1,721,121 research outputs found
Distinct functional roles of microRNA-23b and microRNA-26a in breast cancer pathogenesis
Get PDFTumour formation and metastasis are distinct processes that arise from cumulative alterations of genomic and epigenetic regulation. Uncontrolled modulation of cell cycle-related genes is crucial to tumour growth and additional genetic modifications provide cancer cells with motile and invasive phenotypes, leading to metastatic dissemination.
The cytoskeleton constitutes the structural support to cell motility, invasion and adhesion. Among the best-characterised cytoskeletal modulators are the p21-activated kinases (PAKs). In breast cancer (BC), the HER2 pathway controls the cytoskeletal dynamics and cell motility via PAK activation, through distinct downstream signaling mechanisms.
MicroRNAs (miRNAs) are small, non-coding RNAs that modulate gene expression post-transcriptionally. MiRNAs dysregulation can contribute to tumorigenicity, cell motility and metastasis by affecting relevant signaling pathways.
We identified PAK2 as target of both miR-23b and miR-26a, implicating a direct role for these miRNAs in cytoskeletal remodeling. Experimentally, expression of miR-23b and miR-26a in BC cells promotes focal adhesions and cell spreading on substrates, but miR-23b alone controls cell-cell junctions and lamellipodia formation.
Despite sharing the same target, the two miRNAs show additional distinct functions. MiR-26a overexpression in BC leads to formation of aneuploid cells associated with higher tumorigenicity. On the other hand, miR-23b inhibition enhances BC cell migration, invasion and metastasis in vivo. Clinically, low miR-23b levels correlate with metastatic development in BC patients. Mechanistically, growth factor-mediated signal transductions activate the transcription factor AP-1 and we show that this transcriptionally reduces miR-23b expression thus releasing PAK2 from its translational inhibition. The distinct cellular phenotypes described by the two miRNAs indicate that their global functions depend upon all the genes they regulate. Using RNA-sequencing and luciferase reporter assays, we validated a subset of genes as direct targets of either the two miRNAs. These genes are crucial to distinct molecular pathways and contribute to elucidate the observed phenotypes induced by miR-23b and miR-26a modulation.Open Acces
Investigation of the function of LMTK3 in breast cancer invasion and transcriptional regulation
Get PDFThe role of Lemur tyrosine kinase 3 (LMTK3) and its association with cell proliferation and endocrine resistance in breast cancer due to its ability of regulating estrogen receptor α (ERα) has been previously addressed in our laboratory. However, the ER-independent function of LMTK3 has not been studied yet.
We found that LMTK3 promotes the development of a metastatic phenotype by inducing the expression of genes encoding integrin subunits. Invasive behaviour such as actin cytoskeleton remodelling and focal adhesion were positively correlated with the abundance of LMTK3 formation in various breast cancer cell lines. Using SILAC (stable isotope labelling by amino acids in cell culture) proteomic analysis, we found that LMTK3 increases the protein levels of integrin subunits α5 and β1 through activating the CDC42 GTPase, which promotes integrin α5 and β1 expression via the transcription factor serum response factor (SRF). Furthermore, abundance of LMTK3 was positively correlated with that of integrin β1 in breast cancer patients’ tumours.
As LMTK3 is also localised in the nucleus, we then investigated its nuclear function. We mapped LMTK3 binding across the genome using ChIP-seq and found that LMTK3 binding events are correlated with repressive chromatin markers. We further identified KRAB-associated protein 1 (KAP1) as a binding partner of LMTK3. The LMTK3/KAP1 interaction is stabilized by PP1α, which suppresses KAP1 phosphorylation specifically at LMTK3-associated chromatin regions, inducing chromatin condensation and resulting in transcriptional repression of LMTK3-bound tumour suppressor-like genes. Furthermore, LMTK3 functions at distal regions in tethering the chromatin to the nuclear periphery, resulting in H3K9me3 modification and gene silencing. In summary, we propose a model where a scaffolding function of nuclear LMTK3 promotes cancer progression through chromatin remodelling in an ERα-independent and kinase-independent manner.Open Acces
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
MicroRNA implications in chemotherapy-induced cardiac toxicity
Get PDFThe use of anthracyclines such as doxorubicin (DOX) has improved mortality and morbidity in cancer patients, yet associated risks of cardiomyopathy have limited their clinical application. DOX-associated cardiotoxicity typically progresses to heart failure (HF). The knowledge of the mechanisms underlying DOX-related cardiac dysfunction is currently limited, hampering the development of cardioprotective strategies.
MicroRNAs (miRNAs) are gene expression regulators that play potent roles in both cardiovascular disease and cancer. We wished to investigate DOX-induced changes in cardiac miRNA expression and the potential alteration of cellular processes downstream.
Myocardial miRNA profiling was performed after DOX injury, either via acute administration to cardiomyocytes in vitro or chronic exposure in vivo, and compared to miRNA profiles from infarcted hearts. We identified an overlapping down-regulation of several members of the miR-30 family. Subsequent experimental validation of a bioinformatically predicted subset of target genes allowed us to confirm four novel miR-30 targets: β1- and β2-adrenoceptors (β1AR, β2AR), Gi alpha 2 (Giα-2) and the pro-apoptotic gene BNIP3L, all of which are essential in cardiomyocytes. The implications of the β-adrenergic pathway in HF are extensively described. Importantly, we show a preferential βAR inhibition by miR-30, having a β-blocker like effect. Additionally, we demonstrate that high miR-30 levels are protective against DOX insults and correlate with lower reactive oxygen species generation in cardiac cultures. Upstream of these mechanisms, we describe the transcription factor GATA-6 to be involved in mediating DOX-induced miR-30 down-regulation.
Finally, when assessing the implications of miR-30 in breast cancer, we observed an inverse correlation between miR-30 expression levels and breast cancer cell migration in vitro. Moreover, bioinformatic analyses revealed reduced miR-30 levels in breast cancer patients. Taken together, our findings encourage a potential translational use for miR-30 as an early biomarker as well as a therapeutic strategy, combining a cardioprotective action with pleiotropic anti-cancer effects.Open Acces
Long and short noncoding RNAs in the control of cancer stem cell traits
Get PDFNoncoding RNAs (ncRNAs) are now viewed as integral components of gene expression
networks in human cells, including cancerous ones. Investigating the precise roles they
play in varied cellular contexts has become a separate field within cancer research. In
pancreatic adenocarcinoma (PDAC), TGFβ signalling induces EMT and stemness, yet
the involvement of specific ncRNAs remains unknown. We identified two miRNAs,
miR-100 and -125b, to be substantially elevated following TGFβ stimulation, noting that
they derive from the same primary transcript. Modulating levels of miR-100 and -125b
decreases migration and pancsphere formation. Unexpectedly, miR-100 and -125b
appear to use different rules of miRNA-target base pairing, with an enrichment of
non-canonical miR-100 seed matches occurring in the CDS. Clinically, both miR-100
and -125b were elevated in a large PDAC dataset compared to normal tissue, with high
expression associated with lower patient survival.
In stark contrast to the persistently poor prognosis for PDAC patients, breast
cancer survival has improved markedly. Lethal properties of this disease, such as
chemoresistance and metastasis, have been linked to insufficiently characterised
minority breast cancer stem cell (BCSC) populations that may survive available
treatments to regenerate tumours, and can be migratory and invasive. Whether
ncRNAs play prominent roles in BCSC generation and behaviour is also largely
unresolved. Generating mammospheres to enrich for BCSCs, we found several long
noncoding RNAs (lncRNAs) to be differentially expressed compared to adherent cells.
Silencing three of these lncRNAs produced significant impacts on mammsphere
formation efficiency. We focused on Candidate 1, strongly upregulated in
mammospheres, yet unexpectedly increasing mammsphere formation when silenced.
Candidate 1 was chromatin-associated, correlated with chromatin-regulators in TCGA
data, and positively associated with survival. Candidate 1 silencing produced marked
transcriptomic changes when silenced, and bound strongly to the polyfunctional protein
HNRNP L, enabling us to speculate as to its potential mechanism of action.Open Acces
Identification of KSR1 as a novel target and decoding tyrosine kinase proteome in breast cancer
Get PDFKinase suppressor of Ras-1 (KSR1), originally identified as a novel protein kinase in the Ras-Raf cascade, plays a role in activation of mitogen-activated protein kinases (MAPKs). Although efforts have been devoted to study the role of KSR1 in certain tumour types, its biological functions in breast cancer have remained largely undefined.
A SILAC-based proteomic analysis was conducted to identify the KSR1-regulated phosphoproteins in breast cancer. Our results revealed that KSR1 overexpression decreases deleted in breast cancer 1 (DBC1) phosphorylation. We then demonstrated that KSR1 decreases transcriptional activity of p53 by reducing phosphorylation of DBC1, which leads to a reduced interaction of DBC1 with sirtuin 1 (SIRT1); this in turn enables SIRT1 to deacetylate p53. We further examined the correlation between KSR1 expression and clinical outcome in breast cancer. Our results showed that patients with breast cancer with high KSR1 in our cohort (n>1000) had better disease free- and overall survival. Moreover, in KSR1-transfected stable cells, fewer and smaller size colonies were formed in comparison to parental cells, while an in vivo study demonstrated that the growth of xenograft tumours overexpressing KSR1 was inhibited. Mechanistically, the tumour suppressive action of KSR1 is BRCA1 dependent,
which was shown by in vitro 3D matrigel and soft agar assays. KSR1 regulates BRCA1 ubiquitination through elevated BRCA1-associated RING domain 1 (BARD1) expression and increased BRCA1-BARD1 interaction.
Deregulation of tyrosine kinases (TKs) signalling can contribute to tumourigenesis. A combined approach of RNAi and SILAC-based quantitative proteomics was employed to decode the TKs-regulated proteomes upon silencing individually each 65 validated TKs in MCF7 breast cancer cells. Bioinformatics analysis identified 10 new distinctive clusters based on similarity in the TKs-regulated proteomes. The biological relevance of our proteomic study in interpreting the TKs-regulated proteomes supports the essential role of TKs in regulating
all aspects of cellular activities.Open Acces
Effect of pregnancy on the mutational landscape of normal human breast
Get PDFAbstract
The age at first-time pregnancy has been long recognised as a risk factor for breast cancer, but the mechanism underlying this have not been identified yet. By looking at the healthy breast, we hypothesise that both age and parity affect the mutational burden in the mammary epithelium, and the interplay between the two variables influences the probability of acquiring oncogenic mutations at different rates in the parous and nulliparous breast.
Whole-genome sequencing analysis from the laser-captured epithelial and stromal cells from 20 healthy parous (early and late) and nulliparous breast, revealed that the genomic landscape of the normal breast epithelium is characterised by a high number of somatic mutations (from 200,000 to 750,000 SNPs) and by the presence of mutations in breast cancer drivers (up to and average of 100 hits/gene). While the nulliparous breast is characterised by little variation in the mutational burden across the years, in the parous breast the burden increases with age, with comparable values to the nulliparous breast for the early parity group and significantly higher levels for older parity status. In particular, mutational hits in the driver genes are, irrespectively of age, significantly higher in the parous breast (p<0.005). The increase in mutation of the parous breast in the older age groups is linked to the presence of significant smaller clones, estimated on variant allele frequencies compared to nulliparous breast. This confirms that driver genes are already mutated in the healthy breast, and that the higher proliferation of the parous breast contributes to the higher probability of a mutated cancer clone to expand within the mammary epithelium.
The parous breast epithelium and stroma are characterised by the presence of significantly higher frequency of the 3’UTR variants and the start loss mutations. We propose that the disparity in the risk of developing BC between the groups could be because of the mutations in these regulatory regions. Further validation of these SNPs will allow us to elucidate the exact function of these SNPs, which will have an implication in understanding the disparity in the risk of breast cancer based on age and parity status.Open Acces
Variations on the Author
Get PDF“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
Get PDFWe 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
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