ImmunoPET of CD146 in Orthotopic and Metastatic Breast Cancer Models

Theranostic role of 89Zr- and 177Lu-labeled aflibercept in breast cancer

PURPOSE

Triple-negative breast cancer (TNBC) has a poor prognosis due to the absence of effective therapeutic targets. Vascular endothelial growth factor (VEGF) family are expressed in 30-60% of TNBC, therefore providing potential therapeutic targets for TNBC. Aflibercept (Abe), a humanized recombinant fusion protein specifically bound to VEGF-A, B and placental growth factor (PIGF), has proven to be effective in the treatment in some cancers. Therefore, 89Zr/177Lu-labeled Abe was investigated for its theranostic role in TNBC.

METHODS

Abe was radiolabeled with 89Zr and 177Lu via the conjugation of chelators. Flow cytometry and cell immunofluorescent staining were performed to evaluate the binding affinity of Abe. Sequential PET imaging and fluorescent imaging were conducted in TNBC tumor bearing mice following the injection of 89Zr-labeled Abe and Cy5.5-labeled Abe. Treatment study was performed after the administration of 177Lu-labeled Abe. Tumor volume and survival were monitored and SPECT imaging and biodistribution studies were conducted. Safety evaluation was performed including body weight, blood cell measurement, and hematoxylin-eosin (H&E) staining of major organs. Expression of VEGF and CD31 was tested by immunohistochemical staining. Dosimetry was estimated using the OLINDA software.

RESULTS

FITC-labeled Abe showed a strong binding affinity to VEGF in TNBC 4T1 cells and HUVECs by flow cytometry and cell immunofluorescence. Tumor uptake of 89Zr-labeled Abe peaked at 120 h (SUVmax = 3.2 ± 0.64) and persisted before 168 h (SUVmax = 2.54 ± 0.42). The fluorescence intensity of the Cy5.5-labeled Abe group surpassed that of the Cy5.5-labeled IgG group, implying that Cy5.5-labeled Abe is a viable candidate monitoring in vivo tumor targeting and localization. 177Lu-labeled Abe (11.1 MBq) served well as the therapeutic component to suppress tumor growth with standardized tumor volume at 16 days, significantly smaller than PBS group (about 815.66 ± 3.58% vs 3646.52 ± 11.10%, n = 5, P < 0.01). Moreover, SPECT images confirmed high contrast between tumors and normal organs, indicating selective tumor uptake of 177Lu-labeled Abe. No discernible abnormalities in blood cells, and no evident histopathological abnormality observed in liver, spleen, and kidney. Immunohistochemical staining showed that 177Lu-labeled Abe effectively inhibited the expression of VEGF and CD31 of tumor, suggesting that angiogenesis may be suppressed by 177Lu-labeled Abe. The whole-body effective dose for an adult human was estimated to be 0.16 mSv/MBq.

CONCLUSION

89Zr/177Lu-labeled Abe could be a TNBC-specific marker with diagnostic value and provide insights into targeted therapy in the treatment of TNBC. Further clinical evaluation and translation may be of high significance for TNBC.

Molecular imaging of tumour-associated pathological biomarkers with smart nanoprobe: From "Seeing" to "Measuring"

Although the extraordinary progress has been made in molecular biology, the prevention of cancer remains arduous. Most solid tumours exhibit both spatial and temporal heterogeneity, which is difficult to be mimicked in vitro. Additionally, the complex biochemical and immune features of tumour microenvironment significantly affect the tumour development. Molecular imaging aims at the exploitation of tumour-associated molecules as specific targets of customized molecular probe, thereby generating image contrast of tumour markers, and offering opportunities to non-invasively evaluate the pathological characteristics of tumours in vivo. Particularly, there are no "standard markers" as control in clinical imaging diagnosis of individuals, so the tumour pathological characteristics-responsive nanoprobe-based quantitative molecular imaging, which is able to visualize and determine the accurate content values of heterogeneous distribution of pathological molecules in solid tumours, can provide criteria for cancer diagnosis. In this context, a variety of "smart" quantitative molecular imaging nanoprobes have been designed, in order to provide feasible approaches to quantitatively visualize the tumour-associated pathological molecules in vivo. This review summarizes the recent achievements in the designs of these nanoprobes, and highlights the state-of-the-art technologies in quantitative imaging of tumour-associated pathological molecules.

CD146-targeted nuclear medicine imaging in cancer: state of the art

The transmembrane glycoprotein adhesion molecule CD146 is overexpressed in a wide variety of cancers. Through molecular imaging, a specific biomarker's expression and distribution can be viewed in vivo non-invasively. Radionuclide-labeled monoclonal antibodies or relevant fragments that target CD146 may find potential applications in cancer imaging, thereby offering tremendous value in cancer diagnosis, staging, prognosis evaluation, and prediction of drug resistance. This review discusses the recent developments of CD146-targeted molecular imaging via nuclear medicine, especially in malignant melanoma, brain tumor, lung cancer, liver cancer, breast cancer, and pancreatic cancer. Many studies have proved that CD146 targeting may present a promising strategy for cancer theranostics.

Dual-Targeting PET Tracers Enable Enzyme-Mediated Self-Assembly for the PET Imaging of Legumain Activity

Legumain, a lysosomal cysteine protease overexpressed in a variety of tumors, has been considered a promising biomarker for various cancers. Precise detection of legumain activity in the lysosome represents an important strategy for early diagnosis and prognosis of tumors. Small-molecule probes with the property of target-enabled self-assembly hold great potential for molecular imaging. In this study, we reported two dual-targeting radiotracers ([18F]SF-AAN-M and [18F]SF-AAN-HEM) with a property of legumain-mediated self-assembly for positron emission tomography (PET) imaging. Both the radiotracers were synthesized with high labeling yield (>50%) and the radiochemical purity was over 99% via one-step straightforward 18F-labeling. Both tracers were efficiently activated by the reducing agent and legumain to self-assemble into aggregates and showed enhanced retention in legumain-overexpressed MDA-MB-468 cells and tumors, indicating that the introduction of lysosome-targeting morpholine increased the tumor uptake and extended the retention of radiotracers in legumain-overexpressed tumors. In addition, [18F]SF-AAN-HEM with a hydrophilic (histidine-glutamate)3 tag displayed significantly reduced liver uptake with no conspicuous reduction in tumor uptake, affording high signal-to-noise ratios (tumor/liver and tumor/muscle). All of these results suggest that dual-targeting tracer [18F]SF-AAN-HEM could provide a promising tool for in vivo monitoring legumain activity in tumors.

Advances in PET/CT Imaging for Breast Cancer

One out of eight women will be affected by breast cancer during her lifetime. Imaging plays a key role in breast cancer detection and management, providing physicians with information about tumor location, heterogeneity, and dissemination. In this review, we describe the latest advances in PET/CT imaging of breast cancer, including novel applications of 18F-FDG PET/CT and the development and testing of new agents for primary and metastatic breast tumor imaging and therapy. Ultimately, these radiopharmaceuticals may guide personalized approaches to optimize treatment based on the patient's specific tumor profile, and may become a new standard of care. In addition, they may enhance the assessment of treatment efficacy and lead to improved outcomes for patients with a breast cancer diagnosis.

PET/CT in Patients with Breast Cancer Treated with Immunotherapy

Significant advances in breast cancer (BC) treatment have been made in the last decade, including the use of immunotherapy and, in particular, immune checkpoint inhibitors that have been shown to improve the survival of patients with triple negative BC. This narrative review summarizes the studies supporting the use of immunotherapy in BC. Furthermore, the usefulness of 2-deoxy-2-[¹⁸F]fluoro-D-glucose (2-[¹⁸F]FDG) positron emission/computerized tomography (PET/CT) to image the tumor heterogeneity and to assess treatment response is explored, including the different criteria to interpret 2-[¹⁸F]FDG PET/CT imaging. The concept of immuno-PET is also described, by explaining the advantages of mapping treatment targets with a non-invasive and whole-body tool. Several radiopharmaceuticals in the preclinical phase are referred too, and, considering their promising results, translation to human studies is needed to support their use in clinical practice. Overall, this is an evolving field in BC treatment, despite PET imaging developments, the future trends also include expanding immunotherapy to early-stage BC and using other biomarkers.

Theranostic application of 64Cu/177Lu-labeled anti-Trop2 monoclonal antibody in pancreatic cancer tumor models

PURPOSE

Pancreatic cancer is a malignant tumor with a high degree of malignancy, strong heterogeneity, and high lethality. Trop2 is a transmembrane glycoprotein associated with the occurrence, development, and poor prognosis of pancreatic cancer. This study aims to develop ⁶⁴Cu/¹⁷⁷Lu-labeled anti-Trop2 monoclonal antibody (hIMB1636) for positron emission tomography (PET) imaging and radioimmunotherapy (RIT) application in pancreatic cancer tumor models.

METHODS

The binding kinetics of hIMB1636 to Trop2 antigen was measured by Biolayer interferometry (BLI). Western blotting was used to screen the Trop2 expression of pancreatic cancer cell lines. Flow cytometry and cell immunofluorescence were used to evaluate the binding ability of hIMB1636 and Trop2 on the cell surface. hIMB1636 were conjugated with p-SCN-Bn-NOTA (NOTA) and DOTA-NHS-ester (DOTA) for ⁶⁴Cu and ¹⁷⁷Lu radiolabeling respectively. ImmunoPET imaging and RIT studies were performed using ⁶⁴Cu-NOTA-hIMB1636 and ¹⁷⁷Lu-DOTA-hIMB1636 in subcutaneous pancreatic cancer tumor models.

RESULTS

hIMB1636 had a strong binding affinity to Trop2 according to the results of BLI. The T3M-4 cell line showed the strongest expression of Trop2 and specific binding ability of hIMB1636 according to the results of Western blotting, flow cytometry, and cell immunofluorescence. The radiochemical purity of ⁶⁴Cu-NOTA-hIMB1636 and ¹⁷⁷Lu-DOTA-hIMB1636 exceeded 95%. PET imaging showed gradually an accumulation of ⁶⁴Cu-NOTA-hIMB1636 in T3M-4 tumor models. The maximum tumor uptake was 8.95 ± 1.07%ID/g (n = 4) at 48 h post injection (p.i.), which had significant differences with T3M-4-blocked and PaTu8988-negative groups (P < 0.001). The high-¹⁷⁷Lu-hIMB1636 group demonstrated the strongest tumor suppression with standardized tumor volume about 94.24 ± 14.62% (n = 5) at 14 days p.i., significantly smaller than other groups (P < 0.05). Ex vivo biodistribution and histological staining verified the in vivo PET imaging and RIT results.

CONCLUSIONS

This study demonstrated that ⁶⁴Cu/¹⁷⁷Lu-labeled hIMB1636 could noninvasively evaluate the expression level of Trop2 and inhibit the Trop2-overexpressed tumor growth in pancreatic cancer tumor models. Further clinical evaluation and translation of Trop2-targeted drug may be of great help in the stratification and management of pancreatic cancer patients.

Soluble CD146 in the detection and grading of intravascular and tissue congestion in patients with acute dyspnoea: analysis of the prospective observational Lithuanian Echocardiography Study of Dyspnoea in Acute Settings (LEDA) cohort

OBJECTIVES

To evaluate the potential of soluble cluster of differentiation 146 (sCD146) in the detection and grading of congestion in patients with acute dyspnoea.

DESIGN

Subanalysis of the prospective observational Lithuanian Echocardiography Study of Dyspnoea in Acute Settings (LEDA) cohort.

SETTING

Two Lithuanian university centres.

PARTICIPANTS

Adult patients with acute dyspnoea admitted to the emergency department.

METHODS

Congestion was assessed using clinical and sonographic parameters. All patients underwent sCD146 and N-terminal pro-B-type natriuretic peptide (NT-proBNP) testing.

RESULTS

The median value of sCD146 concentration in the study cohort (n=437) was 405 (IQR 315-509) ng/mL. sCD146 was higher in patients with peripheral oedema than in those without (median (IQR) 472 (373-535) vs 400 (304-501) ng/mL, p=0.009) and with pulmonary rales than in those without (439 (335-528) vs 394 (296-484) ng/mL, p=0.001). We found a parallel increase of estimated right atrial pressure (eRAP) and sCD146 concentration: sCD146 was 337 (300-425), 404 (290-489) and 477 (363-572) ng/mL in patients with normal, moderately elevated and high eRAP, respectively (p=0.001). In patients with low NT-proBNP, high sCD146 distinguished a subgroup with a higher prevalence of oedema as compared with patients with low levels of both biomarkers (76.0% vs 41.0%, p=0.010). Moreover, high sCD146 indicated a higher prevalence of elevated eRAP, irrespective of NT-proBNP concentration (p<0.05).

CONCLUSION

sCD146 concentration reflects the degree of intravascular and tissue congestion assessed by clinical and echocardiographic indices, with this association maintained in patients with low NT-proBNP. Our data support the notion that NT-proBNP might represent heart stretch while sCD146 rather represents peripheral venous congestion.

Immuno-PET Imaging of TNF-α in Colitis Using 89Zr-DFO-infliximab

Tumor necrosis factor-alpha (TNF-α) neutralization has become increasingly important in the treatment of inflammatory bowel diseases (IBD). A series of monoclonal antibodies were approved in the clinic for anti-TNF-α therapy. However, a comprehensive assessment of TNF-α levels throughout the colon, which facilitates the diagnosis of IBD and predicts anti-TNF-α efficacy, remains challenging. Here, we radiolabeled infliximab with long-lived radionuclides ⁸⁹Zr for immuno-positron emission tomography (PET) imaging of TNF-α in vivo. The increased TNF-α level was detected in the inflammatory colon of the dextran sodium sulfate-induced colitis mice. The immuno-PET imaging of ⁸⁹Zr-desferrioxamine-infliximab reveals a high uptake (7.1 ± 0.3%ID/g) in the inflammatory colon, which is significantly higher than in the healthy control and blocked groups. The colon-to-muscle ratio reached more than 10 and was maintained at a high level for 10 h after injection. The ex vivo biodistribution study also verified the superior uptake in the inflammatory colon. This study provides an in vivo immune-PET approach to molecular imaging of the pro-inflammatory cytokine TNF-α. It is promising in diagnosing and predicting efficacy in both IBD and other autoimmune diseases.

An Enzyme-Activatable Aggregation-Induced-Emission Probe: Intraoperative Pathological Fluorescent Diagnosis of Pancreatic Cancer via Specific Cathepsin E

Pancreatic cancer (PC) is one of the most devastating malignant tumors. However, fluorescence probes for early clinical diagnosis of PC often encounter difficulties in accuracy and penetrability. In this work, an enzyme-activated aggregation-induced-emission (AIE) probe, QM-HSP-CPP, for high-contrast fluorescence diagnosis of PC is developed by monitoring specific overexpressed enzyme Cathepsin E (CTSE). The probe is composed of an AIE fluorophore QM-COOH (QM = quinoline-malononitrile), CTSE-triggered hydrophobic peptide (HSP), and hydrophilic biocompatible cell penetrating peptide (CPP). The CPP unit can well-modulate the molecular dispersion properties, giving initial fluorescence-off state in the aqueous biosystem, thus endowing high signal-to-noise ratio, and finally overcoming the poor targeting selectivity of traditional AIE probes. CPP can ensure cell/tissue penetrating ability, thus allowing on-site monitoring of endogenous CTSE in PC cells, tissues, and living animal models. When the QM-HSP-CPP probe is specifically cleaved by CTSE, it can generate AIE signals in situ with high-specificity and long-term tracking ability, and successfully achieve intraoperative diagnosis of human PC sections, tracking PC in heterotopic nude mice models. The CTSE-enzyme-triggered AIEgens' liberation strategy improves accuracy and addresses the penetration problem simultaneously, which can expand the database of multitudinous biocompatible AIE-active probes, especially for establishing intraoperative pathological fluorescent diagnosis.

Early Detection and Investigation of Extracellular Vesicles Biomarkers in Breast Cancer

Breast cancer (BC) is the most commonly diagnosed malignant tumor in women worldwide, and the leading cause of cancer death in the female population. The percentage of patients experiencing poor prognosis along with the risk of developing metastasis remains high, also affecting the resistance to current main therapies. Cancer progression and metastatic development are no longer due entirely to their intrinsic characteristics, but also regulated by signals derived from cells of the tumor microenvironment. Extracellular vesicles (EVs) packed with DNA, RNA, and proteins, are the most attractive targets for both diagnostic and therapeutic applications, and represent a decisive challenge as liquid biopsy-based markers. Here we performed a study based on a multiplexed phenotyping flow cytometric approach to characterize BC-derived EVs from BC patients and cell lines, through the detection of multiple antigens. Our data reveal the expression of EVs-related biomarkers derived from BC patient plasma and cell line supernatants, suggesting that EVs could be exploited for characterizing and monitoring disease progression.

64Cu-labeled daratumumab F(ab')2 fragment enables early visualization of CD38-positive lymphoma

PURPOSE

Abnormal CD38 expression in some hematologic malignancies, including lymphoma, has made it a biomarker for targeted therapies. Daratumumab (Dara) is the first FDA-approved CD38-specific monoclonal antibody, enabling successfully immunoPET imaging over the past years. Radiolabeled Dara however has a long blood circulation and delayed tumor uptake which can limit its applications. The focus of this study is to develop ⁶⁴Cu-labeled Dara-F(ab')₂ for the visualization of CD38 in lymphoma models.

METHODS

F(ab')₂ fragment was prepared from Dara using an IdeS enzyme and purified with Protein A beads. Western blotting, flow cytometry, and surface plasmon resonance (SPR) were performed for in vitro assay. Probes were labeled with ⁶⁴Cu after the chelation of 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA). Small animal PET imaging and quantitative analysis were performed after injection of ⁶⁴Cu-labeled Dara-F(ab')₂, IgG-F(ab')₂, and Dara for evaluation in lymphoma models.

RESULTS

Flow cytometry and SPR assay proved the specific binding ability of Dara-F(ab')₂ and NOTA-Dara-F(ab')₂ in vitro. Radiolabeling yield of [⁶⁴Cu]Cu-NOTA-Dara-F(ab')₂ was over 90% and with a specific activity of 4.0 ± 0.6 × 10³ MBq/μmol (n = 5). PET imaging showed [⁶⁴Cu]Cu-NOTA-Dara-F(ab')₂ had a rapid and high tumor uptake as early as 2 h (6.9 ± 1.2%ID/g) and peaked (9.5 ± 0.7%ID/g) at 12 h, whereas [⁶⁴Cu]Cu-NOTA-Dara reached its tumor uptake peaked at 48 h (8.3 ± 1.4%ID/g, n = 4). In comparison, IgG-F(ab')₂ and HBL-1 control groups found no noticeable tumor uptake. [⁶⁴Cu]Cu-NOTA-Dara-F(ab')₂ had significantly lower uptake in blood pool, bone, and muscle than [⁶⁴Cu]Cu-NOTA-Dara and its tumor-to-blood and tumor-to-muscle ratios were significantly higher than controls.

CONCLUSIONS

[⁶⁴Cu]Cu-NOTA-Dara-F(ab')₂ showed a rapid and high tumor uptake in CD38-positive lymphoma models with favorable imaging contrast, showing its promise as a potential PET imaging agent for future clinical applications.