Cancer Patient´s DNA Sequenced for the First Time in History

Researchers decoded the complete DNA sequence of a patient suffering from a specific type of cancer (acute myelogenous leukemia). The objective of the study was to identify the genetic mutations that led to the disease. But it's hoped that the genetic sequencing technique that the scientists used could be applied to many other cancers. The study was published in the Nov 6th 2008 issue of Nature.

In this study the scientists examined two samples from the woman. One was taken from healthy skin cells and the other from her bone marrow which contained cancerous cells. The genetic sequence of both samples was elucidated and compared for any differences, that is nucleotide base differences in the DNA. Using sophisticated software researchers identified 10 mutations. Only two of these had been linked to the disease before.

Of these mutations 80% were "rare" and had never been associated with acute myelogenous leukemia. Also, they found that every cell in the tumor had 90% of the key mutations. Their gene sequencing approach clearly identified the genetic mutations responsible for this cancer. Three of the genetic mutations were in genes that suppressed tumour growth and four were in genes linked to the spread of cancer.

Acute myelogenous leukemia (AML) is a cancer of the blood-forming cells in the bone marrow. It is poorly understood, although a genetic background has always been suspected. Experts estimate that 13,000 of new cases of AML are diagnosed in the United States each year. More than 8000 people die from this type of cancer.

Interestingly, scientists in this study searched through an amazing 3 billion pairs of chemical bases to find the genetic mutations that caused the cancer. Earlier work had involved sequencing certain genes suspected to be associated with cancer but never a full side-by-side comparison of the DNA of a cancer cell with normal (non-cancerous) cells.

There are always stories in the media about new breakthroughs in cancer research, and it's sometime hard to discern which ones really will help. This study has been hailed by several eminent scientists as a major landmark in cancer research and it highlights the importance of sequencing entire genomes to discover new cancer-related mutations.

Although it may not be applicable to every type of cancer, studies such as this one will, according to lead author Timothy Ley, M.D., be the basis for "more effective ways to diagnose and treat cancer."

Nature. www.nature.com