Overproduction of PGE2 in peripheral blood monocytes of gastrointestinal cancer patients with mucins in their bloodstream.

When monocytes from healthy donors were cultured in the presence of sera from patients with gastrointestinal cancer, PGE2 production from the monocytes was elevated. Serum proteins were fractionated on Sepharose 4B and the inducing activity was found in the excluded fractions. By excluding some mucins from the serum, the inducing activity was reduced effectively. The activity was also reduced by adding binding inhibitors to the scavenger receptor. These results suggest that peripheral blood monocytes in epithelial cancer patients may be continuously stimulated by mucins in the bloodstream through the scavenger receptor, resulting in overproduction of PGE2.