[LncRNA BCYRN1 regulates the miR-125a-5p/HK2 axis to influence radiosensitivity in glioma cells]

Objective: To investigate the effect and mechanism of long non-coding RNA brain cytoplasmic RNA 1 (lncRNA BCYRN1) on the radiosensitivity of glioma cells. Methods: The human glioma cell line U87 was irradiated with X-rays at doses of 0 Gy, 1 Gy, 2 Gy, 3 Gy, 4 Gy, 5 Gy, and 6 Gy for 24 h, and changes in BCYRN1 expression were detected by reverse transcription- quantitative polymerase chain reaction (RT-qPCR). U87 cells were divided into the following groups: control (routine culture), si-NC (transfected with negative control small interfering RNA), si-BCYRN1 (transfected with BCYRN1-targeting siRNA), si-NC+radiotherapy (transfected with si-NC followed by 4 Gy X-ray irradiation), si-BCYRN1+radiotherapy (transfected with si-BCYRN1 followed by 4 Gy irradiation), si-BCYRN1+inhibitor-NC+radiotherapy (co-transfected with si-BCYRN1 and inhibitor-NC followed by 4 Gy irradiation), si-BCYRN1+inhibitor+radiotherapy (co-transfected with si-BCYRN1 and miR-125a-5p inhibitor followed by 4 Gy irradiation), and si-BCYRN1+recombinant human hexokinase 2 (rhHK2)+radiotherapy (transfected with si-BCYRN1 and treated with rhHK2 followed by 4 Gy irradiation). After respective treatments, RT-qPCR was used to detect the expression of BCYRN1 and miR-125a-5p; Western blot was employed to measure the protein levels of HK2 and apoptosis-related proteins; cell proliferation was assessed by cell counting kit-8 (CCK-8) assay, 5-ethynyl-2'-deoxyuridine (EdU) staining, and colony formation assay; apoptosis was examined by Hoechst 33342 staining; and glycolysis levels were evaluated by glucose consumption and lactate production assays. Results: Compared with the 0 Gy group, the expression of BCYRN1 decreased with increasing radiation dose in the 1 Gy, 2 Gy, 3 Gy, and 4 Gy groups (all P＜0.05), while no significant difference was observed between the 5 Gy and 6 Gy groups and the 4 Gy group (both P＞0.05). Compared with the control and si-NC groups, the si-BCYRN1 and si-NC+radiotherapy groups showed down-regulated BCYRN1 mRNA expression (0.42±0.04 and 0.39±0.03, respectively), reduced HK2 protein expression (0.36±0.03 and 0.33±0.02), up-regulated miR-125a-5p expression (3.21±0.18 and 3.05±0.16), decreased cell viability, lower colony formation rate [(96.12±8.66)% and (54.67±5.45)%], increased apoptosis rate [(20.33±2.45)% and (18.92±2.15)%], reduced glucose consumption [(4.42±0.19) mmol/L and (5.92±0.51) mmol/L], and decreased lactate production [(4.27±0.52) mmol/L and (4.76±0.73) mmol/L]; all differences were statistically significant (all P＜0.05). Compared with the si-NC+radiotherapy group, the changes in the si-BCYRN1+radiotherapy group were more pronounced (all P＜0.05). Compared with the si-BCYRN1+inhibitor-NC+radiotherapy group, the si-BCYRN1+inhibitor+radiotherapy group exhibited down-regulated miR-125a-5p expression, reduced HK2 expression, increased cell viability, EdU-positive cell rate, and colony formation rate, decreased apoptosis rate, and elevated glucose consumption and lactate production (all P＜0.05). Compared with the si-BCYRN1+radiotherapy group, the si-BCYRN1+rhHK2+radiotherapy group showed up-regulated HK2 expression, increased cell viability, EdU-positive cell rate, and colony formation rate, decreased apoptosis rate, and significantly increased glucose consumption and lactate production (all P＜0.05). Conclusion: LncRNA BCYRN1 up-regulates HK2 by inhibiting miR-125a-5p expression, thereby promoting glycolysis and cell proliferation while suppressing apoptosis, which reduces the radiosensitivity of glioma cells.