Abstract LB-29: LKB1 tumor suppressor regulates AMP kinase/mTOR-independent cell growth and proliferation via the phosphorylation of Yap

Abstract

Abstract The liver kinase B1 (LKB1) tumor suppressor inhibits cell growth through its regulation of cellular metabolism and apical-basal polarity. The best understood mechanism whereby LKB1 limits cell growth is through activation of the AMP-activated-protein-kinase/mammalian-target-of-rapamycin (AMPK/mTOR) pathway to control metabolism. Since LKB1 is also required for polarized epithelial cells to resist hyperplasia it is anticipated to function through additional mechanisms. Recently, Yes-associated protein (Yap) has emerged as a transcriptional co-activator that modulates tissue homeostasis in response to cell-cell contact. Thus this study examines a possible connection between Yap and LKB1. Restoration of LKB1 expression in HeLa cells, which lack this tumor suppressor, or shRNA knockdown of LKB1 in 293T cells, demonstrated that LKB1 promotes Yap phosphorylation, nuclear exclusion, and proteasomal degradation. The ability of phosphorylation-defective Yap mutants to rescue LKB1 phenotypes, such as reduced cell proliferation and cell size, suggest that Yap inhibition contributes to LKB1 tumor suppressor function(s). Interestingly, LKB1 inhibited Yap independently of either AMPK or mTOR activation. These findings reveal a novel mechanism whereby LKB1 may restrict cancer cell growth via the inhibition of Yap. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-29. doi:1538-7445.AM2012-LB-29