Saturday, August 04, 2001

Tobacco might fight cancer

Plants can help stem-cell growth

By Kimberly Hefling
The Associated Press

        OWENSBORO, Ky. — Could the much maligned tobacco plant be used to help cancer patients?

        A California biotech company says it can, and it has set up shop in tobacco country to prove it.

        Large Scale Biology of Vacaville, Calif., has built a commercial “biopharmaceutical production facility” in this Ohio River community of 54,000. It is one of a handful of companies harnessing plants to produce useful human proteins.

        Genetic engineers use many different ploys to manufacture human proteins, such as insulin and growth hormones. Often, they isolate a human gene that carries the code for making a protein and splice it into yeast or bacteria, which multiply in fermentation vats. Other methods include putting genes into cancer cells, which grow endlessly in lab cultures, or into farm animals, which make the proteins in their milk.

        Now, companies are doing the same thing by the acre. They hope molecular farming, as some call it, will be cheaper and more efficient.

        “We borrow the plant's cellular machinery,” said Barry Bratcher, Large Scale Biology's biomanufacturing director. “The plant is just a host for us.”

        Tobacco produces lots of greenery, and scientists already have practice genetically manipulating it in the lab.

        Large Scale Biology has contracts with four local farmers to grow a combined 27 acres of tobacco for research. Tobacco is also grown in the company's five greenhouses in Owensboro.

        “It is ironic that tobacco might actually be used to create health instead of reducing health,” said chief executive officer Bob Erwin.

        The company has begun early stage testing of a tobacco-produced vaccine intended to trigger the body's immune system to fight non-Hodgkin's lymphoma. Each dose would be a customized protein, made by mutant genes taken from the patient's cancer cells. In theory, the proteins should stimulate the body to turn against the cancer.

        If the vaccine works, the company says it will produce a plant that can make 15,000 individualized doses a year.

        The company is considering human testing of a treatment for Fabry's disease. The therapy is a tobacco-made copy of a normal human enzyme, needed to break down fats, that is missing in victims of the disease.

        In earlier stages is a collaboration with the U.S. Navy and the National Institutes of Health to use tobacco to make stem cells grow. The goal is to find a natural human protein that will multiply blood-forming stem cells that have been isolated from the bone marrow.

        Stem cells are the source of all human tissue. Those taken from early stage embryos can grow into any cell in the body, and they will divide forever in test tubes. However, because they are derived from embryos discarded during in vitro fertilization, many people believe their use is unethical.

        Adults also have stem cells. Even though they can be isolated from the brain and other organs, they are difficult to grow on demand.

        A team of Navy and NIH researchers, led by Dr. John Chute, is attempting to produce a protein that will make blood stem cells divide repeatedly in a test tube. They already have evidence that the body makes such a protein. The collaboration with Large Scale Biology is intended to find the gene responsible so it can be manufactured in quantity.

        Dr. Chute said the protein could be useful for conducting gene therapy to correct inherited blood diseases, such as sickle cell anemia.

        The idea: Isolate a few of the exceedingly rare stem cells from the victim's marrow, then use the protein to produce copies of them. This will leave doctors with enough stem cells to attempt gene therapy, replacing the disease-causing genes with healthy copies. The repaired stem cells would be returned to repopulate the marrow.

        Mr. Erwin said his company hopes to manufacture the stem cell factor soon using tobacco plants in Owensboro. “We would like to get the gene identified in the next year and start clinical trials with the product in two years,” he said.

        Earlier this year, several members of Congress wrote a letter to President Bush praising Large Scale Biology's research because it does not use embryonic stem cells.


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- Tobacco might fight cancer