Guide for antibody selection and antibody application in cancer

  • An overview of several commonly used epithelial tissue and tumor markers (section two)

    1. Monoclonal mouse anti human epithelial membrane antigen (EMA)

    Epithelial membrane antigen is a macromolecular glycoprotein on the surface of epithelial cells. It is not only present in various epithelium or epithelial-derived tumors, but also be present in some non-epithelial or its derived tumors, such as plasma cells, tissue cells.

    When EMA is used to detect normal tissues, the positive expression is mainly on the cell membrane, but when the tumor is detected, the positive substance appears not only on the cell membrane, but also in the cytoplasm. In the experiment, it was found that when the tumor cells differentiated and proliferated, the positive expression was strongly positive. When the tumor cells tend to mature or mature, the positive expression is weak, and when the tumor cells are not differentiated, the antigen expression is negative.

    EMA is positive for antigen expression in detecting epithelial tissues and tumor tissues derived from them, and the antigen can also be expressed as partially positive for detecting non-epithelial-derived tumors such as plasmacytoma, synovial neoplasms, epithelioid tumors, smooth intramuscular tumors, schwannomas, and malignant in schwannomas. Therefore, it is considered that EMA is not a marker unique to epithelial-derived tumors since its specificity is not high.

    The antibody has a wide range of applications and is suitable for various types of sections. The dilution is 1:100 when tested by vacuum negative pressure LSAB.

    1. Carcinombryonic antigen (CEA)

    Since Gotel et al. isolated a tumor-associated antigen from colon cancer in 1965 and after further research, it was found that carcinoembryonic antigen was in the intestine of the fetus. In practical applications, CEA is a broad-spectrum marker. It has been proved that it is positive for antigen expression in gastric cancer, colon cancer, lung cancer, breast cancer, pancreatic cancer, cervical cancer, uterine adenocarcinoma, ovarian cancer, squamous cell carcinoma, bladder transitional epithelial cancer, esophageal cancer, etc. Positive substances were also found in the above-mentioned similar tissues and paracancerous tissues. It has been reported in the literature that CEA-labeled synovial neoplasia, mesothelioma, epithelioid tumor and meningioma can also be positive.

    Currently, CEA has two products, one is a monoclonal antibody and the other is polyclonal antibody.

    (1). Monoclonal mouse anti-human CEA, clone A5B7.

    The characteristics of this antibody are high purity, low impurity content, rarely cause non-specific staining, and at the same time, do not react with glycoprotein-containing substances. Its background is clear and clean.

    The antibody can detect the above-mentioned diseases or tissues from which they are derived. It is suitable for staining various sections. The dilution is 1:100.

    (2). Rabbit anti-human CEA.

    The antibody is a polyclonal antibody, the purity is not as good as the antibody in (1). The detection and application scope are the same as that of the antibody in (1), but the effect is weaker. The dilution is 1:300.

    1. Goat anti human alpha feloprotein (AFP)

    AFP is a type of acidic glycoprotein mainly produced by fetal liver cells and yolk cells. A small amount of it is also produced by cells of the thymus, lung, stomach, and intestine of the fetus. AFP is not a unique biomarker for liver cancer. But AFP was used as a specific diagnostic indicator for primary liver cancer at the initial stage. With the deepening of immunohistochemistry and more studies, the experimental results showed that the increase of AFP is not only seen in cases of primary hepatocellular carcinoma, but also in cases of germ cell tumors, yolk glomeroma and testicular embryonal cancer.

    Cases that showed positive after AFP detection were: primary hepatocellular carcinoma, gastric cancer, yolk tumor, and testicular embryo cancer. Its positive expression site is mainly in the cytoplasm, and a small amount is in the cell membrane and nucleus.

    The antibody is suitable for labeling of various sections and can be stained by any of immunological methods with a dilution of 1:100 to 1:300.

    The four above mentioned antibodies can be used to distinguish tumors derived from epithelium or from other sources. As long as the damage is correct and the quality of the antibody is of no problem, satisfactory results can be obtained. When using, one can select appropriate antibodies according to different tissues and different morphological structures. Of course, some tumors can never be distinguished by one or two antibodies. Therefore, it is reasonable to use antibodies according to different situations in order to make a correct diagnosis.