15-deoxy-delta(12-14)-prostaglandin-j2 and Leukemia

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) induces apoptosis in many transformed cells; however, not all human tumors respond to TRAIL, potentially limiting its therapeutic utility. Although there is substantial evidence that cytotoxic drugs can augment sensitivity to TRAIL, it has become important to know what kinds of nontoxic drugs can be used together with TRAIL. We thus screened several natural compounds that can overcome resistance to TRAIL and found that a cycloanthranilylproline derivative, Fuligocandin B (FCB), an extract of myxomycete Fuligo candida, exhibited significant synergism with TRAIL. Treatment of the TRAIL-resistant cell line KOB with FCB and TRAIL resulted in apparent apoptosis, which was not induced by either agent alone. FCB increased the production of 15-deoxy-Delta(12,14) prostaglandin J(2) (15d-PGJ(2)), an endogenous PPAR gamma ligand, through activation of cyclooxygenase-2 (COX-2). This unique mechanism highlighted the fact that 15d-PGJ(2) directly enhanced sensitivity to TRAIL by inhibiting multiple antiapoptotic factors. More importantly, similar effects were observed in other leukemia cell lines irrespective of their origin. The enhancement was observed regardless of PPAR gamma expression and was not blocked even by peroxisome proliferator-activated receptor-gamma (PPAR gamma) siRNA. These results indicate that 15d-PGJ(2) sensitizes TRAIL-resistant cells to TRAIL in a PPAR gamma-independent manner and that the use of 15d-PGJ(2) or its inducers, such as FCB, is a new strategy for cancer therapy.

Topics: Apoptosis; Cell Line, Transformed; Cyclooxygenase 2; Drug Resistance, Neoplasm; Drug Screening Assays, Antitumor; Drug Synergism; Enzyme Activation; Gene Expression Regulation, Leukemic; HL-60 Cells; Humans; Inhibitor of Apoptosis Proteins; K562 Cells; Leukemia; Neoplasm Proteins; PPAR gamma; Proline; Prostaglandin D2; TNF-Related Apoptosis-Inducing Ligand

The peroxisome proliferator-activated receptor gamma (PPAR gamma) is a member of the nuclear receptor family that forms heterodimers with retinoid X receptor. These heterodimers bind to DNA and activate the transcription of target genes. Here, we report that the PPAR gamma receptor protein is expressed in primary myeloid and lymphoid leukemias and in lymphoma and myeloma cell lines. In this study, we compared the activity of several PPAR gamma ligands including BRL49653 (rosiglitazone), 15-deoxy-Delta 12,14-prostaglandin J(2), and the novel triterpenoid 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid on leukemia cells. Exposure to these PPAR gamma ligands induced apoptosis in myeloid (U937 and HL-60) and lymphoid (Su-DHL, Sup-M2, Ramos, Raji, Hodgkin's cell lines, and primary chronic lymphocytic leukemia) cells. A similar exposure to these PPAR gamma ligands induced the differentiation of myeloid leukemic cells. A combination of PPAR gamma ligands with a retinoid X receptor agonist (i.e., LG100268) or a retinoic acid receptor agonist (i.e., all trans-retinoic acid) enhanced differentiating and growth-inhibitory effects. 2-Cyano-3,12-dioxooleana-1,9-dien-28-oic acid induced differentiation and apoptosis with much greater potency than the other PPAR gamma ligands in established cell lines and primary chronic lymphocytic leukemia samples. Exposure to 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid induced mitochondrial depolarization and caspase activation, which was associated with apoptosis induction. In Bcl-2-overexpressing chronic lymphocytic leukemia cells, the small-molecule Bcl-2 inhibitor HA14-1 sensitized these cells to 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid-induced apoptosis. These results suggest that PPAR gamma ligation alone and in combination with retinoids holds promise as novel therapy for leukemias by activating the transcriptional activity of target genes that control apoptosis and differentiation in leukemias.

Topics: Agar; Apoptosis; Blotting, Western; Cell Differentiation; Cell Line; Cell Line, Tumor; Cell Nucleus; Cell Proliferation; Cell Survival; Dimerization; Fibrinolytic Agents; Flow Cytometry; HL-60 Cells; Humans; Imidazoles; Immunologic Factors; Jurkat Cells; Leukemia; Ligands; Oleanolic Acid; Phagocytosis; Plasmids; PPAR gamma; Prostaglandin D2; Proto-Oncogene Proteins c-bcl-2; Receptors, Retinoic Acid; Retinoic Acid Receptor alpha; Retinoid X Receptors; RNA, Messenger; Rosiglitazone; Thiazolidinediones; Transcription, Genetic; Transcriptional Activation; Transfection; U937 Cells

The nuclear peroxisome proliferator-activated receptor gamma (PPARgamma) ligands may enhance the etoposide-induced apoptosis by modulating the topoisomerase (Topo) IIalpha expression through binding to direct repeat 1 (DR1)-like element.. To investigate the effect of etoposide-induced apoptosis by PPARgamma ligands, leukemia cell lines were treated with troglitazone and 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) in the presence of etoposide and studied about various biological responses.. We found the enhancement of etoposide-induced apoptosis by PPARgamma ligands in several leukemia cell lines, which was dependent on the expression of PPARgamma and specific for TopoIIalpha inhibitor. We also observed the increased expression of TopoIIalpha protein by 15d-PGJ2 in Jurkat and HUVEC cells, which might lead to the increased sensitivity to etoposide. Furthermore, we demonstrated that 15d-PGJ2 enhanced the promoter activity of human TopoIIalpha promoter construct with a DR1-like site by sevenfold when expressed with PPARgamma and RXRalpha. The mutation of DR1-like site decreased the promoter activity, although the direct binding between DR1-like site and PPARgamma/RXRalpha heterodimer was not demonstrated.. We conclude that the induction of TopoIIalpha expression by PPARgamma ligands via DR1-like site is an important mechanism for the enhancement of etoposide-induced apoptosis and a DR1-like site in TopoIIalpha promoter is involved in transcriptional regulation dependent on PPARgamma ligands and PPARgamma/RXRalpha heterodimer.

Topics: Antigens, Neoplasm; Apoptosis; Chromans; DNA Topoisomerases, Type II; DNA-Binding Proteins; Electrophoretic Mobility Shift Assay; Etoposide; Flow Cytometry; Gene Expression; Humans; Jurkat Cells; Leukemia; Ligands; Mutagenesis; Phosphoproteins; Promoter Regions, Genetic; Prostaglandin D2; Receptors, Cytoplasmic and Nuclear; Receptors, Retinoic Acid; Retinoid X Receptors; Thiazoles; Thiazolidinediones; Topoisomerase II Inhibitors; Transcription Factors; Transfection; Troglitazone; Tumor Cells, Cultured