Y-box Binding Protein?1 Promotes The Initiation And Progression Of Colorectal Cancer By Regulating Epithelial Mesenchymal Transition

Objective:To explore the biological role and related molecular mechanism of Y?box binding protein?1(YB-1) in the initiation and progression of colorectal cancer(CRC).Methods: 1.Immunohistochemistry was performed to detect expression of YB-1 in 170 primary CRC tissues and their matched normal tissues, and its clinical significance was evaluated by statistical methods. 2. Small interfering RNA(si RNA) was performed to downregulate YB-1 expression in HT-29 colon adenocarcinoma cells. MTT assay, apoptosis assay, transwell migration and invasion assay were then employed to investigate the biological role of cancer cells. RT-PCR and western blot were employed to detect the expression of Epithelial Mesenchymal Transition(EMT) markers in cancer cells. The expression of YB-1 and EMT markers in 80 CRC tissues were detected by Immunohistochemistry. The relationship between YB-1 and EMT markers was identified by correlation analysis. 3. The expression of N-cadherin in CRC tissues and their matched nomal tissues was detected by western blot andImmunohistochemistry. The si RNA was then employed to downregulate the expression of N-cadherin in HT-29 colon adenocarcinoma cells. The proliferative and migratory ability of cancer cells were subsequently evaluated by MTT assay and wound healing assay respectively. RT-PCR was also employed to detect the expression of N-cadherin and E-cadherin in cancer cells.Results: 1. The expression of YB-1 was was significantly correlated with tumor differentiation, tumor invasion and lymph node metastasis(all P<0.05). Patients with high YB-1 expression had a poorer prognosis and were more likely to undergo local recurrence, compared to those with low YB-1 expression. YB-1 expression was identified as an independent prognostic factor for the overall survival of CRC patients. 2. After downregulating YB-1 expression, cell proliferation, apoptosis resistance, invasion and migration were dramatically inhibited(all P<0.05). More importantly, following downregulation of YB?1, E?cadherin expression was elevated whereas N?cadherin and vimentin expression was reduced. Furthermore, YB?1 expression was negatively correlated with E?cadherin but positively correlated with N?cadherin and vimentin expression in CRC tissues(all P<0.05). 3. N-cadherin expression was higher in tumor tissues than that in their adjacent normal tissues. N?cadherin expression was significantly associated with tumor differentiation, tumor size as well as tumor and nodes stage(all P<0.05). N-cadherin expssion was negatively correlated with E-cadherin expression in CRC tissues. Patients with high N-cadherin expression had a signifiantly lower overall survival and disease?free survival rate than those with low N-cadherin expression, while the opposite was found for E-cadherin. Also, N-cadherin expression was an independent prognostic factor for the overall survival of CRC patients. In vitro assays, N-cadherin was widely expressed in CRC cell lines and silencing of N-cadherin suppressed the proliferation and migration of HT-29 cells by upregulating E-cadherin.Conclusion: YB-1 promotes the initiation and progression of CRC by regulating EMT. N-cadherin, as a mesenchymal marker of EMT, also plays an important role in CRC development. Reversing EMT by targeting YB-1 has the potential to be a novel therapeutical strategy for CRC.