Abstract 5710: Autophagy inhibition sensitizes Liver Kinase B1 (LKB1) - deficient Kras-driven lung tumors to MEK inhibitor Trametinib
Authors: Bhatt Vrushank Dharmesh , Khayati Khoosheh , Kong Jerry , Raju Akash , Hu Zhixian , Su Xiaoyang , Guo Jessie Yanxiang 
Published: September 2020

Abstract
Tumor suppressor liver kinase B1 (LKB1) activates 5'-adenosine monophosphate protein kinase (AMPK) and plays an essential role in maintaining energy homeostasis. LKB1 mutations are the third most frequent mutation detected in non-small cell lung cancer (NSCLC). Compared to p53 mutation, co-mutations in LKB1 with KRAS cause aggressive tumor growth, metastases and resistance to chemotherapy as well as immunotherapy. Thus, identifying a novel target to improve LKB1-deficient Kras-driven NSCLC treatment is urgently needed. Our previous work demonstrates that autophagy inhibition is synthetically lethal in KrasG12D/+;Lkb1−/− (KL) mediated tumorigenesis; in contrast to intact autophagy KL lung tumors, loss of an autophagy-essential gene Atg7 dramatically impaired tumor initiation and tumor growth. This is in sharp contrast to wild-type (WT) Lkb1 (KrasG12D/+;p53−/− (KP)) tumors that are less sensitive to autophagy gene ablation. These observations indicate that LKB1 mutations predispose KRAS NSCLC to autophagy inhibition and that LKB1 mutations could be explored as a predictive biomarker for precision lung cancer therapy. 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 Lkb1-WT 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 increased sensitivity of KL TDCLs to Trametinib by autophagy ablation, we performed metabolomic profiling of KL TDCLs with Trametinib, HCQ alone or in combination treatment. We found that the levels of several glycolytic and TCA cycle intermediates, as well as amino acids, were significantly upregulated upon treatment with Trametinib, which were significantly reduced by the combined treatment with HCQ and trametinib. Moreover, Trametinib treatment led to an increased level of ATP, which was decreased by the combination treatment. Similarly, we observed anti-tumor synergistic effects of the combination treatment in KL allograft tumor growth. In addition, metastases of KL TDCLs to the lung was reduced by the combination treatment compared to the single agents. We further found that in KRAS-mutant human lung cancer cell lines, LKB1-mutant cells were much sensitive to the combination treatment than LKB1-WT cells. Our observations suggest that KL TDCLs and KL human lung cancer cells resist to Trametinib treatment by upregulating autophagy to maintain energy homeostasis for survival. Therefore, combination therapy of autophagy and MEK inhibition could be a novel therapeutic strategy to specifically treat LKB1-deficient NSCLC.
Citation Format: Vrushank Dharmesh Bhatt, Khoosheh Khayati, Jerry Kong, Akash Raju, Zhixian Hu, Xiaoyang Su, Jessie Yanxiang Guo. Autophagy inhibition sensitizes Liver Kinase B1 (LKB1) - deficient Kras-driven lung tumors to MEK inhibitor Trametinib [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5710.