title: Obesity increases the incidence of 7,12-dimethylbenz(a)anthracene-induced mammary tumors in an ovariectomized Zucker rat model.
abstract: Obesity is associated with increased risk for postmenopausal, but not premenopausal breast cancer. Recently, we reported that intact obese Zucker rats had increased susceptibility to DMBA-induced mammary tumors compared to lean Zucker rats. In the present study, we investigated whether excessive adipose tissue would promote mammary tumor induction in the absence of ovarian estrogen. Lean and obese rats were sham-operated or ovariectomized at 40 days old and were gavaged at 50 days old with 65 mg/kg DMBA. Rats were weighed and palpated twice weekly for detection of mammary tumors and sacrificed 135 days post-DMBA treatment. Obese sham-operated (O/S) rats had a shorter latency period (102 days) compared to lean sham-operated (L/S) (134 days) and obese ovariectomized (O/O) rats (123 days). At the end of the experiment, 36% of the O/O rats developed mammary tumors while lean ovariectomized (L/O) rats developed no mammary tumors (P<0.001), and 59% of the O/S rats developed mammary tumors compared to 30% of the L/S rats (P<0.05). In summary, obesity increases the susceptibility of ovariectomized Zucker rats to DMBA-induced mammary tumors, suggesting that adipose tissue-derived estrogen in obese animals may be sufficient to promote DMBA-induced tumors in this model. These results suggest that obesity in postmenopausal women may increase breast cancer risk due to increased breast tissue exposure to adipose tissue-derived estrogen. In conclusion, we have developed an animal model to further investigate the role of obesity in breast cancer development in postmenopausal women.
authors.affiliation: Department of Dietetics and Nutrition, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA. hakkakreza@uams.edu
authors.forename: Reza
authors.initials: R
authors.lastname: Hakkak
authors.forename: Stewart
authors.initials: S
authors.lastname: MacLeod
authors.forename: Saeid
authors.initials: S
authors.lastname: Shaaf
authors.forename: Andy W
authors.initials: AW
authors.lastname: Holley
authors.forename: Pippa
authors.initials: P
authors.lastname: Simpson
authors.forename: George
authors.initials: G
authors.lastname: Fuchs
authors.forename: Chan Hee
authors.initials: CH
authors.lastname: Jo
authors.forename: Thomas
authors.initials: T
authors.lastname: Kieber-Emmons
authors.forename: Soheila
authors.initials: S
authors.lastname: Korourian
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D001835:Body Weight; D002273:Carcinogens; D005260:Female; D008099:Liver / Q000473:pathology; D015674:Mammary Neoplasms, Animal / Q000139:chemically induced* / Q000150:complications; D008325:Mammary Neoplasms, Experimental / Q000150:complications; D009765:Obesity / Q000150:complications*; D009929:Organ Size; D010052:Ovariectomy; D051381:Rats; D011924:Rats, Zucker; D013997:Time Factors
chemical_list: D002273:Carcinogens; D015127:9,10-Dimethyl-1,2-benzanthracene