GENE ROADMAP HOLDS DIRECTIONS TO ADDICTION, CANCER

LONDON (Reuters) - Like tourists poring over a map to find their way around
an unknown city, scientists will be scrutinizing the sequencing of the
human genome published on Monday for directions to the causes of disease.

The human genetic map, or book of life, isn't completely finished. A few
major roads or chapters are still missing, but it is already showing
researchers new routes to understanding what makes us who we are.

"It essentially provides a roadmap of the genes that are present in
humans," Eric Nestler, of the University of Texas Southwestern Medical
Center in Dallas, said in a telephone interview.

"The way to look at the genome sequence is not as an end result in itself
but more as a road map to help us identify genetic abnormalities that
comprise risk for addiction and many other diseases."

Like cancer and heart disease, addiction to alcohol and drugs can be
inherited. Medical research suggests that about 50 percent of the risk of
addiction is genetic.

"That would make addiction more heritable than diseases we commonly think
of as genetic, such as adult onset diabetes or common hypertension,"
Nestler, the head of the department of psychiatry at the university, added.

But so far scientists haven't been able to identify any genetic
abnormalities in humans that contribute to the risk of addiction in humans.

About 100 genes and their products have been shown to influence the process
by which animals become addictive. Nestler believes the sequencing of the
human genome, as well as the completed genomes of the mouse and rat which
are expected soon, will narrow the search.

Profound Implications For Addiction

When the genes are found, he predicts they will have profound implications
for preventing addiction and treating it.

People at risk could be targeted for more intense intervention to protect
them from becoming addicted to alcohol or drugs, and those who already are
could be provided with more effective treatments than are currently available.

"It is only when you understand a syndrome biologically and identify the
root causes of the illness can you identify truly definitive treatments,"
Nestler said.

The destinations, or diseases, will be different but Nestler said the
routes to get to the cause of them will be the same and will be mapped out
in the genome sequence. Like addiction, cancer -- the most common genetic
disease -- has it origins in DNA.

"All cancers are caused by abnormalities in DNA sequence," said Dr. Michael
Stratton, the head of Britain's Cancer Genome Project.

One in three people in the western world will develop cancer and one in
five will die from the disease, so the search to find the maybe 20 abnormal
genes in any of the 200 types of cancer is a daunting task, but one that
will be facilitated by the genome sequence.

Stratton, who was one of the scientists who identified the BRCA2 breast
cancer gene, and his team have been comparing the draft human genome and
cancer genome sequences for new cancer genes.

He said the finished sequence of the human genetic code will be a
structural framework for a new generation of massive-scale comparisons of
cancer cell and normal genomes.