 The humble papaya is gaining recognition in Western medicine for its anticancer powers, with a University of Florida researcher claiming that the power fruit thwarted growth of cancer cells in lab tests.
University of Florida researcher Nam Dang, MD, PhD, and colleagues in Japan have documented papaya's dramatic anticancer effect against a broad range of lab-grown tumours, including cancers of the cervix, breast, liver, lung and pancreas. The researchers used an extract made from dried papaya leaves, and the anticancer effects were stronger when cells received larger doses of the tea. In a paper published in the Feb 17 issue of the Journal of Ethnopharmacology , Dang and his colleagues also documented for the first time that papaya leaf extract boosts the production of key signalling molecules called Th1-type cytokines. This regulation of the immune system, in addition to papaya's direct anti-tumour effect on various cancers, suggests possible therapeutic strategies that use the immune system to fight cancers.
The papaya extract did not have any toxic effects on normal cells, avoiding a common and devastating consequence of many cancer therapy regimens. The success of the papaya extract in acting on cancer without toxicity is consistent with reports from indigenous populations in Australia and his native Vietnam, said Dang, a professor of medicine and medical director of the UF Shands Cancer Centre Clinical Trials Office.
"Based on what I have seen and heard in a clinical setting, nobody who takes this extract experiences demonstrable toxicity; it seems like you could take it for a long time - as long as it is effective," he said. Researchers exposed 10 different types of cancer cell cultures to four strengths of papaya leaf extract and measured the effect after 24 hours. Papaya slowed the growth of tumours in all the cultures.
To identify the mechanism by which papaya checked the growth of the cultures, the team focused on a cell line for T lymphoma. Their results suggested that at least one of the mechanisms employed by the papaya extract is inducing cell death. In a similar analysis, the team also looked at the effect of papaya extract on the production of anti-tumour molecules known as cytokines.
Papaya was shown to promote the production of Th1-type cytokines, important in the regulation of the immune system. For that reason, the study findings raise the possibility of future use of papaya extract components in immune-related conditions such as inflammation, autoimmune disease and some cancers.
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