Profile of miRNAs in small extracellular vesicles released from glioblastoma cells treated by boron neutron capture therapy.

Purpose: Boron neutron capture therapy (BNCT) is a tumor cell-selective particle-radiation therapy. In BNCT, administered p-boronophenylalanine (BPA) is selectively taken up by tumor cells, and the tumor is irradiated with thermal neutrons. High-LET α-particles and recoil Li, which have a path length of 5-9 μm, are generated by the capture reaction between B and thermal neutrons and selectively kill tumor cells that have uptaken B. Although BNCT has prolonged the survival time of malignant glioma patients, recurrences are still to be resolved. miRNAs, that are encapsulated in small extracellular vesicles (sEVs) in body fluids and exist stably may serve critical role in recurrence. In this study, we comprehensively investigated microRNAs (miRNAs) in sEVs released from post-BNCT glioblastoma cells.

Method: Glioblastoma U87 MG cells were treated with 25 ppm of BPA in the culture media and irradiated with thermal neutrons. After irradiation, they were plated into dishes and cultured for 3 days in the 5% CO incubator. Then, sEVs released into the medium were collected by column chromatography, and miRNAs in sEVs were comprehensively investigated using microarrays.

Result: An increase in 20 individual miRNAs (ratio > 2) and a decrease in 2 individual miRNAs (ratio < 0.5) were detected in BNCT cells compared with non-irradiated cells. Among detected miRNAs, 20 miRNAs were associated with worse prognosis of glioma in Kaplan Meier Survival Analysis of overall survival in TCGA.

Conclusion: These miRNA after BNCT may proceed tumors, modulate radiation resistance, or inhibit invasion and affect the prognosis of glioma.