An instructive ductal microenvironment is key for efficient in vivo modeling of estrogen receptor positive breast cancer

Despite comprising 72% of all invasive breast cancers (1), and leading to a higher overall number of deaths than all other breast cancers combined, study of estrogen receptor positive (ER+) breast cancer in animal models has been hampered by numerous technical and biological problems which has made it difficult to effectively study to range of clinical subtypes that fall in this group. While each of the existing experimental systems has some favorable features, in many respects each is modeling a very particular aspect of breast cancer biology which may not be very generalizable to the diverse range of ER+ tumors arising in breast cancer patients.