A study of estrogen signaling using DNA microarray in human breast cancer

Estrogen plays an important role in growth and progression of human breast cancer. To understand the mechanism of estrogen signaling is very important to clarify the breast cancer biology and fight breast cancer. One promising method of study is a DNA microarray, specifically a down-sized, specific, custommade cDNA microarray, which was used for 200 estrogen-responsive genes in the present study. We performed three different studies using our custom microarray. First, clustering analysis of the gene expression profile among the breast cancer specimens before and after aromatase inhibitor treatment could separate patients into two groups showing different estrogen responses. Second, analysis of tamoxifen-effects on the gene expression profile of a tamoxifen-resistant MCF-7 subline, clone 9, showed that most estrogen responsive genes in MCF-7 cells did not contribute to tamoxifen resistance in these cells. Third, a study of the function of estrogen receptor (ER) fl and ERflcx co-expressing with ERa, suggested that ERflcx would be a stronger modulator of ERa than ERr. These data indicate that a custom microarray is a useful tool for assessing the estrogen signaling pathway. Furthermore, DNA microarray could be a very efficacious application for predicting response to breast cancer treatments.