CXCR4 and breast cancer: ABCG2 expression is controlled by several different transcriptional factors, including ESR1 (Mo and Zhang, 2012) which here was downregulated on the protein level in 3D relative 2D cultured cells, supporting a downregulation of ABCG2. 3D cultured cells were also shown to have an increased matrix remodeling profile relative 2D cultured cells by increased levels of a matrix degrading protease (MMP9), a chemotaxis receptor (CXCR4), as well as reduced levels of the CXCR4-related chemokine (CXCL12) whose downregulation is suggested to promote breast cancer metastasis (Yu et al., 2017).