August 1, 2005

Master Regulatory Gene Found That Guides Fate Of Blood-Producing Stem Cells
Discovery May Lead to New Therapies For Leukemia, Other Blood Disorders

(Philadelphia, PA) - Researchers from the University of Pennsylvania School of Medicine found that a protein called NF-Ya activates several genes known to regulate the development of hematopoietic stem cells (HSC), or blood-producing stem cells, in bone marrow. Knowing the details of this pathway may one day lead to new treatments for such blood diseases as leukemia, as well as a better understanding of how HSCs work in the context of bone-marrow and peripheral-stem-cell transplantation. The authors published their findings in the early August issue of the Proceedings of the National Academy of Sciences.

“Understanding the biology behind how the body precisely controls stem-cell fate is one of the most important issues in stem-cell biology,” says senior author Stephen G. Emerson, MD, PhD, Associate Director of Clinical Research for Penn’s Abramson Cancer Center and Chief of the Division of Hematology-Oncology. When HSCs divide, they have one of three fates: develop into two more stem cells, which is called self-renewal; differentiate to become one of several mature blood-cell types; or strike a balance in which one daughter cell becomes an HSC and the other becomes a mature blood-cell type.

“We know that in diseases like leukemia, the first scenario-no differentiated cells, two HCSs developing-must occur because more and more stem cells are made,” explains Emerson. In conditions like bone-marrow failure, the second scenario-two differentiated cells and no HCSs-happens because the body runs out of HSCs.

“We want to figure out how this process is normally regulated in the body, so that we can learn to control it for therapeutic purposes,” says Emerson. “For some clinical purposes, we might want to shift the balance so that we can grow more stem cells, for those who need them. Conversely, for patients in whom this process has gone awry, such as acute leukemia, we might block the regulatory gene to shift the balance of self-renewal versus differentiation so that all the immature, leukemic cells differentiate and die.

Over the past 10 years, several gene families have been suggested to be important in regulating HSC fate-for example homebox, wnt, notch 1, and telomerase genes. Emerson and colleagues figured that one transcription factor, called NF-Y, was required for activating promoters of all of these genes. What’s more, they found that fully assembled NF-Y was activated in stem cells and disappeared when the stem cells became mature cell types, through the induction and loss of one its subunits, NF-Ya.

“When we overexpressed NF-Ya in stem cells, the stem cells produced ten- to twenty-fold more stem cells after transplantation,” says Emerson. “This makes NF-Ya the prime candidate for a master-regulatory gene for multiple, if not all, stem-cell division programs.” NF-Ya would be considered the master regulatory gene since it activates multiple HSC regulatory genes and promotes HSC self-renewal.

Practically, the researchers’ goal is to find a way to control stem-cell fate by biochemically turning NF-Ya on or off at will, to either make more stem cells in the case of bone-marrow failure and for transplantation, or to force the cells to differentiate, in the case of leukemia, where too many HSCs are made.

Co-authors are Jiang Zhu, Yi Zhang, Gerard J. Joe, and Richard Pompetti, all from Penn.

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The Abramson Cancer Center of the University of Pennsylvania was established in 1973 as a center of excellence in cancer research, patient care, education and outreach. Today, the Abramson Cancer Center ranks as one of the nation’s best in cancer care, according to U.S. News & World Report, and is one of the top five in National Cancer Institute (NCI) funding. It is one of only 39 NCI-designated comprehensive cancer centers in the United States. Home to one of the largest clinical and research programs in the world, the Abramson Cancer Center of the University of Pennsylvania has 275 active cancer researchers and 250 Penn physicians involved in cancer prevention, diagnosis and treatment.

PENN Medicine is a $2.7 billion enterprise dedicated to the related missions of medical education, biomedical research, and high-quality patient care. PENN Medicine consists of the University of Pennsylvania School of Medicine (founded in 1765 as the nation's first medical school) and the University of Pennsylvania Health System.

Penn’s School of Medicine is ranked #2 in the nation for receipt of NIH research funds; and ranked #4 in the nation in U.S. News & World Report’s most recent ranking of top research-oriented medical schools. Supporting 1,400 fulltime faculty and 700 students, the School of Medicine is recognized worldwide for its superior education and training of the next generation of physician-scientists and leaders of academic medicine.

The University of Pennsylvania Health System includes: its flagship hospital, the Hospital of the University of Pennsylvania, consistently rated one of the nation’s “Honor Roll” hospitals by U.S. News & World Report; Pennsylvania Hospital, the nation's first hospital; Penn Presbyterian Medical Center; a faculty practice plan; a primary-care provider network; two multispecialty satellite facilities; and home health care and hospice.

This release is available online at http://www.uphs.upenn.edu/news/News_Releases/aug05/HSCs.htm