Evaluation of the interaction of mononuclear phagocytes with ovarian carcinoma cells in a colony assay.

The effect of human peripheral blood monocytes on the SW626 ovarian carcinoma line was investigated in a colony assay in agar, Percoll-enriched monocytes inhibited colony formation by SW626 carcinoma cells at effector-to-target cell (E:T) ratios as low as 0.3:1. In contrast the same effectors had little cytolytic effect in a 48 h thymidine-release assay at E:T ratios as high as 40:1. Monocyte-depleted nonadherent cells had little inhibitory capacity on SW626 colony formation, whereas unseparated mononuclear cells were intermediate between Percoll-enriched monocytes and lymphoid cells. Sorting of cells positive for the monoclonal antibody marker MO2 confirmed the monocytic nature of cells which inhibited colony formation. Ovarian carcinoma cells freshly isolated from 9 patients were heterogenous in their susceptibility to colony inhibition by mononuclear phagocytes. Cells from 4 patients were not inhibited by effector cells and in one subject promotion of colony formation by mononuclear phagocytes was observed. With 4 cell preparations inhibition of colony formation was found as with the SW626 line. Colony assays may provide a useful methodological approach, particularly when effector cells mediate low levels of killing, of doubtful biological significance, in conventional isotope release assays, or when growth promotion is to be evaluated.