RUNX2 and breast carcinoma: These results are consistent with studies showing the inhibitory effect of RA on metastasis from breast cancer cells to bone tissue (Xu and Jiang 2010) and RANKL-induced osteoclast differentiation and function (Lee et al. 2015) Therefore, RA enhances cell viability, differentiation, mineralization through stimulation of Runx-2 and OPG mRNA and protein expression and inhibition of RANKL expression during the differentiation of MC3T3-E1 osteoblastic cells into osteoblasts on the Ti surface (Figure 8).