Unleashing the Potential: Progress in the Human Genome Project

The first draft of the human genome has been read and analyzed, revealing several surprises. For example, the genome only contains 30,000 to 40,000 genes, far fewer than the 100,000 estimate used for most of the last decade.

Now, the project has produced a 94% complete working draft of the human genome sequence. Each of the 3,164.7 million letters (nucleotides) of the sequence has been read 5 times on average. About 30% of the human genome has been sequenced with twice this redundancy, ensuring a high degree of accuracy in the final sequence. It is anticipated that all the human chromosomes will be sequenced in final form by 2003.

Findings have been continuously and freely released to the public within 24 hours of discovery, allowing scientific discoveries to advance even while the genome is being sequenced. About 33 disease genes have been discovered within the past year and a half. Many of the genes took many years to find, but with the tools now available, disease genes can be found within a few months and at a fraction of the cost.

The Human Genome Project has made possible a new way of understanding the process of cancer growth and metastasis. Thirty years have elapsed since President Richard Nixon declared war on cancer and called for a national commitment to find a cure. Along the way, scientists have amassed a wealth of information about how cancer works at the molecular and DNA level, providing important clues for selectively targeting new treatment strategies.

The May 2001 meeting of the American Society of Clinical Oncology (ASCO) in San Francisco provided glimpses into some of these new therapeutic options. Some of these therapies prevent a class of chemicals called growth factors from reaching a tumor, blocking signals that would otherwise instruct the cell to grow out of control. Others drive cancer cells to self-destruct. Still others block enzymes that cancer cells use to chew openings in normal tissues for room to expand. And, most famously, the class of compounds known as angiogenesis inhibitors keeps tumors from building new blood vessels to supply themselves with food and oxygen.

Unlike chemotherapy and radiation, which use carpet-bombing tactics that destroy cancer cells as well as healthy cells, pharmaceutical companies are designing new medicines that act like a troop of snipers, firing on cancer cells only and targeting the weak links described above. The drug Herceptin is one example though it seems to work with only a small percentage of all breast cancers. About 30% of women with breast cancer will overproduce a growth factor called HER2 that stimulates breast cancer growth. Herceptin latches onto breast cancer cells and prevents the uptake of HER2 thereby preventing tumor cell growth.

Researchers at the ASCO meeting discussed other promising new drugs now entering the clinical testing pipeline. One class of drugs under study is the COX2 inhibitors. Originally these drugs were developed to treat arthritis. Researchers have found that COX2, an enzyme, is over expressed in several human cancers including colon, head and neck, bladder, non-small cell lung and breast cancers. Early research suggests COX2 inhibitors may work to prevent cancer at very early stages of growth with the intent of lowering the risk of developing cancer to begin with.

Perhaps one day doctors and scientists will be able to identify exactly which genes are abnormal in any one person’s cancer and selectively prescribe a cocktail made up of the antibodies or small molecules specifically designed to fight against the abnormal products of those genes.

Philana Chen, MPH

Sharon Olsen, MS, RN