MIAMI, March 9, 2010 (AFP) - Researchers said Tuesday that papaya leaf extract and its tea have dramatic cancer-fighting properties against a broad range of tumors, backing a belief held in a number of folk traditions.

University of Florida researcher Nam Dang and colleagues in Japan, in a report published in the Journal of Ethnopharmacology, documented papaya's anticancer effect against tumors of the cervix, breast, liver, lung and pancreas.

The researchers used an extract made from dried papaya leaves, and the effects were stronger when cells received larger doses of papaya leaf tea.

Dang and the other scientists showed that papaya leaf extract boosts the production of key signaling molecules called Th1-type cytokines, which help regulate the immune system.

This could lead to therapeutic treatments that use the immune system to fight cancers, they said in the February issue of the journal and released Tuesday by the university.

Papaya has been used as a folk remedy for a variety of ailments in many parts of the world, especially Asia.

Deng said the results are consistent with reports from indigenous populations in Australia and his native Vietnam.

The researchers said papaya extract did not have any toxic effects on normal cells, avoiding a common side effect of many cancer treatments.

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 tumors in all the cultures.

Dang and a colleague have applied to patent the process to distill the papaya extract through the University of Tokyo.