Cytoplasmic p21 induced by p65 prevents doxorubicin-induced cell death in pancreatic carcinoma cell line

Background: studies have shown the existence of p21 induction in a p53-dependent and -independent pathway. our previous study indicates that dox-induced p65 is able to bind the p21 promoter to activate its transactivation in the cells. methods. over-expression and knock-down experiments were performed in human pancreatic carcinoma (panc1) cells. cell cycle and cell death related proteins were assessed by western blotting. cytotoxicity assay was checked by cck-8 kit. cell growth was analyzed by flow cytometers. results: here we showed that over-expression of p65 decreased the cytotoxic effect of dox on panc1 cells,correlating with increased induction of cytoplasmic p21. we observed that pro-caspase-3 physically associated with cytoplasmic p21,which may be contribution to prevent p21 translocation into the nucleus. our data also suggested that no clear elevation of nuclear p21 by p65 provides a survival advantage by progression cell cycle after treatment of dox. likewise,down-regulation of p65 expression enhanced the cytotoxic effect of dox,due to a significant decrease of mrna levels of anti-apoptotic genes,such as the cellular inhibitor of apoptosis-1 (c-iap1),and the long isoform of b cell leukemia/lymphoma-2 (bcl-2),leading to efficient induction of caspase-3 cleavage in the cells. more,we present evidence that over-expression of p53 or p53/p65 in the panc1 cells were more sensitive to dox treatment,correlated with activation of caspase-3 and clear elevation of nuclear p21 level. our previous data suggested that expression of p21 increases gefitinib-induced cell death by blocking the cell cycle at the g1 and g2 phases. the present findings here reinforced this idea by showing p21's ability of potentiality of dox-induced cell death correlated with its inhibition of cell cycle progression after over-expression of p53 or p53/p65. conclusion: our data suggested p65 could increase p53-mediated cell death in response to dox in panc1 cells. thus,it is worth noting that in p53 null or defective tumors,targeting in down-regulation of p65 may well be useful,leading to the potentiality of chemotherapeutic drugs. © 2012 zhou et al; licensee biomed central ltd.