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Aromatase is an enzymatic complex responsible for the conversion of androgens into estrogens; these hormones are important in development, reproduction, but also in the growth of estrogen-dependent cancer. This enzyme is present in 60-70% of the breast cancer. The aromatase inhibitors are important drugs in the breast cancer treatment of postmenopausal women. In order to study their in vivo activity, animal models have been developed, e.g. rat with tumour induced by 7,12-dimethylbenz[a]anthracene, PMSG-primed immature rat or athymic nude mice with aromatase transfected MCF-7 xenograft. In this review, we were interested in preclinical results obtained with both classes: steroidal and nonsteroidal inhibitors. The former group, as substrate analogs formestane or exemestane, are irreversible, selective and long-lasting inhibitors of aromatase. The nonsteroidal molecules, such as letrozole or anastrozole, are reversible inhibitors with high affinity. Finally, knowledge of the enzyme active site, with molecular modeling and site-directed mutagenesis, could be useful to develop new inhibitor families, more specific and potent in vivo.

Animal models are useful in the evaluation of adjuvant or palliative treatment modalities of human colonic adenocarcinoma. In the present paper, the efficacy of 22 usual chemotherapeutic agents was evaluated in a model of peritoneal carcinomatosis of colonic origin in the BD IX rat. Mitomycin, cisplatine, carboplatine, cyclophosphamide, ifosfamide, and thiotepa were very effective agents on microscopic carcinomatosis (treatment given 3 days after an intraperitoneal inoculation of 1 x 10(6) DHD/K12/PROb cells). Intravenous administration was as effective as the intraperitoneal route, except for anthracyclines and 5-fluorouracil. Rats treated at early stages by thiotepa or cisplatin survived up to 4 months after cell injection and did not display tumor at autopsy. Administered late (15 days after cell injection), none of the drugs were able to cure the rats with carcinomatosis.