Mucin-16 （MUC-16）, also known as ovarian cancer associated tumor marker CA125, is a protein encoded by the MUC16 gene. MUC-16 is a member of the glycoprotein family of mucins. MUC-16 has been applied as a tumor marker or biomarker, which may be elevated in the blood of certain types of cancer patients, especially those with cancer or other benign diseases. Detecting CA-125 blood levels is considered useful for treating ovarian cancer. Although this test can provide useful information for women who are known to have cancer, due to the uncertain correlation between CA-125 levels and cancer, the CA-125 test has not been found to be useful as a screening method. In addition to ovarian cancer, CA-125 also increases in patients with endometrial cancer, fallopian tube cancer, lung cancer, breast cancer, and gastrointestinal cancer. Pregnant women may also experience this condition in their bodies. Due to the fact that serum levels can be increased under various circumstances, CA-125 is not used for cancer detection, but it is typically used to monitor ovarian cancer patients' response to chemotherapy, recurrence, and disease progression.