CEACAM5 and colorectal carcinoma: Except for checking the H2B12Kcr levels of PBMCs in all the 40 CRC patients and 40 healthy controls, corresponding plasma were also separated from the blood samples of all these subjects, and were used to examine the carcinoembryonic antigen (CEA) commonly used as diagnostic factors for digestive tract tumors, including CEA, CA199 and CA724, using a chemiluminescence method.