Abstract 4214: Antitumoral effects of orexins and their receptors OX1R in pancreatic ductal adenocarcinomas (PDAC)

Abstract

Abstract Orexins A and B were identified as hypothalamic ligands for two serpentine G protein-coupled receptors, OX1R and OX2R. Aberrant expression of OX1R was detected in colonic cancer cells and hepatic metastasis. Orexins induce apoptosis in human colon cancer cell lines and in mice models, resulting in massive reduction of tumor cell growth. Pancreatic ductal adenocarcinomas (PDAC) are highly malignant neoplasms with poor prognosis. Chemotherapy treatment shows a poor response rate. Our previous data suggested the expression of OX1R in 98% of tested PDAC. The aims of this study were 1) to investigate the presence of OX1R in human PDAC cell lines and to analyse orexin-A (OX-A) effects in relation to apoptosis and 2) to develop an in vivo heterotopic xenografted model from the cell lines expressing OX1R, for the study of tumor growth in response to OX-A. The expression of OX1R was studied at mRNA (RT-PCR), proteins (immunocytochemistry) and functional levels (number of viable cells after OX-A treatment), in 3 PDAC cell lines (AsPC-1, HPAF-II and SW 1990). The development of an animal model (heterotopic xenograft) from the cell line expressing OX1R, has allowed studying the effect of OX-A in tumor growth. Resected tumors were analyzed by immunohistochemistry. Only AsPC-1 cell line expresses OX1R. The treatment with OX-A promoted a 32% cell growth inhibition. OX-A injection in nude mice xenografted with AsPC-1 cells, has declined 49% of tumor progression in treated cases. This effect was dose-dependent and more important in weekly or twice-weekly treatments. All the tumors corresponded to poorly differentiated adenocarcinomas expressing OX1R. Induction of apoptosis was observed in OX-A treated tumors (activated caspase-3). To generalize further the role of OX1R in inhibition of cell growth and induction of apoptosis, we considered HPAF-II cells expressing the recombinant hOX1R. Orexin-A strongly inhibited HPAF-II/OX1R cell growth in vitro and tumor growth in vivo, whereas no effect of orexins could be detected in the parental HPAF-II cell line. The role of OX1R in controlling apoptosis is directly demonstrated by the expression of recombinant OX1R in HPAF-II cells that confers the ability of orexins to promote apoptosis in this cell line. This work has demonstrated the antitumor and proapoptotic effect of orexins in PDAC, using in vitro and in vivo models. In this context, orexines receptors may establish a new therapeutic target in pancreatic antineoplastic therapies. Citation Format: Thierry Voisin, Daniela Speisky, Anne Couvelard, Alain Couvineau. Antitumoral effects of orexins and their receptors OX1R in pancreatic ductal adenocarcinomas (PDAC). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4214. doi:10.1158/1538-7445.AM2014-4214