Polyethylene glycol-conjugated HER2-targeted peptides as a nuclear imaging probe for HER2-overexpressed gastric cancer detection in vivo

Advances in Preclinical Research of Theranostic Radiopharmaceuticals in Nuclear Medicine

Theranostics of nuclear medicine refers to the combination of radionuclide imaging and internal irradiation therapy, which is currently a research hotspot and an important direction for the future development of nuclear medicine. Radiopharmaceutical is a vital component of nuclear medicine and serves as one of the fundamental pillars of molecular imaging and precision medicine. At present, a variety of radiopharmaceuticals have been developed for various targets such as fibroblast activation protein (FAP), prostate-specific membrane antigen (PSMA), somatostatin receptor 2 (SSTR2), C-X-C motif chemokine receptor 4 (CXCR4), human epidermal growth factor-2 (HER2), and integrin αvβ3, and some of them have been successfully applied in clinical practice. The radiopharmaceutical with theranostic function plays an important role in the diagnosis, treatment, efficacy evaluation, and prognosis prediction of cancers and is the key to realize the personalized treatment of tumors. This Review summarizes the preclinical research progress of theranostic radiopharmaceuticals toward the above targets in the field of nuclear medicine and discusses the prospects and development directions of radiopharmaceuticals in the future.

Generation of peptides using phage display technology for cancer diagnosis and molecular imaging

Cancer is one of the leading causes of mortality worldwide; nearly 10 million people died from it in 2020. The high mortality rate results from the lack of effective screening approaches where early detection cannot be achieved, reducing the chance of early intervention to prevent cancer development. Non-invasive and deep-tissue imaging is useful in cancer diagnosis, contributing to a visual presentation of anatomy and physiology in a rapid and safe manner. Its sensitivity and specificity can be enhanced with the application of targeting ligands with the conjugation of imaging probes. Phage display is a powerful technology to identify antibody- or peptide-based ligands with effective binding specificity against their target receptor. Tumour-targeting peptides exhibit promising results in molecular imaging, but the application is limited to animals only. Modern nanotechnology facilitates the combination of peptides with various nanoparticles due to their superior characteristics, rendering novel strategies in designing more potent imaging probes for cancer diagnosis and targeting therapy. In the end, a myriad of peptide candidates that aimed for different cancers diagnosis and imaging in various forms of research were reviewed.

ERBB2 as a prognostic biomarker correlates with immune infiltrates in papillary thyroid cancer

Epidermal growth factor receptor 2 (ERBB2) is commonly over-expressed in advanced or metastatic tissues of papillary thyroid cancer (PTC) with poor prognosis, while it remains unknown whether ERBB2 plays a role in the progression of PTC. Thus, we analyzed the data derived from online repositories, including TCGA, KEGG, GO, GeneMANIA, and STRING, to explore the relationship between ERBB2 expression and prognosis, tumor phenotypes of interest, and immune infiltrates in PTC. Compared to normal thyroid tissue, ERBB2 was up-regulated in PTC samples (p < 0.001); In comparison with the group with low expression of ERBB2, the group with high expression of ERBB2 had poorer progression-free interval in stage III/IV patients (p = 0.008) and patients aged >45 years (p = 0.019). The up-regulated ERBB2 was associated with iodine metabolism dysfunction, proliferation, metastasis, angiogenesis, and drug resistance. The expression of ERBB2 negatively correlated with enrichment scores of B cells (r = −0.176, p < 0.001), CD8⁺ T cells (r = −0.160, p < 0.001), cytotoxic cells (r = −0.219, p < 0.001), NK CD56dim cells (r = −0.218, p < 0.001), plasmacytoid dendritic cells (r = −0.267, p < 0.001), T cells (r = −0.164, p < 0.001), T follicular helper cells (r = −0.111, p = 0.012), gamma delta T cells (r = −0.105, p = 0.017), and regulatory T cells (r = −0.125, p = 0.005). In conclusion, ERBB2 may serve as a prognostic biomarker and an immunotherapeutic target in PTC, deserving further exploration.

Synthesis and comparative evaluation of 177Lu-labeled PEG and non-PEG variant peptides as HER2-targeting probes

Highest global cancer incidence of female breast cancer is a matter of great concern. HER2-positive breast cancers have high mortality rate hence detection at an early stage is vital for successful treatment, improved cancer care and survival rate. Radiolabeled peptides have emerged as new alternatives to radiolabeled antibodies to overcome the limitations of slow clearance and uptake in non-target tissues. Herein, DOTA-A9 peptide and its pegylated variant were constructed on solid phase and radiolabeled with [177Lu]LuCl3. [177Lu]DOTA-A9 and [177Lu]DOTA-PEG4-A9 displayed high binding affinity (Kd = 48.4 ± 1.4 and 55.7 ± 12.3 nM respectively) in human breast carcinoma SKBR3 cells. Two radiopeptides exhibited renal excretion and rapid clearance from normal organs. Uptake in SKBR3 tumor and tumor-to-background ratios were significantly higher (p < 0.05) for [177Lu]DOTA-PEG4-A9 at the three time points investigated. Xenografts could be clearly visualized by [177Lu]DOTA-PEG4-A9 in SPECT images at 3, 24 and 48 h p.i. indicating the potential for further exploration as HER2-targeting probe. The encouraging in vivo profile of PEG construct, [177Lu]DOTA-PEG4-A9 incentivizes future studies for clinical applications.

Review: Radionuclide Molecular Imaging Targeting HER2 in Breast Cancer with a Focus on Molecular Probes into Clinical Trials and Small Peptides

As the most frequently occurring cancer worldwide, breast cancer (BC) is the leading cause of cancer-related death in women. The overexpression of HER2 (human epidermal growth factor receptor 2) is found in about 15% of BC patients, and it is often associated with a poor prognosis due to the effect on cell proliferation, migration, invasion, and survival. As a result of the heterogeneity of BC, molecular imaging with HER2 probes can non-invasively, in real time, and quantitatively reflect the expression status of HER2 in tumors. This will provide a new approach for patients to choose treatment options and monitor treatment response. Furthermore, radionuclide molecular imaging has the potential of repetitive measurements, and it can help solve the problem of heterogeneous expression and conversion of HER2 status during disease progression or treatment. Different imaging probes of targeting proteins, such as monoclonal antibodies, antibody fragments, nanobodies, and affibodies, are currently in preclinical and clinical development. Moreover, in recent years, HER2-specific peptides have been widely developed for molecular imaging techniques for HER2-positive cancers. This article summarized different types of molecular probes targeting HER2 used in current clinical applications and the developmental trend of some HER2-specific peptides.

Isolation of Cowpea Mosaic Virus-Binding Peptides

The plant virus cowpea mosaic virus (CPMV) is a natural nanocarrier that has been developed as a platform technology for the delivery of various payloads including peptide epitopes for vaccines, contrast agents for imaging, and drugs for therapy. Genetic fusion and chemical conjugations are the mainstay approaches to load the active ingredient to the exterior and/or interior of CPMV. However, these methods have limitations; genetic engineering is limited to biologics, and chemical alteration often requires multistep reactions with modification of both CPMV and the active ingredient. Either method can also result in particle instability. Therefore, to provide an alternate path toward CPMV functionalization, we report the isolation of peptides that specifically bind to CPMV, termed CPMV-binding peptides (CBP). We used a commercial M13 phage display 7-mer peptide library to pan for and select peptides that selectively bind to CPMV. Biopanning and characterization of lead candidates resulted in isolation of the motif "GWRVSEF/L" as the CPMV-specific motif with phenylalanine (F) at the seventh position being stronger than leucine (L). Specificity to CPMV was demonstrated, and cross-reactivity toward other plant viruses was not observed. To demonstrate cargo loading, GWRVSEF was tagged with biotin, fluorescein isothiocyanate (FITC), and a human epidermal growth factor receptor 2 (HER2)-specific targeting peptide ligand. Display of the active ingredient was confirmed, and utility of tagged and targeted CPMV in cell binding assays was demonstrated. The CBP functionalization strategy offers a new avenue for CPMV nanoparticle functionalization and should offer a versatile tool to add active ingredients that otherwise may be difficult to conjugate or display.

Peptide Based Imaging Agents for HER2 Imaging in Oncology

Breast cancer continues to be the most lethal cancer type in women and one of the most diagnosed. Understanding Breast cancer receptor status is one of the most vital processes for determining treatment options. One type of breast cancer, human epidermal growth factor receptor 2 (HER2) positive, has approved receptor-based therapies including trastuzumab and pertuzumab that can significantly increase the likelihood of survival. Current methods to determine HER2 status include biopsies with immunohistochemical staining and/or fluorescence in situ hybridization. However, positron emission tomography (PET) imaging techniques using ⁸⁹Zr-trastuzumab or ⁸⁹Zr-pertuzumab are currently in clinical trials for a non-invasive, full body diagnostic approach. Although the antibodies have strong specificity to the HER2 positive lesions, challenges involving long post-injection time for imaging due to the blood circulation of the antibodies and matching of long-live isotopes leading to increased dose to the patient leave opportunities for alternative PET imaging probes. Peptides have been shown to allow for shorter injection-to-imaging time and can be used with shorter lived isotopes. HER2 specific peptides under development will help improve the diagnosis and potentially therapy options for HER2 positive breast cancer. Peptides showing specificity for HER2 could start widespread development of molecular imaging techniques for HER2 positive cancers.

PET and SPECT Imaging of the EGFR Family (RTK Class I) in Oncology

The human epidermal growth factor receptor family (EGFR-family, other designations: HER family, RTK Class I) is strongly linked to oncogenic transformation. Its members are frequently overexpressed in cancer and have become attractive targets for cancer therapy. To ensure effective patient care, potential responders to HER-targeted therapy need to be identified. Radionuclide molecular imaging can be a key asset for the detection of overexpression of EGFR-family members. It meets the need for repeatable whole-body assessment of the molecular disease profile, solving problems of heterogeneity and expression alterations over time. Tracer development is a multifactorial process. The optimal tracer design depends on the application and the particular challenges of the molecular target (target expression in tumors, endogenous expression in healthy tissue, accessibility). We have herein summarized the recent preclinical and clinical data on agents for Positron Emission Tomography (PET) and Single Photon Emission Tomography (SPECT) imaging of EGFR-family receptors in oncology. Antibody-based tracers are still extensively investigated. However, their dominance starts to be challenged by a number of tracers based on different classes of targeting proteins. Among these, engineered scaffold proteins (ESP) and single domain antibodies (sdAb) show highly encouraging results in clinical studies marking a noticeable trend towards the use of smaller sized agents for HER imaging.

Relationship between HER2 expression and tumor interstitial angiogenesis in primary gastric cancer and its effect on prognosis

INTRODUCTION

Her2-positive gastric cancer is a unique subtype of disease, requiring different diagnosis and treatment strategies and methods. Neoplasms are significantly correlated with the occurrence, invasion and metastasis of tumors. The purpose of this study was to explore the correlation between HER2 amplification and tumor interstitial angiogenesis in patients with gastric cancer.

METHODS

The data of 1121 patients with gastric cancer were retrospectively analyzed, and the amplification of HER2 was detected by immunohistochemistry (IHC) and FISH. CD34 IHC was used to label MVD. We analyzed the factors affecting HER2 amplification, the difference in MVD under different HER2 states, the factors related to 5-year survival rate of patients, and predicted the independent factors affecting 5-year survival rate of gastric cancer patients.

RESULTS

We found 115 cases with HER2 positive rate of 10.26 %. HER2 amplification was more likely in gastric cancer patients with more than 5.2 cm tumor diameter, Lauren intestinal type, tubular adenocarcinoma, and the depth of infiltration at stage T2, (P < 0.05). Gender, age, tumor location, number of lymph node metastasis, distant metastasis, clinical stage, nerve invasion and vascular tumor thrombi were not the factors affecting HER2 amplification of gastric cancer (P > 0.05). MVD count of HER2-positive gastric cancer was significantly higher than that of HER2-negative gastric cancer, (P < 0.05). The 5-year overall survival rate of 1121 patients with gastric cancer was 51.92 %. HER2 amplification, high MVD count, large tumor size, tubular adenocarcinoma, Lauren intestinal type, deep tumor infiltration, numerous lymph node metastases and late clinical stage are all associated with low 5-year survival rate, indicating poor prognosis in gastric cancer patients, (P < 0.05). The 5-year survival rate of gastric cancer patients was not correlated with gender, age, tumor location, distant metastasis, nerve invasion and vascular cancer plug, (P > 0.05). Multivariate analysis showed that Lauren classification, Infiltrating depth, Nodal status, Clinical stage, HER2 expression, MVD count were independent factors affecting the prognosis of gastric cancer patients, (P < 0.05).

CONCLUSION

HER2 overexpression was not only closely related to gastric cancer neovascularization, but also an independent predictor of prognosis of gastric cancer. In clinical treatment, anti-HER2 targeted therapy and anti-angiogenesis drugs can be adopted to achieve effective treatment.

TMTHSI, a superior 7-membered ring alkyne containing reagent for strain-promoted azide-alkyne cycloaddition reactions

We describe the development of TMTH-SulfoxImine (TMTHSI) as a superior click reagent. This reagent combines a great reactivity, with small size and low hydrophobicity and compares outstandingly with existing click reagents. TMTHSI can be conveniently functionalized with a variety of linkers allowing attachment of a diversity of small molecules and (peptide, nucleic acid) biologics.

Functional peptide-based drug delivery systems

Peptides are one of the most important functional motifs for constructing smart drug delivery systems (DDSs). Functional peptides can be conjugated with drugs or carriers via covalent bonds, or assembled into DDSs via supramolecular forces, which enables the DDSs to acquire desired functions such as targeting and/or environmental responsiveness. In this mini review, we first introduce the different types of functional peptides that are commonly used for constructing DDSs, and we highlight representative strategies for designing smart DDSs by using functional peptides in the past few years. We also state the challenges of peptide-based DDSs and come up with prospects.

Strategic design to create HER2-targeting proteins with target-binding peptides immobilized on a fibronectin type III domain scaffold

Tumor-binding peptides such as human epidermal growth factor receptor 2 (HER2)-binding peptides are attractive therapeutic and diagnostic options for cancer. However, the HER2-binding peptides (HBPs) developed thus far are susceptible to proteolysis and lose their affinity to HER2 in vivo. In this report, a method to create a HER2-binding fluctuation-regulated affinity protein (HBP-FLAP) consisting of a fibronectin type III domain (FN3) scaffold with a structurally immobilized HBP is presented. HBPs were selected by phage-library screening and grafted onto FN3 to create FN3-HBPs, and the HBP-FLAP with the highest affinity (HBP sequence: YCAHNM) was identified after affinity maturation of the grafted HBP. HBP-FLAP containing the YCAHNM peptide showed increased proteolysis-resistance, binding to HER2 with a dissociation constant (K_D) of 58 nM in ELISA and 287 nM in biolayer interferometry and specifically detects HER2-expressing cancer cells. In addition, HBP-FLAP clearly delineated HER2-expressing tumors with a half-life of 6 h after intravenous injection into tumor-bearing mice. FN3-based FLAP is an excellent platform for developing target-binding small proteins for clinical applications.

A HER2-binding protein, HBP-FLAP, developed by peptide immobilization specifically binds to HER2 and has improved resistance to proteases.

Development of the Tumor-Specific Antigen-Derived Synthetic Peptides as Potential Candidates for Targeting Breast and Other Possible Human Carcinomas

The human epidermal growth factor receptor 2 (HER2) represents one of the most studied tumor-associated antigens for cancer immunotherapy. The receptors for HER2 are overexpressed in various human cancers, such as breast and ovarian cancer. The relatively low expression of this antigen on normal tissues makes it a clinically useful molecular target for tumor imaging and targeted therapy. HER2 overexpression is correlated with aggressive tumor behavior and poor clinical outcomes. Thus, HER2 has become an important prognostic and predictive factor, as well as a potential molecular target. Due to the heterogeneity of breast cancer and possible discordance in HER2 status between primary tumors and distant metastases, assessment of HER2 expression by noninvasive imaging is important. Molecular imaging of HER2 expression may provide essential prognostic and predictive information concerning disseminated cancer and aid in the selection of an optimal therapy. Another tumor-specific antigen is MUC1, which is silent on normal tissues, but overexpressed in almost all human epithelial cell cancers, including >90% of human breast, ovarian, pancreatic, colorectal, lung, prostate, and gastric cancers and is a promising tumor antigen with diagnostic as well as the therapeutic potential of cancer. Radiolabeled small peptide ligands are attractive as probes for molecular imaging, as they reach and bind the target receptor efficiently and clear from blood and non-target organs faster than bulky antibodies. In this study, HER2 and MUC1-based peptides were synthesized and preclinically evaluated in an effort to develop peptide-based SPECT radiopharmaceuticals derived from tumor-associated antigens for the detection of breast cancer. Our findings demonstrate that the tumor antigen peptides radiolabeled efficiently with ^99mTc and showed high metabolic stability in human plasma in vitro. The data from breast tumor cell binding confirmed the high affinity (in low nanomolar range) towards respective breast cancer cell lines. In healthy mice, ^99mTc-labeled peptides displayed favorable pharmacokinetics, with high excretion by the renal system. In tumor xenografts nude mice models, good uptake by the SKBR3, MCF7, and T47D tumors were found, with good tumor-to-blood and tumor to muscle ratios. Additionally, tumor lesions can be seen in γ-camera imaging. Our data suggest that based on its ability to detect HER2- and MUC1-positive breast cancer cells in vivo, ^99mTc-HER2 and ^99mTc-MUC1-targeted peptides may be promising tumor imaging probes and warrant further investigation.