Glyoxalase 1 as a Novel Molecular Marker of High-Grade Prostatic Intraepithelial Neoplasia and Causative Effector in the Progression of Prostate Cancer
AdvisorWondrak, Georg T.
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PublisherThe University of Arizona.
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AbstractThe prostate is a male accessory sex gland that functions to produce many components of the seminal fluid including zinc and citrate, both of which are crucial to men fertility. The prostate gland has two main compartments: the stroma and the epithelium. Three cell types comprise the prostatic epithelium: secretory epithelial cells, basal/stem cells, and neuroendocrine cells. The prostatic epithelium is unique in that they are the only healthy human cells that produce energy by glycolysis rather than the Krebs cycle. Changes in the prostatic epithelium leading to malignant proliferation increase in incidence with age. Prostate carcinoma (PCa) is the leading malignancy and the second leading cause of cancer-associated deaths in the USA male population. PCa is a disease of the elderly and risk prediction becomes crucial. Most patients present low-risk, relatively indolent tumors; however, 20-30% of these men present tumor characteristics associated with high-risk PCa. High Grade Prostatic intraepithelial neoplasia (HGPIN) is the only widely accepted histological condition and precursor of invasive PCa. High glycolytic activity is an oncometabolic hallmark of cancer. Cancer cells turn to aerobic glycolysis for energy production in a process referred to as ‘the Warburg effect’ leading to accumulation of methylglyoxal (MG), a cytotoxic glycolytic byproduct responsible for the adduction of macromolecules, a process called advanced glycation end-products (AGEs) formation. Glyoxalase 1 (GLO1), also known as lactoylglutathione lyase (EC: 184.108.40.206), is part of the glyoxalase system, playing a crucial role in cellular detoxification of spontaneously formed MG. In a two-step reaction, GLO1 first catalyzes the conversion of highly reactive MG to S-D-lactoylgluthatione. The resulting thioester, in the case of MG, is then hydrolyzed by GLO2 to produce D-lactate and reformed glutathione (GSH). The cytoprotective glyoxalase system prevents formation of AGEs and promotes cell survival. GLO1 upregulation has been described in the context of metabolic and inflammatory stress in vitro and in vivo, serving as a cellular mechanism to detoxify high levels of MG, particularly in cancer, where high glycolytic rates as a result of the ‘Warburg effect’ are observed. Our laboratory has demonstrated GLO1 upregulation during tumor progression, observable in HGPIN and PCa versus normal prostatic tissue by immunohistochemistry in archival tumor samples. GLO1 upregulation was identified as a novel hallmark of HGPIN lesions. In PCa specimens, GLO1 expression correlated with intermediate–high risk Gleason grade but not with patient age, biochemical recurrence, or pathological stage. Using CRISPR/Cas9 we genetically engineered GLO1 knock-out isogenic clones from DU-145 prostate carcinoma cells to further examine the role of GLO1 in PCa. Interestingly, we showed upregulation of TXNIP (encoding the thioredoxin-interacting protein) in the DU-145-GLO1_KO as a function of GLO1 status. TXNIP is a master regulator of cellular energy metabolism and redox homeostasis, also considered a tumor suppressor. Furthermore, GLO1 elimination had a profound detrimental effect in the clonogenicity and invasiveness capacity. We also identified MMP-3 (encoding matrix metalloproteinase-3) and SPP1 (encoding secreted phosphoprotein 1) as the two genes displaying the most profound downregulation in response to GLO1 elimination. MMP-3 and SPP1 are two effectors implicated in the development of prostate cancer in the bone, tumor-associated inflammation, facilitating metastasis, and promoting drug resistance. Additionally, based on The Human Protein Atlas data, decreased survival probability correlated with high MMP-3 mRNA expression levels in tissue from prostate cancer patients suggesting that GLO1 expression status is a novel and underappreciated determinant of PCa invasiveness and patient survival. Our published GLO1 data generated some excitement in the private sector with a potential translational application for GLO1 in the clinical setting. Current studies performed at Roche Diagnostics seek to develop a methodology for the detection of malignant biochemical signatures in tissue by spectroscopic imaging. These signatures can be used as biomarkers of early prostate cancer associated with aggressive disease. GLO1 promises to be one of the targets of study. Our future goals seek to (a) have a better understanding of the molecular mechanisms underlining oncometabolic dysregulation in PCa, (b) an improved understanding of the molecular basis underlying early PCa with a focus on HGPIN lesions pursued in relevant murine models, (c) identify improved molecular therapeutics that allow early interventions targeting HGPIN and mPCa. Translationally, we seek to aid in the development of powerful prognostic and diagnostic biomarkers identifying HGPIN and PCa and the discovery and development of novel optics-based technologies for the antibody independent diagnosis and prediction of PCa grade and progression.
Degree ProgramGraduate College