Arizona Cancer Center at the University of Arizona, Tucson
Eugene W. Gerner, Ph.D., Principal Investigator
Arizona Cancer Center
University of Arizona
1515 N. Campbell Avenue
PO Box 245024
Tucson, AZ 85724
Gastrointestinal (GI) cancers account for nearly 20 percent of cancer deaths, and colorectal cancer (CRC) continues to be the second leading cause of such deaths, in the USA in 2006. The long-term objective of our SPORE in GI Cancers is to decrease mortality due to GI cancers by developing novel approaches for risk assessment, screening, chemoprevention and therapeutics. The GI SPORE includes four projects, three cores and developmental research and career development programs.
Project 1 is entitled Genetic Variability as Prognostic or Predictive Factors in Colorectal Intraepithelial Neoplasia (IEN). The translational goal of this project is to demonstrate that tailoring prevention therapy in high-risk individuals, based on host and adenoma characteristics, will reduce the development of clinically significant colonic IEN.
Project 2 is entitled Barrett’s Esophagus and Oxidative Stress: Role of Gastric Acid and Bile Acids. The translational goal of this project is to determine if ursodeoxycholic acid can modify markers of oxidative stress and/or cancer risk in patients with Barrett’s esophagus.
Project 3 is entitled Mechanistic Translational Studies of the Stress Response in Gastrointestinal Cancer. The translational goal of this project is to exploit processes associated with altered blood perfusion in tumors for therapeutic benefit.
Project 4 is entitled Drug Targeting of G-Quadraplex-NM23-H2 Complex in the c-MYC Promoter, and targets an important oncogene in GI cancer development.
The goals of both Projects 3 and 4 are to conduct translation studies with novel target-directed drugs for treatment of GI cancers.
The projects are supported by an extensive Human GI Tissue Resource, which includes access to existing normal and neoplastic tissue specimens, which have been gathered from approximately 6000 participants in colon polyp prevention trials, over 600 patients with Barrett’s esophagus, and over 500 surgical patients who were treated for various GI malignancies. A Statistics and Informatics Core provides state-of-the-art statistical, computational and informatics support for all projects in our efforts to discover new prognostic markers and drug targets. The Evaluation and Administration Core is the critical feedback loop necessary for a productive SPORE. The Developmental Research Program ensures that the most promising translational ideas are nurtured and funded. The complementary Career Development Program will support and mentor physicians and scientists in translational research.
Taken collectively, the ACC SPORE in GI Cancer offers a unique opportunity to prevent and cure GI cancer.
The ACC SPORE is organized into 4 Projects and 6 Cores. The Projects and Cores are described below.
Eugene W. Gerner, Ph.D. (Basic Scientist)
Patricia Thompson, Ph.D. (Applied Scientist)
The translational goal of this project is to identify host characteristics that can be used to individually tailor colon cancer prevention therapy in order to reduce the development of clinically significant colorectal intraepithelial neoplasia (IEN) in humans with elevated risk for colon cancer.
The hypothesis to be tested in this proposal is that individual responses to certain colon cancer preventive agents, including specific non-steroidal anti-inflammatory drugs (NSAIDS) and agents that target features of polyamine metabolism, are influenced by host factors, including genetic background, and diet.
Three specific aims are proposed to test this hypothesis. First, we will determine if genetic variability in the host gene encoding ornithine decarboxylase (ODC) can explain individual variability in colorectal mucosal polyamine contents. We will also determine if variability in the ODC and/or the flavin monooxygenase 3 (FMO3) genes modulate the action and/or bioavailability of the chemopreventive agents sulindac and difluoromethylornithine (DFMO) when given in combination for the reduction of colon polyp recurrence. Second, we will determine if the association between the ODC G316A promoter variant alleles and adenoma recurrence in aspirin users involves other genes, which affect polyamine metabolism. This aim will focus on the spermidine/spermine N1-acetyltransferase (SSAT), and determine if acetylated polyamines, which are substrates for polyamine export, may be a useful biomarker of NSAID action. Third, we will assess the independent and joint effects of aspirin use, dietary sources of polyamines, and gene modifiers of polyamine synthesis (ODC) on risk of colorectal adenoma recurrence. We will pool data from three adenoma recurrence studies, including the Polyp Prevention Trial (PPT), Wheat Bran Fiber (WBF) and Ursodeoxycholic Acid (UDCA) colon polyp prevention trials to assess these effects on overall adenoma recurrence and recurrence of advanced lesions.
The long-term goal of this project is to determine the influence of host and adenoma factors as predictors of efficacy for the chemoprevention of colorectal adenomas, particularly advanced, clinically significant lesions, and to use this information to reduce the incidence of colorectal cancer in individuals with high risk of developing this disease.
Katerina Dvorak, Ph.D. (Basic Scientist)
Richard Sampliner, M.D.. (Applied Scientist)
Our major translational goal is to develop a chemopreventive strategy for inhibiting progression of Barrett’s esophagus to esophageal adenocarcinoma. We hypothesize that the deleterious effects of hydrophobic bile acids and low pH may be inhibited by the cytoprotective bile acid, ursodeoxycholic acid (UDCA), that was shown to protect cells against oxidative injury.
The central hypothesis to be tested in this proposal is that bile acids in combination with low pH induce oxidative stress that leads to DNA damage, genomic instability and apoptosis resistance in Barrett’s esophagus. Therefore, an alteration of bile acid composition by ursodeoxycholic acid treatment may be beneficial to Barrett’s esophagus patients in the prevention of neoplastic progression.
Three specific aims are proposed to test this hypothesis. First, we will evaluate the effect of a bile acid cocktail and/or low pH on the generation of reactive oxygen species (ROS), oxidative DNA damage, expression of DNA repair proteins, anti-oxidant and anti-apoptotic proteins in vitro in esophageal cell lines and ex vivo in BE biopsies. We will determine the effect of acute, repeated and chronic exposure to bile acids and/or low pH (1) on the induction of superoxide, (2) formation of 8-OH-dG, a marker of oxidative DNA damage, (3) expression of DNA repair proteins (i.e. Mlh1, Pms2 and PARP), anti-oxidant (i.e. superoxide dismutases and catalase) and anti-apoptotic proteins (i.e. Mcl-1, survivin, Bcl-xL). Furthermore, we plan to identify patterns of DNA alterations using microarray-based comparative genomic hybridization (CGH) in novel esophageal cell lines developed for resistance to bile acids and/or low pH. In specific aim #2 we plan to evaluate the effects of UDCA and its conjugated forms [(tauro-ursodeoxycholic acid (TUDCA), glyco-ursodeoxycholic acid (GUDCA)] on ROS production, oxidative DNA damage, genomic instability and the expression of DNA repair proteins, anti-oxidant and anti-apoptotic proteins induced by low pH and cytotoxic bile acids in vitro. Since UDCA is an excellent scavenger of ROS we anticipate that UDCA will reduce damage caused by bile acids and low pH. Finally, in specific aim #3 we propose to conduct a pilot clinical trial to evaluate UDCA as a potential preventive agent that changes the composition of bile acids in the refluxate so that less toxic bile acids are refluxed to the esophagus. Thus, bile acid composition at the baseline and post UDCA treatment will be determined. Furthermore, markers of oxidative stress (8-OH-dG) and proliferation (Ki-67) will be assessed in BE biopsies at the baseline, 6 months on UDCA and 6 months after discontinuation of UDCA using immunohistochemistry in conjunction with image analysis.
Our long-term goal is to evaluate factors and molecular mechanisms leading to BE development and/or progression to esophageal adenocarcinoma and to inhibit these processes.
Garth Powis, D.Phil, Ph.D. (Basic Scientist)
James Abbruzzese, M.D. (Applied Scientist)
The translational goal of this project is to develop new target-directed drugs for the treatment of colorectal cancer. Colorectal tumors exist in a stressed environment. As they grow, they outstrip new blood vessel formation leading to poor perfusion, nutrient deprivation and hypoxia. Cancer cells adapt to this stress by changes in key cell survival signaling pathways leading to resistance to cell death, increased anaerobic metabolism, new blood vessel formation and increased metastasis. Although the changes give aggressive, resistant tumors they also provide an Achilles heel for selectively attacking the tumor because without the changes the cancer cells will die.
The hypothesis upon which our studies are based is that the signaling pathways that regulate the growing tumor’s response to inadequate blood perfusion, nutrient deprivation and hypoxia provide novel targets for the development of agents to selectively treat cancer. We will study two pathways and conduct two clinical trials in colorectal cancer of agents developed by us that inhibit the pathways. The first pathway is the thioredoxin-1 (Trx-1) redox signaling pathway and its inhibitor PX-12 that has already shown antitumor activity in patients with colorectal cancer in a Phase I trial. We have show that PX-12 inhibits the hypoxia inducible factor-1 and the Sp1 mediated increase in tumor VEGF formation, EGFR and IGF-1R expression and increases the activity of the Nrf2 transcription factor that plays a dual role in regulating polyamine metabolism through the polyamine response element (PRE) and the antioxidant defense through the antioxidant response element (ARE) in cancer cells. The second pathway is the phosphatidylinositol-3-kinase (PI-3-K) stress signaling pathway, the most frequent signaling abnormality in human cancer. PI-3-K is mutated and activated in many colorectal cancers. We have developed PX-866 a potent inhibitor of PI-3-K and identified a potential biomarker for predicting response.
The specific aims are:1) to investigate the mechanisms for the redox regulation of transcription factors by Trx-1 and its reversal by PX-12; 2) to conduct a Phase I/II clinical trial of PX-12 in colorectal cancer with mechanistic molecular marker and imaging; 3) to investigate mechanisms mediating the response to PI-3-K inhibition in colorectal cancer; and 4) to conduct a PhaseI/II clinical trail of PX-866 in colorectal cancer with mechanistic marker and imaging studies.
The long-term goal of our work is to conduct translational studies of the mechanisms of stress induced gene expression that will lead to the development of novel agents for colorectal cancer treatment.
Laurence Hurley, Ph.D., D.Sc. (Basic Scientist)
Daniel D. Von Hoff, M.D., F.A.C.P. (Applied Scientist)
The translational goal in Project 4 is to identify and bring forward into clinical trials one or two lead compounds that will suppress c-Myc transcription by targeting the NM23-H2–DNA complex.
This proposal builds upon progress from the last grant period and will further test hypothesis that the NM23-H2–DNA complex is critically involved in transcriptional activation of c-Myc and c-Myc is a critical factor in colon cancer.
The specific aims of the proposal are (1) structural characterization of the G-quadruplex–drug complexes in the c-Myc promoter, (2) to establish in vitro biochemical and cell-based screens to identify small molecules that inhibit binding of NM23-H2 to the G-quadruplex in the silencer element of the c-Myc promoter, (3) to discover and optimize G-quadruplex- and NM23-H2-interactive compounds using computer-aided drug design and structure-based and virtual-screening approaches, (4) In vivo evaluation and subsequent preclinical development, and (5) to file an IND for Phase I clinical trial and overall clinical development program. High-field NMR will be used to characterize the drug–G-quadruplex complex, molecular modeling will be used to identify new lead compounds, and fluorescence resonance energy transfer (FRET) and double-filter methods will be used for identification of in vitro biochemical hits. A luciferase-based high-throughput screen has already been used to identify hits, and subsequent assays will be carried out in matched cell lines genetically engineered to provide proof of principle that the mechanism of action is as proposed. Structure-based approaches will be used to aid in lead optimization. Following lead optimization, an IND will be filed and the clinical development program will be based upon discoveries from specific aims 1–4. Immunohistochemistry will be used to guide patient selection and phase I and II clinical trial plans will be designed to determine whether the new agents will help patients with advanced colorectal cancer.
The long-term goal of this research is to develop novel target-directed drugs for treatment of colorectal cancer.
Achyut Bhattachryya, M.D.
The GI Human Tissue Resource coordinates histopathological assessment of all GI tissues collected from two local Tucson-area hospitals and existing banks of normal and neoplastic GI tissues. Approximately 400 colorectal, esophageal and pancreatic cancer patients are seen annually at the Arizona Cancer Center (AZCC) and the Southern Arizona Veterans Administration Medical Center (SAVAMC). During the past funding period, we collected over 2,000 surgical specimens prospectively. Existing tissue banks contain over 5000 frozen and fixed samples of normal and neoplastic intestinal and pancreaticobiliary tissues. More than 1500 colon adenomas and over 800 specimens from patients with Barrett's esophagus have been collected and stored during the course of cancer prevention studies conducted at the AZCC and SAVAMC. Standard methods of preservation and storing tissues are employed to facilitate measurement of desired endpoints. Special services, such as laser capture microdissection, tissue arrays, and digitized virtual slides of the specimens are available to SPORE investigators.
The activities of Core A-GI Tissue Resource are coordinated with other resources, to ensure collection of tissues from patients participating in the clinical trials, standards of marker measurement in tissues, adequacy of statistical input into design of trials and evaluation of results from patient studies. With the assistance of Core B -Informatics, a comprehensive database for all samples within the GI Tissue Resource has been established. This database is designed so that it can be interrogated for patient related information, including outcome data, and specific prognostic and/or predictive factors obtained during the course of this research effort. The G.I. Tissue Resource is essential for translational aspects of all the G.I. SPORE projects. We have a significant resource for our G.I. SPORE and outside SPORE investigators.
Bonnie LaFleur, Ph.D. and David Mount, Ph.D.
Core B provides essential statistical, computational, and informatics expertise that is necessary for all GI SPORE projects and investigators to achieve the translational goals of the SPORE grant in a timely and efficient manner. Core B personnel are expertly qualified for this task and represent a broad spectrum of capability in biostatistics and computational analysis. They contribute significantly to the GI SPORE projects through extensive interactions with SPORE investigators and have been actively involved with experimental design and analysis for each project. Core B contributions fall into two main areas, biostatistics and informatics.
Biostatistical analysis includes descriptive analysis of data, hypothesis testing, group comparisons using t-tests or analysis of variance, linear and logistic regression, zero-inflated Poisson regression, Generalized Estimating Equations, and assessment of relationships between time and potential clinical, laboratory, and treatment covariates. Transformations are used as needed to meet statistical assumptions and, when such transformations are not available, nonparametric procedures are used. False discovery rates are estimated to compensate for multiple comparisons common in high throughput data analysis. Biostatistical input also includes an essential role in planning of projects, study design, and protocol development.
Informatics includes web sites for data storage and information sharing, data management support, bioinformatics support for sequence and genome analysis, software methods for finding and validating predictive markers and drug targets, haplotype analysis, advanced computational modeling of large data sets, and biological interpretation of microarray and high-throughput data. Core B personnel are expert data managers and perl/java/R programmers prepared to meet the computational needs of the SPORE grant.
The combined biostatistical and informatics expertise of Core B offers a full range of data analysis and exploratory methods that are of enormous importance to each SPORE project.
Eugene W. Gerner , Ph.D.
SPORE grants have several unique features that require added attention to evaluation and administration. The Evaluation and Administration Core provides a framework for supporting the unique features of the SPORE as well as the more routine administrative tasks associated with a large, diverse, multiple project grant. The essential services provided by this core are listed below.