Peritoneal fluid from ovarian cancer patients stimulates MUC1 epithelial mucin expression in ovarian cancer cell lines.

The MUC1 epithelial mucin is a transmembrane glycoprotein that is frequently but variably over-expressed by adenocarcinomas. It is used as a diagnostic serum tumour marker and is a candidate target for tumour immunotherapy. Peritoneal fluid (PF) samples from ovarian cancer patients were investigated for their ability to modulate MUC1 expression in 6 ovarian cancer cell lines which showed a range from very low to high endogenous MUC1 expression. Cell lines were cultured in 20% PF for 4 days, fixed in situ and MUC1 assayed by ELISA. MUC1 expression was stimulated by some PF samples in 5 of 6 lines tested. MUC1 expression in the PE04 cell line (very low endogenous expression) was increased by 35 of 36 PFs tested (p < 0.05); stimulation varied between PFs but was greater than with 100 IU/mL hu-r-gamma-interferon. Western blotting confirmed the stimulation of MUC1 in PE04 cells and FACS showed an increase in the proportion of cells expressing MUC1. The active factor was partially purified by gel filtration and was shown to stimulate PE04 cells in a dose-dependent manner. Concentrations of IL1beta, IL4, IL6, IL8, IL10, TNF-alpha, TGF-beta and GM-CSF were often very high in PF and varied substantially between different PF samples but did not correlate with the degree of MUC1 stimulatory activity.