December 2004
Written by Brian Hansen & Catherine Anderson

Tags: technology, mutations

Feelin' Hot Hot Hot
You’re lounging at the beach, catching some rays, and the time comes to reapply your sunscreen so reach for your bottle of DNA 30.

DNA 30?

But before we get to DNA 30...

Sunscreen Basics
When you apply regular sunscreen, it reflects, absorbs, or scatters harmful ultraviolet rays, preventing them from entering your cells.

If you forget to apply your sunscreen, ultraviolet light from the sun causes damage to the skin cells by actually changing the structure of the DNA in them. The UV light ionizes DNA molecules in skin cells, causing bonds to form between adjacent pyrimidine bases (C and T), producing dimers. These dimers do not base pair normally so the dimers can cause distortion of the DNA helix, stalled replication, gaps, and misincorporation These mutations, called ‘photo lesions’, can cause transcription to stop, cell cycle arrest, or, in the extreme case, cell death. Less obvious but no less damaging are the increased mutations from replicating damaged DNA.

On the positive side, our cells have DNA repair systems to remove UV-damaged DNA. This mechanism won’t prevent sunburns or skin damage – you still need to use your sunscreen or wear protective clothing, but it does repair minor damage from day-to-day UV exposure.

The DNA 30 Connection
Researchers have found that introducing small bits of DNA – called thymidine dinucleotide (pTT) – can boost the cell’s repair pathways so they remove more of the damaged bits of DNA after UV exposure. It seems like the presence of pTT alerts the cell that damage is happening, putting the ‘repair crew’ on stand-by; so if any damage does happen, it is caught quickly.

Think of your skin as airport security…. always watching out for and preventing security risks. The pTT is like a security warning, making the airport security guards even more vigilant.

Testing...Testing
Researchers tried the pTT application on hairless mice prone to skin cancer. The mice received one week of daily pTT or nothing and then 3 weeks of daily UV exposure, with this cycle repeated for 24 weeks. Almost all of the mice (88%) in the untreated (or fake treatment) group had skin cancer compared to only 22% of the mice treated with pTT. Therefore, scientists are optimistic that pTT reduces UV-induced skin cancer. **

The research is still new; mice have different skin than humans – for one thing they don’t tan. Some similar results have been announced for guinea pigs who do tan, but scientists still need to conduct more studies to confirm these results and whether they can be applied to humans.

So don’t run out and try to buy your pTT-fortified sunscreen... just yet.

**This study was published in PNAS in March, 2004 (Goukassian et al. 2004. Topical DNA oligonucleotide therapy reduced UV-induced mutations and phocarcinogenesis in hairless mice. PNAS March 16, 2004, vol. 101 #11, pages 3933-3938)