The Role of TLRs in Anti-cancer Immunity and Tumor Rejection

Abstract

In recent years, a lot of scientific interest has focused on cancer immunotherapy. Although chronic inflammation has been described as one of the hallmarks of cancer, acute inflammation can actually trigger the immune system to fight diseases, including cancer. Toll-like receptor (TLR) ligands have long been used as adjuvants for traditional vaccines and it seems they may also play a role enhancing efficiency of tumor immunotherapy. The aim of this perspective is to discuss the effects of TLR stimulation in cancer, expression of various TLRs in different types of tumors, and finally the role of TLRs in anti-cancer immunity and tumor rejection.

Keywords: anti-cancer immunity; immuno-oncology; immunotherapy; toll-like receptors; tumor rejection.

Figure 1

The role of TLR stimulation in cancer progression. TLR stimulation of cancer cells can lead to either tumor progression or inhibition. Stimulation of TLR 2, 4, and 7/8 can lead to tumor progression via production of immunosuppressive cytokines, increased cell proliferation and resistance to apoptosis. On the other hand, stimulation of TLR 2, 3, 4, 5, 7/8, and 9, often combined with chemo- or immunotherapy, can lead to tumor inhibition via different pathways. Additionally, stimulation of TLRs on NK cells and APCs (DCs and macrophages) can induce CTLs to further inhibit tumor growth.