Interactions of ficolin-3 with ovarian cancer cells.
Ficolin-3 is a pattern-recognition molecule with the ability to activate the lectin pathway of complement. It is found in lung, liver and blood, but its physiological role is unclear. We have investigated interaction of recombinant ficolin-3 with malignant cells and tissues. Cells of various lines of human origin as well as ovarian tissue sections have been studied with the use of flow cytometry and immunohistochemistry. Recombinant (but not serum-derived) ficolin-3 was found to bind strongly to the ovarian cancer cell lines, SKOV-3, OVCAR-3 and ES-2, at concentrations of 2.5 μg/ml and above. Moreover, His-tagged recombinant ficolin-3 (10 μg/ml) preferentially stained ovarian tissue sections from patients with malignant tumours compared with those from patients without. Binding to cell lines was inhibited by EDTA and specific carbohydrate ligands, indicating involvement of the fibrinogen-like domain. Binding was enhanced under mildly acidic conditions and at physiological pH after pre-incubation of cells with mildly acidic buffer. Basing on data concerning recombinant protein, it may be suggested that ficolin-3 is involved in immune response in ovarian cancer. However, unidentified serum factor(s) seem(s) to protect cancer cells from recognition by natural or rficolin-3.