Nanobees take the sting out of cancer

Researchers at Washington University School of Medicine in St Louis have harnessed the toxin in bee venom to kill tumour cells by attaching the major component of the venom to nano-sized spheres that they call nanobees. In mice, nanobees delivered the bee toxin, melittin, to tumours, while protecting other tissues from the toxin's destructive effects. The tumours were shown to stop growing or shrank.

Melittin is a small protein, or peptide, which is strongly attracted to cell membranes, where it can form pores that break up cells and kill them. Professor Samuel Wickline, a specialist in nanomedicine at Washington University who led the research, explained: "the nanobees fly in, land on the surface of cells and deposit their cargo of melittin, which rapidly merges with the target cells." The investigators have shown that the bee toxin is taken into the cells where it pokes holes in their internal structures.

As detailed in the 10th August online edition of the Journal of Clinical Investigation (10.1172/JCI38842), the scientists tested nanobees in two kinds of mice with cancerous tumours. One mouse breed was implanted with human breast cancer (BC) cells and the other with melanoma tumours. After four to five injections of the melittin-carrying nanoparticles over several days, growth of the BC tumours slowed by nearly 25 per cent, and the size of the melanoma tumours decreased by 88 per cent compared to untreated tumours.

The researchers indicated that the nanobees gathered in these solid tumours because they often have leaky blood vessels and tend to retain material. Scientists call this the "enhanced permeability and retention effect of tumours", and it explains how certain drugs concentrate in tumour tissue much more than they do in normal tissues. Further, the researchers developed a more specific method for ensuring that nanobees target tumours and not healthy tissue, by loading them with additional components. When they added a targeting agent that was attracted to growing blood vessels around tumours, the nanobees were guided to precancerous skin lesions that were rapidly increasing their blood supply. Injections of targeted nanobees reduced the extent of proliferation of precancerous skin cells in the mice by 80 per cent.

The flexibility of nanobees and other nanoparticles made by the group suggests that they could be readily adapted to fit medical situations as needed. The ability to attach imaging agents to nanoparticles means that they can give a visible indication of how much medication reaches tumours and how they respond. Potentially, it is thought that these could be formulated for a particular patient. Overall, the results suggest that nanobees could not only lessen the growth and size of established cancerous tumours, but also act at early stages to prevent cancer from developing.

Alice Rossiter - Cancer Drug News Editor