In the early stages of lung cancer, breast cancer, pancreatic cancer, ovarian cancer, and other cancers, serum carcinoembryonic antigen (CEA), carbohydrate antigen 153(CA153), CA19-9, and CA125 levels may increase, which may also decrease after treatment, demonstrating their utility as markers of therapeutic efficacy. The gene discussed is CEACAM5; the disease is lung carcinoma.