Article

Optical Imaging with a Cathepsin B Activated Probe for the Enhanced Detection of Esophageal Adenocarcinoma by Dual Channel Fluorescent Upper GI Endoscopy

1. Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Massachusetts General Hospital.
Theranostics (Impact Factor: 8.02). 02/2012; 2(2):227-34. DOI: 10.7150/thno.4088
Source: PubMed

ABSTRACT

Despite significant advances in diagnosis and treatment, the prognosis of esophageal adenocarcinoma remains poor highlighting the importance of early detection. Although white light (WL) upper endoscopy can be used for screening of the esophagus, it has limited sensitivity for early stage disease. Thus, development of new imaging technology to improve the diagnostic capabilities of upper GI endoscopy for early detection of esophageal adenocarcinoma is an important unmet need. The goal of this study was to develop a method for the detection of malignant lesions in the esophagus using WL upper endoscopy combined with near infrared (NIR) imaging with a protease activatable probe (Prosense750) selective for cathepsin B (CTSB). An orthotopic murine model for distal esophageal adenocarcinoma was generated through the implantation of OE-33 and OE-19 human esophageal adenocarcinoma lines in immunocompromised mice. The mice were imaged simultaneously for WL and NIR signal using a custom-built dual channel upper GI endoscope. The presence of tumor was confirmed by histology and target to background ratios (TBR) were compared for both WL and NIR imaging. NIR imaging with ProSense750 significantly improved upon the TBRs of esophageal tumor foci, with a TBR of 3.64±0.14 and 4.50±0.11 for the OE-33 and OE-19 tumors respectively, compared to 0.88±0.04 and 0.81±0.02 TBR for WL imaging. The combination of protease probes with novel imaging devices has the potential to improve esophageal tumor detection by fluorescently highlighting neoplastic regions.

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    • "However, there are few reports of the relationship between cathepsins and esophageal epithelial permeability. There are many reports concerning cathepsins in esophageal adenocarcinoma (Andl et al. 2010; Habibollahi et al. 2012), yet the identities and cellular origins of cathepsins that are activated during inflammation after RE are not fully established, and their causative roles in diseases remain uncertain. "
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    ABSTRACT: We have designed a stable rat chronic acid reflux esophagitis (RE) model. In gastrointestinal lesions, several lysosomal cathepsins are known to participate in epithelial permeability in cell-cell connections, such as tight junctions in ulcerative colitis. However, very few studies have focused on the distribution of cathepsins in the esophageal multilayer squamous epithelium. Therefore to clarify the role of cathepsins in RE, we investigated their immunohistological localization in the esophageal epithelium under normal conditions and after RE. Of the cathepsins examined (cathepsins B, C, D, F, H, L, S, and X), granular immunoreactivity for cathepsins B, C, D and L was observed in the control esophageal epithelia; although, their distribution differed depending on the enzyme examined. In the RE model, immunoreactivity of these cathepsins was increased in esophageal epithelial cells and activated macrophages. The immunoreactivity for cathepsins F, H, S and X was barely detectable in the control esophageal epithelium. However, in the RE model, we noticed a slight increase in the expression of cathepsins H and X in the epithelial cells. Furthermore, activated macrophages of the RE model possessed intense immunoreactivity for these cathepsins, which may have been related to esophageal inflammatory mechanisms.
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    • "This is the first demonstration of a novel NIRF imaging agent specific for CB that can localize and detect ESCC xenografts. Similarly, fluorescent imaging probes in combination with near-infrared optical imaging has been applied to more sensitive detection of a series of cancers including pancreas, hypopharynx, ovary, and lung cancers [24]–[29]. Proteases activatable NIRF probes enabled detection of molecules or biologic activities of tumors in real time [30], [31]. "
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    • "The probe is also designed for prolonged circulation by attaching several polyethylene-glycol side chains to the polymer. A commercially available probe, ProSense, is preferentially hydrolyzed by cathepsin B but can also be activated through proteolysis by other cathepsins, such as cathepsin L and cathepsin S. ProSense has been shown to detect a variety of experimentally induced tumors of the colon, ovary, mammary gland, pancreas, and esophagus [12] [13] [14] [15] [16]. However, the mechanisms underlying the tumor specificity of ProSense signals are still unclear because this probe is exposed to numerous complex in vivo processes. "
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