CXCL12 and neoplasm: In particular, knocking down CXCR4 using RNAi or inhibiting CXCR4 function by AMD3100 in CSCs, impairs proliferation in vivo, effectively reducing tumor growth in two different xenograft models (Ping et al., 2011; Lee et al., 2013); similarly shRNA CXCL12 knock-down in CSCs inhibited tumor growth in vivo (Uemae et al., 2014).