SOX2 and squamous cell lung carcinoma: Genetic markers such as circulating cell-free tumor DNA (cfDNA), e.g., TP53 mutations in the plasma cfDNA from SCLC (squamous cell lung cancer) cases; telomerase reverse transcription (TERT); exosomes; tumor-educated platelets (TEP); cell-free tumor RNA (cfRNA); plasma microRNAs (e.g. miR-1254 and miR-574-5p, miR-21, miRNA-126, miR-210, and miR-486-5p) in early-stage NSCLC (non-squamous cell lung cancer); circulating tumor cells (CTCs) [5, 6] and tumor-related antigens-p53, GBU4-5, NY-ESO-1, CAGE, Annexin 1, and SOX2 [7].