Synthesis, antiproliferative, and pharmacokinetic properties of 3- and 17-double-modified analogs of 2-methoxyestradiol

Design, synthesis and antiproliferative effect of 17β-amide derivatives of 2-methoxyestradiol and their studies on pharmacokinetics

A series of 17β-amide-2-methoxyestradiol compounds were synthesized with an aim to enhance the antiproliferative effect of 2-methoxyestradiol. The antiproliferative activity of 2-methoxyestradiol analogs against human cancer cells was investigated. 2-methoxy-3-benzyloxy-17β-chloroacetamide-1,3,5(10)-triene (5e) and 2-methoxy-3-hydroxy-17β-butyramide-1,3,5(10)-triene (6c) had comparable or better antitumor activity than 2-methoxyestradiol. The elimination half-life of 6c (t_1/2β=240.93min) is ten times longer than 2-ME and the area under the curve was seven times (AUC_0-tmin=2068.20±315.74μgmL^-1min) higher than 2-ME, respectively. Whereas 5e had similar pharmacokinetic behavior with 2-ME (t_1/2β=22.28min) with a t_1/2β of 29.5 min. 6c had higher blood concentration, longer actuation duration and better suppression rate against S180 mouse ascites tumor than 2-methoxyestradiol.

Synthesis of sex hormone-derived modified steroids possessing antiproliferative activity

During recent years intensive research has been focused on the synthesis of structurally modified steroid hormones in order to obtain compounds with beneficial biological activity such as cell-growth inhibition. Experimental results have revealed that some steroidal derivatives possess direct cytostatic effect on cancer cells in a hormone receptor-independent manner. After a brief account on the most important biological function and characteristics of the naturally occurring sex hormones in physiological and pathological conditions, structural modifications of estrane and androstane scaffolds are discussed in detail. The review covers literature publications (from 2002 to 2012) relating to the synthesis and antiproliferative activity of semisynthetic sex hormone-derived molecules containing simple or heterocyclic substituents. The compounds reviewed are divided into three main categories according to their sterane framework and the nature of substitution. This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

Signaling pathways of ESE-16, an antimitotic and anticarbonic anhydrase estradiol analog, in breast cancer cells

The aim of this study was to characterize the in vitro action of 2-ethyl-3-O-sulphamoyl-estra-1,3,5(10)16-tetraene (ESE-16) on non-tumorigenic MCF-12A, tumorigenic MCF-7 and metastatic MDA-MB-231 breast cancer cells. ESE-16 is able to inhibit the activity of a carbonic anhydrase II and a mimic of carbonic anhydrase IX in the nanomolar range. Gene and protein expression studies using various techniques including gene and antibody microarrays and various flow cytometry assays yielded valuable information about the mechanism of action of ESE-16. The JNK pathway was identified as an important pathway mediating the effects of ESE-16 while the p38 stress-induced pathway is more important in MDA-MB-231 cells exposed to ESE-16. Lysosomal rupture and iron metabolism was identified as important mediators of mitochondrial membrane depolarization. Abrogation of Bcl-2 phosphorylation status as a result of ESE-16 also plays a role in inducing mitochondrial membrane depolarization. The study provides a basis for future research projects to develop the newly synthesized compound into a clinically usable anticancer agent either alone or in combination with other agents.

Keywords: Antimitotic, anticarbonic anhydrase IX, apoptosis, autophagy, cell cycle arrest, Bcl-2, JNK, p38, mitochondrial membrane depolarization, flow cytometry, gene expression and protein microarray, anticancer.

In vitro changes in mitochondrial potential, aggresome formation and caspase activity by a novel 17-β-estradiol analogue in breast adenocarcinoma cells

2-Methoxyestradiol, a natural metabolite of estradiol, exerts antiproliferative and antitumour properties in vitro and in vivo. Because of its low oral bioavailability, several promising analogues of 2-methoxyestradiol have been developed. In this study, the in vitro influence of the compound, 2-ethyl-3-O-sulphamoyl-estra-1,3,5(10)16-tetraene (C19), a non-commercially available 17-β-estradiol analogue, was tested on the breast adenocarcinoma MCF-7 cell line. The in vitro influence of 24 h exposure to 0.18 μM of C19 on MCF-7 cells was evaluated on cell morphology, cell cycle progression and possible induction of apoptosis and autophagy. Polarization-optical transmitted light differential interference contrast and fluorescence microscopy revealed the presence of cells blocked in metaphase, occurrence of apoptotic bodies and compromised cell density in C19-treated cells. Hallmarks of autophagy, namely an increase in the number of acidic vacuoles and lysosomes, were also observed in C19-treated samples. An increase in the number of cells present in the sub-G1 fraction, as well as a reduction in mitochondrial membrane potential was observed. No significant alterations in caspase 8 activity were observed. A twofold increase in aggresome formation was observed in C19-treated cells. C19 induced both apoptosis and autophagy in MCF-7 cells.

2-methoxyestradiol analogue ENMD-1198 reduces breast cancer-induced osteolysis and tumor burden both in vitro and in vivo

It has been estimated that 70% of advanced breast cancer patients will face the complication of bone metastases. Three processes are pivotal during bone metastatic growth of breast cancer, namely, tumor cell proliferation, angiogenesis, and osteolysis. During tumor-induced osteolysis, a number of cytokines and growth factors are released from the degraded bone matrix. These factors stimulate further tumor growth, tumor angiogenesis, and tumor-induced osteolysis. New therapies should target all relevant processes to halt this powerful feedback loop. Here, we characterized the new 2-methoxyestradiol analogue ENMD-1198 and showed that it is cytotoxic to tumor cells. Moreover, ENMD-1198 showed both antiangiogenic and vascular disruptive properties and was capable of protecting the bone against tumor-induced osteolysis. We confirmed the in vitro data with a series of in vivo experiments showing the beneficial effects of ENMD-1198 and ENMD-1198-based combination treatments of metastatic breast cancer in bone both on tumor progression and on survival with long-term ENMD-1198 treatment. We confirmed the in vivo relevance of the ENMD-1198 protective effect on bone both with X-ray radiographs and microcomputed tomography. In addition, we combined ENMD-1198 treatment with low-dose metronomic cyclophosphamide and the bisphosphonate risedronic acid, leading to a mild increase in treatment efficacy.

Therapeutic promises of 2-methoxyestradiol and its drug disposition challenges

2-Methoxyestradiol (2MeO-E2) is an endogenous metabolite of estrogen which was initially considered to be inactive. During the last few decades it has been shown that 2MeO-E2 is a promising anticancer drug. In vitro experiments have demonstrated that it has several anticancer activities, and potential to alleviate hypertension, glomerulosclerosis, hypercholesterolemia, and other disorders. However, due to its low solubility and extensive glucuronidation, to achieve effective concentrations large doses of 2MeO-E2 would be required. Clinical studies reflected very high inter- and intrapatient variability and oral bioavailability of 1 to 2%. Thus, this review paper highlights the origin of this compound, its therapeutic promises, and possible mechanisms of action. It also discusses the pharmacokinetic properties of 2MeO-E2 as well as current developments to overcome low drug solubility and its extensive first pass metabolism.

Synthesis and antitumor activities of 3-modified 2-methoxyestradiol analogs

The syntheses of 2-methoxyestradiol analogs with modifications at the 3-position are described. The analogs were assessed for their antiproliferative, antiangiogenic, and estrogenic activities. Several lead substituents were identified with similar or improved antitumor activities and reduced metabolic liability compared to 2-methoxyestradiol.