MMP9 and neoplasm: miR-34a-5p is down-regulated in CAF exosomes; miR-34a-5p overexpression suppressed cell proliferation, colony formation, migration, invasion, and reduced the weight of tumor nodules; overexpression of AXL, a target of miR-34a-5p, abolished the inhibitory effects of the miRNA through the AKT/GSK-3B/B-catenin signaling pathway, and subsequent up-regulation of SNAIL and activation of MMP-2 and MMP-9.