Which DNA is linked to pediatric cancer?

Mysterious rings of DNA -- known as extrachromosomal circular DNA -- may contribute to cancer development in children, according to a study which may lead to better diagnosis methods for pediatric cancer.

Chromosomes are threadlike structures of DNA and protein found in the nucleus of most living cells, and carry genetic information in the form of genes.

The current study, published in the journal Nature Genetics, probed into enigmatic rings of DNA that is not present in the chromosomes.

While cancer is associated with the gradual accumulation of defects in the genetic material Deoxyribonucleic Acid (DNA) over time and is considered an age-related disease, the researchers, including those from the Charite – Universitatsmedizin Berlin in Germany, sought to know why children develop the malignant disease.

According to the researchers, a range of external factors such as tobacco smoke and radiation may cause damage to the DNA within cells.

Accumulation of these damages over many years, they said, may lead to cells losing control over their replication and growth, resulting in cancer.

However, the current study noted that extrachromosomal DNA can disrupt genetic information, contributing to cancer development.

While scientists have known about these circular DNA for years, the current study noted that relatively very little has been understood about their functions due to the lack of sufficient technology to analyse them.

As part of the study, the researchers applied advanced techniques to analyse the chemical structure and sequence of these mysterious DNA molecules using leading bioinformatics algorithms.

In the process, they have obtained the first-ever detailed mapping of circular DNA in neuroblastoma -- a deadly childhood tumour.

Analysing neuroblastoma tissue samples from a total of 93 children, the researchers revealed that the prevalence and diversity of circular DNA is far greater than previously anticipated.

According to the study, each tissue sample contained on average 5,000 circular DNA copies.

The findings described the process by which specific DNA sections separate from a chromosome to form circular DNA before reintegrating into the chromosome at a different location.

"This can potentially cause cancer if it results in the original sequence of genetic information being disrupted," explained study co-author Anton Henssen, a researcher at the German Cancer Consortium (DKTK) in Germany.

According to the researchers, the current study offers an insight into how even young cells, like those found in children, can transform into cancer cells.

"We were also able to show that certain types of circular DNA may accelerate neuroblastoma growth," said Richard Koche, study co-author from the Memorial Sloan Kettering Cancer Center in the US.

Koche added that testing for the presence of these circular DNA molecules may make it easier to predict the course of cancer.

"Additionally, studying this process in the relatively quiet genomes of these pediatric tumours may help illuminate similar mechanisms which were previously missed in more complex adult cancers," he added.

The researchers said the current study may also have implications for a broad range of tumour types and associated clinical outcomes.