Effect of soybean isoflavones on MMTV-erbB-2 transgenic mice at different estrogen environments

Objective To investigate the effect of the soybean isoflavones at different estrogen environments on the pathogenesis of breast cancer in MMTV-erbB-2 transgenic mice. Methods 150 fiveweek-old MMTV-erbB-2 transgenic female mice were phosen and divided into five groups; control group,low estrogen group 1, low estrogen group 2, high estrogen group 1 and high estrogen group 2. The incidence and latent period of breast cancer were observed, and the expression of estrogen receptor (ER) ,progesterone receptor (PR), and proliferating cell nuclear antigen (PCNA) proteins was detected by using immunohistochemistry SP method. Results The incidence of breast cancer in control group, low estrogen group 1, low estrogen group 2, high estrogen group 1 and high estrogen group 2 was 73. 3% , 96. 7% ,30. 3% , 40. 0% and 83. 3% , respectively, with the difference being not significant between control group and high estrogen group 2, and between low estrogen group 1 and high estrogen group 2 (P ＞ 0. 05 ) , but with the difference being significant among the other groups (P ＜ 0. 05 ). There was significant difference in the average latent period of breast cancer among all groups (P ＞ 0. 05 ). There was significant difference in the number of TEB between low-estrogen group 1 and other groups (P ＜ 0.05). There was significant difference in the erbB-2 expression among the groups ( P ＞ 0. 05 ). There was no significant difference in the expression of breast ER and PR between control group and other groups ( P ＞ 0. 05 ). The PCNA expression in breast tumor tissue in low-estrogen group 1 was significantly higher than other groups (P ＜0. 05) , and there was significant difference in the PCNA expression between control group and high estrogen group 2, between low estrogen group 1 and high estrogen group 2 (P ＜ 0. 05). Conclusion The soybean isoflavones at different estrogen environments play different roles in the occurrence and development of MMTV-erbb-2 transgenic mouse mammary tumor. In the context of low estrogen, soybean isoflavones could even promote breast cancer formation and development. In the context of high estrogen, soybean isoflavones could inhibit breast cancer and development. Key words: Castration surgery; Soybean isoflavones; ER; PR; PCNA