Noninvasive Evaluation of Tumoral PD-L1 Using a Novel 99mTc-Labeled Nanobody Tracer with Rapid Renal Clearance.

The expression level of PD-L1 in tumor tissue is considered one of the effective biomarkers to guide PD-1/PD-L1 therapy. Quantifying whole-body PD-L1 expression by SPECT imaging may help in selecting patients that potentially respond to PD-1/PD-L1 therapy. Nanobody is the smallest antibody fragment with antigen-binding ability that is well suited for radionuclide imaging. Nevertheless, high retention of radioactivity in the kidney may limit its clinical translation. The present study aimed to screen, design, and prepare a nanobody-based SPECT probe with rapid renal clearance to evaluate the PD-L1 expression level in vivo noninvasively. A phage library was constructed by immunizing alpaca with recombinant human PD-L1 protein, and 17 anti-PD-L1 nanobodies were screened by the phage display technique. After sequence alignment and flow cytometry analysis, APN09 was selected as the candidate nanobody, and a GGGC chelator was attached to its C-terminus for 99mTc labeling to prepare a SPECT imaging probe. The affinity and specificity of 99mTc-APN09 were evaluated by protein and cell-binding experiments, and SPECT imaging and biodistribution were performed in a mouse model with bilateral transplantation of A549 and A549PD-L1 tumors. The ability of 99mTc-APN09 to quantify the PD-L1 expression level in vivo was validated in tumor models with different PD-L1 expression levels. 99mTc-APN09 had a radiochemical purity higher than 99% and a binding equilibrium dissociation constant of 21.44 ± 1.65 nM with hPD-L1, showing high affinity. SPECT imaging results showed that 99mTc-APN09 could efficiently detect PD-L1-positive tumors within 0.5 h, and the quantitative results of SPECT were well correlated with the expression level of PD-L1 in cell lines. SPECT imaging and biodistribution results also showed that 99mTc-APN09 was rapidly cleared from the kidney in 2 h postinjection. 99mTc-APN09 was a simple and stable tool for visualizing PD-L1 expression in the whole body. In addition, due to its significant reduction in renal retention, it has better prospects for clinical translation.

Preclinical evaluation and pilot clinical study of [68Ga]Ga-THP-APN09, a novel PD-L1 targeted nanobody radiotracer for rapid one-step radiolabeling and PET imaging.

PURPOSE: Programmed cell death protein-1/ligand-1 (PD-1/L1) blockade has been a breakthrough in the treatment of patients with non-small cell lung cancer (NSCLC), but there is still a lack of effective methods to screen patients. Here we report a novel 68 Ga-labeled nanobody [68 Ga]Ga-THP-APN09 for PET imaging of PD-L1 status in mouse models and a first-in-human study in NSCLC patients. METHODS: [68 Ga]Ga-THP-APN09 was prepared by site-specific radiolabeling, with no further purification. Cell uptake assays were completed in the human lung adenocarcinoma cell line A549, NSCLC cell line H1975 and human PD-L1 gene-transfected A549 cells (A549PD-L1). The imaging to image PD-L1 status and biodistribution were investigated in tumor-bearing mice of these three tumor cell types. The first-in-human clinical translational trial was registered as NCT05156515. The safety, radiation dosimetry, biodistribution, and correlations of tracer uptake with immunohistochemical staining and major pathologic response (MPR) were evaluated in NSCLC patients who underwent adjuvant immunotherapy combined with chemotherapy. RESULTS: Radiosynthesis of [68 Ga]Ga-THP-APN09 was achieved at room temperature and a pH of 6.0-6.5 in 10 min with a high radiochemical yield (> 99%) and 13.9-27.8 GBq/µmol molar activity. The results of the cell uptake study reflected variable levels of surface PD-L1 expression observed by flow cytometry in the order A549PD-L1 > H1975 > A549. In small-animal PET/CT imaging, H1975 and A549PD-L1 tumors were clearly visualized in an 8.3:1 and 2.2:1 ratios over PD-L1-negative A549 tumors. Ex vivo biodistribution studies showed that tumor uptake was consistent with the PET results, with the highest A549PD-L1 being taken up the most (8.20 ± 0.87%ID/g), followed by H1975 (3.69 ± 0.50%ID/g) and A549 (0.90 ± 0.16%ID/g). Nine resectable NSCLC patients were enrolled in the clinical study. Uptake of [68 Ga]Ga-THP-APN09 was mainly observed in the kidneys and spleen, followed by low uptake in bone marrow. The radiation dose is within a reliable range. Tumor uptake was positively correlated with PD-L1 expression TPS (rs = 0.8763, P = 0.019). Tumor uptake of [68 Ga]Ga-THP-APN09 (SUVmax) in MPR patients was higher than that in non-MPR patients (median SUVmax 2.73 vs. 2.10, P = 0.036, determined with Mann-Whitney U-test). CONCLUSION: [68 Ga]Ga-THP-APN09 has the potential to be transformed into a kit-based radiotracer for rapid, simple, one-step, room temperature radiolabeling. The tracer can detect PD-L1 expression levels in tumors, and it may make it possibility to predict the response of PD-1 immunotherapy combined with chemotherapy. Confirmation in a large number of cases is needed. TRIAL REGISTRATION: Clinical Trial (NCT05156515). Registered 12 December 2021.

IgG-Binding Nanobody Capable of Prolonging Nanobody-Based Radiotracer Plasma Half-Life and Enhancing the Efficacy of Tumor-Targeted Radionuclide Therapy.

Nanobodies have been developed rapidly as targeted probes for molecular imaging owing to their high affinity, outstanding tissue penetration, and rapid blood clearance. However, the short retention time at the tumor site limits their application in targeted radionuclide therapy. In this study, we designed a dual-targeting nanobody referred to as MIRC213-709, which can specifically bind to the HER2 receptor in tumor cell lines with high affinity (by nanobody MIRC213) and endogenous IgG in plasma to prolong the half-life by the MIRC213 C-terminal fusion nanobody, MIRC709. The nanobodies were site-specifically radiolabeled with 99mTc and 177Lu, and radiochemical purity was >95% after purification. The long blood circulation time and tumor retention property of 99mTc/177Lu-MIRC213-709 were confirmed by a blood clearance assay, single-photon emission computed tomography (SPECT), and a biodistribution study. The blood clearance assay showed that the distribution phase half-life (T1/2α) and elimination phase half-life (T1/2ß) of 99mTc-MIRC213-709 were 6.74- and 19.04-fold longer than those of 99mTc-MIRC213, respectively. The SPECT/CT and biodistribution results showed that the highest uptake of 177Lu-MIRC213 in the NCI-N87 model was 5.24 ± 0.95% ID/g at 6 h p.i., while the highest uptake of 177Lu-MIRC213-709 in the NCI-N87 model was 30.82 ± 7.29% ID/g at 48 h p.i. Compared with 177Lu-MIRC213, 177Lu-MIRC213-709 had a 16.9-fold increased tumor cumulative uptake (2606 ± 195.1 vs 153.9 ± 22.37% ID/g·h). The targeted radionuclide therapy assay was performed in the NCI-N87 tumor model, and treatment monitoring ended on day 32. The post-treatment/pretreatment tumor volumes were 12.99 ± 1.66, 3.58 ± 0.96, 1.26 ± 0.17, and 1.54 ± 0.50 in the 0, 9, and 18 MBq single-dose groups and the two 9 MBq divided dose group (14 days apart), respectively. All treatment groups showed significant therapeutic effects (P < 0.0001). Thus, fusion with the IgG-binding nanobody MIRC709 provides MIRC213 derivatives with improved metabolic properties for targeted radionuclide therapy.

Analysis and Monitoring of Indoor Radon Concentrations of 37 Kindergartens - Beijing Municipality, China, 2023.

Introduction: Radon (222Rn or 222radon) is a radioactive gas emitted from building materials, foundations, and soil. Children are especially susceptible to radon exposure, underscoring the need to assess indoor radon levels in kindergartens. This study monitored radon concentrations in 37 Beijing kindergartens from June to October 2023. Methods: A random sample of 37 kindergartens was selected from 18 administrative districts in Beijing. The indoor radon concentration was measured using the solid track accumulation method, with radon detectors continuously monitored over a 3-month period. Results: The mean indoor radon level in 37 kindergartens, observed at 252 monitoring points, was 84.3 Bq/m3, with values varying from 12.9 to 263.5 Bq/m3. About 20.2% of points showed radon levels between 100.0 and 200.0 Bq/m3, while 2.4% exceeded 200.0 Bq/m3. Notably, radon levels were significantly elevated on the ground floor compared to the upper floors. Conclusion: Indoor radon levels in 37 kindergartens remained below the national standard limit of 300.0 Bq/m3 for buildings (GB/T 16146-2015). Nonetheless, 18.9% of the kindergartens exceeded the 100.0 Bq/m3 limit set for new constructions. It is advised to improve radon monitoring in kindergartens and consider developing a national standard for maximum permissible radon levels in such facilities.

Myoglobin-loaded gadolinium nanotexaphyrins for oxygen synergy and imaging-guided radiosensitization therapy.

Gadolinium (Gd3+)-coordinated texaphyrin (Gd-Tex) is a promising radiosensitizer that entered clinical trials, but temporarily fails largely due to insufficient radiosensitization efficacy. Little attention has been given to using nanovesicles to improve its efficacy. Herein, Gd-Tex is transformed into building blocks "Gd-Tex-lipids" to self-assemble nanovesicles called Gd-nanotexaphyrins (Gd-NTs), realizing high density packing of Gd-Tex in a single nanovesicle and achieving high Gd-Tex accumulation in tumors. To elucidate the impact of O2 concentration on Gd-Tex radiosensitization, myoglobin (Mb) is loaded into Gd-NTs (Mb@Gd-NTs), resulting in efficient relief of tumor hypoxia and significant enhancement of Gd-Tex radiosensitization, eventually inducing the obvious long-term antitumor immune memory to inhibit tumor recurrence. In addition to Gd3+, the versatile Mb@Gd-NTs can also chelate 177Lu3+ (Mb@177Lu/Gd-NTs), enabling SPECT/MRI dual-modality imaging for accurately monitoring drug delivery in real-time. This "one-for-all" nanoplatform with the capability of chelating various trivalent metal ions exhibits broad clinical application prospects in imaging-guided radiosensitization therapy.

Functional Immune Cell-Derived Exosomes Engineered for the Trilogy of Radiotherapy Sensitization.

The limited efficacy of radiotherapy leads to radio-resistance and high rates of tumor recurrence and metastasis, which is caused by tumor hypoxia, rapid DNA damage repair, and especially the suppressive immune microenvironment of tumor. Lots of immune cell-derived exosomes can regulate antitumor immunity, but their application in enhancing radiotherapy is rarely studied. Herein, as a model of concept, M1 macrophage-derived exosomes (M1Exos) is engineered as effective radiotherapy sensitizers, realizing the trilogy of radiotherapy sensitization: 1) M1Exos is engineered to express catalases on the inside of membrane, which can effectively relieve tumor hypoxia, and enhance DNA damage. 2) The DNA damage repair inhibitor is loaded in M1Exos to effectively inhibit DNA damage repair. 3) M1Exos can polarize M2 macrophages into M1 phenotypes, and the anti-PD-L1 nanobody engineered on the outside of M1Exos can relieve the immunosuppression of T cells, both ultimately leading to the remodeling of the tumor suppressive microenvironment. The trilogy of radiotherapy sensitization achieves excellent antitumor efficacy, exhibiting the good utility of engineering immune cell-derived exosomes as radiotherapy sensitizers, inspiring the future efforts to explore different kinds of immune cell-derived exosomes for enhanced radiotherapy.

HER2-targeted dual radiotracer approach with clinical potential for noninvasive imaging of trastuzumab-resistance caused by epitope masking.

Rationale: The decreased HER2-accessibility by epitope masking is a primary trastuzumab-resistance mechanism. In this study, we developed a HER2-targeted dual radiotracer approach to predict the HER2-trastuzumab engagement noninvasively. Methods: Two novel HER2-specific VHHs, MIRC208 and MIRC213, were acquired by immunizing alpaca with human HER2 protein, and were site-specifically labeled with 99mTc. Biodistribution and SPECT/CT imaging studies were performed in mice bearing HER2-positive and HER2-negative tumors. The HER2 binding sites of 99mTc-MIRC208 and 99mTc-MIRC213 were investigated by cell binding and SPECT/CT imaging studies. We evaluated the therapeutic predictive ability of our dual-radiotracer imaging approach for trastuzumab treatment in mice bearing MUC4-positive tumors (trastuzumab-resistant JIMT-1 and 87MUC4) and MUC4-negative tumors (trastuzumab-sensitive 7HER2 and NCI-N87). The preliminary clinical studies of 99mTc-MIRC208 were performed in two patients with HER2-positive breast tumors. Results:99mTc-MIRC208 and 99mTc-MIRC213 clearly visualized HER2-positive tumors, but not HER2-negative tumors. 99mTc-MIRC208 competes with trastuzumab for HER2-binding while 99mTc-MIRC213 recognizes HER2 on an epitope that is not masked by MUC4. The SPECT/CT studies with 99mTc-MIRC208 and 99mTc-MIRC213 clearly showed that the MUC4-negative and trastuzumab-sensitive 7HER2 and NCI-N87 tumors had very similar tumor uptake with the SUV208/SUV213 (2 h) ratios of 1.11 ± 0.17 in 7HER2 and 1.25 ± 0.22 in NCI-N87. However, the MUC4-positive JIMT-1 tumors showed the decreased SUV208/SUV213 (2 h) ratio (0.63 ± 0.07), which correlated well with the low response rate to trastuzumab therapy. The SUV208/SUV213 (2 h) ratio was reduced to 0.72 ± 0.02 in MUC4-expressing NCI-N87 cells, and resulting in the decreased trastuzumab sensitivity, further supporting the correlation between the SUV208/SUV213 (2 h) ratio and trastuzumab-sensitivity. The primary and metastatic HER2-positive lesions of patients were clearly visualized by 99mTc-MIRC208 SPECT at 2 h post injection. Conclusion: Overall, we demonstrated that the dual radiotracer imaging strategy is a valid noninvasive approach for the cancer patient selection before trastuzumab therapy. 99mTc-MIRC213 SPECT is utilized to quantify the tumor HER2 expression and screen HER2-positive cancer patients, while 99mTc-MIRC208 SPECT is used to determine the HER2-accessibility of trastuzumab. The SUV208/SUV213 (2 h) ratio is an important biomarker to determine the responsiveness of trastuzumab therapy.

High Intensity Focused Ultrasound-Responsive and Ultrastable Cerasomal Perfluorocarbon Nanodroplets for Alleviating Tumor Multidrug Resistance and Epithelial-Mesenchymal Transition.

Hypoxia is a hostile hallmark of most solid tumors, which often leads to multidrug resistance (MDR) and causes the failure of chemotherapy. Hypoxia also promotes epithelial-mesenchymal transition (EMT), leading to acceleration of tumor metastasis. Many chemotherapeutic drugs can further exacerbate hypoxia and thus promote metastasis. Therefore, relieving hypoxia is necessary for chemotherapy to inhibit both MDR and EMT. Herein, highly stable cerasomal perfluorocarbon nanodroplets with an atomic layer of polyorganosiloxane surface and pH-sensitive tumor-targeting peptide (D-vPCs-O2) were fabricated to co-deliver oxygen and therapeutic drug, doxorubicin. High-intensity focused ultrasound (HIFU) was utilized to trigger the co-release of doxorubicin and oxygen and simultaneously enhance ultrasound imaging, therefore achieving imaging-guided drug delivery. Mild-temperature HIFU (M-HIFU) not only triggered oxygen release from nanodroplets but also slightly elevated tumor temperature to accelerate tumor blood flow. The oxygen release and temperature elevation jointly relieved tumor hypoxia and alleviated MDR, which greatly enhanced the drug therapeutic efficacy as compared to clinically used doxorubicin and Doxil. Overall side effects were also largely reduced owing to the ultrastable drug loading of cerasome. The improvement of insufficient chemotherapy and the relief of tumor hypoxia corporately down-regulated TGF-ß1, leading to the alleviation of EMT, and therefore significantly inhibited tumor metastasis. When "D-vPCs-O2 + M-HIFU" was utilized as a neoadjuvant chemotherapy, nanodroplets down-regulated heat shock proteins, reducing tumor relapse after the high-temperature HIFU (H-HIFU)-mediated hyperthermia ablation. The chemo-hyperthermia therapy totally eradicated tumors without any relapse or metastasis, providing a promising way to treat the triple-negative breast cancer, which is highly malignant, easily metastatic, and lacks effective treatments.

Monoclonal-Antibody-Templated Gold Nanoclusters for HER2 Receptors Targeted Fluorescence Imaging.

HER2 receptor-specific monoclonal-antibody-templated gold nanoclusters, Herceptin-templated Au NCs (Her-Au NCs), have been successfully obtained via "green" synthesis. This strategy allows the fluorescent gold nanoclusters (Au NCs) formed in the three-dimensional structure of Herceptin without destroying the high specificity and affinity to HER2 receptors. The Her-Au NCs have been found to be superior compared to Cy3-Herceptin in the fluorescence emission (λem = 645 nm) and the photostability under high-intensity UV irradiation or long-time storage. Moreover, Her-Au NCs can achieve receptor-specific imaging without targeted modification owing to the HER2-binding ability of the Herceptin scaffold. For imaging applications, Her-Au NCs can be utilized as effective optical probes for not only fluorescence imaging of HER2-positive cancer cells but also imaging of HER2-positive tumors in vivo.

Host-Guest Polypyrrole Nanocomplex for Three-Stimuli-Responsive Drug Delivery and Imaging-Guided Chemo-Photothermal Synergetic Therapy of Refractory Thyroid Cancer.

Despite the good prognosis of the low-risk thyroid cancer, there are no truly effective treatments for radioactive iodine-refractory thyroid cancer. Herein, a novel theranostic nanoplatform, as well as a smart doxorubucin (DOX) delivery system is fabricated. Gelatin-stabilized polypyrrole nanoparticles are reported for the first time. The combination of gelatin-stabilized polypyrrole and cyclodextrin-DOX complexes enabling three-stimuli-controlled drug delivery, including the enzyme-sensitive, pH-sensitive and photothermal-sensitive drug release, exhibiting a new way to equip photothermal agents with precisely controlled drug delivery. Anti-galectin-3 antibodies are utilized as the targeting molecules of nanoparticles in the first time, which surprisingly increase intracellular DOX uptake by enhanced clathrin-mediated endocytosis, showing galectin-3 can be employed as a highly efficient target of drug delivery systems. The nanoparticles achieve excellent photoacoustic imaging effect, enabled chemo-photothermal combined therapy with pinpointed drug delivery. Compared to free DOX, these multifunctional nanoparticles decrease the heart damage, but greatly increase the tumor/heart ratio of DOX concentration by 12.9-fold. The tumors are completely eradicated without any recurrence after the in vivo combined therapy. To the best of the authors' knowledge, this is also the first report to apply photoacoustic imaging-guided chemo-photothermal therapy for thyroid cancer, showing great potential to solve the dilemma in thyroid cancer therapy.

Lectin-Mediated pH-Sensitive Doxorubicin Prodrug for Pre-Targeted Chemotherapy of Colorectal Cancer with Enhanced Efficacy and Reduced Side Effects.

Doxorubicin (DOX) has been clinically used as a broad-spectrum chemotherapeutic agent for decades, but its clinical application is hindered by the lack of tumour specificity, severe cardiotoxicity and haematotoxicity. Pre-targeted strategies are highly tumour-specific, therapeutic approaches. Herein, a novel pre-targeted system was constructed, aiming to enhance anticancer efficacy of DOX and maximally reduce its side effects. Methods: The DOX prodrug (bDOX) was first synthesized by conjugating DOX with mini-PEGylated (mPEGylated) biotin through a pH-sensitive bond. During the pre-targeted treatment, avidin was first administrated. After an optimized interval, bDOX was second administrated. The nontoxic prodrug bDOX was eventually transformed into the toxic anticancer form (DOX) by a pH-triggered cleavage specifically in tumour cells. The drug efficacy and side effect of the two-step, pre-targeted treatment were fully compared with free DOX in vitro and in vivo. Results: The prodrug bDOX was quite stable under neutral conditions and nearly nontoxic, but was immediately transformed into the toxic anticancer form (DOX) under acidic conditions. Compared to free DOX, the pre-targeted bDOX exhibited a higher cellular uptake by human colorectal tumour cells (LS180 and HT-29 cells). In vivo evaluation performed on LS180 xenograft animal model demonstrated that the pre-targeted bDOX achieved a much more significant tumour inhibition than free DOX. The largely decreased, unwanted bystander toxicity was demonstrated by changes in body weight, cardiomyocyte apoptosis, blood routine examination and splenic pathological changes. Conclusion: The high therapeutic efficacy, together with the minimal side effects, of this easily synthesized, pre-targeted system exhibited immense potentiality for the clinical application of DOX delivery.

The decline of pregnancy rate and abnormal uterine responsiveness of steroid hormones in aging mice.

Reproductive capacity in animals and women declines with increasing age. Although ovarian aging is considered as a main cause for the decline of pregnancy rate, whether uterine aging occurs remains unclear. Even if blastocysts are transferred from young donors to older pseudopregnant recipients, the rate of implantation is still low, suggesting the occurrence of uterine aging. In this study, we compared the pregnancy rate and the uterine responsiveness of steroid hormones in ovariectomized mice at age between 2- and 12-month-old. Compared to 2-month-old mice, there is a significant decrease of both pregnancy rate and the number of implantation sites in 12-month-old mice. In ovariectomized mice, the uterine responsiveness of steroid hormones is also significantly different between 2- and 12-month-old mice. On day 4, Muc1 and PR level in 12-month-old mice is significantly higher than that in 2-month-old mice, while Hand2 level is significantly lower in 12-month-old mice. Our data suggest that the abnormal responsiveness of steroid hormones may contribute to the decline of pregnancy rate in 12-month-old mice.

Progesterone induces the expression of lipocalin-2 through Akt-c-Myc pathway during mouse decidualization.

Lipocalin-2 (Lcn2) is a small glycoprotein involved in a number of biological processes such as inflammation and antibacterial response. In our study, Lcn2 is expressed in the subluminal stromal cells at implantation site on day 5 of pregnancy. The expression of Lcn2 in stromal cells is under the control of progesterone through Akt-c-Myc signaling pathway. Data from Lcn2 knockdown and recombinant protein treatments indicate that Lcn2 promotes mPGES-1 expression in stromal cells. The expression of Lcn2 and mPGES-1 is strongly stimulated by lipopolysaccharide (LPS), indicating that Lcn2 mediates LPS-induced inflammation. These findings shed light on the role of Lcn2 during decidualization.

Hyaluronic Acid-Coated Silver Nanoparticles As a Nanoplatform for in Vivo Imaging Applications.

An efficient chemical reduction protocol has been developed for the synthesis of hyaluronic acid-coated silver nanoparticles (HA-Ag NPs) that are spherical, ultrasmall and monodisperse. The as-synthesized HA-Ag NPs not only exhibited excellent long-term stability and low cytotoxicity but also could be used as a nanoplatform for X-ray computed tomography (CT) and single-photon emission computed tomography (SPECT) imaging after being radiolabeled with 99mTc.