The Use of Anchored Agonists of Phagocytic Receptors for Cancer Immunotherapy: B16-F10 Murine Melanoma Model

Abstract

The application of the phagocytic receptor agonists in cancer immunotherapy was studied. Agonists (laminarin, molecules with terminal mannose, N-Formyl-methioninyl-leucyl-phenylalanine) were firmly anchored to the tumor cell surface. When particular agonists of phagocytic receptors were used together with LPS (Toll-like receptor agonist), high synergy causing tumour shrinkage and a temporary or permanent disappearance was observed. Methods of anchoring phagocytic receptor agonists (charge interactions, anchoring based on hydrophobic chains, covalent bonds) and various regimes of phagocytic agonist/LPS mixture applications were tested to achieve maximum therapeutic effect. Combinations of mannan/LPS and f-MLF/LPS (hydrophobic anchors) in appropriate (pulse) regimes resulted in an 80% and 60% recovery for mice, respectively. We propose that substantial synergy between agonists of phagocytic and Toll-like receptors (TLR) is based on two events. The TLR ligand induces early and massive inflammatory infiltration of tumors. The effect of this cell infiltrate is directed towards tumor cells, bearing agonists of phagocytic receptors on their surface. The result of these processes was effective killing of tumor cells. This novel approach represents exploitation of innate immunity mechanisms for treating cancer.

Innate immunity based cancer immunotherapy: B16-F10 murine melanoma model

“…1 h prior to application of SMCC ligands. The injection of TCEP alone does not have any effect on tumor growth [4]. …”

“…The calculation of mean reduction of tumor growth was performed as previously described [4]. After therapy began, on days 4, 6, 8, 10, 12 and 14, the reduction of tumor growth was calculated using the following formula: …”

“…Analysis of cell infiltrate was performed as previously described [4]. Mice were euthanized via cervical dislocation, and the tumors were excised.…”

“…This problem was solved in our previous studies [4, 5], where we described the use of phagocytic receptors agonists anchored to the surface of tumor cells for cancer immunotherapy. To achieve a sufficiently strong therapeutic effect, it was necessary to combine this therapy with simultaneous application of lipopolysaccharide (LPS) – the agonist of TLR4.…”

“…Therefore we searched for an effective TLR agonist that would be safe for humans and shows strong synergy with phagocytosis stimulating ligands attached to tumor cells. Anchored mannan was selected for the stimulation of phagocytosis, as it gave the best results (mainly survival prolongation) in previous experiments [4, 5]. Resiquimod (R-848) proved to be the best TLR agonist demonstrating synergy with mannan anchored to tumor cells.…”