioartificial cardiac tissue and reduced calcineurin/NFAT activation in response to hypertrophic stimulation. In mice, administration of AAV-shCIB1 strongly ameliorated eccentric cardiac hypertrophy and cardiac dysfunction during 2 weeks of pressure overload by transverse aortic constriction (TAC). Ultrastructural and molecular analyses revealed markedly reduced myocardial fibrosis, inhibition of hypertrophy associated gene expression and calcineurin/NFAT as well as ERK MAP kinase activation after TAC in AAV-shCIB1 vs. AAV-shControl treated mice. During long-term exposure to pressure overload for 10 weeks, AAV-shCIB1 treatment maintained its anti-hypertrophic and anti-fibrotic effects, but cardiac function was no longer improved vs. AAV-shControl treatment, most likely resulting from a reduction in myocardial angiogenesis upon downregulation of CIB1. Conclusions: Inhibition of CIB1 by a shRNA-mediated gene therapy potently inhibits pathological cardiac hypertrophy and fibrosis during pressure overload. While cardiac function is initially improved by shCIB1, this cannot be kept up during persisting overload.

miR-125b regulates chemotaxis and survival of bone marrow derived granulocytes in vitro and in vivo.

The evolutionary conserved miR-125b is highly expressed in hematopoietic stem cells (HSC) enhancing self-renewal and survival. Accordingly, over-expression of miR-125b in HSC may induce myeloproliferative neoplasms and leukemia with long latency. During hematopoietic cell maturation miR-125b expression decreases, and the function of miR-125b in mature granulocytes is not yet known. We here use transplantation of miR-125b over-expressing HSC into syngeneic hosts to generate and analyse miR-125b over-expressing granulocytes. Under steady state conditions, miR-125b over-expression inhibits granulocytic chemotaxis and LPS- but not PMA- and TNFα- induced cell death. Inflammatory signals modulate the effects of miR-125b over-expression as demonstrated in a sterile peritonitis and a polymicrobial sepsis model. In particular, survival of mice with miR-125b over-expressing granulocytes is significantly reduced as compared to controls in the polymicrobial sepsis model. These data demonstrate inflammation dependent effects of miR-125b in granulocytes and may point to therapeutic intervention strategies in the future.