Autophagy Inhibition Sensitizes Liver Kinase B1 (LKB1)‐Deficient Kras‐Driven Lung Tumors to MEK Inhibitor Trametinib

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 causes aggressive tumor growth 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 both 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 the KL TDCLs were much more 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 metabolomics 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 of HCQ and Trametinib. Similarly, we observed anti‐tumor synergistic effects of the combination treatment in KL allograft tumor growth. Our observations suggest that KL TDCLs resist to Trametinib treatment by upregulating autophagy to maintain energy homeostasis for cancer cell survival. Therefore, a combination therapy of autophagy and MEK inhibition could be a novel therapeutic strategy to specifically treat LKB1‐deficient NSCLC.Support or Funding InformationThis research has been supported by the research funds from NIH K22 CA190521 grant, American Cancer Society Early Investigator Pilot Award, Lung Cancer Research Foundation grant and startup funding from Rutgers Cancer Institute of New Jersey.