HMGB1 and brain cancer: Intriguingly, RAGE knockout mice displayed an osteopetrotic phenotype due to defects in osteoclast maturation and function.36 High-mobility group box 1 (HMGB1) was suggested as a ligand of RAGE in support of osteoclastogenesis.37 In addition, the HMGB1–RAGE interaction has been shown to have significant roles in the metastasis of lung and brain cancers.33 However, our microarray analysis showed that HMGB1 expression was lower in MDA cells than in MCF7 cells, suggesting that HMGB1 is unlikely to contribute to the osteoclastogenesis occurring in breast cancer metastasis.