Rab18 is a potential molecular biomarker for diagnosis and assessing the progression of human gliomas

Abstract

Objective To investigate the mechanism by which Rab18 affects proliferation and apoptosis of human glioma cells and assess the value of Rab18 as a biomarker for diagnosis and evaluating the progression of gliomas. Methods Human glioma U87 cells were transfected with a small interfering RNA (siRNA) targeting Rab18 or a negative control siRNA. The changes in mRNA and protein expression of Rab18 and apoptosis-related proteins were detected with qRT-PCR and Western blotting, and the cell proliferation was assessed using CCK-8 test; the changes in cell cycle and cell apoptosis were analyzed using flow cytometry. We also collected surgical specimens of human glioma tissues (n=33) and adjacent normal brain tissues (n=15) from patients who never received chemotherapy or radiotherapy prior to the surgery for histological examination with HE staining and analysis of Rab18 mRNA and protein expression in relation with the pathological grade of the tumors. Results The mRNA and protein expression levels of Rab18 were significantly downregulated in U87 cells after Rab18 silencing (P < 0.01), which induced not only cell cycle arrest in G0/G1 phase and reduced percentage of S phase cells (P < 0.01) but also upregulated the mRNA and protein expression levels of the apoptosis-related proteins P53, caspase7, Bax, and Bim (P < 0.01). In the surgical specimens, the gliomas expressed significantly higher levels of Rab18 than the adjacent tissues (P < 0.01), and the expression levels of Rab18 were significantly higher in high-grade gliomas (WHO Ⅲ~Ⅳ, n=19) than in the low-grade gliomas (WHO Ⅰ~Ⅱ, n=14; P < 0.01). Conclusion Rab18 silencing not only inhibits cell proliferation but also promotes cell apoptosis in human glioma cells. Its expression level is related with the malignancy of the tumor, suggesting its value as a potential molecular biomarker for diagnosis and evaluating progression of human glioma.

Keywords

• rab18
• glioma
• apoptosis
• proliferation
• diagnosis
• progression