ENO2 and lung cancer: The most commonly utilized serum markers of lung cancer include squamous cell carcinoma antigen, carcino emryonic antigen (CEA), neuron-specific enolase (NSE), CA-125 [70], CYFR A 21–21 (cytokeratin fragment 21], chromogranin A, retinol-binding protein (RBP), and α1-antitrypsin.