Various studies have devised methylation biomarkers for diverse cancers like lung, colorectal, cervical, and bladder cancers, which find application in clinical diagnosis (Han et al., 2019; Tang et al., 2019; Roy and Tiirikainen, 2020; Chang et al., 2023), such as the three-gene methylation biomarker (SHOX2/RASSF1A/PTGER4) for lung cancer (Kneip et al., 2011; Weiss et al., 2017; Malpeli et al., 2019). The gene discussed is PTGER4; the disease is lung cancer.