Inhibition of human glioblastoma cell invasion involves PION@E6 mediated autophagy process

Abstract

Background: Glioblastoma (GBM) is the most severe brain cancer due to its ability to invade surrounding brain tissue. Iron oxide nanoparticles (ION) could effectively induce a decrease of cell migration/invasion. Also IONs could generate ROS stress which induces autophagy elevation. Autophagy is associated with both anti-tumorigenesis and protumorigenesis. Objective: To explore the effect of PEGylated IONs (PION@E6) on the GBM cell invasion and its mechanism based on autophagy. Materials and methods: PION@E6 were prepared and characterized according to our previous study. After incubation of U251 cells with PION@E6, cellular uptake of PION@E6 and cell viability were tested by Prussian blue staining and Cell Counting Kit-8, respectively. The migration and invasive capability was assessed by transwell cell migration and invasion assay. Expressions of autophagy biomarkers were detected by Western blotting. Intracellular ROS level was determined using 2'-7'-dichlorodihydrofluorescein diacetate. Results: Average hydrate particle size and zeta potential of PION@E6 were 37.86±12.90 nm and -23.8 mV, respectively, and uniformly distributed nanoparticles with an average diameter of 10 nm were observed by TEM. Chlorin e6 successfully incorporated onto PION@E6 was demonstrated by ultraviolet and visible absorption spectrophotometry, and PION@E6 owning excellent water solubility and stability were showed by Colloid stability test. PION@E6 were successfully taken up by U251 cells with Prussian blue staining, and they showed in vitro cytotoxicity to glioma cells after long incubation of 72 hours. Migration/invasion of cells was significantly inhibited by PION@E6, which could be counteracted by pretreatment with 3-MA. Additionally, the expression of beclin-1, IC3I, and IC3II proteins was higher, whereas that of p62 protein was lower. Moreover, a dose dependent intracellular ROS generation of PION@E6 was detected. Conclusion: Invasiveness of human GBM cells involves the PION@E6-mediated autophagy process, which may be related to the intracellular ROS induced by PION@E6.