A liaison between mTOR signaling, ribosome biogenesis and cancer

The ability to translate genetic information into functional proteins is considered a landmark in evolution. Ribosomes have evolved to take on this responsibility and, although there are some differences in their molecular make-up, both prokaryotes and eukaryotes share a common structural architecture and similar underlying mechanisms of protein synthesis. Understanding ribosome function and biogenesis has been the focus of extensive research since the early days of their discovery. In the last decade however, new and unexpected roles have emerged that place deregulated ribosome biogenesis and protein synthesis at the crossroads of pathological settings, particularly cancer, revealing a set of novel cellular checkpoints. Moreover, it is also becoming evident that mTOR signaling, which regulates an array of anabolic processes, including ribosome biogenesis, is often exploited by cancer cells to sustain proliferation through the upregulation of global protein synthesis. The use of pharmacological agents that interfere with ribosome biogenesis and mTOR signaling has proven to be an effective strategy to control cancer development clinically. Here we discuss the most recent findings concerning the underlying mechanisms by which mTOR signaling controls ribosome production and the potential impact of ribosome biogenesis in tumor development

Clinical inertia and its impact on treatment intensification in people with type 2 diabetes mellitus

Many people with type 2 diabetes mellitus (T2DM) fail to achieve glycaemic control promptly after diagnosis and do not receive timely treatment intensification. This may be in part due to 'clinical inertia', defined as the failure of healthcare providers to initiate or intensify therapy when indicated. Physician-, patient- and healthcare-system-related factors all contribute to clinical inertia. However, decisions that appear to be clinical inertia may, in fact, be only 'apparent' clinical inertia and may reflect good clinical practice on behalf of the physician for a specific patient. Delay in treatment intensification can happen at all stages of treatment for people with T2DM, including prescription of lifestyle changes after diagnosis, introduction of pharmacological therapy, use of combination therapy where needed and initiation of insulin. Clinical inertia may contribute to people with T2DM living with suboptimal glycaemic control for many years, with dramatic consequences for the patient in terms of quality of life, morbidity and mortality, and for public health because of the huge costs associated with uncontrolled T2DM. Because multiple factors can lead to clinical inertia, potential solutions most likely require a combination of approaches involving fundamental changes in medical care. These could include the adoption of a person-centred model of care to account for the complex considerations influencing treatment decisions by patients and physicians. Better patient education about the progressive nature of T2DM and the risks inherent in long-term poor glycaemic control may also reinforce the need for regular treatment reviews, with intensification when required

Change in HbA 1c Across the Baseline HbA 1c Range in Type 2 Diabetes Patients Receiving Once-Weekly Dulaglutide Versus Other Incretin Agents

Introduction: This exploratory post hoc analysis investigated the relative changes in glycated haemoglobin (HbA1c) in patients with type 2 diabetes mellitus (T2DM) treated with dulaglutide versus active comparators across a continuous range of baseline HbA1c values using data from three phase III randomised controlled trials. Methods: Data from patients receiving once-weekly dulaglutide 0.75 and 1.5 mg, once-daily sitagliptin 100 mg, once-daily liraglutide 1.8 mg or twice-daily exenatide 10 ?g in the intent-to-treat populations in the AWARD-5, AWARD-6 and AWARD-1 trials were analysed using last observation carried forward analysis of covariance. Starting with the predefined statistical model from each study, the type of association between HbA1c baseline and change at 26 weeks was modelled. Consistency of treatment effect was assessed via treatment-by-baseline HbA1c interaction terms. Results: Improvements in HbA1c occurred in all treatment groups across the entire baseline HbA1c range. The relationship between HbA1c baseline and magnitude of change was linear in all treatment groups, with greater reductions in patients with higher baseline HbA1c values. Across the continuum of baseline HbA1c values, patients treated with dulaglutide 1.5 mg achieved a similar mean HbA1c reduction to patients receiving liraglutide 1.8 mg and a greater reduction than patients receiving twice-daily exenatide or sitagliptin. In AWARD-5, the treatment-by-baseline HbA1c interaction P value (0.001) demonstrated progressively greater HbA1c reduction in dulaglutide-treated compared with sitagliptin-treated patients as baseline HbA1c increased. Conclusion: Our results suggest that dulaglutide is an appropriate therapeutic option for patients with T2DM across a wide range of baseline HbA1c values, including those with poor metabolic control

Phosphofructokinases Axis Controls Glucose-Dependent mTORC1 Activation Driven by E2F1.

Cancer cells rely on mTORC1 activity to coordinate mitogenic signaling with nutrients availability for growth. Based on the metabolic function of E2F1, we hypothesize that glucose catabolism driven by E2F1 could participate on mTORC1 activation. Here, we demonstrate that glucose potentiates E2F1-induced mTORC1 activation by promoting mTORC1 translocation to lysosomes, a process that occurs independently of AMPK activation. We showed that E2F1 regulates glucose metabolism by increasing aerobic glycolysis and identified the PFKFB3 regulatory enzyme as an E2F1-regulated gene important for mTORC1 activation. Furthermore, PFKFB3 and PFK1 were found associated to lysosomes and we demonstrated that modulation of PFKFB3 activity, either by substrate accessibility or expression, regulates the translocation of mTORC1 to lysosomes by direct interaction with Rag B and subsequent mTORC1 activity. Our results support a model whereby a glycolytic metabolon containing phosphofructokinases transiently interacts with the lysosome acting as a sensor platform for glucose catabolism toward mTORC1 activity

The activity of hsp90α promoter is regulated by NF-κB transcription factors

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V-ATPase, a master effector of E2F1-mediated lysosomal trafficking, mTORC1 activation and autophagy

In addition to being a master regulator of cell cycle progression, E2F1 regulates other associated biological processes, including growth and malignancy. Here, we uncover a regulatory network linking E2F1 to lysosomal trafficking and mTORC1 signaling that involves v-ATPase regulation. By immunofluorescence and time-lapse microscopy we found that E2F1 induces the movement of lysosomes to the cell periphery, and that this process is essential for E2F1-induced mTORC1 activation and repression of autophagy. Gain- and loss-of-function experiments reveal that E2F1 regulates v-ATPase activity and inhibition of v-ATPase activity repressed E2F1-induced lysosomal trafficking and mTORC1 activation. Immunoprecipitation experiments demonstrate that E2F1 induces the recruitment of v-ATPase to lysosomal RagB GTPase, suggesting that E2F1 regulates v-ATPase activity by enhancing the association of V0 and V1 v-ATPase complex. Analysis of v-ATPase subunit expression identified B subunit of V0 complex, ATP6V0B, as a transcriptional target of E2F1. Importantly, ATP6V0B ectopic-expression increased v-ATPase and mTORC1 activity, consistent with ATP6V0B being responsible for mediating the effects of E2F1 on both responses. Our findings on lysosomal trafficking, mTORC1 activation and autophagy suppression suggest that pharmacological intervention at the level of v-ATPase may be an efficacious avenue for the treatment of metastatic processes in tumors overexpressing E2F1

The Real-World Observational Prospective Study of Health Outcomes with Dulaglutide and Liraglutide in Type 2 Diabetes Patients (TROPHIES): Design and Baseline Characteristics

Introduction: The TROPHIES observational study enrolled patients with type 2 diabetes mellitus (T2DM) initiating their first injectable treatment with the glucagon-like peptide 1 receptor agonists (GLP-1 RAs) dulaglutide or liraglutide. This manuscript focuses on the study design, baseline characteristics of the enrolled population, and factors associated with GLP-1 RA choice. Methods: TROPHIES is a prospective, observational, 24-month study conducted in France, Germany, and Italy. Inclusion criteria include adult patients with T2DM, naïve to injectable antihyperglycemic treatments, initiating dulaglutide or liraglutide per routine clinical practice. The primary outcome is the duration of treatment on dulaglutide or liraglutide without a significant treatment change. Results: The analysis included 2181 patients (dulaglutide, 1130; liraglutide, 1051) (cutoff date May 15, 2019). The population was 56% male with mean [standard deviation (SD)] patient characteristics at baseline as follows: age, 59.2 (11.0) years; body mass index (BMI), 33.9 (6.6) kg/m2; T2DM duration, 8.5 (6.9) years; and glycated hemoglobin (HbA1c), 8.2 (1.3)%. Between-cohort demographic and clinical characteristics were balanced. The mean (SD) HbA1c and BMI values for French, German, and Italian patients were, respectively, 8.6 (1.4)%, 8.2 (1.4)%, 8.0 (0.8)%; 33.3 (6.1) kg/m2, 36.0 (7.2) kg/m2, and 32.6 (5.9) kg/m2. Conclusion: This study analysis at baseline provides an opportunity to evaluate between-country differences in baseline HbA1c, weight, macrovascular complications, and factors driving GLP-1 RA selection for patients with T2DM in daily practice

BAG3: a multifaceted protein that regulates major cell pathways

Bcl2-associated athanogene 3 (BAG3) protein is a member of BAG family of co-chaperones that interacts with the ATPase domain of the heat shock protein (Hsp) 70 through BAG domain (110–124 amino acids). BAG3 is the only member of the family to be induced by stressful stimuli, mainly through the activity of heat shock factor 1 on bag3 gene promoter. In addition to the BAG domain, BAG3 contains also a WW domain and a proline-rich (PXXP) repeat, that mediate binding to partners different from Hsp70. These multifaceted interactions underlie BAG3 ability to modulate major biological processes, that is, apoptosis, development, cytoskeleton organization and autophagy, thereby mediating cell adaptive responses to stressful stimuli. In normal cells, BAG3 is constitutively present in a very few cell types, including cardiomyocytes and skeletal muscle cells, in which the protein appears to contribute to cell resistance to mechanical stress. A growing body of evidence indicate that BAG3 is instead expressed in several tumor types. In different tumor contexts, BAG3 protein was reported to sustain cell survival, resistance to therapy, and/or motility and metastatization. In some tumor types, down-modulation of BAG3 levels was shown, as a proof-of-principle, to inhibit neoplastic cell growth in animal models. This review attempts to outline the emerging mechanisms that can underlie some of the biological activities of the protein, focusing on implications in tumor progression

Nucleotide depletion reveals the impaired ribosomebiogenesis checkpoint as a barrier against DNA damage

Many oncogenes enhance nucleotide usage to increase ribosome content, DNA replication, and cell proliferation, but in parallel trigger p53 activation. Both the impaired ribosome biogenesis checkpoint (IRBC) and the DNA damage response (DDR) have been implicated in p53 activation following nucleotide depletion. However, it is difficult to reconcile the two checkpoints operating together, as the IRBC induces p21‐mediated G1 arrest, whereas the DDR requires that cells enter S phase. Gradual inhibition of inosine monophosphate dehydrogenase (IMPDH), an enzyme required for de novo GMP synthesis, reveals a hierarchical organization of these two checkpoints. We find that the IRBC is the primary nucleotide sensor, but increased IMPDH inhibition leads to p21 degradation, compromising IRBC‐mediated G1 arrest and allowing S phase entry and DDR activation. Disruption of the IRBC alone is sufficient to elicit the DDR, which is strongly enhanced by IMPDH inhibition, suggesting that the IRBC acts as a barrier against genomic instability

The transcribed pseudogene RPSAP52 enhances the oncofetal HMGA2-IGF2BP2-RAS axis through LIN28B-dependent and independent let-7 inhibition

Altres ajuts: We thank CERCA Program/Generalitat de Catalunya for their institutional support. This work was also supported by the Fundació La Marató de TV3, grant number #20131610 (S.G.), the AECC-Junta de Barcelona (S.G.), the Fundación Científica de la AECC under grant GCB13131578DEÁ (O.M.T.), the Health and Science Departments of the Catalan Government (Gen-eralitat de Catalunya). C.O.-M. is a pre-doctoral fellow funded by the Basque Government (PRE_2013_1_1009).One largely unknown question in cell biology is the discrimination between inconsequential and functional transcriptional events with relevant regulatory functions. Here, we find that the oncofetal HMGA2 gene is aberrantly reexpressed in many tumor types together with its antisense transcribed pseudogene RPSAP52. RPSAP52 is abundantly present in the cytoplasm, where it interacts with the RNA binding protein IGF2BP2/IMP2, facilitating its binding to mRNA targets, promoting their translation by mediating their recruitment on polysomes and enhancing proliferative and self-renewal pathways. Notably, downregulation of RPSAP52 impairs the balance between the oncogene LIN28B and the tumor suppressor let-7 family of miRNAs, inhibits cellular proliferation and migration in vitro and slows down tumor growth in vivo. In addition, high levels of RPSAP52 in patient samples associate with a worse prognosis in sarcomas. Overall, we reveal the roles of a transcribed pseudogene that may display properties of an oncofetal master regulator in human cancers