BCAR3 and breast cancer: Another noteworthy putative STAT5 target gene, BCAR3 (breast cancer anti-estrogen resistance 3), which encodes a SRC homology 2 domain by which it may direct cellular signaling to increase cell motility and estrogen-independent proliferation in human breast cancer cells [64], was confirmed by qPCR to be significantly down-regulated by approximately 2-fold in MDA-MB-231 SH-4-54-resistant clones while being significantly up-regulated by at least 2-fold in T47D clones.