The Cancer Genome Atlas Project

On 26th June 2000, following 10 years of work, British Prime Minister Tony Blair and US President Bill Clinton announced that scientists had unveiled a rough draft of the human genome. In May 2006, the publication of the sequence of the last, and largest, human chromosome – chromosome 1 – marked the effective completion of the Human Genome Project (HGP).

What scientists have effectively produced, however, is a map of where all the genes are, and on which chromosomes they reside. The vital work of exploring the function of all these genes, and how genetic mutations can affect people’s chances of developing particular diseases remains to be done.

Interest is particularly intense in cancer research. Obviously, environmental factors and lifestyle choices play a large role in determining how likely someone is to develop a particular cancer, but genetic factors are important as well.

Many of the genes that promote the transformation of healthy cells into cancer cells have already been identified, and this has often led to new drugs. For example, the HER2 gene was found to be responsible for increased aggression in some cases of breast cancer: as a result, the breast cancer drug Herceptin, which inhibits this protein, was created.

However, the relationships between gene mutations and cancer are often highly complex. There are a variety of different mutations, none of which is harmful on its own, but they combine to turn a cell to the dark side. These mutations may be quite different among different patients with the same cancer.

This is where The Cancer Genome Atlas (TGCA) comes in. HGP provided a map of the genome of a healthy volunteer (or, more precisely, a composite of several different people). TGCA aims to sequence the genomes of the tumour cells of a large sample of patients with the same cancer, looking for genes which are often mutated. This is obviously a much larger undertaking than HGP and would not be possible were it not for the huge decrease in the time taken and cost required to sequence genomes since then.

At present, three-year pilot studies are underway in three cancers: lung cancer, ovarian cancer and glioblastoma (the type of brain cancer with which Senator Kennedy has been diagnosed). These aim to determine if preparing a complete encyclopaedia of cancer-causing genetic mutations is feasible.

The first results from the glioblastoma study were recently published in Nature. The researchers announced that three genes not previously linked to glioblastoma seem to be consistently mutated. One of these is thought to explain the resistance that some glioblastoma patients show to chemotherapy drugs.

The decision about whether to proceed with the full-scale project will be made at the end of the three years. In the meantime, we can hope to learn a lot about three particularly nasty cancers.