Fibronectin is distinctly downregulated in murine mammary adenocarcinoma cells with high metastatic potential.

In the present work we used a murine mammary cancer model of two related adenocarcinomas with different lung metastasizing abilities, to compare their global gene expression profiles. Clontech Atlas mouse cDNA microarrays of primary cultured tumor cells were employed to identify genes that are modulated in the more metastatic variant MM3 relative to its parental tumor M3. A total of 88 from 1,176 genes were differentially expressed in MM3 primary cultures, most of them (n=86) were upregulated. Genes were grouped according to their functions as associated with signal transduction and transcription regulation (e.g. Stat1 and Zfp 92), with cell adhesion and motility (cadherin 1, fibronectin), with invasion and angiogenesis (uPA, 72 kDa MMP2), with the regulation of cell proliferation and cell death (cyclins G and A2, TNF), and also included growth factors and receptors, oncogenes and tumor suppressors genes (p107, TGFbeta2, TBR-I, PDGFR). Only 2 genes, TTF1 and fibronectin (FN), showed a significant downregulation. Notably FN expression, loss of which has been associated with a malignant phenotype, was reduced about 19-fold in the more metastatic MM3 cells. Previously known differences in expression patterns associated with the metastatic capacity of MM3 and M3 adenocarcinomas, including downregulation of FN or upregulated expression of TGFbeta and proteases, were confirmed by the array data. The fact that FN was one of the only two genes significantly down-regulated out of the 1,176 genes analyzed stresses the hypothesis that FN may behave as an important metastasis suppressor gene in mammary cancer.

[Different enzymatic activities recruitment by specific domains of TIF2 are involved in NF-kappaB transactivation]. / La actividad transcripcional de NF-kappaB es diferencialmente regulada por dominios específicos del coactivador TIF2.

We have previously shown that nuclear receptor coactivator overexpression significantly enhanced NF-kappaB activity in a dose response manner. We studied the mechanism by which TIF2 regulates NF-kappaB activity. We determined that: 1) the p38 specific inhibitor reduces 50% NF-kappaB transcriptional activity, even in cells that overexpress distinct TIF2 deletions; 2) there is a physical interaction between TIF2 and p38 and RelA determined through in vitro translated protein binding assays; 3) TIF2 is a p38 substrate; 4) there is a physical interaction between TIF2 and IKK in TNF-alpha 20 ng/ml stimulated or not HEK 293 cell protein extract, and IkappaB only in basal conditions, determined by binding pull down assays. This NF-kappaB complex regulates its activity and targets gene expression in a determined physiologic context depending on the coactivator complex content.