1. Introduction
Angiogenesis is the process through which new capillaries are sprouted from pre-existing ones (Eilken et al., 2010). And the components of the vascular wall are basement membrane, pericytes, vascular smooth muscle cells and endothelial cells (Carmeliet et al., 2011). The concept of antiangiogenic therapy, inhibition of angiogenesis could inhibit tumor growth, started after an observation by Folkman discovering new vessel production during tumors growth (Folkman, 1971). It is now relatively cleared that angiogenesis plays an important role in tumor metastasis and growth (Vasudev et al., 2014; Bielenberg et al., 2015). The angiogenic system is required for tumor tissue to grow and develop, and angiogenesis is a complex process involving an interaction between soluble factors, extracellular matrix (ECM) components and endothelial cells(ECs) (Patan, 2000). The early stage of angiogenesis occurs dynamic functions of ECs including proliferation, migration and maturation (Griffioen et al., 2000). The significant event in tumor angiogenesis is endothelial cell migration, which relys on the assembly of protease-protein complexes in front of migrating cells to degrade the basement membrane and invade the matrix of adjacent tissues (Ausprunk et al., 1977; Liekens et al., 2001). Notably, the chronic imbalance of proangiogenic and antiangiogenic factors leads to abnormal angiogenesis in tumor tissues (Goel et al., 2011; Carmeliet et al., 2011).
Aspirin (acetylsalicylic acid, ASA) is an old medicine that was originally extracted from willow bark and is widely used in the prevention and treatment of cardiovascular and cerebrovascular diseases (Desborough et al., 2017). It is absorbed in the gastrointestinal tract after oral administration of aspirin in man, and then converted into salicylic acid (SA) which is further metabolized to salicyhxic acid, gentisic acid, gentisuric acid (2,5-DHBA), salicyl acyl glucuronide, and salicyl phenolic glucuronide (Rumble et al., 1981). During the circulation process, the biological activity of salicylic acid is impaired due to the large amount of salicylic acid (50-80%) bound to albumin, which is because the free salicylic acid has biological activity (Hua et al., 2019).
Increasing evidence have shown that long-term regular aspirin use can significantly reduce the risk of overall cancer (Cao et al., 2016). These effects may be related to the antiangiogenic ability of aspirin (Pearce et al., 2003; Yoshida et al., 2003; Tsujii et al., 1998). Here, we update recent researches on the antiangiogenic effects of aspirin in cancer prevention and treatment, and analyze the several molecular mechanisms of the antiangiogenesis effects for cancer by aspirin.