Increased expression of protease-activated receptors 2 indicates poor prognosis in HBV related hepatocellular carcinoma

Protease-activated receptor 2 (PAR2)-targeting peptide derivatives for positron emission tomography (PET) imaging

The proteolytically-activated G protein-coupled receptor (GPCR) protease-activated receptor 2 (PAR2), is implicated in various cancers and inflammatory diseases. Synthetic ligands and in vitro imaging probes targeting this receptor have been developed with low nanomolar affinity, however, no in vivo imaging probes exist for PAR2. Here, we report the strategic design, synthesis, and biological evaluation of a series of novel 4-fluorobenzoylated PAR2-targeting peptides derived from 2f-LIGRLO-NH₂ (2f-LI-) and Isox-Cha-Chg-Xaa-NH₂ (Isox-) peptide families, where the 4-fluorobenzoyl moiety acts as the ¹⁹F-standard of an ¹⁸F-labeled probe for potential use in in vivo imaging. We found that several of the 4-fluorobenzoylated peptides from the 2f-LI-family exhibited PAR2 selectivity with moderate potency (EC₅₀ = 151-252 nM), whereas several from the Isox-family exhibited PAR2 selectivity with high potency (EC₅₀ = 13-42 nM). Our lead candidate, Isox-Cha-Chg-Ala-Arg-Dpr(4FB)-NH₂ (EC₅₀ = 13 nM), was successfully synthesized with fluorine-18 with a radiochemical yield of 37%, radiochemical purity of >98%, molar activity of 20 GBq/μmol, and an end of synthesis time of 125 min. Biodistribution studies and preliminary PET imaging of the tracer in mice showed predominantly renal clearance. This ¹⁸F-labeled tracer is the first reported PAR2 imaging agent with potential for use in vivo. Future work will explore the use of this tracer in cancer xenografts and inflammation models involving upregulation of PAR2 expression.

Inhibition of Protease Activated Receptor 2 Attenuates HBx-Induced Inflammation and Mitochondria Oxidative Stress

BACKGROUND

Hepatitis B virus (HBV) infection is one of the global public problems. Among the known infection cases, HBV X protein (HBx) is one of the key inducements of viral replication and host infection. This study was aimed to uncover the role of protease activated receptor 2 (PAR2) on HBx-induced liver injury.

METHODS

A PAR2-KO mouse model expressing HBx was constructed using hydrodynamics-based in vivo gene transfection method. In addition, pcDNA3.1-HBx was used to over-express HBx in LO2 cells. The effects of HBx overexpression on inflammation and mitochondria oxidative stress were evaluated.

RESULTS

We found that PAR2 protein level was increased by HBx overexpression. The enforced HBx inhibited LO2 cells apoptosis. Meanwhile, HBx induced inflammation reactions through promoting the secretion of pro-inflammatory cytokines such as TNF-α, IL-6, and CXCL-2. Overexpressed HBx also resulted in mitochondria oxidative stress by upregulation of ROS level and downregulation of MMP and ATP. However, in FSLLRY-NH2 (PAR2 antagonist) treated LO2 cells or PAR2-KO mice, PAR2 blockade reversed the above adverse effects of HBx on liver cells or tissues.

CONCLUSION

Inhibition of PAR2 may suppress inflammation and mitochondria oxidative stress caused by HBx, pointing out the potential application values of PAR2 antagonist on the treatment of HBV infection in clinic.

The Role of Protease-Activated Receptor 2 in Hepatocellular Carcinoma after Hepatectomy

Background and Objectives: Protease activated receptor-2 (PAR2) is elevated in a variety of cancers and has been promoted as a potential therapeutic target. However, the clinical and prognostic values of PAR2 in hepatocellular carcinoma (HCC) are poorly characterized. This study aimed to evaluate the expression of PAR2 in HCC tissues and examine the prognostic value of PAR2 after resection in HCC. Materials and Methods: Two hundred and eight resected specimens were collected from HCC patients at Kaohsiung Chang Gung Memorial Hospital. PAR2 protein expression was assessed by western blotting in HCC tissues and matched normal tissues. The correlation between PAR2 expression and clinicopathological parameters was analyzed. Disease-free survival (DFS) and overall survival (OS) were compared using the log-rank test. A Cox regression model was used to identify independent prognostic factors. Results: PAR2 was expressed at higher levels in HCC tissues than the paired adjacent nontumor tissues. High expression of PAR2 was associated with advanced tumor, node, metastasis (TNM )stage and histological grade. Kaplan-Meier analysis indicated high PAR2 expression was associated with poorer DFS and OS compared to low PAR2 expression. Multivariate analyses indicated high PAR2 expression [hazard ratio (HR), 1.779, p = 0.006), α-fetoprotein (AFP) (HR, 1.696, p = 0.003), liver cirrhosis (HR, 1.735, p = 0.002), and advanced TNM stage (HR, 2.061, p < 0.001) were prognostic factors for DFS, and advanced TNM stage (HR, 2.741, p < 0.001) and histological grade (HR, 2.675, p = 0.002) and high PAR2 expression (HR, 1.832, p = 0.012) were significant risk factors for OS. In subgroup analyses, the combination of PAR2 expression and serum AFP provided improved prognostic ability for OS and DFS. Conclusion: Combination PAR2 and AFP predict HCC outcomes after resection. PAR2 represents a potentially clinically relevant biomarker for HCC.