Non-contact co-culture with human vascular endothelial cells promotes epithelial-to-mesenchymal transition of cervical cancer SiHa cells by activating the NOTCH1/LOX/SNAIL pathway

BACKGROUND: The aim of this study was to investigate the effect of human umbilical vein endothelial cells on epithelial-to-mesenchymal transition of the cervical cancer cell line SiHa by studying the Notch1/lysyl oxidase (LOX)/SNAIL1 pathway. METHODS: Monocultures of SiHa cells, SiHa cells containing a control sequence, and Notch1-silenced SiHa cells, as well as co-cultures of human umbilical vein endothelial cells with SiHa cells and Notch1-silenced SiHa cells, were established. The invasiveness of SiHa cells in each group was evaluated using a Transwell assay. The mRNA levels of E-cadherin and vimentin were detected using quantitative real-time polymerase chain reaction. The expression levels of the matrix metalloproteinases MMP-2 and MMP-9 were determined in SiHa cells using an immunofluorescence assay and the protein activity was detected by gelatin zymography. Changes in LOX, SNAIL1 and NOTCH1 expression in the SiHa cells in each group were detected using western blotting. RESULTS: Compared with monocultured SiHa cells, co-cultured SiHa cells showed a significant increase in their invasiveness and expression levels of vimentin, as well as of NOTCH 1, LOX, and SNAIL1, whereas their expression of E-cadherin was significantly reduced and protein activities of MMP-2 and MMP-9 were increased. Compared with SiHa, mono- and co-cultured NOTCH 1-silenced SiHa cells showed significant reductions in their invasiveness and expression levels of vimentin, NOTCH 1, LOX, and SNAIL1, whereas their expression of E-cadherin significantly increased and protein activities of MMP-2 and MMP-9 decreased. CONCLUSION: Co-culture with human umbilical vein endothelial cells promoted the epithelial-to-mesenchymal transition of SiHa cells by activating the NOTCH1/LOX/SNAIL1 pathway in SiHa cells, which enhanced their invasive and metastatic capacities. The results of this study may provide a new perspective on cervical cancer metastasis and a theoretical basis for clinical treatment.