Synthesis and Biological Evaluation of Analogs of Didehydroepiandrosterone as Potential New Anticancer Agents.

The synthesis, cytotoxicity and inhibition of CDK8 by thirteen analogs of cortistatin A are reported. These efforts revealed that the analogs with either a 6- or 7-isoquinoline or 5-indole side chain in the 17-position are the most promising anti-proliferative agents. These compounds showed potent cytotoxic effects in CEM, HeLa and HMEC-1 cells. All three compounds exhibited IC50 values < 10µM. The most interesting 10l analog exhibited an IC50 value of 0.59 µM towards the human dermal microvascular endothelial cell line (HMEC-1), significantly lower than the reference standard 2-methoxyestradiol. At a concentration at 50 nM the most potent 10h compound reduced the activity of CDK8 to 35%.

New CDK8 inhibitors as potential anti-leukemic agents - Design, synthesis and biological evaluation.

Cyclin-dependent kinase 8 (CDK8) plays a vital role in regulating cell transcription either through its association with the mediator complex or by the phosphorylation of transcription factors. CDK8-mediated activation of oncogenes has proved to be important in a variety of cancer types including hematological malignancies. We have designed and synthesized a series of new synthetic steroids. The compounds were evaluated as CDK8 inhibitors in vitro. The three most potent compounds exhibit Kd-values towards CDK8 in the low nanomolar range (3.5-18 nM). Furthermore, the compounds displayed selectivity for CDK8 in a panel of 465 different kinases. The cell studies indicated a selectivity to kill AML-cancer cell lines compared to normal cell lines.

Synthesis, molecular modeling and biological evaluation of potent analogs of 2-methoxyestradiol.

The endogenous steroid 2-methoxyestradiol (1) has attracted a great interest as a lead compound towards the development of new anti-cancer drugs. Herein, the synthesis, molecular modeling, anti-proliferative and anti-angiogenic effects of ten 2-ethyl and four 2-methoxy analogs of estradiol are reported. The ethyl group was introduced to the steroid A-ring using a novel Friedel-Crafts alkylation protocol. Several analogs displayed potent anti-proliferative activity with IC50-values in the submicromolar range towards the CEM human leukemia cancer cell line. As such, all of these compounds proved to be more active than the lead compound 2-methoxyestradiol (1) in these cells. The six most cytostatic analogs were also tested as anti-angiogenic agents using an in vitro tube formation assay. The IC50-values were determined to be in the range of 0.1 µM ±â€¯0.03 and 1.1 µM ±â€¯0.2. These six compounds were also modest inhibitors against tubulin polymerization with the most potent inhibitor was 14b (IC50 = 2.1 ±â€¯0.1 µM). Binding studies using N,N'-ethylene-bis(iodoacetamide) revealed that neither14a or 14b binds to the colchicine binding site in the tubulin protein, in contrast to 2-methoxyestradiol (1). These observations were supported by molecular modeling studies. Results from a MDA-MB-231 cell cycle assay showed that both 10e and 14b gave accumulation in the G2/M phase resulting in induction of apoptosis. The results presented herein shows that the novel analogs reported exhibit their anticancer effects via several modes of action.

Differential effects of some novel synthetic oestrogen analogs on oxidative PC12 cell death caused by serum deprivation.

Oestrogens with no or reduced oestrogen receptor (ER) binding properties are reported to have neuroprotective functions. However, we have previously shown that the hormonally inactive isomer of 17ß-estradiol (17ß-E), 17α-estradiol (17α-E), down-regulates glutathione (GSH) synthesis, and fails to rescue serum deprivation-induced cell death in the rat pheochromocytoma cell line PC12 in micromolar concentration. The present study examined cellular protective effects of new 17ß-E analogs and 2-methoxyestradiol (2-ME) analogs with no or little oestrogen activity. 17ß-E, 17α-E, 2-ME, and an antagonist of the G protein-coupled oestrogen receptor (GPER), G36, were also included. Both 17α-E and 2-ME protected against deprivation-induced cell death in PC12 cells at 1 nM, but they enhanced the deprivation-induced cell death accompanied by caspase 3 activity and decreased intracellular GSH levels during deprivation at 10 µM. In addition, 10 µM 17α-E activated the p38 mitogen activated protein kinase pathway, which was linked to the enhanced death and reduced GSH levels. Analogs of 2-ME modified with a 6-isoquinoline moiety (6iq) protected against deprivation-induced cell death at 1 nM and did not interfere with the GSH levels nor increase p38 protein levels at 10 µM. The promoter activity of the catalytic subunit of the rate-limiting enzyme, glutamate cysteine ligase (GCLC) in GSH synthesis as well as protein levels of GCLC and Nrf2, increased with the 2-ME analogs at 10 µM. In conclusion, the steroids have differential protective effects, and modifying 2-ME may give the steroid more favourable properties than 17α-E, 2-ME, and G36 in regard to GSH regulation.

Regioselective monoalkylation of 17ß-estradiol for the synthesis of cytotoxic estrogens.

The regioselective synthesis of estrogens and their derivatives continues to be of interest. Most reported syntheses require multistep protocols associated with poor overall yield and lack of regioselectivity. New preparative protocols are still desired. Herein, 11 2-alkylated 17ß-estradiol analogs were synthesized in a highly regioselective manner. The products were obtained using a convenient, one pot and high-yielding protocol. The anti-proliferative activity of the compounds was tested in human T-cell leukemia (CEM), human cervix carcinoma (HeLa) and human dermal microvascular endothelial (HMEC-1) cells.

Synthesis and Pharmacological Effects of the Anti-Cancer Agent 2-Methoxyestradiol.

The endogenous steroid 2-methoxyestradiol (2-ME) is a metabolite of 17ß-estradiol and its biosynthesis is well established. Moreover, 2-ME is also biosynthesized from estrone. For several years, 2-ME was perceived as an inactive metabolite devoid of any interesting biological activities. Since the late 1980s, a number of biological and pharmacological studies have revealed that 2-ME possesses interesting anti-cancer effects without any undesirable estrogen activity. In particular, the anti-vascular effects and anti-angiogenic activities that 2-ME exhibit, are of great interest and importance, in view of the development of new anti-cancer drugs based on 2-ME. Several clinical trial development programs have been initiated using the steroid 2-ME. In addition, based on the many pharmacological activities reported for 2-ME, but also due to the general interest in total and semi-synthesis of endogenous steroids, several research groups working with organic synthesis have prepared this steroid. Herein, the anti-cancer effects, the results from the clinical trial development programs and the synthetic studies towards 2-ME, are reviewed.

Synthesis and biological evaluations of new analogs of 2-methoxyestradiol: inhibitors of tubulin and angiogenesis.

The synthesis, cytotoxicity, inhibition of tubulin polymerization and anti-angiogenic effects of 15 analogs of 2-methoxyestradiol (1) are reported. The biological studies revealed that the position of nitrogen atom in the heterocyclic ring is important for inhibition of both tubulin polymerization and angiogenesis. The most potent inhibitors were compounds 11f and 13e, with a 6-substituted isoquinoline ring in the 17-position of the steroid skeleton. Moreover, low estrogen activity was observed for the analogs tested at 10 µM concentrations.

Synthesis, cytotoxic effects and tubulin polymerization inhibition of 1,4-disubstituted 1,2,3-triazole analogs of 2-methoxyestradiol.

Thirteen 1,4-disubstituted 1,2,3-triazole analogs of 2-methoxyestradiol were prepared and tested for their cytotoxic and tubulin polymerization inhibition effects. Two compounds, 11j and 11k, exhibited anti-proliferative effects at low micromolar concentrations. The two analogs 11j and 11k also inhibited tubulin assembly with IC50 values of 8.1 and 5.9µM, respectively.