CDO1 and lung cancer: Eleven lung cancer methylation-specific markers (CDO1, GSHR, HOXA11, HOXB4-1, HOXB4-2, HOXB4-3, HOXB4-4, LHX9, MIR196A1, PTGER4-1, and PTGER4-2) were selected from the previous studies [17, 24] based on their capabilities of differentiating pulmonary benign and malignant nodules on the tissue level.