Simultaneous TLR2 inhibition and TLR9 activation synergistically suppress tumor metastasis in mice

Abstract

Aim: To develop a rational immunotherapy against tumor metastasis by combining a Toll-like-receptor 2 (TLR2)-neutralizing antibody with a TLR9 agonist CpG ODN, and then investigate the mechanism of action for this combinational regimen. Methods: After mouse melanoma B16-F10 cell inoculation, female C57BL/6 mice were treated with either CpG ODN (0.5 mg/kg) or the anti-TLR2 antibody (200 μg/kg), or with a combination of the two agents. Pulmonary metastases were evaluated by counting metastatic nodes on the lung surface using anatomical microscopy. Flow cytometry was used to evaluate the cytotoxicity of the immune cells in tumor-draining lymph nodes, the cell population in the spleen, and the infiltration of immune cells within the lungs. Cytokine and enzyme expression in the lung tissue was evaluated using ELISA or immunostaining. Results: Anti-metastatic effects were detected in mice treated with either CpG ODN or the anti-TLR2 antibody alone. However, treatment with CpG ODN plus the anti-TLR2 antibody synergistically suppressed the metastasis as compared with treatment with either single agent. The combinational treatment resulted in enhanced infiltration of natural killer cells and cytotoxic T cells, reduced recruitment of type 2 macrophages and Tregs, and decreased expression of immunosuppressive factors including TGF-β1, cyclooxygenase-2 and indoleamine 2,3-dioxygenase, thus stimulated tumor cytotoxicity and suppressed metastasis. The anti-metastatic effect of the combinational regimen was further confirmed in spontaneous metastatic mouse model of Lewis lung carcinoma. Conclusion: Our studies suggest that combining a TLR9 agonist with an anti-TLR2 antibody, which eliminates immunosuppressive factors from the tumor environment, is critical for an effective anti-metastatic immunotherapy.

Activation of Toll-Like Receptor 2 Promotes Proliferation of Human Lung Adenocarcinoma Cells

“…In this same study, treatment with NF-ĸB inhibitor Bay 11-7082 led to inhibition of tumor cell migration and cytokine production. Likewise, multiple studies have shown that expression and activation of TLR2 may contribute to melanoma metastasis (31,32). The direct effects of TLR2 stimulation on the lung tissue and subsequent inflammation have been explored, however few studies to date have evaluated the effects of TLR2 stimulation among different NSCLC subtypes (33).…”

Gram negative bacteria increase non‐small cell lung cancer metastasis via toll‐like receptor 4 activation and mitogen‐activated protein kinase phosphorylation

“…TLR2 heterodimerized with TLR1 or TLR6 has similar downstream signaling pathways as TLR4 . TLR2 therefore remains a potential analogue to TLR4 for infection‐driven cancer metastasis and there is some evidence supporting this concept …”

“…Severe postoperative infections can often result in bacterial sepsis leading to the release of bacterial PAMPs into the bloodstream where they can interact with circulating tumor cells (CTC) through TLRs directly. A variety of other solid tumors are also known to express functional TLRs that mediate both pro‐tumor and anti‐tumor effects on activation . Previous studies from our group have linked LPS mediated TLR4 activation to augmented adhesion in colorectal and esophageal cancer cells via different mechanisms .…”

IR-780-loaded polymeric micelles enhance the efficacy of photothermal therapy in treating breast cancer lymphatic metastasis in mice

“…Metastasis refers to the spread of cancer cells from the primary tumor into the circulatory system and colonization at distant organs [2,3,6] . During the metastatic process, lymph nodes near the primary tumor are usually the most frequent sites where cancer cells are disseminated [6][7][8][9][10] . Accordingly, inhibiting lymphatic metastasis in breast cancer is an option for treating metastatic disease.…”