The chemotactic and tumoricidal properties of the pathogenic/free-livi
ng amoeba Acanthamoeba castellanii were examined in vivo and in vitro.
A. castellanii trophozoites displayed strong positive chemotactic res
ponses to human melanoma (OCM-1) and murine melanoma (D5.1G4) cells. A
lthough the parasites typically invade and destroy the corneal epithel
ium and stroma, positive chemotactic responses were not detected again
st extracts of either of these corneal elements. In vitro studies reve
aled that viable parasites, as well as cell-free parasite lysates, pro
duced swift and extensive cytolysis of a wide variety of tumor cells.
The tumoricidal properties of A. castellanii were examined in vivo and
revealed that injection of viable parasites or cell-free parasite lys
ates into progressively growing subcutaneous melanomas resulted in 83%
and 53% reductions in the tumor masses compared with untreated contro
ls. The feasibility of utilizing the tumoricidal properties of pathoge
nic/free-living amoebae and their cell-free products in the treatment
of drug-resistant or radioresistant tumors warrants further investigat
ion.