Department of Physiological Sciences

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Browsing Department of Physiological Sciences by browse.metadata.advisor "Fourie, Carla"

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    The tumour microenvironment: the effect of breast cancer cell conditioned medium on the endothelium
    (Stellenbosch : Stellenbosch University, 2023-03) Rass, Atarah Melanie Rose; Engelbrecht, Anna-Mart; Fourie, Carla; Marais, Erna; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.
    ENGLISH ABSTRACT: Background: Breast cancer is the most common cancer diagnosed in women and the most common cancer globally. The human mammary gland is comprised of epithelium and vascular rich stroma. It has been established that breast cancer cells interact with and alter their stroma and neighbouring cells, to establish a tumour microenvironment (TME). Mammary endothelial cells are key targets to be transformed into tumour endothelial cells (TECs). These cells are genetically and phenotypically distinct from their normal, healthy counterparts and provide various pro-tumourigenic effects. These effects are modulated by the expression of various molecules that have been classified as TEC markers based on their expression in TECs compared to normal endothelial cells. As central role players in angiogenesis, TECs are key to tumour angiogenesis. Anti-angiogenic agents have proven to be effective, yet act as a double-edged sword, as a result of downstream complications and side effects. TECs therefore serve as potential targets for therapeutic intervention. Various role players in the tumour microenvironment have been investigated, but the effect of breast cancer cells on the tumour endothelial phenotype is not well established. The aims of this study were to evaluate a TEC phenotype in breast cancer and investigate how breast cancer impacts angiogenesis. Methods: Conditioned medium (CM) was harvested from non-malignant (MCF-12A) breast epithelial cells and from malignant (MCF-7 and MDA-MB-231) breast cancer cells starved of supplements and growth factors for 24 hours. Endothelial cells (HUVECs) were then treated with CM for 24 hours. To evaluate a TEC phenotype in breast cancer, cell viability (WST-1 assay), cell morphology (phase contrast imaging), and gene (reverse transcriptase-quantitative polymerase chain reaction) and protein (Western blots) expression of markers associated with a TEC phenotype were assessed. To assess angiogenesis in breast cancer, cell migration (scratch assay) and tube formation (tube formation assay) assays were utilised. A comparative model of non-malignant versus malignant signalling was used throughout the study. Results: Breast cell CM significantly increased HUVEC cell viability in all treatment groups. Changes in morphology were observed, which included elongation and branching, and occurred to a greater degree in malignant CM groups. TEC markers were significantly upregulated in response to non- malignant signalling and tumour endothelial marker 8 was observed to contribute to the TEC phenotype in breast cancer. Significant changes in cell migration were observed in the MCF-7 CM group. Furthermore, clear qualitative differences in the tube formation of HUVECs were noted in malignant groups compared to the non-malignant group. Conclusion: Our results highlight the fact that endothelial cells are highly responsive to interactions with nutrient deprived breast cells but the interaction with non-malignant breast cells compared to malignant breast cells is significantly different. Breast cancer cells therefore do alter endothelial cells, but the characteristic TEC phenotype is not specific to a malignant response. Breast cancer cells alter the angiogenic process but the degree of hyperactivation is influenced by the breast cancer phenotype. It is therefore evident that endothelial cells and angiogenesis are altered and key to breast cancer progression, yet a TEC phenotype specific to breast cancer remains to be defined.