New Delhi, India

In the genomes of the human body, some of the zombie viruses - which have been handed over from foreign DNA and passed to humans through generations - remain hidden and unnoticed. 

Advertisment

It was believed for a long time that they were inactive, but recent studies have suggested that these sequences of genes have the capability of wreaking havoc. 

The researchers, headed by University of Colorado bioinformatician Atma Ivancevic, discovered that cancers can make use of some of these zombie virus parts for their growth. 

Genome biologist and senior author Edward Chuong said, "Our study shows that diseases today can be significantly influenced by these ancient viral infections that until recently very few researchers were paying attention to."

Advertisment

These ancient genes, which were earlier dismissed as 'junk' DNA, are snippets of virus leftovers called endogenous retroviruses (ERVs) which are important for the existence of mammals because they spurred the evolution of the placenta. 

Also Read: 'Eureka moment': Scientists discover THIS common mouth bacteria can 'melt' cancer

However, not everything about ERVs is helping in the existence of humans. 

Advertisment

"We know that cancer cells express a lot of genes that are not supposed to be on, but no one really knows what is turning them on. It turns out many of the switches turning them on are derived from these ancient viruses," said Chuong.

How did the researchers find that ancient genes are pushing cancer?

The datasets on the epigenomes of 21 types of cancer were analysed by Ivancevic and her team, who stumbled upon a particular family of ERV called long terminal repeat 10 (LTR10) which was found to be active at very high levels. The researchers found that our primate ancestors were infected by the original virus around 30 million years ago.

The researchers carried out a functional study on a cell line of colorectal cancer tissues in which it was found that the expression of genes was regulated by LTR10 with established roles in the generation of tumours.

The undead LTR10 genes were taken out of action in human colorectal tumour cells and in mice, the genes which are known to lead to the growth of cancer, including XRCC4, were deactivated. 

Watch: Is the cure for pancreatic cancer near?

Ivancevic and his team found that LTR10 works as an epigenetic switch to control these genes. It was also discovered that cancer has been using this discarded virus to change patterns of gene expression in tumours. 

The researchers said these zombie viruses are likely to come back to life when human defences break down and lead to health problems. 

(With inputs from agencies)