Endothelial cell metabolism in cancer

Vascular endothelial growth factor (VEGF) is one of the key regulators of angiogenesis and the most important target of anti-angiogenic therapies in several cancer entities. However, lack of efficiency as well as primary resistance to anti-angiogenic therapies necessitate the development of alternative mechanistically distinct therapeutic strategies. Inhibition of tumor growth by starving the pathological vessels themselves from critical metabolic fuel and energy is a highly innovative approach in the field of angiogenesis. When quiescent endothelial cells (ECs) switch to rapid vessel sprouting (angiogenic switch) they adapt their metabolism to generate additional energy and biomass used for growth and cellular proliferation. Briefly, the angiogenic switch requires an angiogenic metabolic switch to adapt EC behaviour. Moreover, it has been shown that cancer cells overcome VEGF inhibition by up-regulating alternative pro- angiogenic signals to bypass anti-VEGF therapy; however EC metabolism continues to act as regulator of EC proliferation downstream of these alternatively upregulated signals. Hence, targeting EC metabolism might offer unprecedented opportunities for the development of alternative anti- angiogenic therapies. The aim of the present research application is to profile EC metabolism in a forward direction: We will analyse EC cell culture models and isolate ECs from mouse- and human (colorectal- and lung cancer) tumors with the aim to identify metabolic pathways deregulated in cancer. We will deploy a multidisciplinary strategy, focusing on targeted profiling of metabolism, thereby taking profit from the fact that disease-ECs have a metabolic memory, which makes it possible to study their metabolic changes in culture. Targeted methods like gas chromatography-mass spectrometry will be used to study predefined metabolic parameters (eg. metabolites, metabolic pathway flux, oxygen consumption, levels of specific, well-characterized metabolites) with high level of specificity and accuracy. In addition, metabolic changes are accompanied by alterations of metabolic genes expression. Thus, we aim to complement the metabolic profiling by unbiased gene expression profiling (mRNA-Seq) and to confirm the importance of identified deregulated genes in cancer endothelial cell biology using in vitro experiments (depending on progress also in vivo experiments). In summary, the present grant application intends to introduce the applicant in a highly innovative field of angiogenic cancer research supervised by Professor Carmeliet, who connects both long-term expertise in angiogenesis and recently acquired know-how in EC metabolism.

Tumors are decisively dependent on the ability to induce blood vessel formation (angiogenesis) to further growth as well as to form metastases. The vascular endothelial growth factor (VEGF) is the central regulator of tumor angiogenesis and thus the primary target of conventional anti-angiogenic drugs. These drugs aim to block the growth of the tumor by starvation to death. Interestingly, tumors have the ability to rapidly develop resistance to these drugs, so the success of the therapy usually only persists for a short time. A new concept to overcome this resistance is to inhibit the endothelial cells (EC) energy and nutrient supply. EC are lining blood vessels inside and play an important role in the process of angiogenesis. Simply speaking, this means blocking the engine of the EC. We were able to show for the first time that isolated mouse and human tumor EC (TEC) differ significantly from healthy normal EC (NECs) metabolically, transcriptomically and morphologically. Concluding that TEC show an increased demand for energy production and nutrient consumption. In mouse TEC we prove that reduction of glycolysis (pharmacological and genetic silencing of a key regulator of glycolysis) led to tumor vessel normalization and reduced metastasis formation. The results of the multi-omics profiling of human TEC lead to several new biological findings and new target identification (TEC metabolism influences extracellular matrix remodeling, TEC as immune gatekeepers). Interestingly, we could also identify that TEC acquire hallmarks of cancer cells such as genetic instability (GIN), an overlooked topic until recently, which has major impact on further anti-angiogenic drug design and understanding of resistance to the currently used drugs. Based on our results, new therapeutic targets for anti-angiogenic therapies could be identified and clinical studies focusing on tumor vessel normalization should be started. Furthermore, TEC GIN should be studied as major contributor to anti-angiogenic resistance to common used anti-VEGF blockers.