Pearl Lee
University of Leicester
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Publication
Featured researches published by Pearl Lee.
Developmental Cell | 2013
Eric C. Cheung; Dimitris Athineos; Pearl Lee; Rachel A. Ridgway; Wendy Lambie; Colin Nixon; Douglas Strathdee; Karen Blyth; Owen J. Sansom; Karen H. Vousden
Summary Regulation of metabolic pathways plays an important role in controlling cell growth, proliferation, and survival. TIGAR acts as a fructose-2,6-bisphosphatase, potentially promoting the pentose phosphate pathway to produce NADPH for antioxidant function and ribose-5-phosphate for nucleotide synthesis. The functions of TIGAR were dispensable for normal growth and development in mice but played a key role in allowing intestinal regeneration in vivo and in ex vivo cultures, where growth defects due to lack of TIGAR were rescued by ROS scavengers and nucleosides. In a mouse intestinal adenoma model, TIGAR deficiency decreased tumor burden and increased survival, while elevated expression of TIGAR in human colon tumors suggested that deregulated TIGAR supports cancer progression. Our study demonstrates the importance of TIGAR in regulating metabolism for regeneration and cancer development and identifies TIGAR as a potential therapeutic target in diseases such as ulcerative colitis and intestinal cancer.
Genes & Development | 2012
Catherine Andreadi; Lai-Kay Cheung; Susan Giblett; Bipin Patel; Hong Jin; Kathryn Mercer; Tamihiro Kamata; Pearl Lee; Alexander G. Williams; Martin McMahon; Richard Marais; Catrin Pritchard
(L597V)BRAF mutations are acquired somatically in human cancer samples and are frequently coincident with RAS mutations. Germline (L597V)BRAF mutations are also found in several autosomal dominant developmental conditions known as RASopathies, raising the important question of how the same mutation can contribute to both pathologies. Using a conditional knock-in mouse model, we show that endogenous expression of (L597V)Braf leads to approximately twofold elevated Braf kinase activity and weak activation of the Mek/Erk pathway. This is associated with induction of RASopathy hallmarks including cardiac abnormalities and facial dysmorphia but is not sufficient for tumor formation. We combined (L597V)Braf with (G12D)Kras and found that (L597V)Braf modified (G12D)Kras oncogenesis such that fibroblast transformation and lung tumor development were more reminiscent of that driven by the high-activity (V600E)Braf mutant. Mek/Erk activation levels were comparable with those driven by (V600E)Braf in the double-mutant cells, and the gene expression signature was more similar to that induced by (V600E)Braf than (G12D)Kras. However, unlike (V600E)Braf, Mek/Erk pathway activation was mediated by both Craf and Braf, and ATP-competitive RAF inhibitors induced paradoxical Mek/Erk pathway activation. Our data show that weak activation of the Mek/Erk pathway underpins RASopathies, but in cancer, (L597V)Braf epistatically modifies the transforming effects of driver oncogenes.
Cancer and Metabolism | 2014
Pearl Lee; Karen H. Vousden; Eric C. Cheung
Cancers cells shift their metabolism towards glycolysis in order to help them support the biosynthetic demands necessary to sustain cell proliferation and growth, adapt to stress and avoid excessive reactive oxygen species (ROS) accumulation. While the p53 tumor suppressor protein is known to inhibit cell growth by inducing apoptosis, senescence and cell cycle arrest, recent studies have found that p53 is also able to influence cell metabolism. TIGAR is a p53 target that functions as a fructose-2,6-bisphosphatase, thereby lowering glycolytic flux and promoting antioxidant functions. By protecting cells from oxidative stress, TIGAR may mediate some of the tumor suppressor activity of p53 but could also contribute to tumorigenesis. Here we discuss the activities of TIGAR described so far, and the potential consequences of TIGAR expression on normal and tumor cells.
Nature | 2017
Oliver D.K. Maddocks; Dimitris Athineos; Eric C. Cheung; Pearl Lee; Tong Zhang; Niels J. F. van den Broek; Gillian M. Mackay; Christiaan F. Labuschagne; Flore Kruiswijk; Julianna Blagih; David F. Vincent; Kirsteen J. Campbell; Fatih Ceteci; Owen J. Sansom; Karen Blyth; Karen H. Vousden
The non-essential amino acids serine and glycine are used in multiple anabolic processes that support cancer cell growth and proliferation (reviewed in ref. 1). While some cancer cells upregulate de novo serine synthesis, many others rely on exogenous serine for optimal growth. Restriction of dietary serine and glycine can reduce tumour growth in xenograft and allograft models. Here we show that this observation translates into more clinically relevant autochthonous tumours in genetically engineered mouse models of intestinal cancer (driven by Apc inactivation) or lymphoma (driven by Myc activation). The increased survival following dietary restriction of serine and glycine in these models was further improved by antagonizing the anti-oxidant response. Disruption of mitochondrial oxidative phosphorylation (using biguanides) led to a complex response that could improve or impede the anti-tumour effect of serine and glycine starvation. Notably, Kras-driven mouse models of pancreatic and intestinal cancers were less responsive to depletion of serine and glycine, reflecting an ability of activated Kras to increase the expression of enzymes that are part of the serine synthesis pathway and thus promote de novo serine synthesis.
Genes & Development | 2016
Eric C. Cheung; Pearl Lee; Fatih Ceteci; Colin Nixon; Karen Blyth; Owen J. Sansom; Karen H. Vousden
Reactive oxygen species (ROS) participate in numerous cell responses, including proliferation, DNA damage, and cell death. Based on these disparate activities, both promotion and inhibition of ROS have been proposed for cancer therapy. However, how the ROS response is determined is not clear. We examined the activities of ROS in a model of Apc deletion, where loss of the Wnt target gene Myc both rescues APC loss and prevents ROS accumulation. Following APC loss, Myc has been shown to up-regulate RAC1 to promote proliferative ROS through NADPH oxidase (NOX). However, APC loss also increased the expression of TIGAR, which functions to limit ROS. To explore this paradox, we used three-dimensional (3D) cultures and in vivo models to show that deletion of TIGAR increased ROS damage and inhibited proliferation. These responses were suppressed by limiting damaging ROS but enhanced by lowering proproliferative NOX-derived ROS. Despite having opposing effects on ROS levels, loss of TIGAR and RAC1 cooperated to suppress intestinal proliferation following APC loss. Our results indicate that the pro- and anti-proliferative effects of ROS can be independently modulated in the same cell, with two key targets in the Wnt pathway functioning to integrate the different ROS signals for optimal cell proliferation.
Cell Cycle | 2014
Andreas K. Hock; Pearl Lee; Oliver Dk Maddocks; Susan M. Mason; Karen Blyth; Karen H. Vousden
GFP and luciferase are used extensively as markers both in vitro and in vivo although both have limitations. The utility of GFP fluorescence is restricted by high background signal and poor tissue penetrance. Luciferase throughput is limited in vitro by the requirement for cell lysis, while in vivo, luciferase readout is complicated by the need for substrate injection and the dependence on endogenous ATP. Here we show that near-infrared fluorescent protein in combination with widely available near-infrared scanners overcomes these obstacles and allows for the accurate determination of cell number in vitro and tumor growth in vivo in a high-throughput manner and at negligible per-well costs. This system represents a significant advance in tracking cell proliferation in tissue culture as well as in animals, with widespread applications in cell biology.
Scientific Reports | 2017
A Hock; Eric C. Cheung; Timothy J. Humpton; Tiziana Monteverde; Viola Paulus-Hock; Pearl Lee; Ewan J. McGhee; Alessandro Scopelliti; Daniel J. Murphy; Douglas Strathdee; Karen Blyth; Karen H. Vousden
While the use of bioluminescent proteins for molecular imaging is a powerful technology to further our understanding of complex processes, fluorescent labeling with visible light fluorescent proteins such as GFP and RFP suffers from poor tissue penetration and high background autofluorescence. To overcome these limitations, we generated an inducible knock-in mouse model of iRFP713. This model was used to assess Cre activity in a Rosa Cre–ER background and quantify Cre activity upon different tamoxifen treatments in several organs. We also show that iRFP can be readily detected in 3D organoid cultures, FACS analysis and in vivo tumour models. Taken together we demonstrate that iRFP713 is a progressive step in in vivo imaging and analysis that widens the optical imaging window to the near-infrared spectrum, thereby allowing deeper tissue penetration, quicker image acquisition without the need to inject substrates and a better signal to background ratio in genetically engineered mouse models (GEMMs).
Molecular Cancer Research | 2016
Pearl Lee; Eric C. Cheung; Karen H. Vousden
The p53 tumor suppressor protein inhibits the development of cancer by initiating various cellular responses including apoptosis, senescence and cell cycle arrest. In addition to this, recent studies have found that p53 is also able to influence cell metabolism. TP53-induced glycolysis and apoptosis regulator (TIGAR) was discovered as a p53 target functioning as a fructose-2,6-bisphosphatase. In this way, TIGAR can modulate glucose metabolism, resulting in enhanced NADPH production and antioxidant defence. While discovered as a p53 target, basal expression of TIGAR is not affected by loss of p53 or its family member TAp73 in mice and increased expression of TIGAR in the small intestines is still observed following irradiation in these animals. Moreover, this induction is retained in mice deleted of both p53 and TAp73, demonstrating that TIGAR expression is not dependent on either of these transcription factors. In mouse intestines, TIGAR is important in repair following tissue injury and mice that are TIGAR-deficient show elevated levels of oxidative stress following damage. As the Wnt/Myc signalling pathway is important in cellular proliferation and tissue regeneration, its potential role in regulating TIGAR was investigated. Deletion of APC in mouse intestines, leading to high Wnt pathway activation, results in an increased expression of TIGAR, suggesting that the Wnt/Myc signalling pathway may influence the regulation of TIGAR. Together, the results suggest that TIGAR can be regulated through p53-dependent and independent mechanisms to contribute to the control of tissue regeneration and tumorigenesis. Funded by Cancer Research UK, PL is a recipient of an MRC studentship. Citation Format: Pearl Lee, Eric C. Cheung, Karen H. Vousden. The regulation of TIGAR. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr A47.
Cancer and Metabolism | 2014
Eric C. Cheung; Pearl Lee; Celia R. Berkers; Karen Blyth; Owen J. Sansom; Karen H. Vousden
The p53 tumour suppressor inhibits tumour development via various mechanisms such as apoptosis, inhibition of proliferation or the activation of senescence. Recently, several studies have indicated a novel role of p53 in the regulation of energy metabolism. Previously we have discovered TIGAR, a p53 target gene that acts as a fructose-2,6-bisphosphatase. TIGAR would therefore be predicted to redirect glucose from the glycolytic pathway to secondary pathways such as the pentose phosphate pathway (PPP). Indeed, TIGAR can promote NADPH production to generate reduced glutathione for protection against ROS. In order to understand the function of TIGAR in vivo, we generated TIGAR deficient mice. We have determined a critical role of TIGAR in rapidly proliferating tissue, either for repair after damage or during tumor development. These studies support a role for TIGAR in maintaining both antioxidant activity and nucleotide synthesis, both generated through the PPP. We are now also investigating the role of TIGAR in other metabolic pathways such as the hexosamine biosynthesis pathway, and in other animal models of cancer.
Cancer and Metabolism | 2014
Pearl Lee; Eric C. Cheung; Karen H. Vousden
TIGAR (TP53-induced glycolysis and apoptosis regulator) functions to promote antioxidant defence, with a loss of TIGAR associated with a defect in a cell’s ability to control reactive oxygen species (ROS) and resultant oxidative damage. TIGAR can function as a fructose-2,6-bisphosphatase, lowering the levels of fructose-2,6- bisphosphate, which is an activator of phosphofructokinase-1. As a consequence, TIGAR activity results in a dampening of the glycolytic pathway and, by enhancing the pentose phosphate pathway, increases cellular antioxidant capacity by promoting the generation of NADPH and GSH. Although TIGAR is clearly a transcriptional target of the tumour suppressor p53 in human cells, the activation of TIGAR expression in mouse cells in vitro and in a mouse model of intestinal regeneration was not dependent on p53 or its family member TAp73. However, TIGAR expression was strongly induced in the mouse intestine during proliferation following damage or APC loss, suggesting a role for the Wnt signalling pathway. The increase in TIGAR expression seen in response to APC loss was lost after simultaneous deletion of c-Myc, suggesting that TIGAR responds to c-Myc activation downstream of the Wnt signalling pathway. While TIGAR may be a direct Myc target, Myc was shown to induce ROS, which were also found to regulate the expression of TIGAR. In order to further understand the function of TIGAR, a TIGAR-deficient mouse was generated and TIGAR was found to play a role in supporting intestinal regeneration by lowering oxidative stress in the small intestinal crypts following tissue damage by irradiation or cisplatin treatment. Moreover, TIGAR-null mice showed decreased tumour development in a model of intestinal adenoma. In particular, it was found that TIGAR acts to lower the damaging pool of ROS during oxidative stress. Through this, TIGAR can function to promote tumourigenesis and elevated TIGAR expression has been observed in various cancer types, independently of p53 status. This suggests that a deregulated expression of TIGAR may play a role in supporting rather than inhibiting cancer development. This study reveals p53-independent mechanisms by which TIGAR is regulated and how TIGAR can contribute to promote cell growth and tumourigenesis.