However, sorafenib was found to show a complex inhibition profile affecting various ef fector kinases in several cellular signaling http://www.selleckchem.com/products/Gefitinib.html pathways and is therefore considered a multi kinase inhibitor today. Recently, it has been shown that PI3K AKT signal ing rather than the Raf Mek Erk cascade is both the main target of sorafenib in apoptosis initiation and a key player in de novo resistance against sorafenib. In our model, sorafenib suppressed proliferation at antici pated concentrations, but elicited no differential effects between BRAF mutant and wild type cells. This further supports the mechanism of sorafenib to be widely independent of Mek 1 2 phosphorylation. Recently, more selective B Raf inhibitors have been de veloped exhibiting considerable specificity for the V600E The predictive role of BRAF mutations in EGFR anti body therapy has been elucidated recently but remains poorly understood on the molecular Inhibitors,Modulators,Libraries level.

Our model enabled us to specifically analyze BRAF dependent ef fects of cetuximab sensitivity independent of confound ing Inhibitors,Modulators,Libraries genetic events. RKO cells and derived mutant and mutant kinase in vitro. Testing these compounds in our model system revealed that vemurafenib and RAF265 did not have significantly different effects on proliferation of the Inhibitors,Modulators,Libraries RKO derived clones. Mechanisms of resistance against B Raf inhibition are complex and involve activation of upstream rather than only downstream effectors of the B Raf kinase or can be modulated via other signaling pathways. Additionally, resistance against particular B Raf inhibi tors has recently been reported to occur frequently in colorectal cancer cells.

In contrast to these compounds, the B RafV600E inhibi tor dabrafenib selectively decreased proliferation of BRAF mutant cell clones. Remarkably, the IC50 ratio between the wild type clone RBW 1 and clones carrying a mutant allele only was 20, while it was only 5. 3 between RBW 1 and the heterozygous clones that carry both wild type and mutant alleles, potentially Inhibitors,Modulators,Libraries indicating a gene dosage effect. However, since the inhibition profile of dabrafenib is not yet fully known, a favorable off target effect cannot be excluded and should be fur ther examined in future studies. To further investigate the differential effects of the specific B RafV600E inhibitors, we examined their specific impact on downstream effectors of B Raf.

For this pur pose, we analyzed the relative phosphorylation levels of Mek 1 2 and Erk 1 2 in lysates from cells incu bated with compound concentrations corresponding to the previously determined IC50. All inhibitors reduced the relative level of Mek 1 2 phosphorylation in clones carry ing the Inhibitors,Modulators,Libraries V600E mutation by more than 90% with dabrafe nib showing the strongest effect. http://www.selleckchem.com/products/Bosutinib.html No reduction of Mek 1 2 phosphorylation was observed in RBW 1 BRAFwt cells. These data were further confirmed on the level of phospho Erk 1 2.