ORCID Profile
0000-0002-1831-4804
Current Organisations
University of Western Australia
,
The Harry Perkins Institute of Medical Research
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Publisher: Elsevier BV
Date: 02-2009
Publisher: American Association for Cancer Research (AACR)
Date: 11-2013
DOI: 10.1158/1535-7163.MCT-13-0170
Abstract: Elevated expression and activity of the epidermal growth factor receptor (EGFR) is associated with development and progression of head and neck cancer (HNC) and a poor prognosis. Clinical trials with EGFR tyrosine kinase inhibitors (e.g., erlotinib) have been disappointing in HNC. To investigate the mechanisms mediating resistance to these agents, we developed an HNC cell line (HN5-ER) with acquired erlotinib resistance. In contrast to parental HN5 HNC cells, HN5-ER cells exhibited an epithelial–mesenchymal (EMT) phenotype with increased migratory potential, reduced E-cadherin and epithelial-associated microRNAs (miRNA), and elevated vimentin expression. Phosphorylated receptor tyrosine kinase profiling identified Axl activation in HN5-ER cells. Growth and migration of HN5-ER cells were blocked with a specific Axl inhibitor, R428, and R428 resensitized HN5-ER cells to erlotinib. Microarray analysis of HN5-ER cells confirmed the EMT phenotype associated with acquired erlotinib resistance, and identified activation of gene expression associated with cell migration and inflammation pathways. Moreover, increased expression and secretion of interleukin (IL)-6 and IL-8 in HN5-ER cells suggested a role for inflammatory cytokine signaling in EMT and erlotinib resistance. Expression of the tumor suppressor miR-34a was reduced in HN5-ER cells and increasing its expression abrogated Axl expression and reversed erlotinib resistance. Finally, analysis of 302 HNC patients revealed that high tumor Axl mRNA expression was associated with poorer survival (HR = 1.66, P = 0.007). In summary, our results identify Axl as a key mediator of acquired erlotinib resistance in HNC and suggest that therapeutic inhibition of Axl by small molecule drugs or specific miRNAs might overcome anti-EGFR therapy resistance. Mol Cancer Ther 12(11) 2541–58. ©2013 AACR.
Publisher: Elsevier BV
Date: 2012
DOI: 10.1016/J.BBRC.2012.11.086
Abstract: Aberrant expression of microRNAs (miRNAs), a class of small non-coding regulatory RNAs, has been implicated in the development and progression of melanoma. However, the precise mechanistic role of many of these miRNAs remains unclear. We have investigated the functional role of miR-7-5p in melanoma, and demonstrate that miR-7-5p expression is reduced in metastatic melanoma-derived cell lines compared with primary melanoma cells, and that when ectopically expressed miR-7-5p significantly inhibits melanoma cell migration and invasion. Additionally, we report that insulin receptor substrate-2 (IRS-2) is a target of miR-7-5p in melanoma cells, and using RNA interference (RNAi) we provide evidence that IRS-2 activates protein kinase B (Akt), and promotes melanoma cell migration. Thus, miR-7-5p may represent a novel tumor suppressor miRNA in melanoma, acting at least in part via its inhibition of IRS-2 expression and oncogenic Akt signaling.
Publisher: Elsevier BV
Date: 07-2020
Publisher: Springer Science and Business Media LLC
Date: 29-04-2023
DOI: 10.1186/S13148-023-01482-0
Abstract: Epigenetic silencing of tumor suppressor genes (TSGs) is a key feature of oncogenesis in hepatocellular carcinoma (HCC). Liver-targeted delivery of CRISPR-activation (CRISPRa) systems makes it possible to exploit chromatin plasticity, by reprogramming transcriptional dysregulation. Using The Cancer Genome Atlas HCC data, we identify 12 putative TSGs with negative associations between promoter DNA methylation and transcript abundance, with limited genetic alterations. All HCC s les harbor at least one silenced TSG, suggesting that combining a specific panel of genomic targets could maximize efficacy, and potentially improve outcomes as a personalized treatment strategy for HCC patients. Unlike epigenetic modifying drugs lacking locus selectivity, CRISPRa systems enable potent and precise reactivation of at least 4 TSGs tailored to representative HCC lines. Concerted reactivation of HHIP , MT1M , PZP , and TTC36 in Hep3B cells inhibits multiple facets of HCC pathogenesis, such as cell viability, proliferation, and migration. By combining multiple effector domains, we demonstrate the utility of a CRISPRa toolbox of epigenetic effectors and gRNAs for patient-specific treatment of aggressive HCC.
Publisher: Springer Science and Business Media LLC
Date: 09-09-2021
DOI: 10.1038/S41598-021-97190-X
Abstract: RNA-based therapeutics are emerging as innovative options for cancer treatment, with microRNAs being attractive targets for therapy development. We previously implicated microRNA-642a-5p (miR-642a-5p) as a tumor suppressor in prostate cancer (PCa), and here we characterize its mode of action, using 22Rv1 PCa cells. In an in vivo xenograft tumor model, miR-642a-5p induced a significant decrease in tumor growth, compared to negative control. Using RNA-Sequencing, we identified gene targets of miR-642a-5p which were enriched for gene sets controlling cell cycle downregulated genes included Wilms Tumor 1 gene (WT1), NUAK1, RASSF3 and SKP2 and upregulated genes included IGFBP3 and GPS2. Analysis of PCa patient datasets showed a higher expression of WT1, NUAK1, RASSF3 and SKP2 and a lower expression of GPS2 and IGFBP3 in PCa tissue compared to non-malignant prostate tissue. We confirmed the prostatic oncogene WT1, as a direct target of miR-642a-5p, and treatment of 22Rv1 and LNCaP PCa cells with WT1 siRNA or a small molecule inhibitor of WT1 reduced cell proliferation. Taken together, these data provide insight into the molecular mechanisms by which miR-642a-5p acts as a tumor suppressor in PCa, an effect partially mediated by regulating genes involved in cell cycle control and restoration of miR-642-5p in PCa could represent a novel therapeutic approach.
Publisher: Springer Science and Business Media LLC
Date: 16-03-2018
Publisher: Public Library of Science (PLoS)
Date: 30-04-2018
Publisher: Elsevier BV
Date: 12-2012
Publisher: Springer New York
Date: 31-10-2018
DOI: 10.1007/978-1-4939-7435-1_12
Abstract: MicroRNAs (miRNAs) are a family of short noncoding RNA molecules that fine-tune expression of mRNAs. Often their altered expression is associated with a number of diseases, including cancer. Given that miRNAs target multiple genes and "difficult to drug" oncogenes, they present attractive candidates to manipulate as an anti-cancer strategy. MicroRNA-7 (miR-7) is a tumor suppressor miRNA that has been shown to target oncogenes overexpressed in cancers, such as the epidermal growth factor receptor (EGFR) and the nuclear factor-κ B subunit, RelA. Here, we describe methods for evaluating systemic delivery of miR-7 using a lipid nanoparticle formulation in an animal model. The microRNA is delivered three times, over 1 week and tissues collected 24 h after the last injection. RNA and protein are extracted from snap frozen tissues and processed to detect miRNA distribution and subsequent assessment of downstream targets and signaling mediators, respectively. Importantly, variability in efficiency of miRNA delivery will be observed between organs of the same animal and also between animals. Additionally, delivering the microRNA to organs other than the liver, particularly the brain, remains challenging. Furthermore, large variation in miRNA targets is seen both within tissues and across tissues depending on the lysis buffer used for protein extraction. Therefore, analyzing protein expression is dependent upon the method used for isolation and requires optimization for each in idual application. Together, these methods will provide a foundation for those planning on assessing the efficacy of delivery of a miRNA in vivo.
Publisher: Elsevier BV
Date: 09-2014
DOI: 10.1016/J.BIOCEL.2014.05.040
Abstract: microRNAs are a family of endogenous, short, non-coding RNAs that play critical roles in regulating gene expression for key cellular processes in normal and abnormal physiology. microRNA-7 is a 23 nucleotide miRNA whose expression is tightly regulated and restricted predominantly to the brain, spleen and pancreas. Reduced levels of miR-7 have been linked to the development of cancer and metastasis. As a tumor suppressor, miR-7 functions to co-ordinately downregulate a number of direct (e.g. the epidermal growth factor receptor) and indirect (e.g. phospho-Akt) growth promoting targets to decrease tumor growth in vitro and in vivo. In addition, miR-7 can increase the sensitivity of treatment-resistant cancer cells to therapeutics and inhibit metastasis. These data suggest that replacement of miR-7 ('miRNA replacement therapy') for specific human cancers could represent a new treatment approach. This article is part of a Directed Issue entitled: The Non-coding RNA Revolution.
Publisher: Elsevier BV
Date: 10-2012
Publisher: Impact Journals, LLC
Date: 17-05-2016
Publisher: American Society of Hematology
Date: 27-08-2019
DOI: 10.1182/BLOODADVANCES.2018030551
Abstract: Erythroid maturation requires the concerted action of a core set of transcription factors. We previously identified the Krüppel-type zinc finger transcription factor Zfp148 (also called ZBP-89) as an interacting partner of the master erythroid transcription factor GATA1. Here we report the conditional knockout of Zfp148 in mice. Global loss of Zfp148 results in perinatal lethality from nonhematologic causes. Selective Zfp148 loss within the hematopoietic system results in a mild microcytic and hypochromic anemia, mildly impaired erythroid maturation, and delayed recovery from phenylhydrazine-induced hemolysis. Based on the mild erythroid phenotype of these mice compared with GATA1-deficient mice, we hypothesized that additional factor(s) may complement Zfp148 function during erythropoiesis. We show that Zfp281 (also called ZBP-99), another member of the Zfp148 transcription factor family, is highly expressed in murine and human erythroid cells. Zfp281 knockdown by itself results in partial erythroid defects. However, combined deficiency of Zfp148 and Zfp281 causes a marked erythroid maturation block. Zfp281 physically associates with GATA1, occupies many common chromatin sites with GATA1 and Zfp148, and regulates a common set of genes required for erythroid cell differentiation. These findings uncover a previously unknown role for Zfp281 in erythroid development and suggest that it functionally overlaps with that of Zfp148 during erythropoiesis.
Publisher: Frontiers Media SA
Date: 22-02-2022
Abstract: Improving tumor access for drug delivery is challenging, particularly in poorly perfused tumors. The availability of functional tumor blood vessels for systemic access is vital to allow drugs or imaging agents to accumulate in the tumor parenchyma. We subjected mice engineered to develop hepatocellular carcinoma (HCC), to treatment with tumor necrosis factor alpha (TNFα) conjugated to a CSG peptide (CSGRRSSKC). CSG binds to the laminin-nidogen-1 complex of the extracellular matrix (ECM) in HCC. When produced as a recombinant fusion protein, the TNFα-CSG functions as an ECM depletion agent via an immune-mediated mechanism to improve tumor perfusion. Tumor perfusion in HCC was dramatically improved after daily intravenous (i.v.) injection of 5 µg TNFα-CSG for five consecutive days. Following treatment, we assessed the tumor accessibility to accumulate an imaging agent, superparamagnetic iron-oxide nanoparticles (IO-NP). Here, we compared the passive delivery of an i.v. dose of IO-NP in HCC following ECM depletion after TNFα-CSG treatment, to the intratumoral accumulation of a comparable dose of CSG-targeted IO-NP in HCC with intact ECM. Magnetic resonance imaging (MRI) T 2 -weighted scans and T 2 relaxation times indicate that when the tumor ECM is intact, HCC was resistant to the intratumoral uptake of IO-NP, even when the particles were tagged with CSG peptide. In contrast, pre-treatment with TNFα-CSG resulted in the highest IO-NP accumulation in tumors. These findings suggest poorly perfused HCC may be resistant to molecular-targeted imaging agents including CSG-IO-NP. We demonstrate that specific ECM depletion using TNFα-CSG improves nanoparticle delivery into poorly perfused tumors such as HCC.
Publisher: Springer Science and Business Media LLC
Date: 04-06-2019
DOI: 10.1007/S00018-019-03163-9
Abstract: RNA-binding proteins (RBPs) and microRNAs (miRNAs) are the most important regulators of mRNA stability and translation in eukaryotic cells however, the complex interplay between these systems is only now coming to light. RBPs and miRNAs regulate a unique set of targets in either a positive or negative manner and their regulation is mainly opposed to each other on overlapping targets. In some cases, the levels of RBPs or miRNAs regulate the cellular levels of one another and decreased levels of either results in changes in translation of their targets. There is growing evidence that these regulatory circuits are crucial in the development and progression of cancer however, the rules underlying synergism and antagonism between miRNAs and RNA-binding proteins remain unclear. Synthetic biology seeks to develop artificial systems to better understand their natural counterparts and to develop new, useful technologies for manipulation of gene expression at the RNA level. The recent development of artificial RNA-binding proteins promises to enable a much greater understanding of the importance of the functional interactions between RNA-binding proteins and miRNAs, as well as enabling their manipulation for therapeutic purposes.
Publisher: Springer Science and Business Media LLC
Date: 07-10-2022
DOI: 10.1038/S41389-022-00435-1
Abstract: The MYC proto-oncogene ( MYC ) is one of the most frequently overexpressed genes in breast cancer that drives cancer stem cell-like traits, resulting in aggressive disease progression and poor prognosis. In this study, we identified zinc finger transcription factor 148 ( ZNF148 , also called Zfp148 and ZBP-89) as a direct target of MYC. ZNF148 suppressed cell proliferation and migration and was transcriptionally repressed by MYC in breast cancer. Depletion of ZNF148 by short hairpin RNA (shRNA) and CRISPR/Cas9 increased triple-negative breast cancer (TNBC) cell proliferation and migration. Global transcriptome and chromatin occupancy analyses of ZNF148 revealed a central role in inhibiting cancer cell de-differentiation and migration. Mechanistically, we identified the Inhibitor of DNA binding 1 and 3 ( ID1, ID3 ), drivers of cancer stemness and plasticity, as previously uncharacterized targets of transcriptional repression by ZNF148. Silencing of ZNF148 increased the stemness and tumorigenicity in TNBC cells. These findings uncover a previously unknown tumor suppressor role for ZNF148, and a transcriptional regulatory circuitry encompassing MYC, ZNF148, and ID1/3 in driving cancer stem cell traits in aggressive breast cancer.
Publisher: MDPI AG
Date: 25-08-2015
DOI: 10.3390/JCM4091668
Publisher: Humana Press
Date: 28-08-2010
DOI: 10.1007/978-1-60761-863-8_11
Abstract: Aberrant expression of the epidermal growth factor receptor (EGFR) and/or human epidermal growth factor receptor 2 (HER2) is a feature of many human tumors and is associated with disease progression, treatment resistance, and poor prognosis. Protein kinase B/Akt, an important downstream effector of these receptor tyrosine kinases, induces signaling pathways that control cancer cell proliferation, invasion, angiogenesis, and apoptosis resistance. MicroRNAs (miRNAs), small noncoding RNAs that bind to the 3'-untranslated region of target mRNAs, are now recognized to play key roles in the regulation of gene expression, particularly in tumor development and metastasis. We have shown that miRNA-7 (miR-7) and miRNA-331-3p (miR-331-3p) directly regulate expression of EGFR and HER2, respectively, in glioblastoma and prostate cancer cell lines. As a consequence, miR-7 and miR-331-3p reduce Akt activity and thus have the capacity to regulate a signaling pathway critical to the development and progression of glioblastoma and prostate cancer. This chapter provides a detailed approach outlining how to confirm that a putative target of a miRNA is a direct target, and subsequent assessment of downstream signaling mediators.
Publisher: Impact Journals, LLC
Date: 27-06-2017
Publisher: Elsevier BV
Date: 12-2011
Publisher: Frontiers Media SA
Date: 09-04-2020
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 29-11-2018
DOI: 10.1002/HEP.29478
Abstract: Sorafenib remains the only approved drug for treating patients with advanced hepatocellular carcinoma (HCC). However, the therapeutic effect of sorafenib is transient, and patients invariably develop sorafenib resistance (SR). Recently, TYRO3, a member of the TYRO3‐AXL‐MER family of receptor tyrosine kinases, was identified as being aberrantly expressed in a significant proportion of HCC however, its role in SR is unknown. In this study, we generated two functionally distinct sorafenib‐resistant human Huh‐7 HCC cell lines in order to identify new mechanisms to abrogate acquired SR as well as new potential therapeutic targets in HCC. Initially, we investigated the effects of a microRNA (miR), miR‐7‐5p (miR‐7), in both in vitro and in vivo preclinical models of human HCC and identified miR‐7 as a potent tumor suppressor of human HCC. We identified TYRO3 as a new functional target of miR‐7, which regulates proliferation, migration, and invasion of Huh‐7 cells through the phosphoinositide 3‐kinase rotein kinase B pathway and is markedly elevated with acquisition of SR. Furthermore, miR‐7 effectively silenced TYRO3 expression in both sorafenib‐sensitive and sorafenib‐resistant Huh‐7 cells, inhibiting TYRO3/growth arrest specific 6‐mediated cancer cell migration and invasion. Conclusion : We identified a mechanism for acquiring SR in HCC that is through the aberrant expression of the TYRO3 hosphoinositide 3‐kinase rotein kinase B signal transduction pathway, and that can be overcome by miR‐7 overexpression. Taken together, these data suggest a potential role for miR‐7 as an RNA‐based therapeutic to treat refractory and drug‐resistant HCC. (H epatology 2018 :216‐231)
Publisher: Wiley
Date: 30-08-2018
DOI: 10.1002/JCB.27446
Abstract: Expression of the transcriptional regulator, E26 transformation‐specific 1 (ETS1), is elevated in human prostate cancers, and this is associated with more aggressive tumor behavior and a rapid progression to castrate‐resistant disease. Multiple ETS1 isoforms with distinct biological activities have been characterized and in 44 matched nonmalignant and malignant human prostate specimens, messenger RNAs for two ETS1 isoforms, ETS1p51 and ETS1p42 , were detected, with ETS1p51 levels significantly lower in prostate tumor compared to matched nonmalignant prostate tissues. In contrast, ETS1p51 protein, the only ETS1 isoform detected, was expressed at significantly higher levels in malignant prostate. Analysis of epithelial‐to‐mesenchymal transition (EMT)–associated genes regulated following overexpression of ETS1p51 in the LNCaP prostate cancer cell line predicted promotion of transforming growth factor β (TGFβ) signaling and of EMT. ETS1p51 overexpression upregulated cellular levels of the EMT transcriptional regulators, ZEB1 and SNAIL1, resulted in reduced expression of the mesenchymal marker vimentin with concomitantly elevated levels of claudin 1, an epithelial tight junction protein, and increased prostate cancer cell migration and invasion. ETS1p51‐induced activation of the pro‐EMT TGFβ signaling pathway that was predicted in polymerase chain reaction arrays was verified by demonstration of elevated SMAD2 phosphorylation following ETS1p51 overexpression. Attenuation of ETS1p51 effects on prostate cancer cell migration and invasion by inhibition of TGFβ pathway signaling indicated that ETS1p51 effects were in part mediated by induction of TGFβ signaling. Thus, overexpression of ETS1p51, the predominant ETS1 isoform expressed in prostate tumors, promotes an EMT program in prostate cancer cells in part via activation of TGFβ signaling, potentially accounting for the poor prognosis of ETS1‐overexpressing prostate tumors.
Publisher: Public Library of Science (PLoS)
Date: 24-10-2012
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.BIOCEL.2015.11.001
Abstract: MicroRNAs (miRNAs) are a family of short, non-coding RNA molecules (∼22nt) involved in post-transcriptional control of gene expression. They act via base-pairing with mRNA transcripts that harbour target sequences, resulting in accelerated mRNA decay and/or translational attenuation. Given miRNAs mediate the expression of molecules involved in many aspects of normal cell development and functioning, it is not surprising that aberrant miRNA expression is closely associated with many human diseases. Their pivotal role in driving a range of normal cellular physiology as well as pathological processes has established miRNAs as potential therapeutics, as well as potential diagnostic and prognostic tools in human health. MicroRNA-7 (miR-7) is a highly conserved miRNA which displays restricted spatiotemporal expression during development and in maturity. In humans and mice, mature miR-7 is generated from three different genes, illustrating unexpected redundancy and also the importance of this miRNA in regulating key cellular processes. In this review we examine the expanding role of miR-7 in the context of health, with emphasis on organ differentiation and development, as well as in various mammalian diseases, particularly of the brain, heart, endocrine pancreas and skin, as well as in cancer. The more we learn about miR-7, the more we realise the complexity of its regulation and potential functional application both from a biomarker and therapeutic perspective.
No related grants have been discovered for Peter Leedman.