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

Abstract

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.

• Authors: YingQi Zhou, Gang Li, Yuan Ji, Chen Liu, JingPing Zhu, YanJun Lu
• Journal: Journal of biomedical science (J Biomed Sci) Vol. 19 Pg. 15 (Feb 04 2012) ISSN: 1423-0127 [Electronic] England
• PMID: 22305266 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antibiotics, Antineoplastic
• Cyclin-Dependent Kinase Inhibitor p21
• RNA, Messenger
• Transcription Factor RelA
• Tumor Suppressor Protein p53
• Doxorubicin

Topics

• Antibiotics, Antineoplastic (toxicity)
• Blotting, Western
• Cell Death
• Cell Line, Tumor
• Cyclin-Dependent Kinase Inhibitor p21 (biosynthesis, genetics)
• Doxorubicin (toxicity)
• Humans
• RNA, Messenger (genetics, metabolism)
• Real-Time Polymerase Chain Reaction
• Transcription Factor RelA (metabolism)
• Tumor Suppressor Protein p53 (metabolism)