Modular nanotransporters of anticancer drugs conferring cell specificity and higher efficiency

This review deals with artificial modular nanotransporters (MNT) of polypeptide nature for drug delivery into target cells and then into a specified cell compartment like the nucleus. The developed approach is based on the use of intracellular transport processes characteristic of practically all cells, including cancer cells. The first MNT module ligand carries out a double function: specific recognition of a cancer target cell and penetration into the cell via receptor-mediated endocytosis. The movement of the MNT within the cell along this path specifies the need to supply the MNT with an endosomolytic module making it possible to leave the endocytotic pathway before getting into lysosomes in order to have time for interaction with importins. For this purpose, a polypeptide fragment able to make defects in membranes only at the pH of endosomes is used as the second module. Delivery into the cell nucleus is provided by the third module containing an amino acid sequence of nuclear localization, "recognized" by importins located in the hyaloplasm. And finally, the fourth module, a carrier for joining the transported drug, is incorporated into the MNT. Depending on the type of ligand module, MNT for different target cell types have been produced. Each module retains its activity within the MNT, ligand modules bind target receptors with high affinity, while the module with the nuclear localization sequence binds importins. The endosomolytic module forms pores in lipid membranes through which MNT are able to leave acidifying cell compartments (endosomes). Modules within MNT can be replaced or transposed, which makes it possible to use them for delivery of different drugs into different target cells and their compartments. It was shown that photosensitizers and radionuclides used for cancer therapy acquire pronounced cell specificity as well as the 10-1000-fold higher efficiency resulting from their delivery into the most vulnerable compartment--the cell nucleus.