Abstract 3507: LKB1 deficiency and KEAP1/NRF2 pathway alterations as biomarkers of response for ATR and ATM inhibitors and other inhibitors of DNA damage response (DDR) in NSCLC
Authors: Galan-Cobo Ana , Pottetee Alissa , Heymach John V. 
Published: August 2019

Abstract
The serine/threonine kinase STK11 (LKB1) is the second most commonly altered tumor suppressor in NSCLC; however, there are currently no effective treatment strategies for this subset of tumors. KRAS-mutant LKB1 deficient tumors often also have alterations in KEAP1 or NRF2 gene, which activate the NRF2 pathway known to be involved in antioxidant response.
Inhibitors of ATM and ATR, two key proteins in the DNA damage response (DDR) pathway, are currently undergoing clinical testing but there are no biomarkers established for identifying which subgroups of patients are more likely to benefit from treatment. Here we have identified that alterations of LKB1, and the KEAP1/NRF2 pathway, are associated with enhanced response to ATM and ATR inhibitors (AMTi and ATRi) and other inhibitors of the DDR and may be useful biomarkers for predicting therapeutic response.
To investigate the impact of LKB1 loss and KEAP1/NRF2 pathway activation on response to DDR inhibitors (DDRi), we first tested the in vitro activity of ATM inhibitor in NSCLC murine cell lines with or without knock out of LKB1 and/or KEAP1. In these cells, the loss of LKB1 and/or KEAP1 significantly sensitize cells to ATMi AZD0156. In addition, we evaluated the activity of the ATRi AZD6738 in NSCLC cells with or without knockout of LKB1 and/or KEAP1. Cells deficient in LKB1 (KL) and/or KEAP1 (KLK/KK) were more sensitive to AZD0156 and AZD6738 than cells with intact LKB1 and KEAP1. Next, we investigated whether the activity of ATR and ATM inhibitors in KL, KK or KLK tumor cells could be enhanced by the addition of a PARP inhibitor (Olaparib). Although all NSCLC cells were resistant to the PARP inhibitor olaparib when used as a single agent, treatment of LKB1, KEAP1 or LKB1 plus KEAP1 deficient cells with the combination of olaparib plus ATM or ATR inhibitors significantly enhanced the antitumor cell activity of ATM or ATR inhibitors alone. We confirmed these data in an additional panel of LKB1 deficient NSCLC human cell lines (A549, H460 and H2030) treated with a broad spectrum of ATR and ATM inhibitors. In all human cell lines re-expression of LKB1 clearly reduced the sensitivity to ATR inhibition. LKB1 lost was also associated with sensitivity to PARP and ATM inhibitor, although these effects seemed to be less significant compared with ATR inhibitors.
Tumors with LKB1 deficiency or KEAP/NRF2 mutations are typically resistant to standard chemotherapy drugs and immunotherapy. Our data indicate that LKB1 and KEAP1/NRF2 loss significantly enhance the sensitivity to ATR and ATM inhibitors in vitro. Thus, we have identified that NSCLC tumors bearing STK11 or KEAP1/NRF2 mutations are highly sensitive to ATM or ATR inhibitors and that genes may serve as biomarkers for selecting appropriate patients for treatment alone or in combination treatments, such as PARPi or immunotherapy.
Citation Format: Ana Galan-Cobo, Alissa Pottetee, John V. Heymach. LKB1 deficiency and KEAP1/NRF2 pathway alterations as biomarkers of response for ATR and ATM inhibitors and other inhibitors of DNA damage response (DDR) in NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3507.