Bee Venom Nanoparticles Reduce Tumors in Animal Experiments

Melittin, the toxic component of bee venom, has been incorporated into nanoparticles such that when injected into mice triggered death of cancer cells and remission of tumors of both breast cancers and melanomas as well as destruction of precancerous skin lesions. Melittin, a peptide consisting of 26 amino acids, is the principal active component of bee venom (apitoxin) and is a potent antimicrobial compound and a powerful stimulator of phospholipase A2.

Investigators at Washington University School of Medicine (St. Louis, MO, USA) affectionately nicknamed the nanoparticles prepared from perfluorocarbon and melittin "nanobees.” These particles could be further modified to incorporate specific targeting molecules such as antibodies or receptors. The nanobee format has two major features. It sequesters the melittin and protects the body from its toxic effects. At the same time, the nanoparticles are resistant to the action of proteolytic enzymes in the blood that would otherwise quickly destroy the melittin.

To test the efficacy of the nanobees the investigators worked with mouse models for both human breast cancer and melanoma. Results published in the August 10, 2009, online edition of the Journal of Clinical Investigation revealed that four to five injections of generic nanobees over several days, slowed growth of breast cancer tumors by nearly 25%, while the size of melanoma tumors decreased by 88% compared to untreated tumors. Molecularly targeted nanobees selectively delivered melittin to multiple tumor targets, including endothelial and cancer cells. The transfer process did not disrupt the surface membrane of cells but did trigger apoptosis and in animals caused regression of precancerous dysplastic lesions.

"Melittin has been of interest to researchers because in high enough concentration it can destroy any cell it comes into contact with, making it an effective antibacterial and antifungal agent and potentially an anticancer agent," said senior author Dr. Paul Schlesinger, associate professor of cell biology and physiology at Washington University School of Medicine. "Cancer cells can adapt and develop resistance to many anticancer agents that alter gene function or target a cell's DNA, but it is hard for cells to find a way around the mechanism that melittin uses to kill."

"Nanobees are an effective way to package the useful, but potentially deadly, melittin, sequestering it so that it neither harms normal cells nor gets degraded before it reaches its target," said Dr. Schlesinger. "Potentially, these could be formulated for a particular patient. We are learning more and more about tumor biology, and that knowledge could soon allow us to create nanoparticles targeted for specific tumors using the nanobee approach."

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