MAPK regulation of an innate immune response in KRAS-mutant lung adenocarcinoma.

Mutations in the KRAS oncogene are frequent in lung adenocarcinomas (LUADs). Unfortunately, KRAS lacks a pharmacologically available inhibitor for precision oncology. Immunotherapies have recently become available and are now FDA approved for LUAD, although only a subset of patients show clinical benefit. Recent work has unveiled biomarkers of immunotherapy response and include interferon γ (IFNγ) and T-cell inflamed gene signatures, suggesting that active IFN signaling within the tumor microenvironment (TME) and infiltration of antitumor T-cells are necessary for response. Thus, strategies that increase T-cell inflammation within LUAD are predicted to broaden immunotherapy response. Using human and murine KRAS-mutant LUAD cell lines, we demonstrated variable transcriptional induction of an innate immune response after 1-2-day treatment with the MEK inhibitor, trametinib. In particular, murine lung cancer cell lines 832B and LKR10 demonstrated induction of CXCL10 transcript, an innate immune chemotactic factor for effector T cells and natural killer (NK) cells. This variable induction was also seen at the protein level with CXCL10 protein increasing 8- and 4-fold, in 832B and LKR10 respectively, after a 3-day treatment. Human KRAS-mutant LUAD cell line, H358, exhibited a 17-fold induction in CXCL10 protein secretion following a 3-day treatment with trametinib. The mechanism(s) by which MAPK inhibition leads to induction of innate immune signaling remains ill defined. IKK-16, an inhibitor of IKKα/β and downstream NF-kB signaling, but not the JAK inhibitor, ruxolitinib, blocked trametinib-induced CXCL10 secretion in H358 cells. While the data support a central role for NF-kB signaling in this response, the complexity of innate immune signaling and IKK-NF-kB pathways prevents their full dissection with traditional candidate-based approaches. Therefore, we have initiated a functional genomics approach using CRISPR/Cas9-mediated tagging of the CXCL10gene in human lung cancer cell lines. While H358 cells are in process, we successfully generated EGFR mutant PC9 cells that bear GFP-tagged CXC10 and exhibit strong induction of CXCL10-GFP when treated with the 3rd-generation EGFR inhibitor, AZD9291. These CXCL10-GFP tagged cell lines will be deployed in functional genomics experiments to define in an unbiased manner signal pathway and transcription factor components that mediate oncogene-targeted drug-induced CXCL10 induction. A full elucidation of the mechanism by which oncogene pathways suppress innate immune pathways and CXCL10 expression may highlight novel ways in which to enhance antitumor inflammation and increase the depth of the therapeutic response to oncogene-targeted drugs. Citation Format: Daniel Sisler, Sean Korpela, Natalia Gurule, Trista Hinz, Lindsay Marek, Bonnie Bullock, Howard Li, Molishree Joshi, Colin Sempeck, Raphael Nemenoff, Lynn Heasley. MAPK regulation of an innate immune response in KRAS-mutant lung adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr B51.