User Tools (skip):
Damaged DNA? Take vitamin D
Good news for sun worshippers sick of lathering on layers of sunscreen every summer: sunlight may actually help prevent cancer, according to a recent study.
PHOTO: Claudio Calligaris
Sunlight, specifically ultraviolet light, is a known culprit behind skin cancer. However, in moderate amounts it is beneficial in that it stimulates the production of vitamin D in the body. According to physiology professor John White's research, vitamin D appears to have some important cancer-fighting properties.
"Our results suggest that enhanced production of vitamin D3 ... helps stimulate mechanisms that repair DNA," says White.
According to White, the discovery has some potential as a cancer prevention measure. White's research had its genesis in a phone call from Dr. Martin Black, an oncologist and ear, nose and throat surgeon at the Jewish General Hospital. Black wanted to look into possible treatments to prevent or limit secondary squamous tumours, tumours characterized by flat, scale-like cells, in his patients. The hope was not to treat cancers after they occur, but to prevent, or at least limit, their growth in the first place.
"In this type of cancer, what is important is chemoprevention," explains White. "You're closing the door before the horse has bolted."
A major difficulty with chemoprevention is to find a drug that will be well tolerated by a patient over time. In some senses, vitamin D, produced as it is by the body, stands out as an excellent candidate. However, it has drawbacks as well.
Vitamin D's normal role in the body is to help distribute calcium, which is why it is added to milk in North America. Too much vitamin D, though, and a patient can become hypercalcemic.
"The active form of vitamin D gets in the way because at the concentrations where it exerts an anti-cancer effect, it also exerts side effects... It mobilizes the body's calcium too much," notes White.
For this reason his team, with funding from the Canadian Institutes for Health Research, treated cancer cell cultures and mice with a compound called EB1089, which is a vitamin D analogue. White and his collaborators, who included Black and Dr. Moulay Alaoui-Jamali from the Jewish General, found that this compound worked better than vitamin D at limiting cancer growth while not having a hypercalcemic effect.
The question they next had to address is: How do Vitamin D and its analogues work?
"In vitamin D-treated cells, you get more expression of the GADD 45 protein, which means you will have an enhanced capacity of the cell to repair damage to its DNA," says White.
GADD stands for Growth Arrest and DNA Damage. As the name implies, this protein inhibits the growth of cells, and stimulates repair of damage to cellular DNA. Both of these are important for cancer treatment, both limiting the growth of mutations in cells and preventing further mutations.
"The net result is inhibition of cell growth, but also enhanced capacity of a cell to repair its DNA, which is ideal for a chemoprevention plan," says White.
Although his research focused on head and neck squamous tumours, White suspects his team's discovery can be applied to numerous forms of cancers.
Since EB1089 is cheap and easy to administer, he believes that, at some point, it might be feasible that we will have dietary supplements containing vitamin D analogues as an easily affordable cancer prevention treatment. And of course, there is always the sun.