Unerring hormone delivers cancer drug
Mice remain fertile with unusual chemotherapy technique.
Researchers may have found a better way to target anti-cancer drugs at tumours: they attach the medicine to hormones. The technique turns a traditional way of tackling cancer on its head, as researchers often try to inhibit tumour growth by blocking these hormones.
One of the main difficulties in cancer treatment is delivering drugs to tumours, and only tumours. Many current chemotherapy treatments use medicines that also kill normal cells, with side-effects that range from hair loss to infertility.
So Tamara Minko of Rutgers in Piscataway, New Jersey, and her colleagues decided to take advantage of the fact that many tumour cells produce abundant receptors for a hormone known as luteinizing hormone-releasing factor.
Cancer cells, particularly those from the breast, ovary and prostate, are known to contain more receptors for this hormone than normal cells. No one knows why, although it is assumed that it helps to promote a cancer cell's uncontrolled growth.
In the past, researchers have attempted to block the action of the factor, but Minko's team decided to take advantage of it.
The team attached a portion of luteinizing hormone-releasing factor to a drug called camptothecin, which kills cells by disrupting the repair and replication of DNA.
Twenty times more cells died in mice tumours treated with the drug when it was joined to the hormone, the team reports in the Proceedings of the National Academy of Sciences1. More important, most of the camptothecin reached cancerous cells and it hardly affected healthy organs such as the heart, lung and liver.
And female mice dosed with the drug had just as many babies as those who did not get the medicine.
The result is more targeted than many drug delivery approaches that have been tried in the past, says the team, though they still need to test exactly how accurate the technique is.
- Dharap S. S., et al. Proc. Natl Acad. Sci. USA, published online, doi:10.1073/pnas.0504274102 (2005).