NRP1 and neoplasm: NP1 then undergoes passive cellular uptake, disassociates in the acidic pH of the tumor cell, and releases ellipticine (an anticancer agent) into the cytosol.55 Similarly, Zhang M. et al. developed an enzyme-responsive, self-assembling peptide-based NC using a core of repeating GFLG oligopeptides highly specific to cathepsin B for cytoplasmic DOX release.