Involvement of angiotensin II type 2 receptor (AT2R) signaling in human pancreatic ductal adenocarcinoma (PDAC): a novel AT2R agonist effectively attenuates growth of PDAC grafts in mice

Abstract

Keywords: angiotensin II type 2 receptor (AT2R), apoptosis, pancreatic ductal adenocarcinoma, selective AT2R agonist Abbreviations: PDAC, pancreatic ductal adenocarcinoma; Ang II, angiotensin II; AT1R, angiotensin II type 1 receptor; AT2R, angiotensin II type 2 receptor; PCR, polymerase chain reaction; cGMP, cyclic guanosine monophosphate; HIF-1, hypoxia inducible factor; VEGF, vascular endothelial growth factor; Ki, association constant; GFP, green fluorescent protein; BSA, bovine serum albumin; PLZF, promyelocytic leukemia zinc finger protein; PI3K, phosphatidylinositol-3 kinase; TUNEL, terminal deoxynucleotidyl transferase dUTP nick end labeling; FBS, fetal bovine serum; DMEM, Dulbecco`s modification of Eagle`s medium; Ad-, adenoviral vector; HBSS, Hanks' balanced salt solution.We have recently discovered the potential involvement of angiotensin II type 2 receptor (AT2R) signaling in pancreatic cancer using AT2R deficient mice. To examine the involvement of AT2R expression in human PDAC, expressions of AT2R as well as the major angiotensin II receptor (type 1 receptor, AT1R) in human PDAC and adjacent normal tissue was evaluated by immunohistochemistry and real time PCR using surgically dissected human PDAC specimens. In immunohistochemical analysis, relatively strong AT1R expression was detected consistently in both normal pancreas and PDAC areas, whereas moderate AT2R expression was detected in 78.5% of PDAC specimens and 100% of normal area of the pancreas. AT1R, but not AT2R, mRNA levels were significantly higher in the PDAC area than in the normal pancreas. AT2R mRNA levels showed a negative correlation trend with overall survival. In cell cultures, treatment with a novel AT2R agonist significantly attenuated both murine and human PDAC cell growth with negligible cytotoxicity in normal epithelial cells. In a mouse study, administrations of the AT2R agonist in tumor surrounding connective tissue markedly attenuated growth of only AT2R expressing PAN02 murine PDAC grafts in syngeneic mice. The AT2R agonist treatment induced apoptosis primarily in tumor cells but not in stromal cells. Taken together, our findings offer clinical and preclinical evidence for the involvement of AT2R signaling in PDAC development and pinpoint that the novel AT2R agonist could serve as an effective therapeutic for PDAC treatment.

Small‐molecule AT2 receptor agonists

“…109 The octapeptide attenuates growth of pancreatic ductal adenocarcinoma (PDAC) grafts in mice. 110 A comprehensive review on angiotensin peptides as AT2R agonists was recently published. 111 The non-selective thiofen derivative L-162,313 (10) (AT1R; IC 50 = 1.1 nM and AT2R; IC 50 = 2.0 nM), was reported in 1994…”

“…Furthermore, displacement of His6 in Ang II for Tyr 6 creates the very potent AT2R agonist Tyr 6 Ang II that exhibits a remarkably high, AT2R/AT1R selectivity . The octapeptide attenuates growth of pancreatic ductal adenocarcinoma (PDAC) grafts in mice . A comprehensive review on angiotensin peptides as AT2R agonists was recently published .…”

“…Another area of potential therapeutic benefit of AT2R agonists such as 8 is cancer. Notably, regarding cancer and based on experiments with 8 or an AT2R selective peptide agonist, it was proposed that AT2R agonists might find a therapeutic role in the treatment of pancreatic ductal adenocarcinoma, prostate cancer, lung cancer, hepatocellular carcinoma, epithelial ovarian carcinoma, colorectal carcinoma, uterine leiomyosarcoma, and Lewis lung carcinoma …”

“…Displacements of the methylene imidazole group of C21/M24 with benzylamide, acetic acid amide and other groups Displacements of the imidazole group of C21/M24 with benzoic acid amide groups Receptor selective AT2R agonists and antagonists hepatocellular carcinoma, epithelial ovarian carcinoma, colorectal carcinoma, uterine leiomyosarcoma, and Lewis lung carcinoma 82,94,110,[151][152][153][154][155]. …”

GPCRs in pancreatic adenocarcinoma: Contributors to tumour biology and novel therapeutic targets

“…A role for AT 2 receptors in tumour cells and cell lines has been suggested via effects on migration or proliferation, which are blunted by AT receptor antagonists (e.g. Anandanadesan et al, 2008; Fujimoto, Sasaki, Tsuchida, & Chayama, 2001; Gong, Davis, Chipitsyna, Yeo, & Arafat, 2010; Ishiguro et al, 2015; McGhee et al, 2011). It is difficult to reconcile these findings with expression data from databases on cancer cells, showing very low expression of AT 1 receptor in pancreatic adenocarcinoma cell lines and virtually no expression of AT 2 receptor in tumour tissue, cancer cells or CAFs.…”