Various human solid
tumors highly express
IL-4 receptors which amplify the expression of some of
anti-apoptotic proteins, preventing
drug-induced
cancer cell death. Thus,
IL-4 receptor targeted
drug delivery can possibly increase the therapeutic efficacy in
cancer treatment. Macromolecular carriers with multivalent targeting moieties offered great advantages in
cancer therapy as they not only increase the plasma half-life of the
drug but also allow delivery of therapeutic drugs to the
cancer cells with higher specificity, minimizing the deleterious effects of the
drug on normal cells. In this study we designed a library of
elastin like polypeptide (ELP)
polymers containing
tumor targeting
AP1 peptide using recursive directional
ligation method. AP1 was previously discovered as an
atherosclerotic plaque and
breast tumor tissue homing
peptide using phage display screening method, and it can selectively bind to the
interleukin 4 receptor (IL-4R). The fluorescently labeled [AP1-V12]6, an ELP
polymer containing six AP1 enhanced
tumor-specific targeting ability and uptake efficiency in H226 and MDA-MB-231
cancer cell lines in vitro. Surface plasmon resonance analysis showed that multivalent presentation of the targeting
ligand in the ELP
polymer increased the binding affinity towards
IL-4 receptor compared to free
peptide. The binding of [AP1-V12]6 to
cancer cells was remarkably reduced when
IL-4 receptors were blocked by antibody against
IL-4 receptor further confirmed its binding. Importantly, the Cy5.5-labeled [AP1-V12]6 demonstrated excellent homing and longer retention in
tumor tissues in MDA-MB-231 xenograft mouse model. Immunohistological studies of
tumor tissues further validated the targeting efficiency of [AP1-V12]6 to
tumor tissue. These results indicate that designed [AP1-V12]6 can serve as a novel carrier for selective delivery of therapeutic drugs to
tumors.