If you've ever seen a photo or drawing of DNA, you're probably familiar with the famous double helix of genetic material that forms the building blocks of life. Now scientists at the Cambridge Institute and the University of Cambridge in the U.K. have discovered DNA with four helices hidden within human cancer cells. They describe the new quadruple-stranded DNA helix this week in the journal Nature Chemistry.

The quadruple DNA forms a square structure and appears to be created temporarily when cancer cells are preparing to divide. The researchers say future cancer treatments that targeted these quadruple helices would theoretically leave healthy cells unharmed.

The research was supervised by Shankar Balasubramanian, a professor of chemistry at the University of Cambridge whose lab focuses on the chemical biology of nucleic acids ("DNA" is short for for deoxyribonucleic acid). He tells New Scientist that this new discovery challenges the common wisdom that the structure of DNA is fully understood.

Scientists first started creating and seeing quadruple DNA in laboratory conditions several years ago, but this is the first time that they have been observed in live tissue. "We've come a long way in 10 years, from simple ideas to really seeing some substance in the existence and tractability of targeting these funny structures," Balasubramaninan told the BBC. "I'm hoping now that the pharmaceutical companies will bring this on to their radar and we can perhaps take a more serious look at whether quadruplexes are indeed therapeutically viable targets."

So how would this new discovery potentially be used in cancer treatments? Normal DNA is comprised of four base chemical groups called nucleotides: adenine, cytosine, thymine and guanine. This last nucleotide is present at above-normal quantities in the quadruple DNA. The paper's lead author, Giulia Biffi, a third-year PhD student in Balasubramanian's lab, used antibody proteins with a fluorescent marker that linked to guanine to reveal the quadruple DNA in human cancer cells. They then used a molecule called pyridostatin to temporarily "trap" the quadruple helices in place. If the scientists could identify and trap the unusual DNA in this manner, it is theorized that a cancer drug could be developed to target the cells in the same manner.

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