Extracellular citrate and metabolic adaptations of cancer cells

It is well established that cancer cells acquire energy via the Warburg effect and oxidative phosphorylation. Citrate is considered to play a crucial role in cancer metabolism by virtue of its production in the reverse Krebs cycle from glutamine. Here, we review the evidence that extracellular citrate is one of the key metabolites of the metabolic pathways present in cancer cells. We review the different mechanisms by which pathways involved in keeping redox balance respond to the need of intracellular citrate synthesis under different extracellular metabolic conditions. In this context, we further discuss the hypothesis that extracellular citrate plays a role in switching between oxidative phosphorylation and the Warburg effect while citrate uptake enhances metastatic activities and therapy resistance. We also present the possibility that organs rich in citrate such as the liver, brain and bones might form a perfect niche for the secondary tumour growth and improve survival of colonising cancer cells. Consistently, metabolic support provided by cancer-associated and senescent cells is also discussed. Finally, we highlight evidence on the role of citrate on immune cells and its potential to modulate the biological functions of pro- and anti-tumour immune cells in the tumour microenvironment. Collectively, we review intriguing evidence supporting the potential role of extracellular citrate in the regulation of the overall cancer metabolism and metastatic activity

Impact of massive neutrinos on the Higgs self-coupling and electroweak vacuum stability

The presence of right-handed neutrinos in the type I seesaw mechanism may lead to significant corrections to the RG evolution of the Higgs self-coupling. Compared to the Standard Model case, the Higgs mass window can become narrower, and the cutoff scale become lower. Naively, these effects decrease with decreasing right-handed neutrino mass. However, we point out that the unknown Dirac Yukawa matrix may impact the vacuum stability constraints even in the low scale seesaw case not far away from the electroweak scale, hence much below the canonical seesaw scale of 10^15 GeV. This includes situations in which production of right-handed neutrinos at colliders is possible. We illustrate this within a particular parametrization of the Dirac Yukawas and with explicit low scale seesaw models. We also note the effect of massive neutrinos on the top quark Yukawa coupling, whose high energy value can be increased with respect to the Standard Model case.Comment: 17 pages, 7 figures, minor revisions, version to appear in JHE

Management of Septated Malignant Pleural Effusions

Purpose of Review: We review recent studies of patients with septated malignant pleural effusions, to understand what the clinical implications for patients are and what evidence-based methods should be used to manage these effusions. Recent Findings: Fibrinolytics improve effusion size assessed radiologically in patients with a chest drain inserted for septated malignant pleural effusions but this does not translate into an improvement in breathlessness relief or pleurodesis success. Fibrinolytics have also been used in patients with septated effusions associated with indwelling pleural catheters, but dyspnoea relief has not been assessed in this population. Patients with septated effusions or extensive adhesions appear to have a worse prognosis. Summary: Patients with septated malignant pleural effusions have a poor prognosis and do not gain clinical benefit from fibrinolytics via chest drain. The role of fibrinolytics for septated effusions associated with indwelling pleural catheters requires further study

Different rates of spontaneous mutation of chloroplastic and nuclear viroids as determined by high-fidelity ultra-deep sequencing

[EN] Mutation rates vary by orders of magnitude across biological systems, being higher for simpler genomes. The simplest known genomes correspond to viroids, subviral plant replicons constituted by circular non-coding RNAs of few hundred bases. Previous work has revealed an extremely high mutation rate for chrysanthemum chlorotic mottle viroid, a chloroplastreplicating viroid. However, whether this is a general feature of viroids remains unclear. Here, we have used high-fidelity ultra-deep sequencing to determine the mutation rate in a common host (eggplant) of two viroids, each representative of one family: the chloroplastic eggplant latent viroid (ELVd, Avsunviroidae) and the nuclear potato spindle tuber viroid (PSTVd, Pospiviroidae). This revealed higher mutation frequencies in ELVd than in PSTVd, as well as marked differences in the types of mutations produced. Rates of spontaneous mutation, quantified in vivo using the lethal mutation method, ranged from 1/1000 to 1/800 for ELVd and from 1/7000 to 1/3800 for PSTVd depending on sequencing run. These results suggest that extremely high mutability is a common feature of chloroplastic viroids, whereas the mutation rates of PSTVd and potentially other nuclear viroids appear significantly lower and closer to those of some RNA viruses.This work was supported by the European Research Council (erc.europa.eu; ERC-2011-StG-281191-VIRMUT to RS), the Spanish Ministerio de Economia y Competitividad (www.mineco.gob.es; BFU2013-41329 grant to RS, BFU2014-56812-P grant to RF, and a predoctoral fellowship to ALC), and the Spanish Junta de Comunidades de Castilla-La Mancha (www.castillalamancha.es;postdoctoral fellowship to CB). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.López-Carrasco, MA.; Ballesteros Martínez, C.; Sentandreu, V.; Delgado Villar, SG.; Gago Zachert, SP.; Flores Pedauye, R.; Sanjuan Verdeguer, R. (2017). Different rates of spontaneous mutation of chloroplastic and nuclear viroids as determined by high-fidelity ultra-deep sequencing. PLoS Pathogens. 13(9):1-17. https://doi.org/10.1371/journal.ppat.1006547S117139Ganai, R. A., & Johansson, E. (2016). DNA Replication—A Matter of Fidelity. Molecular Cell, 62(5), 745-755. doi:10.1016/j.molcel.2016.05.003Lynch, M. (2010). Evolution of the mutation rate. Trends in Genetics, 26(8), 345-352. doi:10.1016/j.tig.2010.05.003Sanjuán, R., & Domingo-Calap, P. (2016). Mechanisms of viral mutation. Cellular and Molecular Life Sciences, 73(23), 4433-4448. doi:10.1007/s00018-016-2299-6Gago, S., Elena, S. F., Flores, R., & Sanjuan, R. (2009). 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Viroid RNA redirects host DNA ligase 1 to act as an RNA ligase. Proceedings of the National Academy of Sciences, 109(34), 13805-13810. doi:10.1073/pnas.1206187109Brass, J. R. J., Owens, R. A., Matoušek, J., & Steger, G. (2017). Viroid quasispecies revealed by deep sequencing. RNA Biology, 14(3), 317-325. doi:10.1080/15476286.2016.1272745Bull, J. J., Sanjuán, R., & Wilke, C. O. (2007). Theory of Lethal Mutagenesis for Viruses. Journal of Virology, 81(6), 2930-2939. doi:10.1128/jvi.01624-06Cuevas, J. M., González-Candelas, F., Moya, A., & Sanjuán, R. (2009). Effect of Ribavirin on the Mutation Rate and Spectrum of Hepatitis C Virus In Vivo. Journal of Virology, 83(11), 5760-5764. doi:10.1128/jvi.00201-09Ribeiro, R. M., Li, H., Wang, S., Stoddard, M. B., Learn, G. H., Korber, B. T., … Perelson, A. S. (2012). Quantifying the Diversification of Hepatitis C Virus (HCV) during Primary Infection: Estimates of the In Vivo Mutation Rate. 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Proceedings of the National Academy of Sciences, 55(6), 1504-1511. doi:10.1073/pnas.55.6.1504López-Carrasco, A., Gago-Zachert, S., Mileti, G., Minoia, S., Flores, R., & Delgado, S. (2015). The transcription initiation sites of eggplant latent viroid strands map within distinct motifs in theirin vivoRNA conformations. RNA Biology, 13(1), 83-97. doi:10.1080/15476286.2015.1119365Keese, P., & Symons, R. H. (1985). Domains in viroids: evidence of intermolecular RNA rearrangements and their contribution to viroid evolution. Proceedings of the National Academy of Sciences, 82(14), 4582-4586. doi:10.1073/pnas.82.14.4582López-Carrasco, A., & Flores, R. (2016). Dissecting the secondary structure of the circular RNA of a nuclear viroid in vivo: A «naked» rod-like conformation similar but not identical to that observed in vitro. RNA Biology, 14(8), 1046-1054. doi:10.1080/15476286.2016.1223005Flores, R., Hernandez, C., de la Peña, M., Vera, A., & Daros, J.-A. (2001). 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Nuevas fuentes de antioxidantes naturales: caracterización de compuestos bioactivos en cinco frutos nativos de Chile.

Diferentes berries de la zona centro y sur de Chile fueron analizados con el fin de buscar fuentes promisorias de polifenoles con clara actividad sobre la salud humana. Se estudiaron cinco bayas nativas: arrayan, frutilla blanca, murtilla y calafate, y un berry tradicional (uva tintorera). Se determinó in vitro sus propiedades antioxidantes según el ensayo de polifenoles totales de Folin Ciocalteu, antocianinas por pH diferencial, capacidad antioxidante por medición de capacidad de reducción del radical libre 2.2-difenil-1picrilhidracilo (DPPH) y poder de reducción férrica (FRAP) y perfil químico por HPLC-DAD. De los cinco berries, calafate registró el valor más alto (1066,4 ± 24,9 mg GAE/100g de muestra) para polifenoles totales y antocianinas (1031,9 ± 48,1 mg de cianidina-3-glucósido/100g de muestra) seguido por uva tintorera. Calafate presentó excelente poder reductor (11279,2 ± 2027,4 umol Trolox/100g ensayo FRAP y 5235,0 ± 445,9, umol/100g en PPH). El perfil químico de antocianinas mostró delfinidina, cianidina, malvidina, petunidina, peonidina y pelargonidina en los cinco berries. Alrededor de 30 flavonoles derivados de quercetina, myricetina e isorhamnetina fueron identificados así cómo elagitaninos presentes en frutilla blanca, compuestos muy interesantes para estudios posteriores. Estos resultados contribuyen a destacar el uso potencial de estos berries como alimentos funcionales.Berries from central and southern Chile were analyzed in order to find promising sources of polyphenols with clear activity on human health. Five native fruits like arrayan, white strawberry, murtilla and calafate, and a traditional berry (grape called “tintorera”) were studied. Antioxidant properties were determined in vitro according to the total polyphenol assay of Folin Ciocalteu, anthocyanins by differential pH, antioxidant capacity by measuring the capacity of reduction of the free radical 2.2-diphenyl-1-picrylhydracil (DPPH) and iron reducing capacity (FRAP) and chemical profile by HPLC-DAD. Calafate showed the highest value (1066.4 ± 24.9 mg gallic acid / 100g sample) for total polyphenols and anthocyanins (1031.9 ± 48.1 mg of cyanidin-3-glucoside / 100g of sample) followed by blue grape. Calafate displayed excellent reducing power (11279.2 ± 2027.4 umol Trolox / 100g FRAP assay and 5235.0 ± 445.9, umol / 100g in DPPH), followed by grape. The chemical profile ofanthocyanins showed delphinidin, cyanidin, malvidin, petunidin, peonidin and pelargonidin in the five berries. Around 30 flavonols derived from quercetin, yricetin and sorhamnetin were identified as well as ellagitannins present in white trawberry, very interesting compounds for further studies. These results contribute to highlight the potential use of these berries as functional foods

Considering Intra-individual Genetic Heterogeneity to Understand Biodiversity

In this chapter, I am concerned with the concept of Intra-individual Genetic Hetereogeneity (IGH) and its potential influence on biodiversity estimates. Definitions of biological individuality are often indirectly dependent on genetic sampling -and vice versa. Genetic sampling typically focuses on a particular locus or set of loci, found in the the mitochondrial, chloroplast or nuclear genome. If ecological function or evolutionary individuality can be defined on the level of multiple divergent genomes, as I shall argue is the case in IGH, our current genetic sampling strategies and analytic approaches may miss out on relevant biodiversity. Now that more and more examples of IGH are available, it is becoming possible to investigate the positive and negative effects of IGH on the functioning and evolution of multicellular individuals more systematically. I consider some examples and argue that studying diversity through the lens of IGH facilitates thinking not in terms of units, but in terms of interactions between biological entities. This, in turn, enables a fresh take on the ecological and evolutionary significance of biological diversity

ruvA Mutants that resolve Holliday junctions but do not reverse replication forks

RuvAB and RuvABC complexes catalyze branch migration and resolution of Holliday junctions (HJs) respectively. In addition to their action in the last steps of homologous recombination, they process HJs made by replication fork reversal, a reaction which occurs at inactivated replication forks by the annealing of blocked leading and lagging strand ends. RuvAB was recently proposed to bind replication forks and directly catalyze their conversion into HJs. We report here the isolation and characterization of two separation-of-function ruvA mutants that resolve HJs, based on their capacity to promote conjugational recombination and recombinational repair of UV and mitomycin C lesions, but have lost the capacity to reverse forks. In vivo and in vitro evidence indicate that the ruvA mutations affect DNA binding and the stimulation of RuvB helicase activity. This work shows that RuvA's actions at forks and at HJs can be genetically separated, and that RuvA mutants compromised for fork reversal remain fully capable of homologous recombination