Gene That Causes Cancer to Spread Is Identified
August 03, 2000
Star Tribune Company
It is a discovery scientists are hailing as a significant advance in understanding the molecular mechanisms that underlie why cancer cells stray. The consequences of that wanderlust, researchers estimate, ultimately lead to 90 percent of all cancer deaths.
The study is one of two reported in Wednesday's issue of the journal Nature that focus on cancer's spread -- metastasis -- and malignant melanoma, a deadly form of skin cancer.
The findings from both investigations hold promise of using gene-based data to stop the spread of cancer before it starts, medical experts say. One study focuses on the role of one gene in triggering spread of malignant melanoma. The second examines a host of genes involved in the cancer's metastasis.
"It is the metastatic cell, not the primary one that proves fatal to the patient," said Dr. Richard Hynes, director of the Cancer Research Center at the Massachusetts Institute of Technology.
Hynes and colleagues have identified the role of a gene dubbed rhoC, a significant trigger in the spread of some forms of malignant melanoma.
Using mouse and human cancer cell lines, Hynes and his team were able to elucidate how the gene triggered the cascade of events that allow a melanoma cell to migrate and invade.
The process of metastasis has been one of medicine's enduring mysteries. Cancer cells can evade the body's warrior cells and proteins and establish new, deadlier cancers far from the mother tumor. Hynes said not all cancer cells are capable of breaking from the primary tumor and burrowing through walls of tissue to reach the bloodstream, their conduit to new sites.
Cells that are metastatic not only hold the keys to escape, they are hardy enough to survive the buffeting of the blood. What makes a renegade cancer cell a survivor, Hynes said, is part of its mystery. It maintains its properties of adhesion, the biological glue that keeps all cells in their places, long enough to grow and divide in the original tumor. Then it loses those properties to break away. Metastatic cells regain their adhesion properties when they establish a new tumor elsewhere in the body.
RhoC, Hynes said, sheds new light on the processes of having, losing and regaining adhesion, one of the more confounding abilities of a rogue cancer cell.
Cholera: Scientists find secret of its genome
The genome of the bacterium that causes cholera has been decoded, paving the way for devising better vaccines and drugs against a killer that has caused seven pandemics since 1817.
With the genome sequenced, all of the bacterium's 3,885 genes are now open for inspection, giving biologists the basis for understanding every detail of the microbe's evolution and its tricks for surviving in such different conditions as the open ocean and the human gut.
Epidemics of the diarrhea-causing disease occurred regularly in the United States and other western nations before modern water-and sewage-treatment processes were developed in the late 19th century.
It remains "a living terror for people in the developing world, not a historical one," said Richard Gallagher, biological sciences editor of the journal Nature, which is publishing the findings today.
Cholera is one of nature's most efficient killers, sometimes killing within hours of onset. The bacterium attacks the intestine of humans and can cause death by severe dehydration resulting from diarrhea.
Most lives can be saved with modern rehydration therapy, but that often is not widely available in developing nations.
A half-million cases have been reported to the World Health Organization in the past two years with 20,000 deaths, said Claire Fraser of the Institute for Genomic Research in Rockville, Md., whose researchers analyzed the genetic structure of the bacterium.
The development is especially important in the potential production of vaccines, said John Mekalanos of Harvard Medical School. He said it provides an "open book" of the bacterium's structure, which will allow researchers to find and delete dangerous genes before using the bacteria to make vaccines.
-- The New York Times contributed to this report.
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