Engineered mesenchymal stem cells as therapeutic vehicles for tumor therapy

Dohmann, Maike (2025): Engineered mesenchymal stem cells as therapeutic vehicles for tumor therapy: angiogenesis-based targeting and the influence of thyroid hormones. Dissertation, LMU München: Medizinische Fakultät

Abstract

New approaches are slowly improving the outcomes of cancer patients. The use of engineered versions of mesenchymal stem cells (MSCs) is currently under investigation as a platform to deliver therapeutic genes to solid tumors. This approach makes use of the robust tumor tropism of adoptively applied mesenchymal stem cells to deliver a therapeutic gene such as a suicide gene or cytokine deep into the tumor environment. This thesis focused on the effect of thyroid hormones in the context of mesenchymal stem cell biology, and specifically, on the influence of thyroid hormones on tumor angiogenesis. To this end, an in vitro angiogenesis assay was established. (See results 4.1.) In parallel, a novel cloning platform was applied for the expression of novel reporter transgenes linked to tumor hypoxia and angiogenesis biology. (See results 4.2.) Stable transgenes were introduced into primary human mesenchymal stem cells making use of gene promoters activated in the context of the tumor stroma and tumor angiogenesis. These included a synthetic Hif-1α - driven promoter that is responsive to hypoxia, a human VEGF promoter thought to be activated in early angiogenesis, and the Tie2 promoter, the promoter driving expression of the TEK receptor tyrosine kinase receptor that binds angiopoietin and plays an important role in late angiogenesis. The gene promoters were engineered to drive expression of a secreted version of the Gaussia luciferase as a reporter gene. While the synthetic Hif-1α - responsive promoter did show induction following treatment of MSCs with CoCl2, an agent that can mimic a hypoxic milieu, in a significant dosis-dependant way, similar stimulation of MSCs containing the VEGF promoter reporter constructs did show a significant activation, but not in a dosis-depandant way. Stimulation of MSCs, transfected with the Tie2 promoter, with CoCl2 not induce promoter activity. The study then focused on the influence of thyroid hormones on tumor angiogenesis in context of MSC biology. MSCs containing one of the three reporter constructs Hif-1α, Tie2 and VEGF were then stimulated with thyroid hormones with and without CoCl2. For all constructs a slight enhancement in Gaussia light reaction was seen for T3, especially in combination with CoCl2. (See results 4.3.) When applying the in vitro angiogenesis assay, human endothelial cells (HUVECS) and mesenchymal stem cells (MSCs) were both shown to generate solid tube formation in vitro while the hepatocellular carcinoma cell line (HUH7) used in this study did not. Thyroid hormones have been previously shown to influence aspects of MSC biology and angiogenesis. A dose-dependent activation could be seen for T3 and T4 stimulation of endothelial cells in the context of the angiogenesis assay. Stimulation of HUVECs with MSC conditioned media plus T3 or T4 lead to an increase in experimental angiogenesis. (See results 4.4.) The last series of experiments combined the angiogenesis assay and the genetically modified transgene MSCs. MSCs containing Hif-1α, Tie2 and VEGF reporter plasmids were tested in the angiogenesis assay with and without thyroid hormones. While most of the results were not significant, a significant result was seen for MSCs containing Hif-1α in the angiogenesis after stimulation with T3. (See results 4.5.) The results suggest that thyroid hormones T3 and T4 influence tumor angiogenesis and partly through activation of MSCs. Next to the goals stated above, the aim was to lay the foundation of future individualized tumor-target therapy to enhance the outcome of cancer patients.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: mesenchymal stem cells, angiogenesis, thyroid hormones, gene therapy, cancer
• Themengebiete: 600 Technik, Medizin, angewandte Wissenschaften ; 600 Technik, Medizin, angewandte Wissenschaften > 610 Medizin und Gesundheit
• Fakultäten: Medizinische Fakultät
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 23. Januar 2025
• 1. Bericht­erstatter:in: Nelson, Peter