Abstract 4893: AKT1 signaling negatively regulates invasion and metastasis of non-small cell lung cancer cells carrying mutations in KRAS or EGFR

Abstract

Abstract Signaling driven by the phosphoinositide-3 kinase (PI3K) and AKT/protein kinase B (PKB) pathway plays an important role in cancer development and progression, and thus this pathway is an attractive therapeutic target. Although many different inhibitors targeting either PI3K or AKT have been developed, the therapeutic benefit of these inhibitors in the clinic remains elusive, in part because of the perplexing role of AKT signaling in the regulation of cell motility, invasion and metastasis. AKT activation is known to promote migration, invasion and metastasis; however under certain circumstances and different cellular systems, it also exhibits an inhibitory activity on these cellular processes and the underlying cause of these conflicting results is unclear. Through analysis of the Reverse Phase Protein Array (RPPA) performed on a series of non-small cell lung cancer (NSCLC) brain metastasis models generated via intracardiac injection in mice, we identified AKT1 (one of three AKT family members) as a critical negative regulator of A549 tumor metastasis. AKT1 tyrosine phosphorylation (but not AKT2 or AKT3) inversely correlated with the metastatic potential of A549 cells which carry a KRAS mutation. Using AKT1 siRNAs, we demonstrated that inhibition of AKT1 significantly enhanced migration and invasion of KRAS- or EGFR-mutant NSCLC cells, but not wild type KRAS and EGFR cells. Similarly, the AKT inhibitor MK-2206 also enhanced the migration and invasion of KRAS- or EGFR-mutant NSCLC cells in vitro, and promoted metastasis of KRAS-mutant A549 cells in vivo. The PI3K-AKT pathway is downstream of both EGFR and KRAS, whose constitutive activation caused by mutations likely alter the signal output of PI3K-AKT pathway and thus the activity on cell invasiveness. Therefore, our results provide a sound explanation that under certain genetic backgrounds (as we demonstrated here with KRAS or EGFR mutations) the AKT signaling may switch from being a promoter to an inhibitor of cell migration, invasion and metastasis. This observation may have strong clinical implications for the development of inhibitors of this pathway for cancer treatment. Furthermore, we found that AKT1 blockade induced phosphorylation of Myristoylated alanine-rich C-kinase substrate (MARCKS) and elevation of Laminin subunit gamma-2 (LAMC2), which in turn inhibited AKT phosphorylation and promoted cell invasiveness. In contrast, MARCKS or LAMC2 knockdown abrogated the activities of migration and invasion induced by AKT1 inhibition. This study unravels an anti-metastatic role of AKT1 in NSCLC cells with KRAS or EGFR mutation, and provides mechanistic insights for the understanding of the potentially contrasting roles of AKT signaling in the regulation of cell invasiveness. Citation Format: Guanhua Rao, Mariaelena Pierobon, In-Kyu Kim, Wei-Hsun Hsu, Jianghong Deng, Yong-Wha Moon, Emanuel F. Petricoin, Yu-Wen Zhang, Yisong Wang, Giuseppe Giaccone. AKT1 signaling negatively regulates invasion and metastasis of non-small cell lung cancer cells carrying mutations in KRAS or EGFR [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 4893. doi:10.1158/1538-7445.AM2017-4893