pylori infection in the gastric mucosa and that RAS may participate Gefitinib molecular weight in H. pylori infection-related
gastric cancer progression. We also discuss the possibility that the widely used antihypertensive agents angiotensin I converting enzyme inhibitor (ACE-I) and AT1R blocker (ARB), which target the production or action of AngII, are useful for cancer prevention. The RAS is a hormone system that regulates blood pressure and water balance. The system is activated when there is a loss of blood volume or a drop in blood pressure, such as in hemorrhage. When blood volume is low, juxtaglomerular cells in the kidneys secrete renin. The RAS cascade is induced by the action of renin, which cleaves angiotensinogen to produce the inactive decapeptide AngI (Fig. 1). ACE or chymase then cleaves AngI to generate the active octapeptide AngII. Finally, AngII binds NVP-AUY922 solubility dmso to either of two cell membrane
receptor subtypes, AT1R and AT2R, which belong to the G-protein-coupled receptor superfamily. AT1R binds to AngII with higher affinity than AT2R and is more abundantly expressed. Specifically, the AngII-AT1R signaling pathway functions in vasoconstriction, aldosterone synthesis, increased vasopressin secretion, cardiac hypertrophy, vascular smooth muscle cells proliferation, decreased renal blood flow, renal renin inhibition, and central osmocontrol. Two distinct RAS types exist: a circulatory type, which controls blood pressure and cardiovascular homeostasis;
and a local type, which functions in individual organs and tissues (Fig. 1). In humans, the circulatory and local system account for 70–85% and 15–30% of RAS function, respectively, in humans.18 Systemic AngII generation is mediated mainly by ACE, whereas 60–80% of local AngII is produced through chymase activity independently of ACE, with ACE generating the remaining local balance.18 Chymase is produced in inflammatory and cancer cells by paracrine 上海皓元 or autocrine mechanisms. On this basis, although the effect of ACE on local oncogenesis cannot be ignored, given that it accounts for 20–40% of local AngII production in organs and tissues and most RAS activity of the circulatory type, chymase may play a more important role in local oncogenesis. Overexpression of RAS components has been shown to occur in diverse cancer cell types and tissues, including brain, lung, breast, prostate, skin and cervical carcinomas,19,20 as well as gastrointestinal malignancies and normal tissues (e.g. stomach, pancreas and colon). Gastric mucosal cells in patients who are negative for H. pylori express RAS components at low levels (Fig. 2).21 In contrast, H. pylori infection is characterized by marked neutrophil, lymphocyte, monocyte and plasma cell infiltration of gastric mucosa,22 with inflammatory cell numbers closely correlated with increased AT1R and AT2R expression in humans and in a Mongolian gerbil model (Fig. 3a).