Arid5a actually binds to the promoter of the Col2a1 gene and enhances transcription of Col2a1, which further induces acetylation of histone 3 proteins to regulate chondrocyte differentiation in association with Sox9. Recently, we observed that Arid5a regulates the invasion and metastasis of breast cancer cells (20). This evidence concerns the gene COL2A1 and breast cancer.