GPX3 is a key cholesterol-related gene associated with prognosis and tumorinfiltrating T cells in colorectal cancer

High cholesterol is an important factor inducing colorectal cancer (CRC). The study aims to determine the key genes and regulatory mechanism associated with tumor-infiltrating T cells underlying cholesterol-induced CRC. Gene expression data and clinical data from CRCS in The Cancer Genome Atlas (TCGA) were selected for differential expression and survival analysis. A total of 5,815 DEGs and 21 cholesterol-associated KEGG pathways were identified. Subsequently, 128 CRCs and 127 patients without obvious intestinal lesions were recruited to analyze the relationship between GPX3 expression, cholesterol levels, and pathologic condition. The results showed that the expression of cholesterol-related gene GPX3 was negatively associated with cholesterol level, but positively correlated with Ki-67 proliferation index in CRC. The expression of GPX3 was higher in CRC patients who were in poorly differentiated and advanced stage. In addition, a mice model of high-cholesterol diet intervention was constructed to detect the levels of cholesterol and GPX3 in the peripheral blood of mice, and it was found that the expression level of GPX3 in high-cholesterol mice was lower than that in normal diet mice. CD8(+) T cells were isolated from the spleen of mice and the T cell surface receptors were detected. It was found that the expression of CD69 in CD8(+) T cells of mice interfered with the high-cholesterol diet, while the expression of PD1, TIM-3, and CTLA-4 was increased. CD8(+) T cells were co-cultured with MC38 cells to detect the proliferation rate of CRC cells. The results showed that the tumor cell proliferation ratio in the high cholesterol group was higher than that in the control group. Furthermore, GPX3 downstream genes associated with m6A modification and tumor-infiltrating T cells were screened, and a T cell immune-related ceRNA network was constructed. In total, 53 GPX3 downstream genes associated with m6A modification and tumor-infiltrating T cells were identified. A PPI network that contained 45 nodes and 85 interaction pairs was constructed. The ceRNA network, including 39 miRNA-target and 43 lncRNA-miRNA regulatory pairs, was constructed. In conclusion, GPX3 is a potential target for cholesterol regulation of T cell immunity in CRC.