Treatment of 3D In Vitro Tumoroids of Ovarian Cancer Using Photochemical Internalisation as a Drug Delivery Method

Photochemical internalisation (PCI) is a means of achieving spatio-temporal control of cytosolic drug delivery using sub-lethal photodynamic therapy (PDT), with a photosensitiser that can be activated by non-ionising visible light. Various 3D models including those developed at our laboratory, where spheroids are grown in a compressed collagen matrix, have been used for studying anti-cancer drug effects. However, the use of a more biomimetic tumouroid model which consists of a relatively hypoxic central cancer mass surrounded by its microenvironment (stroma) has not yet been explored in either toxicity or phototoxicity studies involving PCI. Here, we examined the efficacy of PCI using a porphyrin photosensitiser and a cytotoxin (Saporin) on ovarian cancer tumouroids, with HEY ovarian cancer cells in the central cancer compartment, and HDF fibroblast cells and HUVEC endothelial cells in the surrounding stromal compartment. The efficacy was compared to tumouroids treated with either Saporin or PDT alone, or no treatment. PCI treatment was shown to be effective in the tumouroids (determined through viability assays and imaging) and caused a considerable decrease in the viability of cancer cells both within the central cancer mass and those which had migrated into the stroma, as well as a reduction in the cell density of surrounding HUVEC and HDFs. Post-treatment, the mean distance of stromal invasion by cancer cells from the original cancer mass following treatment with Saporin alone was 730 μm vs. 125 μm for PCI. PDT was also effective at reducing viability in the central cancer mass and stroma but required a higher photosensitiser dose and light dose than PCI. Tumouroids, as tissue mimics, are suitable models for interrogating multicellular events following pharmacological assault.

Synergy between Photodynamic Therapy and Dactinomycin Chemotherapy in 2D and 3D Ovarian Cancer Cell Cultures

In this study we explored the efficacy of combining low dose photodynamic therapy using a porphyrin photosensitiser and dactinomycin, a commonly used chemotherapeutic agent. The studies were carried out on compressed collagen 3D constructs of two human ovarian cancer cell lines (SKOV3 and HEY) versus their monolayer counterparts. An amphiphilc photosensitiser was employed, disulfonated tetraphenylporphine, which is not a substrate for ABC efflux transporters that can mediate drug resistance. The combination treatment was shown to be effective in both monolayer and 3D constructs of both cell lines, causing a significant and synergistic reduction in cell viability. Compared to dactinomycin alone or PDT alone, higher cell kill was found using 2D monolayer culture vs. 3D culture for the same doses. In 3D culture, the combination therapy resulted in 10 and 22 times higher cell kill in SKOV3 and HEY cells at the highest light dose compared to dactinomycin monotherapy, and 2.2 and 5.5 times higher cell kill than PDT alone. The combination of low dose PDT and dactinomycin appears to be a promising way to repurpose dactinomycin and widen its therapeutic applications.

Therapeutic enhancement of a cytotoxic agent using photochemical internalisation in 3D compressed collagen constructs of ovarian cancer

Photochemical internalisation (PCI) is a method for enhancing delivery of drugs to their intracellular target sites of action. In this study we investigated the efficacy of PCI using a porphyrin photosensitiser and a cytotoxic agent on spheroid and non-spheroid compressed collagen 3D constructs of ovarian cancer versus conventional 2D culture. The therapeutic responses of two human carcinoma cell lines (SKOV3 and HEY) were compared using a range of assays including optical imaging. The treatment was shown to be effective in non-spheroid constructs of both cell lines causing a significant and synergistic reduction in cell viability measured at 48 or 96 h post-illumination. In the larger spheroid constructs, PCI was still effective but required higher saporin and photosensitiser doses. Moreover, in contrast to the 2D and non-spheroid experiments, where comparable efficacy was found for the two cell lines, HEY spheroid constructs were found to be more susceptible to PCI and a lower dose of saporin could be used. PCI treatment was observed to induce death principally by apoptosis in the 3D constructs 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. STATEMENT OF SIGNIFICANCE: Assessment of new drugs or delivery systems for cancer therapy prior to conducting in vivo studies often relies on the use of conventional 2D cell culture, however 3D cancer constructs can provide more physiologically relevant information owing to their 3D architecture and the presence of an extracellular matrix. This study investigates the efficacy of Photochemical Internalisation mediated drug delivery in 3D constructs. In 3D cultures, both oxygen and drug delivery to the cells are limited by diffusion through the extracellular matrix unlike 2D models, and in our model we have used compressed collagen constructs where the density of collagen mimics physiological values. These 3D constructs are therefore well suited to studying drug delivery using PCI. Our study highlights the potential of these constructs for identifying differences in therapeutic response to PCI of two ovarian carcinoma lines.