Biochemical and biological evaluation of novel potent coumarin inhibitor of 17β-HSD type 1

17β-Hydroxysteroid dehydrogenases types 1 and 2: Enzymatic assays based on radiometric and mass-spectrometric detection

The 17β-hydroxysteroid dehydrogenase type 1 (HSD17B1) has a key role in estrogen biosynthesis as it catalyzes the reduction of estrone to the most potent estrogen, estradiol. Estradiol has a high affinity for estrogen receptors and thus stimulates their transactivation, which leads to cell proliferation and numerous other effects. HSD17B2 catalyzes the oxidation of estradiol to the less potent estrone, thereby decreasing estrogen receptor activation, which results in reduction of estrogen-associated effects. HSD17B1 and HSD17B2 overexpressing E.coli homogenates or recombinant enzymes can be used for screening and development of drugs against various pathologies such as cancer, endometriosis or osteoporosis. Here we describe the preparation of HSD17B1 and HSD17B2 bacterial homogenates and purified recombinant HSD17B1 protein as enzyme sources as well as enzymatic assays based on radiometric and mass-spectrometric detection for enzyme characterization.

Reductive 17beta-hydroxysteroid dehydrogenases which synthesize estradiol and inactivate dihydrotestosterone constitute major and concerted players in ER+ breast cancer cells

The reductive 17β-hydroxysteroid dehydrogenases which catalyze the last step in estrogen activation for estrogen dependent breast cancer cells were studied. Their biological function and the effects of their knockdown for cancer cell proliferation were demonstrated. The multidisciplinary study involves enzyme catalysis, sex-hormone and cell cycle regulation, as well as cell proliferation in breast cancer cells. Reductive 17β-HSD1, -7 and -12 were studied in the main breast cancer epithelial cells MCF-7 and T47D. Modification of estradiol and 5α-dihydrotestosterone concentrations was monitored by ELISA assay while corresponding cell viability measured by MTT assay. Cell cycle was determined by flow cytometry. Dual activity of estradiol activation and 5α-dihydrotestosterone reduction by 17β-HSD1 and -7 was critical for breast cancer cell (T47D and MCF-7) viability. Cell viability was decreased by 35.8% ± 1.6% in T47D cells after simultaneously knocking down 17β-HSD1 and -7. MCF-7 cell viability was decreased by 29.3% ± 4.2% using a combination of siRNAs and inhibitors. By knocking down 17β-HSD7, we have provided the first demonstration of the significant role of this enzyme in the stimulation of breast cancer cell viability as a result of its high activity on androgen reduction with positive feedback on estradiol production. A further decrease in cell viability was not observed with additional knockdown of 17β-HSD12 after 17β-HSD1 and 7. Breast cancer cell cycle progression was impeded to enter the S phase from G0-G1 after knocking down 17β-HSD1 and -7. In summary, this is the first demonstration that the dual activity in estrone activation and 5α-dihydrotestosterone reduction are the functional basis of reductive 17β-HSDs in breast cancer cells. 17β-HSD1 and -7 are principal reductive 17β-HSDs and major players in the viability of estrogen-dependent breast cancer cells. Combined targeting of these enzymes may be potential for molecular therapy of such cancer.

Cysteine-10 on 17 β -Hydroxysteroid Dehydrogenase 1 Has Stabilizing Interactions in the Cofactor Binding Region and Renders Sensitivity to Sulfhydryl Modifying Chemicals

17β-Hydroxysteroid dehydrogenase type 1 (17β-HSD1) catalyzes the conversion of estrone to the potent estrogen estradiol. 17β-HSD1 is highly expressed in breast and ovary tissues and represents a prognostic marker for the tumor progression and survival of patients with breast cancer and other estrogen-dependent tumors. Therefore, the enzyme is considered a promising drug target against estrogen-dependent cancers. For the development of novel inhibitors, an improved understanding of the structure-function relationships is essential. In the present study, we examined the role of a cysteine residue, Cys¹⁰, in the Rossmann-fold NADPH binding region, for 17β-HSD1 function and tested the sensitivity towards sulfhydryl modifying chemicals. 3D structure modeling revealed important interactions of Cys¹⁰ with residues involved in the stabilization of amino acids of the NADPH binding pocket. Analysis of enzyme activity revealed that 17β-HSD1 was irreversibly inhibited by the sulfhydryl modifying agents N-ethylmaleimide (NEM) and dithiocarbamates. Preincubation with increasing concentrations of NADPH protected 17β-HSD1 from inhibition by these chemicals. Cys¹⁰Ser mutant 17β-HSD1 was partially protected from inhibition by NEM and dithiocarbamates, emphasizing the importance of Cys¹⁰ in the cofactor binding region. Substitution of Cys¹⁰ with serine resulted in a decreased protein half-life, without significantly altering kinetic properties. Despite the fact that Cys¹⁰ on 17β-HSD1 seems to have limited potential as a target for new enzyme inhibitors, the present study provides new insight into the structure-function relationships of this enzyme.

Intratumoral localization and activity of 17β-hydroxysteroid dehydrogenase type 1 in non-small cell lung cancer: a potent prognostic factor

BACKGROUND

Estrogens were recently demonstrated to be synthesized in non-small cell lung carcinomas (NSCLCs) via aromatase activity and aromatase inhibitor (AI) did suppressed estrogen receptor (ER) positive NSCLC growth. However, other enzymes involved in intratumoral production and metabolism of estrogens, i.e. 17β-hydroxysteroid dehydrogenases (i.e. 17βHSD1 and 17βHSD2) and others have not been studied. Therefore, in this study, we examined the clinical/ biological significance of 17β-hydroxysteroid dehydrogenases in NSCLCs.

METHODOLOGY

Archival materials obtained from 103 NSCLC patients were immunohistochemically evaluated using anti-17βHSD1 and anti-17βHSD2 antibodies. The findings of immunohistochemistry were then correlated with intratumoral estrone (E1) and estradiol (E2) concentration, clinicopathological factors and overall survival of the patients. We further employed NSCLC cell lines, A549 and LK87 to study the functional significance of 17βHSD1, in vitro.

RESULTS

A higher 17βHSD1 immunoreactivity tended to be positively associated with aromatase (p=0.057) and tumor stage (p=0.055) whereas a higher 17βHSD2 immunoreactivity was positively associated with a squamous cell and adenosquamous cell carcinomas subtypes (p=0.031), tumor stage (p=0.004), T factor of TNM classification (p=0.010), maximum tumor diameter (p=0.002) and tended to be associated with N factor of TMN classification (p=0.065). A higher 17βHSD1 immunoreactivity was also significantly associated with lower intratumoral E1 concentration (p=0.040) and a higher intratumoral E2/E1 concentration ratio (p=0.028). On the other hand a higher 17βHSD2 immunoreactivity was significantly associated with higher intratumoral E1 concentration (p=0.035). Results of multivariate regression analysis demonstrated an increased 17βHSD1 immunoreactivity in tumor cells as an independent negative prognostic factor (HR= 2.83, p=0.007). E1 treatment in 17βHSD1 positive NSCLC cells, A549 and LK87, resulted in E2 production (p<0.0001) and enhanced cell proliferation, which was abrogated effectively by 17βHSD1 siRNA knockdown (p<0.0001). In addition, aromatase inhibitor treatment resulted in 17βHSD1 up regulation in both A549 and LK87 cells.

CONCLUSION

Results of our present study suggest that 17βHSD1 may be considered an important prognostic factor in NSCLC patients and targeting 17βHSD1 activity may further improve the clinical response in estrogen responsive NSCLC patients.

Pharmacological Evaluation and Docking Studies of 3-Thiadiazolyl- and Thioxo-1,2,4-triazolylcoumarin Derivatives as Cholinesterase Inhibitors

Inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) is considered a promising strategy for the treatment of Alzheimer's disease (AD). This research project aims to provide a comprehensive knowledge of newly synthesized coumarin analogues with anti-AD potential. In the present work a series of 3-thiadiazolyl- and thioxo-1,2,4-triazolylcoumarins derivatives were designed, synthesized, and tested as potent inhibitors of cholinesterases. These compounds were assayed against AChE from electrophorus electricus and rabbit; and BChE from horse serum and rabbit by Ellman's method using neostigmine methylsulphate and donepezil as reference drugs. Some of the assayed compounds proved to be potent inhibitors of AChE and BChE with K_i values in the micromolar range. 4b was found to be the most active compound with K_i value 0.028 ± 0.002 μM and higher selectivity for AChE/BChE. The ability of 4b to interact with AChE was further confirmed through computational studies, in which a primary binding was proved to occur at the active gorge site, and a secondary binding was revealed at the peripheral anionic site. Structure activity relationships of prepared compounds were also discussed.

Coumarin polysulfides inhibit cell growth and induce apoptosis in HCT116 colon cancer cells

Coumarins and coumarin derivatives as well as diallyl polysulfides are well known as anticancer drugs. In order to find new drugs with anticancer activities, we combined coumarins with polysulfides in the form of di-coumarin polysulfides. These novel compounds were tested in the HCT116 colorectal cancer cell line. It turned out that they reduced cell viability of cancer cells in a time and concentration dependent manner. Cells tested with these coumarin polysulfides accumulate in the G(2)/M phase of the cell cycle and finally they go into apoptosis. A decrease in bcl-2 level, and increase in the level of bax, cytochrome c release into the cytosol, cleavage of caspase 3/7and PARP suggested that coumarin polysulfides induced the intrinsic pathway of apoptosis. Comparison of these new coumarin compounds with the well known diallyl polysulfides revealed that the coumarin disulfides were more active than the corresponding diallyl disulfides. The activities of the coumarin tetrasulfides and the corresponding diallyl tetrasulfides are similar. The novel coumarin compounds regulated the phosphatase activity of the cell cycle regulating cdc25 family members, indicating that these phosphatases are implicated in the induction of cell cycle arrest and possibly in apoptosis induction as well. In addition, coumarin polysulfides also down-regulated the level of cdc25C, which also contributed to the arrest in the G(2)-phase of the cell cycle.