Abstract 88: Autophagy inhibition sensitizes liver kinase b1 (LKB1)-deficient kras-driven lung tumors to MEK inhibitor trametinib
Authors: Bhatt Vrushank Dharmesh , Lan Taijin , Wang Wenping , Khayati Khoosheh , Cararo-Lopes Eduardo , Wang Jianming , Kong Jerry , Raju Akash , Luo Xuefei , Hu Wenwei , Su Xiaoyang , White Eileen , Guo Jessie Yanxiang 
Published: July 2021

Abstract
Tumor suppressor Liver Kinase B1 (LKB1) activates 5'-adenosine monophosphate protein kinase (AMPK) and maintains energy homeostasis in response to energy crises. LKB1 and KRAS are the third most frequent co-mutations detected in non-small cell lung cancer (NSCLC), causing aggressive tumor growth, metastases, and resistance to standard chemotherapy as well as immunotherapy. Thus, identifying a novel treatment for patients harboring co-mutations in LKB1 and KRAS is urgently needed. Autophagy degrades and recycles the building blocks for cancer cells to survival metabolic challenges. Using genetically engineered mouse models (GEMMs), we have previously demonstrated that autophagy compensates for Lkb1 loss for KRAS-driven lung tumorigenesis; loss of an autophagy-essential gene Atg7 dramatically impaired tumor initiation and tumor growth in KrasG12D/+;Lkb1-/- (KL) lung tumors. This is in sharp contrast to Lkb1 wild-type (WT) (KrasG12D/+;p53-/- (KP)) tumors that are less sensitive to autophagy gene ablation. To further value our discoveries in clinical translational ability, we treated mouse lung tumor-derived cell lines (TDCLs) with FDA-approved autophagy inhibitor hydroxychloroquine (HCQ) and found that KL TDCLs were much sensitive to HCQ-induced cell death compared with KP TDCLs. Furthermore, a combination treatment of HCQ with mitogen-activated protein kinase kinase (MAPKK or MEK) inhibitor Trametinib showed synergistic anti-proliferative effects in KL TDCLs, but not in KP TDCLs. To elucidate the underlying mechanism of the increased sensitivity of KL TDCLs to Trametinib by autophagy ablation, we performed metabolomic profiling of KL TDCLs with Trametinib, HCQ, or combination treatment. We found that several glycolytic and TCA cycle intermediates, amino acids, and ATP levels were significantly upregulated upon treatment with Trametinib, which were significantly reduced by the combination treatment. Also, the combination treatment significantly reduced the mitochondrial membrane potential, basal respiration, and ATP production in the KL TDCLs compared with the single agents. However, these effects were not observed in KP TDCLs. Similarly, we found that LKB1-mutant human lung cancer cell lines were much more sensitive to the combination treatment than LKB1 WT cells. Finally, we performed in vivo tumor assay using allograft mouse models and GEMMs to validate our in vitro observations. We found anti-tumor synergistic effects of the combination treatment in KL tumor growth, with no such effect in KP tumor growth. Taken together, our observation suggests that autophagy upregulation in Lkb1-deficient tumors cause resistance to Trametinib treatment by maintaining energy homeostasis for cell survival. Therefore, a combination of autophagy and MEK inhibition could be a novel therapeutic strategy to specifically treat LKB1-deficient NSCLC.
Citation Format: Vrushank Dharmesh Bhatt, Taijin Lan, Wenping Wang, Khoosheh Khayati, Eduardo Cararo-Lopes, Jianming Wang, Jerry Kong, Akash Raju, Xuefei Luo, Wenwei Hu, Xiaoyang Su, Eileen White, Jessie Yanxiang Guo. Autophagy inhibition sensitizes liver kinase b1 (LKB1)-deficient kras-driven lung tumors to MEK inhibitor trametinib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 88.