Neutrophils are cytotoxic and growth-inhibiting for neuroblastoma cells with an anti-GD2 antibody but, without cytotoxicity, can be growth-stimulating

Abstract

Neutrophils and mononuclear cells (MNC) can mediate antibody-dependent cellular cytotoxicity (ADCC) against cancer cells. To study cytotoxicity and growth inhibition of neuroblastoma cells by neutrophils and MNC with chimeric anti-disialoganglioside (GD2) monoclonal antibody (mAb) ch14.18, we developed digital image microscopy scanning (DIMSCAN) assays that measure fluorescence of target cells in 96-well plates after 6–18 h (cytotoxicity assay) or 7 days (growth assay). Neuroblastoma cell lines (GD2-positive: SMS-KCN, SMS-LHN, LA-N-1; GD2-negative: SK-N-SH) were preloaded with calcein acetoxymethyl ester for the cytotoxicity assay or labeled in situ after 7 days of culture with fluorescein diacetate in the growth assay. Fluorescence, as quantified by DIMSCAN, was correlated with neuroblastoma cell number in both assays (100–2000 cells/well). In the cytotoxicity test, both neutrophils and MNC effectively mediated ADCC of GD2-positive but not GD2-negative neuroblastoma cell lines. Cytotoxicity of both neutrophils and MNC increased with effector to target cell (E:T) ratio (5–50:1) and mAb ch.14.18 dose (0.1–10 μg/ml). ADCC of neutrophils, but not MNC, increased with addition of GM-CSF. Neutrophils, especially with rhGM-CSF, significantly suppressed growth of GD2-positive cell lines at a high E:T ratio (50:1) and mAb dose (10 μg/ml). Without antibody, neutrophils inhibited growth of one cell line (LA-N-1) but stimulated growth of two others (SMS-KCN, SMS-LHN). If neuroblastoma cells did not express GD2 (SK-N-SH), neutrophils stimulated growth whether or not antibody was present. Neutrophil culture supernatants increased growth of SK-N-SH, LA-N-1, and SMS-KCN cells, and MNC culture supernatants increased growth of SK-N-SH. In conclusion, neutrophils can mediate cytotoxicity and growth inhibition with a chimeric anti-GD2 antibody but also can promote tumor cell growth if antibody is not present or if GD2 is not expressed.