Mohammad Hadi, Layla; (2019) Photobiological studies of a drug delivery system for the treatment of breast and ovarian cancer using 3D in vitro models. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Photochemical internalisation (PCI) is a method for enhancing delivery of drugs such as cytotoxins to their intracellular target sites of action through the use of low dose photodynamic therapy (PDT). One of the main applications of PCI is local treatment of solid cancerous tumours. The use of three-dimensional (3D) tissue culture cancer models can provide more physiologically relevant information compared to standard monolayer culture owing to the present of an extracellular matrix. The aim of this study was to examine the effect of PDT and PCI in 3D compressed collagen cancer constructs of breast and ovarian cancer. The use of plastically compressed collagen confers near physiological densities of collagen unlike standard hydrogels. In the first set of PCI studies, a disulfonated porphyrin (TPPS2a) was used as the photosensitiser together with a cytotoxic macromolecule, a ribosome inactivating protein (saporin) to investigate the efficacy of the treatment in spheroid and non-spheroid compressed collagen 3D constructs of breast and ovarian cancer versus conventional 2D culture. Three human cell lines were investigated, a breast cancer cell line (MCF-7) and two ovarian cancer cell lines (SKOV3 and HEY). Using a range of assays including optical imaging, the treatment resulted in significant and synergistic reduction in viability of cells in the 2D and non-spheroid constructs of all 3 cell lines when measured at 48 or 96 hours post-illumination. In a further set of experiments, PCI-induced enhancement in cytotoxicity was observed when Dactinomycin was used as the cytotoxic agent. This is the first time that PCI with Dactinomycin has been investigated. In the larger spheroid constructs of ovarian cancer cells, PCI was still effective but required higher saporin and photosensitiser doses compared to 2D and non-spheroid cultures. PCI treatment was observed to induce death principally by apoptosis in the non-spheroid constructs of ovarian cancer compared to the mostly necrotic cell death caused by PDT. At low oxygen levels (1%) both PDT and PCI were significantly less effective in the constructs compared to 2D models. Using the 3D tumouroid model, where a central cancer mass is surrounded by the collagen matrix populated by fibroblasts to simulate the stroma, PCI was found to be able to both kill ovarian cancer cells within the cancer mass and inhibit their migration to the stroma. In conclusion, the use of 3D cancer models provides a useful means to assess the efficacy of PCI for the minimally invasive treatment of breast and ovarian cancer prior to in vivo studies and could help reduce the number of animals used in animal experimentation.

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