Abstract A30: Gene regulatory mechanisms governing invasive mucinous adenocarcinoma of the lung (IMA)

Abstract

Abstract Background: Invasive mucinous adenocarcinoma of the lung (IMA) comprises 5-10% of lung adenocarcinoma. IMA is pathologically characterized as lung tumor cells with goblet cell morphology containing abundant intracytoplasmic mucin. Recent advances using next-generation sequencing technology revealed driver oncogenes (e.g., KRAS mutation and NRG1 fusions) and a gene expression signature (e.g., NKX2-1 negative and SPDEF positive) inducing IMA. However, the genetic mechanism governing the pathogenesis of IMA is not fully understood. Here, we report the mechanism of the gene regulatory network regulating mucins and immune checkpoints in IMA. Methods: Using lentiviral vectors expressing the anti-mucous transcription factor NKX2-1 (also known as TTF-1) and the pro-mucous transcription factor SPDEF, we assessed their functions in regulating the expression of mucins and immune checkpoints in multiple lung cancer cell lines. Using ChIP-seq datasets, we further identified genome-wide binding sites of NKX2-1 and SPDEF in A549 lung carcinoma cells that carry a KRAS mutation and produce mucins. We further deleted such binding sites in the genome using CRISPR/Cas9 to assess the function of the sites. Results: NKX2-1 influenced the expression of immune checkpoints, including PD-L1, and mucin-related genes, including MUC5AC and SPDEF. Notably, NKX2-1 bound to the same noncoding region upstream of MUC5AC as SPDEF. The genomic deletion study using CRISPR/Cas9 indicated that both NKX2-1 and SPDEF bound to the enhancer region (but not the silencer region) of MUC5AC, suggesting that NKX2-1 suppresses mucin gene expression by blocking the activity of the enhancer region but not by recruiting a co-repressor complex such as HDAC to the region. Conclusion: Transcription factors NKX2-1 and SPDEF function as yin and yang to affect the pathogenesis of IMA. Citation Format: Minzhe Guo, Koichi Tomoshige, Iris Fink-Baldauf, Yutaka Maeda. Gene regulatory mechanisms governing invasive mucinous adenocarcinoma of the lung (IMA) [abstract]. In: Proceedings of the Fifth AACR-IASLC International Joint Conference: Lung Cancer Translational Science from the Bench to the Clinic; Jan 8-11, 2018; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(17_Suppl):Abstract nr A30.