For example, exosomes engineered to express the transmembrane domain of the PDGF receptor fused to the GE11 peptide were shown to successfully deliver the let-7a microRNA to EGFR-expressing breast cancer cells in vitro and EGFR-expressing xenograft breast cancer tissue in vivo, thus demonstrating the potential of exosomes to be used therapeutically to specifically target cancer cells with nucleic acid drug targets [143]. This evidence concerns the gene EGFR and cancer.