ENO2 and lung cancer: To this end, researchers have made efforts all the time in seeking blood markers for early diagnosis of lung cancer, with the most intensively investigated biomarkers including squamous cell carcinoma antigen (SCC-Ag), cytokeratin 19 fragment (CYFRA 21–1), carcinoembryonic antigen (CEA), and neuron-specific enolase (NSE) (Hu et al. 2023).