( Many cancers arise due to defects in ge...)Reactivated gene shrinks tumors

The study offers evidence that the tumor suppressor gene p53 is a promising target for human cancer drugs.

"If we can find drugs that restore p53 function in human tumors in which this pathway is blocked, they may be effective cancer treatments," said David Kirsch of MIT's Center for Cancer Research and Harvard Medical School, one of the lead co-authors of the paper.

The study will be published in the Jan. 24 online edition of Nature. It was conducted in the laboratory of Tyler Jacks, director of the Center for Cancer Research, the David H. Koch Professor of Biology and a Howard Hughes Medical Institute investigator.

P53 has long been known to play a critical role in the development of many tumors-it is mutated in more than 50 percent of human cancers. Researchers have identified a few compounds that restore p53 function, but until now, it has not been known whether such activity would actually reverse tumor growth in primary tumors.

The new MIT study shows that re-activating p53 in mouse tumors dramatically reduces the size of the tumors, in some cases by 100 percent.

"This study provides critical genetic evidence that continuous repression of a tumor suppressor gene is required for a tumor to survive," said Andrea Ventura, an Italian postdoctoral associate in the Center for Cancer Research and first author of the paper.

In normal cells, p53 controls the cell cycle. In other words, when functioning properly, it activates DNA repair mechanisms and prevents cells with damaged DNA from dividing. If DNA damage is irreparable, p53 induces the cell to destroy itself by undergoing apoptosis, or programmed cell death.

When p53 is turned off by mutation or deletion, cells are much
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Source:Massachusetts Institute of Technology