Human cytomegalovirus infection enhances invasiveness and migration of glioblastoma cells by epithelial-to-mesenchymal transition.

objectiveThis study aims to investigate the effect of human cytomegalovirus (HCMV) infection on epithelial-to-mesenchymal transition (EMT) in glioblastoma cells and the possible underlying molecular mechanism.

methodsWe established primary cell cultures and measured the expression of the HCMV immediate early protein (IE1) to determine HCMV infection by immunohistochemical assays. Human glioma cells were divided into four groups: primary HCMV-positive, primary HCMV-negative, HCMV-positive U87, and HCMV-negative U87 cells. Cells were treated with transforming growth factor (TGF-β1, 5 ng/ml) to induce EMT. Morphologic changes of the cells were observed microscopically at 0, 24, 48, and 72 h post TGF-β1 treatment. Following EMT induction, E-cadherin and vimentin were detected using RT-PCR. Expression of MMP-2, E-cadherin, and vimentin was measured by western blotting. The invasiveness of glioma cells was also measured using the Transwell migration assay and a wound-healing assay.

resultsMorphologic changes in primary glioblastoma cells and U87 cells were observed at different times after exposure to TGF-β1, and the extent of these changes was greater in HCMV-positive compared with HCMV-negative cells. Following exposure to TGF-β1, the transcription of E-cadherin was significantly lower in HCMV-positive primary cells and U87 cells compared with HCMV-negative cells (P<0.01), which was consistent with the results of western blotting. The expression levels of vimentin were also elevated in HCMV-positive cells at 48 and 72 h. HCMV-positive U87 cells were significantly more invasive and migratory than HCMV-positive primary cells. TGF-β1 and HCMV were observed to accelerate EMT and cell invasion by the Jun N-terminal kinase (JNK) pathway. Collectively, our findings indicate that HCMV and TGF-β1 promoted cell invasion and migration in glioma cells by the JNK pathway.

conclusionHCMV infection can promote EMT and strengthen the invasiveness of glioma cells.