CEACAM5-targeted near-infrared fluorescence imaging: A novel strategy for precise intraoperative navigation in colorectal cancer

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This article addresses the challenges of intraoperative tumor identification in colorectal cancer surgery, systematically elucidating the principles and advantages of near-infrared fluorescence imaging technology as it evolves from NIR-I to NIR-II. It analyzes the molecular basis of CEACAM5 as a specific imaging target for colorectal cancer and its significant expression differences between tumor and normal tissues, explores the clinical translation potential of this targeted imaging strategy in achieving precise tumor resection, and introduces the application of fluorescently labeled recombinant proteins in target validation and imaging research.

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CEACAM5-Targeted Near-Infrared Fluorescence Imaging: A Novel Strategy for Precision Navigation in Colorectal Cancer Surgery

Summary: This article addresses the intraoperative tumor identification challenges in colorectal cancer surgical treatment, systematically elaborating on the principle advantages of near-infrared fluorescence imaging technology evolving from NIR-I to NIR-II. It analyzes the molecular basis of CEACAM5 as a specific imaging target for colorectal cancer and its significant expression differences between tumor and normal tissues, explores the clinical translation potential of this targeted imaging strategy in achieving precise tumor resection, and introduces the application of fluorescently labeled recombinant proteins in target validation and imaging research.

1. Current Status of Colorectal Cancer Treatment and Intraoperative Navigation Challenges

Colorectal cancer is one of the most prevalent and deadly malignancies worldwide. Currently, for most patients with localized colorectal cancer, surgical resection of all tumor tissues with clear margins remains the primary and most effective curative treatment. However, achieving complete tumor resection (R0 resection) in clinical practice faces numerous challenges. On one hand, due to the infiltrative growth of tumors and inflammatory adhesions with surrounding tissues, surgeons often struggle to accurately define the true tumor boundaries based solely on visual and tactile feedback during surgery. On the other hand, some patients present with multifocal lesions or peritoneal micrometastases, which are easily overlooked during routine surgical exploration. These factors collectively contribute to high rates of incomplete tumor resection, positive surgical margins, and postoperative peritoneal metastases, significantly impacting patients' long-term survival outcomes. Therefore, there is an urgent clinical need for the development of intraoperative navigation technologies capable of real-time, precise identification of tumor-normal tissue boundaries.

2. Principles and Evolution of Near-Infrared Fluorescence Imaging Technology

Near-infrared fluorescence imaging is a real-time intraoperative navigation technique that combines targeted fluorescent probes with highly sensitive imaging systems. Its fundamental principle involves intravenous administration of fluorescently labeled probes that specifically bind to antigens highly expressed on tumor cell surfaces, leading to selective accumulation in tumor tissues. During surgery, near-infrared fluorescence imaging devices are used to visualize the probes in real time, assisting surgeons in accurately identifying and completely resecting tumor tissues.

In the development of near-infrared fluorescence imaging technology, two main wavelength bands have emerged based on emission characteristics: NIR-I and NIR-II. The NIR-I band (700-900 nm) was the first to be clinically applied but revealed significant limitations in practice: strong photon absorption and scattering by biological tissues in this band, coupled with high tissue autofluorescence background, severely restricted imaging depth and signal-to-noise ratio. In contrast, the NIR-II band (1000-1700 nm) overcomes these limitations with its superior tissue penetration, effectively addressing issues of tissue absorption, photon scattering, and autofluorescence interference. NIR-II imaging achieves higher spatial resolution and deeper tissue penetration, clearly delineating deep tumor boundaries and their anatomical relationships with surrounding critical vessels and nerves. This provides surgeons with more precise intraoperative navigation information, potentially significantly improving R0 resection rates.

3. CEACAM5: An Ideal Target for Specific Imaging in Colorectal Cancer

An ideal tumor-targeted imaging target must exhibit three core characteristics: high expression in tumor tissues, low expression in normal tissues, and accessibility on the cell membrane surface. Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5), also known as CD66e or carcinoembryonic antigen (CEA), perfectly meets these criteria. At the molecular expression level, CEACAM5 is overexpressed in approximately 90% of colorectal cancer tissues, while its expression in normal tissues is on average 60-fold lower than in tumors. This nearly two-order-of-magnitude difference provides an exceptionally favorable tumor-to-normal tissue signal contrast for targeted imaging. Additionally, CEACAM5 is anchored to the cell membrane surface via glycosylphosphatidylinositol (GPI), facilitating probe recognition and binding without significant ligand internalization or degradation issues, thereby enabling stable accumulation and sustained visualization of probes at tumor sites. These features collectively establish CEACAM5 as one of the most promising targets for near-infrared fluorescence imaging in colorectal cancer.

4. Preclinical Validation of CEACAM5-Targeted NIR-II Imaging in Colorectal Cancer Surgery

Leveraging the excellent targeting properties of CEACAM5, researchers have developed various CEACAM5-targeted near-infrared fluorescent probes and validated their feasibility for intraoperative navigation in preclinical models. For instance, researchers conjugated anti-CEACAM5 nanobodies with the NIR-II fluorescent dye IRDye 800CW to create the targeted probe 2D5-IR800. In mouse models bearing human colorectal cancer HT-29 and LS180 xenografts, this probe demonstrated significant tumor-specific accumulation as early as 6 hours post-injection, achieving a tumor-to-muscle signal ratio (T/M) as high as 6.4±1.1, with tumor-to-major organ signal contrasts all exceeding 4. This indicates the probe's capability to clearly outline tumor boundaries and accurately locate multifocal microtumors. Similarly, in patient-derived xenograft models of colorectal cancer, 2D5-IR800 achieved high-contrast imaging of primary tumors and their peritoneal disseminated lesions. These results provide robust experimental support for the clinical translation of CEACAM5-targeted NIR-II fluorescence imaging to guide precise colorectal cancer resection.

5. Conclusion

Colorectal cancer surgery has long been constrained by the inability to visualize tumor boundaries intraoperatively, making it difficult to further improve R0 resection rates. With its 90% positivity rate in colorectal cancer and nearly 60-fold expression difference between tumor and normal tissues, CEACAM5 has emerged as one of the most promising targets for intraoperative near-infrared fluorescence imaging. The evolution of NIR-II fluorescence imaging technology has endowed this targeting strategy with superior tissue penetration and spatial resolution, potentially enabling precise intraoperative tumor boundary localization and detection of micrometastases. U-ACT offers FITC-Labeled CEACAM-5/CD66e Fc Chimera Protein, Human, a product that, with its precise molecular design, native conformation ensured by human expression systems, and the high brightness and stability of FITC dyes, provides a reliable detection tool for CEACAM5-related target validation, probe screening, and flow cytometry applications.

This article is reviewed and published by the technical expert team of UA

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