X-ray and deuterium labeling studies on the abnormal ring cleavages of a 5 beta-epoxide precursor of formestane

Biotransformation of anabolic androgenic steroids in human skin cells

In comparison to well-known drug-metabolizing organs such as the liver, the metabolic capacity of human skin is still not well elucidated despite the widespread use of topical drug application. To gain a comprehensive insight into anabolic steroid metabolism in the skin, six structurally related anabolic androgenic steroids, testosterone, metandienone, methyltestosterone, clostebol, dehydrochloromethyltestosterone, and methylclostebol, were applied to human keratinocytes and fibroblasts derived from the juvenile foreskin. Phase I metabolites obtained from incubation media were analyzed by gas chromatography-mass spectrometry. The 5α-reductase activity was predominant in the metabolic pathways as supported by the detection of 5α-reduced metabolites after incubation of testosterone, methyltestosterone, clostebol, and methylclostebol. Additionally, the stereochemistry structures of fully reduced metabolites (4α,5α-isomers) of clostebol and methylclostebol were newly confirmed in this study by the help of inhouse synthesized reference materials. The results provide insights into the steroid metabolism in human skin cells with respect to the characteristics of the chemical structures.

Design, synthesis, biological activity evaluation and structure-activity relationships of new steroidal aromatase inhibitors. The case of C-ring and 7β substituted steroids

In this work, new steroidal aromatase inhibitors (AIs) were designed, synthesized, and tested. In one approach, C-ring substituted steroids namely those functionalized at C-11 position with an α or β hydroxyl group or with a carbonyl group as well as C-9/C-11 steroidal olefins and epoxides were studied. It was found that the carbonyl group at C-11 is more beneficial for aromatase inhibition than the hydroxyl group, and that the C-ring epoxides were more potent than the C-ring olefins, leading to the discovery of a very strong AI, compound 7, with an IC₅₀ of 0.011 μM, better than Exemestane, the steroidal AI in clinical use, which presents an IC₅₀ of 0.050 μM. In another approach, we explored the biological activity of A-ring C-1/C-2 steroidal olefins and epoxides in relation to aromatase inhibition and compared it with the biological activity of C-ring C-9/C-11 steroidal olefins and epoxides. On the contrary to what was observed for the C-ring olefins and epoxides, the A-ring epoxides were less potent than A-ring olefins. Finally, the effect of 7β-methyl substitution on aromatase inhibition was compared with 7α-methyl substitution, showing that 7β-methyl is better than 7α-methyl substitution. Molecular modelling studies showed that the 7β-methyl on C-7 seems to protrude into the opening to the access channel of aromatase in comparison to the 7α-methyl. This comparison led to find the best steroidal AI (12a) of this work with IC₅₀ of 0.0058 μM. Compound 12a showed higher aromatase inhibition capacity than two of the three AIs currently in clinical use.

A photochemical approach to 18-nor-17β-hydroxymethyl-17α-methylandrost-13-ene steroids

A photochemical approach to 18-nor-17β-hydroxymethyl-17α-methylandrost-13-ene unit of the long-term metabolites of 17-methylated androgenic anabolic steroids (AAS) is reported. It is based on a visible light-promoted radical decarboxylative alkynylation of steroidal redox-active ester. The developed method was used in synthesis of the long-term metabolite of AAS oxymesterone.

Synthesis and structural elucidation of a dehydrochloromethyltestosterone metabolite

The human urinary long-term metabolite "M3" (4-chloro-17β-hydroxymethyl-17α-methyl-18-norandrost-13-en-3-ol) of the common doping agent DHCMT has thus far been detected via GC/MS-MS, creating ambiguities concerning its absolute configuration. Its structure was elucidated via the synthesis of all eight possible stereoisomers with 17β-hydroxymethyl configuration. The highlights of the synthesis consist of a novel first generation approach to 4β-chloro-5β compounds as well as a divergent route which allows easy access to the remaining A-ring chlorohydrins.

Neurosteroid analogues. 18. Structure-activity studies of ent-steroid potentiators of γ-aminobutyric acid type A receptors and comparison of their activities with those of alphaxalone and allopregnanolone

A model of the alignment of neurosteroids and ent-neurosteroids at the same binding site on γ-aminobutyric acid type A (GABAA) receptors was evaluated for its ability to identify the structural features in ent-neurosteroids that enhance their activity as positive allosteric modulators of this receptor. Structural features that were identified included: (1) a ketone group at position C-16, (2) an axial 4α-OMe group, and (3) a C-18 methyl group. Two ent-steroids were identified that were more potent than the anesthetic steroid alphaxalone in their threshold for and duration of loss of the righting reflex in mice. In tadpoles, loss of righting reflex for these two ent-steroids occurs with EC50 values similar to those found for allopregnanolone. The results indicate that ent-steroids have considerable potential to be developed as anesthetic agents and as drugs to treat brain disorders that are ameliorated by positive allosteric modulators of GABAA receptor function.

Characterization of desoxymethyltestosterone main urinary metabolite produced from cultures of human fresh hepatocytes

Desoxymethyltestosterone (DMT; 17β-hydroxy-17α-methyl-5α-androst-2-ene) is a designer steroid present in hormonal supplements distributed illegally as such or in combination with other steroids, for self-administration. It figures on the list of substances prohibited in sports and its detection in athlete's urine samples is based upon the presence of the parent compound or the main urinary metabolite, which has not been characterized yet. Following its isolation from cultures of human fresh hepatocytes and S9 fractions of liver homogenates, we were able to identify this metabolite as being 17α-methyl-2β,3α,17β-trihydroxy-5α-androstane. Other minor metabolites were also characterized. The production, isolation, NMR, mass spectral analyses and chemical synthesis are presented.

Molecular mechanisms of aromatase inhibition by new A, D-ring modified steroids

A recent approach for treatment and prevention of estrogen-dependent breast cancer focuses on the inhibition of aromatase, the enzyme that catalyzes the final step of estrogen biosynthesis. Some synthetic steroids, such as formestane and exemestane, resembling the natural enzyme substrate androstenedione, revealed to be potent and useful aromatase inhibitors (AIs) and were approved for the treatment of estrogen-dependent breast cancer in postmenopausal women. Recently, we found that five newly synthesized steroids with chemical features in the A- and D-rings considered important for drug-receptor interaction efficiently inhibit aromatase derived from human placental microsomes. In this work, these steroids showed a similar pattern of anti-aromatase activity in several aromatase-expressing cell lines. 5alpha-androst-3-en-17-one and 3alpha,4alpha-epoxy-5alpha-androstan-17-one were revealed to be the most potent inhibitors. These compounds induced a time-dependent inhibition of aromatase, showing to be irreversible AIs. The specific interactions of these compounds with aromatase active sites were further demonstrated by site-directed mutagenesis studies and evaluated by computer-aided molecular modeling. Both compounds were able to suppress hormone-dependent proliferation of MCF-7aro cells in a dose-dependent manner. These findings are important for the elucidation of a structure-activity relationship on aromatase, which may help in the development of new AIs.

New steroidal aromatase inhibitors: suppression of estrogen-dependent breast cancer cell proliferation and induction of cell death

BACKGROUND

Aromatase, the cytochrome P-450 enzyme (CYP19) responsible for estrogen biosynthesis, is an important target for the treatment of estrogen-dependent breast cancer. In fact, the use of synthetic aromatase inhibitors (AI), which induce suppression of estrogen synthesis, has shown to be an effective alternative to the classical tamoxifen for the treatment of postmenopausal patients with ER-positive breast cancer. New AIs obtained, in our laboratory, by modification of the A and D-rings of the natural substrate of aromatase, compounds 3a and 4a, showed previously to efficiently suppress aromatase activity in placental microsomes. In the present study we have investigated the effects of these compounds on cell proliferation, cell cycle progression and induction of cell death using the estrogen-dependent human breast cancer cell line stably transfected with the aromatase gene, MCF-7 aro cells.

RESULTS

The new steroids inhibit hormone-dependent proliferation of MCF-7aro cells in a time and dose-dependent manner, causing cell cycle arrest in G0/G1 phase and inducing cell death with features of apoptosis and autophagic cell death.

CONCLUSION

Our in vitro studies showed that the two steroidal AIs, 3a and 4a, are potent inhibitors of breast cancer cell proliferation. Moreover, it was also shown that the antiproliferative effects of these two steroids on MCF-7aro cells are mediated by disrupting cell cycle progression, through cell cycle arrest in G0/G1 phase and induction of cell death, being the dominant mechanism autophagic cell death. Our results are important for the elucidation of the cellular effects of steroidal AIs on breast cancer.

Synthesis of some epoxy and/or N-oxy 17-picolyl and 17-picolinylidene-androst-5-ene derivatives and evaluation of their biological activity

Steroidal epoxy and/or N-oxy 17-picolyl and 17-picolinylidene-androst-5-ene derivatives have been prepared using 3beta,17beta-dihydroxy-17alpha-picolyl-androst-5-ene (1), 3beta-acetoxy-17-picolinylidene-androst-5-ene (2), and 3beta-hydroxy-17-picolinylidene-androst-5-ene (3) as synthetic precursors. The compounds 2 and/or 3 were reacted with m-chloroperoxybenzoic acid (MCPBA). The compounds synthesized from 2 were 17-picolinylidene-N-oxide 4, 5alpha,6alpha-epoxy and 5beta,6beta-epoxy-17-picolinylidene-N-oxide 5 and 6, and 5alpha,6alpha:17alpha,20alpha- and 5beta,6beta:17alpha,20alpha-diepoxy-N-oxide 7 and 8. Starting from compound 3, a mixture of 5alpha,6alpha-epoxy and 5beta,6beta-epoxy-17-picolinylidene 9 and 10, 5alpha,6alpha-epoxy and 5beta,6beta-epoxy-17-picolinylidene-N-oxide 11 and 12, and 5alpha,6alpha:17alpha,20alpha- and 5beta,6beta:17alpha,20alpha-diepoxy-N-oxide 13 and 14 were obtained. From compounds 15 and 18, obtained from 1 and 3 by the Oppenauer oxidation, the 4alpha,5alpha-epoxy and 4beta,5beta-epoxy derivatives 16, 17 and 20, 21 were prepared by oxidation with 30% H(2)O(2). Oxidation of 18 with MCPBA yielded only the N-oxide 19. The structures of compounds 15 and 18 were proved by the X-ray analysis. Compounds 1-6, 9, 15, 17, 18, and 21 were tested on activity against the enzyme aromatase. Antitumor activity against three tumor cell lines (human breast adenocarcinoma ER+, MCF-7, human breast adenocarcinoma ER-, MDA-MB-231, and prostate cancer PC3) was evaluated. Three tested compounds (1, 4, and 19) showed strong activity against PC3, the IC(50) values being in the range 0.55-10microM, whereas compound 17 showed strong activity against MDA-MB-231 (IC(50) 10.4microM).

Synthesis and evaluation of new 6-hydroximinosteroid analogs as cytotoxic agents

Taking into account the structural requirements for cytotoxicity, several new hydroximinosteroid derivatives have been prepared and evaluated for their cytotoxic activity against A-549, H116, PSN1, and T98G cultured tumor cell lines in order to obtain further information on the potential pharmacophoric core of this type of compound. The influence of the oxygenated position in the A ring, the presence of an additional oxygenated position at C-7 and C-16, and a fluorinated position at C-5 were considered in order to study the structure-activity relationships. The results reveal the importance of oxygenated positions in the A ring (e.g., 4,5-epoxide showed an IC50 value against HCT-116 under micromolar level) for an increase in cytotoxic activity in this type of compound. Furthermore, they showed an important selectivity toward colon tumor line (HCT-116).

Structure−Activity Relationships of New A,D-Ring Modified Steroids as Aromatase Inhibitors: Design, Synthesis, and Biological Activity Evaluation

Inhibition of aromatase is an efficient approach for the prevention and treatment of breast cancer. New A,D-ring modified steroid analogues of formestane and testolactone were designed and synthesized and their biochemical activity was investigated in vitro in an attempt to find new aromatase inhibitors and to gain insight into their structure-activity relationships (SAR). All compounds tested were less active than formestane. However, the 3-deoxy steroidal olefin 3a and its epoxide derivative 4a proved to be strong competitive aromatase inhibitors (K(i) = 50 and 38 nM and IC50 = 225 and 145 nM, respectively). According to our findings, the C-3 carbonyl group is not essential for anti-aromatase activity, but 5alpha-stereochemistry and some planarity in the steroidal framework is required. Furthermore, modification of the steroidal cyclopentanone D-ring, by construction of a delta-lactone six-membered ring, decreases the inhibitory potency. From the results obtained, it may be concluded that the binding pocket of the active site of aromatase requires planarity in the region of the steroid A,B-rings and the D-ring structure is critical for the binding.