CYP19A1 and breast cancer: Having established an estrogen deficiency-driven high bone turnover state in OVX-Let mice by week three, MDA-MB-231 human breast cancer cells were inoculated into the left cardiac ventricle to generate a model of breast cancer metastatic to bone in order to determine the importance of aromatase inhibitor-induced changes to the bone microenvironment on tumor progression in the skeleton.