Inverse PPARß/δ agonists suppress oncogenic signaling to the ANGPTL4 gene and inhibit cancer cell invasion.

Besides its established functions in intermediary metabolism and developmental processes, the nuclear receptor peroxisome proliferator-activated receptor ß/δ (PPARß/δ) has a less defined role in tumorigenesis. In the present study, we have identified a function for PPARß/δ in cancer cell invasion. We show that two structurally divergent inhibitory ligands for PPARß/δ, the inverse agonists ST247 and DG172, strongly inhibit the serum- and transforming growth factor ß (TGFß)-induced invasion of MDA-MB-231 human breast cancer cells into a three-dimensional matrigel matrix. To elucidate the molecular basis of this finding, we performed chromatin immunoprecipitation sequencing (ChIP-Seq) and microarray analyses, which identified the gene encoding angiopoietin-like 4 (ANGPTL4) as the major transcriptional PPARß/δ target in MDA-MB-231 cells, previously implicated in TGFß-mediated tumor progression and metastatic dissemination. We show that the induction of ANGPTL4 by TGFß and other oncogenic signals is strongly repressed by ST247 and DG172 in a PPARß/δ-dependent fashion, resulting in the inhibition of ANGPTL4 secretion. This effect is attributable to these ligands' ability to induce a dominant transcriptional repressor complex at the site of transcription initiation that blocks preinitiation complex formation through an histone deacetylase-independent, non-canonical mechanism. Repression of ANGPTL4 transcription by inverse PPARß/δ agonists is functionally linked to the inhibition of cancer cell invasion into a three-dimensional matrix, as (i) invasion of MDA-MB-231 cells is critically dependent on ANGPTL4 expression, (ii) recombinant ANGPTL4 stimulates invasion, and (iii) reverses the inhibitory effect of ST247 and DG172. These findings indicate that a PPARß/δ-ANGPTL4 pathway is involved in the regulation of tumor cell invasion and that its pharmacological manipulation by inverse PPARß/δ agonists is feasible.

Stability-indicating HPLC assays for the determination of piritramide and droperidol in PCA solution.

WHAT IS KNOWN AND OBJECTIVE: A mixture of morphine and droperidol is a well-established antiemetic for reducing the risk of postoperative nausea and vomiting. A mixture of piritramide and droperidol has not yet been evaluated in this context. Our objectives were to develop a high-performance liquid chromatographic assay for piritramide and droperidol in 0·9% saline, and to establish their stability under defined storage conditions. METHODS: The separation and assay of both drugs were attempted by high performance liquid chromatography (HPLC) using a RP-select B column and a mobile phase of 57:43% v/v methanol-monosodium phosphate solution 0·05 M at a flow rate of 1·2 mL/min. UV detection at 205 and 246 nm for piritramide and droperidol were used, respectively. RESULTS AND DISCUSSION: The HPLC method was successful. Linearity was shown for piritramide from 0·075 to 0·013 mg/mL and for droperidol from 0·8 to 0·2 mg/mL. The intra- and inter-day relative standard deviation (RSD, %) was 0·27% and 0·54% for piritramide and droperidol, respectively. The two drugs were stable for at least 72 h when stored under ambient light at room temperature. WHAT IS NEW AND CONCLUSION: Seventy-five milligrams piritramide and 2·5 mg droperidol diluted to 50 ml with 0·9% saline should be suitable for clinical use. At this dilution, a Dipidolor(®) and Xomolix(®), mixture, was stable when stored under ambient light exposure at room temperature for at least 72 h.