Thursday, October 1, 2009

Nanobees Sting Tumors to Death

We have known for many years that melittin, an ingredient in bee venom, is a poison to tumor cells. Development of therapeutic uses of the substance has been stymied by the fact that melittin does damage to healthy cells as well. Now researchers from Washington University in St. Louis have developed nanoparticles called 'nanobees' that can ferry the melittin directly to tumor cells with great specificity.
The Wall Street Journal reports:
Among Dr. Soman's first experiments was to see how melittin interacted with the nanoparticles. He found that not only did it attach quickly to the outer, lipid layer of the nanoparticles, but that the attachment was stable, suggesting that the nanoparticle-melittin combination, or nanobee, might be able to circulate in the body and not attack healthy cells.
The next issue was to figure out how to get the melittin, once it came upon a tumor, to detach from the nanoparticle and transfer to the cancer cells, taking its cell-killing properties with it. The researchers accomplished this by attaching a third component to the mix—a ligand, which is a chemical that binds two distinct compounds. The ligand they used in this case—which Dr. Schlesinger likens to a "molecular ZIP Code"—has an affinity for attaching to a receptor plentiful in newly formed blood vessels. That's useful in cancer treatment because tumors tend to form new blood vessels to feed themselves and grow.
The scientists began testing the resulting mix, which resembles a milky substance, in mice in 2007. They tried it on a few dozen lab mice with three kinds of tumors: a mouse form of skin cancer; a form of human breast cancer transplanted into the mice; and precancerous lesions caused by human papillomavirus, which can cause cervical cancer in humans.
After about two weeks of treatment, the nanobees slowed the growth of the breast-cancer tumors, shrank the melanoma tumors and reduced the precancerous lesions, compared with control groups that received saline injections and nanoparticles lacking melittin.
Full paper in J. Clin. Invest.: Molecularly targeted nanocarriers deliver the cytolytic peptide melittin specifically to tumor cells in mice, reducing tumor growth
Link to WSJ: The Buzz: Targeting Cancer With Bee Venom ...

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