Effects of granulocyte‐monocyte colony‐stimulating factor (GM‐CSF) on expression of adhesion molecules and production of cytokines in blood monocytes and ovarian cancer‐associated macrophages

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Abstract
The present study was aimed at characterizing the effects of in vitro exposure to GM‐CSF on blood monocytes and tumor‐associated macrophages (TAM) in human ovarian cancer. Purified populations of TAM from ovarian cancer patients were studied in terms of expression of surface molecules, cytokine production and tumor cytotoxicity after overnight incubation with GM‐CSF or IFNγ and LPS, used as reference activators. GM‐CSF augmented the surface expression of ICAM‐I and CD 18 in TAM and in blood monocytes. Stimulation was more prominent in monocytes than in TAM, which showed higher baseline expression of this adhesion molecule. ICAM‐3 was not influenced by GM‐CSF or by IFNγ/LPS. GM‐CSF‐augmented ICAM‐I expression was associated with higher levels of mRNA transcripts. The protein synthesis inhibitor cycloheximide superinduced basal and GM‐CSF‐induced ICAM‐I transcripts, thus excluding a role for secondary polypeptide mediators. In the absence of stimuli, TAM produced higher levels, compared to monocytes, of IL‐6 and IL‐8 but not of IL‐1 and TNF. GM‐CSF augmented the production of IL‐6 and IL‐8 (but not that of IL‐1 and TNF) in TAM, whereas it had little effect on blood monocyte. Tumoricidal activity was tested against two ovarian tumor cell lines (OVCAR3 and SW626). GM‐CSF more prominently augmented monocyte cytotoxicity, while only 2 of 6 TAM preparations were stimulated by GM‐CSF. These results suggest that GM‐CSF selectively regulates the function of blood monocytes and TAM, the effect of this cytokine varying with the parameter and cell population examined. These data provide a rational and biological endpoint for further studies with GM‐CSF as an activator of mononuclear phagocyte function in ovarian cancer.