Highly specific targeting and imaging of live cancer cells by using a peptide probe developed from rationally designed peptides.

Specific detection and in vivo tracing of cancer biomarkers are important for cancer analysis. In this work, a simple and effective strategy for developing peptide probes was established. Peptides were rationally designed by using an antisense peptide approach directed towards an extracellular fragment (EL2) of a novel tumor-related protein LAPTM4B. Positional-scanning and stepwise affinity screening was employed to obtain an optimal peptide AP2H (IHGHHIISVG). The dissociation constant between the two small peptides, AP2H and the target EL2, was 5.51 μM under physiological conditions. Fluorescence imaging assays indicated that AP2H can recognize live hepatoma cells by targeting the LAPTM4B protein on the cell surface with high specificity, low cytotoxicity and desirable cell penetrability. Compared to negative control cells, AP2H could differentiate cells with different expression levels of LAPTM4B. The screened peptide probe for molecular signatures of cancer cells, based on targeting the LAPTM4B protein, has potential applications in cancer diagnosis and targetable drug delivery.