Fluorescence and tracers in surgery: the coming future

The revolution that we are seeing in the world of surgery will determine the way we understand surgical approaches in coming years. Since the implementation of minimally invasive surgery, innovations have constantly been developed to allow the laparoscopic approach to go further and be applied to more and more procedures. In recent years, we have been in the middle of another revolutionary era, with robotic surgery, the application of artificial intelligence and image-guided surgery. The latter includes 3D reconstructions for surgical planning, virtual reality, holograms or tracer-guided surgery, where ICG-guided fluorescence has provided a different perspective on surgery. ICG has been used to identify anatomical structures, assess tissue perfusion, and identify tumors or tumor lymphatic drainage. But the most important thing is that this technology has come hand in hand with the potential to develop other types of tracers that will facilitate the identification of tumor cells and ureters, as well as different light beams to identify anatomical structures. These will lead to other types of systems to assess tissue perfusion without the use of tracers, such as hyperspectral imaging. Combined with the upcoming introduction of ICG quantification, these developments represent a real revolution in the surgical world. With the imminent implementation of these technological advances, a review of their clinical application in general surgery is timely, and this review serves that aim.

Spatial and temporal patterns in dynamic-contrast enhanced intraoperative fluorescence imaging enable classification of bone perfusion in patients undergoing leg amputation

Dynamic contrast-enhanced fluorescence imaging (DCE-FI) classification of tissue viability in twelve adult patients undergoing below knee leg amputation is presented. During amputation and with the distal bone exposed, indocyanine green contrast-enhanced images were acquired sequentially during baseline, following transverse osteotomy and following periosteal stripping, offering a uniquely well-controlled fluorescence dataset. An unsupervised classification machine leveraging 21 different spatiotemporal features was trained and evaluated by cross-validation in 3.5 million regions-of-interest obtained from 9 patients, demonstrating accurate stratification into normal, suspicious, and compromised regions. The machine learning (ML) approach also outperformed the standard method of using fluorescence intensity only to evaluate tissue perfusion by a two-fold increase in accuracy. The generalizability of the machine was evaluated in image series acquired in an additional three patients, confirming the stability of the model and ability to sort future patient image-sets into viability categories.

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

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

The Use of Fluorescent Anti-CEA Antibodies to Label, Resect and Treat Cancers: A Review

A major barrier to the diagnosis and effective treatment of solid-tumor cancers is the difficulty in detection and visualization of tumor margins in primary and metastatic disease. The use of fluorescence can augment the surgeon's ability to detect cancer and aid in its resection. Several cancer types express carcinoembryonic antigen (CEA) including colorectal, pancreatic and gastric cancer. Antibodies to CEA have been developed and tagged with near-infrared fluorescent dyes. This review article surveyed the use of CEA antibodies conjugated to fluorescent probes for in vivo studies since 1990. PubMed and Google Scholar databases were queried, and 900 titles and abstracts were screened. Fifty-nine entries were identified as possibly meeting inclusion/exclusion criteria and were reviewed in full. Forty articles were included in the review and their citations were screened for additional entries. A total of 44 articles were included in the final review. The use of fluorescent anti-CEA antibodies has been shown to improve detection and resection of tumors in both murine models and clinically. The cumulative results indicate that fluorescent-conjugated anti-CEA antibodies have important potential to improve cancer diagnosis and surgery. In an emerging technology, anti-CEA fluorescent antibodies have also been successfully used for photoimmunotherapy treatment for cancer.

Color-Coded Imaging of the Tumor Microenvironment (TME) in Human Patient-Derived Orthotopic Xenograft (PDOX) Mouse Models

The tumor microenvironment (TME) contains stromal cells in a complex interaction with cancer cells. This relationship has become better understood with the use of fluorescent proteins for in vivo imaging, originally developed by our laboratories. Spectrally distinct fluorescent proteins can be used for color-coded imaging of the complex interaction of the tumor microenvironment in the living state using cancer cells expressing a fluorescent protein of one color and host mice expressing another color fluorescent protein. Cancer cells engineered in vitro to express a fluorescent protein were orthotopically implanted into transgenic mice expressing a fluorescent protein of a different color. Confocal microscopy was then used for color-coded imaging of the TME. Color-coded imaging of the TME has enabled us to discover that stromal cells are necessary for metastasis. Patient-derived orthotopic xenograft (PDOX) tumors were labeled by first passaging them orthotopically through transgenic nude mice expressing either green, red, or cyan fluorescent protein in order to label the stromal cells of the tumor. The colored stromal cells become stably associated with the PDOX tumors through multiple passages in transgenic colored nude mice or noncolored nude mice. The fluorescent protein-expressing stromal cells included cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs). Using this model, specific cancer cell or stromal cell targeting by potential therapeutics can be visualized. Color-coded imaging enabled the visualization of apparent fusion of cancer and stromal cells. Color-coded imaging is a powerful tool visualizing the interaction of cancer and stromal cells during cancer progression and treatment.

A review of tumor-specific fluorescence-guided surgery for colorectal cancer

The present study reviews the use of tumor-specific antibodies conjugated to fluorescent dyes in preclinical and clinical studies to enhance visualization of primary tumors and metastases for fluorescence-guided surgery (FGS) in colorectal cancer (CRC). A search strategy was developed using the peer-reviewed National Center for Biotechnology Information (NCBI) database on PubMed. Studies using tumor-specific fluorescence imaging and FGS techniques on murine models of colorectal cell lines or patient-derived orthotopic xenograft (PDOX) colorectal cancer are reviewed. A total of 24 articles were identified that met the inclusion criteria, 21 preclinical and 3 clinical trials. The most widely used target antigen in preclinical and clinical trials was carcinoembryonic antigen (CEA). Mouse studies and clinical studies have demonstrated that the use of FGS in CRC can aid in decreased residual tumor and decreased rates of recurrence. As the mainstay of colorectal cancer treatment is surgery, the addition of intraoperative fluorescence imaging can help locate tumor margins, visualize occult micro-metastases, drive surgical decision making and improve patient outcomes.

Application of fluorescein sodium in breast cancer brain-metastasis surgery

OBJECTIVE

Surgical resection serves an important role in the multidisciplinary treatment of cerebral metastases (CMs). Conventional white-light, microsurgical, and circumferential stripping of CMs is standard neurosurgical procedure, but is associated with a high recurrence rate. Based on this outcome, there is an urgent need for a new surgical strategy, such as fluorescence-guided resection, for CMs, in order to achieve total removal.

METHODS

A retrospective study was carried out in 38 patients clinically and pathologically diagnosed with breast cancer brain metastasis at three medical centers from May 2012 to June 2016. The study comprised group 1 (fluorescein-guided surgery) and group 2 (standard microsurgery). In group 1, 5 mg/kg of fluorescein sodium was injected intravenously after an allergy test and before general anesthesia for 17 patients. A yellow 560 filter was employed for microsurgical tumor resection. Group 2 consisted of 21 patients for whom fluorescein was not administered.

RESULTS

Surgical outcomes were assessed concerning the extent of resection and Karnofsky performance status. Gross total resection was achieved in these patients, with high fluorescence markedly enhancing tumor visibility. The extent of resection had a powerful influence on performance status. Overall survival after CM was 24.1 months in patients given fluorescein and was 22.8 months in the nonfluorescein group.

CONCLUSION

Fluorescein-guided surgery is a simple, safe, and practical method to resect breast cancer brain metastasis, and leads to a higher proportion of resection compared to common microsurgery. This offers a tremendous advantage when navigating a tiny tumor, and improves the quality of life of patients with CM.

Precision Medicine for CRC Patients in the Veteran Population: State-of-the-Art, Challenges and Research Directions

Colorectal cancer (CRC) accounts for ~9% of all cancers in the Veteran population, a fact which has focused a great deal of the attention of the VA's research and development efforts. A field-based meeting of CRC experts was convened to discuss both challenges and opportunities in precision medicine for CRC. This group, designated as the VA Colorectal Cancer Cell-genomics Consortium (VA4C), discussed advances in CRC biology, biomarkers, and imaging for early detection and prevention. There was also a discussion of precision treatment involving fluorescence-guided surgery, targeted chemotherapies and immunotherapies, and personalized cancer treatment approaches. The overarching goal was to identify modalities that might ultimately lead to personalized cancer diagnosis and treatment. This review summarizes the findings of this VA field-based meeting, in which much of the current knowledge on CRC prescreening and treatment was discussed. It was concluded that there is a need and an opportunity to identify new targets for both the prevention of CRC and the development of effective therapies for advanced disease. Also, developing methods integrating genomic testing with tumoroid-based clinical drug response might lead to more accurate diagnosis and prognostication and more effective personalized treatment of CRC.

Fluorescence-guided surgery of a highly-metastatic variant of human triple-negative breast cancer targeted with a cancer-specific GFP adenovirus prevents recurrence

We have previously developed a genetically-engineered GFP-expressing telomerase-dependent adenovirus, OBP-401, which can selectively illuminate cancer cells. In the present report, we demonstrate that targeting a triple-negative high-invasive human breast cancer, orthotopically-growing in nude mice, with OBP-401 enables curative fluorescence-guided surgery (FGS). OBP-401 enabled complete resection and prevented local recurrence and greatly inhibited lymph-node metastasis due to the ability of the virus to selectively label and subsequently kill cancer cells. In contrast, residual breast cancer cells become more aggressive after bright (white)-light surgery (BLS). OBP-401-based FGS also improved the overall survival compared with conventional BLS. Thus, metastasis from a highly-aggressive triple-negative breast cancer can be prevented by FGS in a clinically-relevant mouse model.

Fluorescence-Guided Surgery

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

Near-infrared-conjugated humanized anti-carcinoembryonic antigen antibody targets colon cancer in an orthotopic nude-mouse model

BACKGROUND

The success of a curative surgery for cancer is dependent on the complete removal of all cancer cells. Tumor visualization by the surgeon can be enhanced through fluorescent-antibody targeting. To further develop such technology, we selected humanized anti-carcinoembryonic antigen (CEA) conjugated to a near-infrared dye to target orthotopically-implanted human colon cancer in nude mice.

MATERIALS AND METHODS

The HT-29 human colon cancer cell line was grown in culture and subcutaneously injected in mice. After 3 wk of growth, tumors were resected and cut into 2 mm³ fragments that were sutured to the cecum of five additional nude mice for orthotopic implantation. The tumors were allowed to grow for 4 wk at which point 3 had successful orthotopic tumor growth and were selected for injection of the humanized anti-CEA antibody conjugated to the near-infrared dye IRDye800CW (anti-CEA-IRDye800CW). The antibody-dye conjugate (75 μg) was administered via tail vein injection. Images were obtained with the Pearl Trilogy Small Animal Imaging System with both 700 and 800 nm channels and evaluated using Image Studio.

RESULTS

Laparotomy was performed 24 h after labeling the tumors. When imaged through the 800 nm channel, the tumors were observed to be strongly labeled with anti-CEA-IRDye800. At 48 h, laparotomy was repeated which again demonstrated strong labeling of the tumors through the 800 nm channel, but with a lower absolute intensity (in relative units), than at 24 h.

CONCLUSIONS

Humanized anti-CEA-IRDye800CW can rapidly and effectively label CEA-expressing human colon cancer in an orthotopic nude mouse model. Given the ability of this technology to target and label tumors with great specificity, the anti-CEA-IRDye800CW is currently being developed for clinical use in fluorescence-guided surgery.

Near-Infrared Photochemoimmunotherapy by Photoactivatable Bifunctional Antibody-Drug Conjugates Targeting Human Epidermal Growth Factor Receptor 2 Positive Cancer

Near-infrared photoimmunotherapy (NIR-PIT) is a new class of molecular targeted cancer therapy based on antibody-photoabsorber conjugates and NIR light irradiation. Recent studies have shown effective tumor control, including that of human epidermal growth factor receptor 2 (HER2)-positive cancer, by selective molecular targeting with NIR-PIT. However, the depth of NIR light penetration limits its use. Trastuzumab emtansine (T-DM1) is an antibody-drug conjugate consisting of the monoclonal antibody trastuzumab linked to the cytotoxic agent maytansinoid DM1. Here, we developed bifunctional antibody-drug-photoabsorber conjugates, T-DM1-IR700, that can work as both NIR-PIT and chemoimmunotherapy agents. We evaluated the feasibility of T-DM1-IR700-mediated NIR light irradiation by comparing the in vitro and in vivo cytotoxic efficacy of trastuzumab-IR700 (T-IR700)-mediated NIR light irradiation in HER2-expressing cells. T-IR700 and T-DM1-IR700 showed almost identical binding to HER2 in vitro and in vivo. Owing to the presence of internalized DM1 in the target cells, NIR-PIT using T-DM1-IR700 tended to induce greater cytotoxicity than that of NIR-PIT using T-IR700 in vitro. In vivo NIR-PIT using T-DM1-IR700 did not show a superior antitumor effect to NIR-PIT using T-IR700 in subcutaneous small-tumor models, which could receive sufficient NIR light. In contrast, NIR-PIT using T-DM1-IR700 tended to reduce the tumor volume and showed significant prolonged survival compared to NIR-PIT using T-IR700 in large-tumor models that could not receive sufficient NIR light. We successfully developed a T-DM1-IR700 conjugate that has a similar immunoreactivity to the parental antibody with increased cytotoxicity due to DM1 and potential as a new NIR-PIT agent for targeting tumors that are large and inaccessible to sufficient NIR light irradiation to activate the photoabsorber IR700.

Targeted multimodal nano-reporters for pre-procedural MRI and intra-operative image-guidance

Multimodal-imaging probes offer a novel approach, which can provide detail diagnostic information for the planning of image-guided therapies in clinical practice. Here we report targeted multimodal Nd3+-doped upconversion nanoparticle (UCNP) imaging reporters, integrating both magnetic resonance imaging (MRI) and real-time upconversion luminescence imaging (UCL) capabilities within a single platform. Nd3+-doped UCNPs were synthesized as a core-shell structure showing a bright visible emission upon excitation at the near infrared (minimizing biological overheating and increasing tissue penetration depth) as well as providing strong MRI T2 contrast (high r2/r1 ratio). Transcatheter intra-arterial infusion of Nd3+-doped UCNPs conjugated with anti-CD44-monoclonal antibody allowed for high performance in vivo multimodal UCL and MR imaging of hepatocellular carcinoma (HCC) in an orthotopic rat model. The resulted in vivo multimodal imaging of Nd3+ doped core-shell UCNPs combined with transcatheter intra-arterial targeting approaches successfully discriminated liver tumors from normal hepatic tissues in rats for surgical resection applications. The demonstrated multimodal UCL and MRI imaging capabilities of our multimodal UCNPs reporters suggest strong potential for in vivo visualization of tumors and precise surgical guidance to fill the gap between pre-procedural imaging and intraoperative reality.

Review of fluorescence guided surgery systems: identification of key performance capabilities beyond indocyanine green imaging

There is growing interest in using fluorescence imaging instruments to guide surgery, and the leading options for open-field imaging are reviewed here. While the clinical fluorescence-guided surgery (FGS) field has been focused predominantly on indocyanine green (ICG) imaging, there is accelerated development of more specific molecular tracers. These agents should help advance new indications for which FGS presents a paradigm shift in how molecular information is provided for resection decisions. There has been a steady growth in commercially marketed FGS systems, each with their own differentiated performance characteristics and specifications. A set of desirable criteria is presented to guide the evaluation of instruments, including: (i) real-time overlay of white-light and fluorescence images, (ii) operation within ambient room lighting, (iii) nanomolar-level sensitivity, (iv) quantitative capabilities, (v) simultaneous multiple fluorophore imaging, and (vi) ergonomic utility for open surgery. In this review, United States Food and Drug Administration 510(k) cleared commercial systems and some leading premarket FGS research systems were evaluated to illustrate the continual increase in this performance feature base. Generally, the systems designed for ICG-only imaging have sufficient sensitivity to ICG, but a fraction of the other desired features listed above, with both lower sensitivity and dynamic range. In comparison, the emerging research systems targeted for use with molecular agents have unique capabilities that will be essential for successful clinical imaging studies with low-concentration agents or where superior rejection of ambient light is needed. There is no perfect imaging system, but the feature differences among them are important differentiators in their utility, as outlined in the data and tables here.

Diagnostic Performance of Indocyanine Green-Guided Sentinel Lymph Node Biopsy in Breast Cancer: A Meta-Analysis

Background

The diagnostic performance of indocyanine green (ICG) fluorescence-guided sentinel lymph node biopsy (SLNB) for the presence of metastases in breast cancer remains unclear.

Objective

We performed a meta-analysis to investigate the diagnostic performance of ICG-guided SLNB.

Methods

Eligible studies were identified from searches of the databases PubMed and EMBASE up to September 2015. Studies that reported the detection rate of ICG fluorescence-guided SLNB with full axillary lymph node dissection and histological or immunohistochemical examinations were included. A meta-analysis was performed to generate pooled detection rate, sensitivity, specificity, false negative rate, diagnostic odds ratio (DOR) and a summary receiver operator characteristic curve (SROC).

Results

Nineteen published studies were included to generate a pooled detection rate, comprising 2594 patients. The pooled detection rate was 0.98 (95% confidence interval [CI], 0.96–0.99). Six studies finally met the criteria for meta-analysis, which yielded a pooled sensitivity of 0.92 (95% CI, 0.85–0.96), specificity 1 (95% CI, 0.97–1), and DOR 311.47 (95% CI, 84.11–1153.39). The area under the SROC was 0.9758. No publication bias was found.

Conclusion

ICG fluorescence-guided SLNB is viable for detection of lymph node metastases in breast cancer. Large-scale randomized multi-center trials are necessary to confirm our results.

Feasibility of Using an Enzymatically Activatable Fluorescence Probe for the Rapid Evaluation of Pancreatic Tissue Obtained Using Endoscopic Ultrasound-Guided Fine Needle Aspiration: a Pilot Study

PURPOSE

Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) is the most reliable method for the histological diagnosis of pancreatic tumors. Rapid on-site fluorescence-guided histological diagnosis was evaluated by topically applying an enzymatically activatable probe onto the EUS-FNA samples; the probe fluoresces in the presence of γ-glutamyltranspeptidase (GGT).

PROCEDURES

We evaluated GGT expression in pancreatic cancer cell lines in vitro. EUS-FNA was performed in 10 pancreatic tumors. After topical application of the probe, signal intensity was measured using a fluorescence imaging system for 13 min.

RESULTS

GGT was expressed in Panc-1, AsPC-1, and AR42J, but not in KP4 cells. In samples from six cases, several regions of the specimens fluoresced and contained adequate tissue for pathological diagnosis. The remaining four non-fluorescent samples contained very small amounts of carcinoma, normal epithelial cells, or no epithelial cells. The signal intensity at 5 min was 25.5 ± 7.7 and 7.7 ± 0.5 in fluorescent and non-fluorescent regions, respectively (p < 0.05).

CONCLUSIONS

Application of enzymatically activatable probe onto EUS-FNA samples would be feasible for the rapid evaluation of tissues suitable for histological diagnosis.

Imaging and Selective Elimination of Glioblastoma Stem Cells with Theranostic Near-Infrared-Labeled CD133-Specific Antibodies

Near-infrared photoimmunotherapy (NIR-PIT), which employs monoclonal antibody (mAb)-phototoxic phthalocyanine dye IR700 conjugates, permits the specific, image-guided and spatiotemporally controlled elimination of tumor cells. Here, we report the highly efficient NIR-PIT of human tumor xenografts initiated from patient-derived cancer stem cells (CSCs). Using glioblastoma stem cells (GBM-SCs) expressing the prototypic CSC marker AC133/CD133, we also demonstrate here for the first time that NIR-PIT is highly effective against brain tumors. The intravenously injected theranostic AC133 mAb conjugate enabled the non-invasive detection of orthotopic gliomas by NIR fluorescence imaging, and reached AC133+ GBM-SCs at the invasive tumor front. AC133-targeted NIR-PIT induced the rapid cell death of AC133+ GBM-SCs and thereby strong shrinkage of both subcutaneous and invasively growing brain tumors. A single round of NIR-PIT extended the overall survival of mice with established orthotopic gliomas by more than a factor of two, even though the harmless NIR light was applied through the intact skull. Humanised versions of this theranostic agent may facilitate intraoperative imaging and histopathological evaluation of tumor borders and enable the highly specific and efficient eradication of CSCs.

Fluorescence-guided surgery of human prostate cancer experimental bone metastasis in nude mice using anti-CEA DyLight 650 for tumor illumination

The present report demonstrates efficacy of fluorescence-guided surgery (FGS) to resect and prevent recurrence of experimental skeletal metastasis in a nude-mouse model of human prostate cancer. Green fluorescent protein (GFP)-expressing PC-3 human prostate cancer cells were injected into the intramedullary cavity of the tibia in 25 nude mice. One week after implantation, monoclonal antibodies, specific for carcinoembryonic antigen (CEA), labeled with DyLight 650, were injected into the tail vein of 13 mice. Thirteen mice underwent FGS and 12 mice underwent bright-light surgery (BLS). Weekly GFP fluorescence imaging of the mice was performed to observe tumor recurrence. The extent of residual tumor after BLS was 13-fold greater than after FGS (p < 0.001). Time-course imaging visualized rapid growth of the residual tumor in the BLS group, whereas the FGS group showed only slight tumor growth and significantly improved disease-free survival of the treated mice. Our study demonstrated that FGS significantly reduced residual tumor as well as the recurrence of experimental prostate-cancer bone metastasis. The present results suggest that FGS will be effective for resection of skeletal metastases in selected patients with prostate cancer.

Improved Resection and Outcome of Colon-Cancer Liver Metastasis with Fluorescence-Guided Surgery Using In Situ GFP Labeling with a Telomerase-Dependent Adenovirus in an Orthotopic Mouse Model

Fluorescence-guided surgery (FGS) of cancer is an area of intense development. In the present report, we demonstrate that the telomerase-dependent green fluorescent protein (GFP)-containing adenovirus OBP-401 could label colon-cancer liver metastasis in situ in an orthotopic mouse model enabling successful FGS. OBP-401-GFP-labeled liver metastasis resulted in complete resection with FGS, in contrast, conventional bright-light surgery (BLS) did not result in complete resection of the metastasis. OBP-401-FGS reduced the recurrence rate and prolonged over-all survival compared with BLS. In conclusion, adenovirus OBP-401 is a powerful tool to label liver metastasis in situ with GFP which enables its complete resection, not possible with conventional BLS.

A Fluorescence-Guided Laser Ablation System for Removal of Residual Cancer in a Mouse Model of Soft Tissue Sarcoma

The treatment of soft tissue sarcoma (STS) generally involves tumor excision with a wide margin. Although advances in fluorescence imaging make real-time detection of cancer possible, removal is limited by the precision of the human eye and hand. Here, we describe a novel pulsed Nd:YAG laser ablation system that, when used in conjunction with a previously described molecular imaging system, can identify and ablate cancer in vivo. Mice with primary STS were injected with the protease-activatable probe LUM015 to label tumors. Resected tissues from the mice were then imaged and treated with the laser using the paired fluorescence-imaging/ laser ablation device, generating ablation clefts with sub-millimeter precision and minimal underlying tissue damage. Laser ablation was guided by fluorescence to target tumor tissues, avoiding normal structures. The selective ablation of tumor implants in vivo improved recurrence-free survival after tumor resection in a cohort of 14 mice compared to 12 mice that received no ablative therapy. This prototype system has the potential to be modified so that it can be used during surgery to improve recurrence-free survival in patients with cancer.

Current status and future perspectives of fluorescence-guided surgery for cancer

Curative cancer surgery is dependent on the removal of all primary tumor and metastatic cancer cells. Preoperative imaging, intraoperative inspection and palpation, as well as pathological margin confirmation aid the surgeon, but these methods are lacking in sensitivity and can be highly subjective. Techniques in fluorescence-guided surgery (FGS) are emerging that selectively illuminate cancer cells, enhancing the distinction between tumors and surrounding tissues with the potential for single-cell sensitivity. FGS enhances tumor detection, surgical navigation, margin confirmation, and in some cases can be combined with therapeutic techniques to eliminate microscopic disease. In this review, we describe the preclinical developments and currently-used techniques for FGS.

Fluorescence-Guided Surgery of Liver Metastasis in Orthotopic Nude-Mouse Models

We report here the development of fluorescence-guided surgery of liver metastasis. HT29 human colon cancer cells expressing green fluorescent protein (GFP) were initially injected in the spleen of nude mice. Three weeks later, established liver metastases were harvested and implanted on the left lobe of the liver in other nude mice in order to make an orthotopic liver metastasis model. Fourteen mice with a single liver metastasis were randomized into bright-light surgery (BLS) or fluorescence-guided surgery (FGS) groups. Seven mice were treated with BLS, seven were treated with FGS. Three weeks after implantation, the left lobe of the liver with a single metastasis was exposed through a median abdominal incision. BLS was performed under white light. FGS was performed using a hand-held portable fluorescence imaging system (Dino-Lite). Post-surgical residual tumor fluorescence was visualized with the OV100 Small Animal Imaging System. Residual tumor fluorescence after BLS was clearly visualized at high magnification with the OV100. In contrast, residual tumor fluorescence after FGS was not detected even at high magnification with the OV100. These results demonstrate the feasibility of FGS for liver metastasis.

Precise navigation surgery of tumours in the lung in mouse models enabled by in situ fluorescence labelling with a killer-reporter adenovirus

Background

Current methods of image-guided surgery of tumours of the lung mostly rely on CT. A sensitive procedure of selective tumour fluorescence labelling would allow simple and high-resolution visualisation of the tumour for precise surgical navigation.

Methods

Human lung cancer cell lines H460 and A549 were genetically transformed to express red fluorescent protein (RFP). Tumours were grown subcutaneously for each cell line and harvested and minced for surgical orthotopic implantation on the left lung of nude mice. Tumour growth was measured by fluorescence imaging. After the tumours reached 5 mm in diameter, they were injected under fluorescence guidance with the telomerase-dependent green fluorescent protein (GFP)-containing adenovirus, OBP-401. Viral labelling of the lung tumours with GFP precisely colocalised with tumour RFP expression. Three days after administration of OBP-401, fluorescence-guided surgery (FGS) was performed.

Results

FGS of tumours in the lung was enabled by labelling with a telomerase-dependent adenovirus containing the GFP gene. Tumours in the lung were selectively and brightly labelled. FGS enabled complete lung tumour resection with no residual fluorescent tumour.

Conclusions

FGS of tumours in the lung is feasible and more effective than bright-light surgery.

Improved disease-free survival and overall survival after fluorescence-guided surgery of liver metastasis in an orthotopic nude mouse model

BACKGROUND

In the present study, we sought to determine if fluorescence-guided surgery (FGS) would improve survival compared to standard bright light surgery (BLS) in an experimental colorectal liver metastasis nude mouse model.

METHODS

Orthotopic nude-mouse models of human HT-29-GFP colon cancer liver metastasis were established in the left lobe of the liver of mice. Fourteen mice with a single liver metastasis were randomized into FGS or BLS groups of seven each. FGS of liver metastasis was performed using a hand-held portable fluorescence imaging system (Dino-Lite) to visualize the GFP fluorescence of the metastasis. The BLS- and FGS-treated mice were followed by weekly fluorescence imaging in order to detect recurrence.

RESULTS

The bright fluorescence of GFP provided sufficient illumination to accurately distinguish the margins of the metastasis within the liver. Recurrence occurred in multiple sites including the liver, lung, and other organs in the BLS-treated mice but was significantly reduced in FGS-treated mice. The FGS-treated mice had significantly prolonged disease-free survival (P = 0.001) and overall survival (P = 0.027) compared to BLS-treated mice.

CONCLUSION

The results of the present report demonstrate the feasibility and efficacy of FGS for liver metastasis and suggest its important clinical potential.

Color-coding cancer and stromal cells with genetic reporters in a patient-derived orthotopic xenograft (PDOX) model of pancreatic cancer enhances fluorescence-guided surgery

Precise fluorescence-guided surgery (FGS) for pancreatic cancer has the potential to greatly improve the outcome in this recalcitrant disease. To achieve this goal, we have used genetic reporters to color code cancer and stroma cells in a patient-derived orthotopic xenograft (PDOX) model. The telomerase-dependent green fluorescent protein (GFP)-containing adenovirus OBP-401 was used to label the cancer cells of a pancreatic cancer PDOX. The PDOX was previously grown in a red fluorescent protein (RFP) transgenic mouse that stably labeled the PDOX stroma cells bright red. The color-coded PDOX model enabled FGS to completely resect the pancreatic tumors including stroma. Dual-colored FGS significantly prevented local recurrence, which bright-light surgery or single-color FGS could not. FGS, with color-coded cancer and stroma cells has important potential for improving the outcome of recalcitrant-cancer surgery.

Targeting tumors with a killer-reporter adenovirus for curative fluorescence-guided surgery of soft-tissue sarcoma

Fluorescence-guided surgery (FGS) of cancer is an area of intense interest. However, FGS of cancer has not yet been shown to be curative due to residual microscopic disease. Human fibrosarcoma HT1080 expressing red fluorescent protein (RFP) was implanted orthotopically in the quadriceps femoris muscle of nude mice. The tumor-bearing mice were injected with high and low-dose telomerase-dependent, green fluorescent protein (GFP)-containing adenovirus OBP-401, which labeled the tumor with GFP. Fluorescence-guided surgery (FGS) or bright light surgery (BLS) was then performed. OBP-401 could label soft-tissue sarcoma (STS) with GFP in situ, concordant with RFP. OBP-401-based FGS resulted in superior resection of STS in the orthotopic model of soft-tissue sarcoma, compared to BLS. High-dose administration of OBP-401 enabled FGS without residual sarcoma cells or local or metastatic recurrence, due to its dual effect of cancer-cell labeling with GFP and killing. High-dose OBP-401 based-FGS improved disease free survival (p = 0.00049) as well as preserved muscle function compared with BLS. High-dose OBP-401-based FGS could cure STS, a presently incurable disease. Since the parent virus of OBP-401, OBP-301, has been previously proven safe in a Phase I clinical trial, it is expected the OBP-401-FGS technology described in the present report should be translatable to the clinic in the near future.

Experimental Curative Fluorescence-guided Surgery of Highly Invasive Glioblastoma Multiforme Selectively Labeled With a Killer-reporter Adenovirus

Fluorescence-guided surgery (FGS) of cancer is an area of intense current interest. However, although benefits have been demonstrated with FGS, curative strategies need to be developed. Glioblastoma multiforme (GBM) is one of the most invasive of cancers and is not totally resectable using standard bright-light surgery (BLS) or current FGS strategies. We report here a curative strategy for FGS of GBM. In this study, telomerase-dependent adenovirus OBP-401 infection brightly and selectively labeled GBM with green fluorescent protein (GFP) for FGS in orthotopic nude mouse models. OBP-401-based FGS enabled curative resection of GBM without recurrence for at least 150 days, compared to less than 30 days with BLS.

Application of GFP imaging in cancer

Multicolored proteins have allowed the color-coding of cancer cells growing in vivo and enabled the distinction of host from tumor with single-cell resolution. Non-invasive imaging with fluorescent proteins enabled the dynamics of metastatic cancer to be followed in real time in individual animals. Non-invasive imaging of cancer cells expressing fluorescent proteins has allowed the real-time determination of efficacy of candidate antitumor and antimetastatic agents in mouse models. The use of fluorescent proteins to differentially label cancer cells in the nucleus and cytoplasm can visualize the nuclear-cytoplasmic dynamics of cancer cells in vivo including: mitosis, apoptosis, cell-cycle position, and differential behavior of nucleus and cytoplasm that occurs during cancer-cell deformation and extravasation. Recent applications of the technology described here include linking fluorescent proteins with cell-cycle-specific proteins such that the cells change color from red to green as they transit from G1 to S phases. With the macro- and micro-imaging technologies described here, essentially any in vivo process can be imaged, giving rise to the new field of in vivo cell biology using fluorescent proteins.

Fluorescence-guided surgery of retroperitoneal-implanted human fibrosarcoma in nude mice delays or eliminates tumor recurrence and increases survival compared to bright-light surgery

The aim of this study is to determine if fluorescence-guided surgery (FGS) can eradicate human fibrosarcoma growing in the retroperitoneum of nude mice. One week after retroperitoneal implantation of human HT1080 fibrosarcoma cells, expressing green fluorescent protein (GFP) (HT-1080-GFP), in nude mice, bright-light surgery (BLS) was performed on all tumor-bearing mice (n = 22). After BLS, mice were randomized into 2 treatment groups; BLS-only (n = 11) or the combination of BLS + FGS (n = 11). The residual tumors remaining after BLS were resected with FGS using a hand-held portable imaging system under fluorescence navigation. The average residual tumor area after BLS + FGS was significantly smaller than after BLS-only (0.4 ± 0.4 mm² and 10.5 ± 2.4 mm², respectively; p = 0.006). Five weeks after surgery, the fluorescent-tumor areas of BLS- and BLS + FGS-treated mice were 379 ± 147 mm² and 11.7 ± 6.9 mm², respectively, indicating that FGS greatly inhibited tumor recurrence compared to BLS. The combination of BLS + FGS significantly decreased fibrosarcoma recurrence compared to BLS-only treated mice (p < 0.001). Mice treated with BLS+FGS had a significantly higher disease-free survival rate than mice treated with BLS-only at five weeks after surgery. These results suggest that combination of BLS + FGS significantly reduced the residual fibrosarcoma volume after BLS and improved disease-free survival.

Fluorescence-guided surgery, but not bright-light surgery, prevents local recurrence in a pancreatic cancer patient derived orthotopic xenograft (PDOX) model resistant to neoadjuvant chemotherapy (NAC)

BACKGROUND

The aim of this study is to determine the efficacy of neoadjuvant chemotherapy (NAC) with gemcitabine (GEM) in combination with fluorescence-guided surgery (FGS) on a pancreatic cancer patient derived orthotopic xenograft (PDOX) model.

METHODS

A PDOX model was established from a CEA-positive tumor from a patient who had undergone a pancreaticoduodenectomy for pancreatic adenocarcinoma. Mice were randomized to 4 groups: bright light surgery (BLS) only; BLS + NAC; FGS only; and FGS + NAC. An anti-CEA antibody conjugated to DyLight 650 was administered intravenously via the tail vein of mice with a pancreatic cancer PDOX 24 h before surgery.

RESULTS

The PDOX was clearly labeled with fluorophore-conjugated anti-CEA antibody. Only one out of 8 mice had local recurrence in the FGS only group and zero out of 8 mice had local recurrence in the FGS + NAC which was significantly lower than BLS only or BLS + NAC mice, where local disease recurred in 6 out of 8 mice in each treatment group (p = 0.041 and p = 0.007, respectively). NAC did not significantly reduce recurrence rates when combined with either FGS or BLS.

CONCLUSION

These results indicate that FGS can significantly reduce local recurrence compared to BLS in pancreatic cancer resistant to NAC.

Metastatic recurrence in a pancreatic cancer patient derived orthotopic xenograft (PDOX) nude mouse model is inhibited by neoadjuvant chemotherapy in combination with fluorescence-guided surgery with an anti-CA 19-9-conjugated fluorophore

The aim of this study is to determine the efficacy of neoadjuvant chemotherapy (NAC) with gemcitabine (GEM) in combination with fluorescence-guided surgery (FGS) on a pancreatic cancer patient derived orthotopic xenograft (PDOX) model. A PDOX model was established from a CA19-9-positive, CEA-negative tumor from a patient who had undergone a pancreaticoduodenectomy for pancreatic adenocarcinoma. Mice were randomized to 4 groups: bright light surgery (BLS) only; BLS+NAC; FGS only; and FGS+NAC. An anti-CA19-9 or anti-CEA antibody conjugated to DyLight 650 was administered intravenously via the tail vein of mice with the pancreatic cancer PDOX 24 hours before surgery. The PDOX was brightly labeled with fluorophore-conjugated anti-CA19-9, but not with a fluorophore-conjugated anti-CEA antibody. FGS was performed using the fluorophore-conjugated anti-CA19-9 antibody. FGS had no benefit over BLS to prevent metastatic recurrence. NAC in combination with BLS did not convey an advantage over BLS to prevent metastatic recurrence. However, FGS+NAC significantly reduced the metastatic recurrence frequency to one of 8 mice, compared to FGS only after which metastasis recurred in 6 out of 8 mice, and BLS+NAC with metastatic recurrence in 7 out of 8 mice (p = 0.041). Thus NAC in combination with FGS can reduce or even eliminate metastatic recurrence of pancreatic cancer sensitive to NAC. The present study further emphasizes the power of the PDOX model which enables metastasis to occur and thereby identify the efficacy of NAC in combination with FGS on metastatic recurrence.

Fluorescence-guided surgery improves outcome in an orthotopic osteosarcoma nude-mouse model

In order to develop a model for fluorescence-guided surgery (FGS), 143B human osteosarcoma cells expressing red fluorescent protein (RFP) were injected into the intramedullary cavity of the tibia in nude mice. The fluorescent areas of residual tumors after bright-light surgery (BLS) and FGS were 10.2 ± 2.4 mm(2) and 0.1 ± 0.1 mm(2) , respectively (p<0.001). The BLS-treated mice and BLS+cisplatinum (CDDP)-treated mice had significant recurrence. In contrast, the FGS mice and FGS+CDDP mice had very little recurring tumor growth. Disease-free survival (DFS) in the BLS-, BLS+CDDP-, FGS-, and FGS+CDDP-treated mice was 12.5%, 37.5%, 75.0%, and 87.5%, respectively. The FGS-treated mice had a significantly higher DFS rate than the BLS-treated mice (p=0.021). The FGS+CDDP-treated mice had significantly higher DFS rate than the BLS+CDDP-treated mice (p=0.043). Although chemotherapy significantly reduced multiple metastases (p=0.033), there was no significant correlation between FGS and lung metastasis. FGS significantly reduced the recurrence of the primary tumor but did not reduce lung metastasis. The combination of FGS and adjuvant CDDP reduced tumor recurrence and prevented multiple metastases. FGS and adjuvant chemotherapy should be performed as early as possible in the disease to prevent both recurrence and metastatic development.

Fluorescence-guided surgery of prostate cancer bone metastasis

BACKGROUND

The aim of this study is to investigate the effectiveness of fluorescence-guided surgery (FGS) of prostate cancer experimental skeletal metastasis.

MATERIALS AND METHODS

Green fluorescent protein-expressing PC-3 human prostate cancer cells (PC-3-green fluorescent protein) were injected into the intramedullary cavity of the tibia in 32 nude mice. After 2 wk, 16 of the mice underwent FGS; the other 16 mice underwent bright-light surgery (BLS). Half of BLS and FGS mice (8 mice in each group) received zoledronic acid (ZOL). Weekly fluorescence imaging of the mice was performed. Six weeks after surgery, metastases to lung and inguinal lymph node were evaluated by fluorescence imaging.

RESULTS

The percentage of residual tumor after BLS and FGS was 9.9 ± 2.2% and 0.9 ± 0.3%, respectively (P < 0.001). FGS reduced recurrent cancer growth compared with BLS (P < 0.005). Although FGS alone had no significant effect on inguinal lymph node metastases, lung metastasis or disease-free survival (DFS), ZOL in combination with FGS significantly increased DFS (P = 0.01) in comparison with the combination of BLS and ZOL. ZOL reduced lymph node metastases (P = 0.033) but not lung metastasis.

CONCLUSIONS

FGS significantly reduced recurrence of experimental prostate cancer bone metastasis compared with BLS. The combination of FGS and ZOL increased DFS over BLS and ZOL. ZOL inhibited lymph node metastasis but not lung metastasis.

Ratiometric activatable cell-penetrating peptides label pancreatic cancer, enabling fluorescence-guided surgery, which reduces metastases and recurrence in orthotopic mouse models

BACKGROUND

The aim of this study was to evaluate the efficacy of using matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9)-cleavable ratiometric activatable cell-penetrating peptides (RACPPs) conjugated to Cy5 and Cy7 fluorophores to accurately label pancreatic cancer for fluorescence-guided surgery (FGS) in an orthotopic mouse model.

METHODS

Orthotopic mouse models were established using MiaPaCa-2-GFP human pancreatic cancer cells. Two weeks after implantation, tumor-bearing mice were randomized to conventional white light reflectance (WLR) surgery or FGS. FGS was performed at far-red and infrared wavelengths with a customized fluorescence-dissecting microscope 2 h after injection of MMP-2 and MMP-9-cleavable RACPPs. Green fluorescence imaging of the GFP-labeled cancer cells was used to assess the effectiveness of surgical resection and monitor recurrence. At 8 weeks, mice were sacrificed to evaluate tumor burden and metastases.

RESULTS

Mice in the WLR group had larger primary tumors than mice in the FGS group at termination [1.72 g ± standard error (SE) 0.58 vs. 0.25 g ± SE 0.14; respectively, p = 0.026). Mean disease-free survival was significantly lengthened from 5.33 weeks in the WLR group to 7.38 weeks in the FGS group (p = 0.02). Recurrence rates were lower in the FGS group than in the WLR group (38 vs. 73 %; p = 0.049). This translated into lower local and distant recurrence rates for FGS compared to WLR (31 vs. 67 for local recurrence, respectively, and 25 vs. 60 % for distant recurrence, respectively). Metastatic tumor burden was significantly greater in the WLR group than in the FGS group (96.92 mm(2) ± SE 52.03 vs. 2.20 mm(2) ± SE 1.43; respectively, χ (2) = 5.455; p = 0.02).

CONCLUSIONS

RACPPs can accurately and effectively label pancreatic cancer for effective FGS, resulting in better postresection outcomes than for WLR surgery.

Fluorescence-guided surgery in combination with UVC irradiation cures metastatic human pancreatic cancer in orthotopic mouse models

The aim of this study is to determine if ultraviolet light (UVC) irradiation in combination with fluorescence-guided surgery (FGS) can eradicate metastatic human pancreatic cancer in orthotopic nude–mouse models. Two weeks after orthotopic implantation of human MiaPaCa-2 pancreatic cancer cells, expressing green fluorescent protein (GFP), in nude mice, bright-light surgery (BLS) was performed on all tumor-bearing mice (n = 24). After BLS, mice were randomized into 3 treatment groups; BLS-only (n = 8) or FGS (n = 8) or FGS-UVC (n = 8). The residual tumors were resected using a hand-held portable imaging system under fluorescence navigation in mice treated with FGS and FGS-UVC. The surgical resection bed was irradiated with 2700 J/m² UVC (254 nm) in the mice treated with FGS-UVC. The average residual tumor area after FGS (n = 16) was significantly smaller than after BLS only (n = 24) (0.135±0.137 mm² and 3.338±2.929 mm², respectively; p = 0.007). The BLS treated mice had significantly reduced survival compared to FGS- and FGS-UVC-treated mice for both relapse-free survival (RFS) (p<0.001 and p<0.001, respectively) and overall survival (OS) (p<0.001 and p<0.001, respectively). FGS-UVC-treated mice had increased RFS and OS compared to FGS-only treated mice (p = 0.008 and p = 0.025, respectively); with RFS lasting at least 150 days indicating the animals were cured. The results of the present study suggest that UVC irradiation in combination with FGS has clinical potential to increase survival.

Polyethylene glycol (PEG) linked to near infrared (NIR) dyes conjugated to chimeric anti-carcinoembryonic antigen (CEA) antibody enhances imaging of liver metastases in a nude-mouse model of human colon cancer

We report here that polyethylene glycol (PEG) linked to near infrared dyes conjugated to chimeric mouse-human anti-carcinoembryonic antigen (CEA) antibody greatly improves imaging of liver metastases in a nude mouse model of colon-cancer experimental metastases. PEGylated and non-PEGylated DyLight 650 and 750 dyes were conjugated to the chimeric anti-CEA antibody. The dyes were initially injected intravenously into nude mice without tumors. Tissue biodistribution was determined by tissue sonication and analyzing tissue dye concentration profiles over time. PEGylated dyes had significantly lower accumulation in the liver (p = 0.03 for the 650 dyes; p = 0.002 for the 750 dyes) compared to non-PEGylated dyes. In an experimental liver metastasis model of HT-29 colon cancer, PEGylated dyes conjugated to the anti-CEA antibody showed good labeling of metastatic tumors with high contrast between normal and malignant tissue which was not possible with the non-PEGylated dyes since there was so much non-specific accumulation in the liver. PEGylation of the DyLight 650 and 750 NIR dyes significantly altered tissue biodistribution, allowing brighter tissue labeling, decreased accumulation in normal organs, particularly the liver. This enabled high fidelity and high contrast imaging of liver metastases.

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.

Imaging UVC-induced DNA damage response in models of minimal cancer

We have previously demonstrated that the ultraviolet (UV) light is effective against a variety of cancer cells in vivo as well as in vitro. In the present report, we imaged the DNA damage repair response of minimal cancer after UVC irradiation. DNA-damage repair response to UV irradiation was imaged on tumors growing in 3D culture and in superficial tumors grown in vivo. UV-induced DNA damage repair was imaged with GFP fused to the DNA damage response (DDR)-related chromatin-binding protein 53BP1 in MiaPaCa-2 human pancreatic cancer cells. Three-dimensional Gelfoam® histocultures and confocal imaging enabled 53BP1-GFP nuclear foci to be observed within 1 h after UVC irradiation, indicating the onset of DNA damage repair response. A clonogenic assay showed that UVC inhibited MiaPaCa-2 cell proliferation in a dose-dependent manner, while UVA and UVB showed little effect on cell proliferation. Induction of UV-induced 53BP1-GFP focus formation was limited up to a depth of 40 µm in 3D-culture of MiaPaCa-2 cells. The MiaPaCa-2 cells irradiated by UVC light in a skin-flap mouse model had a significant decrease of tumor growth compared to untreated controls. Our results also demonstrate that 53BP1-GFP is an imageable marker of UV-induced DNA damage repair response of minimal cancer and that UVC is a useful tool for the treatment of residual cancer since UVC can kill superficial cancer cells without damage to deep tissue.

Fluorescently labeled chimeric anti-CEA antibody improves detection and resection of human colon cancer in a patient-derived orthotopic xenograft (PDOX) nude mouse model

BACKGROUND AND OBJECTIVES

The aim of this study was to evaluate a new fluorescently labeled chimeric anti-CEA antibody for improved detection and resection of colon cancer.

METHODS

Frozen tumor and normal human tissue samples were stained with chimeric and mouse antibody-fluorophore conjugates for comparison. Mice with patient-derived orthotopic xenografts (PDOX) of colon cancer underwent fluorescence-guided surgery (FGS) or bright-light surgery (BLS) 24 hr after tail vein injection of fluorophore-conjugated chimeric anti-CEA antibody. Resection completeness was assessed using postoperative images. Mice were followed for 6 months for recurrence.

RESULTS

The fluorophore conjugation efficiency (dye/mole ratio) improved from 3-4 to >5.5 with the chimeric CEA antibody compared to mouse anti-CEA antibody. CEA-expressing tumors labeled with chimeric CEA antibody provided a brighter fluorescence signal on frozen human tumor tissues (P = 0.046) and demonstrated consistently lower fluorescence signals in normal human tissues compared to mouse antibody. Chimeric CEA antibody accurately labeled PDOX colon cancer in nude mice, enabling improved detection of tumor margins for more effective FGS. The R0 resection rate increased from 86% to 96% with FGS compared to BLS.

CONCLUSION

Improved conjugating efficiency and labeling with chimeric fluorophore-conjugated antibody resulted in better detection and resection of human colon cancer in an orthotopic mouse model.

Fluorescence-guided surgery with a fluorophore-conjugated antibody to carcinoembryonic antigen (CEA), that highlights the tumor, improves surgical resection and increases survival in orthotopic mouse models of human pancreatic cancer

BACKGROUND

We have developed a method of distinguishing normal tissue from pancreatic cancer in vivo using fluorophore-conjugated antibody to carcinoembryonic antigen (CEA). The objective of this study was to evaluate whether fluorescence-guided surgery (FGS) with a fluorophore-conjugated antibody to CEA, to highlight the tumor, can improve surgical resection and increase disease-free survival (DFS) and overall survival (OS) in orthotopic mouse models of human pancreatic cancer.

METHODS

We established nude-mouse models of human pancreatic cancer with surgical orthotopic implantation of the human BxPC-3 pancreatic cancer. Orthotopic tumors were allowed to develop for 2 weeks. Mice then underwent bright-light surgery (BLS) or FGS 24 h after intravenous injection of anti-CEA-Alexa Fluor 488. Completeness of resection was assessed from postoperative imaging. Mice were followed postoperatively until premorbid to determine DFS and OS.

RESULTS

Complete resection was achieved in 92 % of mice in the FGS group compared to 45.5 % in the BLS group (p = 0.001). FGS resulted in a smaller postoperative tumor burden (p = 0.01). Cure rates with FGS compared to BLS improved from 4.5 to 40 %, respectively (p = 0.01), and 1-year postoperative survival rates increased from 0 % with BLS to 28 % with FGS (p = 0.01). Median DFS increased from 5 weeks with BLS to 11 weeks with FGS (p = 0.0003). Median OS increased from 13.5 weeks with BLS to 22 weeks with FGS (p = 0.001).

CONCLUSIONS

FGS resulted in greater cure rates and longer DFS and OS using a fluorophore-conjugated anti-CEA antibody. FGS has potential to improve the surgical treatment of pancreatic cancer.

Successful fluorescence-guided surgery on human colon cancer patient-derived orthotopic xenograft mouse models using a fluorophore-conjugated anti-CEA antibody and a portable imaging system

BACKGROUND

Fluorescence-guided surgery (FGS) can enable successful cancer surgery where bright-light surgery often cannot. There are three important issues for FGS going forward toward the clinic: (a) proper tumor labeling, (b) a simple portable imaging system for the operating room, and (c) patient-like mouse models in which to develop the technology. The present report addresses all three.

MATERIALS AND METHODS

Patient colon tumors were initially established subcutaneously in nonobese diabetic (NOD)/severe combined immune deficiency (SCID) mice immediately after surgery. The tumors were then harvested from NOD/SCID mice and passed orthotopically in nude mice to make patient-derived orthotopic xenograft (PDOX) models. Eight weeks after orthotopic implantation, a monoclonal anti-carcinoembryonic antigen (CEA) antibody conjugated with AlexaFluor 488 (Molecular Probes Inc., Eugene, OR) was delivered to the PDOX models as a single intravenous dose 24 hours before laparotomy. A hand-held portable fluorescence imaging device was used.

RESULTS

The primary tumor was clearly visible at laparotomy with the portable fluorescence imaging system. Frozen section microscopy of the resected specimen demonstrated that the anti-CEA antibody selectively labeled cancer cells in the colon cancer PDOX. The tumor was completely resected under fluorescence navigation. Histologic evaluation of the resected specimen demonstrated that cancer cells were not present in the margins, indicating successful tumor resection. The FGS animals remained tumor free for over 6 months.

CONCLUSIONS

The results of the present report indicate that FGS using a fluorophore-conjugated anti-CEA antibody and portable imaging system improves efficacy of resection for CEA-positive colorectal cancer. These data provide the basis for clinical trials.

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.

Specific tumor labeling enhanced by polyethylene glycol linkage of near infrared dyes conjugated to a chimeric anti-carcinoembryonic antigen antibody in a nude mouse model of human pancreatic cancer

Labeling of metastatic tumors can aid in their staging and resection of cancer. Near infrared (NIR) dyes have been used in the clinic for tumor labeling. However, there can be a nonspecific uptake of dye by the liver, lungs, and lymph nodes, which hinders detection of metastasis. In order to overcome these problems, we have used two NIR dyes (DyLight 650 and 750) conjugated to a chimeric anti-carcinoembryonic antigen antibody to evaluate how polyethylene glycol linkage (PEGylation) can improve specific tumor labeling in a nude mouse model of human pancreatic cancer. The conjugated PEGylated and non-PEGylated DyLight 650 and 750 dyes were injected intravenously into non-tumor-bearing nude mice. Serum samples were collected at various time points in order to determine serum concentrations and elimination kinetics. Conjugated PEGylated dyes had significantly higher serum dye concentrations than non-PEGylated dyes (p=0.005 for the 650 dyes and p<0.001 for the 750 dyes). Human pancreatic tumors subcutaneously implanted into nude mice were labeled with antibody-dye conjugates and serially imaged. Labeling with conjugated PEGylated dyes resulted in significantly brighter tumors compared to the non-PEGylated dyes (p<0.001 for the 650 dyes; p=0.01 for 750 dyes). PEGylation of the NIR dyes also decreased their accumulation in lymph nodes, liver, and lung. These results demonstrate enhanced selective tumor labeling by PEGylation of dyes conjugated to a tumor-specific antibody, suggesting their future clinical use in fluorescence-guided surgery.

Comparison of a chimeric anti-carcinoembryonic antigen antibody conjugated with visible or near-infrared fluorescent dyes for imaging pancreatic cancer in orthotopic nude mouse models

The aim of this study was to evaluate a set of visible and near-infrared dyes conjugated to a tumor-specific chimeric antibody for high-resolution tumor imaging in orthotopic models of pancreatic cancer. BxPC-3 human pancreatic cancer was orthotopically implanted into pancreata of nude mice. Mice received a single intravenous injection of a chimeric anti-carcinoembryonic antigen antibody conjugated to one of the following fluorophores: 488-nm group (Alexa Fluor 488 or DyLight 488); 550-nm group (Alexa Fluor 555 or DyLight 550); 650-nm group (Alexa Fluor 660 or DyLight 650), or the 750-nm group (Alexa Fluor 750 or DyLight 755). After 24 h, the Olympus OV100 small-animal imaging system was used for noninvasive and intravital fluorescence imaging of mice. Dyes were compared with respect to depth of imaging, resolution, tumor-to-background ratio (TBR), photobleaching, and hemoglobin quenching. The longer wavelength dyes had increased depth of penetration and ability to detect the smallest tumor deposits and provided the highest TBRs, resistance to hemoglobin quenching, and specificity. The shorter wavelength dyes were more photostable. This study showed unique advantages of each dye for specific cancer imaging in a clinically relevant orthotopic model.

Hand-held high-resolution fluorescence imaging system for fluorescence-guided surgery of patient and cell-line pancreatic tumors growing orthotopically in nude mice

BACKGROUND

In this study, we investigated the advantages of fluorescence-guided surgery (FGS) in mice of a portable hand-sized imaging system compared with a large fluorescence imaging system or a long-working-distance fluorescence microscope.

METHODS

Mouse models of human pancreatic cancer for FGS included the following: (1) MiaPaCa-2-expressing green fluorescent protein, (2) BxPC3 labeled with Alexa Fluor 488-conjucated anti-carcinoembryonic antigen (CEA) antibody, and (3) patient-derived orthotopic xenograft (PDOX) labeled with Alexa Fluor 488-conjugated anti-carbohydrate antigen 19-9 antibody.

RESULTS

Each device could clearly detect the primary MiaPaCa-2-green fluorescent protein tumor and any residual tumor after FGS. In the BxPC3 model labeled with Alexa Fluor 488-conjugated anti-CEA, each device could detect the primary tumor, but the MVX10 could not clearly detect the residual tumor remaining after FGS whereas the other devices could. In the PDOX model labeled with Alexa Fluor 488-conjugated anti-carbohydrate antigen 19-9, only the portable hand-held device could distinguish the residual tumor from the background, and complete resection of the residual tumor was achieved under fluorescence navigation.

CONCLUSIONS

The results described in the present report suggest that the hand-held mobile imaging system can be applied to the clinic for FGS because of its convenient size and high sensitivity which should help make FGS widely used.

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

OBJECTIVES

Screening colonoscopy to monitor for early colitis-associated colon cancer (CAC) is difficult due to the aberrant mucosal patterns associated with long-standing colitis. The aim of this study was to develop a rapid fluorescent detection method for use during colonoscopy for improving the detection of CAC utilising a topically applied enzymatically activatable probe (gGlu-HMRG) which fluoresces in the presence of γ-glutamyltranspeptidase (GGT), an enzyme associated with cancer.

METHODS

Expression of GGT in colon cell lines was examined with fluorescence microscopy and flow cytometry. A mouse model (azoxymethane/dextran sulphate sodium) of CAC was used and mice were examined with white light and fluorescence colonoscopy before and after topical gGlu-HMRG administration.

RESULTS

Expression of GGT, although variable, was higher in human colon cancer cells than normal human colon cells. Using fluorescence colonoscopy in mice, gGlu-HMRG fluorescent lesions were detected 5 min after topical administration and fluorescence persisted for at least 30 min. Fluorescence guided biopsy revealed all fluorescent lesions that contained cancer or dysplasia (n=16), whereas three out of 12 non-fluorescent lesions contained low grade dysplasia and others did not contain neoplastic histology. Microscopic inflammatory infiltration also had variable fluorescence but in general was much lower (∼10-fold) in signal than cancer. Repeat fluorescence endoscopy allowed individual tumours to be monitored.

CONCLUSION

These results suggest that gGlu-HMRG can improve endoscopic detection of CAC with a higher target to background ratio than conventional white light colonoscopy. This could be of benefit to patients with long-standing colitis who must undergo repeated screening colonoscopies.

Polychromatic in vivo imaging of multiple targets using visible and near infrared light

Conventional diagnostic imaging methods such as X-ray CT, MRI, and nuclear medicine are inherently monochromatic meaning that they can depict only one molecular target at a time. Optical imaging has the unique ability to be polychromatic and therefore multi-color imaging employing targeted agents conjugated to fluorophores of varying wavelength enables multiple simultaneous readouts thus providing greater multiplexed information. Numerous successful multicolor imaging techniques have recently been reported using optical imaging in in vivo animal disease models, thus adding to a growing body of research supporting the clinical viability and applicability of these technologies. Herein, we review multicolor optical imaging from the basic chemistry and physics perspective and then extend this to biological and medical applications.