Distribution of murine MUC16, a homolog of human ovarian cancer marker CA125, in adult murine reproductive tissues

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Human ovarian cancer marker CA125 is associated with greater than 80% of epithelial ovarian cancers and has been used to monitor patients with ovarian cancer. CA125 has been cloned and found encode a mucin (MUC16) of Mr >1,000 kDa with multiple tandem repeats. A murine MUC16 homolog has been identified on chromosome 9A2 encoding a protein of similar size and structure. We have examined MUC16 mRNA distribution in adult murine tissues using in situ hybridization. Strong MUC16 mRNA expression was detectable in epithelial cells of the ovarian surface, fallopian tube, oviduct and peritoneum. To characterize MUC16 protein expression in the mouse, we have developed a polyclonal antibody against a 27 kDa protein fraction of the tandem repeat domain of the murine CA125. Affinity purified antibody showed a high titer of specific activity against murine MUC16. Consistent with mRNA results, strong expression of Muc16 was detected in epithelial cells of the ovarian surface, oviduct and peritoneum, as well as the lamina propria and secretory cells of the fallopian tube. Similar to the tissue distribution of human CA125, murine MUC16 was expressed in most coelomic-epithelium-derived female reproductive tissues, including epithelial cells of ovary. Future studies will explore the functional significance of MUC 16 expression.