Abstract 1990: Identification and biochemical characterization of HMP19, a tumor/metastasis suppressor in pancreatic cancer

Abstract

Abstract The overwhelming majority of pancreatic cancer is not diagnosed until the cancer has metastasized, which leads to an abysmal average life expectancy (3 to 6 months post-diagnosis). Earlier detection and more effective treatments have been hampered by inadequate understanding of the underlying molecular mechanisms controlling metastasis. Metastasis suppressors inhibit metastasis without blocking orthotopic tumor growth and represent powerful new targets and biomarkers. We hypothesize that metastasis suppressors are involved in controlling metastasis in pancreatic cancer. Using an unbiased genome wide shRNA screen, we identified HMP19 as a putative metastasis suppressor in pancreatic ductal adenocarcinoma (PDAC). Functional validation was carried out by manipulating expression in PDAC cell lines. Knockdown of HMP19 in S2-028 cells increased orthotopic tumor growth and liver metastasis, while over-expression in S2-007 cells slowed tumor growth and suppressed metastasis in xenographs. HMP19 expression inversely correlated with in vitro migration, colony formation, proliferation, and cyclin E1 expression. In clinical samples, HMP19 expression inversely correlated with tumor size, plexus invasion, liver metastasis, and patient survival (p<0.05). HMP19 is essentially uncharacterized, except for reported sub-cellular localization in the Golgi apparatus in neuronal cells (Saberan-Djoneidi et al. 1994). HMP19 is localized throughout the secretory/endocytic pathways (fluorescence microscopy), including at the plasma membrane (surface biotinylation). HMP19 is predicted to be a type II, single-pass transmembrane protein with 3 domains (cytoplasmic; transmembrane; extracellular). However, the ability to biotinylate HMP19 in intact S2-028 cells expressing the predicted cytoplasmic+transmembrane domains suggest that HMP19 might be a type I transmembrane protein. The cytoplasmic tail and transmembrane domains are important for protein stability, while the presence of multiple bands in immunoblots (16, 19, 21, and 25 kDa) suggests that HMP19 is post-translationally modified by an as-yet defined mechanism. Interestingly, we found that HMP19 co-immunoprecipitates with and suppresses phospho-ERK nuclear localization. Here we describe the discovery and characterization of a novel PDAC metastasis suppressor and potential mechanism of action, which is in support of our hypothesis that metastasis suppressors control metastasis in pancreatic cancer. Support: National Foundation for Cancer Research, Hall Family Foundation, Kansas Bioscience Authority, and CA134981 Citation Format: Christopher R. Bohl, Hiroshi Kurahara, Shoji Natsugoe, Yuka Nishizono, Sitaram Harihar, Tomoo Iwakuma, Danny R. Welch. Identification and biochemical characterization of HMP19, a tumor/metastasis suppressor in pancreatic cancer. [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 1990. doi:10.1158/1538-7445.AM2014-1990