Scientists pinpoint gene coding errors for cancer

The biggest-ever trawl of the human genome for cancer-causing DNA errors has netted more than 80 tiny mutations, a finding that could help people at high risk, researchers said Wednesday.

The results, which double the number of known genetic alterations linked to breast, ovarian and prostate cancer, were unveiled in a dozen scientific papers published in journals in Europe and the United States.

The three hormone-related cancers are diagnosed in over 2.5 million people every year and kill one in three patients, said a Nature press statement.

Teams from more than 100 research institutes in Europe, Asia, Australia and the United States said the work should in the future help doctors to calculate an individual's cancer risk long before any symptoms emerge.

People with high-susceptibility mutations could be counselled against lifestyle choices that further increase their risk, given regular screening and drug treatment, or even preventative surgery.

"We have examined 200,000 areas of the genome in 250,000 individuals. There is no (other) study of cancer of this size," Per Hall, coordinator of the Collaborative Oncological Gene-environment Study (COGS), told AFP of the research.

The studies compared the DNA of more than 100,000 patients with breast, ovarian and prostate cancer to that of an equal number of healthy individuals. Most were of European ancestry.

DNA, the blueprint for life, comprises four basic chemicals called A (adenine) C (cytosine), T (thymine) and G (guanine) strung together in different combinations along a double helix.

Researchers noted where the A, C, T, G combinations of cancer patients differed significantly from those of healthy people.

They were looking for a tiny "spelling mistake" in the code, called a single nucleotide polymorphism or SNP that can cause problems in gene function.

For breast cancer, the researchers found 49 SNPs, "which is more than double the number previously found", said Sweden's Karolinska Institutet, which took part in the giant study.

"In the case of prostate cancer, researchers have discovered another 26 deviations, which means that a total number of 78 SNPs may be linked to the disease."

For ovarian cancer, eight new SNPs were found.

Everyone has inherited alterations in their DNA, but whether these mutations are dangerous or not is determined by where on the code they lie.

And carrying a mutation does not necessarily mean a person will develop cancer, a disease that may have multiple causes.

The researchers said further study is needed to allow scientists to translate these DNA telltales into tests for predicting cancer risk. A more distant goal is using the knowledge for better treatments.

"Since there are many other factors that influence the risk of these cancers (mainly lifestyle factors), future tests have to take more risk factors than just genes into consideration," said Hall.

"It will take a couple of years before we have the necessary models enabling us, with high accuracy, to predict the individual risk of these cancers."

The findings were published in Nature Genetics and Nature Communications, PLOS Genetics, the American Journal of Human Genetics and Human Molecular Genetics.

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