The results of this study showed that the methylation positivity rates of SHOX2, RASSF1A and PTGER4 genes in cancer tissues of LC patients were 48.00%, 32.00% and 64.00%, respectively, which were significantly higher than those in paracancerous tissues (16.00%, 4.0% and 14.00%), indicating that the methylation positivity rates of SHOX2, RASSF1A and PTGER4 genes were higher in cancer tissues of LC patients. Here, PTGER4 is linked to cancer.