Cancer cells need normal, nonmutated genes to survive

May 28, 2009

Corrupt lifestyles and vices go hand in hand; each feeds the other. But even the worst miscreant needs customary societal amenities to get by. It's the same with cancer cells. While they rely on vices in the form of genetic mutations to wreak havoc, they must sustain their activity, and that requires equal parts vice and virtue.

According to a new study in the May 29 issue of Cell, rely heavily on many normal proteins to deal with stress and maintain their deviant state. Researchers at Harvard Medical School and Brigham and Women's Hospital used a technique called (RNAi) to dial down the production of thousands of proteins and determine which were required for cancer cell survival.

"Cancer cells actually leverage many genes that don't harbor mutations to maintain their malignant lifestyles," says first author and postdoctoral researcher Ji Luo. "These genes probably help them deal with the problems that develop as a result of the inappropriate presence of growth and survival signaling in tumor cells."

Being a cancer cell isn't easy. Think of all the and involved, not to mention the abnormal architecture of a tumor, which deprives cells of oxygen. Survival requires a complete kit of tools.

"Researchers often characterize cancer cells as oncogene addicts, but they're just as reliant on normal genes that alleviate stress," explains senior author Stephen Elledge, a professor at HMS and Brigham and Women's Hospital. "These stress management genes deserve attention as potential therapeutic targets."

In recent years, the National Cancer Institute has supported an ambitious effort to understand the molecular basis of cancer by sequencing cancer genomes. Elledge and Luo note that this Cancer Genome Atlas project would miss the stress management genes.

"If these genes are intact, they won't stand out when you compare the of cancer cells with normal cells," says Luo.

So the team took a different approach to test their "non-oncogene addiction" hypothesis. They acquired two human cell lines, identical in every way except for one—the presence or absence of a Ras oncogene. Ras mutations are prevalent in many deadly cancers, and researchers have not been successful in developing drugs against the dangerous gene.

The team used molecules called shRNAs to interfere with the production of thousands of normal, healthy proteins in the two cell lines. They gave the cells time to divide and sifted through the data to determine which proteins were required for survival. (In the past, labs relied on large robots to complete these types of screens, but Elledge and others have refined the technology in an effort to make RNAi affordable and accessible. Luo conducted his genome-wide screen in test tubes without the aid of a robot.)

Despite their similarities, the two cell lines responded differently to a number of shRNAs. That is, normal cells tolerated low levels of a particular protein while cells with the Ras mutation perished. Luo validated 50 of these hits in a second pair of cell lines. Dozens of these represent brand new therapeutic targets.

"This opens the door to using a drug cocktail approach to treat tumors driven by Ras mutations," says Elledge, who is also an investigator with Howard Hughes Medical Institute. "We might be able to tinker with the levels of these proteins and cripple cancer cells without hurting normal in the body, though this needs to be tested in tumor models."

"This type of functional approach complements the physical mapping of cancer genomes, but provides a much more direct path to new anti-cancer drug targets," adds Luo. "The genes that are critical for maintaining the malignant state will really crystallize when we combine forces."

Source: Harvard Medical School (news : web)

Explore further: Study shows epigenetic changes can drive cancer

add to favorites email to friend print save as pdf

Related Stories

New cancer gene found

May 08, 2008

Researchers at the OU Cancer Institute have identified a new gene that causes cancer. The ground-breaking research appears in Nature’s cancer journal Oncogene.

Cancer cells more likely to genetically mutate

Feb 19, 2007

When cells become cancerous, they also become 100 times more likely to genetically mutate than regular cells, researchers have found. The findings may explain why cells in a tumor have so many genetic mutations, but could ...

Neuronal regulators offer potential targets for cancer

Mar 19, 2008

Being too brainy can be a bad thing in a junior high cafeteria, where the social hierarchy favors other traits. "Braininess" also causes problems for cells. When a breast cell begins making the proteins normally produced ...

Recommended for you

Study shows epigenetic changes can drive cancer

1 hour ago

Cancer has long been thought to be primarily a genetic disease, but in recent decades scientists have come to believe that epigenetic changes – which don't change the DNA sequence but how it is 'read' – also play a role ...

Clearing cells to prevent cervical cancer

16 hours ago

A study published online in the International Journal of Cancer earlier this month describes a novel approach to preventing cervical cancer based on findings showing successful reduction in the risk of cervical cancer after ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

jsovine
not rated yet May 28, 2009
I think methods like this will eventually cure cancer as we know it
Birger
not rated yet May 29, 2009
I think methods like this will eventually cure cancer as we know it


.....Or at least turn cancer into a manageable chronic disease. Remember, cancer is not one disease, it is a hundred different diseases, and one single tumor will mutate and metastaze until the daughter tumors are quite different.