Aromatase inhibitors: rationale and use in breast cancer

Synchronous Primary Metastatic Infra-Mammary Accessory Breast Cancer and Ipsilateral Breast Cancer: An Extremely Rare Case Report

Background: Accessory breast cancer cases are rarely reported in the literature. Of the reported cases, the predominantly available ones are those localized in the axillary region. Methods: We present here a very rare case of metastatic accessory breast cancer. It was located in the infra-mammary region (IMR). IMR accessory breast cancer is a rare form of breast cancer. Although ectopic nipples are occasionally found in the IMR, because of the lack of ductal tissue malignant changes, they are rare. Results: In our case, the primary tumor was localized in the congenital accessory breast tissue (ABT). It was recognized as invasive lobular accessory breast cancer cT3N1M0 with a second NST carcinoma, cT2N0M0, Stage IIA, in the ipsilateral breast. A multi-modal approach was applied. Adjuvant chemotherapy was carried out with epirubicin, cyclophosphamide, and paclitaxel, with post-chemotherapy ultrasound followed by right radical mastectomy. Adjuvant radiotherapy was given to our patient in the form of 25 fractions of 50 GY for 25 days, followed by hormonal treatment with Letrozole, 2.5 mg/day, to be continued for 5 years. Conclusions: our case demonstrates that since it is rare to find accessory breast cancer in the infra-mammary region, early identification and management with a multi-modal approach can lead to a successful patient outcome.

Modeling of Mouse Experiments Suggests that Optimal Anti-Hormonal Treatment for Breast Cancer is Diet-Dependent

Estrogen receptor positive breast cancer is frequently treated with anti-hormonal treatment such as aromatase inhibitors (AI). Interestingly, a high body mass index has been shown to have a negative impact on AI efficacy, most likely due to disturbances in steroid metabolism and adipokine production. Here, we propose a mathematical model based on a system of ordinary differential equations to investigate the effect of high-fat diet on tumor growth. We inform the model with data from mouse experiments, where the animals are fed with high-fat or control (normal) diet. By incorporating AI treatment with drug resistance into the model and by solving optimal control problems we found differential responses for control and high-fat diet. To the best of our knowledge, this is the first attempt to model optimal anti-hormonal treatment for breast cancer in the presence of drug resistance. Our results underline the importance of considering high-fat diet and obesity as factors influencing clinical outcomes during anti-hormonal therapies in breast cancer patients.

Extended adjuvant endocrine therapy for women with hormone receptor-positive early breast cancer: A meta-analysis with trial sequential analysis of randomized controlled trials

OBJECTIVES

The aim of the current study is to explore the association between extended adjuvant endocrine treatment and prognosis of women with hormone receptor-positive (HR+) early breast cancer.

METHODS

Databases including PubMed, Web of Science, Embase and the Cochrane Library databases were electronically searched to identify randomized controlled trials (RCTs) that reported extended endocrine therapy for women with HR+ early breast cancer. The retrieval time was limited from inception to September 2022. Two reviewers independently screened literature, extracted data, and assessed risk bias of included studies. Meta-analysis was performed by using R software Version 4.1.2 and STATA Version 12.0.

RESULTS

A total of 15 RCTs involving 29497 cases were included. The overall analysis showed that compared with the control, extended adjuvant endocrine therapy increased disease-free survival (DFS) (HR=0.814, 95% CI: 0.720-0.922, 95% PI: 0.556-1.194), overall survival (OS) (HR=0.885, 95% CI: 0.822-0.953, 95% PI: 0.771-1.035), relapse-free survival (RFS) (HR=0.833, 95% CI: 0.747-0.927, 95% PI: 0.575-1.159), distant metastatic-free survival (DMFS) (HR=0.824, 95% CI: 0.694-0.979, 95% PI: 0.300-2.089) and reduced new breast cancer cumulative incidence (NBCCI) (HR=0.484, 95% CI: 0.403-0.583, 95% PI: 0.359-0.654). For adverse events, extended adjuvant endocrine treatment was associated with a significantly higher risk of bone fracture (RR=1.446, 95% CI: 1.208-1.730, 95% PI: 1.154-1.854) and osteoporosis (RR=1.377, 95% CI: 1.018-1.862, 95% PI: 0.347-5.456).

CONCLUSION

Our study showed that extended adjuvant endocrine therapy increased DFS, OS, RFS, DMFS, the incidence of bone fracture and osteoporosis, and reduced NBCCI.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero, identifier (CRD42022351295).

Radionuclide-Based Imaging of Breast Cancer: State of the Art

Simple Summary

Breast cancer is one of the most commonly diagnosed malignant tumors, possessing high incidence and mortality rates that threaten women’s health. Thus, early and effective breast cancer diagnosis is crucial for enhancing the survival rate. Radionuclide molecular imaging displays its advantages for detecting breast cancer from a functional perspective. Noninvasive visualization of biological processes with radionuclide-labeled small metabolic compounds helps elucidate the metabolic state of breast cancer, while radionuclide-labeled ligands/antibodies for receptor-targeted radionuclide molecular imaging is sensitive and specific for visualization of the overexpressed molecular markers in breast cancer. This review focuses on the most recent developments of novel radiotracers as promising tools for early breast cancer diagnosis.

Abstract

Breast cancer is a malignant tumor that can affect women worldwide and endanger their health and wellbeing. Early detection of breast cancer can significantly improve the prognosis and survival rate of patients, but with traditional anatomical imagine methods, it is difficult to detect lesions before morphological changes occur. Radionuclide-based molecular imaging based on positron emission tomography (PET) and single-photon emission computed tomography (SPECT) displays its advantages for detecting breast cancer from a functional perspective. Radionuclide labeling of small metabolic compounds can be used for imaging biological processes, while radionuclide labeling of ligands/antibodies can be used for imaging receptors. Noninvasive visualization of biological processes helps elucidate the metabolic state of breast cancer, while receptor-targeted radionuclide molecular imaging is sensitive and specific for visualization of the overexpressed molecular markers in breast cancer, contributing to early diagnosis and better management of cancer patients. The rapid development of radionuclide probes aids the diagnosis of breast cancer in various aspects. These probes target metabolism, amino acid transporters, cell proliferation, hypoxia, estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), gastrin-releasing peptide receptor (GRPR) and so on. This article provides an overview of the development of radionuclide molecular imaging techniques present in preclinical or clinical studies, which are used as tools for early breast cancer diagnosis.

Celecoxib and dimethylcelecoxib block oxidative phosphorylation, epithelial-mesenchymal transition and invasiveness in breast cancer stem cells

BACKGROUND

Drug resistance and invasiveness developed by breast cancer stem cells (BCSC) are considered the major hurdles for successful cancer treatment. <P> Objective: As these two processes are highly energy-dependent, the identification of the main ATP supplier required for stem cell viability may result advantageous in the design of new therapeutic strategies to deter malignant carcinomas. <P> Methods: The energy metabolism (glycolysis and oxidative phosphorylation, OxPhos) was systematically analyzed by assessing relevant protein contents, enzyme activities and pathway fluxes in BCSC. Once identified the main ATP supplier, selective energy inhibitors and canonical breast cancer drugs were used to block stem cell viability and their metastatic properties. <P> Results: OxPhos and glycolytic protein contents, as well as HK and LDH activities were several times higher in BCSC than in their parental line, MCF-7 cells. However, CS, GDH, COX activities and both energy metabolism pathway fluxes were significantly lower (38-86%) in BCSC than in MCF-7 cells. OxPhos was the main ATP provider (>85%) in BCSC. Accordingly, oligomycin (a specific and potent canonical OxPhos inhibitor) and other non-canonical drugs with inhibitory effect on OxPhos (celecoxib, dimethylcelecoxib) significantly decreased BCSC viability, levels of epithelial-mesenchymal transition proteins, invasiveness, and induced ROS over-production, with IC50 values ranging from 1 to 20 µM in 24 h treatment. In contrast, glycolytic inhibitors (gossypol, iodoacetic acid, 3-bromopyruvate, 2-deoxyglucose) and canonical chemotherapeutic drugs (paclitaxel, doxorubicin, cisplatin) were much less effective against BCSC viability (IC50> 100 µM). <P> Conclusion: These results indicated that the use of some NSAIDs may be a promising alternative therapeutic strategy to target BCSC.

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.

New thieno[3,2-d]pyrimidine-based derivatives: Design, synthesis and biological evaluation as antiproliferative agents, EGFR and ARO inhibitors inducing apoptosis in breast cancer cells

An array of newly synthesized thieno[3,2-d]pyrimidine-based derivatives and thienotriazolopyrimidines hybridized with some pharmacophoric anticancer fragments were designed, synthesized and assessed for their in vitro antiproliferative activity against MCF-7 and MDA-MB-231 breast cancer cell lines using erlotinib and pictilisib as reference standards in the MTT assay. In general, many compounds were endowed with considerable antiproliferative activity (IC₅₀ = 0.43-1.31 µM). Some of the tested compounds, namely 3c, 5b, 5c, 9d, 10, 11b and 13 displayed remarkable antiproliferative activity against both cell lines. Meanwhile, compounds 2c-e, 3b, 4a, 5a, 9c and 15b showed noticeable selectivity against MCF-7 cells while compounds 2b, 3a, 4b, 6a-c, 7, 8, 9b and 12 exhibited considerable selectivity against MDA-MB-231 cells. Further mechanistic evidences for their anticancer activities were provided by screening the most potent compounds against MCF-7 and/or MDA-MB-231 cells for EGFR and ARO inhibitory activities using erlotinib and letrozole as reference standards respectively. Results proved that, in general, tested compounds were better EGFRIs than ARIs. In addition, significant overexpression in caspase-9 level in treated MCF-7 breast cell line samples was observed for all tested compounds with the 4-fluorophenylhydrazone derivative 2d exhibiting the highest activation. In treated MDA-MB-231 breast cell line samples, 11b was found to highly induce caspase-9 level thereby inducing apoptosis. Cell cycle analysis and Annexin V-FITC/PI assay were also assessed for active compounds where results indicated that all tested compounds induced preG1 apoptosis and cell cycle arrest at G2/M phase. Compound 9d, as an inhibitor of ARO, was observed to downregulate the downstream signaling proteins HSP27 and p-ERK in MCF-7 cells. Furthermore, compound 11b downregulated EGFR expression as well as the downstream signaling protein p-AKT. Docking experiments on EGFR and ARO enzymes supported their in vitro results. Thus, the thienotriazolopyrimidines 11b and 12 showing good EGFR inhibition and the thieno[3,2-d]-pyrimidine derivatives 3b and 9d, eliciting the best ARO inhibition activity, can be considered as new candidates as anti-breast cancer agents that necessitate further development.

A simple, precise, and sensitive HPLC method for quantification of letrozole in rat plasma: development, validation, and preclinical pharmacokinetics

A simple bioanalytical liquid chromatographic method was developed and validated to quantify letrozole (LTZ) in rat plasma. Protein precipitation using acidified chilled acetonitrile (containing 0.1% orthophosphoric acid) was used to extract LTZ from the plasma. Chromatographic separation was carried out on Kinetex C18 reverse phase (RP) column (250 mm × 4.6 mm i.d., 5 μm) using a mixture of 20 mM acetate buffer (pH 5.5) and acetonitirile (60:40 %v/v) eluting at 1.0 mL/min flow rate with the method responses measured at 240 nm. The optimized method was selective and established good linearity with recovery ranging between 91.16 and 99.44%. The validation experiments revealed that the method showed acceptable precision (2.61–7.48%) and accuracy (97.44–102.70%) and was found to be stable. The sensitivity of the method was demonstrated by the lowest concentration (LLOQ) detected at 75 ng/mL. Using the developed method, single-dose oral pharmacokinetics in Sprague-Dawley rats was carried out to successfully confirm the applicability of the method for the quantification of LTZ in biological matrix.

Comprehensive and Automated Linear Interaction Energy Based Binding-Affinity Prediction for Multifarious Cytochrome P450 Aromatase Inhibitors

Cytochrome P450 aromatase (CYP19A1) plays a key role in the development of estrogen dependent breast cancer, and aromatase inhibitors have been at the front line of treatment for the past three decades. The development of potent, selective and safer inhibitors is ongoing with in silico screening methods playing a more prominent role in the search for promising lead compounds in bioactivity-relevant chemical space. Here we present a set of comprehensive binding affinity prediction models for CYP19A1 using our automated Linear Interaction Energy (LIE) based workflow on a set of 132 putative and structurally diverse aromatase inhibitors obtained from a typical industrial screening study. We extended the workflow with machine learning methods to automatically cluster training and test compounds in order to maximize the number of explained compounds in one or more predictive LIE models. The method uses protein-ligand interaction profiles obtained from Molecular Dynamics (MD) trajectories to help model search and define the applicability domain of the resolved models. Our method was successful in accounting for 86% of the data set in 3 robust models that show high correlation between calculated and observed values for ligand-binding free energies (RMSE < 2.5 kJ mol-1), with good cross-validation statistics.

Ligand- and Structure-Based Drug Design of Non-Steroidal Aromatase Inhibitors (NSAIs) in Breast Cancer

Aromatase is a multienzyme complex overexpressed in breast cancer and responsible for estrogen production. It is the potential target for designing anti-breast cancer drugs. Ligand and Structure-Based Drug Designing approaches (LBDD and SBDD) are involved in development of active and more specific Nonsteroidal Aromatase Inhibitors (NSAIs). Different LBDD and SBDD approaches are presented here to understand their utility in designing novel NSAIs. It is observed that molecules should possess a five or six membered heterocyclic nitrogen containing ring to coordinate with heme portion of aromatase for inhibition. Moreover, one or two hydrogen bond acceptor features, hydrophobicity, and steric factors may play crucial roles for anti-aromatase activity. Electrostatic, van der Waals, and p-p interactions are other important factors that determine binding affinity of inhibitors. HQSAR, LDA-QSAR, GQSAR, CoMFA, and CoMSIA approaches, pharmacophore mapping followed by virtual screening, docking, and dynamic simulation may be effective approaches for designing new potent anti-aromatase molecules.

Evidence to Support the Anti-Cancer Effect of Olive Leaf Extract and Future Directions

The traditional Mediterranean diet (MD) is associated with long life and lower prevalence of cardiovascular disease and cancers. The main components of this diet include high intake of fruit, vegetables, red wine, extra virgin olive oil (EVOO) and fish, low intake of dairy and red meat. Olive oil has gained support as a key effector of health benefits and there is evidence that this relates to the polyphenol content. Olive leaf extract (OLE) contains a higher quantity and variety of polyphenols than those found in EVOO. There are also important structural differences between polyphenols from olive leaf and those from olive fruit that may improve the capacity of OLE to enhance health outcomes. Olive polyphenols have been claimed to play an important protective role in cancer and other inflammation-related diseases. Both inflammatory and cancer cell models have shown that olive leaf polyphenols are anti-inflammatory and protect against DNA damage initiated by free radicals. The various bioactive properties of olive leaf polyphenols are a plausible explanation for the inhibition of progression and development of cancers. The pathways and signaling cascades manipulated include the NF-κB inflammatory response and the oxidative stress response, but the effects of these bioactive components may also result from their action as a phytoestrogen. Due to the similar structure of the olive polyphenols to oestrogens, these have been hypothesized to interact with oestrogen receptors, thereby reducing the prevalence and progression of hormone related cancers. Evidence for the protective effect of olive polyphenols for cancer in humans remains anecdotal and clinical trials are required to substantiate these claims idea. This review aims to amalgamate the current literature regarding bioavailability and mechanisms involved in the potential anti-cancer action of olive leaf polyphenols.

Clinical utility of letrozole in the treatment of breast cancer: a Chinese perspective

The incidence rate of breast cancers in People’s Republic of China has increased in the last decade, and many cases are responsive to hormone therapies. The third-generation aromatase inhibitor letrozole inhibits estrogen production, and is more efficacious than the estrogen receptor inhibitor tamoxifen. In recent years, letrozole has been widely used to treat postmenopausal breast cancers in People’s Republic of China. Also, metastatic, premenopausal, and male breast cancers have been effectively treated by a combination of letrozole with cytotoxic, radiation, or other therapies. In this review, we provide a perspective and summary of recent advances in the use of letrozole for breast cancer in Chinese patients.

Ligand- and Structure-Based Drug Design of Non-Steroidal Aromatase Inhibitors (NSAIs) in Breast Cancer

Aromatase is a multienzyme complex overexpressed in breast cancer and responsible for estrogen production. It is the potential target for designing anti-breast cancer drugs. Ligand and Structure-Based Drug Designing approaches (LBDD and SBDD) are involved in development of active and more specific Nonsteroidal Aromatase Inhibitors (NSAIs). Different LBDD and SBDD approaches are presented here to understand their utility in designing novel NSAIs. It is observed that molecules should possess a five or six membered heterocyclic nitrogen containing ring to coordinate with heme portion of aromatase for inhibition. Moreover, one or two hydrogen bond acceptor features, hydrophobicity, and steric factors may play crucial roles for anti-aromatase activity. Electrostatic, van der Waals, and p-p interactions are other important factors that determine binding affinity of inhibitors. HQSAR, LDA-QSAR, GQSAR, CoMFA, and CoMSIA approaches, pharmacophore mapping followed by virtual screening, docking, and dynamic simulation may be effective approaches for designing new potent anti-aromatase molecules.

Novel methods and tracers for breast cancer imaging

Although positron emission tomography (PET) using [(18)F]fluorodeoxyglucose (FDG) has an established role in breast cancer staging and monitoring response to therapy, more specifically novel targeted tracers are under investigation and hold promise toward identification of critical molecular targets of therapy. We review herein novel tracers in breast cancer including steroidal endocrine tracers, 16α-[(18)F]fluoro-17β-estradiol (FES) to measure tumor estrogen receptor density and function and 21-(18)F-fluoro-16α,17α-[(R)-(1'-α-furylmethylidene)dioxy]-19-norpregn-4-ene-3,20-dione (FFNP) to assay tumor progesterone receptor (PgR) expression, and to asses nuclear proliferation using 3'-deoxy-3'-fluorothymidine (FLT), membrane lipids using (11)C- or (18)F-labeled choline and amino acid transport using (11)C-methionine. These investigational tracers are moving closer to clinical use, and are likely to affect clinical care by aiding in characterization of breast cancer biology, which can have an important effect in the selection of targeted therapy and monitoring responsiveness to such therapy.

Eurycomanone, the major quassinoid in Eurycoma longifolia root extract increases spermatogenesis by inhibiting the activity of phosphodiesterase and aromatase in steroidogenesis

ETHNOPHARMACOLOGICAL RELEVANCE

Eurycoma longifolia Jack (Simaroubaceae family), known locally as 'Tongkat Ali' by the ethnic population, is popularly taken as a traditional remedy to improve the male libido, sexual prowess and fertility. Presently, many tea, coffee and carbonated beverages, pre-mixed with the root extract are available commercially for the improvement of general health and labido. Eurycomanone, the highest concentrated quassinoid in the root extract of E. longifolia improved fertility by increasing testosterone and spermatogenesis of rats through the hypothalamus-pituitary-gonadal axis, but the mechanisms underlying the effects are not totally clear.

AIM OF THE STUDY

To provide evidences on the plant ethnopharmacological use and the involvement of eurycomanone, the major indigenous plant quassinoid in testosterone steroidogenesis and spermatogenesis increase.

MATERIAL AND METHODS

The rat testicular Leydig cell-rich interstitial cells were isolated and incubated in the culture medium M199. The viability of the cells was determined with trypan blue staining and the concentration of the viable cells was counted with a haemocytometer. The 3β-hydroxysteroid dehydrogenase (HSD) staining method was used to measure the abundance of Leydig cells in the preparation. Eurycomanone and the standard steroidogenesis inhibitors were incubated with 1.0 × 10(5) cells, and after 2h, the testosterone and the oestrogen concentrations were determined by the ELISA method. Computational molecular docking was performed to determine the binding affinity of the compound at the respective steroidogenesis enzymes.

RESULTS

Eurycomanone (EN) significantly increased testosterone production dose-dependently at 0.1, 1.0 and 10.0 μM (P<0.05), but the two lower doses when combined with 3-isobutyl-1-methylxanthine (IBMX), the phosphodiesterase inhibitor were not significantly higher than EN or IBMX alone, except at a higher concentration. The molecular docking studies indicated EN and IBMX were binding at different sites of the enzyme. EN has no reversal of inhibition by aminoglutethimide, ketoconazole or nifedipine at the respective steroidogenesis enzyme. The quassinoid was also non-responsive to the inhibition of oestrogen receptor by tamoxifen, but displayed improved formestane inhibition of aromatase in reducing oestrogen production. The molecular docking studies further supported that EN and formestane bound to aromatase with similar orientations and free energy binding values.

CONCLUSION

Eurycomanone enhanced testosterone steroidogenesis at the Leydig cells by inhibiting aromatase conversion of testosterone to oestrogen, and at a high concentration may also involve phosphodiesterase inhibition. The quassinoid may be worthy for further development as a phytomedicine to treat testosterone-deficient idiopathic male infertility and sterility.

CITED2 modulates estrogen receptor transcriptional activity in breast cancer cells

Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 (CITED2) is a member of the CITED family of non-DNA binding transcriptional co-activators of the p300/CBP-mediated transcription complex. Previously, we identified CITED2 as being overexpressed in human breast tumors relative to normal mammary epithelium. Upon further investigation within the estrogen receptor (ER)-positive subset of these breast tumor samples, we found that CITED2 mRNA expression was elevated in those associated with poor survival. In light of this observation, we investigated the effect of elevated CITED2 levels on ER function. While ectopic overexpression of CITED2 in three ER-positive breast cancer cell lines (MCF-7, T47D, and CAMA-1) did not alter cell proliferation in complete media, growth was markedly enhanced in the absence of exogenous estrogen. Correspondingly, cells overexpressing CITED2 demonstrated reduced sensitivity to the growth inhibitory effects of the selective estrogen receptor modulator, 4-hydroxytamoxifen. Subsequent studies revealed that basal ER transcriptional activity was elevated in CITED2-overexpressing cells and was further increased upon the addition of estrogen. Similarly, basal and estrogen-induced expression of the ER-regulated genes trefoil factor 1 (TFF1) and progesterone receptor (PGR) was higher in cells overexpressing CITED2. Concordant with this observation, ChIP analysis revealed higher basal levels of CITED2 localized to the TFF-1 and PGR promoters in cells with ectopic overexpression of CITED2, and these levels were elevated further in response to estrogen stimulation. Taken together, these data indicate that CITED2 functions as a transcriptional co-activator of ER in breast cancer cells and that its increased expression in tumors may result in estrogen-independent ER activation, thereby reducing estrogen dependence and response to anti-estrogen therapy.

Inhibitory effect of luteolin on estrogen biosynthesis in human ovarian granulosa cells by suppression of aromatase (CYP19)

Inhibition of aromatase, the key enzyme in estrogen biosynthesis, is an important strategy in the treatment of breast cancer. Several dietary flavonoids show aromatase inhibitory activity, but their tissue specificity and mechanism remain unclear. This study found that the dietary flavonoid luteolin potently inhibited estrogen biosynthesis in a dose- and time-dependent manner in KGN cells derived from human ovarian granulosa cells, the major source of estrogens in premenopausal women. Luteolin decreased aromatase mRNA and protein expression in KGN cells. Luteolin also promoted aromatase protein degradation and inhibited estrogen biosynthesis in aromatase-expressing HEK293A cells, but had no effect on recombinant expressed aromatase. Estrogen biosynthesis in KGN cells was inhibited with differing potencies by extracts of onion and bird chili and by four other dietary flavonoids: kaempferol, quercetin, myricetin, and isorhamnetin. The present study suggests that luteolin inhibits estrogen biosynthesis by decreasing aromatase expression and destabilizing aromatase protein, and it warrants further investigation as a potential treatment for estrogen-dependent cancers.

Twist contributes to hormone resistance in breast cancer by downregulating estrogen receptor-α

The role of estrogen receptor-α (ER) in breast cancer development, and as a primary clinical marker for breast cancer prognosis, has been well documented. In this study, we identified the oncogenic protein, TWIST1 (Twist), which is overexpressed in high-grade breast cancers, as a potential negative regulator of ER expression. Functional characterization of ER regulation by Twist was performed using Twist low (MCF-7, T-47D) and Twist high (Hs 578T, MDA-MB-231, MCF-7/Twist) expressing cell lines. All Twist high expressing cell lines exhibited low ER transcript and protein levels. By chromatin immunoprecipitation and promoter assays, we demonstrated that Twist could directly bind to E-boxes in the ER promoter and significantly downregulate ER promoter activity in vitro. Functionally, Twist overexpression caused estrogen-independent proliferation of breast cells, and promoted hormone resistance to the selective estrogen receptor modulator tamoxifen and selective estrogen receptor down-regulator fulvestrant. Importantly, this effect was reversible on downregulating Twist. In addition, orthotopic tumors generated in mice using MCF-7/Twist cells were resistant to tamoxifen. These tumors had high vascular volume and permeability surface area, as determined by magnetic resonance imaging (MRI). Mechanistically, Twist recruited DNA methyltransferase 3B (DNMT3B) to the ER promoter, leading to a significantly higher degree of ER promoter methylation compared with parental cells. Furthermore, we demonstrated by co-immunoprecipitation that Twist interacted with histone deacetylase 1 (HDAC1) at the ER promoter, causing histone deacetylation and chromatin condensation, further reducing ER transcript levels. Functional re-expression of ER was achieved using the demethylating agent, 5-azacytidine, and the HDAC inhibitor, valproic acid. Finally, an inverse relationship was observed between Twist and ER expression in human breast tumors. In summary, the regulation of ER by Twist could be an underlying mechanism for the loss of ER activity observed in breast tumors, and may contribute to the generation of hormone-resistant, ER-negative breast cancer.

Bone metabolism and quality-of-life of postmenopausal women with invasive breast cancer receiving neoadjuvant hormonal therapy: sub-analyses from celecoxib anti-aromatase neoadjuvant (CAAN) trial

OBJECTIVE

Anti-aromatase therapy is important in the treatment of breast cancer in postmenopausal women but they have effects on the bone mineral density (BMD) and osteoporosis. Cyclooxygenase-2 (COX-2) inhibitors have been shown to be effective in chemoprevention in animal and clinical studies. A proof of principle study was performed to investigate the efficacy of combing anti-aromatase therapy (exemestane) and COX-2 inhibitors neoadjuvantly. The changes in the BMD, bone turnover proteins and quality-of-life (QoL) were analyzed and presented here.

METHOD

82 postmenopausal patients with histologically confirmed invasive hormone-sensitive breast cancers were included for the neoadjuvant therapy (NHT). 30 patients received exemestane (EXE) 25 mg daily and celecoxib (CXB) 400 mg twice daily (group A), 24 patients received EXE 25 mg daily (group B) and 28 patients received letrozole (LET) 2.5 mg daily (group C). The same assigned treatment was intended to continue for 2 years to study the changes in the bone metabolism. BMD of 48 patients were analyzed; 23 belongs to group A, 10 to group B and 15 to group C. The serum bone turnover proteins bone-specific alkaline phosphatase (BAP) and carboxyterminal crosslinked telopeptide of type I collagen (ICTP), were measured with commercially available test kits before treatment, 3 months and 15 months after treatment. Functional Assessment of Cancer Therapy core questionnaire (FACT-G) with its additional breast cancer subscale were performed at baseline, 4, 8, and 12 weeks after NHT.

RESULT

Difference between groups (p=0.007) for BMD at femur was significant. The changes of BMD in group B patients were significantly greater than patients in group A (p=0.011, CI=0.063-0.437), and group C (p=0.003, CI=0.146-0.620). The mean BAP increased from baseline in group B patients but decreased from baseline in group C patients at 3 months and 15 months. No statistical significance was found in the FACT-G scores and FACT-B scores among different groups at baseline, week 4, week 8 and week 12 after NHT. The Breast Cancer Subscale scores in group A patients were significantly higher than that of group C patients (p=0.021). After 4 weeks of NHT, negative changes of FACT-B and FACT-G scores were found in group B and C patients, but there were positive changes in group A patients. Significant differences of FACT-B score (p=0.008) and FACT-G score (p=0.019) were observed at that time point. Article from the Special issue on Targeted Inhibitors.

Emerging drugs for the management of cancer treatment induced bone loss

AREAS COVERED IN THIS REVIEW

We focus our attention on data on the efficacy of currently available and emerging drugs for the management of cancer treatment induced bone loss (CTIBL) found in a PubMed research from 1997 till today.

IMPORTANCE OF THE FIELD

One of the most common and severe safety issues of the antihormonal therapy in both sexes is the CTIBL and the related fragility fractures. In postmenopausal women with estrogenic receptor positive breast cancer, the third-generation aromatase inhibitors (AIs) are the standard therapy. Observational retrospective studies have found that AIs treated patients had a high rate of bone loss and fracture risk (RR 1.3). Also in men with prostate cancer receiving androgen deprivation therapy, the increase in bone turnover and the consequent bone loss are very rapid and sustained significantly increasing the fracture risk.

WHAT THE READER WILL GAIN

The aim of our review is to provide the current evidences for the management of bone loss and fracture risk in this subpopulation.

TAKE HOME MESSAGE

The very high rate of bone loss and the high incidence of fractures indicate that cancer patients at risk of CTIBL need to be carefully monitored and stratified for fracture risk. Although there is a strong evidence of efficacy in prevention of bone loss and reduction of fracture risk for many drugs approved for postmenopausal osteoporosis (PMO) and male osteoporosis, for CTIBL there are actually no drugs approved for this indication.

Imaging progesterone receptor in breast tumors: synthesis and receptor binding affinity of fluoroalkyl-substituted analogues of tanaproget

The progesterone receptor (PR) is estrogen regulated, and PR levels in breast tumors can be used to predict the success of endocrine therapies targeting the estrogen receptor (ER). Tanaproget is a nonsteroidal progestin agonist with very high PR binding affinity and excellent in vivo potency. When appropriately radiolabeled, it might be used to image PR-positive breast tumors noninvasively by positron emission tomography (PET). We describe the synthesis and PR binding affinities of a series of fluoroalkyl-substituted 6-aryl-1,4-dihydrobenzo[d][1,3]oxazine-2-thiones, analogues of Tanaproget. Some of these compounds have subnanomolar binding affinities, higher than that of either Tanaproget itself or the high affinity PR ligand R5020. Structure-binding affinity relationships can be rationalized by molecular modeling of ligand complexes with PR, and the enantioselectivity of binding has been predicted. These compounds are being further evaluated as potential diagnostic PET imaging agents for breast cancer, and enantiomerically pure materials of defined stereochemistry are being prepared.

Intracrinology of sex steroids in ductal carcinoma in situ (DCIS) of human breast: comparison to invasive ductal carcinoma (IDC) and non-neoplastic breast

Sex steroids, including those through intratumoral production in an intracrine manner, play important roles in the development of invasive ductal carcinoma (IDC) of human breast, but biological and/or clinical significance of intratumoral production and metabolism of sex steroids, have remained largely unknown in the ductal carcinoma in situ (DCIS), an important precursor lesion of IDC. We recently examined tissue concentration of estradiol and 5-dihydrotestosterone using liquid chromatography/electrospray tandem mass spectrometry in non-neoplastic breast, DCIS, and IDC tissues. Results of our study suggest that intratumoral concentrations of both estradiol and 5-dihydrotestosterone are increased in DCIS, which is considered due to intratumoral production of these sex steroids. Therefore, both estradiol and 5-dehydrotestosterone are considered to play important roles in the development of DCIS as well as IDC through an intracrine manner. Intratumoral metabolism and synthesis of estrogens and androgens as a result of the interactions of various enzymes are therefore also considered to play important roles in hormone dependent DCIS. Aromatase, which is one of the estrogen synthesis enzymes, plays an important role in intratumoral production of estrogen but other enzymes also play pivotal roles in intratumoral estrogen and androgen productions in human breast carcinoma. Therefore, in this review, we also focused on the importance of key intracrine enzymes such as 17beta-hydroxysteroid dehydrogenases, steroid sulfatase,estrogen sulfotransferase, 5alpha-reductases in both IDC and DCIS.

The influence of endocrine treatments for breast cancer on health-related quality of life

Many hormonal modalities are available for breast cancer treatment, such as selective oestrogen receptor modulators (SERMs), aromatase inhibitors, progestins and luteinising hormone-releasing hormone (LHRH) agonists. The long-term impact of these endocrine manipulations is an issue, because the duration of adjuvant treatment is still increasing, as is the number of breast cancer survivors. Premature menopause is induced at a young age, and may often be permanent after chemotherapy. The purpose of this review is to provide a literature-based overview of the side effects of endocrine treatment in pre- and postmenopausal breast cancer patients and the influence on HRQoL, especially on sexual functioning. The collection of health-related quality of life (HRQoL) data can result in better treatment recommendations during endocrine therapy.

METHODS

This review was limited to prospective randomised studies in English literature from between 1977 and 2007 and provides an overview of the effects on HRQoL and sexuality of various hormonal treatment in pre- and postmenopausal breast cancer patients, both in the adjuvant and palliative setting. Relevant clinical studies were identified by using the Medline database.

RESULTS

HRQoL mostly is severely influenced by chemotherapy and part of these symptoms may be lasting, especially when associated with the induction of premature menopause. Similar symptoms may be encountered during ovarian suppression therapy by LHRH analogs, but they will usually prove to be reversible. The varying side effect profiles of tamoxifen and aromatase inhibitors did not lead to significant difference in overall HRQoL. HRQoL during progestins and the SERM fulvestrant has been compared to this during aromatase inhibitors, and a large number of studies on HRQoL during endocrine therapy will be discussed.

CYP1B1 is not a major determinant of the disposition of aromatase inhibitors in epithelial cells of invasive ductal carcinoma

CYP1B1 and CYP19 (aromatase) have been shown to be expressed in breast tumors. Both enzymes are efficient estrogen hydroxylases, indicating the potential for overlapping substrate and inhibitor specificity. We measured the inhibition properties of aromatase inhibitors (AIs) against CYP1B1-catalyzed hydroxylation of 17beta-estradiol (E2) to determine whether CYP1B1 affects the disposition of AIs. In addition, we estimated the frequency of coexpression of these enzymes in breast tumor epithelium. Immunohistochemical analyses of CYP19 and CYP1B1 in a panel of 29 cases of invasive ductal carcinoma of the breast showed epithelial cell staining for CYP19 in 76% and for CYP1B1 in 97% of the samples. Statistical analysis showed no significant correlation (0.33) for positive expression of CYP19 and CYP1B1 (p > 0.07). CYP1B1 inhibition was determined for two steroidal inhibitors: formestane and exemestane and five nonsteroidal inhibitors: aminoglutethimide, fadrozole, anastrozole, letrozole, and vorozole. Of the seven compounds tested, only vorozole exhibited inhibition of CYP1B1 activity with IC(50) values of 17 and 21 microM for 4-hydroxy estradiol and 2-hydroxy estradiol, respectively. The estimated K(i) values of vorozole for E2 4- and 2-hydroxylation were 7.26 and 6.84 microM, respectively. Spectrophotometric studies showed that vorozole was a type II inhibitor of CYP1B1. This study shows that with the exception of vorozole, the aromatase inhibitors are selective for CYP19 relative to CYP1B1. Thus, although both CYP19 and CYP1B1 are expressed in a high percentage of breast cancers, CYP1B1 is not a major determinant of the disposition of AIs.

Aromatase inhibitors: past, present and future in breast cancer therapy

Estrogen has been implicated in promoting breast cancer in a majority of women. Endocrine therapy controlling estrogen production has been the guiding principle in treating breast cancer for more than a century. A greater understanding of this disease at a molecular level has led to the development of molecules that inhibit estrogen production by inhibiting the aromatase enzyme, that is the primary source of estrogen in postmenopausal women. This review examines the evolution of aromatase inhibitor (AI) based therapies over the past three decades. The third generation aromatase inhibitors (anastrozole, letrozole and exemestane), which have been found to be extremely specific and effective in an adjuvant/neoadjuvant/extended adjuvant setting are discussed from a biochemical and clinical perspective. A comprehensive discussion of the past, present, and future of aromatase inhibitors is conducted in this review.

Of mice and men: the many guises of estrogens

Models of estrogen insufficiency have revealed new and unexpected roles for estrogens in males as well as females. These models include natural mutations in the aromatase gene in humans, as well as mouse knock-outs of aromatase and the estrogen receptors, and one man with a mutation in the ERa gene. These mutations, both natural and experimental, have revealed that estrogen deficiency results in a spectrum of symptoms. These include loss of fertility and libido in both males and females; loss of bone in both males and females; a cardiovascular and cerebrovascular phenotype; development of a metabolic syndrome in both males and females, with truncal adiposity and male-specific hepatic steatosis. Most of these symptoms can be reversed or attenuated by estradiol therapy. Thus estrogen is involved in the maintenance of general physiological homeostasis in both sexes.

New development in intracrinology of breast carcinoma: therapeutic horizons after aromatase inhibitors

Aromatase inhibitors have become the gold standard of endocrine therapy in postmenopausal patients with estrogen receptor-positive or estrogen-dependent breast carcinoma, replacing tamoxifen. However, it is true that there are some potential problems to be overcome or improved on regarding aromatase inhibitor treatment of breast cancer. This especially includes the presence of the estrogen receptor-positive patients who do not necessarily respond to aromatase inhibitors, may require other modes of endocrine therapy and develop resistance to aromatase inhibitor in their clinical course, and who may also need alternative modes of suppressing intratumoral estrogen signals or other intracellular signal pathways related to tumor progression or development. Intratumoral estrogen production from precursors present in circulation in an 'intracrine' manner is considered to play very important roles in the development and progression of estrogen receptor-positive breast cancer. The great majority of estrone in circulation is present as a sulfated form or estrone sulfate, and steroid sulfatase hydrolyzes circulating estrone sulfate to estrone in various human tissues in situ, which confers potent estrogenic actions. Estrone is subsequently reduced to 17β-estradiol by 17β-hydroxysteroid dehydrogenase type 1. Therefore, these two enzymes also play very important roles in intracrinology of estrogen in breast cancer in addition to intratumoral aromatase, and the potential inhibition of these two enzymes could lead to the development of a new mode of endocrine therapy based on intracrinology, which may overcome some of the problems above in aromatase inhibitor therapy. In this review, the potential advantages and pitfalls or problems associated with the inhibition of these two intratumoral enzymes in breast cancer patients will be discussed.

Diffusion of aromatase inhibitors for breast cancer therapy between 1996 and 2003 in the Cancer Research Network

PURPOSE

Clinical trials demonstrated adjuvant aromatase inhibitor treatment is superior for decreasing breast cancer recurrence risk over adjuvant tamoxifen treatment as early as 2001. Yet clinical use for adjuvant treatment was not recommended by the American Society of Clinical Oncology until 2004. Aromatase inhibitor uptake after the first public presentation of randomized trial results but before the release of national guidelines is unclear. We evaluated diffusion of aromatase inhibitor dispensings for breast cancer treatment in integrated healthcare delivery systems across the United States.

METHODS

We collected automated data for 13,245 women enrolled at seven integrated healthcare delivery systems in the Cancer Research Network. All women were aged >55 and diagnosed with estrogen receptor positive, invasive breast cancer between 1996 and 2003. We used electronic pharmacy data to identify aromatase inhibitor and tamoxifen dispensings through 2004. We evaluated the proportions of women who received hormone dispensings in two ways: (1) at any point after diagnosis to capture all use, and (2) in the two-year period following diagnosis to approximate adjuvant use.

RESULTS

Over time, adjuvant aromatase inhibitor use increased whereas tamoxifen use decreased. Aromatase inhibitor dispensings within 2 years of diagnosis increased from 4.1% among women diagnosed in 2000 to 13% in 2001, 24% in 2002, and 40% in 2003. Tamoxifen use declined starting in 2001 at every system.

CONCLUSION

Aromatase inhibitor use rose dramatically after 2001 while tamoxifen use decreased. It appears results from early clinical trials changed practice in these integrated healthcare systems before formal changes in national guidelines.

New development in intracrinology of breast carcinoma

Intratumoral metabolism and synthesis of estrogens as a result of the interactions of various enzymes are considered to play very important roles in the pathogenesis and development of hormone dependent breast carcinoma. Among these enzymes, intratumoral aromatase plays as important role converting serum androgens to estrogens in situ, and serves as a source of estrogen, especially in postmenopausal patients with breast carcinoma. However, other enzymes such as the 17beta-hydroxysteroid dehydrogenase (17beta-HSD) isozymes, estrogen sulfatase (STS) and estrogen sulfotransferase, also play pivotal roles in intratumoral estrogen production. The 17beta-hydroxysteroid dehydrogenase (17beta-HSD) isozymes catalyze the interconversion of estradiol (E2) and estrone (E1), and thereby serve to modulate the tissue levels of bioactive E2 in human breast carcinoma. 17Beta-HSD type 1 catalyzes primarily the reduction of estrone (E1) to estradiol (E2), whereas 17beta-HSD type 2 catalyzes primarily the oxidation of E2 to E1. In human breast disease, 17beta-HSD type 1 is expressed in proliferative disease without atypia, atypical ductal hyperplasia, ductal carcinoma in situ and invasive ductal carcinoma. 17Beta-HSD type 2 has not been detected in any of these breast lesions. In addition, 17beta-HSD type 1 coexpression is significantly correlated with estrogen receptor status in invasive ductal carcinoma cases. These results indicate that breast carcinoma can effectively convert E1, produced as a result of in situ aromatization, to E2, a biologically potent estrogen, which exerts estrogenic actions on tumor cells through estrogen receptor, especially the alpha subtype in carcinoma cells. Therefore, inhibiting intratumoral 17beta-HSD type 1 is also considered to contribute to inhibition of cell proliferation by decreasing intratumoral estradiol. Estrogen sulfotransferase (EST; SULT 1E1 or STE gene) sulfonates estrogens to inactive estrogen sulfates, while steroid sulfatase (STS) hydrolyzes estrone sulfate (E1-S) to estrone. EST immunoreactivity was recently demonstrated to be significantly associated with a decreased risk of recurrence or improved prognosis by both uni- and multivariate analyses. STS immunoreactivity was significantly associated with an increased risk of recurrence by univariate analysis. These findings also suggest that EST and STS plays important roles in regulation of in situ estrogen production, and EST especially is a potent prognostic factor in human breast carcinoma. Therefore, the inhibition of intratumoral STS might also serve as an endocrine therapy in postmenopausal patients. It is also important to note that the status of intratumoral aromatase, 17beta-HSD type 1, EST and STS in human breast cancer tissues is variable and not necessarily correlated with each other, which suggests different potential sources of intratumoral estrogens among individual patients with breast cancer. These findings indicate that there are patients who could benefit more from inhibition of these intratumoral enzymes rather than aromatase inhibition as an endocrine therapy. Therefore, it will become very important to examine the intratumoral levels of 17beta-HSD type 1 and STS in the resected specimens of human breast carcinoma as potential targets of novel endocrine therapy in the near future.

Of mice and men: the evolving phenotype of aromatase deficiency

We are rapidly becoming aware of the importance of estrogen in maintaining virtually all facets of male health. In order for estrogens to be synthesized endogenously, the enzyme responsible for their synthesis from androgens, aromatase, must be functional. The seven known men in whom aromatase is nonfunctional all have a mutation in either exon V or IX of the CYP19 gene, which encodes aromatase. Collectively, these men are reported to have undetectable estrogen; normal to high levels of testosterone and gonadotropins; tall stature with delayed skeletal maturation and epiphyseal closure; osteoporosis; impaired lipid and insulin metabolism; and impaired reproductive function. The aromatase knockout mouse presents with a phenotype that is similar in many aspects and provides a valuable tool with which to examine and manipulate the actions of estrogen. By studying the naturally occurring aromatase-deficient humans, together with studies of the aromatase-knockout mouse, we are expanding our understanding of the essential role of estrogen in male physiology.

Three-dimensional model of the human aromatase enzyme and density functional parameterization of the iron-containing protoporphyrin IX for a molecular dynamics study of heme-cysteinato cytochromes

Mammalian cytochromes P450 (CYP) are enzymes of great biological and pharmaco-toxicological relevance. Due to their membrane-bound nature, the structural characterization of these proteins is extremely difficult, and therefore computational techniques, such as comparative modeling, may help obtaining reliable structures of members of this family. An important feature of CYP is the presence of an iron-containing porphyrin group at the enzyme active site. This calls for quantum chemical calculations to derive charges and parameters suitable for classical force field-based investigations of this proteins family. In this report, we first carried out density functional theory (DFT) computations to derive suitable charges for the Fe2+-containing heme group of P450 enzymes. Then, by means of the homology modeling technique, and taking advantage of the recently published crystal structure of the human CYP2C9, we built a new model of the human aromatase (CYP19) enzyme. Furthermore, to study the thermal stability of the new model as well as to test the suitability of the new DFT-based heme parameters, molecular dynamics (MD) simulations were carried out on both CYP2C9 and CYP19. Finally, the last few ns of aromatase MD trajectories were investigated following the essential dynamics protocol that allowed the detection of some correlated motions among some protein domains.