Did you know? The discovery of the CA125 biomarker

Dec 28, 2018

CA125, also known as mucin 16 or MUC16 is a member of the mucin family glycoproteins. Based on early experience with immune therapy for cancer, investigators started searching for something unique on the surfaces of ovarian cancer cells that could be used to trigger recognition of tumor cells by the immune system.

After 125 attempts, an antibody was found and it was termed OC125 (for the 125th antibody tested against ovarian cancer cells) and recognized a tumor cell surface signal termed CA125.

Attempts to use this antibody in treatment were not successful, however creative researchers recognized an interesting phenomenon about the protein and antibody - the levels in the blood seemed to correlate with the status of the ovarian cancer. New studies were launched to see if CA125 might be useful as a test to diagnose and follow ovarian cancer patients.

Eventually, a CA125 level of 35 U/mL was found to be a useful cutoff point, with 99% of healthy women having values less than 35U/mL.1


  1. Foundation for womens cancer - Understanding CA125 levels (www.foundationforwomenscancer.org)