Clinical Relevance of estrogen reactivity in the breast cancer microenvironment

Estrogen signals play an important role in the phenotype of estrogen receptor positive breast cancer. However, comprehensive analyses of the effect of estrogen signals on the tumor microenvironment and sur-vival in large cohorts of primary breast cancer patients have been lacking. We aimed to test the hypothesis that estrogen reactivity affects gene expression and immune cell infiltration profiles in the tumor microenvi-ronment and survival. A total of 3098 breast cancer cases were analyzed; 1904 from Molecular Taxonomy of Breast Cancer (METABRIC) cohort, 1082 from the cancer genome atlas (TCGA) cohort, and 112 from Hokkaido University hospital cohort. In Hokkaido University hospital cohot, Formalin-Fixed Paraffin-Embedded (FFPE) tissues were obtained from 112 breast cancer patients, who underwent breast surgery between 2005 and 2012 at Hokkaido University Hospital.