Enhanced Visualisation of Colorectal Tumours via Topical Application of EMI-137 in a Methylcellulose-Based Formulation: An ex vivo Feasibility Study

TL;DR

A new viscous formulation of EMI-137 improves fluorescence imaging of colorectal tumors by enhancing tracer contact with tissue.

Contribution

A novel methylcellulose-based formulation enhances EMI-137's fluorescence for ex vivo tumor visualization.

Findings

Methylcellulose formulation increased EMI-137 fluorescence intensity compared to PBS.

EMI-137 in methylcellulose effectively visualized colon tumors with high tumor-to-background ratio.

Histopathological analysis confirmed c-Met expression in visualized tumors.

Abstract

Fluorescence-guided molecular imaging may improve colorectal cancer (CRC) patient outcomes by enabling early detection and better surgical treatment, relying on developing targeted fluorescent tracers to highlight tumours. This study investigates visualising primary colon tumours by topically applying EMI-137, a targeted fluorescent tracer designed to bind to c-Met receptor. We introduce a novel viscous formulation to enhance the tracer's performance, aiming for a clear, robust fluorescent signal by improving contact with mucosal surface of ex vivo colon specimens.

We evaluated fluorescence properties of EMI-137 in phosphate-buffered saline (PBS) and in methylcellulose (m-cellulose) and determined emission spectrum of the tracer in both formulations. Flow cytometry was used to determine EMI-137's specificity for c-Met receptor and its optimal concentration. Live-cell imaging visually confirmed EMI-137's fluorescence signal for the c-Met receptor, highlighting its distinctive characteristics across various solvents. In a prospective cohort study, freshly excised colon cancer specimens were incubated with EMI-137 in PBS or m-cellulose. Specimens underwent a meticulous washing process. Near-infrared fluorescence imaging was performed and compared with histopathological analysis to validate detection accuracy.

Fluorospectrometry showed that m-cellulose enhanced EMI-137's fluorescence intensity compared to PBS. Flow cytometry showed dose-dependent binding of EMI-137 in HT-29 cells, with an optimum at 500 nM. Microscopy confirmed targeting of c-Met receptors. Topical EMI-137 dissolved in m-cellulose visualised colon tumours effectively, resulting in a high tumour-to-background ratio. Histopathological analysis confirmed c-Met expression in these colon tumours.

EMI-137 in a novel viscous vehicle effectively imaged c-Met expressing colon tumors, potentially facilitating fluorescent-guided tumor imaging.

The online version contains supplementary material available at 10.1007/s11307-025-02042-z.

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