Anti-GD2-IRDye800CW as a targeted probe for fluorescence-guided surgery in neuroblastoma

Imaging adjuvants in pediatric surgical oncology

Surgery is a crucial component of pediatric cancer treatment, but conventional methods may lack precision. Image-guided surgery, including fluorescent and radioguided techniques, offers promise for enhancing tumor localization and facilitating precise resection. Intraoperative molecular imaging utilizes agents like indocyanine green to direct surgeons to occult deposits of tumor and to delineate tumor margins. Next-generation agents target tumors directly to improve specificity. Radioguided surgery, employing tracers like metaiodobenzylguanidine (MIBG), complements fluorescent techniques by allowing for detection of tumors at a greater depth. Dual-labeled agents combining both modalities are under development. Three-dimensional modeling and virtual/augmented reality aid in preoperative planning and intraoperative guidance. The above techniques show great promise to benefit patients with pediatric tumors, and their continued development will almost certainly improve surgical outcomes.

Antibody conjugates in neuroblastoma: a step forward in precision medicine

Neuroblastoma (NB) is a pediatric cancer that often manifests in a high-risk form and is characterized by frequent relapses and resistance to conventional therapies. This underscores the urgent need for more effective and targeted treatment strategies. One promising avenue has been the identification of unique or overexpressed surface antigens on neoplastic cells, which has facilitated the development of antibody conjugates and related technologies. These include antibody-drug conjugates (ADCs) and immunotoxins (ITs), which deliver cytotoxic agents directly to tumor cells, as well as antibody-fluorophore conjugates (AFCs), which bind to surface antigens with high specificity to target malignant tumors. Additionally, radioimmunotherapy (RIT) allows the precise delivery of radioactive isotopes linked to a monoclonal antibody directly to the tumor cells. ADCs, ITs, and RIT represent a novel class of anti-cancer agents offering precision therapy with reduced systemic toxicity, enabling longer and potentially more effective treatment regimens. Meanwhile, AFCs are valuable tools in diagnostics, aiding in detecting and characterizing malignant tissues. Despite advancements in antibody conjugates for NB, significant challenges persist, including optimizing payload delivery, mitigating off-target effects, and addressing tumor heterogeneity. Future research should also prioritize refining and integrating these technologies into multimodal treatment protocols to improve outcomes for pediatric NB patients.

Detection properties of indium-111 and IRDye800CW for intraoperative molecular imaging use across tissue phantom models

Significance

Intraoperative molecular imaging (IMI) enables the detection and visualization of cancer tissue using targeted radioactive or fluorescent tracers. While IMI research has rapidly expanded, including the recent Food and Drug Administration approval of a targeted fluorophore, the limits of detection have not been well-defined.

Aim

The ability of widely available handheld intraoperative tools (Neoprobe and SPY-PHI) to measure gamma decay and fluorescence intensity from IMI tracers was assessed while varying characteristics of both the signal source and the intervening tissue or gelatin phantoms.

Approach

Gamma decay signal and fluorescence from tracer-bearing tumors (TBTs) and modifiable tumor-like inclusions (TLIs) were measured through increasing thicknesses of porcine tissue and gelatin in custom 3D-printed molds. TBTs buried beneath porcine tissue were used to simulate IMI-guided tumor resection.

Results

Gamma decay from TBTs and TLIs was detected through significantly thicker tissue and gelatin than fluorescence, with at least 5% of the maximum signal observed through up to 5 and 0.5 cm, respectively, depending on the overlying tissue type or gelatin.

Conclusions

We developed novel systems that can be fine-tuned to simulate variable tumor characteristics and tissue environments. These were used to evaluate the detection of fluorescent and gamma signals from IMI tracers and simulate IMI surgery.

Dual-labeled anti-GD2 targeted probe for intraoperative molecular imaging of neuroblastoma

BACKGROUND

Surgical resection is integral for the treatment of neuroblastoma, the most common extracranial solid malignancy in children. Safely locating and resecting primary tumor and remote deposits of disease remains a significant challenge, resulting in high rates of complications and incomplete surgery, worsening outcomes. Intraoperative molecular imaging (IMI) uses targeted radioactive or fluorescent tracers to identify and visualize tumors intraoperatively. GD2 was selected as an IMI target, as it is highly overexpressed in neuroblastoma and minimally expressed in normal tissue.

METHODS

GD2 expression in neuroblastoma cell lines was measured by flow cytometry. DTPA and IRDye® 800CW were conjugated to anti-GD2 antibody to generate DTPA-αGD2-IR800. Binding affinity (Kd) of the antibody and the non-radiolabeled tracer were then measured by ELISA assay. Human neuroblastoma SK-N-BE(2) cells were surgically injected into the left adrenal gland of 3.5-5-week-old nude mice and the orthotopic xenograft tumors grew for 5 weeks. 111In-αGD2-IR800 or isotype control tracer was administered via tail vein injection. After 4 and 6 days, mice were euthanized and gamma and fluorescence biodistributions were measured using a gamma counter and ImageJ analysis of acquired SPY-PHI fluorescence images of resected organs (including tumor, contralateral adrenal, kidneys, liver, muscle, blood, and others). Organ uptake was compared by one-way ANOVA (with a separate analysis for each tracer/day combination), and if significant, Sidak's multiple comparison test was used to compare the uptake of each organ to the tumor. Handheld tools were also used to detect and visualize tumor in situ, and to assess for residual disease following non-guided resection.

RESULTS

111In-αGD2-IR800 was successfully synthesized with 0.75-2.0 DTPA and 2-3 IRDye® 800CW per antibody and retained adequate antigen-binding (Kd = 2.39 nM for aGD2 vs. 21.31 nM for DTPA-aGD2-IR800). The anti-GD2 tracer demonstrated antigen-specific uptake in mice with human neuroblastoma xenografts (gamma biodistribution tumor-to-blood ratios of 3.87 and 3.88 on days 4 and 6 with anti-GD2 tracer), while isotype control tracer did not accumulate (0.414 and 0.514 on days 4 and 6). Probe accumulation in xenografts was detected and visualized using widely available operative tools (Neoprobe® and SPY-PHI camera) and facilitated detection ofputative residual disease in the resection cavity following unguided resection.

CONCLUSIONS

We have developed a dual-labeled anti-GD2 antibody-based tracer that incorporates In-111 and IRDye® 800CW for radio- and fluorescence-guided surgery, respectively. The tracer adequately binds to GD2, specifically accumulates in GD2-expressing xenograft tumors, and enables tumor visualization with a hand-held NIR camera. These results encourage the development of 111In-αGD2-IR800 for future use in children with neuroblastoma, with the goal of improving patient safety, completeness of resection, and overall patient outcomes.

A multispectral 3D live organoid imaging platform to screen probes for fluorescence guided surgery

Achieving complete tumor resection is challenging and can be improved by real-time fluorescence-guided surgery with molecular-targeted probes. However, pre-clinical identification and validation of probes presents a lengthy process that is traditionally performed in animal models and further hampered by inter- and intra-tumoral heterogeneity in target expression. To screen multiple probes at patient scale, we developed a multispectral real-time 3D imaging platform that implements organoid technology to effectively model patient tumor heterogeneity and, importantly, healthy human tissue binding.

Monoclonal Antibodies for Targeted Fluorescence-Guided Surgery: A Review of Applicability across Multiple Solid Tumors

This study aims to review the status of the clinical use of monoclonal antibodies (mAbs) that have completed or are in ongoing clinical trials for targeted fluorescence-guided surgery (T-FGS) for the intraoperative identification of the tumor margins of extra-hematological solid tumors. For each of them, the targeted antigen, the mAb generic/commercial name and format, and clinical indications are presented, together with utility, doses, and the timing of administration. Based on the current scientific evidence in humans, the top three mAbs that could be prepared in a GMP-compliant bank ready to be delivered for surgical purposes are proposed to speed up the translation to the operating room and produce a few readily available "off-the-shelf" injectable fluorescent probes for safer and more effective solid tumor resection.

Children's Oncology Group's 2023 blueprint for research: Surgery

Surgery plays a crucial role in the treatment of children with solid malignancies. A well-conducted operation is often essential for cure. Collaboration with the primary care team is important for determining if and when surgery should be performed, and if performed, an operation must be done in accordance with well-established standards. The long-term consequences of surgery also need to be considered. Indications and objectives for a procedure vary. Providing education and developing and analyzing new research protocols that include aims relevant to surgery are key objectives of the Surgery Discipline of the Children's Oncology Group. The critical evaluation of emerging technologies to ensure safe, effective procedures is another key objective. Through research, education, and advancing technologies, the role of the pediatric surgeon in the multidisciplinary care of children with solid malignancies will continue to evolve.

Survival following complete resection of neuroblastoma in novel orthotopic rat xenograft model

Neuroblastoma accounts for 15% of pediatric cancer deaths, despite multimodal therapy including surgical resection. Current neuroblastoma rodent models are insufficient for studying the impact of surgery and combination treatments, largely due to the small size of mouse models. Human neuroblastoma SK-N-BE(2) cells were injected into the left adrenal gland of 5-6-week-old RNU homozygous nude rats. Rats were either monitored by MRI until humane endpoint was reached or after 5 weeks underwent operative tumor resection, followed by monitoring for recurrence and survival. Following neuroblastoma cell implantation, the majority of tumors grew to greater than 5000 mm3 within 5.5-6.5 weeks, meeting the humane endpoint. Surgical resection was successfully done in 8 out of 9 rats, extending survival following tumor implantation from a median of 42 days to 78 days (p < 0.005). Pathology was consistent with human neuroblastoma, showing small round blue cell tumors with Homer-Wright rosettes, high mitoses and karyorrhectic index, and strong PHOX2B staining. Thus, we have established a novel orthotopic xenograft rat model of neuroblastoma and demonstrated increased survival of rats after surgical tumor resection. This model can be used for the development of surgical techniques, such as the use of intraoperative molecular imaging or assessment of combination therapies that include surgery.

Identification of Pediatric Tumors Intraoperatively Using Indocyanine Green (ICG)

BACKGROUND

Fluorescence-guided surgery (FGS) with indocyanine green (ICG) is increasingly applied in pediatric surgical oncology. However, FGS has been mostly reported in case studies of liver or renal tumors. Applying novel technologies in pediatric surgical oncology is more challenging than in adult surgical oncology due to differences in tumor histology, biology, and fewer cases. No consensus exists on ICG-guided FGS for surgically managing pediatric solid tumors. Therefore, we reviewed the literature and discuss the limitations and prospects of FGS.

METHODS

Using PRISMA guidelines, we analyzed articles on ICG-guided FGS for childhood solid tumors. Case reports, opinion articles, and narrative reviews were excluded.

RESULTS

Of the 108 articles analyzed, 17 (14 retrospective and 3 prospective) met the inclusion criteria. Most (70.6%) studies used ICG to identify liver tumors, but the timing and dose of ICG administered varied. Intraoperative outcomes, sensitivity and specificity, were reported in 23.5% of studies. Fluorescence-guided liver resections resulted in negative margins in 90-100% of cases; lung metastasis was detected in 33% of the studies. In otolaryngologic malignancies, positive margins without fluorescence signal were reported in 25% of cases. Overall, ICG appeared effective and safe for lymph node sampling and nephron-sparing procedures.

CONCLUSIONS

Despite promising results from FGS, ICG use varies across the international pediatric surgical oncology community. Underreported intraoperative imaging outcomes and the diversity and rarity of childhood solid tumors hinder conclusive scientific evidence supporting adoption of ICG in pediatric surgical oncology. Further international collaborations are needed to study the applications and limitations of ICG in pediatric surgical oncology.

Fluorescent Probes for Imaging in Humans: Where Are We Now?

Optical imaging has become an indispensable technology in the clinic. The molecular design of cell-targeted and highly sensitive materials, the validation of specific disease biomarkers, and the rapid growth of clinically compatible instrumentation have altogether revolutionized the way we use optical imaging in clinical settings. One prime example is the application of cancer-targeted molecular imaging agents in both trials and routine clinical use to define the margins of tumors and to detect lesions that are "invisible" to the surgeons, leading to improved resection of malignant tissues without compromising viable structures. In this Perspective, we summarize some of the key research advances in chemistry, biology, and engineering that have accelerated the translation of optical imaging technologies for use in human patients. Finally, our paper comments on several research areas where further work will likely render the next generation of technologies for translational optical imaging.

Enhancing intraoperative tumor delineation with multispectral short-wave infrared fluorescence imaging and machine learning

SIGNIFICANCE

Fluorescence-guided surgery (FGS) provides specific real-time visualization of tumors, but intensity-based measurement of fluorescence is prone to errors. Multispectral imaging (MSI) in the short-wave infrared (SWIR) has the potential to improve tumor delineation by enabling machine-learning classification of pixels based on their spectral characteristics.

AIM

Determine whether MSI can be applied to FGS and combined with machine learning to provide a robust method for tumor visualization.

APPROACH

A multispectral SWIR fluorescence imaging device capable of collecting data from six spectral filters was constructed and deployed on neuroblastoma (NB) subcutaneous xenografts ( n = 6 ) after the injection of a NB-specific NIR-I fluorescent probe (Dinutuximab-IRDye800). We constructed image cubes representing fluorescence collected from ∼ 850 to 1450 nm and compared the performance of seven learning-based methods for pixel-by-pixel classification, including linear discriminant analysis, k -nearest neighbor classification, and a neural network.

RESULTS

The spectra of tumor and non-tumor tissue were subtly different and conserved between individuals. In classification, a combine principal component analysis and k -nearest-neighbor approach with area under curve normalization performed best, achieving 97.5% per-pixel classification accuracy (97.1%, 93.5%, and 99.2% for tumor, non-tumor tissue and background, respectively).

CONCLUSIONS

The development of dozens of new imaging agents provides a timely opportunity for multispectral SWIR imaging to revolutionize next-generation FGS.

Evaluation of Potential Targets for Fluorescence-Guided Surgery in Pediatric Ewing Sarcoma: A Preclinical Proof-of-Concept Study

Fluorescence-guided surgery (FGS), based on fluorescent tracers binding to tumor-specific biomarkers, could assist surgeons to achieve complete tumor resections. This study evaluated potential biomarkers for FGS in pediatric Ewing sarcoma (ES). Immunohistochemistry (IHC) was performed to assess CD99, CXCR4, CD117, NPY-R-Y1, and IGF-1R expression in ES biopsies and resection specimens. LINGO-1 and GD2 evaluation did not work on the acquired tissue. Based on the immunoreactive scores, anti-CD99 and anti-CD117 were evaluated for binding specificity using flow cytometry and immunofluorescence microscopy. Anti-GD2, a tracer in the developmental phase, was also tested. These three tracers were topically applied to a freshly resected ES tumor and adjacent healthy tissue. IHC demonstrated moderate/strong CD99 and CD117 expression in ES tumor samples, while adjacent healthy tissue had limited expression. Flow cytometry and immunofluorescence microscopy confirmed high CD99 expression, along with low/moderate CD117 and low GD2 expression, in ES cell lines. Topical anti-CD99 and anti-GD2 application on ES tumor showed fluorescence, while anti-CD117 did not show fluorescence for this patient. In conclusion, CD99-targeting tracers hold promise for FGS of ES. CD117 and GD2 tracers could be potential alternatives. The next step towards development of ES-specific FGS tracers could be ex vivo topical application experiments on a large cohort of ES patients.

Evaluating the Development Status of Fluorescence-Guided Surgery (FGS) in Pediatric Surgery Using the Idea, Development, Exploration, Assessment, and Long-Term Study (IDEAL) Framework

Fluorescence-guided surgery (FGS) is used in many pediatric subspecialties but there are currently no standard guidelines or outcome data. We aimed to assess the current status of FGS in pediatrics using the Idea, Development, Exploration, Assessment, and Long-term study (IDEAL) framework. Clinical papers on FGS in children published from January 2000 to December 2022 were systematically reviewed. The stage of research development was measured considering seven fields of application: biliary tree imaging, vascular perfusion for gastrointestinal procedures, lymphatic flow imaging, tumor resection, urogenital surgery, plastic surgery, and miscellaneous procedures. Fifty-nine articles were selected. For each field of application, the overall IDEAL stage was determined to be 2a for biliary tree imaging (10 publications, 102 cases), 1 for vascular perfusion for gastrointestinal procedures (8 publications, 28 cases), 1 for lymphatic flow imaging (12 publications, 33 cases), 2a for tumor resection (20 publications, 238 cases), 2a for urogenital surgery (9 publications, 197 cases), and 1-2a for plastic surgery (4 publications, 26 cases). One report did not belong to any categories. FGS in children is still in an early phase of adoption and development. We recommend using the IDEAL framework as a guide and suggest developing multicenter studies to define the standard guidelines, effectiveness, and outcomes.

Immunohistochemical Evaluation of Candidate Biomarkers for Fluorescence-Guided Surgery of Myxofibrosarcoma Using an Objective Scoring Method

INTRODUCTION

Myxofibrosarcoma (MFS) is the most common soft-tissue sarcoma subtype in elderly patients. Local recurrence (LR) remains a major concern as the lack of intraoperative guidance and an infiltrative growth pattern with long, slender tails hamper surgeons' ability to achieve adequate resection margins for MFS. Fluorescence-guided surgery (FGS) could overcome this concern by delineating tumor tissue during surgery. One of the most important steps to successful FGS is to define a tumor-specific biomarker that is highly overexpressed in tumor tissue while low or absent in adjacent healthy tissue. The aim of this study is to evaluate the expression of eight previously selected promising biomarkers for FGS in MFS tissue samples with adjacent healthy tissue using immunohistochemistry (IHC).

METHODS

The following eight biomarkers were stained in seventeen paraffin-embedded MFS samples: tumor endothelial marker-1 (TEM-1, also known as endosialin/CD248), vascular endothelial growth factor receptor-1 (VEGFR-1, also known as Flt-1), vascular endothelial growth factor receptor-2 (VEGFR-2, also known as Flk1), vascular endothelial growth factor-A (VEGF-A), epidermal growth factor receptor (EGFR), insulin-like growth factor-1 receptor (IGF-1R), platelet derived growth factor receptor-α (PDGFR-α), and cluster of differentiation 40 (CD40, also known as TNFRSF5). A pathologist specializing in sarcoma annotated the margin between the tumor and adjacent healthy tissue in each MFS tissue sample. Subsequently, we used an objective IHC scoring method to assess and compare the difference in staining intensity between the tumor and adjacent healthy tissue, which is crucial for the use of FGS.

RESULTS

TEM-1, VEGF-A, and PDGFR-α stained all MFS tumors, while the other biomarkers did not show expression in all MFS tumors. Ultimately, TEM-1 was identified as the most suitable biomarker for FGS in MFS based on higher tumor-to-background (TBR) staining intensity compared to VEGF-A and PDGFR-α, regardless of preoperative therapy.

CONCLUSION

TEM-1-targeted FGS tracers should be further investigated to optimize MFS treatment.

Biologicals as theranostic vehicles in paediatric oncology

Biologicals, such as antibodies or antibody-fragments e.g. nanobodies, have changed the landscape of cancer therapy and can be used in combination with traditional cancer treatments. They have been demonstrated to be excellent vehicles for molecular imaging. Several biologicals for nuclear imaging of adult cancer may be used in combination with (nuclear) therapy. Though it's great potential, molecular imaging using biologicals is rarely applied in paediatric oncology. This paper describes the current status of biologicals as radiopharmaceuticals for childhood cancer. Furthermore, the importance and potential for developing additional biological theranostics as opportunity to image and treat childhood cancer is discussed.

Novel Treatments and Technologies Applied to the Cure of Neuroblastoma

Neuroblastoma (NB) is the most common extracranial solid tumour in childhood, accounting for approximately 15% of all cancer-related deaths in the paediatric population1. It is characterised by heterogeneous clinical behaviour in neonates and often adverse outcomes in toddlers. The overall survival of children with high-risk disease is around 40-50% despite the aggressive treatment protocols consisting of intensive chemotherapy, surgery, radiation therapy and hematopoietic stem cell transplantation2,3. There is an ongoing research effort to increase NB's cellular and molecular biology knowledge to translate essential findings into novel treatment strategies. This review aims to address new therapeutic modalities emerging from preclinical studies offering a unique translational opportunity for NB treatment.

Targeting Glycans and Heavily Glycosylated Proteins for Tumor Imaging

Simple Summary

Distinguishing malignancy from healthy tissue is essential for oncologic surgery. Targeted imaging during an operation aids the surgeon to operate better. The present tracers for detecting cancer are directed against proteins that are overexpressed on the membrane of tumor cells. This review evaluates the use of tumor-associated sugar molecules as an alternative for proteins to image cancer tissue. These sugar molecules are present as glycans on glycosylated membrane proteins and glycolipids. Due to their location and large numbers per cell, these sugar molecules might be better targets for tumor imaging than proteins.

Abstract

Real-time tumor imaging techniques are increasingly used in oncological surgery, but still need to be supplemented with novel targeted tracers, providing specific tumor tissue detection based on intra-tumoral processes or protein expression. To maximize tumor/non-tumor contrast, targets should be highly and homogenously expressed on tumor tissue only, preferably from the earliest developmental stage onward. Unfortunately, most evaluated tumor-associated proteins appear not to meet all of these criteria. Thus, the quest for ideal targets continues. Aberrant glycosylation of proteins and lipids is a fundamental hallmark of almost all cancer types and contributes to tumor progression. Additionally, overexpression of glycoproteins that carry aberrant glycans, such as mucins and proteoglycans, is observed. Selected tumor-associated glyco-antigens are abundantly expressed and could, thus, be ideal candidates for targeted tumor imaging. Nevertheless, glycan-based tumor imaging is still in its infancy. In this review, we highlight the potential of glycans, and heavily glycosylated proteoglycans and mucins as targets for multimodal tumor imaging by discussing the preclinical and clinical accomplishments within this field. Additionally, we describe the major advantages and limitations of targeting glycans compared to cancer-associated proteins. Lastly, by providing a brief overview of the most attractive tumor-associated glycans and glycosylated proteins in association with their respective tumor types, we set out the way for implementing glycan-based imaging in a clinical practice.