New York, Sep 29 (IANS) A drug used in the treatment of Parkinson's disease has displayed significant anti-cancer effects in both human cell lines and mice, an advance that could lead the way to the drug being re-purposed as an anti-cancer medication, researchers say. The drug -- carbidopa -- may also explain the low incidence of many cancers (with the exception of melanoma) in patients with Parkinson's disease. Further, when used in both human pancreatic cancer cell line as well as in mouse models of pancreatic cancer, carbidopa showed that it could significantly inhibit cancer cell growth, researchers said. "Carbidopa as an anti-cancer agent to treat pancreatic cancer would be something truly amazing. Given the fact that it is an FDA-approved drug, re-purposing the same drug for cancer treatment would be tremendously cost- and time-saving," said lead author Yangzom Bhutia from Texas Tech University in the US. Parkinson's disease is a degenerative neurological disorder that mostly influences a person's movement and motor skills, with symptoms including shaking, rigidity and difficulty in walking. These effects are a result of lower than normal production of dopamine -- a chemical that sends behavioural signals from the brain to the body. L-DOPA or levodopa -- one of the chemicals that forms dopamine -- has been used to treat Parkinson's disease symptoms for many years, but when used alone can result in side effects such as nausea, as it crosses the blood-brain barrier. However, when taken in combination with the drug carbidopa, which does not cross into the brain, it prevents L-DOPA's conversion into dopamine outside the brain and reduces side effects for patients, the researchers said, in the paper published in the Biochemical Journal. "Carbidopa is never used by itself as a drug for any disease. But our data shows that carbidopa by itself possesses the anti-cancer effect. We believe that the reduced incidence of most cancers in Parkinson's disease patients is due to carbidopa," Bhutia added.