A 3E8.scFv.Cys-IR800 Conjugate Targeting TAG-72 in an Orthotopic Colorectal Cancer Model

Development of Polar BODIPY-Tetrazines for Rapid Pretargeted Fluorescence Imaging

Polar BODIPY-tetrazine dyes were developed and clicked in vivo to a preaccumulated trans-cyclooctene-modified anti-TAG72 monoclonal antibody CC49 (CC49-TCO). The in vivo click performance was evaluated using an in-house developed ex vivo blocking assay. All tested polar BODIPY structures exhibited excellent in vivo binding, confirming that the turn-on tetrazine dyes successfully clicked in vivo to pretargeted CC49-TCO. Fluorescence imaging showed high tumor-to-muscle ratios of 4:1. This proof-of-concept study indicates that the pretargeting concept based on turn-on probes could be used for cancer treatments, such as photodynamic or -thermal therapy.

A Concept for Preoperative and Intraoperative Molecular Imaging and Detection for Assessing Extent of Disease of Solid Tumors

The authors propose a concept of "systems engineering," the approach to assessing the extent of diseased tissue (EODT) in solid tumors. We modeled the proof of this concept based on our clinical experience with colorectal carcinoma (CRC) and gastrinoma that included short and long-term survival data of CRC patients. This concept, applicable to various solid tumors, combines resources from surgery, nuclear medicine, radiology, pathology, and oncology needed for preoperative and intraoperative assessments of a patient's EODT. The concept begins with a patient presenting with biopsy-proven cancer. An appropriate preferential locator (PL) is a molecule that preferentially binds to a cancer-related molecular target (i.e., tumor marker) lacking in non-malignant tissue and is the essential element. Detecting the PL after an intravenous injection requires the PL labeling with an appropriate tracer radionuclide, a fluoroprobe, or both. Preoperative imaging of the tracer's signal requires molecular imaging modalities alone or in combination with computerized tomography (CT). These include positron emission tomography (PET), PET/CT, single-photon emission computed tomography (SPECT), SPECT/CT for preoperative imaging, gamma cameras for intraoperative imaging, and gamma-detecting probes for precise localization. Similarly, fluorescent-labeled PLs require appropriate cameras and probes. This approach provides the surgeon with real-time information needed for R0 resection.

Production and characterization of a camelid single domain anti-CD22 antibody conjugated to DM1

Antibody drug conjugates (ADCs) with twelve FDA approved drugs, known as a novel category of anti-neoplastic treatment created to merge the monoclonal antibody specificity with cytotoxicity effect of chemotherapy. However, despite many undeniable advantages, ADCs face certain problems, including insufficient internalization after binding, complex structures and large size of full antibodies especially in targeting of solid tumors. Camelid single domain antibody fragments (Nanobody®) offer solutions to this challenge by providing nanoscale size, high solubility and excellent stability, recombinant expression in bacteria, in vivo enhanced tissue penetration, and conjugation advantages. Here, an anti-human CD22 Nanobody was expressed in E.coli cells and conjugated to Mertansine (DM1) as a cytotoxic payload. The anti-CD22 Nanobody was expressed and purified by Ni-NTA resin. DM1 conjugated anti-CD22 Nanobody was generated by conjugation of SMCC-DM1 to Nanobody lysine groups. The conjugates were characterized using SDS-PAGE and Capillary electrophoresis (CE-SDS), RP-HPLC, and MALDI-TOF mass spectrometry. Additionally, flow cytometry analysis and a competition ELISA were carried out for binding evaluation. Finally, cytotoxicity of conjugates on Raji and Jurkat cell lines was assessed. The drug-to-antibody ratio (DAR) of conjugates was calculated 2.04 using UV spectrometry. SDS-PAGE, CE-SDS, HPLC, and mass spectrometry confirmed conjugation of DM1 to the Nanobody. The obtained results showed the anti-CD22 Nanobody cytotoxicity was enhanced almost 80% by conjugation with DM1. The binding of conjugates was similar to the non-conjugated anti-CD22 Nanobody in flow cytometry experiments. Concludingly, this study successfully suggest that the DM1 conjugated anti-CD22 Nanobody can be used as a novel tumor specific drug delivery system.

Smaller size packs a stronger punch - Recent advances in small antibody fragments targeting tumour-associated carbohydrate antigens

Attached to proteins, lipids, or forming long, complex chains, glycans represent the most versatile post-translational modification in nature and surround all human cells. Unique glycan structures are monitored by the immune system and differentiate self from non-self and healthy from malignant cells. Aberrant glycosylations, termed tumour-associated carbohydrate antigens (TACAs), are a hallmark of cancer and are correlated with all aspects of cancer biology. Therefore, TACAs represent attractive targets for monoclonal antibodies for cancer diagnosis and therapy. However, due to the thick and dense glycocalyx as well as the tumour micro-environment, conventional antibodies often suffer from restricted access and limited effectiveness in vivo. To overcome this issue, many small antibody fragments have come forth, showing similar affinity with better efficiency than their full-length counterparts. Here we review small antibody fragments against specific glycans on tumour cells and highlight their advantages over conventional antibodies.

Optimized immobilization of single chain variable fragment antibody onto non-toxic fluorescent nanoparticles for efficient preparation of a bioprobe

Single-chain variable fragment antibody (scFv) is a small molecular weight antibody that can be used for both therapeutic and diagnostic purposes. To visualize the interaction with the target biomolecules, scFv must be labeled with fluorescent molecules. In this study, to achieve the efficient labeling of scFv, we developed scFv-fluorescent nanoparticle conjugates to utilize scFv as bioprobes. As fluorescent carriers, cadmium-free ZnS-AgInS2/ZnS core/shell nanoparticles were used, and scFv was immobilized onto the nanoparticles via the interaction of nickel ions on nitrilotriacetic acid and hexahistidine (His-tag) fused with scFv. UV-Vis, fluorescence spectra, NMR, and dynamic laser scattering were used to characterize the scFv immobilized fluorescent nanoparticles (scFv-FNPs). The amounts of scFv on FNPs were controlled by the concentration of scFv. The scFv-FNPs that were prepared were non-toxic and selectively bound to cancer cells. The scFv-FNPs could be used as bioanalytical tools, and the immobilization method described here is a promising method for labeling biomolecules with the His-tag.

Near-Infrared Fluorescence Imaging of EGFR-Overexpressing Tumors in the Mouse Xenograft Model Using scFv-IRDye800CW and Cetuximab-IRDye800CW

EGFR (epidermal growth factor receptor) is overexpressed in a variety of human cancers (including squamous cell carcinoma of head and neck, colon cancer, and some breast cancers) and therefore is regarded as an ideal target for cancer therapy or imaging purposes. In the current study, we produced a scFv-based near-infrared probe (called cet.Hum.scFv-IRDye-800CW) and evaluated its ability in recognizing and imaging of EGFR-overexpressing tumors in a mouse model. Like the molecular probe consisting of its parental antibody (cetuximab, an FDA-approved monoclonal antibody) and IRD800CW, cet.Hum.scFv-IRDye-800CW was able to recognize EGFR-overexpressing tumors in mice. cet.Hum.scFv-IRDye-800CW was found to be superior to the cetuximab-based probe in imaging of mouse tumors. The tumor-to-background ratio and blood clearance rate were higher when cet.Hum.scFv-IRDye-800CW was used as an imaging probe.

Fluorescence Molecular Targeting of Colon Cancer to Visualize the Invisible

Colorectal cancer (CRC) is a common cause of cancer and cancer-related death. Surgery is the only curative modality. Fluorescence-enhanced visualization of CRC with targeted fluorescent probes that can delineate boundaries and target tumor-specific biomarkers can increase rates of curative resection. Approaches to enhancing visualization of the tumor-to-normal tissue interface are active areas of investigation. Nonspecific dyes are the most-used approach, but tumor-specific targeting agents are progressing in clinical trials. The present narrative review describes the principles of fluorescence targeting of CRC for diagnosis and fluorescence-guided surgery with molecular biomarkers for preclinical or clinical evaluation.

Anti-glycan antibodies: roles in human disease

Carbohydrate-binding antibodies play diverse and critical roles in human health. Endogenous carbohydrate-binding antibodies that recognize bacterial, fungal, and other microbial carbohydrates prevent systemic infections and help maintain microbiome homeostasis. Anti-glycan antibodies can have both beneficial and detrimental effects. For example, alloantibodies to ABO blood group carbohydrates can help reduce the spread of some infectious diseases, but they also impose limitations for blood transfusions. Antibodies that recognize self-glycans can contribute to autoimmune diseases, such as Guillain-Barre syndrome. In addition to endogenous antibodies that arise through natural processes, a variety of vaccines induce anti-glycan antibodies as a primary mechanism of protection. Some examples of approved carbohydrate-based vaccines that have had a major impact on human health are against pneumococcus, Haemophilus influeanza type b, and Neisseria meningitidis. Monoclonal antibodies specifically targeting pathogen associated or tumor associated carbohydrate antigens (TACAs) are used clinically for both diagnostic and therapeutic purposes. This review aims to highlight some of the well-studied and critically important applications of anti-carbohydrate antibodies.

Advances in Imaging Modalities and Contrast Agents for the Early Diagnosis of Colorectal Cancer

Colorectal cancer is one of the most common gastrointestinal cancers worldwide. The mortality rate of colorectal cancer has declined by more than 20% due to the rapid development of early diagnostic techniques and effective treatment. At present, there are many diagnostic modalities available for the evaluation of colorectal cancer, such as the carcinoembryonic antigen test, the fecal occult blood test, endoscopy, X-ray barium meal, computed tomography, magnetic resonance imaging, and radionuclide examination. Sensitive and specific imaging modalities have played an increasingly important role in the diagnosis of colorectal cancer following the rapid development of novel contrast agents. This review discusses the applications and challenges of different imaging techniques and contrast agents applied to detect colorectal cancer, for the purpose of the early diagnosis and treatment of patients with colorectal cancer.

Unique Benefits of Tumor-Specific Nanobodies for Fluorescence Guided Surgery

Tumor-specific fluorescence labeling is promising for real-time visualization of solid malignancies during surgery. There are a number of technologies to confer tumor-specific fluorescence. Antibodies have traditionally been used due to their versatility in modifications; however, their large size hampers efficient fluorophore delivery. Nanobodies are a novel class of molecules, derived from camelid heavy-chain only antibodies, that have shown promise for tumor-specific fluorescence labeling. Nanobodies are ten times smaller than standard antibodies, while maintaining antigen-binding capacity and have advantageous features, including rapidity of tumor labeling, that are reviewed in the present report. The present report reviews special considerations needed in developing nanobody probes, the status of current literature on the use of nanobody probes in fluorescence guided surgery, and potential challenges to be addressed for clinical translation.

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.

Cyanine Conjugate-Based Biomedical Imaging Probes

Cyanine is a class of fluorescent dye with meritorious fluorescence properties and has motivated numerous researchers to explore its imaging capabilities by miscellaneous structural modification and functionalization strategies. The covalent conjugation with other functional molecules represents a distinctive design strategy and has shown immense potential in both basic and clinical research. This review article summarizes recent achievements in cyanine conjugate-based probes for biomedical imaging. Particular attention is paid to the conjugation with targeting warheads and other contrast agents for targeted fluorescence imaging and multimodal imaging, respectively. Additionally, their clinical potential in cancer diagnostics is highlighted and some concurrent impediments for clinical translation are discussed.

Advances in image enhancement for sarcoma surgery

The recurrence rate of soft tissue and bone sarcomas strongly correlates to the status of the surgical margin after excision, yet excessive removal of tissue may lead to distinct, otherwise avoidable morbidity. Therefore, adequate margination of sarcomas both pre- and intra-operatively is a clinical necessity that has not yet fully been met. Current guidance for soft-tissue sarcomas recommends an ultrasound scan followed by magnetic resonance imaging (MRI). For bone sarcomas, two plane radiographs are required, followed similarly by an MRI scan. The introduction of more precise imaging modalities may reduce the morbidity associated with sarcoma surgery; the PET-CT and PET-MRI approaches in particular demonstrating high clinical efficacy. Despite advancements in the accuracy in pre-operative imaging, translation of an image to surgical margins is difficult, regularly resulting in wider resection margins than required. For soft tissue sarcomas there is currently no standard technique for image guided resections, while for bone sarcomas fluoroscopy may be used, however margins are not easily discernible during the surgical procedure. Near infra-red (NIR) fluorescence guided surgery offers an intra-operative modality through which complete tumour resection with adequate tumour-free margins may be achieved, while simultaneously minimising surgical morbidity. NIR imaging presents a potentially valuable adjunct to sarcoma surgery. Early reports indicate that it may be able to provide the surgeon with helpful information on anatomy, perfusion, lymphatic drainage, tumour margins and metastases. The use of NIR fluorochromes have also been demonstrated to be well tolerated by patients. However, prior to widespread implementation, studies related to cost-effectiveness and the development of protocols are essential. Nevertheless, NIR imaging may become ubiquitous in the future, carrying the potential to transform the surgical management of sarcoma.

Emerging Fluorescent Molecular Tracers to Guide Intra-Operative Surgical Decision-Making

Fluorescence imaging is an emerging technology that can provide real-time information about the operating field during cancer surgery. Non-specific fluorescent agents, used for the assessment of blood flow and sentinel lymph node detection, have so far dominated this field. However, over the last decade, several clinical studies have demonstrated the great potential of targeted fluorescent tracers to visualize tumor lesions in a more specific way. This has led to an exponential growth in the development of novel molecular fluorescent contrast agents. In this review, the design of fluorescent molecular tracers will be discussed, with particular attention for agents and approaches that are of interest for clinical translation.

Emerging applications of upconverting nanoparticles in intestinal infection and colorectal cancer

Colorectal cancer is the abnormal growth of cells in colon or rectum. Recent findings have acknowledged the role of bacterial infection and chronic inflammation in colorectal cancer initiation and progression. In order to detect and treat precancerous lesions, new tools are required, which may help to prevent or identify colorectal cancer at an early stage. To date, several different screening tests are available, including endoscopy, stool-based blood tests, and radiology-based tests. However, these analyses either lack sensitivity or are of an invasive nature. The use of fluorescently labeled probes can increase the detection sensitivity. However, autofluorescence, photobleaching, and photodamage are commonly encountered problems with fluorescence imaging. Upconverting nanoparticles (UCNPs) are recently developed lanthanide-doped nanocrystals that can be used as light-triggered luminescent probes and in drug delivery systems. In this review, we comprehensively summarize the recent developments and address future prospects of UCNP-based applications for diagnostics and therapeutic approaches associated with intestinal infection and colorectal cancer.

Serum tumor-associated glycoprotein 72, a helpful predictor of lymph nodes invasion in esophagogastric junction adenocarcinoma

Disruption of cell-cell junction and adhesion to vessels are crucial steps in tumor metastasis. Tumor-associated glycoprotein 72 (TAG-72) is a crucial membrane mucin in gastroesophageal mucosa for microenvironment contact with cells. Thus, the TAG-72 value may be an indicator of the malignant involvement of lymph nodes in esophagogastric junction adenocarcinoma (EGAC) patients. Of the 183 patients suspected as gastroesophageal neoplasms, 129 were subsequently diagnosed as EGAC, and 54 were subsequently diagnosed as benign gastroesophageal diseases by imageological or/and histological examination. After we obtained preoperative serum TAG-72 values, the relationship between serum TAG-72 and lymphatic metastasis status, extent of invaded lymph nodes and clinical stage was tested using Spearman correlation analysis and χ2 tests. Compared with those in patients who suffered either benign gastroesophageal diseases or preinvasive carcinoma, the median serum TAG-72 values were statistically higher in EGAC patients with positive lymph nodes (Kruskal-Wallis test; P < 0.001). Serum TAG-72 values were significantly correlated with Lymph Node Ratio (LNR) (Spearman correlation; P < 0.001). Using corresponding ROC (95% CI = 0.621-0.783, P < 0.0001), serum TAG-72 values with an optimal cut-off (2.2 kU/mL) showed a sensitivity of 0.632 and a specificity of 0.690 for predicting malignant lymph node involvement in EGAC. These results suggest that the serum TAG-72 value is a clinically helpful predictor of lymph nodes invasion in resectable EGAC.

Linker engineering in anti-TAG-72 antibody fragments optimizes biophysical properties, serum half-life, and high-specificity tumor imaging

Antibody (Ab) fragments have great clinical potential as cancer therapeutics and diagnostics. Their small size allows for fast clearance from blood, low immunoreactivity, better tumor penetration, and simpler engineering and production. The smallest fragment derived from a full-length IgG that retains binding to its antigen, the single-chain variable fragment (scF_V), is engineered by fusing the variable light and variable heavy domains with a peptide linker. Along with switching the domain orientation, altering the length and amino acid sequence of the linker can significantly affect scF_V binding, stability, quaternary structure, and other biophysical properties. Comprehensive studies of these attributes in a single scaffold have not been reported, making design and optimization of Ab fragments challenging. Here, we constructed libraries of 3E8, an Ab specific to tumor-associated glycoprotein 72 (TAG-72), a mucinous glycoprotein overexpressed in 80% of adenocarcinomas. We cloned, expressed, and characterized scF_Vs, diabodies, and higher-order multimer constructs with varying linker compositions, linker lengths, and domain orientations. These constructs dramatically differed in their oligomeric states and stabilities, not only because of linker and orientation but also related to the purification method. For example, protein L-purified constructs tended to have broader distributions and higher oligomeric states than has been reported previously. From this library, we selected an optimal construct, 3E8.G₄S, for biodistribution and pharmacokinetic studies and in vivo xenograft mouse PET imaging. These studies revealed significant tumor targeting of 3E8.G₄S with a tumor-to-background ratio of 29:1. These analyses validated 3E8.G₄S as a fast, accurate, and specific tumor-imaging agent.

Fluorescence-Guided Surgery

Surgical resection of cancer remains an important treatment modality. Despite advances in preoperative imaging, surgery itself is primarily guided by the surgeon’s ability to locate pathology with conventional white light imaging. Fluorescence-guided surgery (FGS) can be used to define tumor location and margins during the procedure. Intraoperative visualization of tumors may not only allow more complete resections but also improve safety by avoiding unnecessary damage to normal tissue which can also reduce operative time and decrease the need for second-look surgeries. A number of new FGS imaging probes have recently been developed, complementing a small but useful number of existing probes. In this review, we describe current and new fluorescent probes that may assist FGS.