Despite tremendous advances in medicine, breast cancer remains a leading cause of death in the UnitedStates as well as the rest of the world. It has been estimated that there will be 182,460 new cases and40,480 deaths in the US in 2008 due to breast cancer in women. In view of the limited treatment options forpatients with advanced stages of breast cancer, preventive control approaches, in particularchemoprevention could play an important role in therapeutic strategies to combat this disease. The plant-derived triterpenoids are used for medicinal purposes in many Asian countries, and some of thesecompounds are reported to have promising cancer-suppressive activity against various human breastcancer cells in vitro. Amooranin (AMR) is a triterpene acid isolated from the stem bark of Amoora rohituka, awell known medicinal plant native of India. AMR has been shown to inhibit the proliferation of human breastcarcinoma cells in vitro as well as suppress rat mammary tumors in vivo. Recently, it has been shown thatnovel synthetic analogue of amooranin (AMR-Me) has enhanced potency in the killing of human breastcarcinoma cells in vitro because of its effects on genes associated with cell proliferation and apoptosis. Thisrevised proposal is based on the hypothesis that AMR-Me would be clinically useful as a chemopreventiveagent in human breast cancer. Accordingly, the objectives of this proposed research are to evaluate thechemopreventive effects of AMR-Me and to delineate its possible mechanism(s) of action in a well-established, chemically-induced animal model of breast cancer, which closely mimics the human disease.Female Sprague-Dawley rats will be fed either a basal diet or diet supplemented with various levels ofAMR-Me resulting in increasing doses of this terpenoid. The chemopreventive doses will be based on anexperimentally-determined maximum tolerated dose (MTD). The AMR-Me treatment will start one weekprior to a single oral (60 mg/kg) administration of 7,12-dimethylbenz(a)anthracene (DMBA), an establishedcarcinogen for the initiation of mammary tumors. Animals will be palpated starting 4 weeks following DMBAadministration to record the presence, location, and size of tumors. All animals will be sacrificed 18 weeksfollowing the initiation of the mammary carcinogenesis with DMBA to conduct biological, biochemical, andmolecular endpoint studies. The chemopreventive effect of AMR-Me will be assessed from the incidence,multiplicity, volume, and size distribution of mammary tumors. The influence of AMR-Me in modulatingproliferation index, apoptotic index, and estrogen receptor expressions will be investigated. The possiblemechanistic role of AMR-Me at the genetic and molecular pathways that lead to the induction of apoptosisand inhibition of cell proliferation will be thoroughly examined.
The results of the proposed study may extend our knowledge on in vitro breast cancer suppressive effect of a novel triterpenoid in a clinically relevant in vivo animal model. Possible pharmacological modulation of several cellular and molecular regulatory pathways through the effective use of this triterpenoid may lead to the development of an effective chemopreventive agent for breast cancer. This may pave the way for human trials of this promising triterpenoid in attenuating the risk of developing what remains a devastating disease.
