[Photodynamic therapy of human tumor xenotransplants in athymic nu/nu mice]

The effect of phototherapy on the growth of two human tumors, i.e. carcinoma of the rectum I and III, was studied. The tumors were xenotransplated into athymic nu/nu mice. Meso-tetra-(para-sulfophenyl)-porphin, TPPS4, was used as photosensitizer. Incorporation studies showed the optimal dose for phototherapy to be 10 mg/kg TPPS4 and the time interval 72 hours. Under these experimental conditions (helium-neon laser, 632, 8, 300 J/cm2) one of six tumors was cured in the group with carcinoma of the rectum I, and that both after IV and IT administration of the photosensitizer. The other five experimental animals exhibited only partial responses to phototherapy. In the group with carcinoma of the rectum III, five out of six tumors were cured by IT administration of TPPS4 under the same experimental conditions. In one mouse there was only partial response to phototherapy. After IV administration of TPPS4, however, not a single tumor was cured and the response to phototherapy was only partial in all the six experimental animals.