Development of active tumor targeting systems for delivery of siRNA and drugs into breast and colorectal cancer

• Author / Creator

  Moura Paiva, Igor

• Active targeting strategies have been pursued to improve the efficacy and safety of cancer therapeutics and theranostics. The significant benefit of tumor homing ligands conjugated to small molecules versus nanoparticle delivery systems in enhancing drug delivery to the tumor is still a matter of debate in the literature. The central hypothesis of this thesis was that ligand molecules specific to cancer cell-surface biomarkers, can enhance homing and interaction of drugs as well as nano-drug delivery systems with tumors leading to an increased therapeutic index for the incorporated drug. To test this hypothesis, in the first research project of this thesis, the biodistribution of a breast cancer-specific engineered peptide (C18.4DK) conjugated to Cy5.5 (C18.4DK-Cy5.5) was evaluated in mice carrying orthotopic breast MDA-MB-231 tumors, where a preferential accumulation of conjugated Cy5.5 in the tumor was observed, especially two hours after intravenous injection, with rapid clearance from all other organs except kidneys and liver. Next, we examined the validity of P18.4 peptide conjugation on polymeric micellar nanoplatforms, based on poly(ethylene oxide)-block-poly(ε-caprolactone-grafted-polyamines) (PEO-b-PCL-g-PA), for specific siRNA delivery to tumor versus normal cells. We also investigated the capacity of GE11 modified polymeric micelles based on PEO-PCL and its derivative PEO-poly(a-benzyl carboxylate-ε-caprolactone) (PEO-PBCL) in targeting epidermal growth factor receptor (EGFR) overexpressing colorectal cancer models making the comparison with plain or mock peptide modified micelles. For this purpose, traceable micelles were generated using two strategies: by attaching the fluorophore Cy5.5 into the PCL/PBCL block for near-infrared (NIR) imaging; or by incorporating a positron emission tomography (PET) contrast agent, i.e., 64Cu, into the micellar shell-forming portion. Both imaging studies indicated that the EGFR-targeting peptide GE11 positively impacted nanoparticle accumulation into EGFR-expressing colorectal cancer (CRC) subcutaneous or orthotopic xenografts in mice. GE11 modification also enhanced the therapeutic activity of a novel inhibitor of DNA repair, denoted as A83B4C63, encapsulated in PEO-PBCL micelles in reducing the tumor burden in a PTEN negative CRC orthotopic tumor model via synthetic lethality. Finally, modification of polymeric micelles with full-length monoclonal antibody ligands targeting EGFR (i.e., Panitumumab), or carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) was examined and shown to increase micellar association with both HCT116 colorectal cancer cellular populations (i.e., monolayer and spheroid cultures), respectively, when compared to the non-modified micellar counterparts. In conclusion, our results provided a consistent body of evidence showing that the use of tumor-targeting peptide and antibody-based ligands to be an efficient approach for enhancing specificity and delivery of therapeutic cargos (e.g., small molecules), or nanoparticles encapsulating small molecule drugs or siRNA, into breast tumor and CRC models. Nevertheless, the choice of the tumor-targeting ligand and cargo (nanoparticle, versus small molecule) affects the extent and kinetics of tumor interaction and accumulation.

• Subjects / Keywords

  • biodistribution
  • nanomedicine
  • cancer
  • micelles

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-5141-r867

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.