Circulating free and low-density lipoprotein-bound GD2 can compete in vitro with neuroblastoma cells for binding therapeutic anti-GD2 antibodies.

INTRODUCTION: GD2 is a ganglioside expressed on neuroblastoma cell membranes and shed into the circulation, where it primarily circulates bound to low-density lipoprotein (LDL). We questioned whether LDL-bound GD2 could interfere with the binding of therapeutic anti-GD2 monoclonal antibodies (like dinutuximab) to neuroblastoma cells. METHODS: The GD2-expressing neuroblastoma cell line IMR5 was stained with an anti-GD2 antibody tagged with allophycocyanin (APC) at the lowest possible saturating concentration, and mean fluorescence intensity was measured by flow cytometry after in vitro exposure to GD2-LDL or free GD2 at multiple concentrations. Control experiments assessed the ability of GD2-expressing and GD2-non-expressing cells to compete for anti-GD2-APC antibodies with IMR5 cells. RESULTS: Free and LDL-bound GD2 reduced anti-GD2-APC antibodies' binding to IMR5 cells in vitro in a concentration-dependent manner. At physiologically relevant concentrations, LDL-bound GD2 blocked antibody binding to IMR5 to a greater extent than free GD2, including at 100 nM, a concentration below median GD2 concentrations in patients with high-risk neuroblastoma. At higher concentrations, LDL-bound GD2 inhibited antibody binding to IMR5 by up to 92.6%, whereas the same concentration of free GD2 only decreased antibody binding by 56.6. CONCLUSIONS: At concentrations found in patients with high-risk neuroblastoma, both free GD2 and LDL-bound GD2 blocked anti-GD2 antibody binding to neuroblastoma cells. These data suggest that circulating GD2-LDL could impact the efficacy of therapeutic anti-GD2 antibodies administered to patients with a high disease burden during induction therapy or at relapse and may have therapeutic implications for GD2-directed adoptive cellular therapies.