Macrophages are required for proper mammary gland development and maintaining tissue homeostasis. However, the mechanisms by which macrophages regulate this process remain unclear. Here, we identify STAT5 as an important regulator of macrophage function in the developing mammary gland. Analysis of mammary glands from mice with STAT5-deficient macrophages demonstrates delayed ductal elongation, enhanced ductal branching and increased epithelial proliferation. Further analysis reveals that STAT5 deletion in macrophages leads to enhanced expression of proliferative factors such as Cyp19a1/aromatase and IL-6. Mechanistic studies demonstrate that STAT5 binds directly to the Cyp19a1 promoter in macrophages to suppress gene expression and that loss of STAT5 results in enhanced stromal expression of aromatase. Finally, we demonstrate that STAT5 deletion in macrophages cooperates with oncogenic initiation in mammary epithelium to accelerate the formation of estrogen receptor (ER)-positive hyperplasias. These studies establish the importance of STAT5 in macrophages during ductal morphogenesis in the mammary gland and demonstrate that altering STAT5 function in macrophages can affect the development of tissue-specific disease.
Bibliographical noteFunding Information:
The authors thank Alexandra Fuher, Taylor Croissant, Alex Nguyen, Pavlina Chuntova, Sarah Kemp, Dr. Laura Bohrer, Dr. Mariya Farooqui and Dr. Scott Dehm for their technical assistance with experiments. The authors also thank Dr. Lothar Hennighausen for providing the STAT5fl/fl mice and Dr. Jeffrey Rosen for providing HC-11 cells and MMTV-iFGFR1 transgenic mice. This work was supported in part by funds from NCATS UL1TR000114 (NJB), NCI 5T32CA009138 (NJB), NCI 5R01CA132827 (KLS), DOD W81XWH-16-1-0034 (KLS) and NCI 5R21CA184541 (KLS).
- Ductal morphogenesis
- Mammary gland