CXCL12/CXCR4 axis induced miR-125b promotes invasion and confers 5-fluorouracil resistance through enhancing autophagy in colorectal cancer

The activation of CXCL12/CXCR4 axis is associated with potential progression of cancer, such as invasion, metastasis and chemoresistance. However, the underlying mechanisms of CXCL12/CXCR4 axis and cancer progression have been poorly explored. We hypothesized that miRNAs might be critical downstream mediators of CXCL12/CXCR4 axis involved in cancer invasion and chemoresistance in CRC. In human CRC cells, we found that the activation of CXCL12/CXCR4 axis promoted epithelial-mesenchymal transition (EMT) and concurrent upregulation of miR-125b. Overexpression of miR-125b robustly triggered EMT and cancer invasion, which in turn enhanced the expression of CXCR4. Importantly, the reciprocal positive feedback loop between CXCR4 and miR-125b further activated the Wnt/β-catenin signaling by targeting Adenomatous polyposis coli (APC) gene. There was a negative correlation of the expression of miR-125b with APC mRNA in paired human colorectal tissue specimens. Further experiments indicated a role of miR-125b in conferring 5-fluorouracil (5-FU) resistance in CRC probably through increasing autophagy both in vitro and in vivo. MiR-125b functions as an important downstream mediator upon the activation of CXCL12/CXCR4 axis that involved in EMT, invasion and 5-FU resistance of CRC. These findings shed a new insight into the role of miR-125b and provide a potential therapeutic target in CRC.