239 15-deoxy-delta-12,14-Prostaglandin-J2 inhibits multidrug resistance genes and induces apoptosis in doxorubicin-resistant ovarian carcinoma cells

Abstract

Background: Development of chemoresistance in tumour cells is one of the biggest problems in cancer therapies. Multidrug resistance (mdr1) upregulation is known to be related to the activation of NF-κB pathway in tumour cells. Recently, we have reported that 15-deoxy-delta-12, 14-Prostaglandin-J2 (15d-PGJ2), a peroxisome proliferators-activated receptor-gamma (PPAR-γ) agonist, induces cell death in non-resistant tumour cells by inhibiting at least partly the NF-κB activity and exhibited antitumour effects in vivo. In the present study, we investigated whether 15d-PGJ2 could also inhibit NF-κB pathway in doxorubicin-resistant ovarian carcinoma cells and thereby induce apoptosis and inhibit mdr1 expression. Material and Methods: Human ovarian carcinoma cell lines, A2780 (non-resistant) and A2780/AD (doxorubicin-resistant), were used for this study. The cell viability was evaluated using Alamar blue assay by incubating with 15d-PGJ2 and other compounds for 48h in serum-free medium. To determine the NF-κB and caspase-3/7 activities, a plasmid-based Luciferase reporter assay and a luminescence assay were used, respectively. Gene expression levels were determined through quantitative real-time PCR. Results: Doxorubicin-resistant A2780/AD cells had significantly higher expression of mdr1 and enhanced NF-kB activity compared to the non-resistant A2780 cells. Treatment with 15d-PGJ2 induced cell death in both A2780 and A2780/AD cells with a similar potency (IC50=5.0μM). The effects were found to be PPARγ-independent as an irreversible PPARγ antagonist GW9662 could not block these effects. Also, 15d-PGJ2 significantly enhanced the caspase-3/7 enzyme activity in both cell types indicating its caspase-mediated apoptotic activity. Furthermore, we found that 15d-PGJ2 significnalty inhibited the NF-kB activity either inherent or induced with TNF-alpha in these cells. At a low dose (2.5μM), 15d-PGJ2 significantly inhibited the expression of drug resistant-related genes (mdr1 and sirt1) and antiapoptotic genes (bcl-2 and bcl-xl) in A2780/AD cells. Treatment with a specific NF-κB inhibitor BAY11-7082 only inhibited mdr1 and sirt1 gene expression but not of bcl-2 and bcl-xl. These data suggest that inhibition of the drug resistance regulating genes by 15d-PGJ2 is mediated through the blockade of the NF-κB pathway. Conclusion: The present study demonstrates that 15d-PGJ2 can induce apoptosis in doxorubicin-resistant ovarian tumour cells and also inhibits multidrug resistance-regulating genes. Therefore, 15d-PGJ2 is in potential a promising therapeutic agent for the treatment of chemoresistant tumours.