The Mechanisms Of CXCL5/CXCR2 Axis Promoting Colorectal Cancer Progression And Metastasis

Metastasis is a major cause of death in human colorectal cancer patients.Chemokines in tumor microenvironment play an important role on colorectal cancer progression and metastasis.However,mechanisms of chemokines in tumor microenvironment tumor progression and metastasis is not fully understood.Herein,we addressed this issue above by detecting several chemokines in colorectal cancer patients and revealed the expression profiles of the chemokines in CRC.We compared the distinct changes in several chemokines between the tumor and peritumoral normal tissues using a chemokine ELISA array.By setting a threshold of at least a 2-fold upregulation,we found that CXCL5 is overexpressed in tumor tissues.Secondly,the expression levels of CXCL5 were examined in tissue microarrays including 78 pairs of CRC samples and the association between CXCL5 and colorectal cancer patients' clinical materials was also analysed.We found that CXCL5 was associated with advanced tumor stage as well as poor prognosis in colorectal cancer patients.We also identified the prognostic significance of CXCR2 in colorectal cancer patients.We retrospectively analysed 134 patients with colorectal cancer who underwent minimally invasive surgery.We detected CXCR2 expression using immunohistochemical staining.Next,we analysed the association between CXCR2 expression and clinicpathologic features.High expression of CXCR2 was associated with Dukes stage,tumor invasion and liver metastasis.Multivariate COX regression analyses confirmed that high CXCR2 level was an independent prognostic risk factor for both overall survival and disease free survival.Kaplan-Meier survival analysis demonstrated that patients with high expression of CXCR2 had a poor overall survival and disease free survival even in low-risk group(I+II).This indicated that CXCR2 can help to refine individual risk stratification.Moreover,we found the combination of CXCR2 and its ligand CXCL5 had more significant value in predicting the prognosis than single CXCR2 factor.In addition,overexpression of CXCL5 enhanced colorectal cancer cells migration a through inducing epithelial-mesenchymal transition(EMT)based on ERK/Elk-1/Snail pathway in a CXCR2-dependent manner.We investigated the biological changes of cells with high and low expression of CXCL5 and found that the ectopic expression of CXCL5 promoted the migration of CRC cell lines compared with the control group.Moreover,we also observed that ectopic expression of CXCL5 can induce a mesenchymal,spindle-like morphology and lower levels of E-cadherin and ZO-1,as well as an upregulation of N-cadherin and Vimentin in colorectal cancer cells compared with control group.Inhibition of CXCR2 was able to reverse the promoting effect of CXCL5.These results indicate that CXCL5 is able to promote CRC cell migration by inducing EMT in a CXCR2-dependent manner.Ectopic CXCL5 expression activated the ERK and AKT pathways.Our results demonstrated that the inhibition of ERK pathway rather than AKT pathway changed the cellular morphology and reversed the effects of CXCL5 on migration.Meanwhile,inhibition of the ERK pathway decreased the levels of pElk-1,which indicates that pElk-1 may act as downstream effector of the ERK pathway.Inhibition of the ERK pathway using U0126 also decreased the expression of Snail.These results suggest that the CXCL5/CXCR2 axis induces EMT to promote CRC cell migration via the ERK/Elk-1/Snail pathway.We next assessed the contribution of the CXCL5/CXCR2 axis to CRC cell invasion.Ectopic expression of CXCL5 was able to promote cell invasion,the knock-down of CXCR2 also reduced the number of invading cells.Moreover,CXCL5 enhanced the translocation of ?-catenin to the nucleus.The inhibition of CXCR2 led to an accumulation of ?-catenin in the cytoplasm instead of translocation to the nucleus.CXCL5-enhanced activation of AKT pathway may be able to increase ?-catenin and MMP7 levels in CRC cells in a CXCR2-dependent manner.These data indicate that CXCL5 is able to promote CRC cell invasion in a CXCR2-dependent manner.This process may involve regulation of the AKT/GSK3?/?-catenin /MMP7 pathway.Elevated expression of CXCL5 can also potentiate colorectal cancer cells liver metastasis in vivo nude mice intrasplenic injection model.In conclusion,our results indicate that CXCL5 is over-expressed in CRC,which is predictive of a poor prognosis for CRC patients.We also demonstrate a novel role for CXCL5 in the induction of EMT and promotion of CRC cell migration through the ERK/Elk-1/Snail pathway in a CXCR2-dependent manner.Furthermore,we reveal that CXCL5/CXCR2 can potentiate CRC cell invasion via the AKT/GSK3?/?-catenin/MMP7 pathway rather than the ERK pathway.Thus,inhibition of the CXCL5/CXCR2 signaling pathway may be a promising target for therapies for CRC patients.