BILIARY MUCIN SECRETED BY CULTURED HUMAN GALLBLADDER EPITHELIAL-CELLSCARRIES THE EPITOPE OF CA-19-9

Serum CA 19-9 is increased in patients with different gastrointestinal malignancies. Unfortunately, CA 19-9 is also detected in high concent rations in normal bile causing unspecific serum elevations during infl ammatory disease of the biliary tract and cholestasis. In order to ide ntify the source of CA 19-9 in bile, the capacity of cultured human ga llbladder epithelial cells (HGBEC) to secrete CA 19-9 was investigated . Cells were harvested from gallbladders removed by cholecystectomy an d cultured for up to 14 days in collagen I coated 24-well culture dish es. CA 19-9 was measured in the culture medium by a solid-phase CA 19- 9 EI4 (Boehringer). In addition culture medium was separated by Sephar ose 4B-Cl, Concanavalin-A (Con-A) and CA 19-9 affinity chromatography. Significant CA 19-9 activity was measured in the culture medium after a 24 hour incubation period. Following separation of the culture medi um by Sepharose 4B-Cl and Con-A affinity chromatography, 90 % of the C A 19-9 activity was recovered in the exclusion volume (> 2000 kDa) fro m which 90 % were identified as Con-A negative. A close con elation wa s found between CA 19-9 and concentrations of mucin purified from huma n gallbladder bile. Furthermore, CA 19-9 affinity chromatography selec tively extracted mucins from the culture medium of HCBEC. Finally, add ition of the mucin secretagogue bethanechol (6 mM) to the culture medi um increased CA 29-9 activity in the medium. In conclusion, normal HGB EC secrete mucins carrying the epitope of CA 19-9. During inflammatory biliary disease unspecific elevation of CA 19-9 in serum may reflect both inflammatory hypersecretion and leakage of biliary mucins into se rum.