A Therapeutic Whole-Tumor-Cell Vaccine Covalently Conjugated with a TLR7 Agonist.

A single-protein or -peptide vaccine is not sufficient to arouse immune responses in cancer therapy. A whole-tumor-cell vaccine with complete cancer cell antigens and all conformations elicits robust immune responses and is a promising method for the treatment of advanced malignant tumors. In this study, we used 5-azacitidine to stimulate B16-F10 melanoma cells to express toll-like receptor (TLR) 3 on the cell surface and then chemically linked SZU-106, a small-molecule TLR7 agonist, to the cell surface with a pegylated linker to produce a novel whole-tumor-cell vaccine, abbreviated as Aza-BFcell-106. The vaccine stimulated mouse splenic lymphocytes and bone marrow-derived dendritic cells to secrete cytokines, promoted the maturation of dendritic cells and enhanced the capability of dendritic cells to present antigens. In a mouse model of melanoma, the vaccine effectively inhibited tumor growth, decreased tumor volume and prolonged survival. Further combination of the vaccine with a chemokine inhibitor, reparixin, significantly increased the infiltration of CD4+ and CD8+ T cells into the tumor environment, while the antitumor effect was significantly enhanced. The whole-tumor-cell vaccine Aza-BFcell-106 induced immune-activating responses in both in vitro and in vivo experiments, indicating that this vaccine has great potential to treat advanced malignant tumors.

Suppressive effects of sunitinib on a TLR activation-induced cytokine storm.

The cytokine storm includes a clinically heterogeneous set of life-threatening conditions that are manifested by extremely elevated serum cytokine levels and related symptoms (e.g., septic shock) and is devilishly mediated by Toll-like receptor (TLR) agonists in most situations. A tyrosine kinase inhibitor (TKIs), sunitinib, was screened in our group previously and showed antagonistic activity for cytokine release in a TLR7 stimulation model. In this paper, we further studied its mechanisms on interesting phenomena. In vitro, nearly all of the eleven TKIs decreased the TNF-α levels induced by the TLR7 agonist, especially sunitinib. Furthermore, sunitinib displayed potent inhibition of the cytokine levels triggered by several types of TLR ligands, including TLR3, TLR4, TLR7/8 and TLR9, in mouse spleen lymphocytes, mouse BMDCs and human PBMCs. The in vivo results showed that sunitinib efficiently depressed the LPS-induced cytokine storm, i.e., rapid and intense production of TNF-α and IL-6. Sunitinib further increased the survival time and decreased damage to mice. As for the immunosuppressive mechanisms of sunitinib, at least the PDGFR-activated ERK and p38 pathways were critical, although we could not rule out the possibility of other pathways being involved. In conclusion, our study demonstrated the inhibitory actions of TKIs on the cytokine storm induced by TLR ligands, primarily through PDGFR pathways, which could be potentially used to reduce cytokine storms in septic shock.

Anti-tumor Activity of Toll-Like Receptor 7 Agonists.

Toll-like receptors (TLRs) are a class of pattern recognition receptors that play a bridging role in innate immunity and adaptive immunity. The activated TLRs not only induce inflammatory responses, but also elicit the development of antigen specific immunity. TLR7, a member of TLR family, is an intracellular receptor expressed on the membrane of endosomes. TLR7 can be triggered not only by ssRNA during viral infections, but also by immune modifiers that share a similar structure to nucleosides. Its powerful immune stimulatory action can be potentially used in the anti-tumor therapy. This article reviewed the anti-tumor activity and mechanism of TLR7 agonists that are frequently applied in preclinical and clinical investigations, and mainly focused on small synthetic molecules, including imiquimod, resiquimod, gardiquimod, and 852A, etc.

Trichosanthin increases Granzyme B penetration into tumor cells by upregulation of CI-MPR on the cell surface.

Trichosanthin is a plant toxin belonging to the family of ribosome-inactivating proteins. It has various biological and pharmacological activities, including anti-tumor and immunoregulatory effects. In this study, we explored the potential medicinal applications of trichosanthin in cancer immunotherapy. We found that trichosanthin and cation-independent mannose-6-phosphate receptor competitively bind to the Golgi-localized, γ-ear containing and Arf-binding proteins. It in turn promotes the translocation of cation-independent mannose-6-phosphate receptor from the cytosol to the plasma membrane, which is a receptor of Granzyme B. The upregulation of this receptor on the tumor cell surface increased the cell permeability to Granzyme B, and the latter is one of the major factors of cytotoxic T lymphocyte-mediated tumor cell apoptosis. These results suggest a novel potential application of trichosanthin and shed light on its anti-tumor immunotherapy.