Abstract 5811: HMP19, a pancreatic cancer metastasis suppressor, is secreted in extracellular vesicles and inhibits EGFR activity

Pancreatic cancer is usually diagnosed when the cancer is already at an advanced stage. The presence of metastases contributes to the poor prognosis as do the limited treatment options, resulting in an urgent need for early detection methods and novel treatments. HMP19 was identified as a metastasis suppressor in pancreatic duct adenocarcinoma (PDAC) using unbiased genome wide shRNA screen assay (Kurahara et al. 2016). HMP19 is localized to the membrane of Golgi apparatus and has been implicated in the vesicular trafficking in neurons (Saberan-Djoneidi et al. 1994). HMP19 is a predicted type II, single-pass transmembrane protein with protein binding domains at the N- and C- terminals, although, the physiological function of HMP19 remains undefined. Our lab showed that HMP19 attenuates nuclear ERK1/2 activity in PDAC cells. Furthermore, we found that ectopic HMP19 is secreted in the extracellular vesicles (EVs) in non-metastatic PDAC cell line, Suit2 subclone 028 (S2-028), but not in metastatic PDAC cell line, S2-007. Furthermore, silver staining and mass spectrometry showed that the EVs protein profiles between S2-028 and S2-007 EVs are distinct. We hypothesize that secreted HMP19 regulates cell migration and proliferation, and also negatively regulates signaling pathway(s) upstream of ERK. To examine effects of HMP19-containing EVs on parental cells, HMP19-containg EVs were incubated with parental cells and proliferation and migration then were quantified. HMP19-containing EVs treatment inhibited migration but not proliferation of metastatic S2-007 cells, but not non-metastatic S2-028 cells. We identified several proteins as HMP19 binding partners in the co-immunoprecipitation followed by mass spectrometry study and were subsequently validated by co-immunoprecipitation followed by immunoblot. HMP19 was found to interact with multiple proteins, including ERK regulators such as MET and epithelial growth factor receptor (EGFR). We then investigate the role of HMP19 on the MET and EGFR signaling pathway. Intriguingly, HMP19 down regulates EGFR phosphorylation and protein expression in metastatic S2-007, but not non-metastatic S2-028 PDAC cells. Moreover, HMP19 expression had no effect on phosphorylated and total MET and Janus kinase (JAK) total protein levels. Altogether, the data suggest that HMP19 may inhibit metastasis through down regulation of EGFR signaling pathway. In conclusion, we showed that HMP19 is secreted in EVs and these EVs attenuate PDAC cell migration, and mechanistically, HMP19 down regulates EGFR in metastatic PDAC cells. Future studies will further bridge the effects of HMP19 on the EGFR signaling cascade and the extracellular HMP19-mediated inhibition of migration. Citation Format: Sharon Manley, Gada al-Ani, Danny Welch. HMP19, a pancreatic cancer metastasis suppressor, is secreted in extracellular vesicles and inhibits EGFR activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5811. doi:10.1158/1538-7445.AM2017-5811