For many years, β-adrenergic receptor antagonists (β-blockers or βAR antagonists) have provided significant morbidity and mortality benefits in patients who have sustained acute myocardial ...infarction. More recently, β-adrenergic receptor antagonists have been found to provide survival benefits in patients suffering from heart failure, although the efficacy of different β-blockers varies widely in this condition. One drug, carvedilol, a nonsubtype-selective βAR antagonist, has proven particularly effective in the treatment of heart failure, although the mechanism(s) responsible for this are controversial. Here, we report that among 16 clinically relevant βAR antagonists, carvedilol displays a unique profile of in vitro signaling characteristics. We observed that in β2 adrenergic receptor (β2AR)-expressing HEK-293 cells, carvedilol has inverse efficacy for stimulating Gs-dependent adenylyl cyclase but, nonetheless, stimulates (i) phosphorylation of the receptor's cytoplasmic tail on previously documented G protein-coupled receptor kinase sites; (ii) recruitment of β-arrestin to the β2AR; (iii) receptor internalization; and (iv) activation of extracellular regulated kinase 1/2 (ERK 1/2), which is maintained in the G protein-uncoupled mutant β2ART⁶⁸F,Y¹³²G,Y²¹⁹A (β2ARTYY) and abolished by β-arrestin2 siRNA. Taken together, these data indicate that carvedilol is able to stabilize a receptor conformation which, although uncoupled from Gs, is nonetheless able to stimulate β-arrestin-mediated signaling. We hypothesize that such signaling may contribute to the special efficacy of carvedilol in the treatment of heart failure and may serve as a prototype for a new generation of therapeutic β2AR ligands.
Biased G protein-coupled receptor ligands engage subsets of the receptor signals normally stimulated by unbiased agonists. However, it is unclear whether ligand bias can elicit differentiated ...pharmacology in vivo. Here, we describe the discovery of a potent, selective β-arrestin biased ligand of the angiotensin II type 1 receptor. TRV120027 (Sar-Arg-Val-Tyr-Ile-His-Pro-D-Ala-OH) competitively antagonizes angiotensin II-stimulated G protein signaling, but stimulates β-arrestin recruitment and activates several kinase pathways, including p42/44 mitogen-activated protein kinase, Src, and endothelial nitric-oxide synthase phosphorylation via β-arrestin coupling. Consistent with β-arrestin efficacy, and unlike unbiased antagonists, TRV120027 increased cardiomyocyte contractility in vitro. In rats, TRV120027 reduced mean arterial pressure, as did the unbiased antagonists losartan and telmisartan. However, unlike the unbiased antagonists, which decreased cardiac performance, TRV120027 increased cardiac performance and preserved cardiac stroke volume. These striking differences in vivo between unbiased and β-arrestin biased ligands validate the use of biased ligands to selectively target specific receptor functions in drug discovery.
Nicotinic acid is one of the most effective agents for both lowering triglycerides and raising HDL. However, the side effect of cutaneous flushing severely limits patient compliance. As nicotinic ...acid stimulates the GPCR GPR109A and Gi/Go proteins, here we dissected the roles of G proteins and the adaptor proteins, beta-arrestins, in nicotinic acid-induced signaling and physiological responses. In a human cell line-based signaling assay, nicotinic acid stimulation led to pertussis toxin-sensitive lowering of cAMP, recruitment of beta-arrestins to the cell membrane, an activating conformational change in beta-arrestin, and beta-arrestin-dependent signaling to ERK MAPK. In addition, we found that nicotinic acid promoted the binding of beta-arrestin1 to activated cytosolic phospholipase A2 as well as beta-arrestin1-dependent activation of cytosolic phospholipase A2 and release of arachidonate, the precursor of prostaglandin D2 and the vasodilator responsible for the flushing response. Moreover, beta-arrestin1-null mice displayed reduced cutaneous flushing in response to nicotinic acid, although the improvement in serum free fatty acid levels was similar to that observed in wild-type mice. These data suggest that the adverse side effect of cutaneous flushing is mediated by beta-arrestin1, but lowering of serum free fatty acid levels is not. Furthermore, G protein-biased ligands that activate GPR109A in a beta-arrestin-independent fashion may represent an improved therapeutic option for the treatment of dyslipidemia.
Understanding the biology that underlies histologically similar but molecularly distinct subgroups of cancer has proven difficult because their defining genetic alterations are often numerous, and ...the cellular origins of most cancers remain unknown. We sought to decipher this heterogeneity by integrating matched genetic alterations and candidate cells of origin to generate accurate disease models. First, we identified subgroups of human ependymoma, a form of neural tumour that arises throughout the central nervous system (CNS). Subgroup-specific alterations included amplifications and homozygous deletions of genes not yet implicated in ependymoma. To select cellular compartments most likely to give rise to subgroups of ependymoma, we matched the transcriptomes of human tumours to those of mouse neural stem cells (NSCs), isolated from different regions of the CNS at different developmental stages, with an intact or deleted Ink4a/Arf locus (that encodes Cdkn2a and b). The transcriptome of human supratentorial ependymomas with amplified EPHB2 and deleted INK4A/ARF matched only that of embryonic cerebral Ink4a/Arf−/− NSCs. Notably, activation of Ephb2 signalling in these, but not other, NSCs generated the first mouse model of ependymoma, which is highly penetrant and accurately models the histology and transcriptome of one subgroup of human supratentorial tumour. Further, comparative analysis of matched mouse and human tumours revealed selective deregulation in the expression and copy number of genes that control synaptogenesis, pinpointing disruption of this pathway as a critical event in the production of this ependymoma subgroup. Our data demonstrate the power of cross-species genomics to meticulously match subgroup-specific driver mutations with cellular compartments to model and interrogate cancer subgroups.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
Background
Cross-sectional tumor measures are traditional clinical trial endpoints; however volumetric measures may better assess tumor growth. We determined the correlation and compared the ...prognostic impact of cross-sectional and volumetric measures of progressive disease (PD) among patients with DIPG.
Methods
Imaging and clinical data were abstracted from the International DIPG Registry. Tumor volume and cross-sectional product (CP) were measured with mint Lesion™ software using manual contouring. Correlation between CP and volume (segmented and mathematical ellipsoid model) thresholds of PD were assessed by linear regression. Landmark analyses determined differences in survival (via log-rank) between patients classified as PD versus non-PD by CP and volumetric measurements at 1, 3, 5, 7, and 9 months postradiotherapy (RT). Hazard ratios (HR) for survival after these time points were calculated by Cox regression.
Results
A total of 312 MRIs (46 patients) were analyzed. Comparing change from the previous smallest measure, CP increase of 25% (PD) correlated with a segmented volume increase of 30% (R2 = 0.710), rather than 40% (spherical model extrapolation). CP-determined PD predicted survival at 1 month post-RT (HR = 2.77), but not other time points. Segmented volumetric-determined PD (40% threshold) predicted survival at all imaging timepoints (HRs = 2.57, 2.62, 3.35, 2.71, 16.29), and 30% volumetric PD threshold predicted survival at 1, 3, 5, and 9 month timepoints (HRs = 2.57, 2.62, 4.65, 5.54). Compared to ellipsoid volume, segmented volume demonstrated superior survival associations.
Conclusions
Segmented volumetric assessments of PD correlated better with survival than CP or ellipsoid volume at most time points. Semiautomated tumor volume likely represents a more accurate, prognostically-relevant measure of disease burden in DIPG.
Abstract
Background
Diffuse intrinsic pontine gliomas (DIPG) generally occur in young school-age children, although can occur in adolescents and young adults. The purpose of this study was to ...describe clinical, radiological, pathologic, and molecular characteristics in patients ≥10 years of age with DIPG enrolled in the International DIPG Registry (IDIPGR).
Methods
Patients ≥10 years of age at diagnosis enrolled in the IDIPGR with imaging confirmed DIPG diagnosis were included. The primary outcome was overall survival (OS) categorized as long-term survivors (LTS) (≥24 months) or short-term survivors (STS) (<24 months).
Results
Among 1010 patients, 208 (21%) were ≥10 years of age at diagnosis; 152 were eligible with a median age of 12 years (range 10-26.8). Median OS was 13 (2-82) months. The 1-, 3-, and 5-year OS was 59.2%, 5.3%, and 3.3%, respectively. The 18/152 (11.8%) LTS were more likely to be older (P < .01) and present with longer symptom duration (P < .01). Biopsy and/or autopsy were performed in 50 (33%) patients; 77%, 61%, 33%, and 6% of patients tested had H3K27M (H3F3A or HIST1H3B), TP53, ATRX, and ACVR1 mutations/genome alterations, respectively. Two of 18 patients with IDH1 testing were IDH1-mutant and 1 was a LTS. The presence or absence of H3 alterations did not affect survival.
Conclusion
Patients ≥10 years old with DIPG have a median survival of 13 months. LTS present with longer symptom duration and are likely to be older at presentation compared to STS. ATRX mutation rates were higher in this population than the general DIPG population.
To test the hypothesis that soy protein isolate (SPI) with isoflavones opposes the proliferative effects of exogenous estradiol (E2) on the endometrium after menopause.
Thirty-nine postmenopausal ...women were randomized to receive daily for 6 months either 0.5 mg E2 + placebo, 1.0 mg E2 + placebo, 0.5 mg E2 + 25 g SPI with 120 mg isoflavones, or 1.0 mg E2 + 25 g SPI with 120 mg isoflavones. Primary outcome measures were endometrial histology, ultrasound endometrial thickness, and Ki67 staining quantification, a marker of cellular proliferation. Secondary outcome measures were serum lipids and markers of bone resorption.
Endometrial hyperplasia, endometrial stromal and epithelial cellular proliferation, and sonographically measured endometrial thickness were similarly affected in all groups. SPI did not lessen the beneficial effects of E2 on lipids and markers of bone resorption.
In this pilot study, SPI with isoflavones did not protect the endometrium from E2-induced hyperplasia in postmenopausal women. If higher, long-term doses of isoflavone supplementation are found to be safe for postmenopausal women, then future studies combining E2 with isoflavones may be feasible as an alternative to traditional hormone replacement therapy.
We report the first evidence of charmless semileptonic decays of {ital B} mesons. In the momentum interval 2.4--2.6 GeV/{ital c} where the background from {ital b}{r arrow}{ital cl}{nu} is ...negligible, the average of the measured {ital b}{r arrow}{ital ue}{nu} and {ital b}{r arrow}{ital u}{mu}{nu} partial branching ratios is {Delta}{ital B}{sub {ital ub}}(2.4,2.6) =(1.8{plus minus}0.4{plus minus}0.3){times}10{sup {minus}4}. Inclusion of data from the interval 2.2--2.4 GeV/{ital c}, where the lepton yield is dominated by {ital b}{r arrow}{ital cl}{nu}, gives {Delta}{ital B}{sub {ital ub}}(2.2,2.6) =(3.3{plus minus}0.8{plus minus}0.8){times}10{sup {minus}4}. {vert bar}{ital V}{sub {ital ub}}/V{sub cb}{vert bar} depends on the theoretical model of {ital b}{r arrow}{ital ul}{nu} decay and is approximately 0.1.
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