Abstract:

Objective To investigate the effect of etoposide-induced gene 24 （EI24） on the immune function of CD8⁺ T cells in the tumor microenvironment of thyroid cancer，as well as the regulatory mechanism of EI24 on the progression of thyroid cancer. Methods Totally，2 mL of venous blood was collected from 10 healthy subjects at the First Affiliated Hospital of Xinjiang Medical University from January to June 2024. Peripheral blood mononuclear cells （PBMC） were isolated using the immunomagnetic bead method，and CD8⁺ T cells were selected. The EI24 gene blank sequence，overexpression sequence and siRNA sequence of EI24 were constructed and transfected into CD8⁺ T cells. The cells were co-cultured with the thyroid cancer cell line SW579 at a ratio of 5∶1 for 48 h. The expression levels of PD-1，CD28 and CD69 on the surface of CD8⁺ T cells，the secretion levels of interferon-gamma（IFN-γ）and tumor necrosis factor-alpha（TNF-α），the apoptosis rate and the expression levels of EI24 gene，autophagy-related genes [microtubule-associated protein 1A/1B-light chain 3（LC3），p62] and apoptosis-related genes [cysteine-containing aspartate-specific protease-3（Caspase-3），Bcl-2] were determined. The proliferation，invasion and apoptosis of SW579 cells were also determined. Results Compared with blank control group，the relative expression levels of EI24 mRNA and protein in CD8⁺ T cells of overexpression group were increased （P<0.05），and the expressions of PD-1，CD28 and CD69 were increased（P<0.05）. The secretion levels of IFN-γ and TNF-α were increased（P<0.05），while the relative expression levels of LC3，p62 and Caspase-3 mRNA and protein were decreased（P<0.05），the apoptosis rate was decreased（P<0.05），and the relative expression levels of Bcl-2 mRNA and protein were increased（P<0.05）. The proliferation and invasion abilities of SW579 cells were decreased（P<0.05），and the apoptosis rate was increased（P<0.05）. In the low-expression group，the relative expression levels of EI24 mRNA and protein were decreased（P<0.05），and the expressions of PD-1，CD28 and CD69 were decreased（P<0.05）. The secretion levels of IFN-γ and TNF-α were decreased（P<0.05），while the relative expression levels of LC3，p62 and Caspase-3 mRNA and protein were increased （P<0.05），and the apoptosis rate was increased（P<0.05）. The proliferation and invasion abilities of SW579 cells were increased （P<0.05），and the apoptosis rate was decreased （P<0.05）. Conclusions High expression of EI24 gene can inhibit autophagy and apoptosis of CD8⁺ T cells，enhance their immune killing function，and thereby inhibit the malignant progression of thyroid cancer.

Key words: Etoposide-induced gene 24, CD8⁺ T cell, Immune, Autophagy, Thyroid cancer