1,720,960 research outputs found
The mitochondrial Ca2+ homeostasis in breast cancer
Full text linkTriple-negative breast cancer (TNBC) represents one of the most aggressive breast tumour subtypes but the molecular mechanisms promoting tumour aggressiveness is still undefined. Several findings indicate that cancer cells undergo a complex metabolic reprogramming to satisfy the increased requirement of macromolecules and energy necessary for proliferation, and mitochondria have a fundamental role in this mechanism. Indeed, mitochondria are producers of intermediates for lipid, nucleic acid, and protein synthesis but also players of control of the cell fate. In these processes, mitochondrial calcium plays a pivotal role: in physiological conditions, it directly regulates three enzymes of the TCA cycle, i.e. pyruvate-, α-ketoglutarate- and isocitrate-dehydrogenases (Berridge et al., 2000); while in pathological conditions, mitochondrial Ca2+ overload sensitizes cells to apoptotic challenges by triggering the opening of the mitochondrial permeability transition pore (mPTP) (Basso et al., 2005).
The channel responsible for entry into the mitochondria is the mitochondrial calcium uniporter (MCU) (De Stefani et al., 2011) (Baughman et al., 2011) that is composed of both channel-forming subunits and regulatory proteins. In addition to MCU, MCUb, the dominant-negative isoform of MCU (Raffaello et al., 2013), and the essential MCU regulator EMRE (Sancak et al., 2013) contribute to channel formation. The MICU protein family, comprising MICU1, MICU2 and MICU3, regulates the sophisticated mechanism of mitochondrial calcium uptake by modulating MCU function (De Stefani et al., 2016). While MICU3 expression is mainly confined to the nervous system, MICU1 and MICU2 are ubiquitous. MICU1 and MICU2 form a regulatory heterodimer that finely tunes MCU activity. Within the heterodimer, MICU1 increases and MICU2 reduces MCU activity. Both MICU1 and MICU2 possess EF-hand domains that bind Ca2+ ions. At low extra-mitochondrial [Ca2+], MICU2 plays a dominant effect thus inhibiting MCU activity. At higher extra-mitochondrial [Ca2+], MICU1 exerts a stimulatory effect allowing the prompt response of mitochondria to cytosolic [Ca2+] rises.
It was already demonstrated that genetic inhibition of MCU expression causes a significant decline in TNBC metastatic cell motility and invasiveness (Tosatto et al., 2016) and hampers metastasis formation in vivo.
To further understand the role of the mitochondrial Ca2+ uptake in TNBC, and to explore possible therapeutic targets, we aimed to study the role of the MICU1 and MICU2 in TNBC progression, both in vitro and in vivo. Firstly, we detected a decrease in MICU1 expression levels in tumour samples compared to normal breast samples underlining the importance of mitochondrial Ca2+ uptake in breast tumour development. Then, we demonstrated that the mitochondrial Ca2+ uptake inhibition, by overexpression ofMICU1 and MICU2 isoforms in which the EF-hands are mutated in order to hamper Ca2+ binding, causes a significant decline in TNBC cell motility in vitro and in tumour growth and metastasis formation in vivo. In these conditions, mROS production was significantly reduced, suggesting that mROS might play a crucial role in MICU1/2 dependent control of malignancy.
In the second part of the thesis, we studied the role of MCUb, the dominant-negative isoform of MCU. While MCU expression increases with tumour progression, the expression of MCUb decreases (Tosatto et al., 2016). Thus, we decided to overexpress MCUb in a TNBC cell line. Overexpression of MCUb partially inhibits tumor cell growth. Moreover, MCUb overexpression causes a significant decline in TNBC cell motility.
Our results highlight a crucial role of the mitochondrial Ca2+ uptake in the control of TNBC metastatic potential and indicate that the MCU regulatory subunits and MCUb could represent novel therapeutic target for clinical interventio
The Unfolded Protein Response and Autophagy in Chronic Liver Diseases, HCC and Metastases
No full textHigh-Throughput Screening Using Photoluminescence Probe to Measure Intracellular Calcium Levels
No full textAequorin, a 22 kDa protein produced by the jellyfish Aequorea victoria, was the first probe used to measure Ca2+ concentrations ([Ca2+]) of specific intracellular organelles in intact cells. After the binding of Ca2+ to three high-affinity binding sites, an irreversible reaction occurs leading to the emission of photons that is proportional to [Ca2+]. While native aequorin is suitable for measuring cytosolic [Ca2+] after cell stimulation in a range from 0.5 to 10 mu M, it cannot be used in organelles where [Ca2+] is much higher, such as in the lumen of endoplasmic/sarcoplasmic reticulum (ER/SR) and mitochondria. However, some modifications made on aequorin itself or on coelenterazine, its lipophilic prosthetic luminophore, and the addition of targeting sequences or the fusion with resident proteins allowed the specific organelle localization and the measurements of intra-organelle Ca2+ levels. In the last years, the development of multiwell plate readers has opened the possibility to perform aequorin-based high-throughput screenings and has overcome some limitation of the standard method. Here we present the procedure for expressing, targeting, and reconstituting aequorin in intact cells and for measuring Ca2+ in the bulk cytosol, mitochondria, and ER by a high-throughput screening system
Genetic variation of clock genes and cancer risk: a field synopsis and meta-analysis
No full textThe number of studies on the association between clock genes' polymorphisms and cancer susceptibility has increased over the last years but the results are often conflicting and no comprehensive overview and quantitative summary of the evidence in this field is available.
RESULTS:
Literature search identified 27 eligible studies comprising 96756 subjects (cases: 38231) and investigating 687 polymorphisms involving 14 clock genes. Overall, 1025 primary and subgroup meta-analyses on 366 gene variants were performed. Study distribution by tumor was as follows: breast cancer (n=15), prostate cancer (n=3), pancreatic cancer (n=2), non-Hodgkin's lymphoma (n=2), glioma (n=1), chronic lymphocytic leukemia (n=1), colorectal cancer (n=1), non-small cell lung cancer (n=1) and ovarian cancer (n=1).We identified 10 single nucleotide polymorphisms (SNPs) significantly associated with cancer risk: NPAS2 rs10165970 (mixed and breast cancer shiftworkers), rs895520 (mixed), rs17024869 (breast) and rs7581886 (breast); CLOCK rs3749474 (breast) and rs11943456 (breast); RORA rs7164773 (breast and breast cancer postmenopausal), rs10519097 (breast); RORB rs7867494 (breast cancer postmenopausal), PER3 rs1012477 (breast cancer subgroups) and assessed the level of quality evidence to be intermediate. We also identified polymorphisms with lower quality statistically significant associations (n=30).
CONCLUSIONS:
Our work supports the hypothesis that genetic variation of clock genes might affect cancer risk. These findings also highlight the need for more efforts in this research field in order to fully establish the contribution of clock gene variants to the risk of developing cancer.
METHODS:
We conducted a systematic review and meta-analysis of the evidence on the association between clock genes' germline variants and the risk of developing cancer. To assess result credibility, summary evidence was graded according to the Venice criteria and false positive report probability (FPRP) was calculated to further validate result noteworthiness. Subgroup meta-analysis was also performed based on participant features and tumor type. The breast cancer subgroup was further stratified by work conditions, estrogen receptor/progesterone receptor status and menopausal status, conditions associated with the risk of breast cancer in different studies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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