Novel Toll-like Receptor 2 Ligands for Targeted Pancreatic Cancer Imaging and Immunotherapy

Abstract

Toll-like receptor 2 (TLR2) is a target for immune system stimulation during cancer immunotherapy and a cell-surface marker for pancreatic cancer. To develop targeted agents for cancer imaging and therapy, we designed, synthesized and characterized thirteen novel, fully synthetic high affinity TLR2 agonists. Analog 10 had the highest agonist activity (NF-κB functional assay, EC50=20 nM) and binding affinity (competitive binding assay, Ki=25 nM). As an immune adjuvant, compound 10 stimulated the immune system in vivo by generation and persistence of antigen-specific CD8+ T cells indicating its potential use in cancer immunotherapy. After conjugation of near-infrared dye to 10, agonist activity (EC50=34 nM) and binding affinity (Ki =11 nM) were retained in 13. Fluorescence signal was present in TLR2 expressing pancreatic tumor xenografts 24 h post-injection of 13; while an excess of unlabeled ligand blocked 13 from binding to the tumor resulting in significantly decreased signal (p<0.001) demonstrating in vivo selectivity.

Epigenetic Regulation of Toll-Like Receptor Signaling: Implications for Cancer Development

“…Pancreatic ductal adenocarcinoma is the fourth most common cause of cancer death in the United States, and has a 5-year survival rate of less than 6% [51,52]. The tumor microenvironment plays a huge role in the promotion of pancreatic cancer [51].…”

“…However, mice with inflammatory cells lacking TLR7 were exclusively protected from neoplasia, suggesting that TLR7 ligation drives cancer progression by influencing stromal inflammation [51,53]. TLR2 has been considered as a pancreatic cell surface marker as it has been shown to be expressed in over 70% of pancreatic tumors but not in normal tissue [52,54]. As such, TLR2 agonist ligands are being explored as potential targets for pancreatic cancer imaging or immune adjuvants for use in immunotherapies [52].…”

“…TLR2 has been considered as a pancreatic cell surface marker as it has been shown to be expressed in over 70% of pancreatic tumors but not in normal tissue [52,54]. As such, TLR2 agonist ligands are being explored as potential targets for pancreatic cancer imaging or immune adjuvants for use in immunotherapies [52]. TLR4 has also been implicated in pancreatic tumor progression due to the fact that TLR4 is highly expressed on leukocytes within the pancreatic tumor microenvironment, where endogenous ligands can be readily found, and engagement of TLR4 results in accelerated carcinogenesis [55].…”

Imaging of targeted lipid microbubbles to detect cancer cells using third harmonic generation microscopy

“…The specific peptide sequence was Lys-Thr-Leu-Leu-Pro-Thr-Pro-NH 2 . The synthesis of lipidated ligand was performed by solid-phase technology using a Fmoc/tBu protection strategy [17][18][19]. Fig.…”

Vaccines against Mycobacterium Tuberculosis: Exploring Alternate Strategies to Combat a Near-perfect Pathogen

“…TLR-4, 9 and 1 receptors were ineffective in inducing these pro-inflammatory cytokines that would aid in reducing the bacterial burden. New families of these agonists for TLR-2 have been recently described [130] and could be easily synthesized and linked to subunit Mtb vaccines.…”