Since we detected remarkable expression of cxcr4 in all of the five investigated human cerebral metastases of breast and lung carcinomas (Fig. 7A), we assessed the relevance of our qRT-PCR results in external gene sets, one from normal brain autopsies (GSE5389; n = 11), a second from breast (GSE14017, GSE14018; n = 22), and the third from lung adenocarcinoma brain metastasis (GSE14108; n = 28). Here, CXCR4 is linked to lung carcinoma.