Fluorescence endoscopic detection of murine colitis-associated colon cancer by topically applied enzymatically rapid-activatable probe

Fluorescent imaging probes for in vivo ovarian cancer targeted detection and surgery

Ovarian cancer is the most lethal gynecological cancer, with a survival rate of approximately 40% at five years from the diagno. The first-line treatment consists of cytoreductive surgery combined with chemotherapy (platinum- and taxane-based drugs). To date, the main prognostic factor is related to the complete surgical resection of tumor lesions, including occult micrometastases. The presence of minimal residual diseases not detected by visual inspection and palpation during surgery significantly increases the risk of disease relapse. Intraoperative fluorescence imaging systems have the potential to improve surgical outcomes. Fluorescent tracers administered to the patient may support surgeons for better real-time visualization of tumor lesions during cytoreductive procedures. In the last decade, consistent with the discovery of an increasing number of ovarian cancer-specific targets, a wide range of fluorescent agents were identified to be employed for intraoperatively detecting ovarian cancer. Here, we present a collection of fluorescent probes designed and developed for fluorescence-guided ovarian cancer surgery. Original articles published between 2011 and November 2022 focusing on fluorescent probes, currently under preclinical and clinical investigation, were searched in PubMed. The keywords used were targeted detection, ovarian cancer, fluorescent probe, near-infrared fluorescence, fluorescence-guided surgery, and intraoperative imaging. All identified papers were English-language full-text papers, and probes were classified based on the location of the biological target: intracellular, membrane, and extracellular.

New Technologies in Digestive Endoscopy for Ulcerative Colitis Patients

Ulcerative colitis (UC) is a chronic inflammatory bowel disease primarily affecting the colon and rectum. Endoscopy plays a crucial role in the diagnosis and management of UC. Recent advancements in endoscopic technology, including chromoendoscopy, confocal laser endomicroscopy, endocytoscopy and the use of artificial intelligence, have revolutionized the assessment and treatment of UC patients. These innovative techniques enable early detection of dysplasia and cancer, more precise characterization of disease extent and severity and more targeted biopsies, leading to improved diagnosis and disease monitoring. Furthermore, these advancements have significant implications for therapeutic decision making, empowering clinicians to carefully consider a range of treatment options, including pharmacological therapies, endoscopic interventions and surgical approaches. In this review, we provide an overview of the latest endoscopic technologies and their applications for diagnosing and monitoring UC. We also discuss their impact on treatment decision making, highlighting the potential benefits and limitations of each technique.

An oral ratiometric NIR-II fluorescent probe for reliable monitoring of gastrointestinal diseases in vivo

Early monitoring of gastrointestinal diseases via orally delivered NIR-II ratiometric fluorescent probes represents a promising noninvasive diagnostic modality, but is challenging due to the limitation of harsh digestive environment. Here, we report a single-component NIR-II ratiometric molecular nanoprobe (LC-1250 NP) to monitor gastrointestinal disease with high specificity to its biomarker H₂O₂ via oral administration. LC-1250 NP displays stable fluorescence in the channel of 1250 long-pass (F_1250LP) before and after the gastrointestinal disease detection as the reference, while it presents significantly enhanced fluorescence signal in the response channel of 1150 nm short-pass (F_1150SP) in diseased gastrointestinal environment due to the intramolecular cyclization of LC-1250 molecules activated by H₂O₂. The fluorescence ratio (F_1150SP/F_1250LP) increases linearly with the concentration of H₂O₂ with a low detection limit of 20 nM. Therefore, when delivered orally, LC-1250 NP can accurately map the diseased areas and surmount the false-positive interference from biological heterogeneity by NIR-II ratiometric fluorescence imaging, providing sensitive and reliable evaluation for the progress of gastroenteritis.

5-Fluorouracil crystal-incorporated, pH-responsive, and release-modulating PLGA/Eudragit FS hybrid microparticles for local colorectal cancer-targeted chemotherapy

5-Fluorouracil (5-FU) is a widely used chemotherapeutic agent for colorectal cancer (CRC) owing to its potent anticancer effects. However, severe systemic side effects and poor drug accumulation in the CRC tissues limit its efficacy. This study aimed to develop 5-FU crystal-incorporated, pH-responsive, and release-modulating poly(d,l-lactide-co-glycolide)/Eudragit FS hybrid microparticles (5FU-EPMPs) for the local CRC-targeted chemotherapy. Approximately 150 μm 5FU-EPMPs were fabricated via the S/O/W emulsion solvent evaporation method, with 7.93 ± 0.24% and 87.23 ± 2.64% 5-FU loading and encapsulation efficiencies, respectively. Drug release profiles in a simulated pH environment of the gastrointestinal tract revealed that premature 5-FU release in the stomach and small intestine was prevented, thereby minimizing systemic 5-FU absorption. After reaching the colon, 5-FU was continuously released for >15 h, allowing long-term exposure of CRC tissues to sufficient 5-FU concentrations. Furthermore, in a CRC mouse model, the 5FU-EPMPs showed potent inhibition of tumor growth without signs of systemic toxicity. Thus, the 5FU-EPMPs represent a promising drug delivery system for local CRC-targeted chemotherapy.

A Novel Imaging Technique for The On-site Assessment of Renal Biopsy Specimens

When performing renal biopsy, it is necessary to identify the cortex, where glomeruli are exclusively distributed, to ensure the quality of the specimen for histological diagnosis. However, conventional methods using a stereomicroscope or magnifying lens often fail to clarify the quality of the specimen. We have established a fluorescent-based imaging technique for the on-site assessment of renal biopsy specimens. The fluorescent images can be easily obtained by adding an optical filter to the microscope and with a short incubation of an activatable fluorescent probe. This novel imaging technique can be applied to renal biopsy specimens for distinguishing the renal cortex.

The Dual-Targeted Peptide Conjugated Probe for Depicting Residual Nasopharyngeal Carcinoma and Guiding Surgery

Detecting residual nasopharyngeal carcinoma (rNPC) can be difficult because of the coexistence of occult tumours and post-chemoradiation changes, which poses a challenge for both radiologists and surgeons using current imaging methods. Currently, molecular imaging that precisely targets and visualises particular biomarkers in tumours may exceed the specificity and sensitivity of traditional imaging techniques, providing the potential to distinguish tumours from non-neoplastic lesions. Here, we synthesised a HER2/SR-BI-targeted tracer to efficiently position NPC and guide surgery in living mice. This bispecific tracer contained the following two parts: IRDye 800 CW, as an imaging reagent for both optical and optoacoustic imaging, and a fusion peptide (FY-35), as the targeting reagent. Both in vitro and in vivo tests demonstrated that the tracer had higher accumulation and longer retention (up to 48 h) in tumours than a single-targeted probe, and realised sensitive detection of tumours with a minimum size of 3.9 mm. By visualising the vascular network via a customised handheld optoacoustic scan, our intraoperative fluorescence molecular imaging system provides accurate guidance for intraoperative tumour resection. Integrating the advantages of both optical and optoacoustic scanning in an intraoperative image-guided system, this method holds promise for depicting rNPC and guiding salvage surgery.

Molecular Endoscopy for the Diagnosis and Therapeutic Monitoring of Colorectal Cancer

Colorectal cancer (CRC) is one of the leading causes of cancer related death in the western world. Its successful treatment requires early detection and removal of precursor lesions as well as individualized treatment of advanced disease. During recent years, molecular imaging techniques have shown promising results to improve current clinical practice. For instance, molecular endoscopy resulted in higher detection rates of precursors in comparison to conventional endoscopy in preclinical and clinical studies. Molecular confocal endomicroscopy allowed a further classification of suspect lesions as well as the prediction and monitoring of the therapeutic response. In this review, we summarize recent achievements for molecular imaging of CRC in preclinical studies, initial clinical trials and the remaining challenges for future translation into clinical practice.

Optical Modalities for Research, Diagnosis, and Treatment of Stroke and the Consequent Brain Injuries

Stroke is the second most common cause of death and third most common cause of disability worldwide. Therefore, it is an important disease from a medical standpoint. For this reason, various studies have developed diagnostic and therapeutic techniques for stroke. Among them, developments and applications of optical modalities are being extensively studied. In this article, we explored three important optical modalities for research, diagnostic, and therapeutics for stroke and the brain injuries related to it: (1) photochemical thrombosis to investigate stroke animal models; (2) optical imaging techniques for in vivo preclinical studies on stroke; and (3) optical neurostimulation based therapy for stroke. We believe that an exploration and an analysis of previous studies will help us proceed from research to clinical applications of optical modalities for research, diagnosis, and treatment of stroke.

Evolution and New Horizons of Endoscopy in Inflammatory Bowel Diseases

Endoscopy is the mainstay of inflammatory bowel disease (IBD) evaluation and the pillar of colorectal cancer surveillance. Endoscopic equipment, both hardware and software, are advancing at an incredible pace. Virtual chromoendoscopy is now widely available, allowing the detection of subtle inflammatory changes, thus reducing the gap between endoscopic and histologic assessment. The progress in the field of artificial intelligence (AI) has been remarkable, and numerous applications are now in an advanced stage of development. Computer-aided diagnosis (CAD) systems are likely to reshape most of the evaluations that are now prerogative of human endoscopists. Furthermore, sophisticated tools such as endocytoscopy and probe-based confocal laser endomicroscopy (pCLE) are enhancing our assessment of inflammation and dysplasia. Finally, pCLE combined with molecular labeling could pave the way to a new paradigm of personalized medicine. This review aims to summarize the main changes that occurred in the field of IBD endoscopy and to explore the most promising novelties.

Rapid visualization of mammary gland tumor lesions of dogs using the enzyme-activated fluorogenic probe; γ-glutamyl hydroxymethyl rhodamine green

Since gamma-glutamyl transpeptidase (GGT) is highly and locally expressed in human breast cancer, a GGT-enzymatically activatable fluorescent probe, gamma-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG), has been developed to detect the human breast cancer area with high performance. In this study, GGT expression and the efficacy of gGlu-HMRG on visualization were investigated in canine mammary gland tumors (MGT). Seventeen non-fixed fresh-frozen MGT specimens and each peritumoral control tissue were utilized. The GGT mRNA levels were highly observed in the tumor specimens compared with the control. GGT immunostaining was mostly observed on the cell membrane and cytosol of the alveolar and duct mammary epithelium of MGT tissues. These signals were strongly positive in several cases while they were mild to not observed in other cases. When gGlu-HMRG solution was dropped to the non-fixed tissue pieces of MGT or control tissues, the fluorescence intensities (FIs) were measured using Maestro in-vivo imaging device. FIs in MGT tissues were significantly higher than each control tissue 20 min after treatment. Based on Youden index method said that the maximum sensitivity and specificity of FI was 82.4% and 82.4%. These findings suggest that GGT is highly expressed in several MGTs in dogs and gGlu-HMRG could visualize at least a part of MGT tissues in dogs. Nevertheless, it should be needed to assess the false-negative areas more carefully in canine than human cases.

Activatable molecular probes for fluorescence-guided surgery, endoscopy and tissue biopsy

The real-time, dynamic optical visualization of lesions and margins ensures not only complete resection of the malignant tissues but also better preservation of the vital organs/tissues during surgical procedures. Most imaging probes with an "always-on" signal encounter high background noise due to their non-specific accumulation in normal tissues. By contrast, activatable molecular probes only "turn on" their signals upon reaction with the targeted biomolecules that are overexpressed in malignant cells, offering high target-to-background ratios with high specificity and sensitivity. This review summarizes the recent progress of activatable molecular probes in surgical imaging and diagnosis. The design principle and mechanism of activatable molecular probes are discussed, followed by specific emphasis on applications ranging from fluorescence-guided surgery to endoscopy and tissue biopsy. Finally, potential challenges and perspectives in the field of activatable molecular probe-enabled surgical imaging are discussed.

Recent Advances in Molecular Imaging of Colorectal Tumors

BACKGROUND

Recent endoscopic studies have revealed that small colorectal tumors are often overlooked during colonoscopy, indicating that more sensitive detection methods are needed.

SUMMARY

Molecular imaging has received considerable attention as a new endoscopic technique with high sensitivity. It generally employs a fluorescence-labeled compound that specifically binds to a molecule on the tumor. Fluorescent probes for molecular imaging are largely classified as 2 types: a fluorescence-labeled antibody targeting a molecule specifically expressed on the tumor cell surface such as epidermal growth factor receptor or vascular endothelial growth factor (VEGF); and a fluorescence-labeled small molecule compound targeting a molecule specifically expressed in tumor cells including c-Met, glutathione S-transferase, γ-glutamyltranspeptidase, cathepsin, or endothelin A receptor. These probes successfully detected colorectal tumors in several animal studies. Moreover, 3 recent human clinical trials evaluating endoscopic molecular imaging for colorectal tumors have been reported. In one study, a Cy5-labeled synthetic peptide against c-Met was developed, and fluorescent endoscopic observation with this probe detected a greater number of colorectal adenomas than with white light observation. Another trial used IR800-labeled anti-VEGF antibody, which sensitively detected human colorectal adenomas by fluorescent endoscopy. Last, a fluorescent probe with synthetic peptide against BRAF-positive cells was able to visualize sessile serrated lesions. The fluorescent probes accumulated at very high levels in colorectal tumor cells but at lower levels in surrounding nonneoplastic mucosa. Key Messages: We expect that molecular imaging techniques with fluorescent probes will soon lead to the establishment of a highly sensitive endoscopic method for colorectal tumor detection.

A versatile toolbox for investigating biological processes based on quinone methide chemistry: From self-immolative linkers to self-immobilizing agents

Quinone methide (QM) species have been included in the design of various functional molecules. In this review, we present a comprehensive overview of bioanalytical tools based on QM chemistry. In the first part, we focus on self-immolative linkers that have been incorporated into functional molecules such as prodrugs and fluorescent probes. In the latter half, we outline how the highly electrophilic property of QMs, enabling them to react rapidly with neighboring nucleophiles, has been applied to develop inhibitors or labeling probes for enzymes, as well as self-immobilizing fluorogenic probes with high spatial resolution. This review systematically summarizes the versatile QM toolbox available for investigating biological processes.

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.

Endoscopic imaging in inflammatory bowel disease: current developments and emerging strategies

INTRODUCTION

Developments in enhanced and magnified endoscopy have signified major advances in endoscopic imaging of ileocolonic pathology in inflammatory bowel disease (IBD). Artificial intelligence is increasingly being used to augment the benefits of these advanced techniques. Nevertheless, treatment of IBD patients is frustrated by high rates of non-response to therapy, while delayed detection and failures to detect neoplastic lesions impede successful surveillance. A possible solution is offered by molecular imaging, which adds functional imaging data to mucosal morphology assessment through visualizing biological parameters. Other label-free modalities enable visualization beyond the mucosal surface without the need of tracers.

AREAS COVERED

A literature search up to May 2020 was conducted in PubMed/MEDLINE in order to find relevant articles that involve the (pre-)clinical application of high-definition white light endoscopy, chromoendoscopy, artificial intelligence, confocal laser endomicroscopy, endocytoscopy, molecular imaging, optical coherence tomography, and Raman spectroscopy in IBD.

EXPERT OPINION

Enhanced and magnified endoscopy have enabled an improved assessment of the ileocolonic mucosa. Implementing molecular imaging in endoscopy could overcome the remaining clinical challenges by giving practitioners a real-time in vivo view of targeted biomarkers. Label-free modalities could help optimize the endoscopic assessment of mucosal healing and dysplasia detection in IBD patients.

Endoscopic molecular imaging in inflammatory bowel disease

Molecular imaging is a technique for imaging the processes occurring in a living body at a molecular level in real-time, combining molecular cell biology with advanced imaging technologies using molecular probes and fluorescence. Gastrointestinal endoscopic molecular imaging shows great promise for improving the identification of neoplasms, providing characterization for patient stratification and assessing the response to molecular targeted therapy. In inflammatory bowel disease, endoscopic molecular imaging can be used to assess disease severity and predict therapeutic response and prognosis. Endoscopic molecular imaging is also able to visualize dysplasia in the presence of background inflammation. Several preclinical and clinical trials have evaluated endoscopic molecular imaging; however, this area is just beginning to evolve, and many issues have not been solved yet. In the future, it is expected that endoscopic molecular imaging will be of increasing interest among clinicians as a new technology for the identification and evaluation of colorectal neoplasm and colitis-associated cancer.

A novel method for assessing the renal biopsy specimens using an activatable fluorescent probe

Gamma-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG) is an activatable fluorescent probe that can be activated by γ-glutamyltranspeptidase (GGT). The expression of GGT in the kidney, which is one of the major organs exhibiting enhanced GGT expression, is exclusively localised to the cortex. Here, we aimed to investigate the feasibility of gGlu-HMRG as a probe for the on-site assessment of renal biopsy specimens. gGlu-HMRG fluorescent probe was applied to the renal proximal tubular epithelial cells and cortical collecting duct cells in vitro, mouse kidneys ex vivo, and human biopsy specimens. In addition, the fluorescence intensities in the cortex and the medulla were comparatively evaluated in the biopsy specimens. The fluorescence signal was rapidly detected in the renal proximal tubular epithelial cells, whereas that in the cortical collecting duct cells was not detected. The fluorescence signal was detected in the mouse kidneys ex vivo without markedly affecting the tissue morphology. In the human biopsy specimens, the fluorescence signal in the cortex was significantly distinct from that in the medulla (p < 0.05). Thus, this fluorescent probe can be used to distinctly identify the renal cortex in the biopsy specimens.

Asymmetric Si-rhodamine scaffolds: rational design of pH-durable protease-activated NIR probes in vivo

A group of asymmetric Si-rhodamine scaffolds was designed for protease-activated NIR probes. Dual pH-inertia for both spirocyclized fluorescent probes and fluorescent products of zwitterions form over a wide range of pH (4.0-11.0). Leucine aminopeptidase (LAP) and γ-glutamyl transpeptidase (GGT) were monitored by fluorescent imaging in vivo.

Efficacy and clinical monitoring strategies for immune checkpoint inhibitors and targeted cytokine immunotherapy for locally advanced and metastatic colorectal cancer

Colorectal cancer (CRC) is the fourth most common cancer type and is the second leading cause of cancer deaths annually in the United States. Conventional treatment options include postoperative (adjuvant) and preoperative (neoadjuvant) chemotherapy and radiotherapy. Although these treatment modalities have shown to decrease tumor burden, a major limitation to chemothearpy/radiotherapy is the high recurrence rate in patients. Immune-modulation strategies have emerged as a promising new therapeutic avenue to reduce this recurrence rate while minimizing undesirable systemic side effects. This review will focus specifically on the mechanisms of monoclonal antibodies: immune checkpoint inhibitors and cytokines, as well as current drugs approved by the Food and Drug Administration (FDA) and new clinical/pre-clinical trials. Finally, this review will investigate emerging methods used to monitor tumor response post-treatment.

Molecular endoscopic imaging: the future is bright

The prediction and final survival rate of gastrointestinal cancers are dependent on the stage of disease. The ideal would be to detect those gastrointestinal lesions at early stage or even premalignant forms which are difficult to detect by conventional endoscopy with white light optical imaging as they show minimum or no changes in morphological characteristics and are thus left untreated. The introduction of molecular imaging has greatly changed the pattern for detecting gastrointestinal lesions from purely macroscopic structural imaging to the molecular level. It allows microscopic examination of the gastrointestinal mucosa with endoscopy after the topical or systemic application of molecular probes. In recent years, major advancements in endoscopic instruments and specific molecular probes have been achieved. This review focuses on the current status of endoscopic imaging and highlights the application of molecular imaging in gastrointestinal and hepatic disease in the context of diagnosis and therapy based on recently published literature in this field. We also discuss the challenges of molecular endoscopic imaging, its future directions and potential that could have a tremendous impact on endoscopic research and clinical practice in future.

Ratiometric Detection of γ-Glutamyltransferase in Human Colon Cancer Tissues Using a Two-Photon Probe

γ-Glutamyltransferase (GGT) plays a role in cleaving the γ-glutamyl bond of glutathione. The GGT is known to be overexpressed in some tumors and has been recognized as a potential biomarker for malignant tumors. Colon cancer is one of the most common cancers worldwide; however, there is no quantitative method for detecting cancer cells in human colon tissues. In this study, we report a ratiometric two-photon probe for GGT that can be applied in human colon tissues. The probe (Probe 2) showed high fluorescence efficiency, marked fluorescence changes, excellent kinetics, and selectivity for the GGT in live colon cells. Additionally, we obtained ratiometric two-photon microscopy images of GGT activity in human colon tissue. We used this method to compare normal and cancer tissues based on their ratio values; the ratio value was higher in cancer tissue than in normal tissue. This study provides a method for quantitative analysis of GGT, particularly in human colon cancer, which will be useful for studying GGT-related diseases and diagnosing colon cancer.

Epidermal growth factor receptor-targeted molecular imaging of colorectal tumors: Detection and treatment evaluation of tumors in animal models

To overcome the problem of overlooking colorectal tumors, a new and highly sensitive modality of colonoscopy is needed. Moreover, it is also important to establish a new modality to evaluate viable tumor volume in primary lesions of colorectal cancer (CRC) during chemotherapy. Therefore, we carried out molecular imaging of colorectal tumors targeting epidermal growth factor receptor (EGFR), which is highly expressed on tumor cells, for evaluating chemotherapeutic efficacy and for endoscopic detection of colorectal adenomas. We first attempted to image five CRC cell lines with various levels of EGFR expression using an Alexa Fluor-labeled anti-EGFR monoclonal antibody (AF-EGFR-Ab). A strong fluorescence signal was observed in the cells depending on the level of EGFR expression. When nude mice xenografted with LIM1215 CRC cells, which highly express EGFR, were i.v. injected with AF-EGFR-Ab, a strong fluorescence signal appeared in the tumor with a high signal to noise ratio, peaking at 48 hours after injection and then gradually decreasing, as shown using an IVIS Spectrum system. When the xenografted mice were treated with 5-fluorouracil, fluorescence intensity in the tumor decreased in proportion to the viable tumor cell volume. Moreover, when the colorectum of azoxymethane-treated rats was observed using a thin fluorescent endoscope with AF-EGFR-Ab, all 10 small colorectal adenomas (≤3 mm) were detected with a clear fluorescence signal. These preliminary results of animal experiments suggest that EGFR-targeted fluorescent molecular imaging may be useful for quantitatively evaluating cell viability in CRC during chemotherapy, and also for detecting small adenomas using a fluorescent endoscope.

A novel mitochondrial-targeting near-infrared fluorescent probe for imaging γ-glutamyl transpeptidase activity in living cells

γ-Glutamyl transpeptidase (GGT) plays an essential role in regulating cellular glutathione and cysteine homeostasis, and its abnormal elevation is associated with different diseases including cancers. Here a novel mitochondrial-targeting near-infrared fluorescent probe was designed for GGT by conjugating glutamate acid to a newly synthesized amine hemicyanine fluorophore. The fluorescent probe was initially non-emissive due to the formation of an amide bond which destroyed the electronic-donating ability of the amine moiety and disrupted the push-pull structure. GGT-mediated cleavage of the γ-glutamyl bond regenerated the initial fluorophore with distinct intramolecular charge transfer (ICT) and activated the fluorescence signal. The fluorescent probe displayed a linear relationship to the concentration of GGT in the range of 1.0-90 U L-1, with an estimated limit of detection (LOD) of 0.4 U L-1. Its ability to target and image mitochondrial GGT activity was demonstrated in living cells with high specificity and fast response. We believe our near-infrared fluorescent probe could have great potential in imaging mitochondrial GGT activity and elucidating GGT-associated pathological consequences in living cells and even small animal models.

Molecular imaging within the lower gastrointestinal tract: From feasibility to future

Molecular imaging is based on the labelling of defined molecular targets through the utilization of fluorescently linked probes and their subsequent detection with high-resolution endoscopic devices, thereby enabling visualization of single molecules including receptors. Whereas early studies have used molecular imaging for improved visualization and detection of early dysplasia and cancer as well as for assessing intestinal inflammation and inflammation-associated cancer within the gastrointestinal (GI) tract, more recent studies have impressively demonstrated that molecular imaging can also be used to characterize and visualize the molecular fingerprint of cancer and inflammation in vivo and in real time. With this, molecular imaging can be used to guide expression-tailored individualized therapy. With the rapid expansion and diversification of the repertoire of biological agents utilized in inflammatory bowel disease and cancer, this approach is gaining increasing attention. Within this review, we first summarize the technical components commonly used for molecular imaging and then review preclinical and clinical studies and evolving clinical applications on molecular imaging within the lower GI tract. Molecular imaging has the potential to significantly change endoscopic diagnosis and subsequent targeted therapy of gastrointestinal cancer and chronic gastrointestinal diseases.

Molecular endoscopic imaging in cancer

Cancer is one of the major causes of death in both the USA and Europe. Molecular imaging is a novel field that is revolutionizing cancer management. It is based on the molecular signature of cells in order to study the human body both in normal and diseased conditions. The emergence of molecular imaging has been driven by the difficulties associated with cancer detection, particularly early-stage premalignant lesions which are often unnoticed as a result of minimal or no structural changes. Endoscopic surveillance is the standard method for early-stage cancer detection. In addition to recent major advancements in endoscopic instruments, significant progress has been achieved in the exploration of highly specific molecular probes and the combination of both will permit significant improvement of patient care. In this review, we provide an outline of the current status of endoscopic imaging and focus on recent applications of molecular imaging in gastrointestinal, hepatic and other cancers in the context of detection, targeted therapy and personalized medicine. As new imaging agents have the potential to broadly expand our cancer diagnostic capability, we will also present an overview of the main types of optical molecular probes with their pros and cons. We conclude by discussing the challenges and future prospects of the field.

Molecular imaging in gastroenterology: A route for personalized endoscopy

With the rapid expansion and diversification of the repertoire of biological agents utilized in inflammatory bowel diseases and cancer and the increase in oncological patients in gastroenterology, visualization of single receptor or molecular target expression and the subsequent initiation of expression tailored therapy are gaining increasing attention. Through the combination of utilizing fluorescently labeled probes with high specificity towards defined molecular targets and their subsequent detection and visualization with endoscopic devices, molecular imaging is a new emerging field focusing on the receptor expression within the mucosa on a cellular level rather than on macroscopic changes. In the past years various new technological and molecular probes have been successfully utilized for molecular imaging. Within this review, we summarize different technologies as well as molecular probes applied in molecular imaging and review current and past approaches for functional imaging with molecular endoscopy within the GI Tract and resulting clinical applications. It can be expected that molecular imaging allows for individualized diagnostic approaches and patient tailored medicine in the future.

Fluorescence tumor imaging by i.v. administered indocyanine green in a mouse model of colitis-associated colon cancer

Fluorescence tumor imaging using exogenous fluorescent tumor‐targeting agents has potential to improve early tumor detection. The fluorescent contrast agent indocyanine green (ICG) is used in medical diagnostics. The aim of the present study is to investigate the tumor imaging capability and the imaging mechanism of i.v. administered ICG in a mouse model of colitis‐associated colon cancer. To do this, an azoxymethane/dextran sodium sulfate‐induced colon cancer mouse model was used. Ex vivo imaging experiments were carried out 1 hour after i.v. injection of ICG. The ICG fluorescence was observed in the colon tumor tissues, with sufficient tumor to normal tissue ratio, correlating with tumor malignancy. In the tumor tissues, ICG fluorescence was localized in the vascular interstitial tissue. Immunofluorescence microscopy revealed that tumor cells formed tight junctions normally, suggesting an inability of tumor cellular uptake of ICG. In contrast, tumor tissues increased the CD31‐immunoreactive endothelial cell area, and accumulated stromal cells immunoreactive for COX‐2 and tumor cell population immunoreactive for inducible nitric oxide synthase. In vivo vascular permeability assay revealed that prostaglandin E₂ promoted the endothelial cell permeability of ICG. In conclusion, our data indicated that fluorescence contrast‐enhanced imaging following i.v. administered ICG can be applied to the detection of colon tumors in a mouse colitis‐associated colon cancer model. The tumor tissue preference of ICG in the present model can be attributed to the enhanced vascular leakage of ICG involving inflammatory mediators, such as COX‐2 and inducible nitric oxide synthase, in conjunction with increased tumor vascularity.

A Novel Theranostic Combination of Near-infrared Fluorescence Imaging and Laser Irradiation Targeting c-KIT for Gastrointestinal Stromal Tumors

It is difficult to distinguish gastrointestinal stromal tumors (GISTs) from other types of submucosal tumors under conventional gastrointestinal endoscopy. We aimed to detect GISTs by molecular fluorescence imaging using a near-infrared (NIR) photosensitizer (IR700)-conjugated anti-c-KIT antibody and to treat GISTs by photoimmunotherapy with NIR irradiation as a non-invasive theranostic procedure. We also investigated the therapeutic mechanisms. Methods: Human GIST cell lines GIST-T1 and GIST-882M were incubated with IR700-conjugated anti-c-KIT antibody, IR700-12A8, and observed by confocal laser microscopy. Mice with GIST-T1 xenografts or rats with orthotopic xenografts were injected with IR700-12A8 or AF488-conjugated antibody, and observed under IVIS or autofluorescence imaging (AFI) endoscopy. GIST cells were treated with IR700-12A8 and NIR light in vitro and vivo, and cell viability, histology and apoptosis were evaluated. Results: Strong red fluorescence of IR700-12A8 was observed on the cell membrane of GIST cells and was gradually internalized into the cytoplasm. Tumor-specific accumulation of IR700-12A8 was observed in GIST-T1 xenografts in mice. Under AFI endoscopy, a strong fluorescence signal was observed in orthotopic GIST xenografts in rats through the normal mucosa covering the tumor. The percentage of dead cells significantly increased in a light-dose-dependent manner and both acute necrotic and late apoptotic cell death was observed with annexin/PI staining. Cleaved PARP expression was significantly increased after IR700-12A8-mediated NIR irradiation, which was almost completely reversed by NaN₃. All xenograft tumors (7/7) immediately regressed and 4/7 tumors completely disappeared after IR700-12A8-mediated NIR irradiation. Histologic assessment and TUNEL staining revealed apoptosis in the tumors. Conclusion: NIR fluorescence imaging using IR700-12A8 and subsequent NIR irradiation could be a very effective theranostic technology for GIST, the underlying mechanism of which appears to involve acute necrosis and supposedly late apoptosis induced by singlet oxygen.

Dynamic fluorescent imaging with the activatable probe, γ-glutamyl hydroxymethyl rhodamine green in the detection of peritoneal cancer metastases: Overcoming the problem of dilution when using a sprayable optical probe

Optical fluorescence-guided imaging is increasingly used to guide surgery and endoscopic procedures. Activatable probes are particularly useful because of high target-to-background ratios that increase sensitivity for tiny cancer foci. However, green fluorescent activatable probes suffer from interference from autofluorescence found in biological tissue. The purpose of this study was to determine if dynamic imaging can be used to differentiate specific fluorescence arising from an activated probe in a tumor from autofluorescence in background tissues especially when low concentrations of the dye are applied. Serial fluorescence imaging was performed using various concentrations of γ-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG) which was sprayed on the peritoneal surface with tiny implants of SHIN3-DsRed ovarian cancer tumors. Temporal differences in signal between specific green fluorescence in cancer foci and non-specific autofluorescence in background tissue were measured at 5, 10, 20 and 30 min after application of gGlu-HMRG and were processed into three kinetic maps reflecting maximum fluorescence signal (MF), wash-in rate (WIR), and area under the curve (AUC), respectively. Using concentrations up to 10 μM of gGlu-HMRG, the fluorescence intensity of cancer foci was significantly higher than that of small intestine but only at 30 min. However, on kinetic maps derived from dynamic fluorescence imaging, the signal of cancer foci was significantly higher than that of small intestine after only 5 min even at concentrations as low as 2.5 μM of gGlu-HMRG (p < 0.01). At lower concentrations, kinetic maps derived from dynamic fluorescence imaging were superior to unprocessed images for cancer detection.

Colonoscopy-based colorectal cancer modeling in mice with CRISPR-Cas9 genome editing and organoid transplantation

Most genetically engineered mouse models (GEMMs) of colorectal cancer are limited by tumor formation in the small intestine, a high tumor burden that limits metastasis, and the need to generate and cross mutant mice. Cell line or organoid transplantation models generally produce tumors in ectopic locations-such as the subcutaneous space, kidney capsule, or cecal wall-that do not reflect the native stromal environment of the colon mucosa. Here, we describe detailed protocols to rapidly and efficiently induce site-directed tumors in the distal colon of mice that are based on colonoscopy-guided mucosal injection. These techniques can be adapted to deliver viral vectors carrying Cre recombinase, CRISPR-Cas9 components, CRISPR-engineered mouse tumor organoids, or human cancer organoids to mice to model the adenoma-carcinoma-metastasis sequence of tumor progression. The colonoscopy injection procedure takes ∼15 min, including preparation. In our experience, anyone with reasonable hand-eye coordination can become proficient with mouse colonoscopy and mucosal injection with a few hours of practice. These approaches are ideal for a wide range of applications, including assessment of gene function in tumorigenesis, examination of tumor-stroma interactions, studies of cancer metastasis, and translational research with patient-derived cancers.

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.

Targeting Mucosal Endothelin-A-Receptor Expression by Fluorescence Endoscopy is Feasible to Detect and Characterize Colitis-Associated Cancer in Mice

BACKGROUND

To facilitate onsite decision-making during endoscopy, both accurate detection and in vivo characterization of preneoplasia are prerequisites. However, no endoscopy technique is available that meets both demands satisfactorily. We evaluated endothelin-receptor A (ETAR)-guided fluorescence endoscopy (FE) in vivo and fluorescence reflectance imaging (FRI) ex vivo for detection and characterization of early dysplastic colitis-associated colonic lesions.

METHODS

Colorectal cancerogenesis was investigated in the inflammatory driven AOM-DSS model and spontaneous adenoma development in ApcMin mice. A Cy5.5-labeled nonpeptidic ETAR-specific imaging probe was injected intravenously to assess tumor development in vivo by white light endoscopy (WLE) and FE. Ex vivo tumors were evaluated by FRI, histological examination, and western blot analysis. In addition, tissue samples from patients with colitis-associated malignant and nonmalignant mucosal alterations were analyzed. Specificity experiments were performed using an unspecific Cy3.5-glycine tracer.

RESULTS

Overall, 62 adenomas were observed. FE was able to detect and quantify ETAR expression targeting the ETAR-specific photoprobe. A significantly higher fluorescent contrast was detected in colonic adenomas compared to adjacent nonmalignant mucosa by FE (64.3 ± 7.9 vs. 56.6. ± 7.0; P < 0.001). These results were confirmed by FRI examination, immunochemistry, and western blot analysis. Additionally, ETAR expression in samples from human patients with colitis-associated cancer was highly elevated compared to nonmalignant alterations. Specificity experiments indicated a high binding-specificity of the applied ETAR photoprobe (1.4 ± 0.3 vs. 2.5 ± 0.7; P < 0.001).

CONCLUSIONS

We introduced ETAR guided FE in mice for successful in vivo detection and characterization of colorectal neoplasia on a molecular level.

Imaging of Mucosal Inflammation: Current Technological Developments, Clinical Implications, and Future Perspectives

In recent years, various technological developments markedly improved imaging of mucosal inflammation in patients with inflammatory bowel diseases. Although technological developments such as high-definition-, chromo-, and autofluorescence-endoscopy led to a more precise and detailed assessment of mucosal inflammation during wide-field endoscopy, probe-based and stationary confocal laser microscopy enabled in vivo real-time microscopic imaging of mucosal surfaces within the gastrointestinal tract. Through the use of fluorochromes with specificity against a defined molecular target combined with endoscopic techniques that allow ultrastructural resolution, molecular imaging enables in vivo visualization of single molecules or receptors during endoscopy. Molecular imaging has therefore greatly expanded the clinical utility and applications of modern innovative endoscopy, which include the diagnosis, surveillance, and treatment of disease as well as the prediction of the therapeutic response of individual patients. Furthermore, non-invasive imaging techniques such as computed tomography, magnetic resonance imaging, scintigraphy, and ultrasound provide helpful information as supplement to invasive endoscopic procedures. In this review, we provide an overview on the current status of advanced imaging technologies for the clinical non-invasive and endoscopic evaluation of mucosal inflammation. Furthermore, the value of novel methods such as multiphoton microscopy, optoacoustics, and optical coherence tomography and their possible future implementation into clinical diagnosis and evaluation of mucosal inflammation will be discussed.

Molecular Imaging of Colorectal Tumors by Targeting Colon Cancer Secreted Protein-2 (CCSP-2)

A versatile biomarker for detecting colonic adenoma and colon cancer has yet to be developed. Colon cancer secreted protein-2 (CCSP-2) is a protein specifically expressed and secreted in colon adenomas and cancers. We developed a fluorescent imaging method based on CCSP-2 targeting for a more sensitive and specific detection of colorectal tumors. CCSP-2 expression was evaluated in human colon adenoma and colorectal specimens. Anti–CCSP-2 antibody was labeled with a near-infrared fluorescent dye, FPR-675, and molecular imaging of surgical human colorectal tumors was performed. Immunohistochemistry identified CCSP-2 expression in 87.0% of colorectal cancer specimens and 89.5% of colon adenoma specimens. Fluorescence imaging of surgical human colon specimens after spraying treatment with the probe permitted a clear distinction of cancer from paired normal colon tissue (target-to-background ratio, 4.09 ± 0.42; P < .001). CCSP-2 targeting imaging was also evaluated in patient-derived colon cancer xenograft mouse and liver metastasis murine models. CCSP-2–positive colon cancer xenografts and liver metastases were visualized by near-infrared fluorescence imaging after intravenous injection of the probe, which showed significantly higher fluorescence. Our results show that CCSP-2 is a promising marker for colorectal tumor detection in clinical settings and that a CCSP-2–targeting molecular imaging strategy might improve the diagnosis of colorectal tumors in metastatic or recurrent cancers and aid in early colonoscopic detection of premalignant lesions.

Simultaneous Detection of EGFR and VEGF in Colorectal Cancer using Fluorescence-Raman Endoscopy

Fluorescence endomicroscopy provides quick access to molecular targets, while Raman spectroscopy allows the detection of multiple molecular targets. Using a simultaneous fluorescence-Raman endoscopic system (FRES), we herein demonstrate its potential in cancer diagnosis in an orthotopically induced colorectal cancer (CRC) xenograft model. In the model, epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) were targeted with antibody-conjugated fluorescence and surface-enhanced Raman scattering (F-SERS) dots. FRES demonstrated fast signal detection and multiplex targeting ability using fluorescence and Raman signals to detect the F-SERS dots. In addition, FRES showed a multiplex targeting ability even on a subcentimeter-sized CRC after spraying with a dose of 50 µg F-SERS dots. In conclusion, molecular characteristics of tumor cells (EGFR in cancer cell membranes) and tumor microenvironments (VEGF in the extracellular matrix) could be simultaneously investigated when performing a colonoscopy.

Cell-surface markers for colon adenoma and adenocarcinoma

Early detection of colorectal cancer (CRC) is crucial for effective treatment. Among CRC screening techniques, optical colonoscopy is widely considered the gold standard. However, it is a costly and invasive procedure with a low rate of compliance. Our long-term goal is to develop molecular imaging agents for the non-invasive detection of CRC by molecular imaging-based colonoscopy using CT, MRI or fluorescence. To achieve this, cell surface targets must be identified and validated. Here, we report the discovery of cell-surface markers that distinguish CRC from surrounding tissues that could be used as molecular imaging targets. Profiling of mRNA expression microarray data from patient tissues including adenoma, adenocarcinoma, and normal gastrointestinal tissues was used to identify potential CRC specific cell-surface markers. Of the identified markers, six were selected for further validation (CLDN1, GPR56, GRM8, LY6G6D/F, SLCO1B3 and TLR4). Protein expression was confirmed by immunohistochemistry of patient tissues. Except for SLCO1B3, diffuse and low expression was observed for each marker in normal colon tissues. The three markers with the greatest protein overexpression were CLDN1, LY6G6D/F and TLR4, where at least one of these markers was overexpressed in 97% of the CRC samples. GPR56, LY6G6D/F and SLCO1B3 protein expression was significantly correlated with the proximal tumor location and with expression of mismatch repair genes. Marker expression was further validated in CRC cell lines. Hence, three cell-surface markers were discovered that distinguish CRC from surrounding normal tissues. These markers can be used to develop imaging or therapeutic agents targeted to the luminal surface of CRC.

Rapid visualization of nonmelanoma skin cancer

BACKGROUND

Mohs micrographic surgery examines all margins of the resected sample and has a 99% cure rate. However, many nonmelanoma skin cancers (NMSCs) are not readily amenable to Mohs micrographic surgery. This defines an unmet clinical need to assess the completeness of non-Mohs micrographic surgery resections during surgery to prevent re-excision/recurrence.

OBJECTIVE

We sought to examine the utility of quenched activity-based probe imaging to discriminate cancerous versus normal-appearing skin tissue.

METHODS

The quenched activity-based probe GB119 was applied to NMSC excised from 68 patients. We validated activation of the probe for hematoxylin-eosin-confirmed cancerous tissue versus normal-appearing skin tissue.

RESULTS

Topical application of the probe differentiated basal cell carcinoma and squamous cell carcinoma from normal-appearing skin with overall estimated sensitivity and specificity of 0.989 (95% confidence interval 0.940-1.00) and 0.894 (95% confidence interval 0.769-0.965), respectively. Probe activation accurately defined peripheral margins of NMSC as compared with conventional hematoxylin-eosin-based pathology.

LIMITATIONS

This study only examined NMSC debulking excision specimens. The sensitivity and specificity for this approach using final NMSC excision margins will be clinically important.

CONCLUSIONS

These findings merit further studies to determine whether quenched activity-based probe technology may enable cost-effective increased cure rates for patients with NMSC by reducing re-excision and recurrence rates with a rapid and easily interpretable technological advance.

Advanced imaging in colonoscopy: contemporary approach to dysplasia surveillance in inflammatory bowel disease

Inflammatory bowel disease (IBD) (ulcerative colitis (UC) and Crohn's disease (CD)) is a chronic relapsing/remitting condition characterised by intestinal inflammation. One of the main concerns in patients with longstanding ulcerative and Crohn's colitis is development of colonic dysplasia and colorectal cancer (CRC), a risk higher than that of the general population. Colonoscopy surveillance programmes have been developed by major societies worldwide to improve early dysplasia detection and treatment, thus preventing progression to colorectal cancer. Colonoscopy is an imperfect tool as lesions can be missed, an issue even more relevant to colitic patients, where mucosal inspection and lesion recognition may prove challenging. Extensive research has been undertaken on performance improvement in this area while technical advances in optical imaging, such as high-definition, have made their way into modern endoscopy units. Techniques and technologies available to enhance optical diagnosis of dysplasia in inflammatory bowel disease are reviewed in this paper, focusing on those that are realistic, widely available and feasible for everyday practice.

Fluorescence Identification of Head and Neck Squamous Cell Carcinoma and High-Risk Oral Dysplasia With BLZ-100, a Chlorotoxin-Indocyanine Green Conjugate

IMPORTANCE

Surgical cure of head and neck squamous cell carcinoma (HNSCC) remains hampered by inadequately resected tumors and poor recognition of lesions with malignant potential. BLZ-100 is a chlorotoxin-based, tumor-targeting agent that has not yet been studied in HNSCC.

OBJECTIVE

To evaluate BLZ-100 uptake in models of HNSCC and oral dysplasia.

DESIGN, SETTING, AND PARTICIPANTS

This was an observational study (including sensitivity and specificity analysis) of BLZ-100 uptake in an orthotopic xenograft mouse model of HNSCC and a carcinogen-induced dysplasia model of hamster cheek pouches.

INTERVENTIONS

Various HNSCC xenografts were established in the tongues of NOD-scid IL2Rgammanull (NSG) mice. BLZ-100 was intravenously injected and fluorescence uptake was measured. To induce dysplasia, the carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) was applied to the cheek pouch of Golden Syrian hamsters for 9 to16 weeks. BLZ-100 was subcutaneously injected, and fluorescence uptake was measured.

MAIN OUTCOMES AND MEASURES

The signal-to-background ratio (SBR) of BLZ-100 was measured in tumor xenografts. To calculate the sensitivity and specificity of BLZ-100 uptake, a digital grid was placed over tissue sections and correlative histologic sections to discretely measure fluorescence intensity and presence of tumor; a receiver operating characteristic (ROC) curve was then plotted. In the hamster dysplasia model, cheeks were graded according to dysplasia severity. The SBR of BLZ-100 was compared among dysplasia grades.

RESULTS

In HNSCC xenografts, BLZ-100 demonstrated a mean (SD) SBR of 2.51 (0.47). The ROC curve demonstrated an area under the curve (AUC) of 0.89; an SBR of 2.50 corresponded to 92% sensitivity and 74% specificity. When this analysis was focused on the tumor and nontumor interface, the AUC increased to 0.97; an SBR of 2.50 corresponded to 95% sensitivity and 91% specificity. DMBA treatment of hamster cheek pouches generated lesions representing all grades of dysplasia. The SBR of high-grade dysplasia was significantly greater than that of mild-to-moderate dysplasia (2.31 [0.71] vs 1.51 [0.34], P = .006).

CONCLUSIONS AND RELEVANCE

BLZ-100 is a sensitive and specific marker of HNSCC and can distinguish high-risk from low-risk dysplasia. BLZ-100 has the potential to serve as an intraoperative guide for tumor margin excision and identification of premalignant lesions.

Molecular endoscopy for targeted imaging in the digestive tract

Endoscopy uses optical imaging methods to investigate tissue in a non-destructive manner with high resolution over a broad range of wavelengths, thus providing a powerful tool to rapidly visualise mucosal surfaces in the digestive tract. Molecular imaging is an important advancement that has been clinically demonstrated for early cancer detection and guidance of therapy. With this approach, imaging can be used to observe expression patterns of molecular targets to improve understanding of key biological mechanisms that drive disease progression. Prototype devices that collect fluorescence for wide-field or microscopic images have been developed. Several targeting moieties, including enzyme-activatable probes, antibodies, peptides, and lectins, have been administered in preclinical and clinical imaging studies in vivo. These emerging technologies provide useful approaches to study molecular events in different signalling pathways, producing insights that could lead to improved interventions to prevent and treat gastrointestinal diseases. In this Review, we introduce the basic concepts that form the foundation for development of molecular endoscopy and summarise key results from preclinical and clinical studies.

Advances in endoscopic imaging in ulcerative colitis

Modern strategies for the treatment of ulcerative colitis require more accurate tools for gastrointestinal imaging to better assess mucosal disease activity and long-term prognostic clinical outcomes. Recent advances in gastrointestinal luminal endoscopy are radically changing the role of endoscopy in every-day clinical practice and research trials. Advanced endoscopic imaging techniques including high-definition endoscopes, optical magnification endoscopy, and various chromoendoscopy techniques have remarkably improved endoscopic assessment of ulcerative colitis. More recently, optical biopsy techniques with either endocytoscopy or confocal laser endomicroscopy have shown great potential in predicting several histological changes in real time during ongoing endoscopy. Here, we review current applications of advanced endoscopic imaging techniques in ulcerative colitis and present the most promising upcoming headways in this field.

Surgical tissue handling methods to optimize ex vivo fluorescence with the activatable optical probe γ-glutamyl hydroxymethyl rhodamine green

Optical fluorescence imaging has been developed as an aid to intraoperative diagnosis to improve surgical and endoscopic procedures. Compared with other intraoperative imaging methods, it is lower in cost, has a high safety margin, is portable and easy to use. γ-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG) is a recently developed activatable fluorescence probe that emits strong fluorescence in the presence of the enzyme γ-glutamyl transpeptidase (GGT), which is overexpressed in many cancers, including ovarian cancer. Ex vivo testing is important for clinical approval of such probes. The diagnostic performance of gGlu-HMRG in fresh excised surgical specimens has been reported; however, details of tissue handling have not been optimized. In this study, we investigated four different tissue handling procedures to optimize imaging in excised tumor specimens. The fluorescence intensity time courses after the different tissue handling methods were compared. Additionally, the fluorescence positive areas were correlated with the presence of red fluorescent protein (RFP) in an RFP positive cell line as the standard of reference for cancer location. In the 'intact' groups, tumors yielded quick and homogeneous activation of gGlu-HMRG. In the 'rinse' and 'cut' groups, the fluorescence intensity of the tumor was a little lower than that in the intact group. In the 'pressed' groups, however, fluorescence intensity from gGlu-HMRG was lower over the entire time course, suggesting a decrease or relocation of excreted GGT. In conclusion, we demonstrate that the method of tissue handling prior to ex vivo imaging with the activatable probe gGlu-HMRG has a strong influence on the signal derived from the specimen. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Fluorescent imaging of superficial head and neck squamous cell carcinoma using a γ-glutamyltranspeptidase-activated targeting agent: a pilot study

Background

Detecting superficial head and neck squamous cell carcinoma (HNSCC) by endoscopy is challenging because of limited morphological hallmarks, and iodine cannot be applied to head and neck lesions due to severe mucosal irritation. γ-glutamyltranspeptidase (GGT), a cell surface enzyme, is overexpressed in several cancers, and it has been reported that γ-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG), a fluorescent targeting agent which can be enzymatically activated and becomes fluorescent after cleavage of a GGT-specific sequence, can be activated within a few minutes after application to animal models. We investigated whether early HNSCC can be detected by applying gGlu-HMRG to clinical samples.

Methods

gGlu-HMRG was applied to four HNSCC cell lines, and fluorescence was observed by fluorescence microscopy and flow cytometry. Immunohistological examination was performed in three recent cases of endoscopic submucosal dissection (ESD) to investigate GGT expression. Fluorescence imaging with gGlu-HMRG in eight clinical samples resected by ESD or surgery was performed, and fluorescence intensity of tumor and normal mucosa regions of interest (ROI) was prospectively measured.

Results

All four gGlu-HMRG-applied cell lines emitted green fluorescence. Immunohistological examination demonstrated that GGT was highly expressed in HNSCC of the recent three ESD cases but barely in the normal mucosa. Fluorescence imaging showed that iodine-voiding lesions became fluorescent within a few minutes after application of gGlu-HMRG in all eight resected tumors. Tumor ROI fluorescence intensity was significantly higher than in the normal mucosa five minutes after gGlu-HMRG application.

Conclusions

Fluorescence imaging with gGlu-HMRG would be useful for early detection of HNSCC.

From bench to bedside: molecular imaging in inflammatory bowel diseases

PURPOSE OF REVIEW

Standard structural imaging procedures such as endoscopy, ultrasonography, or MRI are an integral part of the rational management of patients with inflammatory bowel diseases (IBDs). There is nevertheless the need for further refined imaging approaches that are able to overcome the limitations of currently used formats. The advent of molecular imaging modalities that allow real-time visualization of cellular processes not only in the preclinical setting but also in clinical trials has demonstrated its ability to improve current therapeutic strategies. The purpose of this review is to present and discuss advancements in the field of molecular imaging approaches in the IBD field.

RECENT FINDINGS

Recent preclinical and clinical studies have addressed the applicability of molecular imaging for improving the differentiation between benign and malignant mucosal alterations, increasing the detection of dysplastic intestinal lesions, and predicting individual responses to biological therapies.

SUMMARY

Molecular imaging in IBD represents an exciting and evolving field that has the potential to impact on current diagnostic and therapeutic algorithms in the treatment of IBD patients by analyzing and visualizing the molecular mechanisms that drive mucosal inflammation. It might enable us to base individualized therapeutic decisions on preceded molecular level analysis by suitable imaging modalities.

Predicting Therapeutic Response by in vivo Molecular Imaging in Inflammatory Bowel Diseases

BACKGROUND

Different invasive and non-invasive imaging modalities are indispensable tools in the management of inflammatory bowel disease (IBD) patients. Standard imaging procedures like white light endoscopy or MRI are used to define gut inflammation based on structural changes and altered morphology of the mucosa. Nevertheless, it has thus far not been possible to analyse biological processes at the cellular level, which drive intestinal inflammation in IBD patients. The recent advent of molecular imaging in the field of IBD has opened new promising avenues to allow personalized medicine approaches based on in vivo-detected molecular findings.

KEY MESSAGES

Recent clinical studies have attempted to address the issue of predicting therapeutic response to anti-tumor necrosis factor (TNF) treatment in IBD patients based on the molecular mechanism of action of these agents and corresponding in vivo assessment of mucosal immune responses. Several experimental studies have indicated that one of the main functions of efficacious anti-TNF therapy in IBD is the induction of intestinal cell apoptosis. Fittingly, a corresponding molecular-imaging study using single-photon emission CT for the localization and quantification of cell apoptosis, demonstrated that induction of mucosal T-cell apoptosis correlated with the therapeutic response to anti-TNF therapy in Crohn's disease patients. There was moreover a predictive capacity regarding therapeutic efficacy. As the main biological properties of anti-TNF antibodies in IBD are mediated through binding to membrane-bound TNF (mTNF) expressing intestinal cells, another study used molecular imaging for in vivo visualization of these cells via fluorescent anti-TNF antibodies to predict therapeutic efficacy of these agents. It could be shown that patients with high amounts of mTNF positive cells showed significantly better response rates compared to patients with low amounts of mTNF positive cells.

CONCLUSION

In vivo molecular imaging in IBD has the potential to have an impact on our current treatment approaches and may allow us to individualize specific therapies based on molecular level analysis.

Endoscopy-guided orthotopic implantation of colorectal cancer cells results in metastatic colorectal cancer in mice

Advanced stage colorectal cancer (CRC) is still associated with limited prognosis. For preclinical evaluation of novel therapeutic approaches, murine models with orthotopic tumor growth and distant metastases are required. However, these models usually require surgical procedures possibly influencing tumor immunogenicity and development. The aim of this study was to establish a minimal-invasive endoscopy-based murine orthotopic model of metastatic CRC. During colonoscopy of CD-1 nude and non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice, implantation of Caco-2 and HT-29 CRC cells was performed subcutaneously (s.c.) or orthotopic into the colonic submucosa. White light endoscopy (WLE) and fluorescence endoscopy (FE) were applied for tumor detection in vivo. Ex vivo, resected tumors were examined by fluorescence reflectance imaging (FRI), histology, gelatin zymography and immunohistochemistry. In CD-1 nude mice, marked tumor growth was observed within 14 days after subcutaneous implantation while submucosal implantation failed to induce CRC after 17 weeks. In contrast, in NOD/SCID mice submucosal injection of HT-29 cells resulted in pronounced tumor growth 12 days post injectionem. Subsequently, rapid tumor expansion occurred, occupying the entire colonic circumference. Importantly, post mortem histological analyses confirmed liver metastases in 28.6 % and peritoneal metastases in 14.3 % of all mice. FRI and gelatin zymography did not detect a significantly increased matrix metalloproteinases (MMPs) expression in s.c. implanted tumors while MMP-tracer uptake was significantly enhanced in orthotopic implanted tumors. Neither s.c. nor orthotopic Caco-2 cell implantation resulted in tumor development. We successfully established an endoscopy-based model of metastatic CRC in immunodeficient mice.

Novel Hexosaminidase-Targeting Fluorescence Probe for Visualizing Human Colorectal Cancer

Precise tumor diagnosis and evaluation of disease extent are crucial for treatment of solid cancers. In order to complement the limited ability of the unaided human eye to discriminate tumor tissue and normal tissue, we have developed a series of fluorescence probes activatable specifically in cancer tissues. Here, we describe the design, synthesis, and application of a new fluorescence probe targeting hexosaminidase (HMRef-βGlcNAc), which is located in lysosomes and is overexpressed in several carcinomas, including colorectal cancer. This probe could sensitively detect intracellular hexosaminidase activity in human colorectal cancer cell lines, and could visualize tiny metastatic nodules (smaller than 1 mm) in a mouse model of disseminated human peritoneal colorectal cancer (HCT116). In human colorectal cancer specimens obtained at surgery, the probe showed high tumor sensitivity/specificity, together with a high tumor-to-normal signal ratio. HMRef-βGlcNAc is a promising candidate for clinical application during surgical or endoscopic procedures to treat colorectal cancer.

Advanced gastrointestinal endoscopic imaging for inflammatory bowel diseases

Gastrointestinal luminal endoscopy is of paramount importance for diagnosis, monitoring and dysplasia surveillance in patients with both, Crohn’s disease and ulcerative colitis. Moreover, with the recent recognition that mucosal healing is directly linked to the clinical outcome of patients with inflammatory bowel disorders, a growing demand exists for the precise, timely and detailed endoscopic assessment of superficial mucosal layer. Further, the novel field of molecular imaging has tremendously expanded the clinical utility and applications of modern endoscopy, now encompassing not only diagnosis, surveillance, and treatment but also the prediction of individual therapeutic responses. Within this review, we describe how novel endoscopic approaches and advanced endoscopic imaging methods such as high definition and high magnification endoscopy, dye-based and dye-less chromoendoscopy, confocal laser endomicroscopy, endocytoscopy and molecular imaging now allow for the precise and ultrastructural assessment of mucosal inflammation and describe the potential of these techniques for dysplasia detection.