IFITM1-targeted NIR-II fluorescence imaging enables visualisation of colorectal cancer and metastatic lymph nodes

To improve the visualisation of colorectal cancer (CRC) and its metastatic lymph nodes (LNs), we developed a second near-infrared window (NIR-II; 1000–1700 nm) fluorescent probe using a monoclonal antibody against interferon-induced transmembrane protein 1 (IFITM1). The NIR-II offers advantages for fluorescence-guided resection of CRC and metastatic LNs. IFITM1 expression in CRC was analysed using The Cancer Genome Atlas (TCGA) database. Clinical tumour specimens were assessed by immunohistochemistry to confirm IFITM1 expression in patients with CRC. An IFITM1–IRDye800CW (IFITM1-800CW) NIR-II fluorescent probe was constructed. It’s in vivo performance was evaluated in subcutaneous CRC xenografts, orthotopic implantation models, and orthotopic LN metastasis models. Surgically resected human CRC specimens were also incubated with the probe to evaluate its clinical utility. TCGA and tissue analyses showed significantly higher IFITM1 expression in CRC compared with normal tissues (P < 0·001). After intravenous injection of IFITM1-800CW, tumour fluorescence signals appeared at 6 h and peaked within 24 h across all mouse models, enabling robust CRC and LN visualisation. This approach permitted in situ detection of tumours and metastatic LNs as small as 1 mm. In ex vivo human samples, IFITM1-800CW produced significantly higher fluorescence intensity in CRC tissues than in normal or adjacent tissues (P < 0·0001), and allowed identification of tumour margins. IFITM1 is differentially expressed in CRC and represents a promising imaging target. IFITM1-800CW enables sensitive detection of CRC and metastatic LNs, enabling supporting complete tumour resection under NIR-II fluorescence guidance.