ENHANCEMENT OF LUNG-COLONIZING POTENTIAL OF MURINE TUMOR-CELL LINES CO-CULTIVATED WITH ACTIVATED MACROPHAGES

In order to explore the influence of activated macrophages on tumor ce lls, we cultured a series of weakly metastatic clones isolated from th e murine T3 fibrosarcoma line (T3 clones) and the B16-F10 melanoma cel ls on feeder layers of C. parvum- or thioglycollate-elicited macrophag es, or 'resident' (unstimulated) macrophages. Go-cultivation,vith C. p arvum-elicited macrophages, but not with resident macrophages, induced an increase of the lung-colonizing potential of T3 clones and B16-F10 cells. An enhancement of lung-colonizing potential was also found in tumor cells grown in media conditioned by C. parvum-elicited macrophag es. Thioglycollate-elicited macrophages also generated a pro-clonogeni c activity which was however effective only on T3 clones but not on B1 6-F10 cells. The increase in the lung-colonizing potential of tumor ce lls stimulated by activated macrophages was retained to some degree af ter subcultivation in tissue culture medium or transplantation into sy ngeneic animals. In conclusion, our data support the notion that macro phages at different states of activation may enhance lung colonization of tumor cells by inducing a partially stable change of phenotype.