NRP1 and neoplasm: It is reported that the tLyp-1 peptide, a tumor cell homing and penetrating peptide, was able to mediate tissue penetration through the NRP-1-dependent internalization pathway due to the structure of both a tumor-homing motif and a cryptic CendR motif ((R/K)XX(R/K)), which is responsible for cell internalization and tissue penetration.