CXCL12 and breast cancer: In addition, the study of 1904 human BC samples from public DNA microarrays15 showed an inverse correlation between FAAH and CXCR4/CXCL12 mRNA levels in human tumors (Fig. 6c), and GSEA analysis of the 286 human BC samples included in the Wang dataset26 revealed an activation of the CXCR4 pathway40 in human BC tumors with low FAAH expression (Supplementary Fig. 9b).