Fig. 3
From: Sympathetic activity in breast cancer and metastasis: partners in crime
The bone metastatic niche and the metastatic vicious cycle. Once engrafted in the bone, breast cancer cells secrete pro-osteoclastic factors such as PTHrP, PGE2, and MMPs, which induce the expression of RANKL by osteoblasts and osteocytes, promoting osteoclast differentiation and activity. In turn, factors released from the bone matrix enhance the growth of cancer cells, establishing a metastatic vicious cycle that leads to extensive bone degradation. NE, norepinephrine; BMSC, bone marrow stromal cell
