Proteinase-activated receptor 2 promotes tumor cell proliferation and metastasis by inducing epithelial-mesenchymal transition and predicts poor prognosis in hepatocellular carcinoma

Photonanozyme-Kras-ribosome combination treatment of non-small cell lung cancer after COVID-19

With the outbreak of the coronavirus disease 2019 (COVID-19), reductions in T-cell function and exhaustion have been observed in patients post-infection of COVID-19. T cells are key mediators of anti-infection and antitumor, and their exhaustion increases the risk of compromised immune function and elevated susceptibility to cancer. Non-small cell lung cancer (NSCLC) is the most common subtype of lung cancer with high incidence and mortality. Although the survival rate after standard treatment such as surgical treatment and chemotherapy has improved, the therapeutic effect is still limited due to drug resistance, side effects, and recurrence. Recent advances in molecular biology and immunology enable the development of highly targeted therapy and immunotherapy for cancer, which has driven cancer therapies into individualized treatments and gradually entered clinicians' views for treating NSCLC. Currently, with the development of photosensitizer materials, phototherapy has been gradually applied to the treatment of NSCLC. This review provides an overview of recent advancements and limitations in different treatment strategies for NSCLC under the background of COVID-19. We discuss the latest advances in phototherapy as a promising treatment method for NSCLC. After critically examining the successes, challenges, and prospects associated with these treatment modalities, their profound prospects were portrayed.

Protease-activated receptor 2 attenuates doxorubicin-induced apoptosis in colon cancer cells

Drug resistance represents a major problem in cancer treatment. Doxorubicin (adriamycin) is an injectable DNA intercalating drug that halts cancer cell growth by inhibiting topoisomerase 2, but its long-term effectiveness is compromised by onset of resistance. This study demonstrates that expression of the PAR2 gene in human colon adenocarcinoma tissue samples was the highest among 32 different cancer types (n = 10,989), and higher in colon adenocarcinoma tissues (n = 331) than normal colon tissues (n = 308), revealing an association between PAR2 expression and human colon cancer. HT29 cells are a human colorectal adenocarcinoma cell line that is sensitive to the chemotherapeutic drug doxorubicin and also expresses PAR2. We find that PAR2 activation in HT29 cells, either by an endogenous protease agonist (trypsin) or an exogenous peptide agonist (2f-LIGRL-NH2), significantly reduces doxorubicin-induced cell death, reactive oxygen species production, caspase 3/7 activity and cleavage of caspase-8 and caspase-3. Moreover, PAR2-mediated MEK1/2-ERK1/2 pathway induced by 2f-LIGRL-NH2 leads to upregulated anti-apoptotic MCL-1 and Bcl-xL proteins that promote cellular survival. These findings suggest that activation of PAR2 compromises efficacy of doxorubicin in colon cancer. Further support for this conclusion came from experiments with human colon cancer HT29 cells, either with the PAR2 gene deleted or in the presence of a pharmacological antagonist of PAR2, which showed full restoration of all doxorubicin-mediated effects. Together, these findings reveal a strong link between PAR2 activation and signalling in human colon cancer cells and increased survival against doxorubicin-induced cell death. They support PAR2 antagonism as a possible new strategy for enhancing doxorubicin therapy.

Protease-Activated Receptor 2 (PAR2) Expressed in Sensory Neurons Contributes to Signs of Pain and Neuropathy in Paclitaxel Treated Mice

Chemotherapy-induced peripheral neuropathy (CIPN) is a common, dose-limiting side effect of cancer therapy. Protease-activated receptor 2 (PAR2) is implicated in a variety of pathologies, including CIPN. In this study, we demonstrate the role of PAR2 expressed in sensory neurons in a paclitaxel (PTX)-induced model of CIPN in mice. PAR2 knockout/wildtype (WT) mice and mice with PAR2 ablated in sensory neurons were treated with PTX administered via intraperitoneal injection. In vivo behavioral studies were done in mice using von Frey filaments and the Mouse Grimace Scale. We then examined immunohistochemical staining of dorsal root ganglion (DRG) and hind paw skin samples from CIPN mice to measure satellite cell gliosis and intra-epidermal nerve fiber (IENF) density. The pharmacological reversal of CIPN pain was tested with the PAR2 antagonist C781. Mechanical allodynia caused by PTX treatment was alleviated in PAR2 knockout mice of both sexes. In the PAR2 sensory neuronal conditional knockout (cKO) mice, both mechanical allodynia and facial grimacing were attenuated in mice of both sexes. In the DRG of the PTX-treated PAR2 cKO mice, satellite glial cell activation was reduced compared to control mice. IENF density analysis of the skin showed that the PTX-treated control mice had a reduction in nerve fiber density while the PAR2 cKO mice had a comparable skin innervation as the vehicle-treated animals. Similar results were seen with satellite cell gliosis in the DRG, where gliosis induced by PTX was absent in PAR cKO mice. Finally, C781 was able to transiently reverse established PTX-evoked mechanical allodynia. PERSPECTIVE: Our work demonstrates that PAR2 expressed in sensory neurons plays a key role in PTX-induced mechanical allodynia, spontaneous pain, and signs of neuropathy, suggesting PAR2 as a possible therapeutic target in multiple aspects of PTX CIPN.

Long non-coding RNA AC245100.4 activates the PI3K/AKT pathway to promote PCa cell proliferation by elevating PAR2

Background

Prostate cancer (PCa) is among the most generally diagnosed cancers in males. A long non-coding RNA (lncRNA) called AC245100.4 has been discovered and linked to PCa carcinogenesis. However, its specific and potential mechanism is uncertain in PCa. In this research, we investigated the role of AC245100.4 in cell proliferation and the underlying mechanism in PCa cells.

Methods

qRT-PCR assays were utilized to detect AC245100.4 expression and confirm its downstream target. The pathways related to AC245100.4 were identified by RAP-MS. PCa cell proliferation was experimented by Cell Counting Kit-8 and Colony formation assays. Western blot was performed to detect PAR2, AKT, p-AKT, Cyclin D1 and PCNA expression.

Results

AC245100.4/PAR2 overexpression promotes PCa cell proliferation and the opposite results are obtained after AC245100.4/PAR2 knockdown. Mechanistically, we found that PAR2 is confirmed as the AC245100.4 downstream target and AC245100.4 promotes PCa cell proliferation by regulating PAR2. AC245100.4 promotes PCa cell proliferation via PI3K/AKT pathway. Rescue assays validated that PAR2 knockdown reversed the impact of AC245100.4 overexpression on increasing p-AKT protein levels.

Conclusion

This research revealed that AC245100.4 enhances cell proliferation in PCa cells through modulating the PAR2/PI3K/AKT axis, which may offer novel tumor markers and potential therapeutic targets for PCa.

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.

PAR2: The Cornerstone of Pancreatic Diseases

It has been 30 years since the first member of the protease-activated receptor (PAR) family was discovered. This was followed by the discovery of three other receptors, including PAR2. PAR2 is a G protein-coupled receptor activated by trypsin site-specific proteolysis. The process starts with serine proteases acting between arginine and serine, creating an N-terminus that functions as a tethered ligand that binds, after a conformational change, to the second extracellular loop of the receptor, leading to activation of G-proteins. The physiological and pathological functions of this ubiquitous receptor are still elusive. This review focuses on PAR2 activation and its distribution under physiological and pathological conditions, with a particular focus on the pancreas, a significant producer of trypsin, which is the prototype activator of the receptor. The role in acute or chronic pancreatitis, pancreatic cancer, and diabetes mellitus will be highlighted.

PAR2 blockade reverses osimertinib resistance in non-small-cell lung cancer cells via attenuating ERK-mediated EMT and PD-L1 expression

Osimertinib, as the third-generation EGFR tyrosine kinase inhibitors (EGFR-TKIs), is a first-line molecularly targeted drug for non-small cell lung cancer (NSCLC). However, the emergence of therapeutic resistance to osimertinib markedly impairs its efficiency and efficacy, leading to the failure of clinical applications. Novel molecular targets and drugs are urgently needed for reversing osimertinib resistance in NSCLC. Protease-activated receptor 2 (PAR2) that belongs to a subfamily of G protein-coupled receptors can stimulate the transactivation of EGFR to regulate multiple cellular signalling, actively participating in tumour progression. This study firstly discovered that PAR2 expression was notably enhanced when NSCLC cells became resistant to osimertinib. A PAR2 inhibitor facilitated osimertinib to attenuate EGFR transactivation, ERK phosphorylation, EMT and PD-L1 expression which were associated to osimertinib resistance. The combination of the PAR2 inhibitor and osimertinib also notably blocked cell viability, migration, 3D sphere formation and in vivo tumour growth whereas osimertinib itself lost such inhibitory effects in osimertinib-resistant NSCLC cells. Importantly, this reversal effect of PAR2 blockade was uncovered to depend on ERK-mediated EMT and PD-L1, since inhibition of β-arrestin or ERK, which could be modulated by PAR2, sensitized osimertinib to prevent EMT, PD-L1 expression and consequently overcame osimertinib resistance. Thus, this study demonstrated that PAR2 antagonism could limit ERK-mediated EMT and immune checkpoints, consequently attenuating EGFR transactivation and reactivate osimertinib. It suggested that PAR2 may be a novel drug target for osimertinib resistance, and PAR2 inhibition may be a promising strategy candidate for reversing EGFR-TKI resistance in NSCLC.

Targeting PAR2 Overcomes Gefitinib Resistance in Non-Small-Cell Lung Cancer Cells Through Inhibition of EGFR Transactivation

Drug resistance can notably restrict clinical applications of gefitinib that is a commonly used EGFR-tyrosine kinase inhibitors (EGFR-TKIs) for non-small cell lung cancer (NSCLC). The attempts in exploring novel drug targets and reversal strategies are still needed, since gefitinib resistance has not been fully addressed. Protease-activated receptor 2 (PAR2), a G protein-coupled receptor, possesses a transactivation with EGFR to initiate a variety of intracellular signal transductions, but there is a lack of investigations on the role of PAR2 in gefitinib resistance. This study established that protease-activated receptor 2 (PAR2), actively participated in NSCLC resistant to gefitinib. PAR2 expression was significantly up-regulated when NSCLC cells or tumor tissues became gefitinib resistance. PAR2 inhibition notably enhanced gefitinib to modulate EGFR transactivation, cell viability, migration and apoptosis in gefitinib-sensitive and-resistant NSCLC cells, suggesting its reversal effects in gefitinib resistance. Meanwhile, the combination of a PAR2 inhibitor (P2pal-18S) and gefitinib largely blocked ERK phosphorylation and epithelial-mesenchymal transition (EMT) compared to gefitinib alone. Importantly, we probed its underlying mechanism and uncovered that PAR2 blockade sensitized gefitinib and reversed its resistance mainly via β-arrestin-EGFR-ERK signaling axis. These effects of PAR2 inhibition were further confirmed by the in vivo study which showed that P2pal-18S reactivated gefitinib to inhibit tumor growth via restricting ERK activation. Taken together, this study could not only reveal a new mechanism of receptor-mediated transactivation to modulate drug resistance, but also provide a novel drug target and direction for overcoming gefitinib resistance in NSCLC.

Inhibition of Bone Morphogenetic Protein 2 Suppresses the Stemness Maintenance of Cancer Stem Cells in Hepatocellular Carcinoma via the MAPK/ERK Pathway

Background

Hepatocellular carcinoma (HCC) remains a life-threatening malignant tumor. Cancer stem cells (CSCs) harbor tumor-initiating capacity and can be used as a therapeutic target for human malignancies. Bone morphogenetic proteins (BMPs) play a regulatory role in CSCs. This study investigated the role and mechanism of BMP2 in CSCs in HCC.

Methods

BMP2 expression in HCC tissues and cells, and CSCs from HepG2 cells and SMMC7721 cells (HepG2-CSCs and SMMC7721-CSCs) was measured. The association between BMP2 expression and prognosis of HCC patients was analyzed. CSCs were interfered with BMP2 to evaluate the abilities of colony and tumor sphere formation, levels of stemness-related markers, epithelial-mesenchymal transition (EMT), and invasion and migration. Levels of MAPK/ERK pathway-related proteins in HepG2-CSCs were detected after BMP2 knockdown. The effect of the activated MAPK/ERK pathway on HepG2-CSCs was assessed. Finally, the effect of BMP2 inhibition on CSCs in HCC was verified in vivo.

Results

BMP2 showed obvious upregulation in HCC tissues and cells and was further upregulated in CSCs in HCC, with its higher expression indicative of worse prognosis. Silencing BMP2 inhibited colony and tumor sphere formation, levels of stemness-related markers, as well as EMT, invasion and migration of HepG2-CSCs and SMMC7721-CSCs. The MAPK/ERK pathway was suppressed after BMP2 knockdown, and its activation reversed the inhibitory effect of shBMP2 on hepatic CSCs. BMP2 accelerated tumor growth and EMT of CSCs in HCC in vivo.

Conclusion

We concluded that BMP2 knockdown inhibited the EMT, proliferation and invasion of CSCs in HCC, thereby hindering the stemness maintenance via suppressing the MAPK/ERK pathway.

PAR2 induces ovarian cancer cell motility by merging three signalling pathways to transactivate EGFR

BACKGROUND AND PURPOSE

Specific cellular functions mediated by GPCRs are often associated with signalling through a particular G protein or β-arrestin. Here, we examine signalling through a GPCR, protease-activated receptor 2 (PAR2), in a high-grade serous ovarian cancer cell line (OV90).

EXPERIMENTAL APPROACH

Human ovarian cancer tissues (n = 1,200) and nine human ovarian cancer cell lines were assessed for PAR2 expression. PAR2 signalling mechanisms leading to cell migration and invasion were dissected using cellular assays, western blots, CRISPR-Cas9 gene knockouts, pharmacological inhibitors of PAR2 and downstream signalling proteins in OV90 cancer cells.

KEY RESULTS

PAR2 was significantly overexpressed in clinical ovarian cancer tissues and in OV90 ovarian cancer cells. PAR2 agonists, an endogenous protease (trypsin) and a synthetic peptide (2f-LIGRL-NH₂ ), induced migration and invasion of OV90 ovarian cancer cells through activating a combination of Gα_q/11 , Gα_12/13 and β-arrestin1/2, but not Gα_s or Gα_i . This novel cooperative rather than parallel signalling resulted in downstream serial activation of Src kinases, then transactivation of epidermal growth factor receptor (EGFR), followed by downstream MEK-ERK1/2-FOS/MYC/STAT3-COX2 signalling. Either a PAR2 antagonist (I-191), CRISPR-Cas9 gene knockouts (PAR2 or Gα proteins or β-arrestin1/2), or inhibitors of each downstream protein attenuated human ovarian cancer cell motility.

CONCLUSION AND IMPLICATIONS

This study highlights a novel shared signalling cascade, requiring each of Gα_q/11 , Gα_12/13 and β-arrestin1/2 for PAR2-induced ovarian cancer cell migration and invasion. This mechanism controlling a cellular function is unusual in not being linked to a specific individual G protein or β-arrestin-mediated signalling pathway.

Protease-Activated Receptor-2 Is Associated With Adverse Outcomes in Canine Mammary Carcinoma

Protease-activated receptor-2 (PAR2) is a G protein-coupled receptor that is activated by serine proteases. In humans, PAR2 is highly expressed in various cancers, including breast cancer, and is associated with cancer progression and metastasis. However, the expression and roles of PAR2 in canine mammary carcinoma remain unclear. The purpose of this study was to examine the expression of PAR2 in canine mammary carcinoma, the association between PAR2 expression and clinical characteristics, and the role of PAR2 in the metastatic phenotypes of tumor cells. Mammary carcinoma from 31 dogs and 10 normal mammary glands were included in this study, and used for immunohistochemical analysis of PAR2 expression. Normal mammary glands did not express PAR2. In contrast, mammary carcinomas showed PAR2 immunoreactivity in the cytoplasm, and its expression level varied between specimens from negative to strongly positive. The overall survival of dogs with high PAR2 expression was shorter than that of dogs with low PAR2 expression. Moreover, PAR2 expression level was associated with the presence of lymph node involvement, advanced clinical stage, and high histopathological grade. In vitro analyses revealed that a PAR2 agonist accelerated cell migration and invasion in a canine mammary carcinoma cell line. In addition, the PAR2 agonist induced epithelial-mesenchymal transition and actin polymerization. These results suggest that PAR2 expression plays a role in tumor progression and clinical outcomes in canine mammary carcinoma.

Triple-negative breast cancer-derived microvesicles transfer microRNA221 to the recipient cells and thereby promote epithelial-to-mesenchymal transition

The triple-negative phenotype is the most prevalent form of human breast cancer worldwide and is characterized by poor survival, high aggressiveness, and recurrence. Microvesicles (MV) are shredded plasma membrane components and critically mediate cell-cell communication, but can also induce cancer proliferation and metastasis. Previous studies have revealed that protease-activated receptor 2 (PAR2) contributes significantly to human triple-negative breast cancer (TNBC) progression by releasing nano-size MV and promoting cell proliferation, migration, and invasion. MV isolated from highly aggressive human TNBC cells impart metastatic potential to nonmetastatic cells. Over-expression of microRNA221 (miR221) has also been reported to enhance the metastatic potential of human TNBC, but miR221's relationship to PAR2-induced MV is unclear. Here, using isolated MV, immunoblotting, quantitative RT-PCR, FACS analysis, and enzymatic assays, we show that miR221 is translocated via human TNBC-derived MV, which upon fusion with recipient cells, enhance their proliferation, survival, and metastasis both in vitro and in vivo by inducing the epithelial-to-mesenchymal transition (EMT). Administration of anti-miR221 significantly impaired MV-induced expression of the mesenchymal markers Snail, Slug, N-cadherin, and vimentin in the recipient cells, whereas restoring expression of the epithelial marker E-cadherin. We also demonstrate that MV-associated miR221 targets phosphatase and tensin homolog (PTEN) in the recipient cells, followed by AKT Ser/Thr kinase (AKT)/NF-κB activation, which promotes EMT. Moreover, elevated miR221 levels in MV derived from human TNBC patients' blood could induce cell proliferation and metastasis in recipient cells. In summary, miR221 transfer from TNBC cells via PAR2-derived MV induces EMT and enhances the malignant potential of recipient cells.

Membrane-Anchored Serine Proteases and Protease-Activated Receptor-2-Mediated Signaling: Co-Conspirators in Cancer Progression

Pericellular proteolysis provides a significant advantage to developing tumors through the ability to remodel the extracellular matrix, promote cell invasion and migration, and facilitate angiogenesis. Recent advances demonstrate that pericellular proteases can also communicate directly to cells by activation of a unique group of transmembrane G-protein-coupled receptors (GPCR) known as protease-activated receptors (PAR). In this review, we discuss the specific roles of one of four mammalian PARs, namely PAR-2, which is overexpressed in advanced stage tumors and is activated by trypsin-like serine proteases that are highly expressed or otherwise dysregulated in many cancers. We highlight recent insights into the ability of different protease agonists to bias PAR-2 signaling and the newly emerging evidence for an interplay between PAR-2 and membrane-anchored serine proteases, which may co-conspire to promote tumor progression and metastasis. Interfering with these pathways might provide unique opportunities for the development of new mechanism-based strategies for the treatment of advanced and metastatic cancers.

Signaling Crosstalk of TGF-β/ALK5 and PAR2/PAR1: A Complex Regulatory Network Controlling Fibrosis and Cancer

Both signaling by transforming growth factor-β (TGF-β) and agonists of the G Protein-coupled receptors proteinase-activated receptor-1 (PAR1) and -2 (PAR2) have been linked to tissue fibrosis and cancer. Intriguingly, TGF-β and PAR signaling either converge on the regulation of certain matrix genes overexpressed in these pathologies or display mutual regulation of their signaling components, which is mediated in part through sphingosine kinases and sphingosine-1-phosphate and indicative of an intimate signaling crosstalk between the two pathways. In the first part of this review, we summarize the various regulatory interactions that have been discovered so far according to the organ/tissue in which they were described. In the second part, we highlight the types of signaling crosstalk between TGF-β on the one hand and PAR2/PAR1 on the other hand. Both ligand–receptor systems interact at various levels and by several mechanisms including mutual regulation of ligand–ligand, ligand–receptor, and receptor–receptor at the transcriptional, post-transcriptional, and receptor transactivation levels. These mutual interactions between PAR2/PAR1 and TGF-β signaling components eventually result in feed-forward loops/vicious cycles of matrix deposition and malignant traits that exacerbate fibrosis and oncogenesis, respectively. Given the crucial role of PAR2 and PAR1 in controlling TGF-β receptor activation, signaling, TGF-β synthesis and bioactivation, combining PAR inhibitors with TGF-β blocking agents may turn out to be more efficient than targeting TGF-β alone in alleviating unwanted TGF-β-dependent responses but retaining the beneficial ones.