Scientists crack cancer genome

December 17th, 2009 - 1:21 pm ICT by ANI  

London, Dec 17 (ANI): Scientists from UT Southwestern Medical Centre claim to have unravelled the entire cancer genome that would help to better understand the disease and develop new therapies.

All cancers are caused by damage to genes — mutations in DNA — that can be triggered by environmental factors such as tobacco smoke, harmful chemicals or ultraviolet radiation, and causes cells to grow out of control.

Working in collaboration with scientists from the Cancer Genome Project in the United Kingdom, the research team focussed on small-cell lung cancer (SCLC).

Using new DNA sequencing technology called “massively parallel sequencing,” the researchers searched the DNA sequences for differences between tumour and normal cells and found more than 23,000 mutations that the tumour cells had acquired.

The study also led to the discovery of a new gene involved in lung cancer named CHD7.

“Cancer is driven by acquired mutations in genes, and we are at a point where it soon will be possible to actually know every mutation in the tumors of each of our patients,” said Dr. John Minna, director of the Nancy B. and Jake L. Hamon Center for Therapeutic Oncology Research at UT Southwestern and one of the authors of the new study.

He said that the number of mutations suggests that a person may develop one mutation for every 15 cigarettes smoked.

When the researchers analyzed the 23,000 mutations, they found distinctive patterns associated with the cocktail of carcinogens present in cigarette smoke.

The DNA sequence of the cancer cells also revealed that the cells had attempted to repair their smoke-damaged DNA using two mechanisms, but the cells were only partially successful.

Cigarette smoke deposits hundreds of chemicals into the airways and lungs. The longer one smokes and the more cigarettes smoked each day, the higher the risk of developing lung cancer and mutations.

“By applying the same approach to other cancers not associated with cigarette smoking, including the very large group of people who develop lung cancer but have never smoked, it may be possible to discern which carcinogens play a role in those other cancers as well,” said Adi Gazdar, professor of pathology in the Hamon Centre at UT Southwestern.

“The data demonstrate the power of whole-genome sequencing to untangle the complex mutational signatures found in cancers induced by cigarette smoke,” said Minna.

“In addition, the protein product of the CHD7 gene now becomes a new marker for early diagnosis and also for potentially targeted therapy,” he added.

The study appears in journal Nature. (ANI)

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