Scientists decode complete DNA of cancer patient

November 6th, 2008 - 4:11 pm ICT by IANS  

Washington, Nov 6 (IANS) Scientists have decoded the complete DNA of a cancer patient and traced her disease, acute myelogenous leukemia, to its genetic roots.A team at the Washington University’s Genome Sequencing Centre (GSC) in St. Louis sequenced the genome of the woman in her 50s who died and the genome of her leukemia cells, to identify genetic changes unique to her cancer.

What is striking is that these scientists were able to sift through the three billion pairs of chemical bases that make up the human genome to pull out the mutations that contributed to the patient’s cancer.

The pioneering work sets the stage for using a more comprehensive, genome-wide approach to unravel the genetic basis of cancer.

“Our work demonstrates the power of sequencing entire genomes to discover novel cancer-related mutations,” said co-author Richard K. Wilson, director of Washington University’s GSC.

“A genome-wide understanding of cancer, which is now possible with faster, cheaper DNA sequencing technology, is the foundation for developing more effective ways to diagnose and treat cancer,” Wilson added.

The researchers discovered just 10 genetic mutations in the patient’s tumour DNA that appeared to be relevant to her disease; eight of the mutations were rare and occurred in genes that had never been linked to AML.

They also showed that virtually every cell in the tumour sample had nine of the mutations, and that the single genetic alteration that occurred less frequently was likely the last to be acquired. The scientists suspect that all the mutations were important to the patient’s cancer.

Like most cancers, AML - a cancer of blood-forming cells in the bone marrow - arises from mutations that accumulate in people’s DNA over the course of their lives.

However, little is known about the precise nature of those changes and how they disrupt biological pathways to cause the uncontrolled cell growth that is the hallmark of cancer.

Previous efforts to decode individual human genomes have looked at common points of DNA variation that may be relevant for disease risk, according to a release of Washington University (WU).

“Until now, no one has sequenced a patient’s genome to find all the mutations that are unique to that person’s disease,” said first co-author Timothy Ley, hematologist and professor of Medicine at WU. “We didn’t know what we would find, but we felt that the answers to why this patient had AML had to be embedded in her DNA.”

The study appeared in the Thursday issue of Nature.

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