Remissions of mammary adenocarcinoma in hypothyroid mice given 5-fluorouracil and chloroquine phosphate.

In two separate experiments, treatment of C3H/He mice bearing transplantable mammary adenocarcinomas (C3HBA) with a regimen of 6-propylthiouracil (PTUra) and 5-fluorouracil (FUra) plus chloroquine phosphate (CP) resulted in complete remissions of 77 and 65%, respectively. Treatment with PTUra alone resulted in 41% remissions in experiment 1 and 35% remissions in experiment 2. None of the nontreated control mice in either experiment had spontaneous remissions, and all controls died in each experiment. The principal effect was apparently due to the treatment with PTUra, inasmuch as most of the tumors disappeared during the 21-day treatment period. This observation indicated that the proper timing of the thyroid treatment with PTUra was crucial to achieve the best results. The combined FUra+CP regimen augmented the effects of the thyroid treatment and resulted in an increase in remissions.