Figure 5 shown that expression new product of a mutated form of the Ras protein in BxPc 3 cells, which are wild type for ras, resulted in decreased p8 mRNA concentration and protein level suggesting that the activated ras inhibits p8 expression. Figure 6 shows that overexpression of Raf, but not of Raf301, and of ERK also inhibited the expression of the p8 CAT construct in Panc 1 as well as in BxPc 3. Finally, the MEK1/2 specific inhibitor U0126 activated p8 mRNA expression in pancreatic cells whether they carry mutated ras or wild type. Inhibitors,Modulators,Libraries Similar results were observed when expression of the p8 protein was monitored by Western blotting. Activation of the Inhibitors,Modulators,Libraries JNK pathway down regulates p8 expression in pancreatic cancer cells c Jun NH2 terminal kinase is another major MAPK pathway which converts extracellular signals into expres sion of specific target genes through phosphorylation and activation of transcription factors.

JNK activation has been implicated in various, often opposite cellular responses, such as cell proliferation, transformation and apoptosis. As shown in Figure 8, overexpression of JNK down regu lates the gene reporter activity of the p8 CAT construct in Panc 1 cells. Similar results were found in BxPc 3 cells. Treatment of Inhibitors,Modulators,Libraries these cells with the JNK specific inhibitor SP600125 up regulates expression of the p8 mRNA and p8 protein. These results show that the JNK pathway is involved in the regulation of p8 expression. The p38 pathway up regulates p8 expression in pancreatic cancer cells The p38 signal transduction pathway also plays an essen tial role in regulating several cell functions including growth, response to inflammation, differentiation and apoptosis.

In fact, in pancreatic cancer cells, p38 is a strong inhibitor of proliferation contrary to the Ras Raf MEK ERK and JNK pathways. We therefore analyzed the putative role of the p38 pathway in regulat ing p8 expression in pancreatic cancer cells. Figure 10 shows that over expression of the plasmid encoding Inhibitors,Modulators,Libraries p38 significantly increases p8 CAT activity in Panc 1 as Inhibitors,Modulators,Libraries well as in BxPc 3 cells. Then, cells were treated with SB203580, a specific inhibitor of p38, and p8 expression was tran Wortmannin PI3K inhibitor measured. p8 mRNA as well as the encoded protein were down regulated after inhibition of the p38 activity. These results indicate that the p38 pathway is a posi tive regulator of p8 expression in pancreatic cancer cells. TGF 1 up regulates p8 expression in pancreatic cancer cells The most prominent biological activity of TGF 1 is its potent inhibition of cell growth in a wide variety of cell types including pancreatic cells. TGF 1 signals are sent through two types of transmembrane serine/threonine kinase receptors. In fact, TGF 1 binds and brings together the type I and type II receptors.