Novel mitochondrial and DNA damaging fluorescent Calix[4]arenes bearing isatin groups as aromatase inhibitors: Design, synthesis and anticancer activity.

Breast cancer causes a high rate of mortality all over the world. Therefore, the present study focuses on the anticancer activity of new lower rim-functionalized calix[4]arenes integrated with isatin and the p-position of calixarenes with 1,4-dimethylpyridinium iodine against various human cancer cells such as MCF-7 and MDA-MB-231 breast cancer cell lines, as well as the PNT1A healthy epithelial cell line. It was observed that compound 6c had the lowest values in MCF-7 (8.83 µM) and MDA-MB-231 (3.32 µM). Cell imaging and apoptotic activity studies were performed using confocal microscopy and flow cytometry, respectively. The confocal imaging studies with 6c showed that the compound easily entered the cell, and it was observed that 6c accumulated in the mitochondria. The Comet assay test was used to detect DNA damage of compounds in cells. It was found that treated cells had abnormal tail nuclei and damaged DNA structures compared with untreated cells. In vitro human aromatase enzyme inhibition profiles showed that compound 6c had a remarkable inhibitory effect on aromatase. Compound 6c displayed a significant inhibition capacity on aromatase enzyme with the IC50 value of 0.104 ± 0.004 µM. Thus, not only the anticancer activity of the new fluorescent derivatives, which are the subject of this study, but the aromatase inhibitory profiles have also been proven.

New 1,2,3-triazole/1,2,4-triazole hybrids linked to oxime moiety as nitric oxide donor selective COX-2, aromatase, B-RAFV600E and EGFR inhibitors celecoxib analogs: design, synthesis, anti-inflammatory/anti-proliferative activities, apoptosis and molecular modeling study.

A new series of bis-triazole 19a-l was synthesised for the purpose of being hybrid molecules with both anti-inflammatory and anti-cancer activities and assessed for cell cycle arrest, NO release. Compounds 19c, 19f, 19h, 19 l exhibited COX-2 selectivity indexes in the range of 18.48 to 49.38 compared to celecoxib S.I. = 21.10), inhibit MCF-7 with IC50 = 9-16 µM compared to tamoxifen (IC50 = 27.9 µM). and showed good inhibitory activity against HEP-3B with IC50 = 4.5-14 µM compared to sorafenib (IC50 = 3.5 µM) (HEP-3B). Moreover, derivatives 19e, 19j, 19k, 19 l inhibit HCT-116 with IC50 = 5.3-13.7 µM compared to 5-FU with IC50 = 4.8 µM (HCT-116). Compounds 19c, 19f, 19h, 19 l showed excellent inhibitory activity against A549 with IC50 = 3-4.5 µM compared to 5-FU with IC50 = 6 µM (A549). Compounds 19c, 19f, 19h, 19 l inhibit aromatase (IC50 of 22.40, 23.20, 22.70, 30.30 µM), EGFR (IC50 of 0.112, 0.205, 0.169 and 0.066 µM) and B-RAFV600E (IC50 of 0.09, 0.06, 0.07 and 0.05 µM).

New functionalized 6-thienylpyrimidine-5-carbonitriles as antiproliferative agents against human breast cancer cells.

6-Thienylpyrimidine-5-carbonitrile derivatives were synthesized and screened for their in vitro antiproliferative activities against two human breast cancer cell lines in comparison to 5-fluorouracil as a reference. Compounds 2, 3a-c, and 6b evolved as the most active congeners against both cell lines, while others showed selectivity for only one cell line. Compound 2 exerted its effect through inhibition of the epidermal growth factor receptor (EGFR), while 6b showed less aromatase inhibitory activity than letrozole. The rest of the tested compounds did not show significant inhibition, and it can be assumed that they exert their antiproliferative activity through different target mechanisms. In addition, caspase-9 protein activation assays, cell cycle analysis using flow cytometry, and annexin V-fluorescein isothiocyanate-propidium iodide (FITC/PI) dual staining assays were performed for the most active compounds. All the tested compounds were found to be potent pyrimidine derivatives able to initiate apoptosis in MCF-7 and MDA-MB-231 cells.

Impact of aromatase inhibitor treatment on global gene expression and its association with antiproliferative response in ER+ breast cancer in postmenopausal patients.

BACKGROUND: Endocrine therapy reduces breast cancer mortality by 40%, but resistance remains a major clinical problem. In this study, we sought to investigate the impact of aromatase inhibitor (AI) therapy on gene expression and identify gene modules representing key biological pathways that relate to early AI therapy resistance. METHODS: Global gene expression was measured on pairs of core-cut biopsies taken at baseline and at surgery from 254 patients with ER-positive primary breast cancer randomised to receive 2-week presurgical AI (n = 198) or no presurgical treatment (control n = 56) from the POETIC trial. Data from the AI group was adjusted to eliminate artefactual process-related changes identified in the control group. The response was assessed by changes in the proliferation marker, Ki67. RESULTS: High baseline ESR1 expression associated with better AI response in HER2+ tumours but not HER2- tumours. In HER2- tumours, baseline expression of 48 genes associated with poor antiproliferative response (p < 0.005) including PERP and YWHAQ, the two most significant, and the transcription co-regulators (SAP130, HDAC4, and NCOA7) which were among the top 16 most significant. Baseline gene signature scores measuring cell proliferation, growth factor signalling (ERBB2-GS, RET/GDNF-GS, and IGF-1-GS), and immune activity (STAT1-GS) were significantly higher in poor AI responders. Two weeks of AI caused downregulation of genes involved in cell proliferation and ER signalling, as expected. Signature scores of E2F activation and TP53 dysfunction after 2-week AI were associated with poor AI response in both HER2- and HER2+ patients. CONCLUSIONS: There is a high degree of heterogeneity in adaptive mechanisms after as little as 2-week AI therapy; however, all appear to converge on cell cycle regulation. Our data support the evaluation of whether an E2F signatures after short-term exposure to AI may identify those patients most likely to benefit from the early addition of CDK4/6 inhibitors. TRIAL REGISTRATION: ISRCTN, ISRCTN63882543, registered on 18 December 2007.

Aromatase inhibition by 2-methyl indole hydrazone derivatives evaluated via molecular docking and in vitro activity studies.

A causal association is reported between prolonged exposures to elevated levels of estrogen and breast cancer. Therefore inhibiting aromatase (CYP19A), which catalyses the conversion of androgens to estrogens, is an important approach in prevention and treatment of estrogen receptor positive (ER+) breast cancer. Melatonin, a natural indolic hormone, is reported to prevent free radical induced carcinogenesis and block local estrogen synthesis in breast tissue via aromatase inhibition. However several features of melatonin limit its therapeutic use. In the present study aromatase inhibiting potential of 2-methyl indole hydrazones are investigated, and compared with melatonin, by two in vitro models; a cell-free assay using a fluorescence substrate and a cell-based assay where cell proliferation was determined in ER + human breast cancer cells (MCF-7 BUS) in the absence of estrogen and the presence of testosterone. Aromatase inhibitory effect is also explored by molecular modelling studies. In biological activity assays monochloro substituted indole hydrazones were found to have stronger aromatase inhibitory activity among all tested derivatives and were more active than melatonin. This finding is further confirmed by molecular modelling. These results may be useful in the design and synthesis of novel melatonin analogues with higher inhibitory potency against aromatase.

Innovative selection approach for a new antifungal agent mefentrifluconazole (Revysol®) and the impact upon its toxicity profile.

Mefentrifluconazole (trade name: Revysol®) is an agrochemical active ingredient from the new sub-class of isopropanol-triazole fungicides, with high selective fungicide activity. A full program of toxicity testing conducted according to OECD guidelines has shown mefentrifluconazole (MFZ) to be non-genotoxic and non-carcinogenic. Repeated dose studies in rats, mice and dogs identified the liver as the main target organ. Prenatal developmental toxicity studies in rats and rabbits did not indicate treatment-related embryofetal toxicity or teratogenicity up to the highest dose levels tested. In a two-generation dietary study in rats, the high dose level resulted in reduced food consumption and body weight gain throughout the dosing-period. Mating performance and fertility, estrous cycles, gestation length and pre-and post-natal survival of offspring were essentially unaffected and there was no evidence of masculinization of female pups or feminization of male pups. The screening strategy that led to the selection of MFZ was aimed to identify candidates with both high fungicidal activity and minimal likelihood of adverse side effects thought to arise from aromatase inhibition. The success of the selection strategy has been illustrated for MFZ by the absence in toxicity studies of effects that would indicate an endocrine disrupting potential.

Behavioral evidence for sex steroids hypersensitivity in castrated male canaries.

In seasonally breeding songbirds such as canaries, singing behavior is predominantly under the control of testosterone and its metabolites. Short daylengths in the fall that break photorefractoriness are followed by increasing daylengths in spring that activate singing via both photoperiodic and hormonal mechanisms. However, we observed in a group of castrated male Fife fancy canaries maintained for a long duration under a short day photoperiod a large proportion of subjects that sang at high rates. This singing rate was not correlated with variation in the low circulating concentrations of testosterone. Treatment of these actively singing castrated male canaries with a combination of an aromatase inhibitor (ATD) and an androgen receptor blocker (flutamide) only marginally decreased this singing activity as compared to control untreated birds and did not affect various measures of song quality. The volumes of HVC and of the medial preoptic nucleus (POM) were also unaffected by these treatments but were relatively large and similar to volumes in testosterone-treated males. In contrast, peripheral androgen-sensitive structures such as the cloacal protuberance and syrinx mass were small, similar to what is observed in castrates. Together these data suggest that after a long-term steroid deprivation singing behavior can be activated by very low concentrations of testosterone. Singing normally depends on the activation by testosterone and its metabolites of multiple downstream neurochemical systems such as catecholamines, nonapeptides or opioids. These transmitter systems might become hypersensitive to steroid action after long term castration as they probably are at the end of winter during the annual cycle in seasonally breeding temperate zone species.

A review of the effects of azole compounds in fish and their possible involvement in masculinization of wild fish populations.

Endocrine-mediated effects in fish populations have been widely documented. Most attention has been focused on feminization caused by estrogenic substances, but this paper reviews evidence for the effects of a group of fungicides and pharmaceuticals, the azoles, which have been reported to cause masculinization in fish. The paper considers information from laboratory studies on the effects of azole compounds on fish endocrinology, and on the potential existence of such effects in wild fish. The occurrence of some azoles in effluents and surface waters has also been briefly reviewed. Under laboratory conditions, many azoles are able to cause masculinization or defeminization in fish by inhibition of the P450 enzyme aromatase (CYP19). However, in no case where such effects have been observed in the field has a link been established with this group of substances. In most instances, other more convincing explanations have been proposed. Peak concentrations of some azoles in surface waters can approach those which, under continuous long-term exposure in the laboratory, might lead to some aromatase inhibition. However, available data on exposure and effects provide reassurance that the concentrations of azoles found in surface waters are too low to cause adverse effects in fish by interference with their endocrine system. Compared to the widespread observations of feminization and estrogenic effects in (male) fish, there are relatively few papers describing masculinization or defeminization in (female) wild fish populations, suggesting that this is quite a rare phenomenon. The significance of this result is emphasized by the fact that fish are among the best studied organisms in the environment.

Biotransformation of metenolone acetate and epiandrosterone by fungi and evaluation of resulting metabolites for aromatase inhibition.

The present study describes the microbial transformation of anabolic drugs, metenolone acetate (1), and epiandrosterone (6). Three new metabolites, 6ß,17ß-dihydroxy-1-methyl-3-oxo-5α-androst-1-en (2), 5α,15α-dihydroxy-1-methyl-3-oxo-1-en-17-yl acetate (3), 15ß-hydroxy-1-methyl-3-oxo-5α-androst-1,4-dien-17-yl acetate (4), and a known metabolite, 17ß-hydroxy-1-methyl-4-androstadiene-3-one (5) were obtained by biotransformation of metenolone acetate (1) via Trametes hirsuta mushroom. Metabolites 7, and 8 were obtained from the incubation of epiandrosterone (6) with Cunninghamella blakesleeana. While bioconversion of compound 6 with Aspergillus alliaceus yielded seven known metabolites 9-15. Modern spectroscopic techniques were employed for the structure elucidation of biotransformed products. All compounds were evaluated for their aromatase inhibitory activity. Among them, new metabolite 3 exhibited a significant human placental aromatase activity with an IC50 = 19.602 ± 0.47 µM, as compared to standard anti-cancer drug exemestane (IC50 = 0.232 ± 0.031 µM), whereas, metabolite 5 (IC50 = 0.0049 ± 0.0032 µM) exhibited a very potent activity. While substrate 6, and metabolites 2, 7, and 9 were found inactive. Aromatase plays a key role in the biosynthesis of estrogen hormone, responsible for cancer cell proliferation. Its inhibition is therefore targeted for the treatment of ER + breast cancer. Further structural modifications (lead optimization) of compound 3 can lead to more potent aromatase inhibition for possible treatment of ER + breast cancer.

Combined aromatase, CDK4/6 and PI3K blockade using letrozole/abemaciclib/LY3023414 in endometrial cancer.

Several lines of preclinical evidence indicate that combining PI3K and CDK4/6 inhibitors may further enhance the efficacy of hormonal therapy by overcoming de novo and acquired resistance to PI3K and CDK4/6 blockade. We evaluated the combination of abemaciclib, letrozole and LY3023414 (an orally available, selective inhibitor of the class I PI3K isoforms and mTORC1/2) in recurrent endometrial cancer (EC). This study was terminated prematurely after 5 patients initiated protocol therapy due to discontinuation of further development of LY3023414. We report our findings from these patients, including one with recurrent endometrioid EC with AKT1, CTNNB1 and ESR1 hotspot mutations who had previously progressed through letrozole/everolimus and achieved a partial response to letrozole/abemaciclib/LY3023414.

Acute Aromatase Inhibition Impairs Neural and Behavioral Auditory Scene Analysis in Zebra Finches.

Auditory perception can be significantly disrupted by noise. To discriminate sounds from noise, auditory scene analysis (ASA) extracts the functionally relevant sounds from acoustic input. The zebra finch communicates in noisy environments. Neurons in their secondary auditory pallial cortex (caudomedial nidopallium, NCM) can encode song from background chorus, or scenes, and this capacity may aid behavioral ASA. Furthermore, song processing is modulated by the rapid synthesis of neuroestrogens when hearing conspecific song. To examine whether neuroestrogens support neural and behavioral ASA in both sexes, we retrodialyzed fadrozole (aromatase inhibitor, FAD) and recorded in vivo awake extracellular NCM responses to songs and scenes. We found that FAD affected neural encoding of songs by decreasing responsiveness and timing reliability in inhibitory (narrow-spiking), but not in excitatory (broad-spiking) neurons. Congruently, FAD decreased neural encoding of songs in scenes for both cell types, particularly in females. Behaviorally, we trained birds using operant conditioning and tested their ability to detect songs in scenes after administering FAD orally or injected bilaterally into NCM. Oral FAD increased response bias and decreased correct rejections in females, but not in males. FAD in NCM did not affect performance. Thus, FAD in the NCM impaired neuronal ASA but that did not lead to behavioral disruption suggesting the existence of resilience or compensatory responses. Moreover, impaired performance after systemic FAD suggests involvement of other aromatase-rich networks outside the auditory pathway in ASA. This work highlights how transient estrogen synthesis disruption can modulate higher-order processing in an animal model of vocal communication.

Bioactive compounds from four Indian medicinal plants have different potency to induce sex reversal in Nile tilapia: A chromatographic, molecular docking and in silico analysis.

ETHNOPHARMACOLOGICAL RELEVANCE: Herbal plants such as Basella alba (Family: Basellaceae), Tribulus terrestris (Family: Zygophyllaceae), Asparagus racemosus (Family: Asparagaceae) and Mucuna pruriens (Family: Fabaceae) are mentioned in Indian traditional system of medicine Ayurveda to possess androgenic activity and increase male virility. The plants have been reported to improve testosterone level and sperm production in experimental male rodents as well. AIM OF THE STUDY: Male Nile tilapias grow more quickly than females and hence are preferred for monosex Nile tilapia culture. Ethanol extracts of B. alba leaves (EB) and T. terrestris seeds (ET), and methanol extract of A. racemosus roots (MA) and M. pruriens seeds (MM) were found effective to induce masculinization in Nile tilapia. The present study intends to evaluate the anti-aromatase activity of EB, ET, MA and MM, to identify the androgenic bioactive compounds in the extracts, and to determine their pharmacokinetics. The study may validate the use of those plant extracts and their major bioactive phytoconstituents in the field of aquaculture and pharmaceuticals. MATERIALS AND METHODS: The four crude plant extracts were first fractioned through column and thin layer chromatography (TLC). Three days old Nile tilapia juveniles (mean weight 0.025 ± 0.009g; mean length 12.50 ± 0.12 mm; n = 50 fish/replicate, 3 replicates/treatment) were then fed diets fortified with the obtained fractions for 30 days. After 30 days, fish were sacrificed and gonad aromatase mRNA expression, and 11-ketotestosterone (11-KT) and estradiol (E2) levels were measured. Fractions yielding the highest male percentage for each plant were subject to gas chromatography-mass spectrometry (GC-MS) analysis. The in silico docking and SwissADME study were conducted with the components showing higher peak percentage in chromatogram. RESULTS: After column chromatography and TLC analysis, EB, ET, MM and MA yielded 6 (EB1 - EB6), 8 (ET1- ET8), 14 (MM1-MM14) and 5 (MA1- MA5) fractions, respectively. Fish fed EB2, ET2, MA2 and MM13 fraction fortified diets showed significantly (p < 0.05) higher male percentage (92.32%-98.39%) compared to other treatment groups. EB2, ET2, MA2 and MM13 fed fish showed significantly (p < 0.05) higher 11-KT level compared to control male (+247.52 - +397.76%) and lower E2 level compared to control female (-95.92% to -90.65%). Aromatase mRNA expression was significantly (p < 0.05) down-regulated by all these four fractions (-1.32 to -5.65 fold) with respect to control female. GC-MS analysis revealed the presence of 1-Octadecene (OD) in EB2, Phenol, 2,4-bis(1,1-dimethylethyl) (PD) in ET2 and MA2, 9,12-Octadecadienoic acid (Z,Z)- (ODDA) in MM13. In silico molecular docking indicated that PD is more effective than ODDA and OD to inhibit aromatase. In addition, PD showed better pharmacokinetics and more drug-likeness compared to OD and ODDA in SwissADME analysis. CONCLUSION: The present results indicate that ET and MA are more potent to produce all-male tilapia by means of aromatase inhibition. PD can be an ideal compound to achieve masculinization in Nile tilapia through dietary administration, but further investigation is required.

Milicia excelsa (Moraceae) reversed the effects of letrozole-induced aromatase inhibition in rats with polycystic ovary syndrome.

OBJECTIVES: Polycystic ovary syndrome (PCOS) is an endocrinopathy affecting 5-20% of women of childbearing age. There is no single drug for the treatment of PCOS and current therapies have significant side effects. This study evaluated the ability of Milica excelsa to improve PCOS symptoms in rats. METHODS: Induction of PCOS was achieved using letrozole (a reversible aromatase inhibitor; 1 mg/kg; given orally for 21 days). From day 22, PCOS rats received the aqueous extract of M. excelsa roots (14 and 140 mg/kg). Clomiphene citrate (1 mg/kg) was administered to the positive control. The negative and the normal controls received the vehicle (5% DMSO). Treatments were given orally for 7 or 14 days. Vaginal smears were scrutinized daily during the experiment. Body weight was measured hebdomadal. Animals were sacrificed after the two treatment periods for biochemical and histological analyses. RESULTS: Aromatase inhibition caused hyperandrogenism (p<0.001), overweight (p<0.001) and fat accumulation (p<0.001). It also blocked the estrous cycle at the diestrus phase and altered ovarian dynamics as evidenced by the accumulation of cystic (p<0.001) and atretic (p<0.001) follicles. In contrast, M. excelsa induced weight loss (p<0.001), reduction in fat weight (p<0001), and lower serum androgen and LH levels (p<0.001). It also restored the estrous cycle and improved ovarian dynamics by increasing the amount of Graafian follicles (p<0.001) and corpora lutea (p<0.001), and decreasing that of cystic and atretic follicles (p<0.001). CONCLUSIONS: Milica excelsa corrected hyperandrogenism and overweight in PCOS animals, and reduced cyst formation and follicle atresia in their ovaries.

Novel oxadiazole-thiadiazole derivatives: synthesis, biological evaluation, and in silico studies.

In the search for new anticancer agents, we synthesized a new series of thiazole derivatives carried on thiadiazole-oxadiazole hybrid. Final compounds (5a-5i) were analyzed via 1H NMR, 13C NMR, and HRMS. The pharmacokinetic profile of the targeted compounds was predicted via in silico calculations. Their anticancer properties were determined using MTT method against MCF7 and A549 cell lines. Compounds 5a, 5b and 5c were found more active against MCF7 cells than A549 cells while they were not cytotoxic on L929 healthy cells. Generally, it can be summarized that acetamide moiety has a pivotal role in anticancer activity. For further studies, their aromatase inhibitory activity was evaluated. After determination all these features, the binding modes of the active compounds and the stability and relation of the ligand-enzyme complex were investigated using molecular docking and molecular dynamics simulation studies, respectively. In vitro and in silico studies suggest two important structure-activity relationship (SAR) points that at least one azole ring is essential, and if there is approximately 8.0 ± 0.5 Å distance between the H-bond rich zone of ligand and the heteroaryl ring system of ligand has a major impact on aromatase inhibitory activity. Compounds with small group substitution on thiazole are found potentially may be used for the treatment of anti-breast cancer orally.Communicated by Ramaswamy H. Sarma.

Advantages and Disadvantages of Two In Vitro Assays in Evaluating Aromatase Activity: "A Cell-Based and a Cell-Free Assay".

Objectives: Aromatase is an enzyme that catalyzes the conversion of androgens to estrogens. While inhibition of aromatase is a useful approach for treating breast cancer, it may also have toxicological consequences due to its endocrine disrupting/modulating effect. In this study, sensitivity and performance of two in vitro assays -a cell free and a cell-based- for evaluating aromatase activity were investigated by testing known aromatase inhibitors and partial validation of the methods was performed. Advantages and disadvantages of these methods are also discussed. Materials and Methods: Aromatase activity was evaluated via two in vitro models; direct measurement with a cell-free assay using a fluorescent substrate and recombinant human enzyme and indirect evaluation with a cell-based assay where cell proliferation was determined in estrogen receptor positive human breast cancer cells (MCF-7 BUS) in the absence of estrogen and the presence of testosterone. Results: In the cell-free direct measurement assay, reference compounds ketoconazole and aminoglutethimide have been shown to inhibit the aromatase enzyme with half-maximal inhibitory concentration (IC50) values concordant with literature. In cell-based indirect measurement assay, only ketoconazole dose-dependently inhibited cell proliferation with 3.47 x 10-7 M IC50. Inter-assay and intra-assay reproducibility of both methods was found to be within acceptable deviation levels. Conclusion: Both methods can be successfully applied. However, to evaluate the potential aromatase activity of the novel compounds in vitro, it seems better to perform both the cell-based and the cell-free assays that allows low-moderate biotransformation and eliminate cytotoxicity potential, respectively.

Synthesis of novel thiazolyl hydrazone derivatives as potent dual monoamine oxidase-aromatase inhibitors.

The inhibitory effects of 2-thiazolyl hydrazones on monoamine oxidase enzymes are known for a long time. In this study, a new series of 2-thiazolyl hydrazone derivatives were synthesized starting from 6-methoxy-2-naphthaldehyde. All of the synthesized compounds were investigated in terms of their monoamine oxidase (MAO) inhibitory effects and significant results were found. The results showed that compound 2j potently inhibited MAO-A and MAO-B, while compound 2t strongly and selectively inhibited MAO-B compared to standard drugs. Compounds 2k and 2q exhibited selective and satisfying inhibition on MAO-B. In the aromatase inhibition studies of the compounds, it was determined that compounds 2q and 2u had high inhibitory properties. Molecular docking studies on MAO-A, MAO-B, and aromatase enzymes were carried out for the aforementioned compounds. Additionally, molecular dynamics simulation was studied for compound 2q on MAO-B and aromatase complexes. Finally, the Field-based QSAR study was developed and the structure-activity relationship (SAR) was explained. For the first time, dual inhibitors on MAO and aromatase enzyme were investigated together. The aim of this approach is for finding the potential agents that do not cause the cognitive disorders and may even treat neurodegenerative symptoms, thus, the aim was reached successfully.

Ent-abietane diterpenoid lactone glycosides and a phenolic glycoside from Phlogacanthus pulcherrimus T. Anderson with cytotoxic and cancer chemopreventive activities.

Nine undescribed ent-abietane diterpenoid lactone glycosides, pulcherrimosides A-I, and a phenolic glycoside, phlogoside A, together with ten known compounds were isolated from the aerial parts of Phlogacanthus pulcherrimus T. Anderson. Their structures were established through spectral methods, especially 2D NMR and HRESIMS analyses, and by acid hydrolysis. The absolute configurations of pulcherrimosides A-I were determined through the interpretation of electronic circular dichroism (ECD) data. Some of the isolates were evaluated for their in vitro cytotoxic and cancer chemopreventive properties. Helioscopinolide A and 17-hydroxyhelioscopinolide A showed good cytotoxic activity against HeLa cells with IC50 values of 18.16 ± 0.58 and 16.60 ± 0.23 µM, respectively. Pulcherrimoside D inhibited superoxide anion radical formation in the xanthine/xanthine oxidase (XXO) assay with an IC50 value of 59.5 µM. Helioscopinolide A and pulcherrimoside D were strong aromatase inhibitors with IC50 values of 9.0 and 11.9 µM, respectively. Among the tested compounds, pulcherrimoside D was considered an interesting cancer chemopreventive agent for further study as it provided good activity in several in vitro cancer preventive assays and was not toxic to normal cells.

Regulation of aromatase expression: Potential therapeutic insight into breast cancer treatment.

Estrogen signaling has been implicated in hormone-dependent breast cancer which constitutes >75% of breast cancer diagnosis and other malignancies. Aromatase, the key enzyme involved in the synthesis of estrogen, is often dysregulated in breast cancers. This has led to the administration of aromatase-inhibitors (AIs), commonly used for hormone-dependent breast cancers. Unfortunately, the increasing development of acquired resistance to the current AIs and modulators of estrogen receptors, following initial disease steadiness, has posed a serious clinical challenge in breast cancer treatment. In this review we highlight historical and recent advances on the transcriptional and post-translational regulation of aromatase in both physiological and pathological contexts. We also discuss the different drug combinations targeting various tumor promoting cell signaling pathways currently being developed and tested both in laboratory settings and in the clinic.

Atalantiaphyllines A-G, prenylated acridones from Atalantia monophylla DC. and their aromatase inhibition and cytotoxic activities.

Seven previously undescribed acridones, named atalantiaphyllines A-G, along with twenty-six known compounds were isolated from the dichloromethane extracts of roots and stems of Atalantia monophylla DC. Their structures were elucidated by analysis of extensive NMR and HRMS data. Aromatase inhibition, cytotoxicity against MOLT-3, HepG2, A549 and HuCCA-1 cell lines and DPPH radical scavenging activity of these compounds were evaluated. Most of the tested acridones exhibited higher potency in inhibiting aromatase than the positive control, ketoconazole, with IC50 values in the range of 0.08-2.0 µM. In the cytotoxicity assay, cycloataphylline A, N-methylbuxifoliadine E and atalantiaphylline G were selectively cytotoxic against MOLT-3 cell line with IC50 values of 8.0, 5.4 and 9.8 µM, respectively, while only atalaphyllidine exhibited highest antioxidant activity as evaluated by DPPH free radical scavenging assay with an IC50 value of 22.4 µM.

Growth inhibitory efficacy and anti-aromatase activity of Tabebuia avellanedae in a model for post-menopausal Luminal A breast cancer.

Aromatase inhibitors (AIs) represent a treatment option for post-menopausal estrogen receptor-positive (ER+) breast cancer as monotherapy, or in combination with cyclin-dependent kinase 4/6 or mTOR inhibitors. Long-term treatment with these agents leads to dose-limiting toxicity and drug resistance. Natural substances provide testable alternatives to current therapy. Tabebuia avellanedae (TA) tree is indigenous to the Amazon rainforest. The inner bark of TA represents a medicinal dietary supplement known as Taheebo. Non-fractionated aqueous extract from TA is an effective growth inhibitor in the Luminal A and triple negative breast cancer models. The quinone derivative naphthofurandione (NFD) is a major bioactive agent in TA. The present study examined the efficacy of finely ground powder from the inner bark of TA, available under the name of Taheebo-NFD-Marugoto (TNM). The ER+ MCF-7 cells stably transfected with the aromatase gene MCF-7AROM represented a model for aromatase-expressing post-menopausal breast cancer. Anchorage-independent colony formation, cell cycle progression, pro-apoptotic caspase 3/7 activity, apoptosis-specific gene expression, aromatase activity and select estradiol (E2) target gene expression represented the mechanistic end points. Treatment of MCF-7AROM cells with TNM induced a dose-dependent reduction in E2-promoted anchorage-independent colony number. Mechanistic assays on TNM-treated MCF-7AROM cells demonstrated that TNM at a concentration of 10 µg (NFD content: 2 ng), induced S-phase arrest, increased pro-apoptotic caspase 3/7 activity, increased pro-apoptotic BAX and decreased anti-apoptotic BCL-2 gene expression, and inhibited aromatase activity. Additionally, TNM treatment downregulated ESR-1 (gene for ER-α), aromatase and progesterone gene expression and reduced mRNA levels of E2 target genes pS2, GRB2 and cyclin D1. Inhibition of aromatase activity, based on the NFD content of TNM was superior to the clinical AIs Letrozole and Exemestane. These data demonstrated the potential efficacy of TNM as a nutritional alternative for current therapy of aromatase positive, post-menopausal breast cancer.