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
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.
MEMS based microendoscopes have become important imaging tools for early cancer diagnosis and precise tumor resection. Due to various technical challenges, few microendoscopes have been translated to clinics or applied to human patients. Through synergistic collaborations, we have developed novel MEMS scanner enabled microendoscopic multispectral (640nm to 780nm) three- dimensional dual-axis confocal fluorescent imaging system for translational applications, including early cancer detection and staging on colorectal cancer, molecular imaging guided surgical navigation on head and neck cancer. Based on dual-axis confocal microscopic architecture, we have miniaturized the imaging system with compact form-factor by integrating micro-optics and a patterned gold coated MEMS scanners, which have been custom-made and mass-produced in the nanofabrication foundry. The metal coating of the scanning mirror provide over 80% high reflectivity over near infra-red range. Both axes of the MEMS scanner could perform large tilting angle (> 6 degree mechanical scan angle) at DC and resonant mode. By advanced computational imaging approach, we have achieved real-time cross-sectional imaging in either raster or lissajous pattern scanning with fast frame rate (> 10 Hz) with large field-of-view (> 600 microns). Advanced real-time mosaicing algorithm has been developed to achieve broader view in millimeter scale. By utilizing molecular contrast probes conjugated with fluorescence dye, we have successfully demonstrated multi-spectral ex-vivo and in-vivo imaging on small animal tumor models and human tissue specimens, aimed for both early cancer detection and molecular imaging guided surgical navigation.
Wide-field fluorescent imaging for fluorescence molecular guidance has become a promising technique for use in imaging guided surgical navigation, but quick and intuitive microscopic inspection of fluorescent hot spots is still needed to confirm local disease states of tissues. To address this unmet need, we have developed a clinically translatable dual-modality handheld surgical microscope that incorporates both, wide-field (mesoscopic) fluorescence imaging and high-resolution (microscopic) horizontal optical-sectioning. This is accomplished by integrating a commercially available wide-field fiberscope, modified for two-color (660nm and 785nm) fluorescent detection, into a compact package (5.5 mm dia.) which also contains a dual-axis confocal (DAC) microscope. DAC microscopy is a high-sensitivity, high-resolution fluorescent imaging technology that benefits from the specificity of molecular probes, and enables interrogation of deeper regions of tissue by performing optical-sectioning of tissue. The DAC microscope has been designed with custom catadioptric micro-lenses to provide broadband multispectral capability for fluorescence imaging of multiple fluorophores over a broad spectral range (VIS to NIR), and also uses a novel MEMS-based scanning system for horizontal sectioning, and thus enables access to deeper regions of tissue at resolutions comparable to histological analysis. Large field-of-view (mm scale) is further provided by image mosaicing. The instrument thus provides simultaneous mesoscopic and microscopic fluorescence imaging over a broad spectral range for intuitively performing fast in-vivo search and microscopic confirmation of optical molecular markers in tissue, which is a capability that will become increasingly important for precise tumor resection in oncology as more optical molecular markers become approved for human use.
Over the past two decades, synergistic innovations in imaging technology have resulted in a revolution in which a range of biomedical applications are now benefiting from fluorescence imaging. Fluorescence imaging of lymph nodes after systemic cetuximab-IRDye800CW administration demonstrated high sensitivity and was capable of identifying additional positive nodes on deep sectioning.
BACKGROUND: Presence of lymph node (LN) metastasis is considered the most important prognostic factor in patients with head and neck cancer, yet intraoperative identification of metastatic LNs is considered challenging. We propose the near-infrared fluorescently labeled epidermal growth factor receptor (EGFR) antibody panitumumab-IRDye800 for intraoperative metastatic LN identification.
METHODS: Patients were injected 2-5 days before surgery with panitumumab-IRDye800 (0.5 or 1.0 mg/kg). On the day of surgery, (excised) LN samples were evaluated on high sensitivity fluorescence imaging systems (SurgVision (SurgOptix), PINPOINT (Novadaq), and Pearl imager and Odyssey CLx (LI-COR Biosciences). Location and intensity of the fluorescence signal was correlated to the location of tumor as defined on the hematoxylin and eosin staining by the pathologist, and the EGFR expression pattern. We calculated the sensitivity, specificity, positive and negative predictive values of panitumumab-IRdye800 for metastatic LN identification.
RESULTS: We thus far included 9/27 patients in our ongoing phase I trial. 244 LNs were removed intraoperatively of which 8 were tumor-positive. Fluorescence imaging of panitumumab-IRdye800 revealed 236 true-negative nodes (not fluorescent, not tumor-positive), 8 true-positive nodes (fluorescent, tumor-positive), 0 false-positive nodes (fluorescent, not tumor-positive) and 0 false-negative nodes (not fluorescent, tumor-positive) resulting in a sensitivity of 100%, a specificity of 100%, and a positive and negative predictive value of 100% and 100%, respectively.
CONCLUSION: Preliminary results from our ongoing study suggest panitumumab-IRDye800 can identify metastatic LNs. Upon trial progression, if findings remain constant, it can open a whole new era for intraoperative metastatic LN identification.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.