Selective metastatic tumor labeling with green fluorescent protein and killing by systemic administration of telomerase-dependent adenoviruses

Fluorescence-guided assessment of bone and soft-tissue sarcomas for predicting the efficacy of telomerase-specific oncolytic adenovirus

Bone and soft-tissue sarcomas are rare malignancies with histological diversity and tumor heterogeneity, leading to the lack of a common molecular target. Telomerase is a key enzyme for keeping the telomere length and human telomerase reverse transcriptase (hTERT) expression is often activated in most human cancers, including bone and soft-tissue sarcomas. For targeting of telomerase-positive tumor cells, we developed OBP-301, a telomerase-specific replication-competent oncolytic adenovirus, in which the hTERT promoter regulates adenoviral E1 gene for tumor-specific viral replication. In this study, we present the diagnostic potential of green fluorescent protein (GFP)-expressing oncolytic adenovirus OBP-401 for assessing virotherapy sensitivity using bone and soft-tissue sarcomas. OBP-401-mediated GFP expression was significantly associated with the therapeutic efficacy of OBP-401 in human bone and soft-tissue sarcomas. In the tumor specimens from 68 patients, malignant and intermediate tumors demonstrated significantly higher expression levels of coxsackie and adenovirus receptor (CAR) and hTERT than benign tumors. OBP-401-mediated GFP expression was significantly increased in malignant and intermediate tumors with high expression levels of CAR and hTERT between 24 and 48 h after infection. Our results suggest that the OBP-401-based GFP expression system is a useful tool for predicting the therapeutic efficacy of oncolytic virotherapy on bone and soft-tissue sarcomas.

Immuno-hyperthermia effected by antibody-conjugated nanoparticles selectively targets and eradicates individual cancer cells

Hyperthermia has been used for cancer therapy for a long period of time, but has shown limited clinical efficacy. Induction-heating hyperthermia using the combination of magnetic nanoparticles (MNPs) and an alternating magnetic field (AMF), termed magnetic hyperthermia (MHT), has previously shown efficacy in an orthotopic mouse model of disseminated gastric cancer. In the present study, superparamagnetic iron oxide nanoparticles (SPIONs), a type of MNP, were conjugated with an anti-HER2 antibody, trastuzumab and termed anti-HER2-antibody-linked SPION nanoparticles (anti-HER2 SPIONs). Anti-HER2 SPIONs selectively targeted HER2-expressing cancer cells co-cultured along with normal fibroblasts and HER2-negative cancer cells and caused apoptosis only in the HER2-expressing individual cancer cells. The results of the present study show proof-of-concept of a novel hyperthermia technology, immuno-MHT for selective cancer therapy, that targets individual cancer cells.Abbreviations: AMF: alternating magnetic field; DDW: double distilled water; DMEM: Dulbecco's Modified Eagle's; Medium; f: frequency; FBS: fetal bovine serum; FITC: Fluorescein isothiocyanate; GFP: green fluorescent protein; H: amplitude; Hsp: heat shock protein; MHT: magnetic hyperthermia; MNPs: magnetic nanoparticles; PI: propidium iodide; RFP: red fluorescent protein; SPION: superparamagnetic iron oxide (Fe₃O₄) nanoparticle.

Hyperthermia generated by magnetic nanoparticles for effective treatment of disseminated peritoneal cancer in an orthotopic nude-mouse model

Magnetic hyperthermia (MHT), which combines magnetic nanoparticles (MNPs) with an alternating magnetic field (AMF), holds promise as a cancer therapy. There have been many studies about hyperthermia, most of which have been performed by direct injection of MNPs into tumor tissues. However, there have been no reports of treating peritoneal disseminated disease with MHT to date. In the present study, we treated peritoneal metastasis of gastric cancer with MHT using superparamagnetic iron oxide (Fe3O4) nanoparticle (SPION) coated with carboxydextran as an MNP, in an orthotopic mouse model mimicking early peritoneal disseminated disease of gastric cancer. SPIONs of an optimal size were intraperitoneally administered, and an AMF (390 kHz, 28 kAm-1) was applied for 10 minutes, four times every three days. Three weeks after the first MHT treatment, the peritoneal metastases were significantly inhibited compared with the AMF-alone group or the untreated-control group. The results of the present study show that MHT can be applied as a new treatment option for disseminated peritoneal gastric cancer.Abbreviations: AMF: alternating magnetic field; Cy1: cytology-positive; DMEM: Dulbecco's Modified Eagle's Medium; FBS: fetal bovine serum; H&E: hematoxylin and eosin; HIPEC: hyperthermic intraperitoneal chemotherapy; MEM: Minimum Essential Medium; MHT: magnetic hyperthermia; MNPs: magnetic nanoparticles; P0: macroscopic peritoneal dissemination; RFP: red fluorescent protein; SPION: superparamagnetic iron oxide (Fe3O4) nanoparticle.

Real-Time Fluorescence Image-Guided Oncolytic Virotherapy for Precise Cancer Treatment

Oncolytic virotherapy is one of the most promising, emerging cancer therapeutics. We generated three types of telomerase-specific replication-competent oncolytic adenovirus: OBP-301; a green fluorescent protein (GFP)-expressing adenovirus, OBP-401; and Killer-Red-armed OBP-301. These oncolytic adenoviruses are driven by the human telomerase reverse transcriptase (hTERT) promoter; therefore, they conditionally replicate preferentially in cancer cells. Fluorescence imaging enables visualization of invasion and metastasis in vivo at the subcellular level; including molecular dynamics of cancer cells, resulting in greater precision therapy. In the present review, we focused on fluorescence imaging applications to develop precision targeting for oncolytic virotherapy. Cell-cycle imaging with the fluorescence ubiquitination cell cycle indicator (FUCCI) demonstrated that combination therapy of an oncolytic adenovirus and a cytotoxic agent could precisely target quiescent, chemoresistant cancer stem cells (CSCs) based on decoying the cancer cells to cycle to S-phase by viral treatment, thereby rendering them chemosensitive. Non-invasive fluorescence imaging demonstrated that complete tumor resection with a precise margin, preservation of function, and prevention of distant metastasis, was achieved with fluorescence-guided surgery (FGS) with a GFP-reporter adenovirus. A combination of fluorescence imaging and laser ablation using a KillerRed-protein reporter adenovirus resulted in effective photodynamic cancer therapy (PDT). Thus, imaging technology and the designer oncolytic adenoviruses may have clinical potential for precise cancer targeting by indicating the optimal time for administering therapeutic agents; accurate surgical guidance for complete resection of tumors; and precise targeted cancer-specific photosensitization.

Bone and Soft-Tissue Sarcoma: A New Target for Telomerase-Specific Oncolytic Virotherapy

Adenovirus serotype 5 (Ad5) is widely and frequently used as a virus vector in cancer gene therapy and oncolytic virotherapy. Oncolytic virotherapy is a novel antitumor treatment for inducing lytic cell death in tumor cells without affecting normal cells. Based on the Ad5 genome, we have generated three types of telomerase-specific replication-competent oncolytic adenoviruses: OBP-301 (Telomelysin), green fluorescent protein (GFP)-expressing OBP-401 (TelomeScan), and tumor suppressor p53-armed OBP-702. These viruses drive the expression of the adenoviral E1A and E1B genes under the control of the hTERT (human telomerase reverse transcriptase-encoding gene) promoter, providing tumor-specific virus replication. This review focuses on the therapeutic potential of three hTERT promoter-driven oncolytic adenoviruses against bone and soft-tissue sarcoma cells with telomerase activity. OBP-301 induces the antitumor effect in monotherapy or combination therapy with chemotherapeutic drugs via induction of autophagy and apoptosis. OBP-401 enables visualization of sarcoma cells within normal tissues by serving as a tumor-specific labeling reagent for fluorescence-guided surgery via induction of GFP expression. OBP-702 exhibits a profound antitumor effect in OBP-301-resistant sarcoma cells via activation of the p53 signaling pathway. Taken together, telomerase-specific oncolytic adenoviruses are promising antitumor reagents that are expected to provide novel therapeutic options for the treatment of bone and soft-tissue sarcomas.

Advances in delivery vectors for gene therapy in liver cancer

Hepatocellular carcinoma (HCC) is the third most common cause of cancer death globally, mainly due to lack of effective treatments – a problem that gene therapy is poised to solve. Successful gene therapy requires safe and efficient delivery vectors, and recent advances in both viral and nonviral vectors have made an important impact on HCC gene therapy delivery. This review explores how adenoviral, retroviral and adeno-associated viral vectors have been modified to increase safety and delivery capacity, highlighting studies and clinical trials using these vectors for HCC gene therapy. Nanoparticles, liposomes, exosomes and virosomes are also featured in their roles as HCC gene delivery vectors. Finally, new discoveries in gene editing technology and their impacts on HCC gene therapy are discussed.

Visualization of epithelial-mesenchymal transition in an inflammatory microenvironment-colorectal cancer network

Epithelial-mesenchymal transition (EMT) is a biological process by which epithelial cells acquire mesenchymal characteristics. In malignant tumors, EMT is crucial for acquisition of a mesenchymal phenotype with invasive and metastatic properties, leading to tumor progression. An inflammatory microenvironment is thought to be responsible for the development and progression of colorectal cancer (CRC); however, the precise role of inflammatory microenvironments in EMT-related CRC progression remains unclear. Here, we show the spatiotemporal visualization of CRC cells undergoing EMT using a fluorescence-guided EMT imaging system in which the mesenchymal vimentin promoter drives red fluorescent protein (RFP) expression. An inflammatory microenvironment including TNF-α, IL-1β, and cytokine-secreting inflammatory macrophages induced RFP expression in association with the EMT phenotype in CRC cells. In vivo experiments further demonstrated the distribution of RFP-positive CRC cells in rectal and metastatic tumors. Our data suggest that the EMT imaging system described here is a powerful tool for monitoring EMT in inflammatory microenvironment-CRC networks.

Management of Locoregionally Advanced Melanoma

Melanoma has a unique propensity for locoregional metastasis secondary to intralymphatic transit not seen in other cutaneous or soft tissue malignancies. Novel intralesional therapies using oncolytic immunotherapy exhibit increasing response rates with observed bystander effect. Intralesional modalities in combination with systemic immunotherapy are the subject of ongoing clinical trials. Regional therapy is used in isolated limb locoregional metastasis whereby chemotherapy is delivered to an isolated limb avoiding systemic side effects. Multimodal treatment strategy is imperative in the treatment of locoregionally advanced melanoma. One must be versed on these quickly evolving therapeutic options.

Engineered oncolytic viruses to treat melanoma: where are we now and what comes next?

INTRODUCTION

Melanoma treatments have evolved rapidly in the past decade and have included the use of intratumoral injections of engineered oncolytic viruses. One such oncolytic virus is talimogene laherparepvec (T-VEC), which is the first approved therapy of its kind for use in recurrent, unresectable stage IIIB-IVM1a melanoma. Additional oncolytic viruses and their uses in combination with other interventions are currently under investigation.

AREAS COVERED

Oncolytic viruses are being evaluated as immunotherapies for a variety of advanced malignancies. In this article, we review T-VEC, the only FDA-approved engineered oncolytic virus, in addition to ongoing research regarding other oncolytic viruses for the treatment of advanced melanomas. Finally, we discuss opportunities to improve these therapies through viral, host, and tumor-related modifications.

EXPERT OPINION

Engineered and naturally oncolytic viruses have demonstrable local and systemic efficacy as immunotherapies in cancer. T-VEC leads the way with improved survival outcomes for unresectable, stage IIIB-IVM1a melanoma as a monotherapy, and is demonstrating superior results in combination with systemic checkpoint inhibitors. Additional viral vectors show acceptable safety profiles and varying degrees of efficacy in targeting melanoma. The indications for use of oncolytic viruses will expand as their efficacy and appropriate usage is better understood in coming years.

A Flow Cytometry-Based Method to Determine the Titer of Adenoviruses Expressing an Extraneous Gene

In recent times, oncolytic viruses expressing an extraneous gene have attracted great interest; in fact, they have been engaged in multiple applications, such as medicine for cancer. Our group made an oncolytic adenovirus, namely, OBP-301, for use in treating solid cancers and press clinical trial to get approval for a pharmaceutical product. In this study, we applied a flow cytometry-based method to determine the titer of adenoviruses expressing an extraneous gene as well as assess their quality. We considered using the green fluorescent protein (GFP)₅₀ titer as a measure of viral quality. The GFP₅₀ titer (GFP₅₀/mL) is the viral load required to render the HeLa S3 cell line 50% GFP-positive by analysing flow cytometry data. We measured the GFP₅₀ titers for three types of recombinant adenoviruses (OBP-401, OBP-1101, and OBP-1106). We compared GFP₅₀/mL and tissue culture infectious dose (TCID₅₀/mL), a conventional titration index, and found that these titers showed a linear correlation, with a correlation coefficient of >0.9. Moreover, GFP₅₀/mL showed high repetitive accuracy. We expect this flow cytometry-based method to be useful in case of clinically relevant viruses expressing an extraneous gene, in particular, to control viral quality.

Integrated fluorescent cytology with nano-biologics in peritoneally disseminated gastric cancer

Gastric cancer patients positive for peritoneal cytology are at increased risk of tumor recurrence, but although a certain proportion of cytology‐positive patients relapse rapidly with aggressive progression, others survive longer with conventional chemotherapies. This heterogeneity makes it difficult to stratify patients for more intensive therapy and poses a substantial challenge for the implementation of precision medicine. We developed a new approach to identify biologically malignant subpopulations in cytology‐positive gastric cancer patients, using a green fluorescent protein (GFP)‐expressing attenuated adenovirus in which the telomerase promoter regulates viral replication (TelomeScan, OBP‐401). The fluorescence emitted from TelomeScan‐positive cells was successfully quantified using a multi‐mode microplate reader. We then analyzed clinical peritoneal washes obtained from 68 gastric cancer patients and found that patients positive for TelomeScan had a significantly worse prognosis. In 21 cytology‐positive patients, the median survival time of those who were TelomeScan positive (235 days) was significantly shorter than that for those who were TelomeScan negative (671 days; P = 0.0062). This fluorescent virus‐guided cytology detects biologically malignant cancer cells from the peritoneal washes of gastric cancer patients and may thus be useful for both therapy stratification and precision medicine approaches based on genetic profiling of disseminated cells.

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.

Tumor-targeting adenovirus OBP-401 inhibits primary and metastatic tumor growth of triple-negative breast cancer in orthotopic nude-mouse models

Our laboratory previously developed a highly-invasive, triple-negative breast cancer (TNBC) variant using serial orthotopic implantation of the human MDA-MB-231 cell line in nude mice. The isolated variant was highly-invasive in the mammary gland and lymphatic channels and metastasized to lymph nodes in 10 of 12 mice compared to 2 of 12 of the parental cell line. In the present study, the tumor-selective telomerase dependent OBP-401 adenovirus was injected intratumorally (i.t.) (1 × 10⁸ PFU) when the high-metastatic MDA-MB-231 primary tumor expressing red fluorescent protein (MDA-MB-231-RFP) reached approximately 500 mm³ (diameter; 10 mm). The mock-infected orthotopic primary tumor grew rapidly. After i.t. OBP-401 injection, the growth of the orthotopic tumors was arrested. Six weeks after implantation, the fluorescent area and fluorescence intensity showed no increase from the beginning of treatment. OBP-401 was then injected into high-metastatic MDA-MB-231-RFP primary orthotopic tumor growing in mice which already had developed metastasis within lymphatic ducts. All 7 of 7 control mice subsequently developed lymph node metastasis. In contrast, none of 7 mice which received OBP-401 had lymph node metastasis. Seven of 7 control mice also had gross lung metastasis. In contrast, none of the 7 mice which received OBP-401 had gross lung metastasis. Confocal laser microscopy imaging demonstrated that all control mice had diffuse lung metastases. In contrast, all 7 mice which received OBP-401 only had a few metastatic cells in the lung. OBP-401 treatment significantly extended survival of the treated mice.

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

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

Combined therapy of colon carcinomas with an oncolytic adenovirus and valproic acid

The anti-tumor potential of oncolytic adenoviruses (CRAds) has been demonstrated in preclinical and clinical studies. While these agents failed to eradicate tumors when used as a monotherapy, they may be more effective if combined with conventional treatments such as radiotherapy or chemotherapy. This study seeks to evaluate the combination of a CRAd bearing a ∆24 deletion in E1A with valproic acid (VPA), a histone deacetylase inhibitor, for the treatment of human colon carcinomas. This combination led to a strong inhibition of cell growth both in vitro and in vivo compared to treatment with CRAd or VPA alone. This effect did not stem from a better CRAd replication and production in the presence of VPA. Inhibition of cell proliferation and cell death were induced by the combined treatment. Moreover, whereas cells treated only with CRAd displayed a polyploidy (> 4N population), this phenotype was increased in cells treated with both CRAd and VPA. In addition, the increase in polyploidy triggered by combined treatment with CRAd and VPA was associated with the enhancement of H2AX phosphorylation (γH2AX), a hallmark of DNA damage, but also with a decrease of several DNA repair proteins. Finally, viral replication (or E1A expression) was shown to play a key role in the observed effects since no enhancement of polyploidy nor increase in γH2AX were found following cell treatment with a replication-deficient Ad and VPA. Taken together, our results suggest that CRAd and VPA could be used in combination for the treatment of colon carcinomas.

Therapeutic Cell-Cycle-Decoy Efficacy of a Telomerase-Dependent Adenovirus in an Orthotopic Model of Chemotherapy-Resistant Human Stomach Carcinomatosis Peritonitis Visualized With FUCCI Imaging

We have established an orthotopic nude-mouse model of gastric cancer carcinomatosis peritonitis, a recalcitrant disease in human patients. Human MKN45 poorly-differentiated human gastric cancer cells developed carcinomatosis peritonitis upon orthotopic transplantation in nude mice. The MKN45 cells expressed the fluorescent ubiquitination-based cell cycle indicator (FUCCI) that color codes the phases of the cell cycle. The intra-peritoneal tumors and ascites contained mostly quiescent G₁ /G_o cancer cells visualized as red by FUCCI imaging. Cisplatinum (CDDP) treatment did not reduce bloody ascites, and larger tumors formed in the peritoneal cavity after CDDP treatment in an early-stage carcinomatosis peritonitis orthotopic mouse model. Paclitaxel-treated mice had reduced ascites, but also had large tumor masses in the peritonium after treatment with cancer cells mostly in G₀ /G₁ , visualized by FUCCI red. In contrast, OBP-301 telomerase-dependent adenovirus-treated mice had no ascites and only small tumor nodules consisting of cancer cells mostly in S/G₂ phases in the early-stage carcinomatosis peritonitis model, visualized by FUCCI green. Furthermore, OBP-301 significantly reduced the size of tumors (P < 0.01) and ascites even in a late-stage carcinomatosis peritonitis model. These results suggest that quiescent peritoneally-disseminated gastric cancer cells are resistant to conventional chemotherapy, but OBP-301 significantly reduced the weight of the tumors and increased survival, suggesting clinical potential. J. Cell. Biochem. 118: 3635-3642, 2017. © 2016 Wiley Periodicals, Inc.

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.

Creation of a murine orthotopic hepatoma model with intra-abdominal metastasis

AIM

To create an orthotopic hepatoma model with local metastasis monitored with ultrasound could be created as a platform for testing new treatments.

BACKGROUND

Hepatoma accounts for 25% of liver tumors in children with poor overall survival. Intraabdominal metastasis are present in 35% of patients at time of diagnosis. We hypothesized that an orthotopic tumor model with local metastasis could be created as a platform for testing treatment modalities and could be monitored with ultrasound.

PATIENTS AND METHODS

One million human hepatoma cells (Hep3B) were injected into the left lobe of the liver of immunocompromised mice. Tumor volume was monitored with high frequency-ultrasound until it reached 1,000mm(3). At that time animals were sacrificed and examined for gross metastatic disease. Tumor sections were analyzed with hematoxylin and eosin (H&E) staining.

RESULTS

Tumor formed in 8/15 mice. The tumor was detected as small as 19.59mm(3) on ultrasound. Of the forming tumors, tumor size was 145±177.93mm(3) at 60 days post-injection, 665±650.39mm(3) at 67 days, and reached >1000mm(3) by 76.6±9.9 days. At necropsy, four mice (50%) had tumor only within the liver, four (50%) had additional tumors in omentum, pelvis and peritoneum. H&E showed tumor within the normal liver parenchyma, with multiple mitotic figures, small areas of necrosis, and hemorrhage within the tumor.

CONCLUSION

We have successfully established an orthotopic hepatoma murine model, with a local metastatic rate of 50%. Non-invasive tumor monitoring is feasible via ultrasound.

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.

Targeted Photodynamic Virotherapy Armed with a Genetically Encoded Photosensitizer

Photodynamic therapy (PDT) is a minimally invasive antitumor therapy that eradicates tumor cells through a photosensitizer-mediated cytotoxic effect upon light irradiation. However, systemic administration of photosensitizer often makes it difficult to avoid a photosensitive adverse effect. The red fluorescent protein KillerRed generates reactive oxygen species (ROS) upon green light irradiation. Here, we show the therapeutic potential of a novel tumor-specific replicating photodynamic viral agent (TelomeKiller) constructed using the human telomerase reverse transcriptase (hTERT) promoter. We investigated the light-induced antitumor effect of TelomeKiller in several types of human cancer cell lines. Relative cell viability was investigated using an XTT assay. The in vivo antitumor effect was assessed using subcutaneous xenografted tumor and lymph node metastasis models. KillerRed accumulation resulted in ROS generation and apoptosis in light-irradiated cancer cells. Intratumoral injection of TelomeKiller efficiently delivered the KillerRed protein throughout the tumors and exhibited a long-lasting antitumor effect with repeated administration and light irradiation in mice. Moreover, intratumorally injected TelomeKiller could spread into the regional lymph node area and eliminate micrometastasis with limited-field laser irradiation. Our results suggest that KillerRed has great potential as a novel photosensitizer if delivered with a tumor-specific virus-mediated delivery system. TelomeKiller-based PDT is a promising antitumor strategy to efficiently eradicate tumor cells.

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.

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.

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.

Biological ablation of sentinel lymph node metastasis in submucosally invaded early gastrointestinal cancer

Currently, early gastrointestinal cancers are treated endoscopically, as long as there are no lymph node metastases. However, once a gastrointestinal cancer invades the submucosal layer, the lymph node metastatic rate rises to higher than 10%. Therefore, surgery is still the gold standard to remove regional lymph nodes containing possible metastases. Here, to avoid prophylactic surgery, we propose a less-invasive biological ablation of lymph node metastasis in submucosally invaded gastrointestinal cancer patients. We have established an orthotopic early rectal cancer xenograft model with spontaneous lymph node metastasis by implantation of green fluorescent protein (GFP)-labeled human colon cancer cells into the submucosal layer of the murine rectum. A solution containing telomerase-specific oncolytic adenovirus was injected into the peritumoral submucosal space, followed by excision of the primary rectal tumors mimicking the endoscopic submucosal dissection (ESD) technique. Seven days after treatment, GFP signals had completely disappeared indicating that sentinel lymph node metastasis was selectively eradicated. Moreover, biologically treated mice were confirmed to be relapse-free even 4 weeks after treatment. These results indicate that virus-mediated biological ablation selectively targets lymph node metastasis and provides a potential alternative to surgery for submucosal invasive gastrointestinal cancer patients.

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.

Advantages of fluorescence-guided laparoscopic surgery of pancreatic cancer labeled with fluorescent anti-carcinoembryonic antigen antibodies in an orthotopic mouse model

BACKGROUND

Our laboratory has previously developed fluorescence-guided surgery of pancreatic and other cancers in orthotopic mouse models. Laparoscopic surgery is being used more extensively in surgical oncology. This report describes the efficacy of laparoscopic fluorescence-guided surgery of pancreatic cancer in an orthotopic mouse model.

STUDY DESIGN

Mouse models of human pancreatic cancer were established with fragments of the BxPC-3 red fluorescent protein-expressing human pancreatic cancer using surgical orthotopic implantation. Mice were randomized to bright-light laparoscopic surgery (BLLS) or to fluorescence-guided laparoscopic surgery (FGLS). Fluorescence-guided laparoscopic surgery was performed with a light-emitting diode light source through a 495-nm emission filter in order to resect the primary tumors and any additional separate submillimeter tumor deposits within the pancreas, the latter of which was not possible with BLLS. Tumors were labeled with anti-CEA AlexaFluor 488 antibodies 24 hours before surgery with intravenous injection. Perioperative fluorescence images were obtained to evaluate tumor size. Mice were followed postoperatively to assess for recurrence and at termination to evaluate tumor burden.

RESULTS

At termination, the FGLS-treated mice had less pancreatic tumor volume than the BLLS-treated mice (5.75 mm(2) vs 28.43 mm(2), respectively; p = 0.012) and lower tumor weight (21.1 mg vs 174.4 mg, respectively; p = 0.033). Fluorescence-guided laparoscopic surgery compared with BLLS also decreased local recurrence (50% vs 80%, respectively; p = 0.048) and distant recurrence (70% vs 95%, respectively; p = 0.046). More mice in the FGLS group than the BLLS group were free of tumor at termination (25% vs 5%, respectively). Median disease-free survival was lengthened from 2 weeks with BLLS (95% CI, 1.635-2.365) to 7 weeks with FGLS (95% CI, 5.955-8.045; p = 0.001).

CONCLUSIONS

Fluorescence-guided laparoscopic surgery is more effective than BLLS and, therefore, has important potential for surgical oncology.

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.

Imageable clinically relevant mouse models of metastasis

In the past 10 years, we have developed a new approach to the development of a clinically accurate rodent model for human cancer based on our invention of surgical orthotopic implantation (SOI). The SOI models have been described in approx. 70 publications and in 4 patents.*SOI allows human tumors of all the major types of human cancer to reproduce clinical like tumor growth and metastasis in the transplanted rodents. The major features of the SOI models are reviewed here and also compared to transgenic mouse models of cancer.

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.

Conditionally replicative adenoviral vectors for imaging the effect of chemotherapy on pancreatic cancer cells

Pancreatic cancer has a poor prognosis after complete macroscopic resection combined with chemotherapy. Even after neoadjuvant chemotherapy, R0 resection is often not possible. Moreover, current imaging techniques cannot reliably distinguish viable cancer cells from scar tissue at the resectional margin. We investigated the use of a conditionally replicative adenovirus (CRAd), Ad5/3Cox2CRAd-ΔE3ADP-Luc, for imaging the effects of chemotherapy. The CRAd infectivity of pancreatic cancer cells was enhanced by a chimeric Ad5/3 fiber, E1A expression was under the control of the Cox2 promoter, and the luciferase gene was inserted adjacent to the adenovirus death protein (ADP) gene. Subcutaneous xenografts of the pancreatic cancer cell line MiaPaCa-2 were established in 24 BALB/c nu/nu mice. When xenografts reached a diameter of 4-6 mm (day 1), the mice were injected i.p. with either PBS (group A; n = 12) or 1000 mg/kg gemcitabine (group B; n = 12), weekly. On days 19, 26, 33, and 40, CRAd were injected intratumorally into three mice in groups A and B. Bioluminescence was imaged 72 h after CRAd injection, and gross tumor volumes were measured then tumors were removed for ex vivo histopathology using H&E and Ki-67 staining. Correlations between gross tumor volume, pathological evaluation of the percentage of viable tumor area, and CRAd bioluminescence were analyzed. Bioluminescence correlated closely with the percentage of viable tumor area (R = 0.96), but not with gross tumor volume (R = 0.31). Therefore, CRAds might be reliable imaging tools for monitoring chemotherapy in pancreatic cancer, and could improve our ability to distinguish viable tumor cells from scar tissue.

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.

Oncolytic virotherapy: the questions and the promise

Oncolytic virotherapy is a new strategy to reduce tumor burden through selective virus replication in rapidly proliferating cells. Oncolytic viruses are members of at least ten virus families, each with its advantages and disadvantages. Here, I briefly review the recent advances and key challenges, as exemplified by the best-studied platforms. Recent advances include preclinical proof of feasibility, clinical evidence of tolerability and effectiveness, and the development of new strategies to improve efficacy. These include engineered tumor selectivity and expression of antitumorigenic genes that could function independently of virus replication, identification of combinatorial therapies that accelerate intratumoral virus propagation, and modification of immune responses and vascular delivery for treatment of metastatic disease. Key challenges are to select "winners" from the distinct oncolytic platforms that can stimulate anti-cancer immunity without affecting virus replication and can lyse cancer stem cells, which are most likely responsible for tumor maintenance, aggressiveness, and recurrence. Preventing the emergence of resistant tumor cells during virotherapy through the activation of multiple death pathways, the development of a better understanding of the mechanisms of cancer stem-cell lysis, and the development of more meaningful preclinical animal models are additional challenges for the next-generation of engineered viruses.

Short PEG-linkers improve the performance of targeted, activatable monoclonal antibody-indocyanine green optical imaging probes

The ability to switch optical imaging probes from the quenched (off) to the active state (on) has greatly improved target to background ratios. The optimal activation efficiency of an optical probe depends on complete quenching before activation and complete dequenching after activation. For instance, monoclonal antibody-indocyanine green (mAb-ICG) conjugates, which are promising agents for clinical translation, are normally quenched, but can be activated when bound to a cell surface receptor and internalized. However, the small fraction of commonly used ICG derivative (ICG-Sulfo-OSu) can bind noncovalently to its mAb and is, thus, gradually released from the mAb leading to relatively high background signal especially in the liver and the abdomen. In this study, we re-engineered a mAb-ICG conjugate, (Panitumumab-ICG) using bifunctional ICG derivatives (ICG-PEG4-Sulfo-OSu and ICG-PEG8-Sulfo-OSu) with short polyethylene glycol (PEG) linkers. Higher covalent binding (70-86%) was observed using the bifunctional ICG with short PEG linkers resulting in less in vivo noncovalent dissociation. Panitumumab-ICG conjugates with short PEG linkers were able to detect human epidermal growth factor receptor 1 (EGFR)-positive tumors with high tumor-to-background ratios (15.8 and 6.9 for EGFR positive tumor-to-negative tumor and tumor-to-liver ratios, respectively, at 3 d postinjection).

In vivo breast cancer characterization imaging using two monoclonal antibodies activatably labeled with near infrared fluorophores

Introduction

The gene expression profiles of cancer cells are closely related to their aggressiveness and metastatic potential. Antibody-based immunohistochemistry (IHC) of tissue specimens is a common method of identifying expressed proteins in cancer cells and increasingly inform treatment decisions. Molecular imaging is a potential method of performing similar IHC studies in vivo without the requirement for biopsy or tumor excision. To date, antibody-based imaging has been limited by high background levels related to slow clearance, making such imaging practical. However, optically activatable imaging agents, which are only fluorescent when bound to their cognate receptor, open the possibility of doing in vivo multi-color IHC.

Methods

We describe the use of activatable, near infrared fluorescence-labeled AlexaFluor680 (Alexa680) conjugated panitumumab (Pan) targeted against human epidermal growth factor receptor (EGFR) (Pan-Alexa680) and Indocyanine Green (ICG) conjugated trastuzumab (Tra) targeted against human epidermal growth factor receptor type 2 (HER2) (Tra-ICG) were synthesized and evaluated in cells in vitro and in an orthotopic breast cancer mouse model in vivo.

Results

Pan-Alexa680 (self-quenched; SQ) and Tra-ICG were initially quenched but demonstrated a 5.2- and 50-fold dequenching capacity under detergent treatment, respectively. In vitro microscopy and flow cytometry using MDA-MB-468 (EGFR+/HER2-) and 3T3/HER2 cells (EGFR-/HER2+), demonstrated specific fluorescence signal for each cell type based on binding to Pan-Alexa680(SQ) or Tra-ICG. An in vivo imaging study employing a cocktail of Pan-Alexa680(SQ) and Tra-ICG (each 50 μg) was injected into mice with orthotopic MDA-MB-468 and 3T3/HER2 tumors in the breast. Each probe visualized only the target-specific breast tumor.

Conclusions

Multi-color target-specific fluorescence breast cancer imaging can be achieved in vivo by employing two activatable fluorescent probes administered as a cocktail. The images allowed us to see a specific receptor expression in each breast tumor without post-image processing.

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.

In vivo bioluminescent imaging of α-fetoprotein-producing hepatocellular carcinoma in the diethylnitrosamine-treated mouse using recombinant adenoviral vector

BACKGROUND

The in vivo molecular imaging method is a useful tool for monitoring carcinogenesis in various hepatocellular carcinoma (HCC) models, such as xenografted-, chemical induced- and transgenic mice. The tumor-specific gene expression strategy, such as transcriptional targeting, is essential for achieving a lower toxicity for normal liver tissue in therapy and the monitoring of tumor progression in diagnosis, respectively. The present study aimed to visualize spontaneously developing α-fetoprotein (AFP)-producing HCC through targeted gene expression in tumors using recombinant adenoviral vector.

METHODS

The recombinant adenovirus vector, AdAFPfLuc (containing firefly luciferase gene driven by human AFP enhancer/promoter) was prepared. After in vitro infection by adenovirus, gene expression was confirmed using the luciferase assay, semi-quantitative reverse transcriptase-polymerase chain reaction and western blotting in AFP-producing and nonproducing cells. Tumor-bearing mice were intravenously injected with adenovirus, and bioluminescent images were obtained.

RESULTS

The expression of fLuc was efficiently demonstrated by the luciferase assay in AFP-producing cells but not in AFP-nonproducing cells. AFP-producing HCC targeted gene expression was confirmed at the mRNA and protein levels. After being injected intravenously in HuH-7 xenografts and HCC-bearing diethylnitrosamine-treated mice using adenovirus, functional reporter gene expression was confirmed in tumors by in vivo bioluminescent imaging (BLI).

CONCLUSIONS

The recombinant adenovirus vector system can be used to monitor spontaneously developing AFP-producing HCC and to evaluate targeted gene expression in tumors by in vivo BLI in a small animal model.

Orthotopic mouse models expressing fluorescent proteins for cancer drug discovery

IMPORTANCE OF THE FIELD

Currently used rodent tumor models, including transgenic tumor models, or subcutaneously growing human tumors in immunodeficient mice, do not sufficiently represent clinical cancer, especially with regard to metastasis and drug sensitivity.

AREAS COVERED IN THIS REVIEW

To obtain clinically accurate models, we have developed the technique of surgical orthotopic implantation (SOI) to transplant histologically intact fragments of human cancer, including tumors taken directly from the patient, to the corresponding organ of immunodeficient rodents. SOI allows the growth and metastatic potential of the transplanted tumors to be expressed and reflects clinical cancer of all types. Effective drugs can be discovered and evaluated in the SOI models utilizing human tumor cell lines and patient tumors. Visualization of many aspects of cancer initiation and progression in vivo has been achieved with fluorescent proteins. Tumors and metastases in the SOI models that express fluorescent proteins can be visualized noninvasively in intact animals, greatly facilitating drug discovery.

WHAT THE READER WILL GAIN

This review will provide information on the imageable mouse models of cancer that are clinically relevant, especially regarding metastasis and their use for drug discovery and evaluation.

TAKE HOME MESSAGE

SOI mouse models of cancer reproduce the features of clinical cancer.

Chapter five--The development of transcription-regulated adenoviral vectors with high cancer-selective imaging capabilities

A clear benefit of molecular imaging is to enable noninvasive, repetitive monitoring of intrinsic signals within tumor cells as a means to identify the lesions as malignant or to assess the ability of treatment to perturb key pathways within the tumor cells. Due to the promising utility of molecular imaging in oncology, preclinical research to refine molecular imaging techniques in small animals is a blossoming field. We will first discuss the several imaging modalities such as fluorescent imaging, bioluminescence imaging, and positron emission tomography that are now commonly used in small animal settings. The indirect imaging approach, which can be adapted to a wide range of imaging reporter genes, is a useful platform to develop molecular imaging. In particular, reporter gene-based imaging is well suited for transcriptional-targeted imaging that can be delivered by recombinant adenoviral vectors. In this review, we will summarize transcription-regulated strategies used in adenoviral-mediated molecular imaging to visualize metastasis and monitor oncolytic therapy in preclinical models.

Fluorescence-guided surgery of human colon cancer increases complete resection resulting in cures in an orthotopic nude mouse model

BACKGROUND

We inquired if fluorescence-guided surgery (FGS) could improve surgical outcomes in fluorescent orthotopic nude mouse models of human colon cancer.

METHODS

We established fluorescent orthotopic mouse models of human colon cancer expressing a fluorescent protein. Tumors were resected under bright light surgery (BLS) or FGS. Pre- and post-operative images with the OV-100 Small Animal Imaging System (Olympus Corp, Tokyo Japan) were obtained to assess the extent of surgical resection.

RESULTS

All mice with primary tumor that had undergone FGS had complete resection compared with 58% of mice in the BLS group (P = 0.001). FGS resulted in decreased recurrence compared with BLS (33% versus 62%, P = 0.049) and lengthened disease-free median survival from 9 to >36 wk. The median overall survival increased from 16 wk in the BLS group to 31 weeks in the FGS group. FGS resulted in a cure in 67% of mice (alive without evidence of tumor at >6 mo after surgery) compared with only 37% of mice that underwent BLS (P = 0.049).

CONCLUSIONS

Surgical outcomes in orthotopic nude mouse models of human colon cancer were significantly improved with FGS. The present study can be translated to the clinic by various effective methods of fluorescently labeling tumors.

Galactosyl human serum albumin-NMP1 conjugate: a near infrared (NIR)-activatable fluorescence imaging agent to detect peritoneal ovarian cancer metastases

Patient survival depends on the completeness of resection of peritoneal ovarian cancer metastases (POCM), and therefore, it is important to develop methods to enhance detection. Previous probe designs based on activatable galactosyl human serum albumin (hGSA)-fluorophore pairs, which target lectin receptors expressed on POCM, have used only visible range dyes conjugated to hGSA. However, imaging probes emitting fluorescence in the NIR range are advantageous because NIR photons have deeper in vivo tissue penetration and result in lower background autofluorescence than those emitting in the visible range. A NIR-activatable hGSA fluorophore was synthesized using a bacteriochlorin-based dye, NMP1. NMP1 has two unique absorption peaks, one in the green range and the other in the NIR range, but emits at a NIR peak of 780 nm. NMP1, thus, has two different Stokes shifts that have the potential to allow imaging of POCM both at the peritoneal surface and just below it. hGSA was conjugated with 2 NMP1 molecules to create a self-quenching complex (hGSA-NMP1). The activation ratio of hGSA-NMP1 was measured by the fluorescence intensity before and after exposure to 10% SDS. The activation ratio of hGSA-NMP1 was ~100-fold in vitro. Flow cytometry, fluorescence microscopy, and in vivo spectral fluorescence imaging were carried out to compare hGSA-NMP1 with hGSA-IR800 and hGSA-ICG (two always-on control agents with similar emission to NMP1) in terms of comparative fluorescence signal and the ability to detect POCM in mice models. The sensitivity and specificity of hGSA-NMP1 for POCM implant detection were determined by colocalizing NMP1 emission spectra with red fluorescent protein (RFP) expressed constitutively in SHIN3 tumor implants at different depths below the peritoneal surface. In vitro, SHIN3 cells were easily detectable after 3 h of incubation with hGSA-NMP1. In vivo submillimeter POCM foci were clearly detectable with spectral fluorescence imaging using hGSA-NMP1. Among 555 peritoneal lesions, hGSA-NMP, using NIR and green excitation light, respectively, detect 75% of all lesions and 91% of lesions ~0.8 mm or greater in diameter. Few false positives were encountered. Nodules located at a depth below the small bowel surface were only depicted with hGSA-NMP1. We conclude that hGSA-NMP1 is useful in imaging peritoneal ovarian cancer metastases, located both superficially and deep in the abdominal cavity.

Fluorescence-guided surgery allows for more complete resection of pancreatic cancer, resulting in longer disease-free survival compared with standard surgery in orthotopic mouse models

BACKGROUND

Negative surgical margins are vital to achieve cure and prolong survival in patients with pancreatic cancer. We inquired if fluorescence-guided surgery (FGS) could improve surgical outcomes and reduce recurrence rates in orthotopic mouse models of human pancreatic cancer.

STUDY DESIGN

A randomized active-control preclinical trial comparing bright light surgery (BLS) to FGS was used. Orthotopic mouse models of human pancreatic cancer were established using the BxPC-3 pancreatic cancer cell line expressing red fluorescent protein (RFP). Two weeks after orthotopic implantation, tumors were resected with BLS or FGS. Pre- and postoperative images were obtained with the OV-100 Small Animal Imaging System to assess completeness of surgical resection in real time. Postoperatively, noninvasive whole body imaging was done to assess recurrence and follow tumor progression. Six weeks postoperatively, mice were sacrificed to evaluate primary pancreatic and metastatic tumor burden at autopsy.

RESULTS

A more complete resection of pancreatic cancer was achieved using FGS compared with BLS: 98.9% vs 77.1%, p = 0.005. The majority of mice undergoing BLS (63.2%) had evidence of gross disease with no complete resections; 20% of mice undergoing FGS had complete resection and an additional 75% had only minimal residual disease (p = 0.0001). The mean postoperative tumor burden was significantly less with FGS compared with BLS: 0.08 ± 0.06 mm(2) vs 2.64 ± 0.63 mm(2), p = 0.001. The primary tumor burden at termination was significantly less with FGS compared with BLS: 19.3 ± 5.3 mm(2) vs 6.2 ± 3.6 mm(2), p = 0.048. FGS resulted in significantly longer disease-free survival than BLS (p = 0.02, hazard ratio = 0.39, 95% CI 0.17, 0.88).

CONCLUSIONS

Surgical outcomes were improved in pancreatic cancer using fluorescence-guidance. This novel approach has significant potential to improve surgical treatment of cancer.

Cancer imaging: Gene transcription-based imaging and therapeutic systems

Molecular-genetic imaging of cancer is in its infancy. Over the past decade gene reporter systems have been optimized in preclinical models and some have found their way into the clinic. The search is on to find the best combination of gene delivery vehicle and reporter imaging system that can be translated safely and quickly. The goal is to have a combination that can detect a wide variety of cancers with high sensitivity and specificity in a way that rivals the current clinical standard, positron emission tomography with [(18)F]fluorodeoxyglucose. To do so will require systemic delivery of reporter genes for the detection of micrometastases, and a nontoxic vector, whether viral or based on nanotechnology, to gain widespread acceptance by the oncology community. Merger of molecular-genetic imaging with gene therapy, a strategy that has been employed in the past, will likely be necessary for such imaging to reach widespread clinical use.

An LED light source and novel fluorophore combinations improve fluorescence laparoscopic detection of metastatic pancreatic cancer in orthotopic mouse models

BACKGROUND

The aim of this study was to improve fluorescence laparoscopy of pancreatic cancer in an orthotopic mouse model with the use of a light-emitting diode (LED) light source and optimal fluorophore combinations.

STUDY DESIGN

Human pancreatic cancer models were established with fluorescent FG-RFP, MiaPaca2-GFP, BxPC-3-RFP, and BxPC-3 cancer cells implanted in 6-week-old female athymic mice. Two weeks postimplantation, diagnostic laparoscopy was performed with a Stryker L9000 LED light source or a Stryker X8000 xenon light source 24 hours after tail-vein injection of CEA antibodies conjugated with Alexa 488 or Alexa 555. Cancer lesions were detected and localized under each light mode. Intravital images were also obtained with the OV-100 Olympus and Maestro CRI Small Animal Imaging Systems, serving as a positive control. Tumors were collected for histologic analysis.

RESULTS

Fluorescence laparoscopy with a 495-nm emission filter and an LED light source enabled real-time visualization of the fluorescence-labeled tumor deposits in the peritoneal cavity. The simultaneous use of different fluorophores (Alexa 488 and Alexa 555), conjugated to antibodies, brightened the fluorescence signal, enhancing detection of submillimeter lesions without compromising background illumination. Adjustments to the LED light source permitted simultaneous detection of tumor lesions of different fluorescent colors and surrounding structures with minimal autofluorescence.

CONCLUSIONS

Using an LED light source with adjustments to the red, blue, and green wavelengths, it is possible to simultaneously identify tumor metastases expressing fluorescent proteins of different wavelengths, which greatly enhanced the signal without compromising background illumination. Development of this fluorescence laparoscopy technology for clinical use can improve staging and resection of pancreatic cancer.

A simple detection system for adenovirus receptor expression using a telomerase-specific replication-competent adenovirus

Adenovirus serotype 5 (Ad5) is frequently used as an effective vector for induction of therapeutic transgenes in cancer gene therapy or of tumor cell lysis in oncolytic virotherapy. Ad5 can infect target cells through binding with the coxsackie and adenovirus receptor (CAR). Thus, the infectious ability of Ad5-based vectors depends on the CAR expression level in target cells. There are conventional methods to evaluate the CAR expression level in human target cells, including flow cytometry, western blotting and immunohistochemistry. Here, we show a simple system for detection and assessment of functional CAR expression in human tumor cells, using the green fluorescent protein (GFP)-expressing telomerase-specific replication-competent adenovirus OBP-401. OBP-401 infection induced detectable GFP expression in CAR-expressing tumor cells, but not in CAR-negative tumor cells, nor in CAR-positive normal fibroblasts, 24 h after infection. OBP-401-mediated GFP expression was significantly associated with CAR expression in tumor cells. OBP-401 infection detected tumor cells with low CAR expression more efficiently than conventional methods. OBP-401 also distinguished CAR-positive tumor tissues from CAR-negative tumor and normal tissues in biopsy samples. These results suggest that GFP-expressing telomerase-specific replication-competent adenovirus is a very potent diagnostic tool for assessment of functional CAR expression in tumor cells for Ad5-based antitumor therapy.

Tumor-selective, adenoviral-mediated GFP genetic labeling of human cancer in the live mouse reports future recurrence after resection

We have previously developed a telomerase-specific replicating adenovirus expressing GFP (OBP-401), which can selectively label tumors in vivo with GFP. Intraperitoneal (i.p.) injection of OBP-401 specifically labeled peritoneal tumors with GFP, enabling fluorescence visualization of the disseminated disease and real-time fluorescence surgical navigation. However, the technical problems with removing all cancer cells still remain, even with fluorescence-guided surgery. In this study, we report imaging of tumor recurrence after fluorescence-guided surgery of tumors labeled in vivo with the telomerase-dependent, GFP-containing adenovirus OBP-401.. Recurrent tumor nodules brightly expressed GFP, indicating that initial OBP-401-GFP labeling of peritoneal disease was genetically stable, such that proliferating residual cancer cells still express GFP. In situ tumor labeling with a genetic reporter has important advantages over antibody and other non-genetic labeling of tumors, since residual disease remains labeled during recurrence and can be further resected under fluorescence guidance.