CRM1-dependent p53 nuclear accumulation in lung lesions of a bitransgenic mouse lung tumor model

The p53 tumor suppressor gene plays an essential role in tumorigenesis, and the chromosomal region maintenance 1 (CRM1) has been suggested to export p53 protein from the nucleus to the cytoplasm. The objectives of the present study were to evaluate p53 expression and subcellular localization as well as CRM1 expression using immunohistochemistry in our established bitransgenic mouse lung tumor model. In this model, expression of the mutant human Ki-ras(G12C) allele was regulated in a doxycycline (DOX)-inducible, lung-specific manner. Following treatment with curcumin, we found that although overall p53 expression levels were not significantly changed among the three groups, lung lesions in mice treated with DOX alone had the highest proportion of N > C (nucleus predominant) p53 staining (46 +/- 7%), followed by lung lesions in mice co-treated with DOX and curcumin (31 +/- 12%) and controls (17 +/- 4%). CRM1 expression was dramatically inhibited in lung lesions in mice treated with DOX (0 +/- 0) as compared to controls (90 +/- 17, P=0.001), and could be partially reversed after curcumin treatment (47 +/- 21, P=0.028, DOX vs. DOX+curcumin). Collectively, the results from this study demonstrated that p53 accumulated in the nucleus in lung lesions in mice expressing the mutant Ki-ras(G12C) transgene as a result of down-regulation of CRM1. Furthermore, these alterations could be partially reversed by curcumin treatment. p53 subcellular localization resulting from CRM1 alterations may play an important role in lung tumorigenesis.