Optimization of the enhanced permeability and retention effect for near-infrared imaging of solid tumors with indocyanine green.

Surgery is the most effective method to cure patients with solid tumors. New techniques in near-infrared (NIR) cancer imaging are being used to identify surgical margins and residual tumor cells in the wound. Our goal was to determine the optimal time and dose for imaging solid tumors using Indocyanine Green. Syngeneic murine flank tumor models were used to test NIR imaging of ICG at various doses ranging from 0 to 10 mg/kg. Imaging was performed immediately after injection and up to 72 hours later. Biodistribution in the blood and murine organs were quantified by spectroscopy and fluorescence microscopy. Based on these results, a six patient dose titration study was performed. In murine flank tumors, the tumor-to-background ratio (TBR) for ICG at doses less than 5 mg/kg were less than 2 fold at all time points, and the surgeons could not subjectively identify tissue contrast. However, for doses ranging from 5 mg/kg to 10 mg/kg, the TBR ranged from 2.1 to 8.0. The tumor signal was best appreciated at 24 hours and the background was least pronounced after 24 hours. Biodistribution studies in the blood and murine organs revealed excretion through the biliary tree and gastrointestinal tract, with minimal blood fluorescence at the higher doses. A follow up pilot study confirmed that these findings were applicable to lung cancer patients, and tumor was clearly delineated from surrounding normal tissue by NIR imaging. For non-hepatic solid tumors, we found ICG was optimal when dosed at 5 mg/kg and 24 hours before surgery.

Quantification of tumor fluorescence during intraoperative optical cancer imaging.

Intraoperative optical cancer imaging is an emerging technology in which surgeons employ fluorophores to visualize tumors, identify tumor-positive margins and lymph nodes containing metastases. This study compares instrumentation to measure tumor fluorescence. Three imaging systems (Spectropen, Glomax, Flocam) measured and quantified fluorescent signal-to-background ratios (SBR) in vitro, murine xenografts, tissue phantoms and clinically. Evaluation criteria included the detection of small changes in fluorescence, sensitivity of signal detection at increasing depths and practicality of use. In vitro, spectroscopy was superior in detecting incremental differences in fluorescence than luminescence and digital imaging (Ln[SBR] = 6.8 ± 0.6, 2.4 ± 0.3, 2.6 ± 0.1, p = 0.0001). In fluorescent tumor cells, digital imaging measured higher SBRs than luminescence (6.1 ± 0.2 vs. 4.3 ± 0.4, p = 0.001). Spectroscopy was more sensitive than luminometry and digital imaging in identifying murine tumor fluorescence (SBR = 41.7 ± 11.5, 5.1 ± 1.8, 4.1 ± 0.9, p = 0.0001), and more sensitive than digital imaging at detecting fluorescence at increasing depths (SBR = 7.0 ± 3.4 vs. 2.4 ± 0.5, p = 0.03). Lastly, digital imaging was the most practical and least time-consuming. All methods detected incremental differences in fluorescence. Spectroscopy was the most sensitive for small changes in fluorescence. Digital imaging was the most practical considering its wide field of view, background noise filtering capability, and sensitivity to increasing depth.

Intraoperative molecular imaging can identify lung adenocarcinomas during pulmonary resection.

BACKGROUND: More than 80,000 people undergo resection of a pulmonary tumor each year, and the only method to determine if the tumor is malignant is histologic analysis. We propose that a targeted molecular contrast agent could bind lung adenocarcinomas, which could be identified using real-time optical imaging at the time of surgery. METHODS: Fifty patients with a biopsy-proven lung adenocarcinoma were enrolled. Before surgery, patients were systemically administered 0.1 mg/kg of a fluorescent folate receptor alpha (FRα)-targeted molecular contrast agent by intravenous infusion. During surgery, tumors were imaged in situ and ex vivo, after the lung parenchyma was dissected to directly expose the tumor to the imaging system. RESULTS: Tumors ranged from 0.3 to 7.5 cm (mean: 2.6 cm), and 46 of 50 (92%) lung adenocarcinomas were fluorescent. No false uptake occurred, and in 2 cases, intraoperative imaging revealed tumor metastases (3 mm and 6 mm) that were not recognized preoperatively. Four adenocarcinomas were not fluorescent, and immunohistochemistry showed that these adenocarcinomas did not express FRα. Tumor fluorescence was independent of nodule size, uptake of 2-deoxy-2-((18)F)fluoro-D-glucose, histology, and tumor differentiation. Molecular imaging could identify only 7 of the 50 adenocarcinomas in situ in the patient without bisection. The most important predictor of the success of molecular imaging in locating the tumor in situ was the distance of the nodule from the pleural surface. CONCLUSIONS: Intraoperative molecular imaging with a targeted contrast agent can identify lung adenocarcinomas, and this technology is currently useful in patients with subpleural tumors, irrespective of size. With further refinements, this tool may prove useful in locating adenocarcinomas that are deeper in the lung parenchyma, in lymph nodes, and at pleural and resection margins.

Macrophages: a double-edged sword in experimental autoimmune encephalomyelitis.

Multiple sclerosis (MS) is a debilitating neurological disorder of the central nervous system (CNS), characterized by activation and infiltration of leukocytes and dendritic cells into the CNS. In the initial phase of MS and its animal model, experimental autoimmune encephalomyelitis (EAE), peripheral macrophages infiltrate into the CNS, where, together with residential microglia, they participate in the induction and development of disease. During the early phase, microglia/macrophages are immediately activated to become classically activated macrophages (M1 cells), release pro-inflammatory cytokines and damage CNS tissue. During the later phase, microglia/macrophages in the inflamed CNS are less activated, present as alternatively activated macrophage phenotype (M2 cells), releasing anti-inflammatory cytokines, accompanied by inflammation resolution and tissue repair. The balance between activation and polarization of M1 cells and M2 cells in the CNS is important for disease progression. Pro-inflammatory IFN-γ and IL-12 drive M1 cell polarization, while IL-4 and IL-13 drive M2 cell polarization. Given that polarized macrophages are reversible in a well-defined cytokine environment, macrophage phenotypes in the CNS can be modulated by molecular intervention. This review summarizes the detrimental and beneficial roles of microglia and macrophages in the CNS, with an emphasis on the role of M2 cells in EAE and MS patients.