Expression Profiling of the Estrogen Responsive Genes Using DNA
Microarrays for Hormone-based Assays in Diagnosis, Drug Screening
and Environmental Monitoring
Ryoiti Kiyama
Institute of Molecular and Cell Biology, National Institute of Advanced Industrial Science
and Technology, Tsukuba, Ibaraki 305-8566, and InfoGenes Co., Ltd., Tsukuba, Ibaraki
305-0047, Japan
Hormones are the micromedia that deliver information from cells to cells to maintain
normal physiological and developmental conditions for the cells. In response to the
stimulation mediated by a wide variety of materials and signals, after they are incorporated
into cells, a number of genes respond in a number of ways specific to the types of the
stimulation, materials and cells. Therefore, the cellular responses to hormones and the
effects of such responses can be monitored by examining or profiling the responses by the
genes, which is essential for the application of hormone-based assays. We developed a
microarray-based technique for diagnosis, drug screening and environmental monitoring by
means of profiling estrogen responsive genes using custom microarrays. Estrogen is a
member of the steroid-thyroid hormones and regulates development and maintenance of
female phenotype and behavior. Approximately 200 cDNAs from the genes and ESTs
(expressed sequence tags) were selected after screening approximately 9,200 genes for the
estrogen response and they were spotted on a custom microarray. The genes and ESTs
selected were classified into several groups according to their functions, cancer-related
genes, the genes for growth and proliferation, and others. Using the custom microarray, we
first investigated the time course of the responses of the genes in MCF-7 cells to an
estrogen, 17β-estradiol. The results were confirmed by Northern blot analysis. The estrogen
responsive genes were further classified according to this result into the early and late
responding types. This microarray system can be used in two different major fields:
diagnosis and drug screening, and environmental monitoring. Both systems need accurate
and high throughput analysis of cellular responses, which can be monitored by the gene
response. In the first field, the custom microarray analysis of estrogen receptor-positive
breast cancer tissues showed similar but not identical profiles to those of cell lines,
indicating the usefulness of this custom microarray for prediction of the effectiveness of
hormone therapy in the human breast cancer. In the second field, gene expression profiling
of environmental hormones, or endocrine disruptors, will be a useful tool for monitoring
effects of industrial chemicals, and natural and artificial biomaterials.