Toll-like receptor 7/8 agonist R848 alters the immune tumor microenvironment and enhances SBRT-induced antitumor efficacy in murine models of pancreatic cancer

Abstract

BackgroundStereotactic body radiotherapy (SBRT) has been increasingly used as adjuvant therapy in pancreatic ductal adenocarcinoma (PDAC), and induces immunogenic cell death, which leads to the release of tumor antigen and damage-associated molecular patterns. However, this induction often fails to generate sufficient response to overcome pre-existing tumor microenvironment (TME) immunosuppression. Toll-like receptor (TLR) 7/8 ligands, such as R848, can amplify the effect of tumor vaccines, with recent evidence showing its antitumor effect in pancreatic cancer by modulating the immunosuppressive TME. Therefore, we hypothesized that the combination of R848 and SBRT would improve local and systemic antitumor immune responses by potentiating the antitumor effects of SBRT and reversing the immunosuppressive nature of the PDAC TME.MethodsUsing murine models of orthotopic PDAC, we assessed the combination of intravenous TLR7/8 agonist R848 and local SBRT on tumor growth and immune response in primary pancreatic tumors. Additionally, we employed a hepatic metastatic model to investigate if the combination of SBRT targeting only the primary pancreatic tumor and systemic R848 is effective in controlling established liver metastases.ResultsWe demonstrated that intravenous administration of the TLR7/8 agonist R848, in combination with local SBRT, leads to superior tumor control compared with either treatment alone. The combination of R848 and SBRT results in significant immune activation of the pancreatic TME, including increased tumor antigen-specific CD8+ T cells, decreased regulatory T cells, and enhanced antigen-presenting cells maturation, as well as increased interferon gamma, granzyme B, and CCL5 along with decreased levels of interleukin 4 (IL-4), IL-6, and IL-10. Importantly, the combination of SBRT and systemic R848 also resulted in similar immunostimulatory changes in liver metastases, leading to improved metastatic control. CD8+ T cell depletion studies highlighted the necessity of these effector cells at both the local and hepatic metastatic sites. T cell receptor (TCR) clonotype analysis indicated that systemic R848 not only diversified the TCR repertoire but also conditioned the metastatic foci to facilitate entry of CD8+ T cells generated by SBRT therapy.ConclusionsThese findings suggest that systemic administration of TLR7/8 agonists in combination with SBRT may be a promising avenue for metastatic PDAC treatment.

Robinin inhibits pancreatic cancer cell proliferation, EMT and inflammation via regulating TLR2-PI3k-AKT signaling pathway

“…In pancreatic cancer, TLR2 and TLR4 were found mainly over-expression and correlated with more mortality [10], while TLR9 was found low express in pancreatic cancer [11]. Other molecules of the TLR family (TLR3,7,8) were also con rmed to be closely related to occurrence, development and invasion of pancreatic cancer [12,13]. Therefore, we speculated that TLR2 interference can similarly regulate tumor microenvironment so as to minimize pancancer cell growth and attenuate metastasis, which would be a good candidate of pancreatic cancer medical therapy.…”

CD73 and PD-L1 dual blockade amplifies antitumor efficacy of SBRT in murine PDAC models

“…As previously described, 17 tumor tissue samples were homogenized and digested with Lysis Buffer #11 (R&D Systems) containing protease inhibitors on ice for 1 hour. The samples were then centrifuged at 14,000 rpm for 20 min at 4 o C, and supernatants were collected and then delivered to Eve Technologies Corporation (Calgary, AB.…”

The clinical terrain of immunotherapies in heterogeneous pancreatic cancer: unravelling challenges and opportunities

“…In a predefined group of patients with high metastatic burden, the IMM‐101/gemcitabine combination significantly prolonged mOS from 4.4 to 7.0 months [61]. Similarly, in another study, the TLR7/8 agonist R848 showed the potential opportunity to target metastatic PDAC by combining with stereotactic body radiotherapy [62]. This response to a TLR agonist may be associated with modulation of the immunosuppressive microenvironment by increasing cytotoxic CD8 + T‐cells in the metastatic microenvironment and improving therapeutic outcomes [62].…”

“…Similarly, in another study, the TLR7/8 agonist R848 showed the potential opportunity to target metastatic PDAC by combining with stereotactic body radiotherapy [62]. This response to a TLR agonist may be associated with modulation of the immunosuppressive microenvironment by increasing cytotoxic CD8 + T‐cells in the metastatic microenvironment and improving therapeutic outcomes [62]. This suggests combination TLR agonists may be useful in downstaging late‐stage/metastatic PDACs, potentially in preparation for surgical resection.…”

“…M Herpels et al T-cells in the metastatic microenvironment and improving therapeutic outcomes [62]. This suggests combination TLR agonists may be useful in downstaging late-stage/metastatic PDACs, potentially in preparation for surgical resection.…”