Abstract B06: The angiotensin receptor blocker and partial PPARγ agonist telmisartan inhibits the growth of pancreatic ductal adenocarcinoma

Abstract

Abstract Pancreatic ductal adenocarcinoma (PDAC) is highly resistant to chemotherapy, partly due to the presence of a dense-fibrotic stroma and adaptive metabolism. Telmisartan is an angiotensin II type receptor 1 (AT1) antagonist with partial peroxisome proliferator-activated receptor gamma (PPARγ) agonistic activity used for treatment of hypertension. The aim of this study was to determine the effects of telmisartan on the viability of PDAC cells and tumor progression. In panels of 4 murine and 8 human PDAC cells, the telmisartan IC50 was lower in cells with a low steady-state expression of PPARγ and a mesenchymal cell morphology. In contrast, losartan—a selective AT1 inhibitor—did not affect the viability of PDAC cells. The siRNA knockdown of PPARγ enhanced the sensitivity of telmisartan and stimulated epithelial-mesenchymal transition, which was accompanied by an increase in Wnt signaling. PPARγ regulates glucose metabolism and autophagy. We thus assessed effects of telmisartan on bioenergetics and autophagy of PDAC cells. In PPARγ-knockdown and -scrambled cells telmisartan significantly reduced glucose uptake, without affecting ATP production, but increased respiratory capacity, which can maintain the production of ATP during hypoglycemia. Immunoblotting revealed that PPARγ knockdown compared to scramble cells had increased levels of phosphorylated-AMP-activated protein kinase (p-AMPK) and increased expression of LC3A/B—structural proteins of autophagosomal membranes—which implies higher levels of autophagy. We also compared effects of telmisartan treatment on LC3A/B expression to well-established autophagy modulators, chloroquine and verapamil. Under nutrient-rich conditions and as expected, chloroquine and verapamil treatment induced LC3A/B accumulation, consistent with active autophagic flux in these cells. Telmisartan treatment decreased the levels of LC3A/B in both scramble and PPARγ knockdown cells and decreased the formation of LC3A/B positive granules in other PDAC cell lines. Telmisartan can also induce the accumulation of the signal adaptor protein p62 (SQSTM1), even in the presence of verapamil, which is also consistent with autophagy inhibition. Telmisartan did not prevent the accumulation LC3A/B in the presence of chloroquine, implying that telmisartan acts after the autophagosome-lysosome fusion step. To assess the effects of telmisartan in vivo, we used an orthotopic PDAC model. Telmisartan monotherapy inhibited the growth of primary tumors, decreased the incidence of liver metastasis, and significantly improved the survival of mice. Hence, telmisartan can reduce autophagy and the viability of PDAC cells, and PDAC progression. Because telmisartan is an FDA-approved drug, our findings provide the scientific rationale for testing its efficacy in the prevention of PDAC progression. Citation Format: Jelena Grahovac, Shiwei Han, Hao Liu, Mark Duquette, Alba Luengo, Daniel Schanne, Andrew S. Liss, Matthew G. Vander Heiden, Rakesh K. Jain, Yves Boucher. The angiotensin receptor blocker and partial PPARγ agonist telmisartan inhibits the growth of pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr B06.