Return to Skip Menu

Main Content

Roadmap published for dynamic mapping of estrogen signaling in breast cancer


NATIONAL CAPITAL REGION, June 16, 2011 – The first roadmap to mathematical modeling of a powerful basic "decision circuit" in breast cancer has been developed and published in Nature Reviews Cancer.

The preliminary mathematical model is the first result of a $7.5 million federal grant, awarded to scientists at the Lombardi Comprehensive Cancer Center at Georgetown University Medical Center (GUMC) and collaborators at Virginia Tech and Fox Chase Cancer Center, to develop a systems approach to understanding and treating one of the most common forms of breast cancer.

"A cell is an information processing system and cancer cells make decisions that promote their growth, so we are striving to understand how these cells make mathematically-based choices based on inputs, processing, and outputs," said lead investigator Robert Clarke, a professor of oncology at Lombardi and GUMC's newly appointed dean for research.

The model, which is being built in modules, is designed to understand estrogen signaling in breast cancer cells, and by extension, why some cancer cells are susceptible to endocrine therapy while others are not. The estrogen hormone drives over half of the 180,000 cases of invasive breast cancer diagnosed each year, yet endocrine therapies designed to shut down this growth pathway are not as successful as simpler, human-derived models would have predicted, Clarke said.

"We need an engineering approach to a biological problem, and this is a very novel, and promising, start," said Clarke. "No one has built a model of breast cancer cell fate decision making like this before."

Working with him are Louis M. Weiner, director of the Lombardi Comprehensive Cancer Center; computational cell biologist John J. Tyson, University Distinguished Professor of Biology in the College of Science at Virginia Tech; and William T Baumann, associate professor of electrical and computer engineer at Virginia Tech. Tyson and Baumann have assembled a team of graduate students and postdoctoral researchers to assist in the modeling project.

Yue Wang, the Grant A. Dove Professor of Electrical and Computer Engineering; Chun Chen and Iman Tavassoly, a Ph.D. students in the Genetics, Bioinformatics, and Computational Biology Program at Virginia Tech; and Anael Verdugo, a National Science Foundation postdoctoral fellow in biological sciences at Virginia Tech, are also co-authors on the paper.

"We are providing a roadmap of how a modeler might capture, in mathematical form, the molecular events controlling cell growth, proliferation, damage responses, and programmed cell death," said Tyson, who is the first author of the article. "The value of this enterprise will be measured ultimately by new insights provided by the model into the logic and functionality of estrogen-receptor signaling and by the effectiveness of the model as a tool for experimental prediction and design."

While scientists have amassed a large body of information about the genes and proteins involved in pathways that govern cancer development and growth, and based on that, have developed some "good ideas about how they go awry in certain cancers, most of our understanding relies on intuitive reasoning about highly complex networks of biochemical interactions," the researchers wrote. "Wouldn't it be better if we could frame a reaction network in precise mathematical terms and use computer simulation to work out the implications of how the network functions in normal cells and malfunctions in cancer cells?"

"The hallmark of cancer cells is that they are making decisions that are right for them, not for the survival of the human organism, so we need to understand those choices," Clarke said.

The roadmap detailed in Nature Reviews Cancer is built on the idea that a cell is an information processing system, receiving signals from its environment and its own internal state, interpreting those signals, and making appropriate cell-fate decisions, such as growth and division, movement, differentiation, self-replication, or cell death.

To that end, the investigators have already begun to model separate modules that computers can track in terms of the dynamic consequences of multiple and often conflicting interactions. These include "decision modules" (cell cycle and apoptosis), "stress modules" (autophagy and unfolded protein response), and the "signal processing modules" (estrogen receptor and growth factor signaling transduction networks).

Clarke said that a lot of "wet lab work" data from Lombardi laboratories measuring how changes in gene and protein expression affects response to endocrine therapy is being transferred into the model, along with published information from other institutions.

Not only does the model have the potential to explain why certain subtypes of breast cancer respond or become resistant to endocrine therapy, it could be used to help test potential new therapies, he said.

"If we tweak some gene in the model and all the breast cancer cells die, we can go back to the lab and test if that actually occurs," Clarke said. "That means that once we understand the decisions that these cancer cells are making, we have an efficient way of developing drugs or combination of drugs."

"The hard work is yet to be done, but it is just a matter a time before an effective, integrated model of regulatory networks in breast cancer cells is informing the next wave of experiments and therapies," said Tyson.

The Lombardi Comprehensive Cancer Center, part of Georgetown University Medical Center and Georgetown University Hospital, seeks to improve the diagnosis, treatment, and prevention of cancer through innovative basic and clinical research, patient care, community education and outreach, and the training of cancer specialists of the future. Lombardi is one of only 40 comprehensive cancer centers in the nation, as designated by the National Cancer Institute, and the only one in the Washington, D.C., area.

Georgetown University Medical Center is an internationally recognized academic medical center with a three-part mission of research, teaching and patient care (through MedStar Health). GUMC's mission is carried out with a strong emphasis on public service and a dedication to the Catholic, Jesuit principle of cura personalis -- or "care of the whole person." The Medical Center includes the School of Medicine and the School of Nursing & Health Studies, both nationally ranked; Georgetown Lombardi Comprehensive Cancer Center, designated as a comprehensive cancer center by the National Cancer Institute; and the Biomedical Graduate Research Organization (BGRO), which accounts for the majority of externally funded research at GUMC including a Clinical Translation and Science Award from the National Institutes of Health.  In fiscal year 2009-2010, GUMC accounted for nearly 80 percent of Georgetown University's extramural research funding.

Dedicated to its motto, Ut Prosim (That I May Serve), Virginia Tech takes a hands-on, engaging approach to education, preparing scholars to be leaders in their fields and communities. As the commonwealth’s most comprehensive university and its leading research institution, Virginia Tech offers 225 undergraduate and graduate degree programs to more than 31,000 students and manages a research portfolio of $496 million. The university fulfills its land-grant mission of transforming knowledge to practice through technological leadership and by fueling economic growth and job creation locally, regionally, and across Virginia.

Tressa Iris Kirby is the media contact at Georgetown University Medical Center. Reach her at 202-687-8865 or tk275@georgetown.edu.