Effects of parenteral recombinant human macrophage colony-stimulating factor on monocyte number, phenotype, and antitumor cytotoxicity in nonhuman primates

D. H. Munn, M. B. Garnick, N. K.V. Cheung

Research output: Contribution to journalArticle

77 Scopus citations


Recombinant human macrophage colony-stimulating factor (rhM-CSF) was given to cynomolgus monkeys by continuous intravenous infusion or subcutaneous injection, at a dose of 50 to 100 μg/kg/d in repetitive 14-day cycles. Starting within 24 to 48 hours of initiation of rhM-CSF, there was a progressive increase in the number of circulating monocytes, from a baseline of 811 ± 253 cells/μL to a peak of 3,495 ± 712 cells/μL on day 5 to 7. Many of these cells were large, granular, and extensively vacuolated. The expanded cell population expressed HLA-DR, LFA3, CD11b (904), and CD14 (MY4), and was 77% CD16 (FcRIII) positive by two-color cytofluorometry. In functional assays, fresh monocytes showed little cytotoxicity against cultured human melanoma cells (SKMel-1), with or without prior rhM-CSF treatment. However, after 3 days of in vitro culture in rhM-CSF, monocytes from treated animals mediated efficient antibody-dependent cytotoxicity (ADCC) against SKMel-1 using the murine monoclonal antibody 3F8 (IgG3, anti-ganglioside G(D2)). Under the same conditions, monocytes from control animals showed little ADCC (17% versus 82%, P < .05). Antitumor cytotoxicity in the absence of antibody was less efficient and was not significantly different between the two groups. There was a mild decrease in platelet count during rhM-CSF treatment, without clinical symptoms. No abnormalities of serum biochemical parameters were seen. We conclude that parenteral rhM-CSF increases the number of circulating monocytes in nonhuman primates, and that these monocytes mediate increased antitumor ADCC after a brief period of in vitro differentiation. This study has implications for the design of possible future clinical trials combining antitumor monoclonal antibodies and rhM-CSF.

Original languageEnglish (US)
Pages (from-to)2042-2048
Number of pages7
Issue number10
Publication statusPublished - Jan 1 1990
Externally publishedYes


ASJC Scopus subject areas

  • Biochemistry
  • Immunology
  • Hematology
  • Cell Biology

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