A plant extract has been found to inhibit tumor growth in laboratory tests. It could be used to target some of the cancers that are currently most difficult to treat, suggests the research.
Two studies published in the early online edition of Nature show that cyclopamine, a chemical extracted from the corn lily, shrinks tumors both in tests on mice and on human cells in vitro.
The findings back previous research demonstrating cyclopamine's action against cancer. A study by Dr Philip Beachy and colleagues at the John Hopkins School of Medicine last year found that cyclopamine effectively killed cultured mouse medulloblastoma cells and tumors implanted in animals, as well as medulloblastoma cells extracted from human tumors. Medulloblastoma is an aggressive brain cancer, which affects children, but so far cannot be treated.
The researchers believe that cyclopamine blocks the Hedgehog signalling pathway, known to be critical for the growth and differentiation of cells during embryonic development but also implicated in malignancy of tumour cells if activated later in life.
In the new research Dr Beachy reports that high levels of the Hedgehog protein appear to trigger tumors in a wide range of digestive tract tumors, "including most of those originating in the oesophagus, stomach, biliary tract and pancreas, but not in the colon". In tests on mice, cyclopamine blocked this protein and significantly reduced the size of tumors after 12 days of treatment.
In a different study published in the journal, Dr Sarah Thayer and colleagues at Massachusetts General Hospital and Harvard Medical School found that hedgehog signalling may also be an important mediator in pancreatic cancer. Again, cyclopamine induced apoptosis of tumor cells in both in vitro and in vivo tests.
The findings suggest that cyclopamine could be used to treat these types of cancer, although researchers will need to carry out further tests to confirm the role of the hedgehog pathway in human cancer.
There could also be barriers in the form of standardising sufficient quantities of cyclopamine, extracted from Veratrum californicum, a plant native to the US and poisonous in its natural form.