MiR-155 up-regulation by LMP1 DNA contributes to increased nasopharyngeal carcinoma cell proliferation and migration

Regulation of oncogenic or tumor-suppressive microRNAs expression by Epstein-Barr virus (EBV) and the correlation of EBV with the nasopharyngeal carcinoma (NPC) have cast new light on the cause of NPC. The present study is to determine the association of miR-155 with EBV-positive NPC, and to evaluate the oncogenic role of miR-155 in cell proliferation, migration and invasion of NPC cells. The miR-155 expression was determined by real-time RT-qPCR; The oncogenic promotion of miR-155 was evaluated by by cell colony formation assay, proliferation assay, scratch assay and transwell migration assay. It showed that miR-155 expression was up-regulated in EBV-positive NPC tissue samples and was correlated with plasma LMP1 DNA copies. Expression of miR-155 was also up-regulated in NPC cell lines post-transfecting with LMP1-expressing plasmid. Up-regulated miR-155 stimulated the capability of NPC cell proliferation, colony formation, cell migration and invasion. Therefore, miR-155 is up-regulated in NPC tissues, with a correlation with plasma LMP1 DNA copies, and is significantly induced in NPC cells by LMP1 in vitro. The oncogenic miR-155 promotes NPC cell proliferation, migration and invasion significantly in vitro.