Abstract 5492: Inhibition of ERK MAPK signaling increases pancreatic cancer dependency on autophagy

Abstract

Abstract Pancreatic ductal adenocarcinoma (PDAC) cell growth is dependent on altered biochemical and cellular activities that facilitate increased metabolic dependencies. We determined the role of mutationally activated KRAS, found in ~95% of PDAC, in supporting autophagy. Surprisingly, acute KRAS suppression, which blocks proliferation, was associated with increased rather than decreased autophagic flux. Similarly, KRAS transformation of immortalized human pancreatic epithelial cells showed decreased autophagic flux. Pharmacologic inhibition of ERK MAPK phenocopied the genetic silencing of KRAS and also increased autophagic flux. Addressing a mechanism for ERK suppression increased autophagy, we found increased AMPK activity, decreased mTOR activity, and increased expression of autophagic proteins. We speculated that increased autophagy may be a compensatory mechanism caused by the loss of KRAS- and ERK-dependent metabolic processes. To address this possibility, we performed RNA-seq analyses to monitor gene expression changes in response to ERK inhibition. We observed increased transcription of genes responsible for the metabolic processes of autophagy and β-oxidation, with concurrent decreased transcription of glycolysis and mitochondrial-associated genes. These changes were validated in metabolomic analyses following either genetic silencing of KRAS or ERK inhibition. Thus, the loss of ERK-driven metabolic processes may induce compensatory mechanisms to increase autophagy. We then addressed whether ERK inhibition increased PDAC dependence on autophagy. Supporting this possibility, we found that cotreatment with the autophagy inhibitor chloroquine synergistically enhanced ERK inhibitor mediated antiproliferative activity. Similarly, genetic or pharmacologic inhibition of specific regulators of autophagy also enhanced ERK inhibitor activity. We conclude that concurrent suppression of multiple metabolic processes, to block compensatory rebound activities, will be needed for effective PDAC treatment. Citation Format: Kirsten Bryant, Sen Peng, Andrey Tikunov, Mariaelena Pierobon, Venugopal Gunda, Garima Tomar, Pankaj Singh, Emanuel Petricoin, Jeffrey Macdonald, Nhan Tran, Alec Kimmelman, Channing Der. Inhibition of ERK MAPK signaling increases pancreatic cancer dependency on autophagy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5492.