NRP1 and neoplasm: Based on this, a dual receptor targeted CPP with a sequence of RRRRRRRRRdGR-R9dGR was designed, which could bind to both integrin αvβ3 and neuropilin-1 (NRP-1) receptors that were high-expressed on breast cancer cells [8–10], and also penetrate tumor tissue by electrostatic interaction to realize the synergetic penetrable effect via the above three pathways.