The expression of carcinoembryonic
protein (CEA) is an important
biological marker and therapeutic target in
colorectal cancer (CRC). CEA expression heterogeneity confers resistance to CEA-targeting
immunotherapy antibodies. Thus, quantification of the CEA-positive cell ratio among all
tumor cells would be important in identifying patients that would benefit from CEA-targeted
therapies. However, the proportion of
tumor cells that express CEA within primary and metastasized
tumors at different sites has not been studied. Therefore, the present study aimed to determine CEA positive cell proportion in paired CRC primary foci, liver
metastases, and lymph node (LN)
metastases, and whether proportion of CEA positive cell differs among
colorectal cancer primary foci, liver
metastases, and LN
metastases from 26 patients. The CEA expression was detected by immunohistochemical assay. Then we set up a quantification approach to quantify the proportion of CEA-positive cells based on the TissueGnostics (TG) system. Then the proportion of CEA positive cells were measured and compared among primary foci, liver
metastases, and LN
metastases. As a result, the proportion of CEA positive
tumor cells was slightly higher in liver
metastases than in primary foci (89.8% ± 2.71% vs 82.1% ± 5.05%, P < 0.001). The proportion of CEA-positive cells was significantly lower in LN
metastases than in primary foci (82.3% ± 4.32% vs 70.28% ± 5.04%, P < 0.001). In 8 cases with matched CRC primary foci, liver
metastases, and LN
metastases, the proportions of CEA proportion in liver
metastasis was the highest, followed by primary foci and LNs
metastasis. In conclusion, this study provided an new approach for quantification of CEA positive cell in
tumors and proved the percentage of CEA-positive cells varied in different
metastases.