Cancer would not be as dangerous if it stayed in one place. But tumor cells are highly mobile, breaking off and flowing away in new directions inside the bloodstream.

In a novel approach to stopping the spread of cancer, Orlando researchers are using tobacco -- a leading cause of the disease -- to grow a protein that might keep tumor cells from invading other organs. The plants can be genetically altered to make the desired protein, and although the work is in its early stages, researchers think they could be tapping into a valuable tool for preventing cancer from launching a wide-scale assault. "Cancer is usually pretty curable as long as it hasn't spread around the body," said John Francis, director of clinical and research laboratories at Florida Hospital's Walt Disney Memorial Cancer Institute. "If this is successful, I think it could have huge potential for the treatment of cancer." Researchers from the Disney institute and the University of Central Florida are working jointly on the project. Their focus is tissue factor protein, or TFP, which helps in the formation of clots. The protein normally remains on the outside of blood vessels, ready to slow the loss of blood if the vessel is broken. Tumors make use of clots But researchers have discovered that tumor cells also use tissue factor protein to help cement themselves to new locations within the body. Cancer spreads when cells from the original tumor move around through the bloodstream, which can gush up to 13 mph inside its thoroughfare of veins and arteries. Once loose in this fast-moving stream of blood, cancer cells must put on the brakes and cling to the wall of the vessel. They do this, in part, by forming a clot that helps them slow down and latch onto the vessel. The cancer cells then can squeeze through the wall to a new location. There are many substances involved in forming a clot, but tissue factor protein is critical, Francis said. The theory is that stopping the protein will impede the ability of the cancerous cells to spread. Nature itself provides the potential remedy. In addition to making tissue factor protein, the human body also makes a protein to counter it -- a substance called tissue factor protein inhibitor. The naturally occurring substance exists in the body at low levels all the time. Francis said that in animal studies, researchers have been able to reduce the spread of cancer by increasing the amount of the anti-clotting protein in the test animals. To do the same in people, researchers need to create large quantities of the desired substance. Enter the tobacco plants. Tobacco, which grows quickly and produces large leaves, is ideal for what has been coined "biopharming," or using plants to grow drugs. Henry Daniell, a UCF professor of molecular biology and microbiology, inserted the gene for the anti-clotting protein into tobacco-plant cells. The cells are then grown into full-fledged plants that incorporate the new gene into their makeup. The genetically altered plants hold the desired protein in their leaves. "It's an irony that a lifesaving drug could come from tobacco," Daniell said. The work has not gotten this far yet, but eventually, Daniell will grind up the plant leaves and extract the anti-clotting protein. It will then require extensive testing to make sure the protein has the same effect as the human-made variety. It could be several years before the research is completed and testing is under way in people. A drug based on this protein would target the tumor cell's ability to clot, so it should not affect the body's normal clotting functions. "What this does is block a support system that the tumor has for spreading," said Dr. Leo Zacharski, professor of medicine at Dartmouth Medical College in New Hampshire, who did pioneering research with cancer patients and anti-clotting drugs in the 1970s. "You have to outsmart the tumor by using powerful inhibitors, and that's exactly what [the Orlando researchers] are doing. I think it's a great idea, but there's still a lot of work that has to be done." If the tobacco plants create a suitable form of the protein, the next hurdle would be to package the protein in a form that could be taken orally. Such a drug may be given to a patient for a long time, providing ongoing protection from secondary cancers. "You could probably take this drug for many months if not years," Francis said. He also thinks the protein's anti-clotting effects could be used on other illnesses, such as heart disease. Francis estimated that Florida Hospital has spent about $30,000 for the initial research, but he and Daniell plan to search for additional sources of research dollars. He hopes other scientists will agree that the protein holds promise. "[The protein] is an extremely powerful therapy with implications for a number of diseases," he said.

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