CL264

CL264 is a a potent and highly specific toll-like receptor 7 (TLR7) ligand. Immune cells utilize toll-like receptors (TLRs) to sense pathogen associated molecular patterns (PAMPs), which represents the starting point of the innate immune response s^[1].

Using concentrations from 0.5 to 10 µg/mL, stimulation with CL264 resulted in a dose-dependent secretion of TNF-α after 6 hours. CAL-1 cells were stimulated with CL264 (5 µg/mL) for up to 12 hours.  CAL-1 cells were seeded into 96-well plates. After overnight resting, cells were stimulated with CL264 or 9.2s RNA or the combination of both. After incubation as indicated, cell supernatant was analyzed for TNF-α, IL-6, and IFN-β by ELISA. CL264 led to a robust, time-dependent release of TNF-α reaching absolute levels of 1347 pg/mL TNF-α into the supernatant^[1].Peripheral blood mononuclear cells (PBMCs) stimulated with CL264, IL-6, IL-8 and IL-12 were significantly stimulated^[2].

The TLR7 agonist CL264 ,40 μg/injectionat day 0, 3 and 6 after tumor grafting, stimulated tumor growth, and this pro-tumorigenic effect was completely lost in the absence of MDSCs, both in WT mice and in TLR7 KO mice. The tumor growth exacerbating effect of TLR7 stimulation is mediated by the increased number of MDSCs within the tumor microenvironment.The secretion of CCL2 and GM-CSF by tumor cells was confirmed in vitro, which was found increased in supernatants of CL264-stimulated cells,these results suggest that CL264 may stimulate the recruitment of MDSCs via the induction of CCL2 and GM-CSF.^[3].

References:
[1].Hilbert T, Steinhagen F, et al. Synergistic Stimulation with Different TLR7 Ligands Modulates Gene Expression Patterns in the Human Plasmacytoid Dendritic Cell Line CAL-1. Mediators Inflamm. 2015;2015:948540.
[2].Dajon M, Iribarren K, et al. Toll like receptor 7 expressed by malignant cells promotes tumor progression and metastasis through the recruitment of myeloid derived suppressor cells. Oncoimmunology. 2018 Oct 11;8(1):e1505174.