DUARTE, Calif., November 20, 2008 — Researchers have discovered an enzyme repairs DNA only in the mitochondria of cells which may hold the key to understanding the genetic origins of cancers. The research team’s work, led by City of Hope’s Li Zheng, Ph.D., staff scientist, and Binghui Shen, Ph.D., professor and director of radiation biology, was published in a recent issue of the journal Molecular Cell. Shen was also awarded a $2 million research grant from the National Cancer Institute to continue his studies into mitochondrial DNA and the enzyme DNA2, which manages repairs and replication.

Mitochondria are self-contained mini-organs, or organelles, within cells that act as generators to provide cells energy and control cell metabolism. Previous research into mitochondria has revealed that they may be important to the development of cancer. The role mitochondria may have in cancer development has been difficult to study, but the discovery by Shen’s lab that the enzyme DNA2 is only found in mitochondria could lead to new investigation.

“Mitochondria have their own separate DNA to control its own operation, and if that DNA gets damaged, it can lead to cell death or diseased cells like those seen in cancer,” said Shen. “The discovery of DNA2’s exclusive role in repairing mitochondrial DNA offers us the opportunity to control and study the role of mitochondrial damage on cancer development.”

In most organisms, from yeast to frogs, DNA2 repairs DNA in both the nucleus and mitochondria, but in humans, DNA2 works exclusively in mitochondria. Because human DNA2 only repairs mitochondrial DNA and not DNA in the nucleus, Zheng and Shen recognized its value for experiments, since they could control the amount of DNA damage in mitochondria. It gives them a tool to study how the organelle influences cancer development.

“Identifying the exclusive region of DNA2 activity is only a first step,” said Shen. ”I am hopeful that the discovery will lead to a useful model to study the role mitochondria play in cancer as well as other diseases.”