Definition

Carbohydrate antigen 125 (MUC16, CA125, mucin 16) is a glycoprotein synthesized by epithelial serous cells. It is a protein found on most ovarian cancer cells, is secreted into the bloodstream and can be measured. CA125 can also be found in other normal cells and cancer cells in the body.

In 1981, Bast used an ovarian serous cystadenocarcinoma cell line to produce a monoclonal antibody and discovered that CA125 is a carbohydrate-protein antigen present in the fetal coelomic epithelium. It is a glycoprotein with a molecular weight of more than 200,000, and its antigenic epitope lies in the protein part. CA-125 is a tumor marker. High levels of certain tumor markers in the blood can be a sign of cancer.

CA125 is a macromolecular polysaccharide protein, mainly present in the pericardium, peritoneum and pleura and other tissues differentiated from the fetal cavity epithelium and can also be expressed in normal female fallopian tubes, daughter endometrium and cervical epithelial cells, CA125 is mainly used for the detection of ovarian cancer, and the positive rate of epithelial ovarian cancer is high. Its elevation is also seen in cervical cancer, endometrial cancer, and fallopian tube cancer. Other non-gynecological malignancies such as pancreatic cancer, gastric cancer, lung cancer, breast cancer, colon cancer, etc. may also have elevated serum CA125.

Fig. 1 The structure of Mucin 16

Biological Properties

CA125 is an antigen recognized by a monoclonal antibody (named OC125) obtained by immunizing mice with ovarian serous cystadenocarcinoma cells and hybridizing with myeloma cells and is a transmembrane glycoprotein located in the region of chromosome 19p13.2 and containing 5797 base pairs, belonging to IgG1. Because its amino acid sequence has some characteristics of mucin molecules, it is named CA125 (gene is MUC16), and it has been confirmed that MUC16 is CA125 by transfection technology. CA125 has a relative molecular mass of 200,000～1 million, is a polymer glycoprotein, has a circular structure, contains 24% carbohydrates, is a mucin-like glycoprotein complex, and belongs to IgG. The concentration of CA125 in healthy adults is less than 35 U/mL.

Clinical Significance

Ova​rian Cancer

CA125 is mainly used in the diagnosis and course monitoring of ovarian cancer.

A common tumor marker for ovarian cancer is glycochain antigen 125 (CA125), but sensitivity is low in the early stages. Human epididymis protein 4 (HE4) is recognized as a novel diagnostic index for ovarian cancer. The combined test of HE4 and CA125 is currently the best combination to help confirm ovarian cancer.

Other Malignant Tumors

Elevated CA125 can also be seen in breast cancer, gastrointestinal cancer and other malignant tumors, with a breast cancer positive rate of 40%, pancreatic cancer positive rate of 50%, gastric cancer positive rate of 47%, lung cancer positive rate of 41.1%, colorectal cancer with a positive rate of 34.2%, another gynecological tumor positive rate of 43%.

A variety of gynecological benign diseases, such as ovarian cysts, endometrial diseases, cervicitis and uterine fibroids. CA125 may also be elevated. In the first 3 months of non-tumor pregnancy, pregnant women may have elevated CA125. CA125 is elevated in the short term, and can also be related to the menstrual cycle, with a high value in the first 10 days of menstruation, and the average value of the proliferative phase is also higher than that of the secretion period.

Fig. 2 CA125-Test

CA125 and Ovarian Cancer

The change of CA125 can be judged by drawing peripheral blood to detect the serum CA125 concentration, in ovarian cancer (epithelial) people, up to 80% of people have elevated blood CA125, and proportional to the severity of the disease, so this index in the process of epithelial ovarian cancer treatment, is an important reference index to judge the efficacy and recurrence.

If this indicator decreases faster in treatment, it indicates that surgery and chemotherapy will bring better treatment results, but this depends on an ideal surgical resection and standardized chemotherapy. If the decrease in CA125 after treatment is not satisfactory, it may indicate that tumor cells are resistant to treatment, and the doctor will arrange for further examination of imaging changes, and the treatment plan may be considered and adjusted according to the imaging results. During the follow-up period after the end of treatment, CA125 is also an important reference index for determining whether there is a recurrence. If this indicator is in the normal range for a long time, it indicates good disease control.

Up to 80% of people with epithelial ovarian cancer have elevated CA125, CA125 is elevated in 50%-60% of stage I and 75%-90% of stage III-IV, In people with radical debulking measures, postoperative CA125 typically drops to the normal reference range within one to two months, and persistent abnormalities indicate the likelihood of recurrence and death.

Alpha Lifetech Inc. is dedicated to developing CA 125 diagnostic regents. Alpha Lifetech Inc. is a reputable supplier focusing on research, manufacture and sales of In Vitro Diagnostic (IVD) regents. All the IVD regents offered by Alpha Lifetech Inc. have undergone strict QC validation and are certified by the COA (certificate of analysis). Meanwhile, we can provide customized services according to customers' requirements. Alpha Lifetech Inc. is committed to supplying high-quality, high-sensitivity antigen and antibody products for scientific research and industrial customers. In addition to regular small packages, Alpha Lifetech Inc.'s large-scale fermentation platform also allows us to provide raw material-grade IVD regents for the majority of industrial customers.

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