Radiation-induced CA 125 production by mesothelial cells.

CA 125 levels are often falsely elevated in disease-free endometrial cancer patients who have undergone abdominal radiation therapy. Because peritoneal irritation or mediators of inflammation can induce CA 125 production in mesothelium, the possibility that irradiated cultured mesothelial cells secrete CA 125 was investigated. Seven mesothelial cell isolates, an ovarian cell line which does not secrete CA 125, normal mammary epithelium, and normal fibroblasts were exposed to 500 cGy of 6-MV photon irradiation. Irradiated mesothelial cells showed little or no growth, while untreated cells increased in number. Twenty-four-hour CA 125 production was measured in the tissue culture medium on Day 4, and daily for one mesothelial cell isolate. Radiation stimulated CA 125 secretion in mesothelial cells up to 32 times over nonirradiated controls. The time course study showed that CA 125 levels increased rapidly in irradiated cells by Day 3 and remained elevated for the next 3 days. Increased immunoreactivity for p53 in irradiated mesothelial cells confirmed that a protein known to be radiation-inducible could be produced by the same conditions. Normal fibroblasts, mammary epithelium, and the ovarian cell line did not produce CA 125 in either the presence or absence of radiation. Thus, irradiated mesothelial cells are a potential source of serum CA 125 in patients who have received abdominal irradiation.