LKB1 and KEAP1/NRF2 pathways cooperatively promote glutamine dependence and vulnerability to glutaminase inhibitors in KRAS-mutant lung adenocarcinoma

KRAS is the most commonly mutated oncogenic driver in non-small cell lung cancer (NSCLC) and other solid tumors. Recently we conducted an integrative analysis and found three major subgroups of KRAS-mutated cancer defined by co-occurring genomic events with distinct biology, molecular vulnerabilities, and therapeutic sensitivities. One of these genes, the serine/threonine kinase STK11 (LKB1), represents the second most commonly altered tumor suppressor in NSCLC and there are currently no treatment strategies tailored for LKB1-deficient NSCLC. KRAS-mutant/LKB1-deficient (KL) tumors are characterized by high co-occurrence of KEAP1 mutational inactivation. Inactivation of KEAP1 protects cells against REDOX stress via upregulation of NRF2 target genes, in part by production of glutathione. We evaluated the effects of blocking glutamine metabolism using an isogenic series of NSCLC cell lines harboring mutations in STK11 and KEAP1. Through sequential silencing or overexpression of LKB1, KEAP1, or NRF2 we demonstrated that glutaminase inhibitors (GLSi) can block cell proliferation while increasing energetic and REDOX stress specifically in LKB1 deficient cells with hyperactivation of the KEAP1/NRF2 pathway driven by KEAP1 mutations (KLK subtype). In KLK models, overexpression of LKB1 or KEAP1 partially reduced GLSi sensitivity, while siRNA-mediated down-regulation of NRF2 showed a similar effect. Furthermore, the combination of LKB1 add back coupled with down-regulation of NRF2 conferred even greater resistance to GLSi. To confirm the LKB1/KEAP1-driven response to GLSi, we performed in vivo experiments examining the response of subcutaneous xenografts of an A549 isogenic series; A549 (KLK), A549 LKB1 add back (KK) or A549 KEAP1 add back (KL); to GLS inhibition. These experiments demonstrated that GLSi impaired tumor growth in A549 (KLK) tumors, exhibiting significant statistical differences compared with the vehicle group from 18 days of treatment. Conversely, GLS inhibition did not significantly affect the growth of A549/LKB1 (KK) or A549/KEAP1 (KL) tumors. Collectively, our data indicate that in KLK tumors both pathways, LKB1 and KEAP1/NRF2, cooperatively drive a glutamine-addicted metabolic program, making KLK tumors selectively vulnerable to GLSi treatment. These findings have immediate clinical implications and support the future clinical testing of GLS inhibitors in KLK NSCLC. Citation Format: Ana Galan-Cobo, Piyada Sitthideatphaiboon, Xiao Qu, Jeffrey J. Kovacs, Alissa Poteete, Pan Tong, Sungnam Cho, Varsha V. Gandhi, Ferdinandos Skoulidis, Jing Wang, Timothy P. Heffernan, John V. Heymach. LKB1 and KEAP1/NRF2 pathways cooperatively promote glutamine dependence and vulnerability to glutaminase inhibitors in KRAS-mutant lung adenocarcinoma [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 2408.