Application and Evaluation of [99mTc]-Labeled Peptide Nucleic Acid Targeting MicroRNA-155 in Breast Cancer Imaging

DNA-Targeted Complexes of Tc and Re for Biomedical Applications

Due to their favorable chemical features, Re and Tc complexes have been widely used for the development of new therapeutic agents and imaging probes to solve problems of biomedical relevance. This review provides an update of the most relevant research efforts towards the development of novel cancer theranostic agents using Re and Tc-based compounds interacting with specific DNA structures. This includes a variety of homometallic complexes, namely those containing M(CO)3 (M=Re, Tc) moieties, that exhibit different modes of interaction with DNA, such as covalent binding, intercalation, groove binding or G-quadruplex DNA binding. Additionally, heterometallic complexes, designed to potentiate synergistic effects of different metal centers to improve DNA-targeting, cytotoxicity and fluorescence properties, are also reviewed. Particular attention is also given to 99m Tc- and 188 Re-labeled oligonucleotides that have been widely explored to develop imaging and therapeutic radiopharmaceuticals through the in vivo hybridization with a specific complementary DNA or RNA target sequence to provide useful molecular tools in precision medicine for cancer diagnosis and treatment. Finally, the need for further improvement of DNA-targeted Re and Tc-based compounds as potential therapeutic and diagnostic agents is highlighted, and future directions are discussed.

Carrier systems of radiopharmaceuticals and the application in cancer therapy

Radiopharmaceuticals play a vital role in cancer therapy. The carrier of radiopharmaceuticals can precisely locate and guide radionuclides to the target, where radionuclides kill surrounding tumor cells. Effective application of radiopharmaceuticals depends on the selection of an appropriate carrier. Herein, different types of carriers of radiopharmaceuticals and the characteristics are briefly described. Subsequently, we review radiolabeled monoclonal antibodies (mAbs) and their derivatives, and novel strategies of radiolabeled mAbs and their derivatives in the treatment of lymphoma and colorectal cancer. Furthermore, this review outlines radiolabeled peptides, and novel strategies of radiolabeled peptides in the treatment of neuroendocrine neoplasms, prostate cancer, and gliomas. The emphasis is given to heterodimers, bicyclic peptides, and peptide-modified nanoparticles. Last, the latest developments and applications of radiolabeled nucleic acids and small molecules in cancer therapy are discussed. Thus, this review will contribute to a better understanding of the carrier of radiopharmaceuticals and the application in cancer therapy.

Monte Carlo-derived 99m Tc uptake quantification with commercial planar MBI: Tumor and breast activity concentrations

BACKGROUND

Current molecular breast imaging (MBI) images are limited to qualitative evaluation, not absolute measurement, of 99m Tc uptake in benign and malignant breast tissues.

PURPOSE

This work assesses the accuracy of previously-published and newly-proposed tumor and normal breast tissue 99m Tc uptake MBI measurements using simulations of a commercial dual-headed planar MBI system under typical clinical and acquisition protocols.

METHODS

Quantification techniques were tested in over 4000 simulated acquisitions of spherical and ellipsoid tumors with clinically relevant uptake conditions using a validated Monte Carlo application of the GE Discovery NM750b system. The evaluated techniques consisted of four tumor total activity methodologies (two single-detector-based and two geometric-mean-based), two tumor MBI volume methodologies (diameter-based and ROI-based), and two normal tissue activity concentration methodologies (single-detector-based and geometric-mean-based). The most accurate of these techniques were then used to estimate tumor activity concentrations and tumor to normal tissue relative activity concentrations (RC).

RESULTS

Single-detector techniques for tumor total activity quantification achieved mean (standard deviation) relative errors of 0.2% (4.3%) and 1.6% (4.4%) when using the near and far detector images, respectively and were more accurate and precise than the measured 8.1% (5.8%) errors of a previously published geometric-mean technique. Using these activity estimates and the true tumor volumes resulted in tumor activity concentration and RC errors within 10% of simulated values. The precision of tumor activity concentration and RC when using only MBI measurements were largely driven by the errors in estimating tumor MBI volume using planar images (± 30% inter-quartile range).

CONCLUSIONS

Planar MBI images were shown to accurately and reliably be used to estimate tumor total activities and normal tissue activity concentrations in this simulation study. However, volumetric tumor uptake measurements (i.e., absolute and relative concentrations) are limited by inaccuracies in MBI volume estimation using two-dimensional images, highlighting the need for either tomographic MBI acquisitions or anatomical volume estimates for accurate three-dimensional tumor uptake estimates.

The Role of MicroRNAs in Predicting the Neurological Outcome of Patients with Subarachnoid Hemorrhage: A Meta-analysis

Subarachnoid hemorrhage (SAH) is a hemorrhagic cerebrovascular disease with an extremely poor prognosis. The molecular mechanism and biomarkers involved in neurological outcome after SAH still need to be explored. This study assessed the microRNA expression characteristics of SAH patients with different neurological outcomes by meta-analysis. Public databases were searched from database inception until December 2022. The study reported that microRNA expression data in SAH patients with different neurological outcomes were included in the analysis. The differential expression of miRNAs was evaluated by meta-analysis. Overrepresentation analysis was performed for the targeted genes of significant miRNAs. The XGBoost algorithm was used to assess the predictive ability for neurological outcomes with clinical characteristics and significantly expressed miRNAs. Seven studies were finally included in the meta-analysis. The results showed that the levels of miR-152-3p (SMD: - 0.230; 95% CI - 0.389, - 0.070; padj = 0.041), miR-221-3p (SMD: - 0.286; 95% CI - 0.446, - 0.127; padj = 0.007), and miR-34a-5p (SMD: - 0.227; 95% CI - 0.386, - 0.067; padj = 0.041) were significantly lower in SAH patients with good neurological outcomes than in those with poor neurological outcomes. The PI3K-AKT signaling pathway may have an important role in neurological recovery after SAH. Based on the XGBoost algorithm, the neurological outcome could be accurately predicted with clinical characteristics plus the three miRNAs. The expression levels of miR-152-3p, miR-221-3p, and miR-34a-5p were significantly lower in patients with good neurological outcomes than in those with poor outcomes. These miRNAs can serve as potential predictive biomarkers for neurological outcomes. The molecular mechanism and biomarkers involved in neurological outcome after SAH still need to be explored. Our study analyzed microRNA expression characteristics of SAH patients with different neurological outcomes by meta-analysis. After analyze studies reporting the microRNA expression data in SAH patients with different neurological outcomes, results show that the levels of miR-152-3p, miR-221-3p, and miR-34a-5p were significantly lower in SAH patients with good neurological outcomes than in those with poor neurological outcomes. The PI3K-AKT signaling pathway may have an important role in neurological recovery after SAH. Based on the XGBoost algorithm, the neurological outcome could be accurately predicted with clinical characteristics plus the three miRNAs.

A novel tetrapeptide for chelator-free radiolabeling in optimized preparation of 99mTc-radiolabeled oligonucleotides

Antisense imaging uses radionuclide labeled antisense oligonucleotides to hybridize with nucleic acids in vivo, display the expression of target genes, and directly quantify biological processes at the cellular and subcellular levels. The anti-miRNA oligonucleotides (AMOs) are a series of single-stranded DNA oligonucleotides that are widely used in gene imaging and gene therapy. However, due to the negative charge and high molecular weight, the permeability through the membrane of AMOs is generally low so that most AMOs cannot enter the cells. Based on the ^99mTc-labeled AMOs imaging in previous studies, this study developed a novel tetrapeptide Glycine-Alanine-Glycine-Lysine (Gly-Ala-Gly-Lys, GAGK) for one-step labeling AMO with ^99mTc. The labeling conditions were optimized by changing the number of stannous ions, the reaction time, and the temperature, respectively. The labeled products were identified by gel electrophoresis and their serum stability was evaluated. The optimal labeling condition in this study was using 1 mg/mL SnCl₂·2H₂O and heating for 30 min at 100°C. Gel electrophoresis confirmed the verification of successful labeling of ^99mTc-GAGK-AMO. After being incubated with human fresh serum for 12 h, ^99mTc-GAGK-AMO showed good stability and no obvious degradation. Therefore, this labeling method has high labeling efficiency and stable labeling, which provides an effective method for the application of miRNA-targeted imaging.

Radiosynthesis of a novel antisense imaging probe targeting LncRNA HOTAIR in malignant glioma

Background

Long non-coding RNA (LncRNA) HOTAIR was amplified and overexpressed in many human carcinomas, which could serve as a useful target for cancer early detection and treatment. The 99mTc radiolabeled antisense oligonucleotides (ASON) could visualize the expression of HOTAIR and provide a diagnostic value for malignant tumors. The aim of this study was to evaluate whether liposome-coated antisense oligonucleotide probe 99mTc-HYNIC-ASON targeting HOTAIR can be used in in vivo imaging of HOTAIR in malignant glioma xenografts.

Methods

The ASON targeting LncRNA HOTAIR as well as mismatched ASON (ASONM) were designed and modified. The radiolabeling of 99mTc with two probes were via the conjugation of bifunctional chelator HYNIC. Then probes were purified by Sephadex G25 and tested for their radiolabeling efficiency and purity, as well as stability by ITLC (Instant thin-layer chromatography) and gel electrophoresis. Then the radiolabeled probes were transfected with lipofectamine 2000 for cellular uptake test and the next experimental use. Furthermore, biodistribution study and SPECT imaging were performed at different times after liposome-coated 99mTc-HYNIC-ASON/ASONM were intravenously injected in glioma tumor-bearing mice models. All data were analyzed by statistical software.

Results

The labeling efficiencies of 99mTc-HYNIC-ASON and 99mTc-HYNIC-ASONM measured by ITLC were (91 ± 1.5) % and (90 ± 0.6) %, respectively, and both radiochemical purities were more than 89%. Two probes showed good stability within 12 h. Gel electrophoresis confirmed that the oligomers were successfully radiolabeled no significant degradation were found. Biodistribution study demonstrated that liposome-coated antisense probes were excreted mainly through the kidney and bladder and has higher uptake in the tumor. Meanwhile, the tumor was clearly shown after injection of liposome coated 99mTc-HYNIC-ASON, and its T/M ratio was higher than that in the non-transfection group and mismatched group. No tumor was seen in mismatched and blocking group.

Conclusion

The liposome encapsulated 99mTc-HYNIC-ASON probe can be used in the in vivo, real-time imaging of LncRNA HOTAIR expression in malignant glioma.

Preclinical Imaging Evaluation of miRNAs' Delivery and Effects in Breast Cancer Mouse Models: A Systematic Review

BACKGROUND

We have conducted a systematic review focusing on the advancements in preclinical molecular imaging to study the delivery and therapeutic efficacy of miRNAs in mouse models of breast cancer.

METHODS

A systematic review of English articles published in peer-reviewed journals using PubMed, EMBASE, BIOSIS™ and Scopus was performed. Search terms included breast cancer, mouse, mice, microRNA(s) and miRNA(s).

RESULTS

From a total of 2073 records, our final data extraction was from 114 manuscripts. The most frequently used murine genetic background was Balb/C (46.7%). The most frequently used model was the IV metastatic model (46.8%), which was obtained via intravenous injection (68.9%) in the tail vein. Bioluminescence was the most used frequently used tool (64%), and was used as a surrogate for tumor growth for efficacy treatment or for the evaluation of tumorigenicity in miRNA-transfected cells (29.9%); for tracking, evaluation of engraftment and for response to therapy in metastatic models (50.6%).

CONCLUSIONS

This review provides a systematic and focused analysis of all the information available and related to the imaging protocols with which to test miRNA therapy in an in vivo mice model of breast cancer, and has the purpose of providing an important tool to suggest the best preclinical imaging protocol based on available evidence.

Radionuclide-Based Imaging of Breast Cancer: State of the Art

Simple Summary

Breast cancer is one of the most commonly diagnosed malignant tumors, possessing high incidence and mortality rates that threaten women’s health. Thus, early and effective breast cancer diagnosis is crucial for enhancing the survival rate. Radionuclide molecular imaging displays its advantages for detecting breast cancer from a functional perspective. Noninvasive visualization of biological processes with radionuclide-labeled small metabolic compounds helps elucidate the metabolic state of breast cancer, while radionuclide-labeled ligands/antibodies for receptor-targeted radionuclide molecular imaging is sensitive and specific for visualization of the overexpressed molecular markers in breast cancer. This review focuses on the most recent developments of novel radiotracers as promising tools for early breast cancer diagnosis.

Abstract

Breast cancer is a malignant tumor that can affect women worldwide and endanger their health and wellbeing. Early detection of breast cancer can significantly improve the prognosis and survival rate of patients, but with traditional anatomical imagine methods, it is difficult to detect lesions before morphological changes occur. Radionuclide-based molecular imaging based on positron emission tomography (PET) and single-photon emission computed tomography (SPECT) displays its advantages for detecting breast cancer from a functional perspective. Radionuclide labeling of small metabolic compounds can be used for imaging biological processes, while radionuclide labeling of ligands/antibodies can be used for imaging receptors. Noninvasive visualization of biological processes helps elucidate the metabolic state of breast cancer, while receptor-targeted radionuclide molecular imaging is sensitive and specific for visualization of the overexpressed molecular markers in breast cancer, contributing to early diagnosis and better management of cancer patients. The rapid development of radionuclide probes aids the diagnosis of breast cancer in various aspects. These probes target metabolism, amino acid transporters, cell proliferation, hypoxia, estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), gastrin-releasing peptide receptor (GRPR) and so on. This article provides an overview of the development of radionuclide molecular imaging techniques present in preclinical or clinical studies, which are used as tools for early breast cancer diagnosis.

Radiolabeling and Preliminary Evaluation of 99mTc-Labeled DNA Cube Nanoparticles as Potential Tracers for SPECT Imaging

Purpose

DNA nanostructures, with the advantages of structural designability and spatial addressability, have shown a great potential in the field of drug delivery and bio-medicine. Herein, we aimed to prepare technetium-99m radiolabeled DNA cube nanoparticles (^99mTc-DCN) and expect to build a DCN-based drug carrier and nuclear medicine imaging platform.

Methods

DCN could be readily assembled with 6 designed DNA oligonucleotides at an equal mole ratio in a single annealing procedure. ^99mTc-MAG3-ssDNA (A20) was obtained by labeling MAG3-ssDNA (A20) with technetium-99m by using a stannous chloride reduction method. ^99mTc-DCN was prepared by hybridize DCN with side chains (T20-DCN) with ^99mTc-MAG3-ssDNA (A20). The biodistribution study and SPECT/CT imaging were conducted on KM mice.

Results

DCN was successfully assembled, and as-prepared DCN was characterized by native polyacrylamide gel electrophoresis, atomic force microscope and fluorescence resonance energy transfer. The size of DCN was about 5 nm. The radiolabeling yield of ^99mTc-MAG3-ssDNA (A20) was approximately 90% by radio thin-layer chromatography. T20-DCN mixed with ^99mTc-MAG3-ssDNA (A20) in PBS could generate ^99mTc-DCN upon hybridization. The retention time (RT) of ^99mTc-MAG3-ssDNA (A20) was at ~22 min, and the RT of as-prepared ^99mTc-DCN was at ~12 min by radio-HPLC. The results from biodistribution study and SPECT/CT imaging showed that a significant proportion of DCNs were metabolized through the liver and kidney. Intestine exhibited a relatively indicative signal as well, which might be explained by the enterohepatic circulation of DCN via the liver and gallbladder.

Conclusion

We have successfully prepared ^99mTc-DCN as a SPECT/CT imaging probe via the side-chain hybridization strategy. The probe was metabolized mainly by the liver and excreted primarily to the bladder. Due to the superior properties of DNA cube nanoparticles, we believe DCN may potentially be translated into a preclinical setting for diagnosis and treatment of cancer-related diseases.