Fig 2: The potential mechanism of LINC00839 inhibiting ferroptosis in NPC.ELK1 binds to LINC00839 promoter and promotes its transcription. LINC00839 binds to UPF1 and lowers the mRNA stability of RCHY1. Downregulation of RCHY1 represses DJ-1 ubiquitination and degradation, leading to NPC cell resistance to ferroptosis.

Fig 3: ELK1 directly binds to LINC00839 promoter to activate its transcription.A JASPAR database predicted the binding motif of transcription factor ELK1. B The putative binding sites of ELK1 to LINC00839 promoter were predicted by JASPAR database. C ChIP assay validated the enrichment of binding sites in LINC00839 promoter after immunoprecipitation by ELK1 antibody. D, E The expression level of ELK1 in NPC cells transfected with shNC or shELK1#1/2 was determined by qRT-PCR and western blotting. F The interaction between ELK1 and LINC00839 promoter site 1/2 was determined by dual-luciferase reporter assay in ELK1-depleted NPC cells. G The binding of ELK1 to LINC00839 promoter in ELK1-depleted NPC cells was detected by ChIP assay. H Pearson correlation analysis of ELK1 and LINC00839 levels in NPC tissues (n = 30). I qRT-PCR evaluated the expression level of LINC00839 in NPC cells after ELK1 overexpression or knockdown. J The correlation between ELK1 and LINC00839 in HNSC was analyzed by ENCORI database (n = 502). *P < 0.05, **P < 0.01, and ***P < 0.001.

Fig 4: Loss of ELK1 or LINC00839 enhanced anti-cancer efficiency of Sorafenib by boosting ferroptosis.NPC/HK1 or C666-1 cells stably infected with lentiviruses carrying shELK1#1, shLINC00839#1, or shNC were subcutaneously injected into BALB/c nude mice. There were 7 experimental groups (n = 6 per group): control, Sorafenib, shNC, shELK#1, shLINC00839#1, shELK#1+Sorafenib, shLINC00839#1+Sorafenib. The mice in Sorafenib groups were intraperitoneally injected with 10 mg/kg Sorafenib every other day after 5 days of transplantation. A Xenograft tumors of nude mice in each group. B Growth curve of xenograft tumors in each group. C The tumor weight of xenograft tumors in each group. D LINC00839 expression in xenograft tumor tissues was measured by qRT-PCR. E Protein levels of ELK1, RCHY1, DJ-1, SLC7A11, GPX4, Nrf2, and HO-1 in tumors were evaluated by western blotting. F 4-HNE expression was detected by immunohistochemical staining. Scale bar, 50 μm. *P < 0.05, **P < 0.01, and ***P < 0.001.

Fig 5: Overexpression of ELK1 or LINC00839 induces ferroptosis resistance of NPC cells.A, B The expression level of ELK1 in NPC cells transfected with ELK1 overexpression vector or control vector was detected by qRT-PCR and western blotting. C The expression level of LINC00839 in NPC cells transfected with LINC00839 overexpression vector or control vector was detected by qRT-PCR. D NPC cells transfected with ELK1 or LINC00839 overexpression vector were exposed to various concentrations of Erastin (2.5, 5, 10, 20, 40 μM) or RSL3 (0.1, 0.5, 1, 5, 10 μM) for 24 h. Cell viability was assessed by CCK-8 assay. E MDA, F iron, G Fe2+, H GSH levels were determined in NPC cells transfected with ELK1 or LINC00839 overexpression vector after treatment with Erastin (10 μM) or RSL3 (1 μM) for 24 h. I Lipid ROS level was measured by C11-BODIPY 581/591 probe and flow cytometry. J Western blotting analysis of DJ-1, GPX4, and SLC7A11 protein abundance. *P < 0.05, **P < 0.01, and ***P < 0.001.