Toll-like receptor-5 agonist, entolimod, suppresses metastasis and induces immunity by stimulating an NK-dendritic-CD8 ⁺ T-cell axis

Abstract

Activation of an anticancer innate immune response is highly desirable because of its inherent ability to generate an adaptive antitumor T-cell response. However, insufficient safety of innate immune modulators limits clinical use to topical applications. Tolllike receptor 5 (TLR5) agonists are favorably positioned as potential systemic immunotherapeutic agents because of unusual tissue specificity of expression, uniquely safe profile of induced cytokines, and antitumor efficacy demonstrated in a number of animal models. Here, we decipher the molecular and cellular events underlying the metastasis suppressive activity of entolimod, a clinical stage TLR5 agonist that activates NF-κB-, AP-1-, and STAT3-driven immunomodulatory signaling pathways specifically within the liver. Used as a single agent in murine colon and mammary metastatic cancer models, entolimod rapidly induces CXCL9 and -10 that support homing of blood-borne CXCR3-expressing NK cells to the liver predominantly through an IFN-γ signaling independent mechanism. NK cell-dependent activation of dendritic cells is followed by stimulation of a CD8 + T-cell response, which exert both antimetastatic effect of entolimod and establishment of tumor-specific and durable immune memory. These results define systemically administered TLR5 agonists as organ-specific immunoadjuvants, enabling efficient antitumor vaccination that does not depend on identification of tumor-specific antigens.cancer immunotherapy | liver | colorectal cancer | breast cancer | innate immunity R ecent advancements in the field of anticancer immunotherapy have been primarily focused on development of T-cellbased approaches because of recognition of the inherent ability of adaptive immunity to efficiently eradicate neoplastic disease (1, 2). Innate immune responses play important roles in T-cell activation, but their potential relevance for prevention and treatment of cancer remains underappreciated (3-5). Toll-like receptors (TLRs) are gaining attention as potential therapeutic targets capable of stimulating antitumor immunity by initiating innate responses (6) and subsequent adaptive T-cell-based immunity (7). Although proof-ofprinciple for this concept has been demonstrated with agonists of several TLRs (TLR3, -7, and -9) (8), only one, the TLR7 agonist Imiquimod, has been approved for clinical use [however, this is limited to topical treatment of basal cell carcinoma (9)]. The major clinical limitations of many TLR agonists are the risk of dose-limiting toxicities associated with their systemic delivery (10-12) and metastasis stimulation (13-15). Furthermore, some previously investigated TLR agonists are restricted to injection directly into tumor tissue (3,(16)(17)(18), an approach that will likely have limited therapeutic value in cancer patients with metastatic disease.TLR5 is unique among TLRs as a potential target for systemic anticancer immunotherapy. Studies have shown that the only known natural TLR5 agonist, flagellin, flagellin-expressing Salmonella bacteria, and a pharmacolog...

Identification of Potential Therapeutic Targets Among CXC Chemokines in Breast Tumor Microenvironment Using Integrative Bioinformatics Analysis

“…The GeparSixto trial revealed that as an immune-activating factor, CXCL9 shows a positive correlation with PD-1 [43]. Brackett et al, found that the toll-like receptor-5 agonist entolimod quickly activates an innate antitumor response predominantly by attracting CXCR3+ NK cells using CXCL9 and CXCL10 [44]. Our study confirms that high transcription levels of CXCL9 confer an overall survival advantage in all BC patients and is a promising prognostic factor.…”

Role of liver ICAM-1 in metastasis

“…In order to efficiently fight against infiltrating tumor cells, either resident or recruited lymphocyte populations are required in order to mount an adequate immune response against the invading tumor. CD8 + T lymphocytes are able to control metastatic growth upon activation; however, when depleted, disease progression continues (118,119). On the other hand, CD4 + T lymphocytes also contribute to immune defense against cancer development (120).…”

Screen for Slit/Robo signaling in trunk neural cells reveals new players

“…Analogously to our microarray, they found upregulation of TLRs in NCC from both species. Toll-Like receptors have emerged as important participants in giving shape to the microenvironment of tumors by their involvement in tumorigenic pathways (Ridnour et al, 2013), to the extent that TLR5 agonists are under study as candidates for organ-specific immunotherapy to prevent metastases (Brackett et al, 2016). These findings regarding Toll receptors fit along a role for Slits in impairing proper NCC migration in our GOF experiments and open the door for future research (Giovannone et al, 2012).…”