Background: Pediatric High-grade gliomas (pHGGs) are the No.1 cause of cancer-related deaths in children with median survival of less than a year. pHGGs tend to be infiltrative and appear irregularly shaped with ill-defined borders difficult to be distinguished from surrounding normal brain tissue. As the extent of surgical resection predicts survival, precise tumor removal with more accurate margin delineation means better treatment outcome and less loss of vital functions. While EGFR is one of the most commonly amplified genes in pHGGs, its protein-level expression is not as well characterized as in adult HGGs. Previously, near-infrared (NIR) dye labeled epidermal growth factor receptor (EGFR) antibody has served as contrast agent in fluorescence-guided surgery of head and neck cancer. However, it must overcome the blood-brain barrier (BBB) for effective intratumoral delivery in the case of brain cancer. Therefore, the latest advancement in reversible BBB opening with tight junction protein modulation has the potential to enable the molecular targeted imaging guidance of pHGG resection.
Aims: The current study aimed to improve intratumoral delivery of NIR fluorescent EGFR antibody via reversible BBB permeability enhancement with siRNA modulation of tight junction protein in an orthotopic xenograft animal model of high-grade glioma with EGFR overexpression. Furthermore, resected pHGGs were examined for EGFR expression in order to stratify patient subpopulation most likely to benefit from intraoperative molecular imaging strategy that targets EGFR.
Methods: An orthotopic high-grade glioma xenograft model was established in 6-15 week old mice (n=3) by intracranial injection of 10^6 EGFR-overexpressing high-grade glioma cells (D270, 10ul) 3mm below the surface of brain. Subsequently, the exposed brain was covered with a glass plate secured to the skull with cyanoacrylate glue. siRNA was selected from those targeting conserved regions of the mouse claudin-5 cDNA sequence. 20μg of claudin-5 siRNA was injected intravenously via the tail vein in an in vivo-Jet-PEI solution (Polyplus Transfection) at a rate of 0.2 ml/sec 10 days post tumor implant. 0.1mL tetramethylrhodamine (250kDa) and various sized FITC-dextran (4.4-150kDa) solutions were injected intravenously to visualize blood vessels and assess extravasation distance through cranial window via 2-photo microscopy. Enhanced permeability of BBB was characterized by increase in KTrans on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in the tumor region. Mean fluorescence intensity at 800nm was measured through cranial window with an in vivo NIR imager (Pearl Impulse, LI-COR Biosciences) 0-72 hours following tail vein injection of 200ug panitumumab-IRDye800 (pan800). Immunohistochemical analysis of EGFR expression was performed on surgically resected de novo primary pHGG tumors, from seven GBM and three anaplastic ependymoma patients respectively.
Results: The siRNA has shown a reversible 80% suppression of claudin-5 at 48-hrs post-injection that returned to normal levels at 72 hours. More than three-fold increase in penetration distance of 70kDa enhancing agent was observed in extravascular space and a 74% increase in intratumoral permeability was observed on DCE-MRI. Intratumoral delivery of fluorescent EGFR antibody (panitumumab-IRDye800) occurred at 6 hours and peaked at 48 hours post systemic injection following BBB opening. Positive EGFR expression was found in 70% of all surgically removed high-grade pediatric brain tumor samples. The median age of patients with positive EGFR expression was 15 (IQR = 12.75 to 16.50), significantly higher (P = 0.018) than that of EGFR negative patients (median = 0.75, IQR = 0.47 to 5.38).
Conclusions: We provided proof-of-concept evidence that the enabling technology of transient BBB modulation and fluorescence-guided imaging with EGFR targeting antibody has great potential for clinical translation to improve surgery outcome by providing tumor-specific precision resection to a significant subpopulation of young patients with pHGGs
Introduction: Glioblastoma (GBM) is the most common and devastating primary brain tumor. The recurrence rate remains high with a median survival of 15 months. GBM’s infiltrative nature results in ill-defined margins that makes maximal tumor resection with minimal morbidity a challenge. Epidermal growth factor receptor (EGFR) is the most frequently amplified gene in GBM (35-45% of tumors) and is associated with overexpression in about 40-98% of cases, a characteristic of more aggressive phenotypes. We hypothesize that fluorescence labeled anti-EGFR monoclonal antibodies (mAb), panitumumab-IRDye800 (pan800) and cetuximab-IRDye800 (cet800), could be leveraged to enhance tumor contrast during surgical resection and improve patient outcome.
Methods: 50mg fluorescently labeled corresponding study drugs, pan800 and cet800 respectively, were administered 1-2 days in glioblastoma patients with contrast enhancing (CE) tumors prior to surgery following 100 mg loading dose of unlabeled cetuximab or panitumumab. Near-infrared fluorescence imaging of tumor and histologically negative peri-tumoral tissue was performed intraoperatively and ex vivo. Fluorescence was measured as mean fluorescence intensity (MFI), and tumor-to-background ratios (TBRs) were calculated by comparing MFIs of tumor and histologically uninvolved tissue.
Results: Despite heterogeneous drug uptake across all resected brain tissues, mean fluorescence intensity (MFI) correlated strongly (R^2=0.97) with tumor volume among histologically confirmed tumor tissues. The smallest detectable tumor size in a closed-field setting was 4.2 x 2.7 mm^2 (8.2 mg) for pan800 and 8.5 x 6.6 mm^2 (70mg) for cet800. Tumor tissues from pan800 infusion had significantly higher mean TBR (8.1 ± 4.6) than cet800 infused ones in intraoperative imaging (3.3 ± 2.7; P = 0.004). NIR fluorescence from both test drugs provided high contrast to identify as few as a cluster of (5 ± 1) tumor cells in macroscopic imaging of whole sections of paraffin embedded tissues. Sensitivity and specificity of MFI for viable tumor detection was calculated and fluorescence was found to be highly sensitive (64.4% for pan800, 73.0% for cet800) and specific (98.0% for pan800, 66.3% for cet800) for viable tumor tissue while normal peri-tumoral tissue showed minimal fluorescence. No related grade-2 adverse events were observed 30 days beyond the infusion of either study drugs.
Conclusion: EGFR antibody based imaging for contrast-enhanced glioblastomas proved safe in human patients and specific intratumoral delivery of NIR fluorescence provided high optical contrast and resolution for intraoperative image-guided resection. Fully humanized panitumumab-IRDye800 demonstrated superior detection sensitivity and tumor specificity over the chimeric cetuximab-IRDye800.
Low response rates in solid tumors including head and neck cancers (HNCs) have been attributed to failure of the drug to reach its intended target. However, investigation of drug delivery has been limited due to difficulties in measuring concentrations in the tumor and the ability to localizing drugs in human tissues. Factors determining intratumoral antibody distribution in primary tumor and metastatic lymph nodes have not been well-studied in human patients. To address this challenge, we propose to leverage fluorescently labeled antibodies to investigate antibody delivery into HNCs.
To this end, we have conducted a first-in-human clinical trial to assess the delivery of panitumumab-IRDye800 in HNCs. Twenty-two patients enrolled in this study received intravenous administration of panitumumab-IRDye800 at multiple subtherapeutic doses: (1) 0.06mg/kg, (2) 0.5 mg/kg, (3) 1 mg/kg, (4) 50 mg flat dose, (5) 25 mg flat dose. To quantify the antibody delivery, fresh tumor samples were procured and the amount of antibody in the tumor was quantified as ng/mg of tissue, which was then correlated with tumor characteristics. Immunohistochemistry of multiple protein markers, including EGFR, ERG, cytokeratin, Ki67, alpha-smooth muscle actin, etc., have been implemented in serial sections of primary tumors and metastatic lymph nodes. A quantitative image analysis pipeline was developed to analyze these IHC images and score the staining on both global and local scale. A predictive model was built to identify the most important predictors for antibody penetration from pharmacological factors, tumor pathophysiological factors, and tumor microenvironmental factors.
Plasmonic gold nanoshell (GNS) probe penetrates into tumors for deep imaging, enables superior photoacoustic contrast. Glypican-3 (GPC3) specific peptide (Kd = 71 nM) conjugated gold nanoshell (λabs=770nm) was used to detect HCC xenograft tumors in mice with photoacoustic imaging. This targeting probe demonstrated tumor uptake after 1 hr and cleared in 12 hrs. Images at a mean (±SD) depth of 9.7±1.4 mm from 0 to 2.1 cm beneath the skin revealed increased PA signal from tumors. Highest tumor uptake and tumor to normal tissue ratio occurred at 2 hrs post injection (T/B = 4.45±0.22, n = 8). Molecular targeting GNS showed potential as a simple, effective and rapid technique for noninvasive in vivo monitoring HCC tumor growth and GPC3 expression.
We demonstrate a dual axes confocal architecture, which can be used to collect horizontal(XY-plane) or vertical cross-sectional(XZ-plane) images for tissue. This scanner head is 5.5mm in outer diameter(OD), and integrates a 3D MEMS scanner with a compact chip size of 3.2×2.9mm2. To realize the miniaturization, there are some obstacles of the small size of 3D MEMS scanner, MEMS wire bundle, the air pressure effect for MEMS motion, the processing of parabolic mirror, and optical alignment to come over. In our probe, separation mechanical structure for optical alignment was adopted and a step shape MEMS holder was designed to deal with the difficult of MEMS wire bundle. Peptides have been demonstrated tremendous potential for in vivo use to detect colonic dysplasia. This class of in vivo molecular probe can be labeled with near-infrared (NIR) dyes for visualizing the full depth of the epithelium in small animals. To confirm our probe performance, we take use of USAF 1951 resolution target to test its lateral and axial resolution. It has lateral and axial resolution of 2.49um and 4.98um, respectively. When we collect the fluorescence imaging of colon, it shows that the field of view are 1000um×1000um (horizontal) and 1000um×430um (vertical). The horizontal and vertical cross-sectional images of fresh mouse colonic mucosa demonstrate imaging performance with this miniature instrument.
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