'Death carrot' could help treat cancer

A pretty yellow Mediterranean plant, sometimes called the “death carrot”, is being developed into a potential new drug for treating cancer by an international team of researchers. Even though Thapsia garganica plant looks innocent enough, it contains thapsigargin and is highly toxic to sheep and cattle. This lethal plant could find a new use by targeting and killing cancer cells. It kills cells, including cancer cells, by blocking a protein called SERCA, which helps cells control their internal calcium levels. The real challenge lies in harnessing the power of this toxic substance, driving it into killing just the cancer cells and leaving the healthy cells alone. Samuel Denmeade, an oncologist at Johns Hopkins University in Baltimore, has taken on the difficult task. Denmeade and his team spent 15 years engineering an analogue of thapsigargin, which is an active ingredient of the plant, to fight cancer cells exclusively. His team modified the thapsigargin molecule by adding an extra peptide chain which prevents the toxin from entering cells. That is, until it encounters PSMA – an enzyme commonly found on the surface of many prostate cancer cells. PSMA cleaves the extra chain off the toxin, setting it free to do its devastating business. While traditional chemotherapy drugs only target cells that rapidly divide, this new toxin destroys not just the cancer cells currently growing, but also those lying dormant as well as non-cancer cells recruited to help the tumour grow. “You can envision it as a grenade,” New Scientist quoted Denmeade as saying. “One guy pulls the pin, but it kills all the guys standing around,” he said, The study has been recently published in Science Translational Medicine.