Combinations of Toll-like receptor 8 agonist TL8-506 activate human tumor-derived dendritic cells

Abstract

BackgroundDendritic cells (DCs) are professional antigen presenting cells that initiate immune defense to pathogens and tumor cells. Human tumors contain only few DCs that mostly display a non-activated phenotype. Hence, activation of tumor-associated DCs may improve efficacy of cancer immunotherapies. Toll-like receptor (TLR) agonists and interferons are known to promote DC maturation. However, it is unclear if DCs in human tumors respond to activation signals and which stimuli induce the optimal activation of human tumor DCs.MethodsWe first screened combinations of TLR agonists, a STING agonist and interferons (IFNs) for their ability to activate human conventional DCs (cDCs). Two combinations: TL8-506 (a TLR8 agonist)+IFN-γ and TL8-506+Poly(I:C) (a TLR3 agonist) were studied in more detail. cDC1s and cDC2s derived from cord blood stem cells, blood or patient tumor samples were stimulated with either TL8-506+IFN-γ or TL8-506+Poly(I:C). Different activation markers were analyzed by ELISA, flow cytometry, NanoString nCounter Technology or single-cell RNA-sequencing. T cell activation and migration assays were performed to assess functional consequences of cDC activation.ResultsWe show that TL8-506 synergized with IFN-γ or Poly(I:C) to induce high expression of different chemokines and cytokines including interleukin (IL)-12p70 in human cord blood and blood cDC subsets in a combination-specific manner. Importantly, both combinations induced the activation of cDC subsets in patient tumor samples ex vivo. The expression of immunostimulatory genes important for anticancer responses including CD40, IFNB1, IFNL1, IL12A and IL12B were upregulated on stimulation. Furthermore, chemokines associated with CD8+ T cell recruitment were induced in tumor-derived cDCs in response to TL8-506 combinations. In vitro activation and migration assays confirmed that stimulated cDCs induce T cell activation and migration.ConclusionsOur data suggest that cord blood-derived and blood-derived cDCs are a good surrogate to study treatment responses in human tumor cDCs. While most cDCs in human tumors display a non-activated phenotype, TL8-506 combinations drive human tumor cDCs towards an immunostimulatory phenotype associated with Th1 responses on stimulation. Hence, TL8-506-based combinations may be promising candidates to initiate or boost antitumor responses in patients with cancer.

Modern Methods of Obtaining Immune Dendritic Cells With Anti-Tumor Potential

“…Як клітини-попередники ДК також використовують CD34 + гемопоетичні стовбурові клітини (ГСК), які отримують із КМ, периферичної або кордової крові [28][29][30]. Слід зазначити, що ДК, отримані з CD34 + -ГСК, стимулюють ЦТЛ більшою мірою, ніж ДК, генеровані з моноцитів периферичної крові [30].…”

“…Активація вказаних TLR призводить до підвищення секреції ІФНгамма та ІЛ-12p70 цими клітинами, а також до посилення їх міграції, активації природних кілерів і антиген-специфічних Т-клітин. Підвищення продукції ІЛ-12p70 та інших прозапальних цитокінів спостерігали також при додаванні в культуру незрілих ДК таких сполук, як TL8-506 (агоніст TLR8) у комбінації з ІФНгамма або Poly(I:C) [29]. При цьому автори спостерігали підвищення в ДК експресії генів, відповідальних за синтез молекул, що беруть участь у протипухлинній відповіді, а саме CD40, ІФН-бета1, ІЛ-12A та ІЛ-12B.…”

A Biological Perspective of TLR8 Signaling in Host Defense and Inflammation

“…12,35 Besides, chemical agonists of TLR8, called imidazoquinolines, are also available, such as R848, VTX-2337 and TL8-506. [43][44][45] From phylogenetic aspects and endosomal locations, TLR8 comprises 26 leucine-rich repeat (LRR) modules and approximately 800 amino acids in its extracellular domain, where each of them possesses a z-loop of approximately 30-40 amino acids between LRR14 and LRR15. Proteolytic processing of the z-loop in the endosome is required for association between the N terminus (residues 31-432) and C terminus (residues 458-817) of TLR8, and for dimerization of TLR8 to generate a functional, mature receptor before ligand binding (Figure 1B).…”

“…ORN-based ligands of hTLR8 have been developed, 8,35 some of which are commercially available, such as ssRNA40, a 20-mer ssRNA derived from the human immunodeficiency virus 1 (HIV-1) genome 12,35 . Besides, chemical agonists of TLR8, called imidazoquinolines, are also available, such as R848, VTX-2337 and TL8–506 43–45 …”

Nanomaterials: A powerful tool for tumor immunotherapy

“…Mature DCs act as APCs to kill tumor cells by initiating specific T cells ( 100 ). Tumor vaccines against a single antigenic target are challenging to alleviate clinically relevant symptoms in cancer patients.…”