Dawn L. Duval

Biography of Investigator:
Dr. Duval grew up on a cattle ranch in Northeastern Nevada. She got started in research while attending the University of Nevada, Reno as a Biochemistry undergraduate student. As part of an undergraduate Research Scholarship program, she studied the ability of plant flavonoids to inhibit mitochondrial respiration as a potential screen for chemotherapeutic agents to treat cancer. In order to further her research career, she obtained a Ph.D. from the Cell and Molecular Pharmacology and Physiology Program at the University of Nevada and had postdoctoral and junior faculty training at Colorado State University and the University of Colorado Health Sciences Center. Much of her graduate and postdoctoral training has explored mechanisms of gene regulation. She is currently applying that knowledge base to explore the gene expression changes that contribute to cancer development and metastatic progression in models of hormone refractory breast cancer, canine osteosarcoma, and pituitary ontology.

Classes Taught/Currently Teaching:
At the University of Colorado Health Sciences Center, she taught: Practical Applications of Molecular and Cell Biology Techniques for the Clinical Investigator, Introduction to Reproductive Endocrinology, and Integrated Organ Systems 6, Pathophysiology of Breast and Prostate Cancer. Currently, she has been lecturing in VS 580, Physiology and Pathophysiology and EH 733 Environmental Carcinogenesis.

Research Focus:
The development and progression of cancer is characterized by changes in gene expression that confer a growth and survival advantage to the cancer cells.  Current studies in the laboratory focus on identifying changes in gene expression that serve as both predictive/prognostic markers for cancer progression and resistance to therapy as well as potential targets for the development of new therapies.

Future Direction:
We will use the knowledge gained in our studies to identify important biological pathways for cancer development and progression and develop therapeutic agents that target those pathways.

Name of Laboratory:
Molecular Oncology

Laboratory Personnel:
Sara Anglin

List of Major Laboratory Equipment/Technical Resources Used:

1. Messenger RNA and DNA isolation
2. Affymetrix chip analysis
3. Quantitative real time PCR
4. Stable and transient transfection of mammalian cells using lipid mediated gene transfer and electroporation
5. Gene expression using constitutive and inducible systems
6. Gene knockdown using siRNA strategies
7. Luciferase reporter assays on chemiluminescent platereader

Current Work/Projects:
Specifically, we are currently identifying molecular markers for metastasis and resistance to therapy in canine osteosarcoma using gene expression analysis on Affymetrix Canine Genome 2.0 Array chips from mRNA isolated from archived primary canine osteosarcomas.  Targets identified in these studies will be validated using real-time quantitative PCR to validate changes in mRNA levels as well as immunohistochemistry to detect changes in protein expression. These studies should improve our ability to treat osteosarcoma as well as identify putative new targets for drug development.

Since expression of Ets transcription factors has been associated with breast cancer, we are currently assessing the role of Ets factors in the progression of breast cancer from estrogen dependence to estrogen independence and resistance to hormone-based therapies.  In these studies, we are utilizing a tetracycline-dependent inducible expression system (Tet-ON) to induce the expression of Ets-1 in stably transfected estrogen dependent MCF-7 breast cancer cells. Following Ets-1 expression, these cells can be tested for their dependence upon estrogen for growth both in tissue culture and nude mouse models. These Ets-1 expressing clones can also be assessed for changes in motility and invasion and have been engineered to constitutively express firefly luciferase so that tumor growth and metastasis can be tracked in nude mice using the Xenogen system. Gene expression changes in response to Ets-1 can be assessed using Affymetrix chips. The effect of Ets-1 expression on estrogen dependent gene expression can be
explored using transient transfection with gene promoter-luciferase reporter constructs and reading luciferase activity on a chemiluminescent platereader and analysis of Ets-1 targets in breast cancer cells using chromatin immunoprecipitation analysis.

In addition, we are examining the role of Ets transcription factors and the pituitary specific transcription factor, Pit-1, in mediating oncogenic Ras and growth factor signaling in the pituitary gland.  We are asking how phosphorylation of Pit-1 can alter its association with Ets-1 and other transcriptional cofactors and regulate the proliferation of cells in the pituitary gland during normal pituitary development, hyperproliferative states and cancer.

Publications: (Recent)
K.D. Augustijn*, D.L.Duval*, R. Wechselberger, R. Kaptein, A. Gutierrez-Hartmann, P.C. van der Vliet. Structural characterization of the Pit-1/Ets-1 interaction:  Charge dependence of Pit-1 for Ets-1 binding. Proc. Natl Acad Sci. 99: 12657-12662, 2002. *These authors contributed equally to this manuscript.

D.L. Duval, A. Jean, and A. Gutierrez-Hartmann. Ras signaling and transcriptional synergy at a flexible Ets-1/Pit-1 composite DNA element is defined by the assembly of selective activation domains. J Biol Chem. 278(41):39684-96, 2003.

B.S. Ellsworth, A.T. Burns, K.W. Escudero, D.L. Duval, S.E. Nelson, C.M. Clay. The gonadotropin releasing hormone (GnRH) receptor activating sequence (GRAS) is a composite regulatory element that interacts with multiple classes of transcription factors including Smads, AP-1 and a forkhead DNA binding protein. Mol Cell Endocrinol. 206(1-2):93-111, 2003.

D.L. Duval, M.D. Jonsen, S.E. Diamond, P. Murapa, A. Jean and A. Gutierrez-Hartmann. Differential Utilization Of Transcription Activation Subdomains By Distinct Coactivators Regulates Pit-1 Basal And Ras Responsiveness. Mol Endocrinol. 21(1):172-85, 2007.

S. Jirawatnotai, E. Osmundson, D.L. Duval, K. Branson-Smith, C. Ott, D.S. Moons, D. Ray, A. Gutierrez-Hartmann, and H. Kiyokawa.  G1-regulatory Cyclin D/CDK4 negatively modulates the Ets-dependent activity of the prolactin promoter. J Endocrinol. (Submitted.)

M.D. Jonsen, D.L. Duval and A. Gutierrez-Hartmann. The 26-amino acid ß-motif of the Pit-1ß transcription factor is an independent repressor domain possessing protein and DNA context dependent and independent activity. Mol Endocrinol. 2008. (Submitted.)

D.L. Duval and A. Jean.  Phosphorylation of Pit-1 Threonine 220 Alters Binding to Distinct DNA binding sites Reducing Ras and Estrogen Stimulation of the Prolactin Gene Promoter. (In preparation.)

A. Gutierrez-Hartmann, D.L. Duval, A.P. Bradford. ETS Transcription Factors in Endocrine Systems. Trends Endocrinol Metab. 18(4):150-8, 2007.

Post Doctorates/Graduate Students:
Name: Liza Pfaff, DVM/Ph.D. (dual-degree program)
Email Address:liza.pfaff@colostate.edu
Area of Study: Canine Osteosarcoma
Graduation Date: 2013

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