Targeted gene delivery to three-dimensional tumour model by Phage-based nanoparticle

Traditional two-dimensional (2D) cancer cell culture has been used extensively to evaluate the efficacy of drug delivery systems, but it has limitations that can deviate results from a real tumour mass in vivo. The lack of accurate cellular interactions and extracellular matrix (ECM) components are the primary differences between 2D cancer models and an actual tumour in vivo. 2D cell culture also lose tumour heterogeneity. The results obtained from 2D models do not represent the complexity of drug delivery and diffusion that occurs in vivo. In recent years, three-dimensional (3D) tumour models have gained popularity as they can overcome the limitations of 2D models and are physiologically comparable to a real tumour mass. 3D models possess ECM components which resembles in vivo tumours. In 3D culture, drug penetration and distribution are more representative of the tumour microenvironment, allowing us to investigate the efficacy and toxicity of a drug in a more clinically relevant model. Together, this makes 3D culture models suitable for drug delivery research. Phage Cancer Therapy group has employed 3D tumour models to evaluate the efficacy of a gene delivery platform derived from a harmless filamentous bacteriophage (Phage); Transmorphic Phage/AAV (TPA). The TPA particle has many advantages over other gene delivery vectors including low production cost, very low toxicity to normal cells, can be targetable to specific cell type, and does not require low temperature storage. Phage Cancer Therapy group has developed TPA as a multifunctional cancer cell targeted nanocarrier to guide the delivery of therapeutic genes (or drugs) to cancer cells. Capsids of TPA particles were engineered to equip cancer targeting ligand (RGD4C) on the capsids with a therapeutic transgene cassette inside the capsids. The RGD4C ligand specifically binds to ?v?3 and ?v?5, which are specifically overexpressed on tumour cell surface. It is subsequently up taken by, and delivers the therapeutic gene to, cancer cells. We adopted 3D tumour models of various cancer cell types as models to evaluate the efficacy of the novel TPA nanocarrier. We found that cancer stem cell population in our 3D tumour sphere models resemble tumours in vivo. Our novel TPA particle demonstrates promising gene delivery efficiency across many types of 3D cancer models. TPA efficiently penetrated through the ECM and delivered a transgene to targeted cells, ultimately resulting in tumour regression. Furthermore, toxicity tests, in vitro and in vivo, showed that the TPA particle itself does not harm normal cells and organs. We confirmed the efficacy of TPA in an animal model by systemic administration of the particle through the teil vein. TPA can selectively deliver a transgene to tumour cells but spare other organs unharmed. Altogether, the TPA particle has the potential to be a powerful cargo for tumour-targeted gene delivery.