The p21 expression was consistent with p53 ex pression in IBP knockdown and IBP over expressing MCF 7 cells. Furthermore, we detected cisplatin induced p53 phosphorylation selleck chemicals Seliciclib at Ser 15. In IBP knockdown cells, increased level of phosphorylated p53 could be induced by cisplatin, whereas lower level p53 Ser 15 phosphorylation was detected in the IBP over expressing Inhibitors,Modulators,Libraries MCF 7 cells. This data suggests that IBP over expression in breast cancer cells decreases p53 accumulation and activa tion in response to cisplatin. Members of the Bcl 2 family also are key players in regulating apoptosis. The apoptotic process is regulated by the ratio between Bax and its antiapoptotic counterpart Bcl 2. It is also known that p53 negatively regulates Bcl 2 expression and that wild type p53 neutralises the death protective function of Bcl 2.

We tested Bcl 2 and Bax levels in IBP over expressing MCF 7 cells. The levels Inhibitors,Modulators,Libraries Therefore the decreased survival with cisplatin in MCF 7/IBP RNAi cells was in large part due to an increase cell death. To confirm that IBP depletion increased cisplatin induced apoptosis in MCF 7 cells, we tested PARP and Annexin V PI expression. When the cells were treated with cisplatin for 24 h, more cleaved PARP was detected in the Inhibitors,Modulators,Libraries MCF 7/IBP RNAi cells. In addition, MCF 7/ IBP RNAi cells showed increased percentage of Annexin V PI positive cells 12 h after cisplatin treatment. These results demonstrate that IBP participates in the sup pression of cisplatin induced apoptosis in MCF 7 cells.

IBP over expression inactivates p53 pathway through AKT Since IBP suppressed cisplatin induced apoptosis, we fur ther investigated the effect of IBP on cisplatin induced apoptotic signals. Stabilization and activation of wild type p53 are critical for cisplatin mediated apoptosis. We tested whether the mechanism of IBP induced cisplatin of Bcl 2 were Inhibitors,Modulators,Libraries highly elevated in IBP over expressing MCF 7 cells, and Bax expression was markedly reduced. This result shows that IBP regulates Bcl 2 family expression, and IBP disruptes p53 dependent apop totic pathway in breast cancer cells. Thus, there is a posi tive feedback loop between IBP and p53 pathway. All p53 auto regulatory loops are either induced by Inhibitors,Modulators,Libraries p53 at the transcriptional level or regulated by p53 induced proteins. It is known that AKT, which is closely asso ciated with DNA damage, induces the phosphorylation of MDM 2 protein, which results in the translocation of MDM 2 into the nucleus where it inactivates p53.

Because the closest homolog of IBP, SWAP 70, is required for the proper activation of AKT, we tested whether IBP may also activate AKT. We found high level of AKT Ser 473 and MDM2 no Ser 166 phosphorylation in IBP over expressing MCF 7 cells. Moreover, when we treated IBP over expressing MCF 7 cells with AKT inhibitor Ly294002 or wortmannin, p53 and p21 ex pression was elevated, and MDM2 phosphorylation was decreased.