The clinical signifcance of serum level of tissue polypeptide specifc antigen (TPS) was investigated in diagnosis, response monitoring and prognosis in patients with lung cancer, compared with carcinoembryonic antigen (CEA), precursor of gastrin-releasing peptide (Pro-GRP) and cytokeratin-19-fragments (CYFRA21-1). This evidence concerns the gene CEACAM5 and lung cancer.