Publications by authors named "Kieran Brennan"

12 Publications

  • Page 1 of 1

Cyclophilin A regulates secretion of tumour-derived extracellular vesicles.

Transl Oncol 2021 Aug 10;14(8):101112. Epub 2021 May 10.

UCD School of Biomolecular & Biomedical Science, Conway Institute, University College Dublin (UCD), Belfield, Dublin 4, Ireland. Electronic address:

Extracellular Vesicles (EVs) are a heterogenous population of particles that play an important role in cell-cell communication in physiological and pathophysiological situations. In this study we reveal that the peptidyl prolyl isomerase Cyclophilin A (CypA) is enriched in cancer-derived EVs from a range of haematopoietic malignancies. CypA-enriched blood cancer EVs were taken up by normal monocytes independent of EV surface trypsin-sensitive proteins and potently stimulated pro-inflammatory MMP9 and IL-6 secretion. Further characterisation revealed that CypA is intravesicular, however, it is not present in all EVs derived from the haematopoietic cells, instead, it is predominantly located in high density EVs with a range of 1.15-1.18 g/ml. Furthermore, loss of CypA expression in haematological cancer cells attenuates high density EV-induced pro-inflammatory MMP9 and IL-6 secretion from monocytes. Mechanistically, we reveal that homozygous loss or siRNA knockdown of CypA expression significantly reduced the secretion of EVs in the range of 100-200 nm from blood cancer cells under normal and hypoxic conditions. Overall, this work reveals a novel role for CypA in cancer cell EV biogenesis.
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http://dx.doi.org/10.1016/j.tranon.2021.101112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8131927PMC
August 2021

Human Epidermal Growth Factor Receptor-3 Expression Is Regulated at Transcriptional Level in Breast Cancer Settings by Junctional Adhesion Molecule-A via a Pathway Involving Beta-Catenin and FOXA1.

Cancers (Basel) 2021 Feb 19;13(4). Epub 2021 Feb 19.

Department of Surgery, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland.

The success of breast cancer therapies targeting the human epidermal growth factor receptor-2 (HER2) is limited by the development of drug resistance by mechanisms including upregulation of HER3. Having reported that HER2 expression and resistance to HER2-targeted therapies can be regulated by Junctional Adhesion Molecule-A (JAM-A), this study investigated if JAM-A regulates HER3 expression. Expressional alteration of JAM-A in breast cancer cells was used to test expressional effects on HER3 and its effectors, alongside associated functional behaviors, in vitro and semi-in vivo. HER3 transcription factors were identified and tested for regulation by JAM-A. Finally a patient tissue microarray was used to interrogate connections between putative pathway components connecting JAM-A and HER3. This study reveals for the first time that HER3 and its effectors are regulated at gene/protein expression level by JAM-A in breast cancer cell lines; with functional consequences in in vitro and semi-in vivo models. In bioinformatic, cellular and patient tissue models, this was associated with regulation of the HER3 transcription factor FOXA1 by JAM-A via a pathway involving β-catenin. Our data suggest a novel model whereby JAM-A expression regulates β-catenin localization, in turn regulating FOXA1 expression, which could drive HER3 gene transcription. JAM-A merits investigation as a novel target to prevent upregulation of HER3 during the development of resistance to HER2-targeted therapies, or to reduce HER3-dependent tumorigenic signaling.
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http://dx.doi.org/10.3390/cancers13040871DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7922773PMC
February 2021

ADAM22/LGI1 complex as a new actionable target for breast cancer brain metastasis.

BMC Med 2020 11 19;18(1):349. Epub 2020 Nov 19.

Endocrine Oncology Research Group, Department of Surgery, Royal College of Surgeons in Ireland, Dublin 2, Ireland.

Background: Metastatic breast cancer is a major cause of cancer-related deaths in woman. Brain metastasis is a common and devastating site of relapse for several breast cancer molecular subtypes, including oestrogen receptor-positive disease, with life expectancy of less than a year. While efforts have been devoted to developing therapeutics for extra-cranial metastasis, drug penetration of blood-brain barrier (BBB) remains a major clinical challenge. Defining molecular alterations in breast cancer brain metastasis enables the identification of novel actionable targets.

Methods: Global transcriptomic analysis of matched primary and metastatic patient tumours (n = 35 patients, 70 tumour samples) identified a putative new actionable target for advanced breast cancer which was further validated in vivo and in breast cancer patient tumour tissue (n = 843 patients). A peptide mimetic of the target's natural ligand was designed in silico and its efficacy assessed in in vitro, ex vivo and in vivo models of breast cancer metastasis.

Results: Bioinformatic analysis of over-represented pathways in metastatic breast cancer identified ADAM22 as a top ranked member of the ECM-related druggable genome specific to brain metastases. ADAM22 was validated as an actionable target in in vitro, ex vivo and in patient tumour tissue (n = 843 patients). A peptide mimetic of the ADAM22 ligand LGI1, LGI1MIM, was designed in silico. The efficacy of LGI1MIM and its ability to penetrate the BBB were assessed in vitro, ex vivo and in brain metastasis BBB 3D biometric biohybrid models, respectively. Treatment with LGI1MIM in vivo inhibited disease progression, in particular the development of brain metastasis.

Conclusion: ADAM22 expression in advanced breast cancer supports development of breast cancer brain metastasis. Targeting ADAM22 with a peptide mimetic LGI1MIM represents a new therapeutic option to treat metastatic brain disease.
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http://dx.doi.org/10.1186/s12916-020-01806-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7677775PMC
November 2020

Classification of diffuse light emission profiles for distinguishing skin layer penetration of a needle-free jet injection.

Biomed Opt Express 2019 Oct 13;10(10):5081-5092. Epub 2019 Sep 13.

Auckland Bioengineering Institute, The University of Auckland, 70 Symonds Street, Auckland, New Zealand.

In this work, a system is developed for tracking the skin layer to which a needle-free jet injection of fluid has penetrated by incorporating a laser beam into the jet, and measuring the diffuse light emitted from skin tissue. Monitoring the injection in this way offers the ability to improve the reliability of drug delivery with this transdermal delivery method. A laser beam, axially aligned with a jet of fluid, created a distribution of diffuse light around the injection site that varied as the injection progressed. High-speed videography was used to capture the diffuse light emission from laser-coupled jet injections into samples of porcine skin, fat, and muscle. The injection produced a distribution of diffuse light around the injection site that varied as the injection descended. A classifier, trained to distinguish whether the light source was located in the fat or muscle from surface intensity profile measurements, correctly identified the injected layer in of the cases when cross-examined against estimates using the light distribution emitted from the side of the sample.
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http://dx.doi.org/10.1364/BOE.10.005081DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6788588PMC
October 2019

Spatially resolved diffuse imaging for high-speed depth estimation of jet injection.

J Biophotonics 2019 12 23;12(12):e201900205. Epub 2019 Oct 23.

Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.

We investigate the use of spatially resolved diffuse imaging to track a fluid jet delivered at high speed into skin tissue. A jet injector with a short needle to deliver drugs beneath the dermis, is modified to incorporate a laser beam into the jet, which is ejected into ex vivo porcine tissue. The diffuse light emitted from the side and top of the tissue sample is recorded using high-speed videography. Similar experiments, using a depth-controlled fiber optic source, generate a reference dataset. The side light distribution is related to source depth for the controlled-source experiments and used to track the effective source depth of the injections. Postinjection X-ray images show agreement between the jet penetration and ultimate light source depth. The surface light intensity profile is parameterized with a single parameter and an exponential function is used to relate this parameter to source depth for the controlled-source data. This empirical model is then used to estimate the effective source depth from the surface profile of the injection experiments. The depth estimates for injections into fat remain close to the side depth estimates, with a root-mean-square error of 1.1 mm, up to a source depth of 8 mm.
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http://dx.doi.org/10.1002/jbio.201900205DOI Listing
December 2019

High-speed X-ray analysis of liquid delivery during jet injection.

Annu Int Conf IEEE Eng Med Biol Soc 2017 Jul;2017:296-299

The effect of varying velocity during jet injection on the dispersion of fluid into tissue is investigated using a custom-built X-ray imaging system. Injections are performed into ex-vivo porcine abdominal tissue using a voice coil actuated injection device. Single velocity and two-phase velocity injections reveal the complex nature of the dispersion of the fluid jet in layered tissue and highlight the effects of changing the jet velocity following the initial penetration of the liquid into the tissue.
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http://dx.doi.org/10.1109/EMBC.2017.8036821DOI Listing
July 2017

Light source depth estimation in porcine skin using spatially resolved diffuse imaging.

Annu Int Conf IEEE Eng Med Biol Soc 2016 Aug;2016:5917-5920

We present an inexpensive imaging system for measuring the diffuse surface radiance profile produced by a light source within a turbid medium. The diffusion model of light propagation in multiple scattering media is used to estimate the optical properties of a sample and subsequently approximate the depth of an optical source. The system is shown to accurately estimate the relative changes in source depth in a homogeneous phantom. The absolute depth estimate may be improved with a better estimate of the optical parameters. Preliminary tests on a porcine skin sample show that the simple model can be used to roughly track the relative changes in the depth of a source in a layered medium. However, a rigorous model of the layered geometry may be required to more accurately localize a source, particularly near interfaces between tissue layers.
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http://dx.doi.org/10.1109/EMBC.2016.7592075DOI Listing
August 2016

Recessive NEK9 mutation causes a lethal skeletal dysplasia with evidence of cell cycle and ciliary defects.

Hum Mol Genet 2016 05 21;25(9):1824-35. Epub 2016 Feb 21.

Clinical Genetics, Children's University Hospital, Temple Street, Dublin 1, Ireland, UCD Academic Centre on Rare Diseases, School of Medicine and Medical Sciences.

Skeletal dysplasias are a clinically and genetically heterogeneous group of bone and cartilage disorders. Whilst >450 skeletal dysplasias have been reported, 30% are genetically uncharacterized. We report two Irish Traveller families with a previously undescribed lethal skeletal dysplasia characterized by fetal akinesia, shortening of all long bones, multiple contractures, rib anomalies, thoracic dysplasia, pulmonary hypoplasia and protruding abdomen. Single nucleotide polymorphism homozygosity mapping and whole exome sequencing identified a novel homozygous stop-gain mutation in NEK9 (c.1489C>T; p.Arg497*) as the cause of this disorder. NEK9 encodes a never in mitosis gene A-related kinase involved in regulating spindle organization, chromosome alignment, cytokinesis and cell cycle progression. This is the first disorder to be associated with NEK9 in humans. Analysis of NEK9 protein expression and localization in patient fibroblasts showed complete loss of full-length NEK9 (107 kDa). Functional characterization of patient fibroblasts showed a significant reduction in cell proliferation and a delay in cell cycle progression. We also provide evidence to support possible ciliary associations for NEK9. Firstly, patient fibroblasts displayed a significant reduction in cilia number and length. Secondly, we show that the NEK9 orthologue in Caenorhabditis elegans, nekl-1, is almost exclusively expressed in a subset of ciliated cells, a strong indicator of cilia-related functions. In summary, we report the clinical and molecular characterization of a lethal skeletal dysplasia caused by NEK9 mutation and suggest that this disorder may represent a novel ciliopathy.
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http://dx.doi.org/10.1093/hmg/ddw054DOI Listing
May 2016

Breast cancer cell migration is regulated through junctional adhesion molecule-A-mediated activation of Rap1 GTPase.

Breast Cancer Res 2011 Mar 23;13(2):R31. Epub 2011 Mar 23.

Department of Surgery, Royal College of Surgeons in Ireland, RCSI Education and Research Centre, Smurfit Building, Beaumont Hospital, Dublin 9, Ireland.

Introduction: The adhesion protein junctional adhesion molecule-A (JAM-A) regulates epithelial cell morphology and migration, and its over-expression has recently been linked with increased risk of metastasis in breast cancer patients. As cell migration is an early requirement for tumor metastasis, we sought to identify the JAM-A signalling events regulating migration in breast cancer cells.

Methods: MCF7 breast cancer cells (which express high endogenous levels of JAM-A) and primary cultures from breast cancer patients were used for this study. JAM-A was knocked down in MCF7 cells using siRNA to determine the consequences for cell adhesion, cell migration and the protein expression of various integrin subunits. As we had previously demonstrated a link between the expression of JAM-A and β1-integrin, we examined activation of the β1-integrin regulator Rap1 GTPase in response to JAM-A knockdown or functional antagonism. To test whether JAM-A, Rap1 and β1-integrin lie in a linear pathway, we tested functional inhibitors of all three proteins separately or together in migration assays. Finally we performed immunoprecipitations in MCF7 cells and primary breast cells to determine the binding partners connecting JAM-A to Rap1 activation.

Results: JAM-A knockdown in MCF7 breast cancer cells reduced adhesion to, and migration through, the β1-integrin substrate fibronectin. This was accompanied by reduced protein expression of β1-integrin and its binding partners αV- and α5-integrin. Rap1 activity was reduced in response to JAM-A knockdown or inhibition, and pharmacological inhibition of Rap1 reduced MCF7 cell migration. No additive anti-migratory effect was observed in response to simultaneous inhibition of JAM-A, Rap1 and β1-integrin, suggesting that they lie in a linear migratory pathway. Finally, in an attempt to elucidate the binding partners putatively linking JAM-A to Rap1 activation, we have demonstrated the formation of a complex between JAM-A, AF-6 and the Rap1 activator PDZ-GEF2 in MCF7 cells and in primary cultures from breast cancer patients.

Conclusions: Our findings provide compelling evidence of a novel role for JAM-A in driving breast cancer cell migration via activation of Rap1 GTPase and β1-integrin. We speculate that JAM-A over-expression in some breast cancer patients may represent a novel therapeutic target to reduce the likelihood of metastasis.
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http://dx.doi.org/10.1186/bcr2853DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3219194PMC
March 2011

Tight junctions: a barrier to the initiation and progression of breast cancer?

J Biomed Biotechnol 2010 15;2010:460607. Epub 2009 Nov 15.

Department of Surgery, Royal College of Surgeons in Ireland, Dublin, Ireland.

Breast cancer is a complex and heterogeneous disease that arises from epithelial cells lining the breast ducts and lobules. Correct adhesion between adjacent epithelial cells is important in determining the normal structure and function of epithelial tissues, and there is accumulating evidence that dysregulated cell-cell adhesion is associated with many cancers. This review will focus on one cell-cell adhesion complex, the tight junction (TJ), and summarize recent evidence that TJs may participate in breast cancer development or progression. We will first outline the protein composition of TJs and discuss the functions of the TJ complex. Secondly we will examine how alterations in these functions might facilitate breast cancer initiation or progression; by focussing on the regulatory influence of TJs on cell polarity, cell fate and cell migration. Finally we will outline how pharmacological targeting of TJ proteins may be useful in limiting breast cancer progression. Overall we hope to illustrate that the relationship between TJ alterations and breast cancer is a complex one; but that this area offers promise in uncovering fundamental mechanisms linked to breast cancer progression.
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http://dx.doi.org/10.1155/2010/460607DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2777242PMC
January 2010

Clinical response of two brush-applied peroxide whitening systems.

J Clin Dent 2003 ;14(3):59-63

Procter & Gamble Company, Mason, OH, USA.

Objective: A randomized, examiner-blind parallel design study was conducted to evaluate the clinical efficacy and tolerability of two brush-applied, peroxide-based tooth whiteners.

Methodology: A total of 38 subjects were randomized to Colgate Simply White, an 18% carbamide peroxide paint-on liquid in an applicator bottle, or Crest Night Effects, a 19% sodium percarbonate system in unit dose sachets that dries to form an adherent film. Treatment was for 14 days. The 18% carbamide peroxide gel was applied twice daily, while the 19% sodium percarbonate film was applied for overnight use. Subjects were evaluated at baseline, and again after 7 and 14 days of treatment using digital images to assess tooth color, and oral examinations to establish safety. Whitening efficacy was determined by evaluating the reduction in tooth yellowness (delta b*), increase in tooth brightness (delta L*), reduction in tooth redness (delta a*) and overall tooth color change relative to pure white (delta W*).

Results: After 14 days, the mean change in yellowness (delta b*) was -1.43 +/- 0.20 for the 19% sodium percarbonate film, and -0.44 +/- 0.06 for the 18% carbamide peroxide gel. Mean change in brightness (delta L*) was 1.13 +/- 0.13 and 0.55 +/- 0.13 in the film and gel groups, respectively. Between-group comparisons showed highly significant (p < or = 0.003) whitening for the 19% sodium percarbonate film compared to the 18% carbamide peroxide gel for all 14-day color measurements (delta b*, delta L*, delta a* or delta W). Both products were well-tolerated, with no subjects discontinuing treatment early due to a causal adverse event.

Conclusion: In a direct clinical comparison of two brush-applied products over 14 days, Crest Night Effects provided significant and meaningful improvement in tooth color, representing more than double the whitening measured for the Colgate Simply White.
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December 2003

Experimental gingivitis studies: effects of triclosan and triclosan-containing dentifrices on dental plaque and gingivitis in three-week randomized controlled clinical trials.

J Clin Dent 2002 ;13(4):158-66

School of Dental Medicine, University of Berne, Switzerland.

A recently reported six-month gingivitis study demonstrated that in subjects with gingivitis, a triclosan/pyrophosphate dentifrice provided supragingival plaque control. The level of plaque reduction was comparable with that reported for other triclosan-containing dentifrices; however, no reductions in gingivitis were observed for triclosan/pyrophosphate relative to the negative control. One possible explanation of this result is that the Hawthorne effect in the study was too great to allow the detection of a treatment benefit for the triclosan product. In order to further explore the relevance of these results, three independent clinical studies were undertaken utilizing designs based on a 21-day experimental gingivitis model in which Hawthorne effects are minimized, in part due to the absence of toothbrushing. In each model, a pre-study prophylaxis was followed by a three-week period of oral hygiene instruction to establish optimum baseline gingival health in study participants. The studies varied in enrollment; 120, 33 and 32 subjects completed treatment on studies 1, 2, and 3, respectively. In study 1, test articles were dentifrice products (0.28% triclosan/5% pyrophosphate/0.145% sodium fluoride, 0.2% triclosan/0.5% zinc citrate/0.112% sodium fluoride, 0.145% sodium fluoride and 0.15% sodium monofluorophosphate) applied neat and undiluted via a performed tooth shield (that prevents mechanical tooth-brushing at the test sites in the oral cavity) in a partial mouth design. In study 2, test articles were also dentifrice products (0.28% triclosan/5% pyrophosphate/0.243% sodium fluoride, 0.3% triclosan/2% Gantrez copolymer/0.24% sodium fluoride and 0.243% sodium fluoride) but administered to subjects in the form of 1:3 aqueous slurry rinses. Lastly, in study 3, test articles were all mouthrinses (0.12% chlorhexidine, 0.045% triclosan in ethanol plus respective vehicle placebos). Clinical assessments to quantify the test articles' effects on the development of plaque and gingivitis were conducted at baseline (studies 1, 2 and 3), day 7 (studies 2 and 3), day 14 (studies 2 and 3) and day 21 (studies 1, 2 and 3). In study 1, no statistically significant treatment effects were observed between the test articles and controls for plaque or gingivitis development. In study 2, no statistically significant treatment effects were observed at any time point between test products for the development of gingivitis. At days 7 and 14, there were no significant differences between test products and control for plaque development as well. At day 21, the group rinsing with the triclosan/pyrophosphate/sodium fluoride slurry had significantly less plaque accumulation than the group rinsing with the triclosan/copolymer/sodium fluoride slurry (p < 0.05); however, neither of the groups using test products containing triclosan was significantly different for plaque development from the group using the sodium fluoride control test article. In addition, aspartate aminotransferase activity in gingival crevicular fluid was assayed at days 0 and 21; no between-group differences were found at either of these time points, though day 21 AST activities were higher than those at baseline. In study 3, statistically significant treatment differences in plaque regrowth and gingivitis were observed at day 21 for the chlorhexidine rinse versus all other rinses (p < 0.05). No other statistically significant treatment effects were observed between test compounds at any other time points. The results benchmark the anti-plaque and anti-gingivitis benefit for a range of triclosan-based product forms against positive and negative controls in a three different experimental gingivitis models, a design considered predictive of clinical efficacy in longer-term investigations. It is concluded that dentifrice products containing triclosan do not possess sufficient antimicrobial activity to suppress plaque and gingivitis development in the absence of normal oral hygiene, and that relative to chlorhexidine, triclosan itself offers only modest efficacy for the prevention of plaque accumulation and therefore the delayed onset of gingivitis.
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September 2002
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