Effect of macrophage-modulating agents on in vivo growth of transplantable Lewis lung cancer in mice.

C57Bl/6 mice, bearing transplantable Lewis lung cancer (non-metastatic subline) implanted either subcutaneously or intraperitoneally were treated with macrophage colony stimulating factor (M-CSF, 10(6) units per mouse, per day for 19 days), Escherichia coli lipopolysaccharide or both. Lipopolysaccharide (5 micrograms per mouse) administered daily once a day for up to 30 days impaired both subcutaneous and intraperitoneal tumor growth and prolonged survival of tumor bearing mice. Macrophage colony stimulating factor, administered daily, inhibited only subcutaneous tumor growth, both when administered alone and in combination with with lipopolysaccharide, and had no effect on intraperitoneal tumor. Moreover, it did not prolong survival of tumor bearing mice, when administered alone, and nullified the effects of lipopolysaccharide when administered concomitantly. These data suggest that macrophage colony stimulating factor, at least in this tumor model and in this dose schedule, offers little benefit. In contrast, the present data confirm earlier suggestions on therapeutic usefulness of bacterial lipopolysaccharide in neoplastic disease, which makes this compound an interesting candidate for future clinical trials.