Confocal laser endomicroscopy enables in vivo VEGF imaging

Molecular imaging of vascular endothelial growth factor (VEGF) might soon be feasible in patients with gastrointestinal cancer, report Foersch and colleagues.

Confocal laser endomicroscopy (CLE) is used to diagnose cancer in real-time, in vivo histological examinations of the gastrointestinal tract; however, the current technique involves tissue staining with nonspecific fluorescent dyes, such as fluorescein. Foersch et al. show that CLE can be used to visualize the expression and subcellular localization of tumor markers, such as VEGF, by using fluorescence-labeled antibodies. VEGF is essential for angiogenesis in both healthy and malignant tissue, with high levels observed in the latter, and is a therapeutic target in gastrointestinal cancers.

After application of fluorescence-labeled anti-VEGF antibodies, the researchers used a hand-held CLE probe to scan tumors in vivo in two rodent models of gastrointestinal cancer (Apc^Min/+ mice and a xenograft model) as well as tissue samples from patients with colorectal cancer. A high proportion of Apc^Min/+ and xenograft tumors displayed a strong, cytoplasmic VEGF signal. Healthy tissue, by contrast, exhibited little or no VEGF expression. The in vivo imaging results correlated well with those of ex vivo histopathological examination.

“Up to now, molecular imaging has been performed only on biopsy samples from humans,” notes Martin Goetz, corresponding author of the paper. “The next step is to use the technique in patients in vivo. CLE could also potentially be used to predict responses to targeted therapy for colorectal cancer,” he says.