Effects of parenteral recombinant human macrophage colony-stimulating factor on monocyte number, phenotype, and antitumor cytotoxicity in nonhuman primates.
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 micrograms/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/microL to a peak of 3,495 +/- 712 cells/microL 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 GD2). Under the same conditions, monocytes from control animals showed little ADCC (17% versus 82%, P less than .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.
Munn
D H
DH
Department of Pediatrics, Memorial Sloan-Kettering Cancer Center, New York, NY 10021.
Garnick
M B
MB
Cheung
N K
NK
D000818:Animals; D000920:Antibody-Dependent Cell Cytotoxicity / Q000187:drug effects*; D002452:Cell Count / Q000187:drug effects; D003115:Colony-Stimulating Factors / Q000494:pharmacology*; D007962:Leukocytes / Q000187:drug effects; D008252:Macaca fascicularis; D016173:Macrophage Colony-Stimulating Factor; D008297:Male; D009000:Monocytes / Q000187:drug effects*; D010641:Phenotype; D011994:Recombinant Proteins / Q000494:pharmacology*
D003115:Colony-Stimulating Factors; D011994:Recombinant Proteins; D016173:Macrophage Colony-Stimulating Factor