COL1A1 and breast cancer: We utilized a syngeneic mouse model of bone metastasis by using the EO771 breast cancer cell line in mice harboring a conditional deletion of MERTK and TYRO3 in osteoblasts (Col1a1-2,3kb-cre+Mertkflox/flox and Col1a1-2,3kb-cre+Tyro3flox/flox).