Laetrile/Amygdalin (PDQ®): Complementary and alternative medicine - Health Professional Information [NCI] - Laboratory / Animal / Preclinical Studies
In the first of these studies, amygdalin enhanced the antitumor activity of a combination of enzymes and vitamin A in mice with spontaneous mammary adenocarcinomas. The amygdalin was given by intramuscular injection, the vitamin A was administered orally through a feeding tube, and the enzymes were injected into and around tumor masses. No anticancer activity was observed when amygdalin was given alone.
In the second study, white blood cells and prostate cancer specimens were used to investigate the potential of amygdalin to stimulate the immune system. The researchers found that amygdalin caused a statistically significant increase in the ability of a patient's white blood cells to adhere to his own prostate cancer cells, suggesting some immune system-boosting potential for amygdalin.
The third study investigated the ability of amygdalin and beta-glucosidase to indirectly sensitize the hypoxic (oxygen-starved) cells at the center of a tumor to the lethal effects of gamma irradiation. Cells at the periphery (outer edge) of a tumor are more sensitive to gamma irradiation because they are not oxygen-deprived. Radiation kills cells, in part, by splitting molecules, including oxygen molecules, to form free radicals, which are highly reactive chemicals that can damage DNA and other important cellular components. It has been proposed that, by inhibiting oxygen uptake by peripheral tumor cells, more oxygen will diffuse to the hypoxic cells, thereby increasing their sensitivity to radiation. In this study, beta-glucosidase was used to break down amygdalin to release cyanide, with the cyanide inhibiting oxygen uptake by peripheral tumor cells. Presumably, cyanide uptake by interior tumor cells is less than that of cells located at a tumor's periphery. Spheres of tumor cells created in the laboratory and tumor slices were used in the study. The investigators found that amygdalin and beta-glucosidase could act as indirect radiation sensitizers of hypoxic tumor cells. It should be noted, however, that independent confirmation of this positive finding has not been published in a peer-reviewed scientific journal. A major hurdle in the application of this technique to animals and humans is the development of a method for delivering a sufficient amount of cyanide to tumors without causing substantial systemic or regional toxicity.