Targeting Angiogenesis and Growth Factor Pathways: Implications for Cancer Therapy and Tumor Microenvironment Regulation

Angiogenesis is a critical process in tumor development, involving the formation of new blood vessels from pre-existing ones. Tumor vasculature, unlike normal vasculature, exhibits structural abnormalities, including leaky and poorly organized vessels. These features create a hypoxic and acidic microenvironment, significantly impacting the efficacy of chemotherapeutic interventions and altering endothelial cell physiology. This review synthesizes recent findings on the roles of endothelial cells and tumor vasculature in angiogenesis. It highlights key mechanisms such as endothelial cell migration, proliferation, and the involvement of angiogenic regulators like vascular endothelial growth factor receptor-2 (VEGFR-2) and Delta-like ligand 4 (Dll4)/NOTCH signaling pathways. Endothelial cells play pivotal roles in vascular sprouting, tube formation, and stabilization during angiogenesis. Activation of VEGFR-2 by vascular endothelial growth factor (VEGF) determines endothelial cell fate, orchestrating tip and stalk cell differentiation through Dll4/NOTCH signaling. Additionally, tumor vasculature abnormalities, such as deficient pericyte coverage and elevated interstitial pressure, create challenges for effective drug delivery and promote tumor progression. Despite significant progress in understanding angiogenesis, several unanswered questions remain. Key challenges include identifying the most impactful angiogenic factors, understanding their regulatory mechanisms, and determining whether targeting tumor cells, stromal cells, or endothelial cells is most effective. The interplay between angiogenic factors suggests a complex network that requires further exploration to unravel tumor pathogenesis. Targeting angiogenesis holds promise as a therapeutic strategy. However, the current focus on VEGF pathways has limited the development of alternative anti-angiogenic agents. Future research should prioritize the discovery of novel angiogenic regulators and their interactions to expand therapeutic options.