Barbara Delage

Bio: Barbara Delage is an academic researcher from Queen Mary University of London. The author has contributed to research in topics: Arginine & Argininosuccinate synthase. The author has an hindex of 5, co-authored 6 publications receiving 513 citations. Previous affiliations of Barbara Delage include University of Cambridge.

Arginine deprivation and argininosuccinate synthetase expression in the treatment of cancer.

Abstract: Arginine, a semi-essential amino acid in humans, is critical for the growth of human cancers, particularly those marked by de novo chemoresistance and a poor clinical outcome. In addition to protein synthesis, arginine is involved in diverse aspects of tumour metabolism, including the synthesis of nitric oxide, polyamines, nucleotides, proline and glutamate. Tumoural downregulation of the enzyme argininosuccinate synthetase (ASS1), a recognised rate-limiting step in arginine synthesis, results in an intrinsic dependence on extracellular arginine due to an inability to synthesise arginine for growth. This dependence on extracellular arginine is known as arginine auxotrophy. Several tumours are arginine auxotrophic, due to variable loss of ASS1, including hepatocellular carcinoma, malignant melanoma, malignant pleural mesothelioma, prostate and renal cancer. Importantly, targeting extracellular arginine for degradation in the absence of ASS1 triggers apoptosis in arginine auxotrophs. Several phase I/II clinical trials of the arginine-lowering drug, pegylated arginine deiminase, have shown encouraging evidence of clinical benefit and low toxicity in patients with ASS1-negative tumours. In part, ASS1 loss is due to epigenetic silencing of the ASS1 promoter in various human cancer cell lines and tumours, and it is this silencing that confers arginine auxotrophy. In relapsed ovarian cancer, this is associated with platinum refractoriness. In contrast, several platinum sensitive tumours, including primary ovarian, stomach and colorectal cancer, are characterised by ASS1 overexpression, which is regulated by proinflammatory cytokines. This review examines the prospects for novel approaches in the prevention, diagnosis and treatment of malignant disease based on ASS1 pathophysiology and its rate-limiting product, arginine.

Prognostic and Therapeutic Impact of Argininosuccinate Synthetase 1 Control in Bladder Cancer as Monitored Longitudinally by PET Imaging

Abstract: Targeted therapies have yet to have significant impact on the survival of patients with bladder cancer. In this study, we focused on the urea cycle enzyme argininosuccinate synthetase 1 (ASS1) as a therapeutic target in bladder cancer, based on our discovery of the prognostic and functional import of ASS1 in this setting. ASS1 expression status in bladder tumors from 183 Caucasian and 295 Asian patients was analyzed, along with its hypothesized prognostic impact and association with clinicopathologic features, including tumor size and invasion. Furthermore, the genetics, biology, and therapeutic implications of ASS1 loss were investigated in urothelial cancer cells. We detected ASS1 negativity in 40% of bladder cancers, in which multivariate analysis indicated worse disease-specific and metastasis-free survival. ASS1 loss secondary to epigenetic silencing was accompanied by increased tumor cell proliferation and invasion, consistent with a tumor-suppressor role for ASS1. In developing a treatment approach, we identified a novel targeted antimetabolite strategy to exploit arginine deprivation with pegylated arginine deiminase (ADI-PEG20) as a therapeutic. ADI-PEG20 was synthetically lethal in ASS1-methylated bladder cells and its exposure was associated with a marked reduction in intracellular levels of thymidine, due to suppression of both uptake and de novo synthesis. We found that thymidine uptake correlated with thymidine kinase-1 protein levels and that thymidine levels were imageable with [(18)F]-fluoro-L-thymidine (FLT)-positron emission tomography (PET). In contrast, inhibition of de novo synthesis was linked to decreased expression of thymidylate synthase and dihydrofolate reductase. Notably, inhibition of de novo synthesis was associated with potentiation of ADI-PEG20 activity by the antifolate drug pemetrexed. Taken together, our findings argue that arginine deprivation combined with antifolates warrants clinical investigation in ASS1-negative urothelial and related cancers, using FLT-PET as an early surrogate marker of response.

Promoter methylation of argininosuccinate synthetase-1 sensitises lymphomas to arginine deiminase treatment, autophagy and caspase-dependent apoptosis

Abstract: Tumours lacking argininosuccinate synthetase-1 (ASS1) are auxotrophic for arginine and sensitive to amino-acid deprivation. Here, we investigated the role of ASS1 as a biomarker of response to the arginine-lowering agent, pegylated arginine deiminase (ADI-PEG20), in lymphoid malignancies. Although ASS1 protein was largely undetectable in normal and malignant lymphoid tissues, frequent hypermethylation of the ASS1 promoter was observed specifically in the latter. A good correlation was observed between ASS1 methylation, low ASS1 mRNA, absence of ASS1 protein expression and sensitivity to ADI-PEG20 in malignant lymphoid cell lines. We confirmed that the demethylating agent 5-Aza-dC reactivated ASS1 expression and rescued lymphoma cell lines from ADI-PEG20 cytotoxicity. ASS1-methylated cell lines exhibited autophagy and caspase-dependent apoptosis following treatment with ADI-PEG20. In addition, the autophagy inhibitor chloroquine triggered an accumulation of light chain 3-II protein and potentiated the apoptotic effect of ADI-PEG20 in malignant lymphoid cells and patient-derived tumour cells. Finally, a patient with an ASS1-methylated cutaneous T-cell lymphoma responded to compassionate-use ADI-PEG20. In summary, ASS1 promoter methylation contributes to arginine auxotrophy and represents a novel biomarker for evaluating the efficacy of arginine deprivation in patients with lymphoma.

A high‐fat diet generates alterations in nuclear receptor expression: Prevention by vitamin A and links with cyclooxygenase‐2 and β‐catenin

Abstract: Epidemiologic studies suggest that intake of high energy from fat, inducing overweight, increases the risk of cancer development and promotes colon carcinogenesis. It is therefore important to understand which parameters are affected early on by a high-fat diet in order to devise and improve protective nutritional strategies. We investigated the effect of high energy/fat intake on colon mucosa of male Wistar rats induced by a single 1,2-dimethylhydrazine (DMH) injection. Aberrant crypt foci (ACF) were numbered and modifications in cyclooxygenase-2 (COX-2) and beta-catenin levels assessed. Peroxisome proliferator- and retinoic acid-activated receptors (PPAR and RAR, RXR) are key transcription factors regulating gene expression in response to nutrient-activated signals. A short-term study was designed to evaluate whether alterations in mRNA expression of nuclear receptors can be detected at the beginning of the weight gain phase induced by an appetizing hyperlipidic diet (HLD). HLD consumption induced early downregulation of PPARgamma (-33.1%) and RARbeta (-53.1%) mRNA expression concomitant with an increase in levels of COX-2 (+45.5%) and beta-catenin (+84.56%) and in the number of ACF (191.56 +/- 88.60 vs. 21.14 +/- 11.64, p < 0.05). These findings suggest that HLD increases ACF occurrence, possibly through alterations in the mRNA expression profile of nuclear receptors. Moreover, the use HLD rich in retinyl esters or supplemented with all-trans retinoic acid led to a reduction in the number of ACF. Vitamin A also prevented HLD-induced alterations and the increase in levels of COX-2 and beta-catenin. The present observations show a protective role for vitamin A against disturbances associated with HLD exposure in induced colon carcinogenesis.

Abstract 4445: Pegylated arginine deiminase induces mitochondrial apoptosis and synergizes with cisplatin in ASS1-negative malignant pleural mesothelioma

Abstract: Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC We have explored the role of pegylated arginine deiminase (ADI-PEG20), an arginine catabolizing enzyme, in argininosuccinate synthetase 1 (ASS1)-negative malignant pleural mesothelioma (MPM). MPM is a chemorefractory disease, increasing worldwide, with a median survival of less than 1 year. Novel treatments are urgently required. MPM tumors, lacking ASS1, are auxotrophic for arginine and therefore sensitive to arginine depletion driven by ADI-PEG20. First we assessed the impact of ADI-PEG20 on global gene expression to identify novel interacting pathways in the ASS1-negative MPM cell line, JU77, using the human genome U133 Plus 2.0 Array from Affymetrix combined with bioinformatic analysis. Next, three ASS1-negative MPM cell lines (MSTO-211H, 2591 and JU77) were treated in triplicate with different fixed ratios of ADI-PEG20 and cisplatin. Cellular viability was determined 6 days post-treatment by MTS colorimetric assay. Apoptosis protein induction by ADI-PEG20 and platinum, alone and in combination, was measured by western blot after mitochondrial and cytosolic fractionation. Drug interactions were analyzed using the isobologram method of Chou and Talalay. ADI-PEG20 modulated several thousand genes involved in cell cycle, DNA damage, immune, and inflammatory pathways in the ASS1-negative JU77 MPM cell line by 24hrs of drug treatment. In contrast, stable transfection of ASS1 cDNA in ASS1-negative MPM cell lines resulted in resistance to ADI-PEG20 with minimal evidence of gene modulation by 24hr of drug treatment as assessed in the JU77 MPM cell line. ADI-PEG20 triggered mitochondria-dependent apoptosis as evidenced by Smac release from mitochondria into the cytosol of ASS1-negative MPM cell lines. We confirmed that arginine depletion by ADI-PEG20 altered the mTOR/p70S6K signaling pathway and led to dephosphorylation of the translation regulation proteins S6K and E4-BP1. The expression of cell cycle regulating proteins p21 and cyclin D1 was decreased by arginine depletion, alone and in combination with cisplatin. The enhancement of cisplatin cytotoxicity by ADI-PEG20 with loss of ASS1-negative MPM cell viability as early as 24hr post treatment, supports the demonstrated strong synergy between the two drugs. In summary, the antitumor effect of platinum was potentiated markedly using ADI-PEG20, suggesting that combining arginine depletion with the current standard of care, platinum and antifolates, may offer an improvement over doublet chemotherapy alone. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4445.

mTOR signalling and cellular metabolism are mutual determinants in cancer.

Abstract: Oncogenic signalling and metabolic alterations are interrelated in cancer cells. mTOR, which is frequently activated in cancer, controls cell growth and metabolism. mTOR signalling regulates amino acid, glucose, nucleotide, fatty acid and lipid metabolism. Conversely, metabolic inputs, such as amino acids, activate mTOR. In this Review, we discuss how mTOR signalling rewires cancer cell metabolism and delineate how changes in metabolism, in turn, sustain mTOR signalling and tumorigenicity. Several drugs are being developed to perturb cancer cell metabolism. However, their efficacy as stand-alone therapies, similar to mTOR inhibitors, is limited. Here, we discuss how the interdependence of mTOR signalling and metabolism can be exploited for cancer therapy.

Amino acids in cancer.

Abstract: Over 90 years ago, Otto Warburg's seminal discovery of aerobic glycolysis established metabolic reprogramming as one of the first distinguishing characteristics of cancer1. The field of cancer metabolism subsequently revealed additional metabolic alterations in cancer by focusing on central carbon metabolism, including the citric acid cycle and pentose phosphate pathway. Recent reports have, however, uncovered substantial non-carbon metabolism contributions to cancer cell viability and growth. Amino acids, nutrients vital to the survival of all cell types, experience reprogrammed metabolism in cancer. This review outlines the diverse roles of amino acids within the tumor and in the tumor microenvironment. Beyond their role in biosynthesis, they serve as energy sources and help maintain redox balance. In addition, amino acid derivatives contribute to epigenetic regulation and immune responses linked to tumorigenesis and metastasis. Furthermore, in discussing the transporters and transaminases that mediate amino acid uptake and synthesis, we identify potential metabolic liabilities as targets for therapeutic intervention.