For example, PIK3CA, PTEN, TSC1 Wortmannin clinical trial 2, HER2, AKT, and PDPK1 have been found to be frequently mutated or amplified in cancer and thereby PI3K AKT mTOR path way is an attractive target for therapeutics. In clinical trials, there are a number of drugs that target proteins involved in this pathway. For example, flavonoid derivative Ly294002 is a PI3K inhibitor that acts in the ATP binding site of PI3K enzyme and targets the PI3K AKT axis. Rapamycin is an immunosuppressant and a potential clinical drug that inhibits mTOR by binding to the phos phatidic acid binding site required for mTOR activation. Thus, mTOR cannot phosphorylate p70S6 kinase resulting in G1 arrest of the cell cycle and suppression of protein synthesis.

Despite the fact that PI3K AKT mTOR pathway contains many putative therapeutic targets, the clinical trials with the pathway specific drugs have not been as promising as previously thought. This might be due to the cross talk of PI3K AKT mTOR pathway Inhibitors,Modulators,Libraries with multiple other signalling pathways leading to multiple sites of regulation. Similarly, the diversity of genetic aber rations activating this pathway is likely to cause differ ences in drug responses. Our aim was to identify genes that are transcriptionally altered due to PI3K mTOR p70S6K pathway inhibition in breast cancer cells using RNAi and small molecule inhibi tors. p70S6K encoded by RPS6KB1 was knocked down using three different siRNAs in BT 474 and MCF 7 breast cancer cell lines, since these cell lines show high level amplification and overexpression of RPS6KB1.

Ly294002 and rapamycin are known to target PI3K mTOR pathway upstream of p70S6K. Therefore, breast cancer cell lines BT 474, MCF 7, MDA 361, MDA 436 and SK BR 3 were treated with these inhibitors to compare transcriptional signatures responsive Inhibitors,Modulators,Libraries to both RPS6KB1 and PI3K mTOR pathway inhibitions. Our results show for the first time the genome wide transcriptional consequences of PI3K mTOR pathway and RPS6KB1 inhibitions in breast can cer, suggesting novel downstream targets for PI3K mTOR pathway and p70S6 kinase. Results p70S6K suppression induces specific gene expression alterations To identify downstream targets of p70S6K in breast cancer cells, we first examined gene expression alterations Inhibitors,Modulators,Libraries in RPS6KB1 suppressed BT 474 and MCF 7 breast cancer cell lines that normally show high level expression of p70S6K.

We used three different siRNAs to knock down the expres Inhibitors,Modulators,Libraries sion of RPS6KB1. Based on Inhibitors,Modulators,Libraries the microarray anal yses, the signal log10 ratio with siRNA 1 was 0. 5, resulting in 70% relative downregulation of RPS6KB1 mRNA, whereas with RPS6KB1 siRNAs 2 and 3 log10 ratios were 0. 3 0. 5 with different probes representing RPS6KB1, indicating 50 70% relative suppression http://www.selleckchem.com/products/INCB18424.html with these two siRNAs. The signal log10 ratios of all the genes representing their mRNA expression levels are available at CanGEM.