June 18, 2009

Researchers Discover New Link Between Genetics And Cancer

In the first ever development of its kind, cancer researchers announced on Wednesday that they have discovered a connection between cancer and a type of genetic mutation that results in either missing or redundant pieces of DNA.

The genetic defect, known as a copy number variation, was discovered in neuroblastoma cells, a form of pediatric cancer responsible for some 15 percent of all cancer-related deaths in children.

A group of researchers at the Children's Hospital of Philadelphia found that a copy number variation (CNV) on chromosome 1 can significantly influence the development of the often deadly disease which most frequently affects infants.

In this case, the CNV involves a segment of missing DNA from a stretch of the chromosome containing genes that are critical in the development of the body's nervous system.  The absent DNA was found on one gene in particular that is responsible for regulating the production of the product of another gene.

"This is a brand new area -- we never suspected that this family of genes played a role in neuroblastoma," said project leader John Maris in a phone interview with AFP.

Last year Maris and his colleagues were able to isolate another important gene, known as ALK, which is responsible for a much rarer hereditary version of the cancer.

The new research, published in the British journal Nature, sheds light on mutant versions of another gene involved with the disease's development known as BARD1.  Though the mutated gene increases a child's likelihood of getting the disease far less dramatically than the ALK gene, scientists say the discovery is critical in that it has revealed an entirely new kind of role for genes in influencing the onset of cancer. 

Researchers had for some time hypothesized that CNVs likely played a role in leading to certain kinds of cancer, but hard evidence to corroborate their suspicions had been lacking.

"The achievement here was proving the hypothesis that CNVs do, indeed, predispose to this pediatric cancer," explained Maris.

"We can infer that it's not just going to be true for neuroblastoma. My expectation is that there will be many reports following on this of similar types of associations in other cancers," he added.

The team's research has also reiterated the incredible complexity and elusive nature of hereditary diseases.  A majority of diseases that are commonly described as hereditary are actually the result of intricate interactions between genetic and environmental factors, making it nearly impossible to say which diseases are purely inherited. 

Very few diseases actually fall under the rubric of Mendelian inheritance, meaning that a single gene inevitably leads to the development of the disease.

"Like all human cancers, a small percentage of neuroblastoma runs in families"”usually one or two percent"”and the rest seemingly occur by chance," explained Maris.

"The genome-wide association field is showing that it is not chance. There actually is a genetic susceptibility, but it takes a perfect storm of inheriting the right mix of these risk factors from Mom and Dad."

Notwithstanding differences between countries, global statistics show that on average approximately one in every ten-thousand children under the age of 15 develop  neuroblastoma, the vast majority of which occur in infants and toddlers under the age of 3.


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