When a compound is first isolated after being collected from nature, it is tested in a variety of ways to help scientists better understand how it works. One of these tests involves the compound’s ability to kill cells that are known to be cancerous. There are a wide variety of different cancer cells and a compound could fight one very specific type of cancer or it could be effective at killing many different cancer types.
During early testing, cancerous cells are treated with the new compound and then a dye is used to determine if the cells live or die. It is important to remember that just because a compound is able to kill cancer cells in these preliminary tests, it doesn’t mean it is safe. Many compounds are toxic not only to cancer cells but also to normal cells and so while they may be very effective at killing cancer cells, they would never be safe to use as a medicine. If a compound shows that it can specifically kill cancer cells without harming normal cells then testing can begin on laboratory animals to make sure there aren’t any negative side effects of treatment such as weight loss or illness.
Until a compound has been shown to selectively kill cancer cells in a living animal it is called a cytotoxic compound (“cell toxic”), but after it has been shown to fight against a tumor in a living animal, it is then referred to as anti-cancer.
-- Kevin Tidgewell, postdoctoral researcher, Center for Marine Biotechnology and Biomedicine