Seaweed extract protects against cervical cancer: Algae compound surprisingly effective at preventing cancer-causing viral infection
13.jul.06
News @ Nature
Narelle Towie
http://www.nature.com/news/2006/060710/full/060710-12.html
Just a tiny amount of a common food additive has been found, in lab tests, to guard against the virus linked to cervical cancer.
Scientists have discovered that carrageenan, a compound extracted from red algae and used as a thickening agent in everyday products such as toothpaste and yoghurt, is highly effective at preventing the spread of the sexually transmitted human papilloma virus (HPV). The cheap ingredient was found to be effective at a concentration 100 times lower than the best HPV inhibitor currently on the market.
"We were screening different compounds for potential HPV inhibitors in vitro, and carrageenan, which is an inexpensive, widely available product, came up as being extraordinarily potent," says Douglas Lowy, a researcher with the National Cancer Institute in Bethesda, Maryland.
Carrageenan was already known to be an inhibitor against the AIDS-causing virus HIV, and is currently undergoing clinical trials for that.
The compound is also already used in a variety of sexual lubricants because of its gelling properties. Lowy and his colleagues, whose paper is published in the journal PLoS Pathogens1, found that some of these over-the-counter products are decidedly effective against HPV transmission in the test-tube.
Carregeenan, which is an inexpensive, widely available product, came up as being extraordinarily potent.
Douglas Lowy
National Cancer Institute, Maryland
"The exciting thing is it is already available in various lubricants," says Anne Szarewski, a clinical consultant for the Cancer Research UK Centre in London. The compound is easy to come by, and is classed as "generally regarded as safe" by the US Food and Drug Administration. "A topical microbicide may not actually be light years away from reality," says Szarewski.
But controlled clinical trials need to take place before any of the products could be recommended as HPV inhibitors, notes study leader Christopher Buck, also with the National Cancer Institute.
No entry
Carrageenan, Irish for 'moss of the rock', is produced by boiling red seaweeds found in abundance along the rocky coasts of North America and Europe.
Buck's team found that carrageenan acts like a border control, sticking to proteins on the human papilloma virus and preventing the virus from interacting with, or entering, the cells of the cervix.
It seems to have a protective effect with some other viruses too, including the cold-sore-causing herpes simplex virus (HSV), they report. But HSV has an extra protective membrane that makes it less susceptible to carrageenan; a dose a thousand times greater was needed to achieve equivalent protection against HSV as was achieved against HPV, the team says.
Another option for defeating HPV may be using a vaccine (see 'Cervical cancer vaccine comes closer to market'). But vaccines currently on their way to clinical use cost hundreds of US dollars, so are unaffordable in developing countries, where screening against cervical cancer is poor and many women die from the disease.
Double whammy
If carrageenan were added to an HIV microbicide, says head of the Indian Council of Medical Research N. K. Ganguly, it could form one of the best preventatives against sexually transmitted diseases available.
More than 5,000 women in South Africa are currently taking part in phase-three clinical trials of Carraguard, a vaginal gel containing carrageenan that has been designed to protect against HIV. These trials are due to end in 2007.
The team hopes that further trials will be designed to explicitly test the compound's effectiveness against HPV transmission. They are also working on developing a mouse model of HPV so that they can study it more closely in the lab.
References
1. Buck C. B., et al. PLoS Path. 2, e69. 0001 - 0010 (2006).