Cancer Antigen 125(CA125) as a Bulk Mass Marker of Peritoneal Mesothelial Cell in CAPD Patients

Kang, Duk Hee; Yoon, Kyun II

Abstract

The longevity of the peritoneum has been an object of interests and speculation since the inception of CAPD. Peritoneal mesothelial cells(MC) are the most important intraperitoneal cell quantitatively and have the capability to secret different types of substances including lubricant and various cytokines. It may therefore be essential to have information on the MC mass during peritoneal dialysis. However, there were no specific tools to evaluate the exact status of peritoneal membrane. CA125 is a 22kDa glycoprotein which is a clinically useful tumor marker of non-mucinous epithelial ovarian carcinoma. Recently, other cells including pleural and peritoneal MC have been proved to express CA125. This study was undertaken to determine whether CA125 can be used as a bulk marker of MC mass in clinically stable 23 CAPD patients. We also analyzed whether the observed intraperitoneal production of CA125 can be attributed to MC using the cultured human peritoneal MC from omentum. The CA125 production by MC in vitro was estimated with cultured MC of various number(10,000-5,000,000/well) for different period of time. The median concentration of CA125 was significantly higher in 24-hour spent dialysate than in serum(5.5 vs. 17.3U/ml, P<0.05). There was signifcant negative correlation between the dialysate CA125 level and the incidence of peritonitis. In-vitro experiment using cultured MC cell showed an exponential increase of CA125 level during confluence(6th day of culture), and persistently increased till 15 days of culture, reaching a plateau. A linear relation between the number of MC and the amount of CA125 in supernatant was also observed. In conclusion, CA125 is locally produced in the peritoneal cavity and can be an useful marker of MC mass in stable CAPD patients. Since the clinical significance of the inverse correlation between the CA125 level and peritonitis incidence is uncertain(low CA125 as a second result of repeated peritonitis or the importance of MC mass to regulate the antibacterial defense mechanism?), a prospective follow-up study is necessary to confirm the relation between dialysate CA125 and the incidence of peritonitis.