Enzyme levels may be responsible.

Scientists are targeting a family of enzymes for new drug development in the fight against rheumatoid arthritis, osteoarthritis, and other serious diseases. Connective tissue remodeling is the normal ongoing process whereby tissue is broken down by matrix metalloproteinase (MMP) enzymes and then rebuilt. Abnormally high levels of MMPs, though, accelerate the destruction of connective tissue, which is associated with arthritis and cancer, indicates Henning Birkedal-Hansen, scientific director, National Institute of Dental Research, National institutes of Health.

Research under way to develop enzyme inhibitors to control the production of MMPs could be successful in the next five to 10 years, he predicts. That could have significant medical importance because "research shows excess MMPs also facilitate tumor growth and promote lung, colon, and breast cancer metastasis.

"Injury and inflammation trigger the production of MMPs; the enzymes then remodel the tissue. However...