Discovery of hPRDX5-based peptide inhibitors blocking PD-1/PD-L1 interaction through in silico proteolysis and rational design

Development of novel peptide-based radiotracers for detecting PD-L1 expression and guiding cancer immunotherapy

PURPOSE

Due to tumor heterogeneity, immunohistochemistry (IHC) showed poor accuracy in detecting the expression of programmed cell death ligand-1 (PD-L1) in patients. Positron emission tomography (PET) imaging is considered as a non-invasive technique to detect PD-L1 expression at the molecular level visually, real-timely and quantitatively. This study aimed to develop novel peptide-based radiotracers [68Ga]/[18F]AlF-NOTA-IMB for accurately detecting the PD-L1 expression and guiding the cancer immunotherapy.

METHODS

NOTA-IMB was prepared by connecting 2,2'-(7-(2-((2,5-dioxopyrrolidin-1-yl)oxy)- 2-oxoethyl)-1,4,7-triazonane-1,4-diyl) diacetic acid (NOTA-NHS) with PD-L1-targeted peptide IMB, and further radiolabeled with 68Ga or 18F-AlF. In vitro binding assay was conducted to confirm the ability of [68Ga]/[18F]AlF-NOTA-IMB to detect the expression of PD-L1. In vivo PET imaging of [68Ga]NOTA-IMB and [18F]AlF-NOTA-IMB in different tumor-bearing mice was performed, and dynamic changes of PD-L1 expression level induced by immunotherapy were monitored. Radioautography, western blotting, immunofluorescence staining and biodistribution analysis were carried out to further evaluate the specificity of radiotracers and efficacy of PD-L1 antibody immunotherapy.

RESULTS

[68Ga]NOTA-IMB and [18F]AlF-NOTA-IMB were both successfully prepared with high radiochemical yield (> 95% and > 60%, n = 5) and radiochemical purity (> 95% and > 98%, n = 5). Both tracers showed high affinity to human and murine PD-L1 with the dissociation constant (Kd) of 1.00 ± 0.16/1.09 ± 0.21 nM (A375-hPD-L1, n = 3) and 1.56 ± 0.58/1.21 ± 0.39 nM (MC38, n = 3), respectively. In vitro cell uptake assay revealed that both tracers can specifically bind to PD-L1 positive cancer cells A375-hPD-L1 and MC38 (5.45 ± 0.33/3.65 ± 0.15%AD and 5.87 ± 0.27/2.78 ± 0.08%AD at 120 min, n = 3). In vivo PET imaging and biodistribution analysis showed that the tracer [68Ga]NOTA-IMB and [18F]AlF-NOTA-IMB had high accumulation in A375-hPD-L1 and MC38 tumors, but low uptake in A375 tumor. Treatment of Atezolizumab induced dynamic changes of PD-L1 expression in MC38 tumor-bearing mice, and the tumor uptake of [68Ga]NOTA-IMB decreased from 3.30 ± 0.29%ID/mL to 1.58 ± 0.29%ID/mL (n = 3, P = 0.026) after five treatments. Similarly, the tumor uptake of [18F]AlF-NOTA-IMB decreased from 3.27 ± 0.63%ID/mL to 0.89 ± 0.18%ID/mL (n = 3, P = 0.0004) after five treatments. However, no significant difference was observed in the tumor uptake before and after PBS treatment. Biodistribution, radioautography, western blotting and immunofluorescence staining analysis further demonstrated that the expression level of PD-L1 in tumor-bearing mice treated with Atezolizumab significantly reduced about 3 times and correlated well with the PET imaging results.

CONCLUSION

[68Ga]NOTA-IMB and [18F]AlF-NOTA-IMB were successfully prepared for PET imaging the PD-L1 expression noninvasively and quantitatively. Dynamic changes of PD-L1 expression caused by immunotherapy can be sensitively detected by both tracers. Hence, the peptide-based radiotracers [68Ga]NOTA-IMB and [18F]AlF-NOTA-IMB can be applied for accurately detecting the PD-L1 expression in different tumors and monitoring the efficacy of immunotherapy.

Improving the efficacy of peptide vaccines in cancer immunotherapy

Peptide vaccines have shown great potential in cancer immunotherapy by targeting tumor antigens and activating the patient's immune system to mount a specific response against cancer cells. However, the efficacy of peptide vaccines in inducing a sustained immune response and achieving clinical benefit remains a major challenge. In this review, we discuss the current status of peptide vaccines in cancer immunotherapy and strategies to improve their efficacy. We summarize the recent advancements in the development of peptide vaccines in pre-clinical and clinical settings, including the use of novel adjuvants, neoantigens, nano-delivery systems, and combination therapies. We also highlight the importance of personalized cancer vaccines, which consider the unique genetic and immunological profiles of individual patients. We also discuss the strategies to enhance the immunogenicity of peptide vaccines such as multivalent peptides, conjugated peptides, fusion proteins, and self-assembled peptides. Although, peptide vaccines alone are weak immunogens, combining peptide vaccines with other immunotherapeutic approaches and developing novel approaches such as personalized vaccines can be promising methods to significantly enhance their efficacy and improve the clinical outcomes for cancer patients.

New insights into the roles of peroxiredoxins in cancer

Oxidative stress is one of the hallmarks of cancer. Tumorigenesis and progression are accompanied by elevated reactive oxygen species (ROS) levels and adaptive elevation of antioxidant expression levels. Peroxiredoxins (PRDXs) are among the most important antioxidants and are widely distributed in a variety of cancers. PRDXs are involved in the regulation of a variety of tumor cell phenotypes, such as invasion, migration, epithelial-mesenchymal transition (EMT) and stemness. PRDXs are also associated with tumor cell resistance to cell death, such as apoptosis and ferroptosis. In addition, PRDXs are involved in the transduction of hypoxic signals in the TME and in the regulation of the function of other cellular components of the TME, such as cancer-associated fibroblasts (CAFs), natural killer (NK) cells and macrophages. This implies that PRDXs are promising targets for cancer treatment. Of course, further studies are needed to realize the clinical application of targeting PRDXs. In this review, we highlight the role of PRDXs in cancer, summarizing the basic features of PRDXs, their association with tumorigenesis, their expression and function in cancer, and their relationship with cancer therapeutic resistance.

Immunogenic cell death inducer peptides: A new approach for cancer therapy, current status and future perspectives

Immunogenic Cell Death (ICD) is a type of cell death that kills tumor cells by stimulating the adaptive immune response against other tumor cells. ICD depends on the endoplasmic reticulum (ER) stress and the secretion of Damage-Associated Molecular Patterns (DAMP) by the dying tumor cell. DAMPs recruit innate immune cells such as Dendritic Cells (DC), triggering a cancer-specific immune response such as cytotoxic T lymphocytes (CTLs) to eliminate remaining cancer cells. ICD is accompanied by several hallmarks in dying cells, such as surface translocation of ER chaperones, calreticulin (CALR), and extracellular secretion of DAMPs such as high mobility group protein B1 (HMGB1) and adenosine triphosphate (ATP). Therapeutic peptides can kill bacteria and tumor cells thus affecting the immune system. They have high specificity and affinity for their targets, small size, appropriate cell membrane penetration, short half-life, and simple production processes. Peptides are interesting agents for immunomodulation since they may overcome the limitations of other therapeutics. Thus, the development of peptides affecting the TME and active antitumoral immunity has been actively pursued. On the other hand, several peptides have been recently identified to trigger ICD and anti-cancer responses. In the present review, we review previous studies on peptide-induced ICD, their mechanism, their targets, and markers. They include anti-microbial peptides (AMPs), cationic or mitochondrial targeting, checkpoint inhibitors, antiapoptotic inhibitors, and "don't eat me" inhibitor peptides. Also, peptides will be investigated potentially inducing ICD that is divided into ER stressors, ATPase inhibitors, and anti-microbial peptides.

Enzyme-catalyzed synthesis of selenium-doped manganese phosphate for synergistic therapy of drug-resistant colorectal cancer

BACKGROUND

The development of multidrug resistance (MDR) during postoperative chemotherapy for colorectal cancer substantially reduces therapeutic efficacy. Nanostructured drug delivery systems (NDDSs) with modifiable chemical properties are considered promising candidates as therapies for reversing MDR in colorectal cancer cells. Selenium-doped manganese phosphate (Se-MnP) nanoparticles (NPs) that can reverse drug resistance through sustained release of selenium have the potential to improve the chemotherapy effect of colorectal cancer.

RESULTS

Se-MnP NPs had an organic-inorganic hybrid composition and were assembled from smaller-scale nanoclusters. Se-MnP NPs induced excessive ROS production via Se-mediated activation of the STAT3/JNK pathway and a Fenton-like reaction due to the presence of manganese ions (Mn²⁺). Moreover, in vitro and in vivo studies demonstrated Se-MnP NPs were effective drug carriers of oxaliplatin (OX) and reversed multidrug resistance and induced caspase-mediated apoptosis in colorectal cancer cells. OX@Se-MnP NPs reversed MDR in colorectal cancer by down-regulating the expression of MDR-related ABC (ATP binding cassette) transporters proteins (e.g., ABCB1, ABCC1 and ABCG2). Finally, in vivo studies demonstrated that OX-loaded Se-MnP NPs significantly inhibited proliferation of OX-resistant HCT116 (HCT116/DR) tumor cells in nude mice.

CONCLUSIONS

OX@Se-MnP NPs with simple preparation and biomimetic chemical properties represent promising candidates for the treatment of colorectal cancer with MDR.

A Three-In-One Assembled Nanoparticle Containing Peptide-Radio-Sensitizer Conjugate and TLR7/8 Agonist Can Initiate the Cancer-Immunity Cycle to Trigger Antitumor Immune Response

Radiotherapy (RT) has been shown to cause immunogenic cell death (ICD) of cancer cells, which promote the release of tumor-associated antigens, and trigger the cancer-immunity cycle (CIC). However, ICD induced by RT usually does not occur in hypoxic tumor cells due to their resistance to radiation. Moreover, RT also induces programmed death ligand 1 (PD-L1) upregulation on tumor cells, which has an inhibitory effect on T lymphocytes. Therefore, therapy based on CIC must selectively target the restricted steps of antitumor immunity. Herein, the authors design a versatile three-in-one assembling nanoparticle that can simultaneously execute these obstacles. The amphiphilic peptide drug conjugate NIA-D1, containing the hydrophobic radio-sensitizer 2-(2-nitroimidazol-1-yl) acetic acid (NIA), a peptide substrate of matrix metalloproteinase-2, and a hydrophilic PD-L1 antagonist ^D PPA-1, is constructed and co-assembled with hydrophobic Toll-like receptor (TLR) 7/8 agonist R848 to form nanoparticle NIA-D1@R848. The NIA-D1@R848 nanoparticles combined with RT can trigger the apoptosis of tumor cells and initiate the CIC. In the presence of R848, it promotes the maturation of dendritic cells, which together with protein programmed cell death protein 1 (PD-1) and its ligand PD-L1  blockade to relieve T cell suppression, and amplify the antitumor immune cycle. In conclusion, a functionalized three-in-one nanoparticle NIA-D1@R848 is successfully constructed, which can induce strong systemic antitumor immune response.

Interfacial Peptides as Affinity Modulating Agents of Protein-Protein Interactions

The identification of disease-related protein-protein interactions (PPIs) creates objective conditions for their pharmacological modulation. The contact area (interfaces) of the vast majority of PPIs has some features, such as geometrical and biochemical complementarities, "hot spots", as well as an extremely low mutation rate that give us key knowledge to influence these PPIs. Exogenous regulation of PPIs is aimed at both inhibiting the assembly and/or destabilization of protein complexes. Often, the design of such modulators is associated with some specific problems in targeted delivery, cell penetration and proteolytic stability, as well as selective binding to cellular targets. Recent progress in interfacial peptide design has been achieved in solving all these difficulties and has provided a good efficiency in preclinical models (in vitro and in vivo). The most promising peptide-containing therapeutic formulations are under investigation in clinical trials. In this review, we update the current state-of-the-art in the field of interfacial peptides as potent modulators of a number of disease-related PPIs. Over the past years, the scientific interest has been focused on following clinically significant heterodimeric PPIs MDM2/p53, PD-1/PD-L1, HIF/HIF, NRF2/KEAP1, RbAp48/MTA1, HSP90/CDC37, BIRC5/CRM1, BIRC5/XIAP, YAP/TAZ-TEAD, TWEAK/FN14, Bcl-2/Bax, YY1/AKT, CD40/CD40L and MINT2/APP.

Peptides that immunoactivate the tumor microenvironment

Cancer immunotherapy has achieved positive clinical outcomes and is revolutionizing cancer treatment. However, cancer immunotherapy has thus far failed to improve outcomes for most "cold tumors", which are characterized by low infiltration of immune cells and immunosuppressive tumor microenvironment. Enhancing the responsiveness of cold tumors to cancer immunotherapy by stimulating the components of the tumor microenvironment is a strategy pursued in the last decade. Currently, most of the agents used to modify the tumor microenvironment are small molecules or antibodies. Small molecules exhibit low affinity and specificity towards the target and antibodies have shortcomings such as poor tissue penetration and high production cost. Peptides may overcome these drawbacks and therefore are promising materials for immunomodulating agents. Here we systematically summarize the currently developed immunoactivating peptides and discuss the potential of peptide therapeutics in cancer immunology.