Abstract
Previous studies have shown that the CC chemokine receptor CCR5 is downregulated on monocyte/macrophage (MO/Mphi) surfaces in head and neck squamous cell carcinoma (HNSCC) patients (stage IIIB). Ligands (RANTES, MIP-1alpha and MIP-1beta) of this chemokine receptor were also secreted in lesser quantity from MO/Mphi of HNSCC patients in comparison with healthy individuals. In an aim to restore this dysregulated receptor-ligand signaling, we have used neem leaf glycoprotein (NLGP), a novel immunomodulator reported from our laboratory. NLGP upregulated CCR5 expression, as evidenced from studies on MO/Mphi of peripheral blood from HNSCC patients as well as healthy individuals. Expression of RANTES, MIP-1alpha and MIP-1beta was also upregulated following NLGP treatment of these cells in vitro. Interestingly, NLGP has little effect on the expression of CCR5 and the ligand RANTES in oral cancer cells. This restored CCR5 receptor-ligand signaling seen in MO/Mphi was reflected in improved CCR5-dependent, p38 mitogen-activated protein kinase (MAPK)-mediated migration of MO/Mphi after NLGP treatment to a standard chemoattractant. NLGP also induces better antigen presentation and simultaneous costimulation to effector T cells by MO/Mphi by upregulating human leucocyte antigen (HLA)-ABC, CD80 and CD86. In addition, NLGP-treated MO/Mphi-primed T cells can effectively lyse tumor cells in vitro. The effects of NLGP on monocyte migration and T cell-mediated oral tumor cell killing were further demonstrated in transwell assays with or without CCR5 neutralization. These results suggest a new approach in cancer immunotherapy by modulating dysregulated CCR5 signals from MO/Mphi.