Inhibition of Autophagy and MEK Promotes Ferroptosis in Lkb1-Deficient Kras-Driven Lung Tumors

Abstract

Listen

Translate article

<b>Abstract ID 22421</b> <b>Poster Board 437</b> 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 and metastases. Unfortunately, standard treatment with RAS-RAF-MEK-ERK signaling pathway inhibitors has minimal therapeutic efficacy in LKB1-mutant KRAS-driven NSCLC. Thus, identifying a novel therapy for patients harboring co-mutations in LKB1 and KRAS is urgently needed. Autophagy degrades and recycles the building blocks for cancer cells to survive 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 <i>Atg7</i> dramatically impaired tumor initiation and tumor growth in <i>Kras^G12D/+</i>;<i>Lkb1^-/-</i> (<b>KL</b>) lung tumors.<i></i> This is in sharp contrast to <i>Lkb1</i> wild-type (WT) <i>(Kras^G12D/+;p53^-/-</i> (<b>KP</b>)<i>)</i> 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 MEK inhibitor Trametinib and found that the combination treatment displayed synergistic anti-proliferative effects in KL TDCLs compared to 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, or combination treatment and 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. In addition, the combination treatment significantly reduced mitochondrial membrane potential, basal respiration, and ATP production in KL TDCLs. In vivo studies using tumor allografts, genetically engineered mouse models (GEMMs), and patient-derived xenografts (PDXs) showed anti-tumor activity of the combination treatment on KL tumors, but not in KP tumors. Moreover, we found increased lipid peroxidation indicative of ferroptosis in KL TDCLs and KL PDX tumors with the combination treatment compared to the single agents. Finally, treatment with a ferroptosis inhibitor rescued the reduced KL allograft tumor growth caused by the combination treatment. Taken together, our observations indicate that autophagy upregulation in KL tumors causes resistance to Trametinib treatment by maintaining energy homeostasis for cell survival and inhibiting ferroptosis. Therefore, a combination of autophagy and MEK inhibition could be a novel therapeutic strategy to specifically treat LKB1-deficient KRAS-driven NSCLC<b>.</b> This research has been supported by New Jersey Commission on Cancer Research Predoctoral Fellowship, Steven Cox Scholarship, GO2 Foundation for Lung Cancer Research Award, American Cancer Society Research Scholar Award, and NIH-R01 grant.