Doctors may be one step closer to uncovering the mystery that surrounds the causes of cancer. A specific class of genes has been proven to trigger some types of the disease.

We all know about the major risk factors for cancer -- smoking, fatty foods, exposure to the sun and heredity.

Now, scientists are closer to discovering what triggers cancer on a cellular level. Carlo Croce is a genetics researcher at Ohio State University. He says, "Now we are able, we and many others, are able to develop novel treatments that might be much more successful."

Croce and his colleges have identified a class of genes called microRNA. They control other genes in our bodies. Altered microRNA genes had already been found in many types of cancer. So Croce's team purposely altered a single type of microRNA gene in lab mice. The result -- the mice developed leukemia and lymphomas.

"The direct proof is to show that when we reintroduce that overactive, very active microRNA into normal cells, those normal cells become malignant."

Croce says the next step is to find treatments that counter the effects of the altered microRNA. So far, he and his team have come up with a way to shut off the activity of the very active microRNA, thus preventing it from creating cancer cells.

"The new challenge,” says the doctor, “and we and many others around the world will try to do that, [is] to develop the treatments based on alterations in microRNA."

The good news is Croce says the technology to manipulate the activity of microRNA already exists. Besides human leukemias and lymphomas, microRNA genes also have been found in human lung, breast and colon cancers.