A SMALL daily dose of Viagra has been shown to significantly reduce colorectal cancer risk in an animal model.
Research carried out on mice genetically predetermined to have the third leading cause of cancer death in the US, showed that Viagra cut in half the formation of polyps - an abnormal and often asymptomatic clump of cells on the lining of the intestines that may become cancer.
Darren Browning, a researcher at the Georgia Cancer Centre at Augusta University, said the next steps should include a clinical trial for the drug in patients considered at high risk of colorectal cancer, such as those with a strong family history, multiple previous polyps and chronic intestinal inflammation like colitis.
Dr Browning said Viagra has been used safely for years in a wide range of doses and age groups, from premature infants with pulmonary hypertension to the elderly with erectile dysfunction.
When placed in the drinking water, the study team found Viagra reduced polyps in a mouse model with a genetic mutation that occurs in humans, causing them to produce hundreds of polyps starting as teenagers and essentially always resulting in colorectal cancer.
"Giving a baby dose of Viagra can reduce the amount of tumours in these animals by half," Dr Browning said.
Viagra is best known for its ability to relax the smooth muscle cells around blood vessels so the vessels can more easily fill with blood, which is how it helps both erectile dysfunction and pulmonary hypertension.
But Dr Browning's lab is showing that it also increases levels of the chemical cyclic GMP, which is known to affect the intestinal lining, the epithelium.
While the details of just how remain unclear, Dr Browning and his team have seen that the results of increased cyclic GMP include suppression of some of the excessive cell proliferation that occurs in the gut and an increase in normal cell differentiation as well as the natural elimination of abnormal cells, through a process called apoptosis.
"When we give Viagra, we shrink the whole proliferating compartment," Dr Browning said.
Colorectal cancer is the third most commonly diagnosed cancer in the US, according to the National Cancer Institute and American Cancer Society.
