In cancer, angiogenesis is a hallmark necessary to supply sufficient nutrients for tumor growth and metastasis to distant sites. Therefore, targeting tumor angiogenesis emerges as an attractive therapeutic modality to retard neoplastic cell growth and dissemination using classes of anti-angiogenic drugs. However, multiple administrations of these drugs show adverse effects, precluding their long-term usage. Conventional chemotherapeutic drugs, natural compounds, carbon-based materials, inorganic and metallic elements, genes, siRNAs, shRNAs, and microRNAs can be incorporated into nanovehicles (e.g. polymers) for delivery to specific targets. This chapter reviews angiogenesis and the underlying molecular mechanisms that regulate this process. Furthermore, this chapter provides an overview on different formulations of nanoparticles or nanovectors that employed to combat cancer, with a special focus on their therapeutic potentials in the context of the suppressive effects on tumor angiogenesis process using in vitro and in vivo models of different tumor entities.
TopCirculatory System
The fundamental difference in the structure of the circulatory system between vertebrate and invertebrate is the presence of a continuous monolayer of luminal epithelial cells, named as endothelium (Monahan‐Earley, Dvorak, & Aird, 2013; Muñoz‐Chápuli, Carmona, Guadix, Macías, & Pérez‐Pomares, 2005). The circulatory system facilitates transportation and exchange of nutrients, gases, and metabolic wastes to and from body cells. Vertebrates have blood vessels through which blood and its components are transported (Muñoz‐Chápuli et al., 2005). The anatomy of the blood vessels is structured based on the size and location into capillary, vein, artery, arteriole, and venule. Capillaries, the smallest blood vessels, have one layer known as tunica intima. By comparison, the largest blood vessels have three layers. The innermost layer, tunica intima, contains endothelium and basement membrane (BM), whereas the BM encloses the endothelium along the entire blood vessels structure in body. The tunica media, which contains elastic fibers and vascular smooth muscle cells (vSMCs), is centered between the tunica intima and tunica externa layers. The function of the outermost layer, tunica externa, is to anchor the vessels to the surrounding tissue via its fibroelastic connective tissues (McConnell, 2013; Ng, Lee, Kuo, & Shen, 2018; Zuyong Wang et al., 2019).