Interestingly, gene expression of osteopontin, a potential marker of the development of lung diseases including fibrosis and cancer, had begun to increase by 1 and 2 months post-exposure in the Gr20 and Gr5 high dose groups; however, no histopathological markers of disease were present at 2 months and protein levels of MMP-9 and TIMP-2, although elevated when compared to the DM group, were decreasing over time. This evidence concerns the gene MMP9 and cancer.