Topical application of Chlorin e6-PVP (Ce6-PVP) for improved endoscopic detection of neoplastic lesions in a murine colitis-associated cancer model

Abstract

Screening colonoscopy is crucial in reducing the mortality of colorectal cancer. However, detecting adenomas against the backdrop of an inflamed mucosa (e.g. in ulcerative colitis) remains exceedingly difficult. Therefore, we aimed to improve neoplastic lesion detection by employing a fluorescencebased endoscopic approach. We used the well-established murine AOM/DSS model to induce inflammation-driven carcinogenesis in the colon. In our diagnostic approach, we evaluated Chlorin e6 polyvinylpyrrolidone (Ce6-PVP)-based fluorescence endoscopy in comparison to standard whitelight endoscopy. A specialized pathologist then analyzed the histology of the detected lesions. Complementary in vitro studies were performed using human cell lines and a murine organoid system. Ce6-PVP-based fluorescence endoscopy had an improved detection rate of 100% (8/8) in detecting high-grade dysplasias and carcinomas over white-light detection alone with 75% (6/8). Trade-off for this superior detection rate was an increased rate of false positive lesions with an increase in the false discovery rate from 45% for white-light endoscopy to 81% for fluorescence endoscopy. We demonstrate in a proof-of-concept study that Ce6-PVP-based fluorescence endoscopy is a highly sensitive red flag technology to identify biopsy-worthy lesions in the colon. Achieving high adenoma detection rates during screening colonoscopy remains a formidable challenge as small or flat lesions are particularly difficult to detect 1-3. Among the technologies used to improve white-light endoscopy and increase detection rates, fluorescence-enhanced endoscopy has proven exceptionally promising. Specifically targeted fluorophores have been applied both systemically (intravenously) and topically (e.g. via enema) 4, 5 to detect dysplastic lesions in the colon with overall encouraging results. However, how to best identify relevant sites for biopsy in inflamed colonic mucosa, e.g. in inflammatory bowel diseases such as ulcerative colitis, remains an open question. It is generally accepted that the disease-specific risk for developing a colorectal carcinoma begins roughly 7 years after diagnosis of UC and a recent meta-analysis has supported that the risk for CRC is positively correlated with inflammatory activity 6. However, discerning non-neoplastic inflammatory alterations from neoplastic lesions during colonoscopy gets increasingly difficult with increasing inflammatory activity. Conflicting data on the best approach for surveillance strategies necessitate further research into emerging technologies such as fluorescence endoscopy.

In vivo multi spectral colonoscopy in mice

“…Hence, there are no artefacts which occur as it happens from fibre bundles. This system was used with a spectral filter as a fluorescence endoscope system for the investigation of the topical application of Chlorin e6-PVP for improved endoscopic detection of neoplastic lesions 18 . The set-up is shown in Fig.…”

“…1 .

Figure 1 Schematics of the set-up (modified as described in our previous study 18 ). The top schematic shows the overall set-up and the bottom schematic shows the optical set-up which images the light from the endoscope.

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“…The modified endoscope was already described in our previous publication 18 : “The custom optics unit incorporates two achromatic lenses with an apochromatic objective in between. The signal initially travels from the endoscopy telescope unit via an adaptor to the first lens with a focal length of 35 mm.…”

Single-Cell RNA Sequencing Reveals Immuno-Oncology Characteristics of Tumor-Infiltrating T Lymphocytes in Photodynamic Therapy-Treated Colorectal Cancer Mouse Model

“…Photodynamic therapy (PDT) is a minimally invasive therapeutic approach that utilizes photosensitizing agents and light activation, resulting in the generation of reactive oxygen species and subsequent tumor destruction [ 3 ]. Chlorin e6 (Ce6), a second-generation photosensitizer, exhibits antitumor activities during photodynamic therapy [ 4 ]. Some studies have indicated that efficiently internalized Ce6 is enriched in the mitochondria and exhibits almost no cytotoxicity under dark conditions but strong photocytotoxicity resulting from reactive oxygen species (ROS) production during photodynamic therapy [ 5 ].…”