[WLA] Mixed news on new ways to prevent colon cancer
Monday August 31, 5:41 pm Eastern Time
WASHINGTON, Aug 31 (Reuters) - Researchers said on Monday they had good news and bad news on ways to treat and even prevent colon cancer.
They said drugs believed to help prevent colon cancer do indeed seem important in the development of tumors -- but reported conflicting evidence on whether the drugs prevent it or make it worse.
The research casts more doubt on whether the new diabetes drug troglitazone, sold under the name Rezulin by Warner-Lambert (WLA - news), can be used to fight colon cancer. This is a second blow for the drug, which is highly effective against diabetes but which is linked with liver damage.
An estimated 500,000 people died of colon cancer around the world last year. It is one of the most deadly forms of cancer and is linked with a high fat diet. Diets high in fruits and vegetables are known to reduce the risk of colon cancer.
Three teams set out to find out just how fats can set off the tumor-making process. They homed in on PPAR receptors, one of many kinds of chemical doorways on cells.
They help control the response to fat, and one specifically known as PPAR-gamma is activated by the diabetes drug troglitazone, by painkillers such as ibuprofen, and by a new class of painkillers known as COX-2 inhibitors.
One study found that activated PPARg stopped cancer cells from their out-of-control mode of replication, turning them instead back into normally dividing cells. But two others found just the opposite.
Dr. Bruce Spiegelman and colleagues at Harvard Medical School infected specially bred mice with human colon cancer and then treated them with troglitazone. Writing in the journal Nature Medicine, they said they found a ''significant reduction of growth'' in the tumors.
But Dr. Ronald Evans of the Salk Institute for Biological Studies in La Jolla, California and Dr. John Auwerx and colleagues at the French research institute INSERM in Lille found the opposite.
Auwerx's team tested mice with a drug related to troglitazone and with a COX-2 inhibitor - one of a new experimental family of drugs that has the good effects of aspirin, reducing inflammation, without the side-effects of bleeding and stomach upset.
They found that in mice on high-fat diets, tumors increased in number when they were given the drugs.
They said it could be PPARg was somehow involved in how the body reacts to the Western diet, which is high in unhealthy animal fats.
''Why the discrepancy?'' Nature Medicine asked in an editorial. It could be some of the specially bred mice used do not reflect human colon cancer. The journal says the research raises as many questions as it answers.
''A number of pharmaceutical companies are following the fortunes of the new diabetes drug troglitazone,'' it read.
At least 26 people have died from liver failure while using Rezulin. ''The bad news about troglitazone is far from over,'' the journal added.
Brian Seed of Massachusetts General Hospital said in a commentary he said it would ''not be prudent'' to prescribe troglitazone, ibuprofen and other drugs acting on PPARg for the prevention of colon cancer. |
