New technologies for human cancer imaging

Intraoperative molecular imaging can identify lung adenocarcinomas during pulmonary resection

BACKGROUND

More than 80,000 people undergo resection of a pulmonary tumor each year, and the only method to determine if the tumor is malignant is histologic analysis. We propose that a targeted molecular contrast agent could bind lung adenocarcinomas, which could be identified using real-time optical imaging at the time of surgery.

METHODS

Fifty patients with a biopsy-proven lung adenocarcinoma were enrolled. Before surgery, patients were systemically administered 0.1 mg/kg of a fluorescent folate receptor alpha (FRα)-targeted molecular contrast agent by intravenous infusion. During surgery, tumors were imaged in situ and ex vivo, after the lung parenchyma was dissected to directly expose the tumor to the imaging system.

RESULTS

Tumors ranged from 0.3 to 7.5 cm (mean: 2.6 cm), and 46 of 50 (92%) lung adenocarcinomas were fluorescent. No false uptake occurred, and in 2 cases, intraoperative imaging revealed tumor metastases (3 mm and 6 mm) that were not recognized preoperatively. Four adenocarcinomas were not fluorescent, and immunohistochemistry showed that these adenocarcinomas did not express FRα. Tumor fluorescence was independent of nodule size, uptake of 2-deoxy-2-((18)F)fluoro-D-glucose, histology, and tumor differentiation. Molecular imaging could identify only 7 of the 50 adenocarcinomas in situ in the patient without bisection. The most important predictor of the success of molecular imaging in locating the tumor in situ was the distance of the nodule from the pleural surface.

CONCLUSIONS

Intraoperative molecular imaging with a targeted contrast agent can identify lung adenocarcinomas, and this technology is currently useful in patients with subpleural tumors, irrespective of size. With further refinements, this tool may prove useful in locating adenocarcinomas that are deeper in the lung parenchyma, in lymph nodes, and at pleural and resection margins.

Antibody Positron Emission Tomography Imaging in Anticancer Drug Development

More than 50 monoclonal antibodies (mAbs), including several antibody–drug conjugates, are in advanced clinical development, forming an important part of the many molecularly targeted anticancer therapeutics currently in development. Drug development is a relatively slow and expensive process, limiting the number of drugs that can be brought into late-stage trials. Development decisions could benefit from quantitative biomarkers, enabling visualization of the tissue distribution of (potentially modified) therapeutic mAbs to confirm effective whole-body target expression, engagement, and modulation and to evaluate heterogeneity across lesions and patients. Such biomarkers may be realized with positron emission tomography imaging of radioactively labeled antibodies, a process called immunoPET. This approach could potentially increase the power and value of early trials by improving patient selection, optimizing dose and schedule, and rationalizing observed drug responses. In this review, we summarize the available literature and the status of clinical trials regarding the potential of immunoPET during early anticancer drug development.

Optical innovations in surgery

BACKGROUND

In the past decade, there has been a major drive towards clinical translation of optical and, in particular, fluorescence imaging in surgery. In surgical oncology, radical surgery is characterized by the absence of positive resection margins, a critical factor in improving prognosis. Fluorescence imaging provides the surgeon with reliable and real-time intraoperative feedback to identify surgical targets, including positive tumour margins. It also may enable decisions on the possibility of intraoperative adjuvant treatment, such as brachytherapy, chemotherapy or emerging targeted photodynamic therapy (photoimmunotherapy).

METHODS

This article reviews the use of optical imaging for intraoperative guidance and decision-making.

RESULTS

Image-guided cancer surgery has the potential to be a powerful tool in guiding future surgical care. Photoimmunotherapy is a theranostic concept (simultaneous diagnosis and treatment) on the verge of clinical translation, and is highlighted as an effective combination of image-guided surgery and intraoperative treatment of residual disease. Multispectral optoacoustic tomography, a technique complementary to optical image-guided surgery, is currently being tested in humans and is anticipated to have great potential for perioperative and postoperative application in surgery.

CONCLUSION

Significant advances have been achieved in real-time optical imaging strategies for intraoperative tumour detection and margin assessment. Optical imaging holds promise in achieving the highest percentage of negative surgical margins and in early detection of micrometastastic disease over the next decade.

Bioresponsive probes for molecular imaging: concepts and in vivo applications

Molecular imaging is a powerful tool to visualize and characterize biological processes at the cellular and molecular level in vivo. In most molecular imaging approaches, probes are used to bind to disease-specific biomarkers highlighting disease target sites. In recent years, a new subset of molecular imaging probes, known as bioresponsive molecular probes, has been developed. These probes generally benefit from signal enhancement at the site of interaction with its target. There are mainly two classes of bioresponsive imaging probes. The first class consists of probes that show direct activation of the imaging label (from "off" to "on" state) and have been applied in optical imaging and magnetic resonance imaging (MRI). The other class consists of probes that show specific retention of the imaging label at the site of target interaction and these probes have found application in all different imaging modalities, including photoacoustic imaging and nuclear imaging. In this review, we present a comprehensive overview of bioresponsive imaging probes in order to discuss the various molecular imaging strategies. The focus of the present article is the rationale behind the design of bioresponsive molecular imaging probes and their potential in vivo application for the detection of endogenous molecular targets in pathologies such as cancer and cardiovascular disease.

Application of fluorescence in robotic general surgery: review of the literature and state of the art

The initial use of the indocyanine green fluorescence imaging system was for sentinel lymph node biopsy in patients with breast or colorectal cancer. Since then, application of this method has received wide acceptance in various fields of surgical oncology, and it has become a valid diagnostic tool for guiding cancer treatment. It has also been employed in numerous conventional surgical procedures with much success and benefit to the patient. The advent of minimally invasive surgery brought with it a new use for fluorescence in helping to improve the safety of these procedures, particularly for single-site procedures. In 2010, a near-infrared camera was integrated into the da Vinci Si System, creating a combination of technical and minimally invasive advantages that have been embraced by several experienced surgeons. The use of fluorescence, although useful, is considered challenging. Only a few studies are currently available on the use of fluorescence in robotic general surgery, whereas many articles have focused on its application in open and laparoscopic surgery. Many of these reports describe promising and satisfactory results, although with some shortcomings. The purpose of this article is to review the current status of the use of fluorescence in general surgery and particularly its role in robotic surgery. We also review potential uses in the future.

Lipid-coated polymeric nanoparticles for cancer drug delivery

Polymeric nanoparticles and liposomes have been the platform of choice for nanoparticle-based cancer drug delivery applications over the past decade, but extensive research has revealed their limitations as drug delivery carriers. A hybrid class of nanoparticles, aimed at combining the advantages of both polymeric nanoparticles and liposomes, has received attention in recent years. These core/shell type nanoparticles, frequently referred to as lipid-polymer hybrid nanoparticles (LPNs), possess several characteristics that make them highly suitable for drug delivery. This review introduces the formulation methods used to synthesize LPNs and discusses the strategies used to treat cancer, such as by targeting the tumor microenvironment or vasculature. Finally, it discusses the challenges that must be overcome to realize the full potential of LPNs in the clinic.

Indocyanine green-loaded nanoparticles for image-guided tumor surgery

Detecting positive tumor margins and local malignant masses during surgery is critical for long-term patient survival. The use of image-guided surgery for tumor removal, particularly with near-infrared fluorescent imaging, is a potential method to facilitate removing all neoplastic tissue at the surgical site. In this study we demonstrate a series of hyaluronic acid (HLA)-derived nanoparticles that entrap the near-infrared dye indocyanine green, termed NanoICG, for improved delivery of the dye to tumors. Self-assembly of the nanoparticles was driven by conjugation of one of three hydrophobic moieties: aminopropyl-1-pyrenebutanamide (PBA), aminopropyl-5β-cholanamide (5βCA), or octadecylamine (ODA). Nanoparticle self-assembly, dye loading, and optical properties were characterized. NanoICG exhibited quenched fluorescence that could be activated by disassembly in a mixed solvent. NanoICG was found to be nontoxic at physiologically relevant concentrations and exposure was not found to inhibit cell growth. Using an MDA-MB-231 tumor xenograft model in mice, strong fluorescence enhancement in tumors was observed with NanoICG using a fluorescence image-guided surgery system and a whole-animal imaging system. Tumor contrast with NanoICG was significantly higher than with ICG alone.

Near-infrared fluorescent semiconducting polymer dots with high brightness and pronounced effect of positioning alkyl chains on the comonomers

In recent years, semiconducting polymer dots (Pdots) have emerged as a novel class of extraordinarily bright fluorescent probes with burgeoning applications in bioimaging and sensing. While the desire for near-infrared (NIR)-emitting agents for in vivo biological applications increases drastically, the direct synthesis of semiconducting polymers that can form Pdots with ultrahigh fluorescence brightness is extremely lacking due to the severe aggregation-caused quenching of the NIR chromophores in Pdots. Here we describe the synthesis of dithienylbenzoselenadiazole (DBS)-based NIR-fluorescing Pdots with ultrahigh brightness and excellent photostability. More importantly, the fluorescence quantum yields of these Pdots could be effectively increased by the introduction of long alkyl chains into the thiophene rings of DBS to significantly inhibit the aggregation-caused emission quenching. Additionally, these new series of DBS-based Pdots can be excited by a commonly used 488 nm laser and show a fluorescence quantum yield as high as 36% with a Stokes shift larger than 200 nm. Single-particle analysis indicates that the per-particle brightness of the Pdots is at least 2 times higher than that of the commercial quantum dot (Qdot705) under identical laser excitation and acquisition conditions. We also functionalized the Pdots with carboxylic acid groups and then linked biomolecules to Pdot surfaces to demonstrate their capability for specific cellular labeling without any noticeable nonspecific binding. Our results suggest that these DBS-based NIR-fluorescing Pdots will be very practical in various biological imaging and analytical applications.

GyneScan: an improved online paradigm for screening of ovarian cancer via tissue characterization

Ovarian cancer is the fifth highest cause of cancer in women and the leading cause of death from gynecological cancers. Accurate diagnosis of ovarian cancer from acquired images is dependent on the expertise and experience of ultrasonographers or physicians, and is therefore, associated with inter observer variabilities. Computer Aided Diagnostic (CAD) techniques use a number of different data mining techniques to automatically predict the presence or absence of cancer, and therefore, are more reliable and accurate. A review of published literature in the field of CAD based ovarian cancer detection indicates that many studies use ultrasound images as the base for analysis. The key objective of this work is to propose an effective adjunct CAD technique called GyneScan for ovarian tumor detection in ultrasound images. In our proposed data mining framework, we extract several texture features based on first order statistics, Gray Level Co-occurrence Matrix and run length matrix. The significant features selected using t-test are then used to train and test several supervised learning based classifiers such as Probabilistic Neural Networks (PNN), Support Vector Machine (SVM), Decision Tree (DT), k-Nearest Neighbor (KNN), and Naive Bayes (NB). We evaluated the developed framework using 1300 benign and 1300 malignant images. Using 11 significant features in KNN/PNN classifiers, we were able to achieve 100% classification accuracy, sensitivity, specificity, and positive predictive value in detecting ovarian tumor. Even though more validation using larger databases would better establish the robustness of our technique, the preliminary results are promising. This technique could be used as a reliable adjunct method to existing imaging modalities to provide a more confident second opinion on the presence/absence of ovarian tumor.

[Molecular breast imaging. An update]

CLINICAL/METHODICAL ISSUE

The aim of molecular imaging is to visualize and quantify biological, physiological and pathological processes at cellular and molecular levels. Molecular imaging using various techniques has recently become established in breast imaging.

STANDARD RADIOLOGICAL METHODS

Currently molecular imaging techniques comprise multiparametric magnetic resonance imaging (MRI) using dynamic contrast-enhanced MRI (DCE-MRI), diffusion-weighted imaging (DWI), proton MR spectroscopy ((1)H-MRSI), nuclear imaging by breast-specific gamma imaging (BSGI), positron emission tomography (PET) and positron emission mammography (PEM) and combinations of techniques (e.g. PET-CT and multiparametric PET-MRI).

METHODICAL INNOVATIONS

Recently, novel techniques for molecular imaging of breast tumors, such as sodium imaging ((23)Na-MRI), phosphorus spectroscopy ((31)P-MRSI) and hyperpolarized MRI as well as specific radiotracers have been developed and are currently under investigation.

PRACTICAL RECOMMENDATIONS

It can be expected that molecular imaging of breast tumors will enable a simultaneous assessment of the multiple metabolic and molecular processes involved in cancer development and thus an improved detection, characterization, staging and monitoring of response to treatment will become possible.

H-ferritin-nanocaged doxorubicin nanoparticles specifically target and kill tumors with a single-dose injection

An ideal nanocarrier for efficient drug delivery must be able to target specific cells and carry high doses of therapeutic drugs and should also exhibit optimized physicochemical properties and biocompatibility. However, it is a tremendous challenge to engineer all of the above characteristics into a single carrier particle. Here, we show that natural H-ferritin (HFn) nanocages can carry high doses of doxorubicin (Dox) for tumor-specific targeting and killing without any targeting ligand functionalization or property modulation. Dox-loaded HFn (HFn-Dox) specifically bound and subsequently internalized into tumor cells via interaction with overexpressed transferrin receptor 1 and released Dox in the lysosomes. In vivo in the mouse, HFn-Dox exhibited more than 10-fold higher intratumoral drug concentration than free Dox and significantly inhibited tumor growth after a single-dose injection. Importantly, HFn-Dox displayed an excellent safety profile that significantly reduced healthy organ drug exposure and improved the maximum tolerated dose by fourfold compared with free Dox. Moreover, because the HFn nanocarrier has well-defined morphology and does not need any ligand modification or property modulation it can be easily produced with high purity and yield, which are requirements for drugs used in clinical trials. Thus, these unique properties make the HFn nanocage an ideal vehicle for efficient anticancer drug delivery.

Development and translational imaging of a TP53 porcine tumorigenesis model

Cancer is the second deadliest disease in the United States, necessitating improvements in tumor diagnosis and treatment. Current model systems of cancer are informative, but translating promising imaging approaches and therapies to clinical practice has been challenging. In particular, the lack of a large-animal model that accurately mimics human cancer has been a major barrier to the development of effective diagnostic tools along with surgical and therapeutic interventions. Here, we developed a genetically modified porcine model of cancer in which animals express a mutation in TP53 (which encodes p53) that is orthologous to one commonly found in humans (R175H in people, R167H in pigs). TP53(R167H/R167H) mutant pigs primarily developed lymphomas and osteogenic tumors, recapitulating the tumor types observed in mice and humans expressing orthologous TP53 mutant alleles. CT and MRI imaging data effectively detected developing tumors, which were validated by histopathological evaluation after necropsy. Molecular genetic analyses confirmed that these animals expressed the R167H mutant p53, and evaluation of tumors revealed characteristic chromosomal instability. Together, these results demonstrated that TP53(R167H/R167H) pigs represent a large-animal tumor model that replicates the human condition. Our data further suggest that this model will be uniquely suited for developing clinically relevant, noninvasive imaging approaches to facilitate earlier detection, diagnosis, and treatment of human cancers.

Tumoral reprogramming: Plasticity takes a walk on the wild side

Cellular plasticity is the capacity that cells have to change their fate and adopt a new identity. Plasticity is essential for normal development and for tissue regeneration and, in an experimental setting, for the induction of pluripotency. All these processes involve a reprogramming of the cellular identity, mediated by signals from the environment and/or by internal changes at the transcriptional and epigenetic levels. Tumorigenesis is a process in which normal cells acquire a new malignant identity and give rise to a clonal aberrant population. This is only possible if the initiating cell has the necessary plasticity to undergo such changes, and if the oncogenic event(s) initiating cancer has the essential reprogramming capacity so as to be able to lead a change in cellular identity. The molecular mechanisms underlying tumoral reprogramming are the pathological counterparts of the normal processes regulating developmental plasticity or experimentally-induced reprogramming. In this review we will first revise the main features of non-pathological examples of reprogramming, and then we will describe the parallelisms with tumoral reprogramming, and we will also delineate how the precise knowledge of the reprogramming mechanisms offers the potential for the development of new therapeutical interventions. This article is part of a Special Issue entitled: Stress as a fundamental theme in cell plasticity.

Near-infrared fluorescence imaging of cancer mediated by tumor hypoxia and HIF1α/OATPs signaling axis

Near-infrared fluorescence (NIRF) imaging agents are promising tools for noninvasive cancer imaging. Here, we explored the mechanistic properties of a specific group of NIR heptamethine carbocyanines including MHI-148 dye we identified and synthesized, and demonstrated these dyes to achieve cancer-specific imaging and targeting via a hypoxia-mediated mechanism. We found that cancer cells and tumor xenografts exhibited hypoxia-dependent MHI-148 dye uptake in vitro and in vivo, which was directly mediated by hypoxia-inducible factor 1α (HIF1α). Microarray analysis and dye uptake assay further revealed a group of hypoxia-inducible organic anion-transporting polypeptides (OATPs) responsible for dye uptake, and the correlation between OATPs and HIF1α was manifested in progressive clinical cancer specimens. Finally, we demonstrated increased uptake of MHI-148 dye in situ in perfused clinical tumor samples with activated HIF1α/OATPs signaling. Our results establish these NIRF dyes as potential tumor hypoxia-dependent cancer-targeting agents and provide a mechanistic rationale for continued development of NIRF imaging agents for improved cancer detection, prognosis and therapy.

Preclinical comparison of near-infrared-labeled cetuximab and panitumumab for optical imaging of head and neck squamous cell carcinoma

PURPOSE

Though various targets have been proposed and evaluated, no agent has yet been investigated in a clinical setting for head and neck cancer. The present study aimed to compare two fluorescently labeled anti-epidermal growth factor receptor (EGFR) antibodies for detection of head and neck squamous cell carcinoma (HNSCC).

PROCEDURES

Antigen specificities and in vitro imaging of the fluorescently labeled anti-EGFR antibodies were performed. Next, immunodeficient mice (n = 22) bearing HNSCC (OSC-19 and SCC-1) tongue tumors received systemic injections of cetuximab-IRDye800CW, panitumumab-IRDye800CW, or IgG-IRDye800CW (a nonspecific control). Tumors were imaged and resected using two near-infrared imaging systems, SPY and Pearl. Fluorescent lymph nodes were also identified, and all resected tissues were sent for pathology.

RESULTS

Panitumumab-IRDye800CW and cetuximab-IRDye800CW had specific and high affinity binding for EGFR (K D = 0.12 and 0.31 nM, respectively). Panitumumab-IRDye800CW demonstrated a 2-fold increase in fluorescence intensity compared to cetuximab-IRDye800CW in vitro. In vivo, both fluorescently labeled antibodies produced higher tumor-to-background ratios compared to IgG-IRDye800CW. However, there was no significant difference between the two in either cell line or imaging modality (OSC-19: p = 0.08 SPY, p = 0.48 Pearl; SCC-1: p = 0.77 SPY, p = 0.59 Pearl; paired t tests).

CONCLUSIONS

There was no significant difference between the two fluorescently labeled anti-EGFR monoclonal antibodies in murine models of HNSCC. Both cetuximab and panitumumab can be considered suitable targeting agents for fluorescent intraoperative detection of HNSCC.

Sensitivity of photoacoustic microscopy

Building on its high spatial resolution, deep penetration depth and excellent image contrast, 3D photoacoustic microscopy (PAM) has grown tremendously since its first publication in 2005. Integrating optical excitation and acoustic detection, PAM has broken through both the optical diffusion and optical diffraction limits. PAM has 100% relative sensitivity to optical absorption (i.e., a given percentage change in the optical absorption coefficient yields the same percentage change in the photoacoustic amplitude), and its ultimate detection sensitivity is limited only by thermal noise. Focusing on the engineering aspects of PAM, this Review discusses the detection sensitivity of PAM, compares the detection efficiency of different PAM designs, and summarizes the imaging performance of various endogenous and exogenous contrast agents. It then describes representative PAM applications with high detection sensitivity, and outlines paths to further improvement.

Rare Earth Nanoprobes for Functional Biomolecular Imaging and Theranostics

Contrast agents designed to visualize the molecular mechanisms underlying cancer pathogenesis and progression have deepened our understanding of disease complexity and accelerated the development of enhanced drug strategies targeted to specific biochemical pathways. For the next generation probes and imaging systems to be viable, they must exhibit enhanced sensitivity and robust quantitation of morphologic and contrast features, while offering the ability to resolve the disease-specific molecular signatures that may be critical to reconstitute a more comprehensive portrait of pathobiology. This feature article provides an overview on the design and advancements of emerging biomedical optical probes in general and evaluates the promise of rare earth nanoprobes, in particular, for molecular imaging and theranostics. Combined with new breakthroughs in nanoscale probe configurations, and improved dopant compositions, and multimodal infrared optical imaging, rare-earth nanoprobes can be used to address a wide variety of biomedical challenges, including deep tissue imaging, real-time drug delivery tracking and multispectral molecular profiling.

Detection and cellular imaging of human cancer enzyme using a turn-on, wavelength-shiftable, self-immolative profluorophore

A frontier area in the development of activatable (turn-on) fluorescence-based probes is that concerned with rapid and selective stimulus triggering of probe activation so as to allow for biomarker identification and cellular imaging. The work here is concerned with a cloaked fluorophore composed of a reporter whose fluorescence is efficiently quenched by it being bound to an activatable trigger group through a novel self-immolative linker. Highly selective and rapid activation of the trigger group is achieved by chemical and enzymatic means that result in activated trigger group detachment from the self-immolative linker, with the latter subsequently cleaved from the reporter autonomously, thereby unmasking intense, red-shifted fluorescence emission. To achieve this success, we used a trimethyl-locked quinone propionic acid trigger group and an N-methyl-p-aminobenzyl alcohol self-immolative linker attached to the reporter. Delineated here are the synthesis and characterization of this cloaked fluorophore and the evaluation of its triggered turning on in the presence of an up-regulated enzyme in human cancer cells, NAD(P)H:quinone oxidoreductase-1 (NQO1, DT-diaphorase, EC 1.6.99.2).

Fluorescent-tilmanocept for tumor margin analysis in the mouse model

BACKGROUND

Dendritic cells (DC) are localized in close proximity to cancer cells in many well-known tumors, and thus maybe a useful target for tumor margin assessment.

MATERIALS AND METHODS

[(99m)Tc]- cyanine 7 (Cy7)-tilmanocept was synthesized and in vitro binding assays to bone marrow-derived DC were performed. Fifteen mice, implanted with either 4T1 mouse mammary or K1735 mouse melanoma tumors, were administered 1.0 nmol of [(99m)Tc]-Cy7-tilmanocept via tail vein injection. After fluorescence imaging 1 or 2 h after injection, the tumor, muscle, and blood were assayed for radioactivity to calculate percent-injected dose. Digital images of the tumors after immunohistochemical staining for DC were analyzed to determine DC density.

RESULTS

In vitro binding demonstrated subnanomolar affinity of [(99m)Tc]-Cy7-tilmanocept to DC (KA = 0.31 ± 0.11 nM). After administration of [(99m)Tc]-Cy7-tilmanocept, fluorescence imaging showed a 5.5-fold increase in tumor signal as compared with preinjection images and a 3.3-fold difference in fluorescence activity when comparing the tumor with the surgical bed after tumor excision. Immunohistochemical staining analysis demonstrated that DC density positively correlated with tumor percent of injected dose per gram (r = 0.672, P = 0.03), and higher DC density was observed at the periphery versus center of the tumor (186 ± 54 K versus 64 ± 16 K arbitrary units, P = 0.001).

CONCLUSIONS

[(99m)Tc]-Cy7-tilmanocept exhibits in vitro and in vivo tumor-specific binding to DC and maybe useful as a tumor margin targeting agent.

Targeted imaging of α(v)β(3) expressing sarcoma tumor cells in vivo in pre-operative setting using near infrared: a potential tool to reduce incomplete surgical resection

Tumor size and location along with efficacy of pre-operative imaging are limiting factors for optimal surgical excision for osteosarcoma. Our general hypothesis is that targeting αvβ3 integrin-rich osteosarcoma neoangiogenesis should provide improved delivery of diagnostic compounds and assist surgeons intra operatively using near-infrared imaging techniques. We evaluated in an orthotopic metastatic osteosarcoma in rats the potential of AngioStamp™ targeting αvβ3 integrins and detected intra operatively by near infrared (NIR) illumination (Fluobeam™) as a novel, intra operative imaging technique. To determine the potential of this association in improving tumor and metastasis detection, we compared the quality and sensitivity of tumor/metastasis margin delineation and tumor resection using intra-operative NIR imaging to the ones guided by pre-operative imaging (i.e., MRI subsequently confirmed by histopathological analysis). Chemotherapy being essential in osteosarcoma treatment, we evaluated the capacity of AngioStamp™ to specifically localize to the tumor after chemotherapy treatment. We showed a significantly lesser extent of healthy tissue resection after surgical excision when assessing tumor margin intra operatively using AngioStamp™/Fluobeam™ association compared to pre-operative MRI post-operatively confirmed by histopathological analysis (p<0.01). Importantly, intra-operative NIR illumination of lungs revealed more metastases than were detected by CT Scan or under intra-operative white light examination (p<0.01). Importantly, chemotherapy did not alter AngioStamp™ tumor specific targeting nor the sensitivity of tumor detection. Our preclinical data confirm the potential of intra-operative imaging for improved primary tumor and lung metastasis excision. Based on these promising results, we now propose to evaluate this approach as a mean to improve surgical excision while maintaining tumor control in other sarcoma or tumors overexpressing αvβ3 integrins.

Polydiacetylene-enclosed near-infrared fluorescent semiconducting polymer dots for bioimaging and sensing

Semiconducting polymer dots (P-dots) recently have emerged as a new type of ultrabright fluorescent probe with promising applications in biological imaging and detection. With the increasing desire for near-infrared (NIR) fluorescing probes for in vivo biological measurements, the currently available NIR-emitting P-dots are very limited and the leaching of the encapsulated dyes/polymers has usually been a concern. To address this challenge, we first embedded the NIR dyes into the matrix of poly[(9,9-dioctylfluorene)-co-2,1,3-benzothiadiazole-co-4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole] (PF-BT-DBT) polymer and then enclosed the doped P-dots with polydiacetylenes (PDAs) to avoid potential leakage of the entrapped NIR dyes from the P-dot matrix. These PDA-enclosed NIR-emitting P-dots not only emitted much stronger NIR fluorescence than conventional organic molecules but also exhibited enhanced photostability over CdTe quantum dots, free NIR dyes, and gold nanoclusters. We next conjugated biomolecules onto the surface of the resulting P-dots and demonstrated their capability for specific cellular labeling without any noticeable nonspecific binding. To employ this new class of material as a facile sensing platform, an easy-to-prepare test paper, obtained by soaking the paper into the PDA-enclosed NIR-emitting P-dot solution, was used to sense external stimuli such as ions, temperature, or pH, depending on the surface functionalization of PDAs. We believe these PDA-coated NIR-fluorescing P-dots will be very useful in a variety of bioimaging and analytical applications.

Minibody-indocyanine green based activatable optical imaging probes: the role of short polyethylene glycol linkers

Minibodies show rapider blood clearance than IgGs due to smaller size that improves target-to-background ratio (TBR) in in vivo imaging. Additionally, the ability to activate an optical probe after binding to the target greatly improves the TBR. An optical imaging probe based on a minibody against prostate-specific membrane antigen (PSMA-MB) and conjugated with an activatable fluorophore, indocyanine green (ICG), was designed to fluoresce only after binding to cell-surface PSMA. To further reduce background signal, short polyethylene glycol (PEG) linkers were employed to improve the covalent bonding ratio of ICG. New PSMA-MBs conjugated with bifunctional ICG derivatives specifically visualized PSMA-positive tumor xenografts in mice bearing both PSMA-positive and -negative tumors within 6 h postinjection. The addition of short PEG linkers significantly improved TBRs; however, it did not significantly alter the biodistribution. Thus, minibody-ICG conjugates could be a good alternative to IgG-ICG in the optical cancer imaging for further clinical applications.

Polymeric micelles for apoptosis-targeted optical imaging of cancer and intraoperative surgical guidance

In a two-step strategy, an intraperitoneal (IP) injection of poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) micelles containing paclitaxel (PTX), cyclopamine (CYP), and gossypol (GSP) at 30, 30, and 30 mg/kg, respectively, debulked tumor tissues by 1.3-fold, based on loss of bioluminescence with <10% body weight change, and induced apoptosis in peritoneal tumors when used as neoadjuvant chemotherapy (NACT) in an ES-2-luc-bearing xenograft model for ovarian cancer. In a second step, a single intravenous (IV) injection of apoptosis-targeting GFNFRLKAGAKIRFGS-PEG-b-PCL micelles containing a near-infrared (NIR) fluorescence probe, DiR (1,1′-dioctadecyltetramethyl indotricarbocyanine iodide), resulted in increased peritoneal DiR accumulation in apoptosis-induced ES-2-luc tumor tissues (ex vivo) by 1.5-fold compared with DiR molecules delivered by methoxy PEG-b-PCL micelles (non-targeted) at 48 h after IV injection in a second step. As a result, a tandem of PEG-b-PCL micelles enabled high-resolution detection of ca. 1 mm diameter tumors, resulting in resection of approximately 90% of tumors, and a low peritoneal cancer index (PCI) of ca. 7. Thus, a tandem of PEG-b-PCL micelles used for NCAT and NIR fluorescence imaging of therapy-induced apoptosis for intraoperative surgical guidance may be a promising treatment strategy for metastatic ovarian cancer.

Near-infrared fluorescence molecular imaging of ductal carcinoma in situ with CD44v6-specific antibodies in mice: a preclinical study

Purpose

The purpose of this study was to develop a molecular imaging technique using tracers specific for ductal carcinoma in situ (DCIS) to improve visualization and localization of DCIS during surgery. As CD44v6 is frequently expressed in DCIS, we used near-infrared fluorescently labeled CD44v6-targeting antibodies for detection of DCIS.

Procedure

Mice bearing orthotopically transplanted CD44v6-positive MCF10DCIS DCIS-like tumors and CD44v6-negative MDA-MB-231 control tumors were intravenously injected with IRDye800CW conjugated to CD44v6-specific antibodies or control IgGs. Noninvasive imaging was performed for 8 days postinjection, followed by intraoperative imaging. Antibody accumulation and intratumor distribution were examined.

Results

Maximum accumulation of CD44v6-specific antibodies was obtained 24 h postinjection. Maximum tumor-to-background ratio for MCF10DCIS tumors was 4.5 ± 0.2, compared to 1.4 ± 0.1 (control tumors, p = 0.006), and 1.7 ± 0.1 (control IgG, p = 0.014), for 8 days postinjection. Ex vivo, tumor-to-background ratios were comparable to those obtained by intraoperative imaging.

Conclusions

We show the applicability of noninvasive and intraoperative optical imaging of DCIS-like lesions in vivo using CD44v6-specific antibodies.

MarginProbe: intraoperative margin assessment during breast conserving surgery by using radiofrequency spectroscopy

In breast conserving surgery, the tumor should be removed with a clean margin, a rim of healthy tissue surrounding. Failure to achieve clean margins in the initial surgery results in a re-excision procedure. Re-excision rates are reported as being 11-46% for invasive carcinoma and ductal carcinoma in situ (DCIS). Re-excisions can have negative consequences such as increased postoperative infections, negative impact on cosmesis, patient anxiety and increased medical costs. Therefore, the surgical margin of invasive and intraductal (DCIS) breast tissue is a subject of intense discussion. Different options for intraoperative assessment are available, but all in all, they are unsatisfying. Frozen section margin examination is possible but is time consuming and restricted to the assessment of invasive carcinoma. In the case of DCIS, there is no procedure for intraoperative margin assessment. Thus, a solution for efficient intraoperative surgical margin assessment is needed. For this purpose, an innovative, real-time, intraoperative margin-assessment device (MarginProbe, Dune Medical Devices, Caesarea, Israel) was designed, and recent published clinical data reported a reduction of re-excisions by more than 50%.

Radiolabeling strategies for tumor-targeting proteinaceous drugs

Owing to their large size proteinaceous drugs offer higher operative information content compared to the small molecules that correspond to the traditional understanding of druglikeness. As a consequence these drugs allow developing patient-specific therapies that provide the means to go beyond the possibilities of current drug therapy. However, the efficacy of these strategies, in particular "personalized medicine", depends on precise information about individual target expression rates. Molecular imaging combines non-invasive imaging methods with tools of molecular and cellular biology and thus bridges current knowledge to the clinical use. Moreover, nuclear medicine techniques provide therapeutic applications with tracers that behave like the diagnostic tracer. The advantages of radioiodination, still the most versatile radiolabeling strategy, and other labeled compounds comprising covalently attached radioisotopes are compared to the use of chelator-protein conjugates that are complexed with metallic radioisotopes. With the techniques using radioactive isotopes as a reporting unit or even the therapeutic principle, care has to be taken to avoid cleavage of the radionuclide from the protein it is linked to. The tracers used in molecular imaging require labeling techniques that provide site specific conjugation and metabolic stability. Appropriate choice of the radionuclide allows tailoring the properties of the labeled protein to the application required. Until the event of positron emission tomography the spectrum of nuclides used to visualize cellular and biochemical processes was largely restricted to iodine isotopes and 99m-technetium. Today, several nuclides such as 18-fluorine, 68-gallium and 86-yttrium have fundamentally extended the possibilities of tracer design and in turn caused the need for the development of chemical methods for their conjugation.

Application of a novel near infrared-fluorescence giant vesicle- and polymerasome-based tissue marker for endoscopic and laparoscopic navigation

In this study, we describe the development of a novel tissue marker that can be injected from within the digestive tract by using an endoscopic instrument, and visualized using near-infrared (NIR) fluorescence imaging. The marker was prepared in three steps, (i) mixing NIR-fluorescent indocyanine green (ICG) with giant vesicles (GVs) of lecithin, (ii) suspending the ICG-containing giant vesicles (ICG-GV) in an oil phase dissolving polyglycerol-polyricinoleate (PGPR), and (iii) centrifugation of the suspension layered on a buffered solution to obtain a giant polymer vesicle (polymerasome) containing ICG-GV. We injected the tissue marker into the inner gastric surface of an anesthetized pig using an endoscopic syringe, and observed the injection site using a fluorescence laparoscopic camera. The diameter of the spot blur was approximately 2 cm over a 5-h period, demonstrating the utility of this procedure as a tissue marker for tumor marking, and suggesting its potential for assisting navigation during surgical procedures.

Fluorescence-lifetime molecular imaging can detect invisible peritoneal ovarian tumors in bloody ascites

Blood contamination, such as bloody ascites or hemorrhages during surgery, is a potential hazard for clinical application of fluorescence imaging. In order to overcome this problem, we investigate if fluorescence-lifetime imaging helps to overcome this problem. Samples were prepared at concentrations ranging 0.3-2.4 μm and mixed with 0-10% of blood. Fluorescence intensities and lifetimes of samples were measured using a time-domain fluorescence imager. Ovarian cancer SHIN3 cells overexpressing the D-galactose receptor were injected into the peritoneal cavity 2.5 weeks before the experiments. Galactosyl serum albumin-rhodamine green (GSA-RhodG), which bound to the D-galactose receptor and was internalized thereafter, was administered intraperitoneally to peritoneal ovarian cancer-bearing mice with various degrees of bloody ascites. In vitro study showed a linear correlation between fluorescence intensity and probe concentration (r(2) > 0.99), whereas the fluorescence lifetime was consistent (range, 3.33 ± 0.15-3.75 ± 0.04 ns). By adding 10% of blood to samples, fluorescence intensities decreased to <1%, while fluorescence lifetimes were consistent. In vivo fluorescence lifetime of GSA-RhodG stained tumors was longer than the autofluorescence lifetime (threshold, 2.87 ns). Tumor lesions under hemorrhagic peritonitis were not depicted using fluorescence intensity imaging; however, fluorescence-lifetime imaging clearly detected tumor lesions by prolonged lifetimes. In conclusion, fluorescence-lifetime imaging with GSA-RhodG depicted ovarian cancer lesions, which were invisible in intensity images, in hemorrhagic ascites.

Multifunctional gold coated thermo-sensitive liposomes for multimodal imaging and photo-thermal therapy of breast cancer cells

Plasmon resonant gold nanoparticles of various sizes and shapes have been extensively researched for their applications in imaging, drug delivery and photothermal therapy (PTT). However, their ability to degrade after performing the required function is essential for their application in healthcare. When combined with biodegradable liposomes, they appear to have better degradation capabilities. They degrade into smaller particles of around 5 nm that are eligible candidates for renal clearance. Distearoyl phosphatidyl choline : cholesterol (DSPC : CHOL, 8 : 2 wt%) liposomes have been synthesized and coated with gold by in situ reduction of chloro-auric acid. These particles of size 150-200 nm are analyzed for their stability, degradation capacity, model drug-release profile, biocompatibility and photothermal effects on cancer cells. It is observed that when these particles are subjected to low power continuous wave near infra-red (NIR) laser for more than 10 min, they degrade into small gold nanoparticles of size 5 nm. Also, the gold coated liposomes appear to have excellent biocompatibility and high efficiency to kill cancer cells through photothermal transduction. These novel materials are also useful in imaging using specific NIR dyes, thus exhibiting multifunctional properties for theranostics of cancer.

An intracellularly activatable, fluorogenic probe for cancer imaging

A newly designed, dual-functional probe based on intracellular activation has been successfully developed for the detection of cancer cells.

Target-to-background enhancement in multispectral endoscopy with background autofluorescence mitigation for quantitative molecular imaging

Fluorescence molecular imaging with exogenous probes improves specificity for the detection of diseased tissues by targeting unambiguous molecular signatures. Additionally, increased diagnostic sensitivity is expected with the application of multiple molecular probes. We developed a real-time multispectral fluorescence-reflectance scanning fiber endoscope (SFE) for wide-field molecular imaging of fluorescent dye-labeled molecular probes at nanomolar detection levels. Concurrent multichannel imaging with the wide-field SFE also allows for real-time mitigation of the background autofluorescence (AF) signal, especially when fluorescein, a U.S. Food and Drug Administration approved dye, is used as the target fluorophore. Quantitative tissue AF was measured for the ex vivo porcine esophagus and murine brain tissues across the visible and nearinfrared spectra. AF signals were then transferred to the unit of targeted fluorophore concentration to evaluate the SFE detection sensitivity for sodium fluorescein and cyanine. Next, we demonstrated a real-time AF mitigation algorithm on a tissue phantom, which featured molecular probe targeted cells of high-grade dysplasia on a substrate containing AF species. The target-to-background ratio was enhanced by more than one order of magnitude when applying the real-time AF mitigation algorithm. Furthermore, a quantitative estimate of the fluorescein photodegradation (photobleaching) rate was evaluated and shown to be insignificant under the illumination conditions of SFE. In summary, the multichannel laser-based flexible SFE has demonstrated the capability to provide sufficient detection sensitivity, image contrast, and quantitative target intensity information for detecting small precancerous lesions in vivo.

Gold nanorods for optimized photothermal therapy: the influence of irradiating in the first and second biological windows

The absorption efficiencies of gold nanorods working in the first and second biological windows are investigated.

Magnetic PEGylated Pt3Co nanoparticles as a novel MR contrast agent: in vivo MR imaging and long-term toxicity study

Magnetic resonance (MR) imaging using magnetic nanoparticles as the contrast agent has been extensively explored in biomedical imaging and disease diagnosis. Herein, we develop biocompatible polymer coated ultra-small Pt3Co magnetic nanoparticles as a new T2-weighted MR imaging contrast agent. A unique class of alloy Pt3Co nanoparticles is synthesized through a thermal decomposition method. After being modified with polyethylene glycol (PEG), the obtained Pt3Co-PEG nanoparticles exhibit an extremely high T2-weighted relaxivity rate (r2) up to 451.2 mM s(-1), which is much higher than that of Resovist®, a commercial T2-MR contrast agent used in the clinic. In vitro experiments indicate no obvious cytotoxicity of Pt3Co-PEG nanoparticles to various cell lines. After intravenous injection of Pt3Co-PEG nanoparticles, in vivo T2-weighted MR imaging of tumor-bearing mice reveals strong tumor contrast, which is much higher than that offered by injecting Resovist®. We further study the long-term biodistribution and toxicology of this new type of MR contrast nanoparticles after intravenous injection into healthy mice. Despite the significant retention of Pt3Co-PEG nanoparticles in the mouse liver and spleen, no appreciable toxicity of these nanoparticles to the treated animals has been noted in our detailed histological and hematological analysis over a course of 60 days. Our work demonstrates that functionalized Pt3Co nanoparticles may be a promising new type of T2-weighted MR contrast agent potentially useful in biomedical imaging and diagnosis.

Biofunctionalized gadolinium-containing prussian blue nanoparticles as multimodal molecular imaging agents

Molecular imaging agents enable the visualization of phenomena with cellular and subcellular level resolutions and therefore have enormous potential in improving disease diagnosis and therapy assessment. In this article, we describe the synthesis, characterization, and demonstration of core-shell, biofunctionalized, gadolinium-containing Prussian blue nanoparticles as multimodal molecular imaging agents. Our multimodal nanoparticles combine the advantages of MRI and fluorescence. The core of our nanoparticles consists of a Prussian blue lattice with gadolinium ions located within the lattice interstices that confer high relaxivity to the nanoparticles providing MRI contrast. The relaxivities of our nanoparticles are nearly nine times those observed for the clinically used Magnevist. The nanoparticle MRI core is biofunctionalized with a layer of fluorescently labeled avidin that enables fluorescence imaging. Biotinylated antibodies are attached to the surface avidin and confer molecular specificity to the nanoparticles by targeting cell-specific biomarkers. We demonstrate our nanoparticles as multimodal molecular imaging agents in an in vitro model consisting of a mixture of eosinophilic cells and squamous epithelial cells. Our nanoparticles specifically detect eosinophilic cells and not squamous epithelial cells, via both fluorescence imaging and MRI in vitro. These results suggest the potential of our biofunctionalized Prussian blue nanoparticles as multimodal molecular imaging agents in vivo.

Evaluation of a cholecystokinin 2 receptor-targeted near-infrared dye for fluorescence-guided surgery of cancer

Surgical resection of malignant disease remains one of the most effective tools for treating cancer. Tumor-targeted near-infrared dyes have the potential to improve contrast between normal and malignant tissues, thereby enabling surgeons to more quantitatively resect malignant disease. Because the cholecystokinin 2 receptor (CCK2R and its tumor-specific splice variant CCK2i4svR) is overexpressed in cancers of the lungs, colon, thyroid, pancreas, and stomach, but absent or inaccessible to parenterally administered drugs in most normal tissues, we have undertaken to design a targeting ligand that can deliver attached near-infrared dyes to CCK2R+ tumors. We report here the synthesis and biological characterization of a CCK2R-targeted conjugate of the near-infrared dye, LS-288 (CRL-LS288). We demonstrate that CRL-LS288 binds selectively to CCK2R+ cancer cells with low nanomolar affinity (Kd = 7 × 10(-9) M). We further show that CRL-LS288 localizes primarily to CCK2R-expressing HEK 293 murine tumor xenografts and that dye uptake in these xenografts is significantly reduced when CCK2R are blocked by preinjection of excess ligand (CRL) or when mice are implanted with CCK2R-negative tumors. Because CRL-LS288 is also found to reveal the locations of distant tumor metastases, we suggest that CRL-LS288 has the potential to facilitate intraoperative identification of malignant disease during a variety of cancer debulking surgeries.

Intraoperative fluorescence delineation of head and neck cancer with a fluorescent anti-epidermal growth factor receptor nanobody

Intraoperative near-infrared (NIR) fluorescence imaging is a technology with high potential to provide the surgeon with real-time visualization of tumors during surgery. Our study explores the feasibility for clinical translation of an epidermal growth factor receptor (EGFR)-targeting nanobody for intraoperative imaging and resection of orthotopic tongue tumors and cervical lymph node metastases. The anti-EGFR nanobody 7D12 and the negative control nanobody R2 were conjugated to the NIR fluorophore IRDye800CW (7D12-800CW and R2-800CW). Orthotopic tongue tumors were induced in nude mice using the OSC-19-luc2-cGFP cell line. Tumor-bearing mice were injected with 25 µg 7D12-800CW, R2-800CW or 11 µg 800CW. Subsequently, other mice were injected with 50 or 75 µg of 7D12-800CW. The FLARE imaging system and the IVIS spectrum were used to identify, delineate and resect the primary tumor and cervical lymph node metastases. All tumors could be clearly identified using 7D12-800CW. A significantly higher tumor-to-background ratio (TBR) was observed in mice injected with 7D12-800CW compared to mice injected with R2-800CW and 800CW. The highest average TBR (2.00 ± 0.34 and 2.72 ± 0.17 for FLARE and IVIS spectrum, respectively) was observed 24 hr after administration of the EGFR-specific nanobody. After injection of 75 µg 7D12-800CW cervical lymph node metastases could be clearly detected. Orthotopic tongue tumors and cervical lymph node metastases in a mouse model were clearly identified intraoperatively using a recently developed fluorescent EGFR-targeting nanobody. Translation of this approach to the clinic would potentially improve the rate of radical surgical resections.

Novel cancer-targeting SPECT/NIRF dual-modality imaging probe (99m)Tc-PC-1007: synthesis and biological evaluation

Synthesis, characterization, in vitro and in vivo biological evaluation of a heptamethine cyanine based dual-mode single-photon emission computed tomography (SPECT)/near infrared fluorescence (NIRF) imaging probe (99m)Tc-PC-1007 is described. (99m)Tc-PC-1007 exhibited preferential accumulation in human breast cancer MCF-7 cells. Cancer-specific SPECT/CT and NIRF imaging of (99m)Tc-PC-1007 was performed in a breast cancer xenograft model. The probe uptake ratio of tumor to control (spinal cord) was calculated to be 4.02±0.56 at 6 h post injection (pi) and 8.50±1.41 at 20 h pi (P<0.0001). Pharmacokinetic parameters such as blood clearance and organ distribution were assessed.

The potential of hypoxia markers as target for breast molecular imaging--a systematic review and meta-analysis of human marker expression

Background

Molecular imaging of breast cancer is a promising emerging technology, potentially able to improve clinical care. Valid imaging targets for molecular imaging tracer development are membrane-bound hypoxia-related proteins, expressed when tumor growth outpaces neo-angiogenesis. We performed a systematic literature review and meta-analysis of such hypoxia marker expression rates in human breast cancer to evaluate their potential as clinically relevant molecular imaging targets.

Methods

We searched MEDLINE and EMBASE for articles describing membrane-bound proteins that are related to hypoxia inducible factor 1α (HIF-1α), the key regulator of the hypoxia response. We extracted expression rates of carbonic anhydrase-IX (CAIX), glucose transporter-1 (GLUT1), C-X-C chemokine receptor type-4 (CXCR4), or insulin-like growth factor-1 receptor (IGF1R) in human breast disease, evaluated by immunohistochemistry. We pooled study results using random-effects models and applied meta-regression to identify associations with clinicopathological variables.

Results

Of 1,705 identified articles, 117 matched our selection criteria, totaling 30,216 immunohistochemistry results. We found substantial between-study variability in expression rates. Invasive cancer showed pooled expression rates of 35% for CAIX (95% confidence interval (CI): 26-46%), 51% for GLUT1 (CI: 40-61%), 46% for CXCR4 (CI: 33-59%), and 46% for IGF1R (CI: 35-70%). Expression rates increased with tumor grade for GLUT1, CAIX, and CXCR4 (all p < 0.001), but decreased for IGF1R (p < 0.001). GLUT1 showed the highest expression rate in grade III cancers with 58% (45-69%). CXCR4 showed the highest expression rate in small T1 tumors with 48% (CI: 28-69%), but associations with size were only significant for CAIX (p < 0.001; positive association) and IGF1R (p = 0.047; negative association). Although based on few studies, CAIX, GLUT1, and CXCR4 showed profound lower expression rates in normal breast tissue and benign breast disease (p < 0.001), and high rates in carcinoma in situ. Invasive lobular carcinoma consistently showed lower expression rates (p < 0.001).

Conclusions

Our results support the potential of hypoxia-related markers as breast cancer molecular imaging targets. Although specificity is promising, combining targets would be necessary for optimal sensitivity. These data could help guide the choice of imaging targets for tracer development depending on the envisioned clinical application.