mRNA expression of Mmp9, Egfr and Hmox1 (tumor progression), Timp1 and Timp2 (inhibitors of metalloproteinases) and Hif1α (hypoxia) evaluated in lung homogenates was significantly augmented in LLC-challenged Igf1rfl/fl mice, remaining unaltered in CreERT2 mice. This evidence concerns the gene MMP9 and neoplasm.