Jurkat T-Cell Antigen-Independent Elimination of PMA-Activated Neuroblastoma Cells Is Triggered by CCL2/CCR2, Depends Upon Lipid Raft LFA1/ICAM1 Immune Synapses, Is Mediated by m-TRAIL and Is Augmented by the TrkAIII Oncoprotein

Advances in multimodal therapy for high-risk neuroblastomas (NBs) have plateaued, prompting therapeutic initiatives to harness the immune system. NBs, however, are immunologically "cold" and a significant challenge to immunotherapy. Here, in a Jurkat lymphocyte cytotoxicity model, we describe an antigen-independent, cell-mediated mechanism for eliminating NB cells, first detected in PMA-activated low pcDNA-SH-SY5Y and high TrkAIII-SH-SY5Y TrkAIII-expressing cells, which are resistant to Jurkat elimination under normal conditions. Characterization of this mechanism through live cell imaging, adhesion assays, RT-PCR, Western blotting and indirect IF, employing a variety of inhibitors, indicates that it initiates with PMA-induced NB cell CCL2 expression. This results in CCL2 promotion of Jurkat CCR2b expression, CCL2/CCR2b-mediated Jurkat LFA-1 activation and the formation of cytotoxic lipid-raft LFA1/ICAM-1 immune synapses, through which Jurkat m-TRAIL combines with PMA-enhanced NB cell DR5/TRAIL-R2 expression to induce NB cell apoptosis. This mechanism is enhanced by the NB-associated oncoprotein TrkAIII through Shp/Src-regulated c-FLIP sequester and is PD-L1/PD-1-independent and resistant to osteoprotegerin. It eliminates both non-<i>MYCN</i>-amplified (SH-SY5Y and SK-N-SH) and <i>MYCN</i>-amplified (SMS-KCNR) NB cells that exhibit PMA-inducible CCL2 expression but not <i>MYCN</i>-amplified NB cells (IMR-32 and NB-1) that exhibit CCL2 repression, and is offset by reciprocal NB cell-induced Fas-mediated Jurkat cell apoptosis. These findings form a solid foundation for further pre-clinical development aimed at identifying clinically relevant physiological immune cell equivalents and alternative PKC activators, with the ultimate goal of translating this mechanism into an effective immune-therapeutic approach for the treatment of high-risk non-immunogenic NBs, especially NBs that exhibit CCL2 and TrkAIII expression.