Synthesis of new antineoplastic prostaglandins

Biochemistry of prostaglandins A

This review considers modern concepts on the structural-functional properties and antiproliferative, antitumor, and antiviral effects of cyclopentenone prostaglandins A and mechanisms underlying their actions. Possible directions of pharmacological application of these compounds and their analogs are discussed.

Cyclopentenone prostaglandins: new insights on biological activities and cellular targets

The cyclopentenone prostaglandins PGA2, PGA1, and PGJ2 are formed by dehydration within the cyclopentane ring of PGE2, PGE1, and PGD2. PGJ2 is metabolized further to yield Delta(12)-PGJ(2) and 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)). Various compounds within the cyclopentenone prostaglandin family possess potent anti-inflammatory, anti-neoplastic, and anti-viral activity. Most actions of the cyclopentenone prostaglandins do not appear to be mediated by binding to G-protein coupled prostanoid receptors. Rather, the bioactivity of these compounds results from their interaction with other cellular target proteins. 15-deoxy-Delta(12,14)-PGJ(2) is a high affinity ligand for the nuclear receptor PPARgamma and modulates gene transcription by binding to this receptor. Other activities of the cyclopentenone prostaglandins are mediated by the reactive alpha,beta-unsaturated carbonyl group located in the cyclopentenone ring. The transcription factor NF-kappaB and its activating kinase are key targets for the anti-inflammatory activity of 15d-PGJ2, which inhibits NF-kappaB-mediated transcriptional activation by PPARgamma-dependent and independent molecular mechanisms. Other cyclopentenone prostaglandins, such as Delta(7)-PGA1 and Delta(12)-PGJ2, have strong anti-tumor activity. These compounds induce cell cycle arrest or apoptosis of tumor cells depending on the cell type and treatment conditions. We review here recent progress in understanding the mechanisms of action of the cyclopentenone prostaglandins and their possible use as therapeutic agents.

Antitumor activity, optimum administration method and pharmacokinetics of 13,14-dihydro-15-deoxy-deoxy-Delta7 -prostaglandin A1 methyl ester (TEI-9826) integrated in lipid microspheres (Lipo TEI-9826)

13,14-Dihydro-15-deoxy-Delta7-prostaglandin A1 methyl ester (TEI-9826), an antitumor prostaglandin analog, is a candidate for clinical trial. In the present study, we examined its biological stability in vitro, antitumor activity in vitro and in vivo, and pharmacokinetics. Although TEI-9826 was rapidly hydrolyzed to the carboxylic acid form (TOK-4528), TOK-4528 as well as Delta12-prostaglandin J2 (PGJ2) were found to be stable in rat, mouse and human serum in vitro. TEI-9826 exhibited nearly identical or greater potential antitumor activity compared to Delta12-PGJ2 and Delta7-PGA1 in vitro against Colon26 tumor cells. Further evaluation of TEI-9826 using the 38 human cancer cell lines panel and COMPARE analysis suggested that its mode of action is quite different from other anticancer agents that are currently used. TEI-9826 was integrated into lipid microspheres (Lipo TEI-9826) for dosing. Growth inhibition by Lipo TEI-9826 against Colon26 tumor inoculated s.c. in mice depended on administration route, i.e. at 80 mg/kg, no growth suppressive effect was observed for daily bolus i.v., but significant growth suppressive effect was observed for daily i.p., daily s.c. every other day s.c. and 4 times a day continuous (5 min) i.v. These tumor growth-suppressive effects were cytostatic and the tumor started to regrow at the end or a few days after the end of administration. The pharmacokinetic study suggested that maintaining the blood level of TEI-9826 and/or TOK-4528 was essential for their antitumor effects. These results show that continuous i.v. infusion might be the most suitable administration method of Lipo TEI-9826 for clinical trial.

Preparation and evaluation of o/w type emulsions containing antitumor prostaglandin

Antitumor prostaglandins(PGs) such as Delta12-PGJ2 and Delta7-PGA1 possess a cyclopentenone or cross-conjugated dienone structures. Antitumor PGs are actively incorporated through cell membrane and control gene expression. Very recent studies clarified that P53 independent expression of p21 and gadd 45, activation of PPARgamma are involved in antitumor mechanism of these PGs. At the low concentration, these PGs exhibit physiological or pathological activity such as osteoblast calcification, promotion of colon cancer cell proliferation. COMPARE PROGRAM using human 38 tumor cell lines suggested that antitumor mechanism of Delta7-PGA1 and 13, 14-dihydro-15-deoxy-Delta7-PGA1 methyl ester (TEI-9826) are quite different from other anticancer agents which are clinically used. Lipid microspheres and Lipiodol formulation were examined as dosage form of the PGs and lipid microspheres were selected for further study. At first lipid microspheres integrated TEI-9038 (Lipo TEI-9038) was chosen as a candidate for clinical trial. However Lipo TEI-9038 failed to exhibit substantial antitumor effect because of its enzymatic instability and toxicity in vivo. Lipo TEI-9826 was then selected as promising candidate for clinical trial because of its stability in serum. Lipo TEI-9826 exhibited marked antitumor effect in several animal models including CDDP resistant nude mice model. Pharmacokinetic and toxicological studies using rats suggested that continuous infusion is the most suitable administration method for Lipo TEI-9826. New type emulsifier, Controlled High Pressure Process Homogenizer (De-BEE 2000 and mini De-BEE) was developed during the preclinical studies on manufacturing process of Lipo TEI-9826. These results warrant the clinical trial for Lipo TEI-9826 in CDDP resistant cancer.

[35S]S-[5-(4-benzoylphenyl)pentyl]glutathione: a versatile radioligand targeting GS-X pumps with the ability of photoaffinity labeling

[35S]S-[5-(4-benzoylphenyl)pentyl]glutathione (GIF-0017) as a biochemical probe targeting the ATP-dependent organic anion transporters GS-X pumps was synthesized by the reaction of [35S]glutathione and excess 4-(5-bromo)pentylbenzophenone under alkaline conditions, with the radiochemical yield of 24-33% after HPLC purification. Photolysis of the mixture of [35S]GIF-0017 and plasma membrane vesicles prepared from the MRP1 cDNA-transfected LLC-PK1 cells resulted in radio-labeling of a 180-kDa membrane protein. Immunoprecipitation and western blotting using an anti-MRP1 monoclonal antibody confirmed that the [35S]GIF-0017-labeled protein was the MRPI/GS-X pump.

Synthesis and anti-cancer activity of 2-alkylaminomethyl-5-(E)-alkylidene cyclopentanone hydrochlorides

A series of 2-alkylaminomethyl-5-(E)-alkylidene cyclopentanone hydrochlorides (2), have been synthesized and evaluated as anti-cancer agents. These compounds were designed as masked alpha-methylenecyclopentanones, which appear in many cytotoxic or anti-cancer natural products. Most of the synthesized compounds were found to be active towards various human cancer cell lines and many showed significant subpanel selectivity. For compounds containing the same alkylidene moiety (from C3 to C9), the dimethylaminomethyl analogs were more active than structures possessing morpholino-, pyrrolidino-, or piperidino-methyl groups. Alteration of the alkylidene moiety had little effect on anti-cancer potency. The mass spectrum of a glutathione adduct of 2h indicated that the mechanism of action for these anti-cancer agents may be related to the attack at the aminomethyl carbon atom by biological nucleophilic thiols.

Use of lipid microspheres as a drug carrier for antitumour drugs

9-Oxo-15-hydroxy-delta 7,10,13-prostatrienoic acid methyl ester (delta 7-PGA1), an antitumour drug was incorporated into lipid microspheres of 0.2 micron diameter (lipo-delta 7-PGA1). In in-vivo experiments, lipo-delta 7-PGA1 had a significantly greater antitumour activity than free delta 7-PGA1 against P388 leukaemia. Lipo-delta 7-PGA1 slightly, but significantly, prolonged the survival time of mice inoculated with L1210 leukaemia, whereas free delta 7-PGA1 did not. Against MM46 ascites tumour, the survival time after treatment with 10 mg kg-1 of lipo-delta 7-PGA1 was significantly greater than that after the same dose of free delta 7-PGA1. The results suggest that lipid microspheres can be used as drug delivery carriers for lipid soluble antitumour agents.