PTGER4 and lung cancer: There are some lung cancer biomarker candidates that are currently being tested in large cohorts, such as seven autoantibodies (p53, NY-ESO-1, CAGE, GBU4-5, SOX2, HuD, and MAGE A4), complement fragments C4d, microRNAs, circulating tumor DNA, DNA methylation(SOX2 and PTGER4 methylation), blood protein analysis or RNA airway or nasal labeling [25].