Study on the protection against estrogen-dependent cancer

点击翻译按钮获取中文摘要

The estrogen dynamics in breast cancer tissues, correllation of clinicopathological and prognostic factors with expression levels of 9 kinds of estrogen-related enzymes participating in the estrogen synthesis and estrogen-signal transducing system, was examined. High level expression of ErbB2, aromatase, and steroid sulfatase was a good prognostic factor, whereas that of ER-alfa and cyclin D2 was a poor prognostic factor. Next, in vivo carcinogenesis by estrogens was examined. DMBA of a chemical carcinogen caused rare tumorigenesis in aromataes-knockout mice (estrogen deficeint mice), in contrast with high frequency in wild mice. Furthermore, it was often observed in cyplBl-transgenic mice to estrogen-dependently suffered from tumors, suggesting that estrogens were metabolized to active carcinogens by cyp1B1. To analyze relationship between cancer cells-stromal cells interaction in the cancer tissues and clinicopathological factors, MCF7 cells carrying ERE-GFP was prepared and used for tracing ER activation in the cancer cells through the interaction by a means of a fluorescent GFP probe. The results indicated that GFP expression vary among stromal cells from breast cancer tissues and were more frequently induced in the postmenopausal tissues than in premenopausal ones. Sensitivities to aromatase inhibitors was also varied among the individual cases. Finally, correlation of estrogens dynamics in the cancer cells with proliferative capability and sensitivities of cancer cells to aromatase inhibitors was analyzed using stable transformant MCF7 cells with various profiles of estrogen metabolism. Consequently, it was indicated that indirect synthesis of estrogens from estrogen sufates by steroid sulfatase also plays an important role in the supply of estrogens to cancer cells as well as direct synthesis from androogens by aromatase, and suggested a possibility of steroid sulfatase inhibitors and estrogen sulfotransferase inducers as anti-cancer drugs.