Our Science – Liu Website

Zheng-Gang Liu, Ph.D.

Cell and Cancer Biology Branch Senior Investigator 37 Convent Drive Room 1066 Bethesda, MD 20892 Phone:   301-435-6351 Fax:   301-402-1997 E-Mail:   zgliu@box-z.nih.gov

Biography

Dr. Liu received both his bachelor's and master's degrees in biochemistry from Peking University, People's Republic of China. He completed his Ph.D. training in Dr. Larry Schwartz's laboratory at the University of Massachusetts in 1995 and carried out his postdoctoral training in the laboratory of Dr. Michael Karin at the University of California, San Diego. He joined the former Department of Cancer and Cell Biology, Medicine Branch, DCS, in 1998. His research interests have focused on the molecular mechanisms of apoptosis.

Research

Molecular Mechanisms of TNF Signaling and Apoptosis

The research goal of our laboratory is to understand the molecular mechanism of tumor necrosis factor (TNF) signaling and the regulation of apoptosis.

TNF Signal Transduction. TNF is a proinflammatory cytokine that plays a critical role in diverse cellular events. Upon TNF treatment, cells could undergo proliferation, differentiation, and apoptosis. In a previous study, we found that the activation of transcription factors NFkappB and AP-1 as well as the induction of apoptosis are mediated by three distinct pathways in response to TNF. While the adaptor molecule FADD mediates apoptosis, the death domain kinase RIP and the TNF receptor-associated factor TRAF2 are essential for NFkappB and AP-1 activation. Because it is unknown how RIP and TRAF2 regulate the NFkappB and AP-1 activation, we are investigating the mechanism by which RIP and TRAF2 activate their downstream kinases-namely, IKK and JNK1-with the combination of biochemical and cellular approaches.

Regulation of Apoptosis. Apoptosis (programmed cell death) is a common phenomenon during development and occurs to eliminate harmful or unwanted cells from the organism. Apoptosis is the crucial process for organisms to keep their cellular homeostasis. Deregulation of apoptosis is involved in many diseases; for instance, inefficient apoptosis has been found in many different cancers. Since all cells have the genetic machinery required to commit suicide, the ability to selectively regulate this process has profound implications for treating disease. Because more and more evidence indicates that irregular cell growth often leads to apoptosis, we believe that in addition to promoting growth signals, inactivation of apoptosis is essential for normal cells to become tumor cells. This can be achieved by either increasing a signal that actively blocks apoptosis or generating a defective mutation in the cell death machinery. Identification of these apoptosis-inactivating targets in different cancers will greatly enrich our knowledge about tumorigenesis and help to develop new cancer therapies.

One of our research interests is to identify the genes that protect cancer cells from apoptosis and, upon understanding the mechanisms of their actions, to develop new cancer therapies. To do so, we use TNF-mediated apoptosis as a model system. It is known that the activation of NFkappB protects cells from apoptosis induced by TNF and many chemotherapeutic agents. While we continue to study the regulation of TNF signal transduction, we also like to understand the mechanism of the transcription factor NFkappB-mediated antiapoptotic effect. Using several different approaches including microarray, we have identified some candidate genes which may protect cells from apoptosis. Currently we are further testing their antiapoptotic effect. Because NFkappB activation protects cells against apoptosis and also is essential for the development of several types of cancer, the identification of the antiapoptotic genes activated by NFkappB will provide new targets for developing new cancer therapies. Inhibition of the functions of these antiapoptotic genes may result in apoptosis of cancer cells and lead to cure of the disease.

This page was last updated on 7/31/2008.