ETV4 transcriptionally activates STAT6 to inhibit ferroptosis and promote immune escape in thyroid cancer.

[BACKGROUND] Thyroid cancer (THCA) is one of the most common endocrine malignancies, with a significant increase in incidence over the past few decades. ETS variant transcription factor 4 (ETV4) is a member of the ETS family of transcription factors, which play crucial roles in tumorigenesis. However, the precise mechanisms by which ETV4 contributes to THCA progression remain largely unexplored.

[METHODS] The expression levels of ETV4, programmed death-ligand 1 (PD-L1), signal transducer and activator of transcription 6 (STAT6), and solute carrier family 7 member 11 (SLC7A11) were analyzed using quantitative reverse transcription PCR (qRT-PCR) and western blotting assays. Cell viability was assessed using the Cell Counting Kit-8 (CCK-8) assay. Reactive oxygen species (ROS) levels and apoptosis were evaluated by flow cytometry. Colorimetric assays were employed to measure malondialdehyde (MDA) levels, glutathione (GSH) levels, iron (Fe) levels, and lactate dehydrogenase (LDH) cytotoxicity. Enzyme-linked immunosorbent assay (ELISA) was used to quantify interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and interleukin-2 (IL-2) levels. The interaction between ETV4 and STAT6 was confirmed using a dual-luciferase reporter assay and chromatin immunoprecipitation (ChIP) assay.

[RESULTS] ETV4 expression was upregulated in THCA tissues and cells. Its knockdown increased ROS, MDA, and Fe, decreased GSH and SLC7A11, and reduced PD-L1 expression. Silencing ETV4 enhanced CD8 T cell cytotoxicity and elevated secretion of IFN-γ, TNF-α, and IL-2, while promoting apoptosis. STAT6 expression was upregulated in THCA tissues and positively correlated with ETV4 expression. Mechanistically, ETV4 transcriptionally activated STAT6 in FTC-133 cells, and STAT6 overexpression inhibited ferroptosis and promoted immune escape by interacting with ETV4.

[CONCLUSION] ETV4 transcriptionally activated STAT6 to inhibit ferroptosis and promote immune escape in THCA. Targeting the ETV4-STAT6 axis may offer a novel therapeutic strategy, potentially inhibiting ferroptosis and enhancing immune response in THCA patients.