Cytostatic activity on tumour cells of monocytes from patients with gastrointestinal cancer.

The ability of monocytes from patients with gastrointestinal cancer to inhibit tumour cell growth and suppress PHA-induced lymphocyte response in vitro was assessed. Isolated monocytes, i.e., adherent Fc+ cells from mononuclear cell suspension, were cytostatic but not cytolytic for both K562 line and L1210 lymphoma cells. Monocytes from the patients showed an increased ability to inhibit the growth of L1210 but not K562 line cells. The increased cytostatic activity of monocytes was associated with their suppressor activity. This suggests that suppressor monocytes are also able to arrest tumour cell growth in vitro.