Development of tumour-targeted gene delivery systems for intravenous cancer therapy

  • Stephen Amoah-Nyako

Student thesis: Master's Thesis

Abstract

The use of gene therapy as a form of cancer treatment is currently limited due to the lack of safe and efficacious gene delivery systems that are able to selectively deliver therapeutic genes to tumours after intravenous administration. The conjugation of ligands to delivery systems for receptors that are overexpressed on tumours can enhance the delivery of a therapeutic gene to tumour cells. However, as most commonly targeted receptors for cancer gene therapy are also expressed on non-target cells, this may also lead to the unintended uptake of the delivery system in other areas. The transferrin receptor is over expressed on many cancer cells and can bind to transferrin, an iron binding glycoprotein involved in the transport of iron into cells, and lactoferrin, a member of the transferrin family. Cell penetrating peptides have the ability to transport molecules across cell membranes via non receptor mediated endocytosis. To increase the specificity of tumour targeting, it was hypothesised that the addition of two ligands were attached to a gene delivery system may result in enhanced gene expression when compared to a single ligand. Generation 3- diaminobutyric polypropylenimine (DAB) dendrimer was conjugated to transferrin, lactoferrin and lysine leading to sustained tumour regression. It was therefore envisaged to combine these together to determine if gene expression could be enhanced and an increase in its therapeutic effect. DAB was conjugated with transferrin and lysine (DAB-Tf-Lys) or lactoferrin and lysine (DAB-Lf-Lys) at various ligand: ligand ratios. The average sizes of the dual ligand dendriplexes ranged from 89 nm to 1138 nm, and were dependent upon the ligand weight ratio and the dendrimer: DNA weight ratio. DAB-Tf-Lys with a ligand weight ratio of 1:5 and 4:2 and DAB-Lf-Lys with a ligand weight ratio of 1:5, 4:2, 5:1 and 6:6 were found to condense more than 75% of the DNA independent of dendrimer: DNA weight ratios. The dual ligand dendriplexes were able to transfect B16-F10 cells, with DAB-Tf-Lys 2:4, DABTf- Lys 3:3, DAB-Lf-Lys 1:5, DAB-Lf-Lys 2:4 and DAB-Lf-Lys 5:1 resulting in an enhancement in gene expression that was approximately between 6.0- to 7.6-fold increase of the unmodified DAB. The anti-proliferative activity of theses dual ligand dendriplexes in B16-F10 cells is still to be determined. These results suggest that the dual ligand dendriplexes (DAB-Tf-Lys 2:4, DAB-Tf-Lys 3:3, DAB-Lf-Lys 1:5, DAB-Lf-Lys 2:4 and DAB-Lf-Lys 5:1) may have some therapeutic benefit in cancer therapy, but further work is needed before using these delivery systems in vivo.
Date of Award29 Apr 2016
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorChristine Duf├Ęs (Supervisor) & Ruangelie Edrada-Ebel (Supervisor)

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