Global Differential Gene Expression Analysis of Spontaneous Lung Tumors in B6C3F1 Mice: Comparison to Human Non-Small Cell Lung Cancer

Introduction: Lung cancer is the leading cause of cancer-related death in people. There are several chemically induced and genetically modified mouse models used to study lung cancer. We hypothesized that spontaneous murine (B6C3F1) lung tumors can serve as a model to study human non-small cell lung cancer (NSCLC). Methods: RNA was extracted from untreated 2-year-old B6C3F1 mouse spontaneous lung (SL) tumors and age-matched normal lung tissue from a chronic inhalation NTP study. Global gene expression analysis was performed using Affymetrix Mouse Genome 430 2.0 GeneChip® arrays. After data normalization, for each probe set, pairwise comparisons between groups were made using a bootstrap t-test while controlling the mixed directional false discovery rate (mdFDR) to generate a differential gene expression list. IPA, KEGG, and EASE software tools were used to evaluate the overrepresented cancer genes and pathways. Results: MAPK and TGF-beta pathways were overrepresented within the dataset. Almost all of the validated genes by quantitative real time RT-PCR had comparable directional fold changes with the microarray data. The candidate oncogenes included Kras, Braf, Raf1, Id2, Hmga1, Cks1b, and Foxf1. The candidate tumor suppressor genes included Rb1, Cdkn2a, Hnf4a, Tcf21, Ptprd, Hpgd, Hopx, Ogn, Id4, Hoxa5, Smad6, Smad7, Zbtb16, Cyr61, Dusp4, and Ifi16. In addition, several genes important in lung development were also differentially expressed, such as Smad6, Hopx, Sox4, Sox9 and Mycn. Conclusion: In this study, we have demonstrated that several cancer genes and signaling pathways relevant for human NSCLC were similarly altered in spontaneous murine lung tumors. Six spontaneous lung tumors and six normal lungs (as controls) from 2-year-old B6C3F1 mice.