CXCR4 and cancer: Recently, miR-9 has been discovered to be involved in modulating cellular processes through regulating the expression of several target genes such as E-cadherin [32], Foxo3a [33], NF-κB1 [34] and CXCR4 [35] et al. High expression levels of miR-9 were observed to promote multiple cancer cells proliferation, invasion and migration [36, 37], while knock-down of miR-9 could inhibit cancer cell growth in vitro [38].