Abstract 2622: TMEFF2 inhibits human prostate cancer cell migration through its G protein activating domain.

Abstract

Abstract The type I transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) is expressed mainly in brain and prostate. Expression of TMEFF2 is deregulated in a significant fraction of primary and metastatic prostate, suggesting a role in this disease. In fact, we have previously shown that TMEFF2 can function as a tumor suppressor in vitro, inhibiting monolayer and anchorage-independent cellular growth in HEK293T cells and sarcosine-induced cell migration and invasion in benign prostate epithelial RWPE-1 cells. However, the molecular mechanisms involved in the tumor suppressor phenotype of TMEFF2 are not clear. TMEFF2 has several biologically important features. The extracellular domain contains two follistatin domains and an epidermal growth factor-like (EGF) domain, while the transmembrane domain and short cytoplasmic tail have features resembling a G protein activating domain, suggesting that it may signal through a G protein. We hypothesize that the tumor suppressor activity of TMEFF2 is, at least in part, due to signaling mediated by the putative G protein activating domain. In order to test this hypothesis, here we investigate the role of TMEFF2 and a mutant lacking the cytoplasmic tail on cellular migration of prostate cancer cells, and begin analyzing the molecular mechanisms involved in this effect. Our results demonstrate that overexpression of TMEFF2 in human prostate cancer cell line RWPE-2 causes about 60% decrease in cellular migration as assessed by wound-healing assays. Interestingly, we found that RWPE-2 cells overexpressing TMEFF2 have a defect in cell spreading on culture dishes (∼20% decrease) as well as on vitronectin-coated coverslips (∼30% decrease) and that this defect is accompanied by abolished focal adhesion and stress fiber formation. Moreover, the inhibition of TMEFF2 on cellular migration is dependent on its G protein activating domain as deletion of this domain rescues migration, spreading on vitronectin, and focal adhesion formation. The specific G protein pathway(s) involved in the anti-migratory effect of TMEFF2 is currently under investigation. In summary, the data presented here indicate, for the first time, that the anti-migratory effect of TMEFF2 in human prostate cancer cells is mediated by its G protein activating domain. These results raise the possibility that TMEFF2 agonists may be used as therapeutic agents to mediate tumor suppression via this pathway. Citation Format: Xiaofei Chen, C. Justus, L Yang, M.j. Ruiz-Echevarria. TMEFF2 inhibits human prostate cancer cell migration through its G protein activating domain. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2622. doi:10.1158/1538-7445.AM2013-2622