ABSTRACT: Purpose: Chronic pulmonary inflammation in the form of chronic obstructive pulmonary disease (COPD) has been consistently shown to increase the risk of lung cancer. Therefore, identification of chemopreventive agents with anti-inflammatory effects, in addition to antiproliferative and apoptotic activities, is indispensable. Recently, we found that combinations of silibinin (Sil) and indole-3-carbinol (I3C) significantly inhibited lung tumorigenesis induced by 4-(methylnitro-samino)-1-(3-pyridyl)-1-butanone (NNK) and enhanced by chronic treatment with the inflammatory agent lipopolysaccharide (LPS). In this study, we described gene expression profiling of lung tissues using RNA-seq to determine the gene expression signature in inflammation-driven lung tumors and modulation of this signature by the chemopreventive agents Sil and I3C. Methods: Total RNA extracted from lung tissues of control and treated mice were processed for mRNA sequencing, in triplicate, using Illumina HiSeq 2000. The sequence reads that passed quality filters were analyzed for transcript abundance at the gene level using CLC Bio Genomics Workbench and differential gene expression analysis was performed using the built-in Empirical Analysis of Differential Gene Expression (DGE) based on 'Exact Test' method. qRT–PCR validation was performed using SYBR Green assays. Results and conclusions: We found that 330, 2,957, and 1,143 genes were differentially regulated in mice treated with NNK, LPS, and NNK + LPS, respectively. The expression of inflammation-and immunity-related genes was significantly more deregulated in lung tissues of mice treated with LPS alone compared to mice treated with NNK + LPS. Among 1,143 genes differentially regulated in the NNK + LPS group, the expression of 162 genes and associated signaling pathways were significantly modulated by I3C and/or Sil + I3C. These genes include cytokines, chemokines, and genes with a well-established role in inflammation and/or tumorigenesis such as c-ros oncogene 1 (Ros1), the EGFR ligands amphiregulin and epiregulin, Cyp1a1, and the circadian rhythm genes Arntl, and Npas2. To our knowledge, this is the first report that provides insight into genes that are differentially expressed during inflammation-driven lung tumorigenesis and the modulation of these genes by chemopreventive agents.
