Safe Polymeric Nucleic Acid Delivery Systems for Cancer Therapy: Focus on Breast Cancer and Chronic Myeloid Leukemia

  • Author / Creator
    Meenakshi Sundaram, Daniel Nisakar
  • RNA interference (RNAi) is a promising technology to specifically target the upregulated genes that provide uncontrolled proliferation and survival of cancers. The target specific silencing is accomplished by the delivery of small interfering RNA (siRNA), which require safe delivery systems to protect against serum nuclease degradation and cellular uptake. Lipid-substituted low molecular weight (LMW) polyethylenimine (PEI) polymers are excellent non-viral gene delivery systems which have the potential to establish safe delivery of the therapeutic gene in any cell type. This thesis investigates the potential of lipid-modified PEI delivery systems in the treatment of two different cancer types: breast cancer and chronic myeloid leukemia (CML) representing adherent and non-adherent cancers, respectively. The current challenge in the treatment of breast cancer is their metastatic ability to establish tumors in distant organs which necessitates the need to develop alternate therapeutic options. In this process of metastasis, cell adhesion molecules such as integrins are known to play a major role, especially the upregulation of integrin-β1 has strong correlation with breast cancer progression and metastasis. Hence, we hypothesized that the silencing of such overexpressed molecule would help to decrease breast cancer metastasis. Among the lipid substituted PEIs explored for breast cancer treatment, the linoleic acid (1.2PEI-LA6) substituent provided strong silencing of the overexpressed cell adhesion molecule integrin-β1 at the cell surface and mRNA transcript level. Silencing of integrin-β1 significantly decreased the attachment of breast cancer cells to fibronectin and human bone marrow stromal cells. High cytoplasmic localization of the siRNA achieved by the 1.2PEI-LA6 polymer helped to accomplish strong migration inhibition, reflecting the ability to decrease breast cancer metastasis. Using the same delivery system, we screened a siRNA library of 496 genes targeting various cell adhesion and cytoskeleton molecules, to identify therapeutic targets for breast cancer treatment. We identified the endoplasmic reticulum heat shock protein 90B1 (HSP90B1) as a potential therapeutic target to decrease the growth and migration of breast cancer cells. Furthermore, the inclusion of hyaluronic acid as additives and the combinational silencing of integrin-β1 and HSP90B1 provided significant decrease in the migration of breast cancer cells. Whereas in CML, the treatment against drug resistance developed by the attachment of leukemic cells through integrin-β1 to the bone marrow stromal environment, activates signaling pathways independent of BCR-ABL whose treatment is a challenging task. Silencing of integrin-β1 in CML cells was achieved by thioester linked α-linoleic acid (tα-LA) substituted PEI polymers. Integrin-β1 silencing decreased its binding and increased its detachment from bone marrow stromal cells. A combinational silencing of integrin-β1 and BCR-ABL helped to overcome resistance mediated by fibronectin binding. Exploring the safety of these lipid-modified PEI delivery system revealed the wide dependence on the ratio of PEI and nucleic acid, through toxicity studies in T-lymphocyte and red blood cells. However, differences in the PEI and nucleic acid ratio and the concentration of nucleic acid does not alter the secretion of TNF-α, IL-6 and IFN-γ cytokines from pulmonary blood mononuclear cells. In addition, variations in the lipid type and the number of lipid substitution does not alter the cytokine secretion in comparison to the positive controls. Overall, we successfully established the therapeutic potential of PEI delivery systems among two different cancer types, in addressing breast cancer metastasis and CML drug resistance by siRNA delivery. In addition, we provided the safety information of these PEI delivery systems which are vital during their clinical exploration and for further application in other cancer types.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.