Thus, PTEN augments p21 stability via two downstream ele ments of the PI3K growth and survival signaling pathway, PI3K and Akt. Cytosolic localization of p21 is augmented in PTEN downregulated cells Subcellular localization of p21 is important in dictating its effect on cell growth and apoptosis, such that cytosolic p21 has been shown to result in activation Nutlin-3a side effects of anti apop totic and proliferative machinery, resulting in more aggressive tumor behavior and a poorer patient prognosis. We utilized immunofluorescence and immunohistochemistry techniques to assess subcel lular distribution of p21 in PTEN knockdown cells. Results were similar using both methods. i. e, p21 levels were substantially increased in the PTEN knockdown cells as compared to control transfectants.

Moreover, cytosolic localization of p21 also was increased in PTEN knockdown cells. To confirm this finding, we performed subcellular Inhibitors,Modulators,Libraries locali zation of PTEN knockdown and mutant shRNA control ACHN cells to determine Inhibitors,Modulators,Libraries whether p21 is directed more to the cytosol as a result of PTEN attenuation. In agreement strand breaks leading to increases in p53, which in turn activates either the cell death Inhibitors,Modulators,Libraries program, or alternatively, genes involved in cell cycle arrest and subse quent DNA repair. Thus, tumors har boring p53 mutations, fail to apoptose or growth arrest after DNA dam age and may thus escape death upon exposure to chemotherapeutic agents. this can lead to chemotherapy failure. The cyclin kinase inhibitor p21 is induced by p53 in situations of DNA damage, and it likely plays a role in the decision pathways leading to apoptosis or DNA repair .

for this reason, not only has p21 been Inhibitors,Modulators,Libraries proposed as a target for chemotherapy sensitization, but also, the mech anisms by which p21 becomes activated have Inhibitors,Modulators,Libraries attracted considerable interest in the study of chemotherapy resist ant Lenalidomide TNF-alpha inhibitor cancers. p21 was initially characterized based on its function as an inhibitor of G1 cyclin kinases, but after the discov ery that p21 possesses pro proliferative as well as anti apoptotic effects, research on this protein expanded to include to its roles in cancer progression and chemo therapy sensitivity. A putative relationship of p21 to PTEN was proposed after reports emerged that p21 is phospho rylated and stabilized by Akt. Our present findings with the immunofluorescence data, we found that the ratio of p21 in the cytosol as compared to the nucleus was markedly enhanced in PTEN KD cells. Whether these findings are due to a generalized increase in cellular p21 with a stoichiometric redistribution of a proportion of the total p21 from the nucleus to the cytosol, or to a specific augmentation of cytosolic p21 through a separate signaling mechanism, remains to be determined.