The effect of childbirth on carcinogenesis of DMBA-induced breast cancer in female SD rats

• Published in: Ai zheng Vol. 30; no. 11; pp. 779 - 785
• Main Authors: Zhao, Ji-An, Chen, Jin-Jun, Ju, Ying-Chao, Wu, Jian-Hua, Geng, Cui-Zhi, Yang, Hui-Chai
• Format: Journal Article
• Language: English
• Published: England Department of Hepatobiliary Surgery, The First Affiliated Hospital, Hebei Medical University, Shijiazhuang, Hebei 050013,P. R. China%Experimental Animal Center%Department of Breast Clinics Center%Department of Pathology, The Fourth Affiliated Hospital, Hebei Medical University, Shijiazhuang, Hebei 050011, P. R. China 01.11.2011; Sun Yat-sen University Cancer Center
• Subjects: 9,10-Dimethyl-1,2-benzanthracene; AgNOR; Animals; Antigens, Nuclear - metabolism; Carcinogens; Cell Transformation, Neoplastic; Female; Ki-67 Antigen - metabolism; Mammary Neoplasms, Experimental - chemically induced; Mammary Neoplasms, Experimental - metabolism; Mammary Neoplasms, Experimental - pathology; Mammary Neoplasms, Experimental - physiopathology; Minichromosome Maintenance Complex Component 2; Nuclear Proteins - metabolism; Original; Parity; Pregnancy; Proliferating Cell Nuclear Antigen - metabolism; Random Allocation; Rats; Rats, Sprague-Dawley; Receptor, ErbB-2 - metabolism; SD大鼠; Tumor Burden; 乳腺癌; 免疫组化检测; 分娩; 增殖细胞核抗原; 诱发; 雌性; childbirth; breast cancer; nulliparity; rat; 7,12-Dimethylbenanthracene (DMBA)
• ISSN: 1000-467X; 1944-446X
• DOI: 10.5732/cjc.011.10098

Many epidemiologic and clinical studies have indicated that the frequency of breast cancer was lower in parous women than in nulliparous women. Moreover, the incidence of breast cancer has been reported to be lower in women with early childbirth than in women with late childbirth. To verify the effect of childbirth and the age at first childbirth on carcinogenesis and progression of breast cancer, we induced breast cancer by 7,12-dimethylbenanthracene （DMBA） in 120 female Sprague-Dawley （SD） rats, and divided them into control or experimental （DMBA-treated） nulliparous, early childbirth, and late childbirth groups to observe the incidence, latency, and size of breast cancer. Argyrophilic nucleolar organizer regions （AgNOR） count and the expression of C-erbB-2, proliferating cell nuclear antigen （PCNA）, Ki-67, and minichromosome maintenance protein 2 （MCM2） in breast cancer tissues were detected by immunohistochemistry. The breast cancer incidences were 95.0%, 16.7%, and 58.8% in the experimental nulliparous, early childbirth, and late childbirth groups, respectively （all P 〈 0.05）. Between any two of these groups, the latency was significantly different, but tumor size was similar. AgNOR count and the expression of C-erbB-2, PCNA, Ki-67, and MCM2 were significantly higher in the experimental nulliparous group than in the experimental early or late childbirth groups （P 〈 0.05）, but no significant differences were observed between the latter two groups. Taken together, the results suggest that childbirth, especially early childbirth, can reduce the incidence and postpone the onset of DMBA-induced breast cancer.