Abstract 4101: Early detection of colonic neoplasia using fluorescence microendoscopy
Authors: Pham Wellington , Kumagai Hironori , Hiwatari Ken-Ichiro , Koike Seiji , Tobita Etsuo , Kitamura Tokio , Mohri Kohta , Sakuma Shinji 
Published: May 2015

Purpose: The objective of this research is to integrate nanotechnology with molecular imaging for early detection of colorectal cancer (CRC). CRC undergoes a protracted asymptomatic stage before it reaches the advance stage. Therefore, detection in the early onset through regular screening will improve therapeutic outcomes and save lives. In that regard, colonoscopy is considered the golden standard for early detection. However, its effectiveness for early detection of tumor growth is mitigated by its incapacity to disclose molecular level changes. Recent studies have reported the miss rate for this tumor size-dependent technique is as high as 20% for polyps.

One molecule associated with the development and progress of CRC is the Thomsen-Friedenreich (TF) antigen (Ag). High expression of TF disaccharide in CRC and its absence from normal tissue represents a unique association in CRC that exhibits the qualities of a prognostic biomarker.

Method: We developed a fluorescence (FL) nanobeacon, which can bind specifically to TF-associated CRC due the presence of multiple identical copies of peanut agglutinin (PNA) molecules derivatized on the surface of the nanobeacon. The physical property of the FL nanobeacon such as size, shape, surface topography, elemental composition and polymer distribution was evaluated using dynamic light scattering, scanning electron microscopy, X-ray photoelectron spectroscopy and permeation chromatography, respectively.

We assessed the sensitivity and specificity of the nanobeacon on human specimens using FL microscopy, Western blot and quantitative PCR. TF Imaging data was validated by depletion of TF expression employing a glycanase assay. In addition, we developed an orthotopic rat model of CRC using Athymic nude rats to assess the specificity of the nanobeacon using white light colonoscopy and FL microendoscopy. Furthermore, the biodistribution of the nanobeacon was assessed using an orthotopic mouse model.

Results: The overall size of the nanobeacon is approximately 350 nm. It contains 0.05% coumarin 6 dye in the polystyrene center core. There are approximately 200-300 PNA molecules, which serve as molecular recognition moieties for TF Ag. The nanobeacon specifically reported CRC by recognizing the tumor-specific Ag through surface-immobilized PNA. Removal of TF from human colorectal cancer cells and tissues resulted in a significant loss of FL signal, which suggests the specificity of the probe.

In vivo imaging data demonstrated that the FL colonoscopy using the nanobeacon can detect CRC much earlier than conventional colonoscopy. Finally, biodistribution study showed that the nanobeacon is not absorbed by colonic mucosa upon being sprayed topically, thus there is no register toxicity associated with this probe.

Conclusion: We demonstrated the potential use of a novel nanobeacon for early detection of CRC. Data obtained in this work suggests that TF Ag can be used as a potential biomarker for imaging CRC.

Citation Format: Wellington Pham, Hironori Kumagai, Ken-Ichiro Hiwatari, Seiji Koike, Etsuo Tobita, Tokio Kitamura, Kohta Mohri, Shinji Sakuma. Early detection of colonic neoplasia using fluorescence microendoscopy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4101. doi:10.1158/1538-7445.AM2014-4101