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The N-nitroso-trischloroethylurea (NTCU)-induced mouse model of squamous lung carcinoma recapitulates human disease from premalignant dysplasia through invasive tumors, making it suitable for preclinical chemoprevention drug testing. Pioglitazone is a peroxisome proliferator-activated receptor γ (PPARγ) agonist shown to prevent lung tumors in preclinical models. We investigated pioglitazone's effect on lesion development and markers of potential preventive mechanisms in the NTCU model. Female FVB/N mice were exposed to vehicle, NTCU or NTCU + oral pioglitazone for 32 weeks. NTCU induces the appearance of basal cells in murine airways while decreasing/changing their epithelial cell makeup, resulting in development of bronchial dysplasia. Hamp;E and keratin 5 (KRT5) staining were used to detect and grade squamous lesions in formalin fixed lungs. mRNA expression of epithelial to mesenchymal transition (EMT) markers and basal cell markers were measured by qPCR. Dysplasia persistence markers desmoglein 3 and polo like kinase 1 were measured by immunohistochemistry. Basal cell markers KRT14 and p63, club cell specific protein and ciliated cell marker acetylated tubulin were measured by immunofluorescence. Pioglitazone treatment significantly reduced squamous lesions and the presence of airway basal cells, along with increasing normal epithelial cells in the airways of NTCU-exposed mice. Pioglitazone also significantly influenced EMT gene expression to promote a more epithelial, and less mesenchymal, phenotype. Pioglitazone reduced the presence of squamous dysplasia and maintained normal airway cell composition. This work increases the knowledge of mechanistic pathways in PPARγ agonism for lung cancer interception and provides a basis for further investigation to advance this chemoprevention strategy.

Silibinin inhibits mouse lung tumorigenesis in part by targeting tumor microenvironment. Tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) can be pro- or anti-tumorigenic, but in lung cancer cell lines they induce pro-inflammatory enzymes cyclooxygenase 2 (COX2) and inducible nitric oxide synthase (iNOS). Accordingly, here we examined mechanism of silibinin action on TNF-α + IFN-γ (hereafter referred as cytokine mixture) elicited signaling in tumor-derived mouse lung epithelial LM2 cells. Both signal transducers and activators of the transcription (STAT)3 (tyr705 and ser727) and STAT1 (tyr701) were activated within 15 min of cytokine mixture exposure, while STAT1 (ser727) activated after 3 h. Cytokine mixture also activated Erk1/2 and caused an increase in both COX2 and iNOS levels. Pretreatment of cells with a MEK, NF-κB, and/or epidermal growth factor receptor (EGFR) inhibitor inhibited cytokine mixture-induced activation of Erk1/2, NF-κB, or EGFR, respectively, and strongly decreased phosphorylation of STAT3 and STAT1 and expression of COX2 and iNOS. Also, janus family kinases (JAK)1 and JAK2 inhibitors specifically decreased cytokine-induced iNOS expression, suggesting possible roles of JAK1, JAK2, Erk1/2, NF-κB, and EGFR in cytokine mixture-caused induction of COX2 and iNOS expression via STAT3/STAT1 activation in LM2 cells. Importantly, silibinin pretreatment inhibited cytokine mixture-induced phosphorylation of STAT3, STAT1, and Erk1/2, NF-κB-DNA binding, and expression of COX2, iNOS, matrix metalloproteinases (MMP)2, and MMP9, which was mediated through impairment of STAT3 and STAT1 nuclear localization. Silibinin also inhibited cytokine mixture-induced migration of LM2 cells. Together, we showed that STAT3 and STAT1 could be valuable chemopreventive and therapeutic targets within the lung tumor microenvironment in addition to being targets within tumor itself, and that silibinin inhibits their activation as a plausible mechanism of its efficacy against lung cancer. © 2011 Wiley Periodicals, Inc.

Pre-mRNA processing is an important mechanism for globally modifying cellular protein composition during tumorigenesis. To understand this process during lung cancer, expression of two key pre-mRNA alternative splicing factors was compared in a mouse model of early lung carcinogenesis and during regenerative growth following reversible lung injury. Heterogeneous nuclear ribonucleoprotein (hnRNP) A1 and alternative splicing factor/splicing factor 2 (ASF/SF2) act antagonistically to modulate splice site selection. Both hnRNP A1 and ASF/SF2 contents rose in adenomas and during injury-induced hyperplasia compared to control lungs, as measured by immunoblotting. While both proteins increased similarly during compensatory hyperplasia, hnRNP A1 increased to a much greater extent than ASF/SF2 in tumors, resulting in a 6-fold increase of the hnRNP A1 to ASF/SF2 ratio. Immunohistochemical analysis showed that hnRNP A1 localized exclusively within tumor nuclei, while ASF/SF2 appeared in cytoplasm and/or nuclei, depending on the growth pattern of the tumor cells. We also demonstrated cancer-associated changes in the pre-mRNA alternative splicing of CD44, a membrane glycoprotein involved in cell-cell and cell-extracellular matrix interactions. hnRNP A1 and ASF/SF2 expression is thus differentially altered in neoplastic lung cells by mechanisms that do not strictly arise from increased cell division. These changes are influenced by tumor histology and may be associated with production of variant CD44 mRNA isoforms. © 2004 Wiley-Liss, Inc.

Gap junctional intercellular communication (GJIC) and connexin expression are frequently decreased in neoplasia and may contribute to defective growth control and loss of differentiated functions. GJIC, in E9 mouse lung carcinoma cells and WB-aB1 neoplastic rat liver epithelial cells, was elevated by forced expression of the gap junction proteins, connexin43 (Cx43) and connexin32 (Cx32), respectively. Transfection of Cx43 into E9 cells increased fluorescent dye-coupling in the transfected clones, E9-2 and E9-3, to levels comparable to the nontransformed sibling cell line, E10, from which E9 cells originated. Transduction of Cx32 into WB-aB1 cells also increased dye-coupling in the clone, WB-a/32-10, to a level that was comparable to the nontransformed sibling cell line, WB-F344. The cell cycle distribution was also affected as a result of forced connexin expression. The percentage of cells in G1-phase increased and the percentage in S-phase decreased in E9-2 and WB-a/32-10 cells as compared to E9 and WB-aB1 cells. Concomitantly, these cells exhibited changes in G1-phase cell cycle regulators. E9-2 and WB-a/32-10 cells expressed significantly less cyclin D1 and more p27kip-1 protein than E9 and WB-aB1 cells. Other growth-related properties (expression of platelet-derived growth factor receptor-β, epidermal growth factor receptor, protein kinase C-α, protein kinase A regulatory subunit-Iα, and production of nitric oxide in response to a cocktail of pro-inflammatory cytokines) were minimally altered or unaffected. Thus, enhancement of connexin expression and GJIC in neoplastic mouse lung and rat liver epithelial cells restored G1 growth control. This was associated with decreased expression of cyclin D1 and increased expression of p27kip-1, but not with changes in other growth-related functions. J. Cell. Biochem. 79:347–354, 2000. © 2000 Wiley-Liss, Inc.

In their study of the linear stability limits for free convection in layers of porous media or packed beds with throughflow, others found that throughflow was generally stabilizing, but there was an exception. In the case of flow toward a porous boundary, they found that the numerically calculated Rayleigh-Darcy number initially decreased and went through a minimum as the appropriate Peclet number increased from zero. It was stated that the origin of the minimum was not completely understood, but others had eliminated numerical inaccuracy as a possible cause. Thus a small amount of throughflow can have a destabilizing effect in at least one situation. The primary purpose of this note is to explain this effect. The opportunity is taken to provide some supplementary material.

Dans ce modele, on suppose qu'un milieu poreux, a l'interieur duquel la loi de Darcy est applicable, occupe toute la colonne a l'exception d'une couche mince d'epaisseur uniforme adjacente a la paroi