CXCR4 and breast cancer: Whereas flow cytometric analysis revealed detectable constitutive CXCR4 surface expression in all eight cell lines evaluated, only four cell lines (CADO-ES, EW3, IOR/BER, RD-ES) demonstrated substantial levels of expression of this protein (Mean Fluorescence Intensity-ratio (over isotype control) >10), comparable to (positive control) breast cancer cell line MCF-7 (Figure3A).