Enzyme in Papaya Leaf, Papain, Inhibits Tumor Growth and Metastatis in Lab

Proteolytic Enzyme Therapy for cancerous tumors goes back to the success of Dr Beard in 1910 (Enzyme Therapy for Cancer). He retrieved the trypsin (a proteolytic enzyme) from young cows and injected it straight into the patient’s Tumor. This method showed success. Doctors who subsequently tried to mimic this procedure were discredited but they tried to retrieve trypsin from old cows, which by definition have less pancreatic enzymes due to their age. The theory of an “enzyme bank” that decreases as we age belongs to Dr Edward Howell, who proved this in a series of studies over years. (1945 +)

The enzyme in papaya leaves, papain, is a proteolytic enzyme that also seems to show a similar effect on tumors, as in this animal study below. Papain is a more potent proteolytic enzyme than our body’s trypsin.

Inhibition of tumor growth, invasion and metastasis in papain-immunized mice.

Bellelli A, Mattioni M, Rusconi V, Sezzi ML, Bellelli L.
Invasion Metastasis. 1990;10(3):142-69.

“The growth rate, invasion and metastasis of both the B16 melanoma and the Lewis lung carcinoma were inhibited in mice immunized with papain. These animals presented an increased mean survival time as compared to the tumor-bearing nonimmunized controls. Quantitative microscopy suggested that vasodilation and edema, associated with tumor invasion, are, at least partially, sustained by proteolytic enzymes, being strongly reduced when tumor cells were inoculated in papain-immunized mice.”


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