Toll-like receptor agonist therapy can profoundly augment the antitumor activity of adoptively transferred CD8+ T cells without host preconditioning

Abstract

BackgroundLymphodepletion enhances adoptive T cell transfer (ACT) therapy by activating the innate immune system via microbes released from the radiation-injured gut. Microbial components, such as LPS, are key mediators of total body irradiation (TBI) enhancement, but our ability to strategically use these toll-like receptor (TLR) agonists to bolster the potency of T cell-based therapies for cancer remains elusive. Herein, we used TLR4 agonist LPS as a tool to address how and when to use TLR agonists to effectively improve cancer immunotherapy.MethodsTo determine the mechanisms of how innate immune activation via lymphodepletion potentiated antitumor T cell immunity, we utilized the pmel-1 melanoma mouse model. B16F10-bearing mice were preconditioned with 5Gy TBI and given a tripartite ACT therapy (consisting of transferred pmel-1 CD8+ T cells, vaccination with fowlpox encoding gp100, and IL-2) along with TLR4 agonist LPS. The timing of LPS administration and the requirement of individual components of the tripartite therapy were evaluated based on tumor growth and the phenotype of recovered splenocytes by flow cytometry. We also evaluated the role of non-toxic and clinically used TLR4 and TLR9 agonists—monophosphoryl lipid A (MPL) and CpG Oligodeoxynucleotide (CpG ODN), respectively— for ACT therapy.ResultsHere we report that while exogenous administration of LPS was able to enhance adoptively transferred CD8+ T cells’ tumor destruction, LPS treatment alone did not replace individual components of the tripartite ACT regimen, or obviate TBI. Moreover, we found that sequentially administering LPS during or one day prior to ACT therapy compromised tumor regression. In contrast, administering LPS after ACT potentiated the antitumor effectiveness of the regimen, thereby supporting the expansion of transferred tumor-specific CD8+ T cells over host CD4+ T cells. We also found that non-toxic TLR agonists MPL and CpG potentiated the antitumor activity of infused CD8+ T cells. Finally, TBI was no longer needed to regress tumors in mice who were depleted of host CD4+ T cells, given a tripartite ACT regimen and then treated with low dose LPS.ConclusionsCollectively, our results identify how and when to administer TLR agonists to augment T cell-based immunotherapy in the absence or presence of host preconditioning for treatment of advanced malignancies. Our findings have clinical implications for the design of next generation immune-based therapies for patients with cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s40425-016-0110-8) contains supplementary material, which is available to authorized users.

Eradication of large established tumors in mice by combination immunotherapy that engages innate and adaptive immune responses

“…To date, complete elimination of large, poorly immunogenic tumors in immunocompetent animal models has only been reliably achieved by combination therapies employing large numbers of adoptively transferred T-cells 14,19,34 . Thus, it has remained an outstanding question whether an endogenous immune response can be stimulated to overcome advanced tumors in a majority of animals.…”

Trial Watch: Adoptively transferred cells for anticancer immunotherapy

“…Indeed, several conventional chemotherapeutic agents have immunostimulatory effects through the induction of the immunogenic cell death (ICD), which stimulates both the innate and adaptive immune systems. 9,[81][82][83][84][85][86][87] Moreover, the proliferative and/or functional capacities of adoptively transferred cells can be boosted by multiple cytokines including IL-2, IL-7 or IL-15, 16,[88][89][90][91] while their activation status and tumor homing ability can be improved with TLR agonists [92][93][94][95][96] or angiogenesis inhibitors, [97][98][99] respectively. Finally, to be fully effective, infused lymphocytes need to evolve in a permissive microenvironment.…”

Biopathological Significance of TLR9 Expression in Cancer Cells and Tumor Microenvironment Across Invasive Breast Carcinomas Subtypes

“…MDSCs are important inhibitors of T-cell responses in solid tumors. It seems that preexisting STAT3 activity in MDSCs, can skew TLR9 signaling toward supporting tumor angiogenesis while blocking antitumor immunity [48][49][50] Recently, TLR9 stimulation by CpG-ODN has been shown to activate NF-kB pathway, leading to Th1 immunostimulation and antitumor immune responses [51,52]. A promising targeted combined therapy should associate T-cell therapy and STAT3 inhibitors linked to CpG/TLR9 that could silence STAT3 in cancer cells and stromal /immune cells and favor down-regulation of cancer stem cells and antitumor immune responses [53,54].…”