Near-infrared fluorescent labeled CGRRAGGSC peptides for optical imaging of IL-11R alpha in athymic mice bearing tumor xenografts

The interleukin-11 (IL-11) and the IL-11 receptor alpha-subunit (IL-11R alpha) have been demonstrated to regulate the invasion and proliferation of tumor cells. Our study intends to evaluate a noninvasive imaging of IL-11R alpha expression in breast tumors using near-infrared (NIR) fluorescent dye Cy7-labeled IL-11 mimic peptide CGRRAGGSC. This work evaluated the IL-11R alpha expression of breast tumor cells and the binding status of this peptide to IL-11R alpha in vitro and in vivo by using Western blotting, immunofluorescence staining and near-infrared fluorescence imaging. Our biochemical study showed that IL-11R alpha was overexpressed in breast tumor cells (MCF-7). The cell-binding assay demonstrated specific binding of peptide CGRRAGGSC to MCF-7 cells in vitro. In vivo imaging results showed that NIR fluorescent signals of Cy7-CGRRAGGSC were selectively accumulated in tumor and metabolic organs. While in the blocking experiment, free CGRRAGGSC obviously blocked the concentration of the Cy7-CGRRAGGSC in the tumors. These results suggested that IL-11R alpha may be used as a potential target for noninvasive imaging in IL-11R alpha overexpressed tumors. Furthermore, the imaging agent of near-infrared fluorescent dye Cy7-labeled CGRRAGGSC is suitable for IL-11R alpha expression imaging study in vivo.