CXCR4 and breast cancer: Likewise, the chemokine receptor CXCR4 has multiple upstream mediators, with upregulation in renal cell carcinoma described in response to hypoxia inducible factor (HIF1a) [30] and galectin 1 [31], and in breast cancer with angiotensin II type I receptor (AGTR-1) and NF kappa B [32, 33].