RESUMEN

Objective:To investigate the effect of estrogen-related receptor α (ESRRA)-mediated lipophagy on the proliferation and migration abilities of nasopharyngeal carcinoma cells.Methods:A total of 16 clinical samples diagnosed by pathology in the Affiliated Hospital of Nantong University from 2021 to 2023 were selected, including 8 normal nasopharyngeal mucosa tissues and 8 nasopharyngeal carcinoma tissues. Immortalized normal nasopharyngeal epithelial cell line NP69 and nasopharyngeal carcinoma cell lines C666-1, CNE2, TW03-EBV and TW03 were selected. The cell lines C666-1 and CNE2 were divided into the siR-NC group (transfected with small interfering RNA negative control sequence) and siR-ESRRA group (transfected with small interfering RNA against ESRRA gene). The relative expression levels of ESRRA were detected by Western blotting and immunohistochemical assay. EdU assay was used to detect the proliferation ability of C666-1 and CNE2 cells, and Transwell assay was used to detect the migration ability. Real-time fluorescence quantitative polymerase chain reaction (qRT-PCR) was used to detect the relative expression levels of ESRRA and perilipin 3 (PLIN3) mRNA. The formation of lipophagy in C666-1 and CNE2 cells was observed by transmission electron microscopy. The co-localization of LC3, PLIN3 and LAMP2 with lipid droplets labeling with Bodipy was detected by immunofluorescence assay. Dual-luciferase reporter gene assay was used to verify the targeting relationship between ESRRA and PLIN3.Results:The relative expression level of ESRRA in nasopharyngeal carcinoma tissues was higher than that in normal nasopharyngeal mucosa tissues(1.15±0.75 vs. 0.32±0.21, t = 3.02, P = 0.009). The relative expression level of ESRRA in nasopharyngeal carcinoma cell lines C666-1 (1.539±0.044), CNE2 (1.420±0.030), TW03-EBV (2.867±0.044), and TW03 (1.323±0.022) were higher than that in normal nasopharyngeal epithelial cell line NP69 (0.094±0.002), and the difference was statistically significant ( F = 34.08, P < 0.001).The results of EdU assay showed that the proportions of EdU labeled positive cells in CNE2 cells of siR-NC group and siR-ESRRA group were (70.44±4.06)% and (51.51±0.92)% ( t = 7.88, P = 0.001), and the proportions in C666-1 cells were (62.25±3.89)% and (54.91±0.27)% ( t = 3.26, P = 0.031). The results of Transwell assay showed that the number of migrating cells in CNE2 and C666-1 cells was less than that in siR-NC group [CNE2 cells: (181±7) cells vs. (261±21) cells; C666-1 cells: (201±16) cells vs. (256±7) cells], and the differences were statistically significant ( t = 6.30, P = 0.003; t = 5.43, P = 0.006). According to qRT-PCR results, the relative expression level of PLIN3 mRNA in the siR-ESRRA group was higher than that in the siR-NC group (CNE2 cells: 1.58±0.16 vs. 0.83±0.17, t = 5.59, P = 0.005; C666-1 cells: 1.37±0.12 vs. 1.06±0.06, t = 3.86, P = 0.018). The dual-luciferase reporter gene assay results indicated a targeted binding interaction between PLIN3 and ESRRA. Transmission electron microscopy observation showed that the lipid droplets in nasopharyngeal carcinoma cells increased and the binding to autophagosomes decreased after knockdown of ESRRA. The results of immunofluorescence assay demonstrated that, in contrast to the siR-NC group, there was a decrease in the co-localization of LC3 and LAMP2 and an increase in the co-localization of lipid droplets with PLIN3. Conclusions:ESRRA is highly expressed in nasopharyngeal carcinoma tissues and cells. As a transcription repressor, ESRRA may work to prevent PLIN3 from being transcribed, decrease lipid droplet stability, mediate lipophagy, and promote proliferation and migration of nasopharyngeal carcinoma cells.