Abstract P2-20-16: Hormone receptor expression is associated with specific immunological profiles in the breast cancer microenvironment

Abstract Purpose: Elucidating the unique immunomodulatory mechanisms in breast cancer microenvironment should provide useful insights to aid the development of new therapeutic strategies for this disease. Some studies suggested the immune regulatory function of hormone receptor such as estrogen receptor-α (ER) and androgen receptor (AR), but their mechanism has not been fully understood because of the complexity of immune milieu in breast cancer microenvironment. In this study, we systematically analyzed the relationships between ER, progesterone receptor (PgR), and AR expression and the immunological profile in breast cancer tissue. Methods: Gene set enrichment analysis (GSEA) was used to screen the biological processes associated with the expression of human sex hormone receptor genes (ESR1, PGR, and AR), using a gene expression profile dataset of the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC). Then, using METABRIC and a gene expression profile dataset of The Sweden Cancerome Analysis Network - Breast (SCAN-B), the correlation between the immune cell composition in breast cancer tissue (estimated with the CIBERSORTx) and hormone receptor expression was analyzed. In our previous study of 45 breast cancer tissues, we evaluated the level of human tumor infiltrating lymphocytes (hTILs), expression of human programmed death-ligand 1 (hPD-L1), and infiltration of 11 types of immune cells, using hematoxylin–eosin staining, immunohistochemistry (IHC), and multicolor flow cytometry, respectively. In this study, the levels of ER, PgR, and AR expression were further evaluated using IHC, and their relationship with the immunological profile of breast cancer tissues was analyzed. Results: GSEA showed that the expression levels of the ESR1, PGR, and AR genes were negatively correlated with multiple immunological processes, including “INFLAMMATORY RESPONSE.” Analysis of the correlations between the immune cell composition and hormone receptor gene expression showed that ESR1 expression was inversely correlated with Macrophage M1, CD4 memory activated T cells, Macrophage M0, CD8 T cells, and CD4 memory resting T cells; PGR expression was inversely correlated with Macrophage M1, CD4 memory activated T cells, and Macrophage M0; and AR expression was inversely correlated with Macrophage M0 and Macrophage M1. Immunohistochemical evaluation of ER and AR expression revealed both receptors to be inversely associated with hTIL, hPD-L1 expression, and leukocyte infiltration in breast cancer tissue. Analysis of the immune cell composition in these tissues revealed that ER expression was associated with the decreased infiltration of total T cells, CD4+ T cells, monocytes/macrophages, myeloid-derived suppressor cells, dendritic cells, and myeloid dendritic cells; PgR expression was associated with the decreased infiltration of dendritic cells; and AR expression was associated with the decreased infiltration of CD4+ T cells, monocytes/macrophages, nonclassical monocytes, myeloid-derived suppressor cells, dendritic cells, myeloid dendritic cells, and minor natural killer cells. Conclusion: The correlation of hormone receptor expression with specific immunological profiles in the breast cancer microenvironment both at the genetic and protein levels strongly suggests that hormonal signals may preferentially affect certain subsets of immune cells. Citation Format: Toru Hanamura, Shigehisa Kitano, Hiroshi Kagamu, Makiko Yamashita, Mayako Terao, Takuho Okamura, Nobue Kumaki, Katsuto Hozumi, Takayuki Iwamoto, Chikako Honda, Sasagu Kurozumi, Naoki Niikura. Hormone receptor expression is associated with specific immunological profiles in the breast cancer microenvironment [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-20-16.