On the irreproducibility of thioproline.

Thioproline was the first inducer of reverse transformation of neoplastic cells to be tested, with encouraging activity, in cancer patients. These results could not be reproduced in two subsequent clinical trials. The possible reason for this irreproducibility could be that, in the first active trials, the patients may have taken other non-cancer-related drugs that, by acting on the cyclic AMP and prostaglandin cascades, could have functioned as positive cooperators on the effect of thioproline. A new clinical trial, with thioproline associated to its cooperators, is proposed in tumors which have no hope of improvement with cytostatics.