Intraoperative tumor-specific fluorescence imaging in ovarian cancer by folate receptor-α targeting: first in-human results

Enriching the interventional vision of cancer with fluorescence and optoacoustic imaging

Among several techniques considered for surgical and endoscopic imaging, novel optical methods are evolving as a promising approach for interventional guidance. Pilot clinical applications of fluorescence molecular imaging have demonstrated the benefits of using targeted fluorescent agents in cancer surgery. This premise can be extended broadly to interventional guidance through an increasing number of targeted agents and detection techniques. Beyond epi-illumination fluorescence imaging, optoacoustic (photoacoustic) methods are emerging to offer high-resolution cross-sectional optical imaging through several millimeters to centimeters of depth. We present an overview of key recent developments in optical interventional imaging and outline the potential for a paradigm shift in surgical and endoscopic visualization.

Noise suppressed, multifocus image fusion for enhanced intraoperative navigation

Current intraoperative imaging systems are typically not able to provide 'sharp' images over entire large areas or entire organs. Distinct structures such as tissue margins or groups of malignant cells are therefore often difficult to detect, especially under low signal-to-noise-ratio conditions. In this report, we introduce a noise suppressed multifocus image fusion algorithm, that provides detailed reconstructions even when images are acquired under sub-optimal conditions, such is the case for real time fluorescence intraoperative surgery. The algorithm makes use of the Anscombe transform combined with a multi-level stationary wavelet transform with individual threshold-based shrinkage. While the imaging system is integrated with a respiratory monitor triggering system, it can be easily adapted to any commercial imaging system. The developed algorithm is made available as a plugin for Osirix.

Folate-receptor 1 (FOLR1) protein is elevated in the serum of ovarian cancer patients

OBJECTIVES

Ovarian cancer is the most lethal gynecological malignancy in North America. Although survival rates are high when the disease is diagnosed at an early stage, this decreases exponentially in late-stage diagnoses. As such, there is a need for novel early detection biomarkers. Through an integrated approach to ovarian cancer biomarker discovery that combines proteomics with transcriptomics and bioinformatics, our laboratory has identified folate-receptor 1 (FOLR1) and Dickkopf-related protein 3 (Dkk-3) as putative biomarkers. The objective of this study was to measure the levels of FOLR1 and Dkk-3 in the serum of patients with ovarian cancer, benign gynecological conditions and healthy women.

DESIGN AND METHODS

FOLR1 and Dkk-3 were analyzed in serum of 100 ovarian cancer patients, 100 patients with benign gynecological conditions, and 100 healthy women using enzyme-linked immunosorbent assays (ELISAs). All specimens were analyzed in triplicate.

RESULTS

FOLR1 was significantly elevated in the serum of ovarian cancer patients compared to serum of both healthy controls (P<0.0001) and patients with benign gynecological conditions (P<0.0001). Furthermore, FOLR1 was strongly correlated with CA125 as both were elevated in the serous histotype and in late-stage disease. FOLR1 did not outperform CA125 in receiver operating characteristic curve analysis and there was no significant complementarity between the two markers. Dkk-3 was not significantly different between the three serum cohorts and was not correlated with CA125.

CONCLUSIONS

FOLR1 is a new biomarker for ovarian cancer which correlates closely with CA125. The role of FOLR1 in the pathogenesis of ovarian cancer warrants further investigation.

Folate-receptor 1 (FOLR1) protein is elevated in the serum of ovarian cancer patients

OBJECTIVES

Ovarian cancer is the most lethal gynecological malignancy in North America. Although survival rates are high when the disease is diagnosed at an early stage, this decreases exponentially in late-stage diagnoses. As such, there is a need for novel early detection biomarkers. Through an integrated approach to ovarian cancer biomarker discovery that combines proteomics with transcriptomics and bioinformatics, our laboratory has identified folate-receptor 1 (FOLR1) and Dickkopf-related protein 3 (Dkk-3) as putative biomarkers. The objective of this study was to measure the levels of FOLR1 and Dkk-3 in the serum of patients with ovarian cancer, benign gynecological conditions and healthy women.

DESIGN AND METHODS

FOLR1 and Dkk-3 were analyzed in serum of 100 ovarian cancer patients, 100 patients with benign gynecological conditions, and 100 healthy women using enzyme-linked immunosorbent assays (ELISAs). All specimens were analyzed in triplicate.

RESULTS

FOLR1 was significantly elevated in the serum of ovarian cancer patients compared to serum of both healthy controls (P<0.0001) and patients with benign gynecological conditions (P<0.0001). Furthermore, FOLR1 was strongly correlated with CA125 as both were elevated in the serous histotype and in late-stage disease. FOLR1 did not outperform CA125 in receiver operating characteristic curve analysis and there was no significant complementarity between the two markers. Dkk-3 was not significantly different between the three serum cohorts and was not correlated with CA125.

CONCLUSIONS

FOLR1 is a new biomarker for ovarian cancer which correlates closely with CA125. The role of FOLR1 in the pathogenesis of ovarian cancer warrants further investigation.

Self-luminescing BRET-FRET near-infrared dots for in vivo lymph-node mapping and tumour imaging

Strong autofluorescence from living tissues, and the scattering and absorption of short-wavelength light in living tissues, significantly reduce sensitivity of in vivo fluorescence imaging. These issues can be tackled by using imaging probes that emit in the near-infrared wavelength range. Here we describe self-luminescing near-infrared-emitting nanoparticles employing an energy transfer relay that integrates bioluminescence resonance energy transfer and fluorescence resonance energy transfer, enabling in vivo near-infrared imaging without external light excitation. Nanoparticles were 30-40 nm in diameter, contained no toxic metals, exhibited long circulation time and high serum stability, and produced strong near-infrared emission. Using these nanoparticles, we successfully imaged lymphatic networks and vasculature of xenografted tumours in living mice. The self-luminescing feature provided excellent tumour-to-background ratio (>100) for imaging very small tumours (2-3 mm in diameter). Our results demonstrate that these new nanoparticles are well suited to in vivo imaging applications such as lymph-node mapping and cancer imaging.

Use of panitumumab-IRDye800 to image cutaneous head and neck cancer in mice

OBJECTIVE

To assess the feasibility of panitumumab in real-time fluorescent imaging and histologic processing of cutaneous squamous cell carcinoma (cSCC) in mice.

DESIGN

A near-infrared (NIR) fluorescent probe (IRDye800CW) was covalently linked to a monoclonal antibody-targeting epidermal growth factor receptor (panitumumab) or nonspecific IgG and injected into mice bearing flank xenografts from a cSCC cell line (SCC-13 or SRB-12; n = 7), human split-thickness skin grafts (STSGs; n = 3), or a human tumor explant (n = 1). The tumor and lymph nodes were imaged and dissected using fluorescence guidance with the SPY imaging system and verified with a charge-coupled NIR system. An NIR scanning device (Odyssey) was used to measure fluorescence intensity in histological sections.

SUBJECTS

Immunodeficient mice.

SETTING

In vivo and in vitro imaging lab.

RESULTS

Tumor tissue could be delineated from the human STSG with tumor-to-background ratios of 4.5 (Pearl) and 3.4 (SPY). Tumor detection was substantially improved with panitumumab-IRDye800 compared with IgG-IRDye800. Biopsies positive for fluorescence were assessed by histology and immunohistochemistry (n = 18/18) to confirm the presence of tumor, yielding a 100% sensitivity. Biopsies of nonfluorescent tissue negative for malignancy (n = 18/18) yielded a specificity of 100%. Furthermore, the SPY system was able to detect residual disease as small as 200 µm in diameter. In addition, the Odyssey confirmed fluorescence of microscopic disease (in tumor samples of frozen and paraffin-embedded histologic specimens) but not in adjacent noncancerous tissue.

CONCLUSIONS

These data suggest panitumumab-IRDye800 may have clinical utility in detection and removal of subclinical cSCC using Food and Drug Administration-approved imaging hardware.

Intraoperative fluorescent imaging of intracranial tumors: a review

A review of fluorescent imaging for intracranial neoplasms is presented. Complete resection of brain cancer is seldom possible because of the goal to preserve brain tissue and the inability to visualize individual infiltrative tumor cells. Verification of histology and identification of tumor invasion in macroscopically normal-appearing brain tissue determine prognosis after resection of malignant gliomas. Therefore, imaging modalities aim to facilitate intraoperative decision-making. Intraoperative fluorescent imaging techniques have the potential to enable precise histopathologic diagnosis and to detect tumor remnants in the operative field. Macroscopic fluorescence imaging is effective for gross tumor detection. Microscopic imaging techniques enhance the sensitivity of the macroscopic observations and provide real-time histological information. Further development of clinical grade fluorescent agents specifically targeting tumor cells could improve the diagnostic and prognostic yield of intraoperative imaging.

Evaluation of the novel folate receptor ligand [18F]fluoro-PEG-folate for macrophage targeting in a rat model of arthritis

INTRODUCTION

Detection of (subclinical) synovitis is relevant for both early diagnosis and monitoring of therapy of rheumatoid arthritis (RA). Previously, the potential of imaging (sub)clinical arthritis was demonstrated by targeting the translocator protein in activated macrophages using (R)-[11C]PK11195 and positron emission tomography (PET). Images, however, also showed significant peri-articular background activity. The folate receptor (FR)-β is a potential alternative target for imaging activated macrophages. Therefore, the PET tracer [18F]fluoro-PEG-folate was synthesized and evaluated in both in vitro and ex vivo studies using a methylated BSA induced arthritis model.

METHODS

[18F]fluoro-PEG-folate was synthesized in a two-step procedure. Relative binding affinities of non-radioactive fluoro-PEG-folate, folic acid and naturally circulating 5-methyltetrahydrofolate (5-Me-THF) to FR were determined using KB cells with high expression of FR. Both in vivo [18F]fluoro-PEG-folate PET and ex vivo tissue distribution studies were performed in arthritic and normal rats and results were compared with those of the established macrophage tracer (R)-[11C]PK11195.

RESULTS

[18F]fluoro-PEG-folate was synthesized with a purity >97%, a yield of 300 to 1,700 MBq and a specific activity between 40 and 70 GBq/µmol. Relative in vitro binding affinity for FR of F-PEG-folate was 1.8-fold lower than that of folic acid, but 3-fold higher than that of 5-Me-THF. In the rat model, [18F]fluoro-PEG-folate uptake in arthritic knees was increased compared with both contralateral knees and knees of normal rats. Uptake in arthritic knees could be blocked by an excess of glucosamine-folate, consistent with [18F]fluoro-PEG-folate being specifically bound to FR. Arthritic knee-to-bone and arthritic knee-to-blood ratios of [18F]fluoro-PEG-folate were increased compared with those of (R)-[11C]PK11195. Reduction of 5-Me-THF levels in rat plasma to those mimicking human levels increased absolute [18F]fluoro-PEG-folate uptake in arthritic joints, but without improving target-to-background ratios.

CONCLUSIONS

The novel PET tracer [18F]fluoro-PEG-folate, designed to target FR on activated macrophages provided improved contrast in a rat model of arthritis compared with the accepted macrophage tracer (R)-[11C]PK11195. These results warrant further exploration of [18F]fluoro-PEG-folate as a putative PET tracer for imaging (sub)clinical arthritis in RA patients.

Fluorescence-guided surgery and fluorescence laparoscopy for gastrointestinal cancers in clinically-relevant mouse models

There are many challenges that face surgeons when attempting curative resection for gastrointestinal cancers. The ability to properly delineate tumor margins for complete resection is of utmost importance in achieving cure and giving the patient the best chance of prolonged survival. Targeted tumor imaging techniques have gained significant interest in recent years to enable better identification of tumor lesions to improve diagnosis and treatment of cancer from preoperative staging modalities to optimizing the surgeon's ability to visualize tumor margins at the initial operation. Using unique characteristics of the tumor to fluorescently label the tissue can delineate tumor margins from normal surrounding tissue, allowing improved precision of surgical resection. In this paper, different methods of fluorescently labeling native tumor are discussed as well as the development of fluorescence laparoscopy and the potential role for fluorescence-guided surgery in the treatment of gastrointestinal cancers.

Real-time in vivo molecular detection of primary tumors and metastases with ratiometric activatable cell-penetrating peptides

Management of metastatic disease is integral to cancer treatment. Evaluation of metastases often requires surgical removal of all anatomically susceptible lymph nodes for ex vivo pathologic examination. We report a family of novel ratiometric activatable cell-penetrating peptides, which contain Cy5 as far red fluorescent donor and Cy7 as near-infrared fluorescent acceptor. Cy5 is quenched in favor of Cy7 re-emission until the intervening linker is cut by tumor-associated matrix metalloproteinases-2 and 9 (MMP2,9) or elastases. Such cleavage increases the Cy5:Cy7 emission ratio 40-fold and triggers tissue retention of the Cy5-containing fragment. This ratiometric increase provides an accelerated and quantifiable metric to identify primary tumors and metastases to liver and lymph nodes with increased sensitivity and specificity. This technique represents a significant advance over existing nonratiometric protease sensors and sentinel lymph node detection methods, which give no information about cancer invasion.

Fluorescence imaging in surgery

Although the modern surgical era is highlighted by multiple technological advances and innovations, one area that has remained constant is the dependence of the surgeon's vision on white-light reflectance. This renders different body tissues in a limited palette of various shades of pink and red, thereby limiting the visual contrast available to the operating surgeon. Healthy tissue, anatomic variations, and diseased states are seen as slight discolorations relative to each other and differences are inherently limited in dynamic range. In the upcoming years, surgery will undergo a paradigm shift with the use of targeted fluorescence imaging probes aimed at augmenting the surgical armamentarium by expanding the "visible" spectrum available to surgeons. Such fluorescent "smart probes" will provide real-time, intraoperative, pseudo-color, high-contrast delineation of both normal and pathologic tissues. Fluorescent surgical molecular guidance promises another major leap forward to improve patient safety and clinical outcomes, and to reduce overall healthcare costs. This review provides an overview of current and future surgical applications of fluorescence imaging in diseased and nondiseased tissues and focus on the innovative fields of image processing and instrumentation.

Multimodal chelation platform for near-infrared fluorescence/nuclear imaging

Dual-labeled compounds containing nuclear and near-infrared fluorescence contrast have the potential to molecularly guide surgical resection of cancer by extending whole-body diagnostic imaging findings into the surgical suite. To simplify the dual labeling process for antibody-based agents, we designed a multimodality chelation (MMC) scaffold which combined a radiometal chelating agent and fluorescent dye into a single moiety. Three dye-derivatized MMC compounds were synthesized and radiolabeled. The IRDye 800CW conjugate, 4, had favorable optical properties and showed rapid clearance in vivo. Using 4, an epithelial cell adhesion molecule (EpCAM) targeting MMC-immunoconjugate was prepared and dual-labeled with (64)Cu. In vitro binding activity was confirmed after MMC conjugation. Multimodal imaging studies showed higher tumor accumulation of (64)Cu-7 compared to nontargeted (64)Cu-4 in a prostate cancer model. Further evaluation in different EpCAM-expressing cell lines is warranted as well as application of the MMC dual labeling approach with other monoclonal antibodies.

Design considerations for targeted optical contrast agents

Optical fluorescence imaging with the right combination of imaging modality and targeted contrast agents offers tremendous improvement in intraoperative imaging and clinical output (i.e., image-guided cancer surgery). Therefore, it is of paramount importance to gain an in-depth knowledge in the design of targeted contrast agents to meet clinical requirements. Currently, there are several clinically approved contrast agents available; however, none perform optimally in vivo by providing optimum sensitivity, stability, specificity, and safety for target imaging, diagnosis, and therapy. In this review, we discuss basic design considerations for targeted contrast agents in terms of optical and physicochemical properties, biological and physiological interactions, and biodistribution and targeting.

Single snapshot imaging of optical properties

A novel acquisition and processing method that enables single snapshot wide field imaging of optical properties in the Spatial Frequency Domain (SFD) is described. This method makes use of a Fourier transform performed on a single image and processing in the frequency space to extract two spatial frequency images at once. The performance of the method is compared to the standard six image SFD acquisition method, assessed on tissue mimicking phantoms and in vivo. Overall both methods perform similarly in extracting optical properties.

Use of indocyanine green for detecting the sentinel lymph node in breast cancer patients: from preclinical evaluation to clinical validation

Assessment of the sentinel lymph node (SLN) in patients with early stage breast cancer is vital in selecting the appropriate surgical approach. However, the existing methods, including methylene blue and nuclides, possess low efficiency and effectiveness in mapping SLNs, and to a certain extent exert side effects during application. Indocyanine green (ICG), as a fluorescent dye, has been proved reliable usage in SLN detection by several other groups. In this paper, we introduce a novel surgical navigation system to detect SLN with ICG. This system contains two charge-coupled devices (CCD) to simultaneously capture real-time color and fluorescent video images through two different bands. During surgery, surgeons only need to follow the fluorescence display. In addition, the system saves data automatically during surgery enabling surgeons to find the registration point easily according to image recognition algorithms. To test our system, 5 mice and 10 rabbits were used for the preclinical setting and 22 breast cancer patients were utilized for the clinical evaluation in our experiments. The detection rate was 100% and an average of 2.7 SLNs was found in 22 patients. Our results show that the usage of our surgical navigation system with ICG to detect SLNs in breast cancer patients is technically feasible.

Assessing breast cancer margins ex vivo using aqueous quantum-dot-molecular probes

Positive margins have been a critical issue that hinders the success of breast- conserving surgery. The incidence of positive margins is estimated to range from 20% to as high as 60%. Currently, there is no effective intraoperative method for margin assessment. It would be desirable if there is a rapid and reliable breast cancer margin assessment tool in the operating room so that further surgery can be continued if necessary to reduce re-excision rate. In this study, we seek to develop a sensitive and specific molecular probe to help surgeons assess if the surgical margin is clean. The molecular probe consists of the unique aqueous quantum dots developed in our laboratory conjugated with antibodies specific to breast cancer markers such as Tn-antigen. Excised tumors from tumor-bearing nude mice were used to demonstrate the method. AQD-Tn mAb probe proved to be sensitive and specific to identify cancer area quantitatively without being affected by the heterogeneity of the tissue. The integrity of the surgical specimen was not affected by the AQD treatment. Furthermore, AQD-Tn mAb method could determine margin status within 30 minutes of tumor excision, indicating its potential as an accurate intraoperative margin assessment method.

Early detection biomarkers for ovarian cancer

Despite the widespread use of conventional and contemporary methods to detect ovarian cancer development, ovarian cancer remains a common and commonly fatal gynecological malignancy. The identification and validation of early detection biomarkers highly specific to ovarian cancer, which would permit development of minimally invasive screening methods for detecting early onset of the disease, are urgently needed. Current practices for early detection of ovarian cancer include transvaginal ultrasonography, biomarker analysis, or a combination of both. In this paper we review recent research on novel and robust biomarkers for early detection of ovarian cancer and provide specific details on their contributions to tumorigenesis. Promising biomarkers for early detection of ovarian cancer include KLK6/7, GSTT1, PRSS8, FOLR1, ALDH1, and miRNAs.

Near infrared fluorescence for image-guided surgery

Near infrared (NIR) image-guided surgery holds great promise for improved surgical outcomes. A number of NIR image-guided surgical systems are currently in preclinical and clinical development with a few approved for limited clinical use. In order to wield the full power of NIR image-guided surgery, clinically available tissue and disease specific NIR fluorophores with high signal to background ratio are necessary. In the current review, the status of NIR image-guided surgery is discussed along with the desired chemical and biological properties of NIR fluorophores. Lastly, tissue and disease targeting strategies for NIR fluorophores are reviewed.

Operating room of the future

Development of surgical care in the 21st century is increasingly dependent on demonstrating safety, efficacy and cost effectiveness. Over the past 2 decades, the potential role of simulation in surgery has been explored with encouraging results; this can now be linked to direct improvement in the quality of care provision. Computer-assisted surgical platforms, such as robotic surgery, offer us the versatility to embrace a host of technical and technological developments. Rapid development in nanomedicine will expand the limits of operative performance through improved navigation and surgical precision. Integration of the multiple functions of the future operating room will be essential in optimising resource management. The key to bringing about the necessary paradigm shift in the design and delivery of modern surgical care is to appreciate that we now function in an information age, where the integrity of processes is driven by apt data management.

Intraoperative image-guided surgery for ovarian cancer

Approximately two thirds of the ovarian cancer is diagnosed at late stage with peritoneal seeding. The most important prognostic factor is the residual tumor size after surgery. The better survival outcome from minimizing tumor has been established well from several institutional reports, clinical trials for chemotherapy, and meta-analyses. The current standard treatment for such advanced ovarian cancer is to resect all visible and palpable ovarian cancer as much as possible and postoperative chemotherapy. But, even after complete resection of all visible and palpable tumors, a significant percentage of the patients have recurrence usually in the peritoneal cavity in advanced ovarian cancer. Recurrence likely stems from microscopic residual tumor not resected at time of the initial surgery. Currently, advanced technology for intraoperative tumor detection has been reported. Although the current clinical outcome is at an early stage definitively, clinical benefit could be expected from the future in-depth basic research and clinical trials in this area. If all residual microscopic disease, especially chemotherapy-resistant cancer cells, could be removed or treated using new technology, groundbreaking advance for treating ovarian cancer will be realized.

Drug-based optical agents: infiltrating clinics at lower risk

Fluorescent agents with specificity to cellular and subcellular moieties present promise for enhancing diagnostics and theranostics, yet challenges associated with regulatory approvals of experimental agents stifle the clinical translation. As a result, targeted fluorescent agents have remained predominantly as preclinical imaging tools. We discuss the potential of using optically labeled drugs to accelerate the clinical acceptance of optical and optoacoustic agents, in analogy to nuclear medicine approaches. This strategy, corroborated with microdosing studies, outlines a promising approach for overcoming bottlenecks and advancing photonic clinical imaging.

Real-time near infrared fluorescence (NIRF) intra-operative imaging in ovarian cancer using an α(v)β(3-)integrin targeted agent

BACKGROUND

In ovarian cancer, optimal cytoreductive surgery is of the utmost importance for long-term survival. The ability to visualize minuscule tumor deposits is important to ensure complete resection of the tumor. The purpose of our study was to estimate the in vivo sensitivity, specificity and diagnostic accuracy of an intra-operative fluorescence imaging system combined with an α(v)β(3)-integrin targeted near-infrared fluorescent probe.

METHOD

Tumor bearing mice were injected intravenously with a fluorescent probe targeting α(v)β(3) integrins. Fluorescent spots and non-fluorescent tissue were identified and resected. Standard histopathology and fluorescence microscopy were used as gold-standard for tumor detection.

RESULTS

Fifty-eight samples excised with support of intra-operative image-guided surgery were analyzed. The mean target to background ratio was 2.2 (SD 0.5). The calculated sensitivity of the imaging system was 95%, and the specificity was 88% with a diagnostic accuracy of 96.5%.

CONCLUSION

Near-infrared image-guided surgery in this model has a high diagnostic accuracy and a fair target to background ratio that supports the development towards clinical translation of α(v)β(3)-integrin targeted imaging.

Targeting the EphB4 receptor for cancer diagnosis and therapy monitoring

Accumulating evidence suggests that EphB4 plays key roles in cancer progression in numerous cancer types. In fact, therapies focusing on EphB4 have become potentially important components of various cancer treatment strategies. However, tumor sensitivity to EphB4 suppression may not be uniform for different cancers. In this study, we developed near-infrared fluorescence (NIRF) probes for EphB4 targeted imaging, based on EphB4-specific humanized monoclonal antibody hAb47. NIRF dye Cy5.5 was introduced to hAb47 either through the reaction with amino groups (named hAb47-Cy5.5) or sulfhydryl groups (named hAb47-Cy5.5-Mal). The resulting probes were evaluated in both HT-29 xenograft and the mAb131 (anti-EphB4) treated models. Although these methods lead to modifications of both the heavy chain and light chain of the antibody, the majority of the EphB4 binding affinity was maintained (81.62 ± 2.08% for hAb47-Cy5.5 and 77.14 ± 2.46% for hAb47-Cy5.5-Mal, respectively). hAb47-Cy5.5 was then chosen for in vivo NIRF imaging of EphB4 expression. In HT29 colorectal tumor xenografts, hAb47-Cy5.5 demonstrated significantly higher tumor uptake compared with that of the hIgG-Cy5.5 control, which was further confirmed by immunofluorescent staining. Moreover, hAb47-Cy5.5 successfully imaged the decreased EphB4 expression (confirmed by Western blot) in EphB4-targeted immunotherapy using another EphB4-specific antibody, mAb131. Collectively, hAb47-Cy5.5 could be used as a specific NIRF contrast agent for noninvasive imaging of EphB4 expression, which may predict whether an individual tumor would likely respond to EphB4 targeted interventions, as well as monitor the therapeutic response.

Alpha-fetoprotein receptor as an early indicator of HBx-driven hepatocarcinogenesis and its applications in tracing cancer cell metastasis

AFP and its receptor (AFPR) are early indicators of HBx-driven hepatocarcinogenesis. Clinical specimens, normal human liver cells L-02 and HCC cell lines were selected for analyzing the effects of HBx on expression of AFP, AFPR, Src, CXCR4, and Ras. Results showed that AFPR localized in the membranes of HCC samples. HBx upregulated the expression of AFPR and AFP prior to expression of Src, CXCR4, and Ras in L-02 cells and in liver specimens; Target-labeled AFPR was able to reveal the location and metastatic status of HCC in vivo. In this way, actuated expression of AFPR served as an indicator suitable for use in the early diagnosis of HBx-driven malignant transformation of hepatocytes. Labeled AFPR may be applied to trace primary and metastatic HCC.

Microscopic Delineation of Medulloblastoma Margins in a Transgenic Mouse Model Using a Topically Applied VEGFR-1 Probe

The unambiguous demarcation of tumor margins is critical at the final stages in the surgical treatment of brain tumors because patient outcomes have been shown to correlate with the extent of resection. Real-time high-resolution imaging with the aid of a tumor-targeting fluorescent contrast agent has the potential to enable intraoperative differentiation of tumor versus normal tissues with accuracy approaching the current gold standard of histopathology. In this study, a monoclonal antibody targeting the vascular endothelial growth factor receptor 1 (VEGFR-1) was conjugated to fluorophores and evaluated as a tumor contrast agent in a transgenic mouse model of medulloblastoma. The probe was administered topically, and its efficacy as an imaging agent was evaluated in vitro using flow cytometry, as well as ex vivo on fixed and fresh tissues through immunohistochemistry and dual-axis confocal microscopy, respectively. Results show a preferential binding to tumor versus normal tissue, suggesting that a topically applied VEGFR-1 probe can potentially be used with real-time intraoperative optical sectioning microscopy to guide brain tumor resections.

Synthesis and characterization of a melanoma-targeted fluorescence imaging probe by conjugation of a melanocortin 1 receptor (MC1R) specific ligand

The incidence of malignant melanoma is rising more rapidly than that of any other cancer in the United States. The melanocortin 1 receptor (MC1R) is overexpressed in most human melanoma metastases, thus making it a promising target for imaging and therapy of melanomas. We have previously reported the development of a peptidomimetic ligand with high specificity and affinity for MC1R. Here, we have conjugated near-infrared fluorescent dyes to the C-terminus of this ligand via lysine-mercaptopropionic acid linkers to generate MC1R specific optical probes (MC1RL-800, 0.4 nM K(i); and MC1RL-Cy5, 0.3 nM K(i)). Internalization of the imaging probe was studied in vitro by fluorescence microscopy using engineered A375/MC1R cells and B16F10 cells with endogenous MC1R expression. The in vivo tumor targeting of MC1RL-800 was evaluated by intravenous injection of probe into nude mice bearing bilateral subcutaneous A375 xenograft tumors with low MC1R expression and engineered A375/MC1R tumors with high receptor expression. Melanotic B16F10 xenografts were also studied. Fluorescence imaging showed that the agent has higher uptake values in tumors with high expression compared to low (p < 0.05), demonstrating the effect of expression levels on image contrast-to-noise. In addition, tumor uptake was significantly blocked by coinjection of excess NDP-α-MSH peptide (p < 0.05). In conclusion, the MC1R-specific imaging probe developed in this study displays excellent potential for the intraoperative detection of regional node involvement and for margin detection during melanoma metastasis resection.

Near-infrared optical guided surgery of highly infiltrative fibrosarcomas in cats using an anti-αvß3 integrin molecular probe

We investigated how near-infrared imaging could improve highly infiltrative spontaneous fibrosarcoma surgery in 12 cats in a clinical veterinary phase. We used an RGD-based nanoprobe at different doses and times before surgery and a portable clinical grade imaging system. All tumours were labelled by the tracer and had an overall tumour-to-healthy tissue ratio of 14±1 during surgery. No false negatives were found, and the percentage of tumour cells was linearly correlated with the fluorescence intensity. All cats recovered well and were submitted to long-term follow-up that is currently on-going 1year after the beginning of the study.

The PEG-fluorochrome shielding approach for targeted probe design

We provide a new approach for fluorescent probe design termed "PEG-fluorochrome shielding", where PEGylation enhances quantum yields while blocking troublesome interactions between fluorochromes and biomolecules. To demonstrate PEG-fluorochrome shielding, fluorochrome-bearing peptide probes were synthesized, three without PEG and three with a 5 kDa PEG functional group. In vitro, PEG blocked the interactions of fluorochrome-labeled peptide probes with each other (absorption spectra, self-quenching) and reduced nonspecific interactions with cells (by FACS). In vivo, PEG blocked interactions with biomolecules that lead to probe retention (by surface fluorescence). Integrin targeting in vivo was obtained as the differential uptake of an (111)In-labeled, fluorochrome-shielded, integrin-binding RGD probe and a control RAD. Using PEG to block fluorochrome-mediated interactions, rather than synthesizing de novo fluorochromes, can yield new approaches for the design of actively or passively targeted near-infrared fluorescent probes.

Two-step labeling of Staphylococcus aureus with Lysostaphin-Azide and DIBO-Alexa using click chemistry

Specific bacteria imaging is highly desirable in clinical diagnostics. Probes enabling rapid and specific diagnostics of bacteria are limited. Current clinical infection diagnostics is time consuming and invasive, relies on microbiological cultures. We investigated the potential of Lysostaphin as a specific probe to label staphylococci in a new labeling protocol. We used azido (N(3))-modified Lysostaphin-N(3) and DIBO-dye in a two-step bacteria-labeling protocol. N(3) and DIBO (di-benzocyclooctyne) are the counterparts of the "click" chemistry. In the first step, Lysostaphin-N(3) binds specifically to Staphylococcus aureus. In the second step, N(3) clicks to DIBO thus achieving the selective for S. aureus labeling. Such a two-step approach effectively distinguishes S. aureus from Escherichia coli; non-toxic and was proven to work in vivo. The two-step labeling protocol is a promising approach for diagnostic imaging of staphylococcal infections in clinical settings.

Quantitative, spectrally-resolved intraoperative fluorescence imaging

Intraoperative visual fluorescence imaging (vFI) has emerged as a promising aid to surgical guidance, but does not fully exploit the potential of the fluorescent agents that are currently available. Here, we introduce a quantitative fluorescence imaging (qFI) approach that converts spectrally-resolved data into images of absolute fluorophore concentration pixel-by-pixel across the surgical field of view (FOV). The resulting estimates are linear, accurate, and precise relative to true values, and spectral decomposition of multiple fluorophores is also achieved. Experiments with protoporphyrin IX in a glioma rodent model demonstrate in vivo quantitative and spectrally-resolved fluorescence imaging of infiltrating tumor margins for the first time. Moreover, we present images from human surgery which detect residual tumor not evident with state-of-the-art vFI. The wide-field qFI technique has broad implications for intraoperative surgical guidance because it provides near real-time quantitative assessment of multiple fluorescent biomarkers across the operative field.

Novel toll-like receptor 2 ligands for targeted pancreatic cancer imaging and immunotherapy

Toll-like receptor 2 (TLR2) is a target for immune system stimulation during cancer immunotherapy and a cell-surface marker for pancreatic cancer. To develop targeted agents for cancer imaging and therapy, we designed, synthesized, and characterized 13 novel, fully synthetic high affinity TLR2 agonists. Analogue 10 had the highest agonist activity (NF-κB functional assay, EC(50) = 20 nM) and binding affinity (competitive binding assay, K(i) = 25 nM). As an immune adjuvant, compound 10 stimulated the immune system in vivo by generation and persistence of antigen-specific CD8+ T cells indicating its potential use in cancer immunotherapy. After conjugation of near-infrared dye to 10, agonist activity (EC(50) = 34 nM) and binding affinity (K(i) = 11 nM) were retained in 13. Fluorescence signal was present in TLR2 expressing pancreatic tumor xenografts 24 h after injection of 13, while an excess of unlabeled ligand blocked 13 from binding to the tumor, resulting in significantly decreased signal (p < 0.001) demonstrating in vivo selectivity.

Use of panitumumab-IRDye800 to image microscopic head and neck cancer in an orthotopic surgical model

BACKGROUND

Fluorescence imaging hardware (SPY) has recently been developed for intraoperative assessment of blood flow via detection of probes emitting in the near-infrared (NIR) spectrum. This study sought to determine if this imaging system was capable of detecting micrometastatic head and neck squamous cell carcinoma (HNSCC) in preclinical models.

METHODS

A NIR fluorescent probe (IRDye800CW) was covalently linked to a monoclonal antibody targeting epidermal growth factor receptor (EGFR; panitumumab) or nonspecific IgG. HNSCC flank (SCC-1) and orthotopic (FADU and OSC19) xenografts were imaged 48-96 h after systemic injection of labeled panitumumab or IgG. The primary tumor and regional lymph nodes were dissected using fluorescence guidance with the SPY system and grossly assessed with a charge-coupled NIR system (Pearl). Histologic slides were also imaged with a NIR charged-coupled device (Odyssey) and fluorescence intensity was correlated with pathologic confirmation of disease.

RESULTS

Orthotopic tongue tumors were clearly delineated from normal tissue with tumor-to-background ratios of 2.9 (Pearl) and 2.3 (SPY). Disease detection was significantly improved with panitumumab-IRDye compared to IgG-IRDye800 (P < 0.05). Tissue biopsy samples (average size 3.7 mm) positive for fluorescence were confirmed for pathologic disease by histology and immunohistochemistry (n = 25 of 25). Biopsy samples of nonfluorescent tissue were proven to be negative for malignancy (n = 28 of 28). The SPY was able to detect regional lymph node metastasis (<1.0 mm) and microscopic areas of disease. Standard histological assessment in both frozen and paraffin-embedded histologic specimens was augmented using the Odyssey.

CONCLUSIONS

Panitumumab-IRDye800 may have clinical utility in detection and removal of microscopic HNSCC using existing intraoperative optical imaging hardware and may augment analysis of frozen and permanent pathology.

Translational optical imaging

OBJECTIVE

Optical imaging is experiencing significant technologic advances. Simultaneously, an array of specific optical imaging agents has brought new capabilities to biomedical research and is edging toward clinical use. We review progress in the translation of macroscopic optical imaging-including fluorescence-guided surgery and endoscopy, intravascular fluorescence imaging, diffuse fluorescence and optical tomography, and multispectral optoacoustics (photoacoustics)-for applications ranging from tumor resection and assessment of atherosclerotic plaques to dermatologic and breast examinations.

CONCLUSION

Optical imaging could play a major role in the move from imaging of structure and morphology to the visualization of the individual biologic processes underlying disease and could, therefore, contribute to more accurate diagnostics and improved treatment efficacy.

The antifolates

This article focuses on the cellular, biochemical, and molecular pharmacology of antifolates and how a basic understanding of the mechanism of action of methotrexate, its cytotoxic determinants, mechanisms of resistance, and transport into and out of cells has led to the development of a new generation of antifolates, a process that continues in the laboratory and in the clinics. New approaches to folate-based cancer chemotherapy are described based on the targeted delivery of drugs to malignant cells.

Near-infrared fluorescent imaging of metastatic ovarian cancer using folate receptor-targeted high-density lipoprotein nanocarriers

AIM

The targeting efficiency of folate receptor-α (FR-α)-targeted high-density lipoprotein nanoparticles (HDL NPs) was evaluated in a syngeneic mouse model of ovarian cancer.

MATERIALS & METHODS

Folic acid was conjugated to the surface of fluorescent-labeled HDL NPs. In vivo tumor targeting of folic acid-HDL NPs and HDL NPs were evaluated in mice with metastatic ovarian cancer following intravenous or intraperitoneal (ip.) administration.

RESULTS & DISCUSSION

Intravenous FR-α-targeted HDL resulted in high uptake of the fluorescent nanoparticle in host liver and spleen. The ip. injection of fluorescent HDL produced moderate fluorescence throughout the abdomen. Conversely, animals receiving the ip. FR-α-targeted HDL showed a high fluorescence signal in ovarian tumors, surpassing that seen in all of the host tissues.

CONCLUSION

The authors' findings demonstrate that the combination of local-regional ip. administration and FR-α-directed nanoparticles provides an enhanced approach to selectively targeting ovarian cancer cells for drug treatment.

Single cell molecular recognition of migrating and invading tumor cells using a targeted fluorescent probe to receptor PTPmu

Detection of an extracellular cleaved fragment of a cell-cell adhesion molecule represents a new paradigm in molecular recognition and imaging of tumors. We previously demonstrated that probes that recognize the cleaved extracellular domain of receptor protein tyrosine phosphatase mu (PTPmu) label human glioblastoma brain tumor sections and the main tumor mass of intracranial xenograft gliomas. In this article, we examine whether one of these probes, SBK2, can label dispersed glioma cells that are no longer connected to the main tumor mass. Live mice with highly dispersive glioma tumors were injected intravenously with the fluorescent PTPmu probe to test the ability of the probe to label the dispersive glioma cells in vivo. Analysis was performed using a unique three-dimensional (3D) cryo-imaging technique to reveal highly migratory and invasive glioma cell dispersal within the brain and the extent of colabeling by the PTPmu probe. The PTPmu probe labeled the main tumor site and dispersed cells up to 3.5 mm away. The cryo-images of tumors labeled with the PTPmu probe provide a novel, high-resolution view of molecular tumor recognition, with excellent 3D detail regarding the pathways of tumor cell migration. Our data demonstrate that the PTPmu probe recognizes distant tumor cells even in parts of the brain where the blood-brain barrier is likely intact. The PTPmu probe has potential translational significance for recognizing tumor cells to facilitate molecular imaging, a more complete tumor resection and to serve as a molecular targeting agent to deliver chemotherapeutics to the main tumor mass and distant dispersive tumor cells.

Redirecting gene-modified T cells toward various cancer types using tagged antibodies

PURPOSE

To develop an adaptable gene-based vector that will confer immune cell specificity to various cancer types.

EXPERIMENTAL DESIGN

Human and mouse T cells were genetically engineered to express a chimeric antigen receptor (CAR) that binds a fluorescein isothiocyanate (FITC) molecule, termed anti-FITC CAR T cells. Various antibodies (Ab) currently in clinical use including cetuximab (Ctx), trastuzumab (Her2), and rituximab (Rtx) were conjugated with FITC and tested for their ability to bind tumor cells, activate T cells, and induce antitumor effects in vitro and in vivo.

RESULTS

Anti-FITC CAR T cells recognize various cancer types when bound with FITC-labeled Abs resulting in efficient target lysis, T-cell proliferation, and cytokine/chemokine production. The treatment of immunocompromised mice with human anti-FITC CAR T cells plus FITC-labeled cetuximab (FITC-Ctx) delayed the growth of colon cancer but unexpectedly led to the outgrowth of EGF receptor (EGFR)-negative tumor cells. On the other hand, in a human pancreatic cancer cell line with uniform EGFR expression, anti-FITC CAR T cells plus FITC-Ctx eradicated preestablished late-stage tumors. In immunocompetent mice, anti-FITC CAR T cells exhibited potent antitumor activity against syngeneic mouse breast cancer expressing Her2 and B-cell lymphoma expressing CD20 by combining with FITC-Her2 and FITC-Rtx, respectively. In addition, the activity of anti-FITC CAR T cells could be attenuated by subsequent injections of nonspecific FITC-IgG.

CONCLUSION

These studies highlight an applicability of anti-tag CAR technology to treat patients with different types of cancers and a possibility to regulate CAR T-cell functions with competing FITC molecules.

Impairment of retrograde neuronal transport in oxaliplatin-induced neuropathy demonstrated by molecular imaging

BACKGROUND AND PURPOSE

The purpose of our study was to utilize a molecular imaging technology based on the retrograde axonal transport mechanism (neurography), to determine if oxaliplatin-induced neurotoxicity affects retrograde axonal transport in an animal model.

MATERIALS AND METHODS

Mice (n = 8/group) were injected with a cumulative dose of 30 mg/kg oxaliplatin (sufficient to induce neurotoxicity) or dextrose control injections. Intramuscular injections of Tetanus Toxin C-fragment (TTc) labeled with Alexa 790 fluorescent dye were done (15 ug/20 uL) in the left calf muscles, and in vivo fluorescent imaging performed (0-60 min) at baseline, and then weekly for 5 weeks, followed by 2-weekly imaging out to 9 weeks. Tissues were harvested for immunohistochemical analysis.

RESULTS

With sham treatment, TTc transport causes fluorescent signal intensity over the thoracic spine to increase from 0 to 60 minutes after injection. On average, fluorescence signal increased 722%+/-117% (Mean+/-SD) from 0 to 60 minutes. Oxaliplatin treated animals had comparable transport at baseline (787%+/-140%), but transport rapidly decreased through the course of the study, falling to 363%+/-88%, 269%+/-96%, 191%+/-58%, 121%+/-39%, 75%+/-21% with each successive week and stabilizing around 57% (+/-15%) at 7 weeks. Statistically significant divergence occurred at approximately 3 weeks (p≤0.05, linear mixed-effects regression model). Quantitative immuno-fluorescence histology with a constant cutoff threshold showed reduced TTc in the spinal cord at 7 weeks for treated animals versus controls (5.2 Arbitrary Units +/-0.52 vs 7.1 AU +/-1.38, p<0.0004, T-test). There was no significant difference in neural cell mass between the two groups as shown with NeuN staining (10.2+/-1.21 vs 10.5 AU +/-1.53, p>0.56, T-test).

CONCLUSION

We show-for the first time to our knowledge-that neurographic in vivo molecular imaging can demonstrate imaging changes in a model of oxaliplatin-induced neuropathy. Impaired retrograde neural transport is suggested to be an important part of the pathophysiology of oxaliplatin-induced neuropathy.

Immuno-PET of tissue factor in pancreatic cancer

Upregulation of tissue factor (TF) expression leads to increased patient morbidity and mortality in many solid tumor types. The goal of this study was to develop a PET tracer for imaging of TF expression in pancreatic cancer.

METHODS

ALT-836, a chimeric antihuman TF monoclonal antibody, was conjugated to 2-S-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA) and labeled with (64)Cu. To compare the TF binding affinity of ALT-836 and NOTA-ALT-836, flow cytometry analysis was performed in 3 pancreatic cancer cell lines with different expression levels of TF (from low to high: PANC-1, ASPC-1, and BXPC-3). PET, biodistribution, blocking, and histology studies were performed on pancreatic tumor-bearing mice to evaluate the ability and specificity of (64)Cu-NOTA-ALT-836 to target TF in vivo.

RESULTS

There was no difference in TF binding affinity between ALT-836 and NOTA-ALT-836. (64)Cu-labeling was achieved with high yield and specific activity. Serial PET revealed that the uptake of (64)Cu-NOTA-ALT-836 in BXPC-3 tumors (high TF expression) was 5.7 ± 1.8, 10.4 ± 0.8, and 16.5 ± 2.6 percentage injected dose per gram at 4, 24, and 48 h after injection, respectively (n = 4), significantly higher than that in the PANC-1 and ASPC-1 tumors. Biodistribution data as measured by γ-counting were consistent with the PET findings. Blocking experiments and histology further confirmed the TF specificity of (64)Cu-NOTA-ALT-836.

CONCLUSION

Herein we report the first successful PET imaging of TF expression. Persistent and TF-specific uptake of (64)Cu-NOTA-ALT-836 was observed in pancreatic cancer models.

Targeted dual-color silica nanoparticles provide univocal identification of micrometastases in preclinical models of colorectal cancer

Background and methods

Despite the recent introduction of targeted bio-drugs, the scarcity of successful therapeutic options for advanced colorectal cancer remains a limiting factor in patient management. The efficacy of curative surgical interventions can only be extended through earlier detection of metastatic foci, which is dependent on both the sensitivity and specificity of the diagnostic tools.

Results

We propose a high-performance imaging platform based on silica-poly(ethylene glycol) nanoparticles doped with rhodamine B and cyanine 5. Simultaneous detection of these dyes is the basis for background subtraction and signal amplification, thus providing high-sensitivity imaging. The functionalization of poly(ethylene glycol) tails on the external face of the nanoparticles with metastasis-specific peptides guarantees their homing to and accumulation at target tissues, resulting in specific visualization, even of submillimetric metastases.

Conclusions

The results reported here demonstrate that our rationally designed modular nanosystems have the ability to produce a breakthrough in the detection of micrometastases for subsequent translation to clinics in the immediate future.

In vivo fluorescence imaging with Ag2S quantum dots in the second near-infrared region

Hits the dot: Ag(2)S quantum dots (QDs) with bright near-infrared-II fluorescence emission (around 1200 nm) and six-arm branched PEG surface coating were synthesized for in vivo small-animal imaging. The 6PEG-Ag(2)S QDs afforded a tumor uptake of approximately 10 % injected dose/gram, owing to a long circulation half-life of approximately 4 h. Clearance of the injected 6PEG-Ag(2)S QDs occurs mainly through the biliary pathway in mice.