Consistently, the expression of differentiation marker and activation marker of osteoclasts, such as Acp5, Ctsk, Nfat-c1, C-fos, and Dc-stamp, were significantly upregulated in osteoclasts treated with CM from osteoblasts that pretreated with CM from NKX2-8-silenced breast cancer cells, but decreased in response to overexpression of NKX2-8 (Supplementary Figure 2). Here, CTSK is linked to breast cancer.