Experimenting on mice, the researchers found that nanobees delivered the bee toxin melittin to tumors, while protecting other tissues from the toxin's destructive power.
Revealing their findings in the online edition of the Journal of Clinical Investigation, the researchers said that tumors in the treated mice either stopped growing or shrank.
"The nanobees fly in, land on the surface of cells and deposit their cargo of melittin which rapidly merges with the target cells. We've shown that the bee toxin gets taken into the cells where it pokes holes in their internal structures," says co-author Dr. Samuel Wickline, who heads the Siteman Center of Cancer Nanotechnology Excellence at Washington University.
Melittin is a small protein, or peptide, that is strongly attracted to cell membranes, where it can form pores that break up cells and kill them.
"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. Cancer cells can adapt and develop resistance to many anticancer agents that alter gene function or target a cell's DNA, but it's hard for cells to find a way around the mechanism that melittin uses to kill," says co-author Dr. Paul Schlesinger, associate professor of cell biology and physiology.
In their study reports, the researchers have revealed that they tested nanobees in two kinds of mice with cancerous tumors: one mouse breed was implanted with human breast cancer cells, and the other with melanoma tumors.
They said that after four to five injections of the melittin-carrying nanoparticles over several days, growth of the mice's breast cancer tumors slowed by nearly 25 percent, and the size of the mice's melanoma tumors decreased by 88 percent compared to untreated tumors.
The researchers have also developed a more specific method to ensure that nanobees go to tumors and not healthy tissue, by loading the nanobees with additional components.
When they added a targeting agent that was attracted to growing blood vessels around tumors, the nanobees were guided to pre-cancerous skin lesions that were rapidly increasing their blood supply. Injections of targeted nanobees reduced the extent of proliferation of pre-cancerous skin cells in the mice by 80 per cent.
Based on their findings, the researchers came to the conclusion that nanobees could not only lessen the growth and size of established cancerous tumors, but they could also act at early stages to prevent cancer from developing.
"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," Schlesinger says.