Treatment Of Hormone-dependent Breast Cancer Research Articles

Evaluating flavonoids as potential aromatase inhibitors for breast cancer treatment: In vitro studies and in silico predictions

Aromatase inhibitors are commonly employed in the treatment of hormone-dependent breast cancers, and flavonoids have emerged as a promising alternative to existing drug classes with unfavorable side effects. In this study, we conducted in vitro investigations into CYP19A1 (aromatase) inhibitory potential of 14 flavonoids, including pinocembrin, sakuranetin, eriodictyol, liquiritigenin, naringenin, hesperetin, flavanone, baicalein, chrysin, nobiletin, luteolin, sinensetin, tricin, and primuletin. Flavonoids displaying inhibitory activity were further assessed using in silico tools, such as molecular docking to predict binding affinities, as well as SwissADME, admetSAR, and QED (Quantitative Estimate of Drug-likeness) for drug-likeness prediction. Flavonoids with IC50 values less than 10 μM, pinocembrin, eriodictyol, naringenin, liquirtigenin, sakuranetin, and chrysin, exhibited favorable physicochemical properties and ADME profiles, suggesting their potential for development as novel flavonoid-based aromatase inhibitors. This study would provide valuable insights for the development of flavonoid-based aromatase inhibitors for the treatment of breast cancer.

Opportunities and prospects for the treatment of hormone-dependent breast cancer

The high incidence of breast cancer requires increased attention to the problem of rational pharmacotherapy of this condition. When choosing tactics for the treatment of breast cancer, it is recommended to take into account the immunohistochemical subtype of cancer cells. In the case of detection of estrogen-positive expression, an obligatory component of pharmacotherapy is endocrine therapy with antiestrogen orientation. Despite the fact that there are already many years of positive experience with the use of selective estrogen receptor modulators and aromatase inhibitors, the search for new more effective agents continues in terms of prolonging the life of patients and reducing the risk of adverse reactions.
 In recent years, cyclin-dependent kinase 4/6 inhibitors have been added to first-line therapy, which is a breakthrough in the treatment of metastatic breast cancer. The introduction of combined antiestrogen therapy with targeted agents that have the ability to inhibit phosphatidylinositol-3-kinase is logical in the event of resistance to primary endocrine therapy. However, the need to search and study new drugs remains. In this regard, the most promising direction is the development of agents that can reduce the expression of the Estrogen receptor alpha protein, and block estrogen-dependent and independent estrogen receptor signaling.

Towards a New Generation of Hormone Therapies: Design, Synthesis and Biological Evaluation of Novel 1,2,3-Triazoles as Estrogen-Positive Breast Cancer Therapeutics and Non-Steroidal Aromatase Inhibitors.

Aromatase inhibitors (AIs) show promising features as drugs to treat estrogen-responsive breast cancer as they block aromatase activity, the key enzyme in estrogen synthesis. The current AIs approved by the Food and Drug Administration for breast cancer treatment present severe adverse effects. For these reasons, it is important to develop of new AIs that are more specific and sensitive. In this paper, we report the synthesis and the characterization of new nonsteroidal aromatase AIs containing triazoles moieties for the treatment of hormone-dependent breast cancer in post-menopausal women. A new series of 1,2,3-triazole based molecules were successfully synthetized and their chemical structures were determined from the spectral data (FT-IR, 13C NMR, 1H NMR, mass spectroscopy) and micro-analytical data. Additionally, the physical properties of the newly synthesized derivatives were reported. The novel compounds were also tested for their anticancer activity in both breast cancer (MCF7 and T-47D) and normal breast (MCF 10A) cell lines, evaluating their effect on cell proliferation, migration, and invasion. The results revealed that the compounds exhibited promising and specific anti-cancer action.

Resistance to hormone therapy in breast cancer cells promotes autophagy and EGFR signaling pathway.

Breast cancer is the leading cause of cancer deaths for women worldwide. Endocrine therapies represent the cornerstone for hormone-dependent breast cancer treatment. However, in many cases, endocrine resistance is induced with poor prognosis for patients. In the current study, we have developed MCF-7 cell lines resistant to fulvestrant (MCF-7Fulv) and tamoxifen (MCF-7Tam) aiming at investigating mechanisms underlying resistance. Both resistant cell lines exerted lower proliferation capacity in two-dimensional (2-D) cultures but retain estrogen receptor α (ERα) expression and proliferate independent of the presence of estrogens. The established cell lines tend to be more aggressive exhibiting advanced capacity to form colonies, increased expression of epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), and heterodimerization of ERBB family receptors and activation of EGFR downstream pathways like MEK/ERK1/2 and PI3K/AKT. Tyrosine kinase inhibitors tested against resistant MCF-7Fulv and MCF-7Tam cells showed moderate efficacy to inhibit cell proliferation, except for lapatinib, which concomitantly inhibits both EGFR and HER2 receptors and strongly reduced cell proliferation. Furthermore, increased autophagy was observed in resistant MCF-7Fulv and MCF-7Tam cells as shown by the presence of autophagosomes and increased Beclin-1 levels. The increased autophagy in resistant cells is not associated with increased apoptosis, suggesting a cytoprotective role for autophagy that may favor cells' survival and aggressiveness. Thus, by exploiting those underlying mechanisms, new targets could be established to overcome endocrine resistance.NEW & NOTEWORTHY The development of resistance to hormone therapy caused by both fulvestrant and tamoxifen promotes autophagy with concomitant apoptosis evasion, rendering cells capable of surviving and growing. The fact that resistance also triggers ERBB family signaling pathways, which are poorly inhibited by tyrosine kinase inhibitors might attribute to cells' aggressiveness. It is obvious that the development of endocrine therapy resistance involves a complex interplay between deregulated ERBB signaling and autophagy that may be considered in clinical practice.

Synthesis and Characterization of Folic Acid-Functionalized DPLA-co-PEG Nanomicelles for the Targeted Delivery of Letrozole.

An effective treatment for hormone-dependent breast cancer is chemotherapy using cytotoxic agents such as letrozole (LTZ). However, most anticancer drugs, including LTZ, are classified as class IV biopharmaceuticals, which are associated with low water solubility, poor bioavailability, and significant toxicity. As a result, developing a targeted delivery system for LTZ is critical for overcoming these challenges and limitations. Here, biodegradable LTZ-loaded nanocarriers were synthesized by solvent emulsification evaporation using nanomicelles prepared with dodecanol-polylactic acid-co-polyethylene glycol (DPLA-co-PEG). Furthermore, cancer cell-targeting folic acid (FA) was conjugated into the nanomicelles to achieve a more effective and safer cancer treatment. During our investigation, DPLA-co-PEG and DPLA-co-PEG-FA displayed a uniform and spherical morphology. The average diameters of DPLA-co-PEG and DPLA-co-PEG-FA nanomicelles were 86.5 and 241.3 nm, respectively. Our preliminary data suggest that both nanoformulations were cytocompatible, with ≥90% cell viability across all concentrations tested. In addition, the amphiphilic nature of the nanomicelles led to high drug loading and dispersion in water, resulting in the extended release of LTZ for up to 50 h. According to the Higuchi model, nanomicelles functionalized with FA have a greater potential for the controlled delivery of LTZ into target cells. This model was confirmed experimentally, as LTZ-containing DPLA-co-PEG-FA was significantly and specifically more cytotoxic (up to 90% cell death) toward MCF-7 cells, a hormone-dependent human breast cancer cell line, when compared to free LTZ and LTZ-containing DPLA-co-PEG. Furthermore, a half-maximal inhibitory concentration (IC50) of 87 ± 1 nM was achieved when MCF-7 cells were exposed to LTZ-containing DPLA-co-PEG-FA, whereas higher doses of 125 ± 2 and 100 ± 2 nM were required for free LTZ and LTZ-containing DPLA-co-PEG, respectively. Collectively, DPLA-co-PEG-FA represents a promising nanosized drug delivery system to target controllably the delivery of drugs such as chemotherapeutics.

Dual aromatase-steroid sulfatase inhibitors (DASI's) for the treatment of breast cancer: a structure guided ligand based designing approach

Dual aromatase-steroid sulfatase inhibitors (DASIs) lead to significant deprivation of estrogen levels as compared to a single target inhibition and thereby exhibited an additive or synergistic effect in the treatment of hormone-dependent breast cancer (HDBC). Triazole-bearing DASI’s having structural features of clinically available aromatase inhibitors are identified as lead structures for optimization as DASI’s. To identify the spatial fingerprints of target-specific triazole as DASI’s, we have performed molecular docking assisted Gaussian field-based comparative 3D-QSAR studies on a dataset with dual aromatase-STS inhibitory activities. Separate contours were generated for both aromatase and steroid sulphates showing respective pharmacophoric structural requirements for optimal activity. These developed 3D-QSAR models also showed good statistical measures with the excellent predictive ability with PLS-generated validation constraints. Comparative steric, electrostatic, hydrophobic, HBA, and HBD features were elucidated using respective contour maps for selective target-specific favourable activity. Furthermore, the molecular docking was used for elucidating the mode of binding as DASI’s along with the MD simulation of 100 ns revealed that all the protease-ligand docked complexes are overall stable as compared to reference ligand (inhibitor ASD or Irosustat) complex. Further, the MM-GBSA study revealed that compound 24 binds to aromatase as well as STS active site with relatively lower binding energy than reference complex, respectively. A comparative study of these developed multitargeted QSAR models along with molecular docking and dynamics study can be employed for the optimization of drug candidates as DASI’s. Communicated by Ramaswamy H. Sarma

Triazoles Synthesis & Applications as Nonsteroidal Aromatase Inhibitors for Hormone-Dependent Breast Cancer Treatment

In the last few years, nonsteroidal aromatase inhibitors (AIs) have been emerged as promising agents for treating hormone-dependent breast cancer in postmenopausal women because of their inhibitory effect on estrogen synthesis. Indeed, these compounds can block the activity of aromatase, the enzyme that intervenes in the last steps of estrogen production pathway. Triazoles are the core structures of nonsteroidal AIs. The nitrogen atom of the triazole moiety plays a fundamental role in the aromatase functionality by interacting with the iron ions of the heme group. In general, AIs possess numerous advantages as they quench the last step of estrogen synthesis without any inhibitory effects on the production of other steroids produced via the same pathway. Some AIs as anastrozole, letrozole, and vorozole have already been approved by the Food and Drug Administration in the treatment of breast cancer. The previously mentioned compounds present severe and adverse effects as polycystic ovary syndrome (PCOS), resistance onset on long-term treatments, and a higher risk of bone fractures. This review focuses intensively on the role of AIs in the treatment of hormone-sensitive types of cancers, especially the role of triazoles as nonsteroidal AIs. Also, the review provides an overview about the chemistry of triazoles along with the different methods by which the v -triazoles and s-triazoles are synthesized.

Impact of Irradiation on the Pharmacokinetics and Biotransformation of Tamoxifen.

BackgroundThe optimal procedure for combining radiotherapy (RT) with tamoxifen treatment is controversial as RT may alter the pharmacokinetics and biotransformation of tamoxifen. The present study investigated this potential interaction by assessing the pharmacokinetics of tamoxifen during concurrent and sequential RT.MethodPlasma tamoxifen concentration was measured in rats with or without RT 2.0 Gy (RT2.0Gy) or 0.5 Gy (RT0.5Gy) with ultra-high-performance liquid chromatography-tandem mass spectrometry after tamoxifen administration (10 mg/kg, p.o., n = 6). Tamoxifen was either administered 1 h after RT (concurrent condition) or 24 h after RT (sequential condition).ResultsPharmacokinetic data analysis demonstrated that the area under the curve (AUC) and half-life of tamoxifen were 2,004 ± 241 h ng/ml and 6.23 ± 1.21 h, respectively, after tamoxifen administration (10 mg/kg, p.o.). The respective conversion rate of 4-hydroxytamoxifen, N-desmethytamoxifen, and endoxifen for tamoxifen metabolism was 20%, 16%, and 5%. The AUC value of tamoxifen in the RT0.5Gy group was 1.5- to 1.7-fold higher than in the sham and RT2.0Gy groups. The relative bioavailability of tamoxifen at concurrent RT0.5Gy and RT2.0Gy groups ranged from 127% to 202% and from 71% to 152%, respectively. The magnitude of endoxifen, which converted from 4-hydroxytamoxifen and N-desmethyltamoxifen, increased 3- to 5-fold in the concurrent RT groups. By contrast, the AUC of tamoxifen decreased by roughly 24% in the sequential RT2.0Gy group. The conversion ratio of endoxifen was four times higher than that in the sequential RT2.0Gy group compared with rats not exposed to RT.ConclusionThe current study provides advanced pharmacokinetic data to confirm the interaction between RT and hormone therapy. Our findings indicate that RT facilitates the metabolism of tamoxifen to active metabolites and thus imply that combination RT-tamoxifen has potential benefits for the treatment of hormone-dependent breast cancer.

The multi-specific human 17 beta-hydroxysteroid dehydrogenase type 7: Non-competitive inhibitors can target different catalyses to facilitate breast cancer treatment

Human 17β-hydroxysteroid dehydrogenase type 7 (17β-HSD7), a special multifunctional enzyme, activates the estrogen estrone while inactivating the potent androgen dihydrotestosterone. Thus, this enzyme has become an ideal target for hormone-dependent breast cancer treatment, as its inhibition leads to estradiol reduction and dihydrotestosterone restoration. However, a particular concern has arisen related to an additional role in cholesterol biosynthesis, as inhibition of the enzyme may lead to undesirable side effects.Our findings demonstrate that the available enzyme inhibitors are non-competitive. Among these, many such as INH81, are specific toward sex-hormone conversion, whereas others represented by 4-bromo-ethynylestradiol, are more specific for zymosterone reduction occurring during cholesterol biosynthesis. The binding of non-competitive inhibitors does not affect the substrate binding on the enzyme. This is the first demonstration of non-competitive inhibitors acting selectively on different catalyses, thereby facilitating inhibitor uses for breast cancer treatment. We aim to quickly communicate the novel results.

Synthesis, Aromatase Inhibitory, Antiproliferative and Molecular Modeling Studies of Functionally Diverse D-Ring Pregnenolone Pyrazoles

Aromatase, a cytochrome P450 hemoprotein that is responsible for estrogen biosynthesis by conversion of androgens into estrogens, has been an attractive target in the treatment of hormonedependent breast cancer. Design of new steroidal aromatase inhibitors becomes imperative. Synthesis and biological evaluation of two classes of structurally and functionally diverse D-ring pregnenolone pyrazoles as type I aromatase inhibitors and antiproliferative agents. Pregnenolone (1) was converted to 3β-hydroxy-21-hydroxymethylidenepregn-5-en-20-one (2), which upon cyclization with phenylhydrazine generated regioisomeric pairs of pyrazoles 4 and 5. Further, Knoevenagel condensation of pregnenolone (1) with 3-oxo-3-phenylpropanenitrile (6) produced 2-benzoyl-3-(3b-hydroxyandrostan- 5-ene-20-ylidene)-but-2-enenitrile (7), which upon cyclization with hydrazine or phenylhydrazine generated the pyrazoles 8 and 9. All new steroidal derivatives were tested for their aromatase inhibition activity using Dibenzylfluorescein (DBF) based fluorescence assay developed by Stresser et al. Antiproliferative activities were measured using Sulforhodamine B assay. The activities were promising and there was a coherence between aromatase inhibitory and antiproliferative activities. The study reveals the immense potential of pregnenolone pyrazoles as aromatase inhibitors for the treatment of breast cancer. Molecular docking studies proved efficient binding of the new steroidal analogs on human placental aromatase. In the overall study, most of the compounds exhibited potential activity for the treatment of hormone dependent breast cancer. Compounds 4c and 4d were found to be the most promising pharmacons. Furthermore, compounds 4c and 4d were applied for their molecular docking study on human placental aromatase to predict their possible binding modes with the enzyme. These studies revealed that such molecules have high scope and potential for further investigation towards the treatment of estrogen dependent breast cancer.

Dual Aromatase-Sulphatase Inhibitors (DASIs) for the Treatment of Hormone Dependent Breast Cancer.

Breast cancer is the most frequently diagnosed cancer in women and the second most common form of cancer, causing death after lung cancer, all across the globe at an alarming rate. The level of estrogens in breast cancer tissues of postmenopausal women is 10-40 folds higher than the non-carcinogenic breast tissues. As a result of this greater level of estrogen, breast tissue becomes more prone to develop breast cancer; mainly, estradiol plays a significant role in the initiation and development of hormone-dependent breast cancer. Androstenedione, Adrenal dehydroepiandrosterone sulfate, and estrone-sulfate also play an important role as precursors for estrogen biosynthesis. Estrogen deprivation exhibits an attractive phenomenon in the advancement of ideal therapeutics for the treatment of breast cancer. Inhibition of aromatase and sulphatase emerged as an attractive therapy for the treatment of hormone-dependent breast cancer via deprivation of estrogen by different pathways. The cocktail of aromatase and sulphatase inhibitors known as Dual Aromatase-sulphatase Inhibitors (DASIs) emerged as an attractive approach for effective estrogen deprivation. The present review article focused on the journey of dual aromatase-sulphatase inhibitors from the beginning to date (2020). Keeping in view the key observations, this review may be helpful for medicinal chemists to design and develop new and efficient dual aromatase-sulphatase inhibitors for the possible treatment of hormone- related breast cancer.

The impact of xenoestrogens on effectiveness of treatment for hormone-dependent breast cancer – current state of knowledge and perspectives for research

Breast cancer is the most common cancer occurring in women and causing the highest number of deaths among them. The role of xenoestrogens has been the subject of many studies in the pathogenesis of breast cancer. Less is known about the impact of xenoestrogens on the effectiveness of hormone therapy used to treat breast cancer, and thus possible drug-xenostrogen interactions. The aim of this review is to summarize the current state of knowledge and present perspectives for further research on the impact of xenoestrogens on the effectiveness of drugs used in the treatment of hormone-dependent breast cancer. Phytoestrogens, in particular flavonoid genistein, are the best studied group of xenoestrogens in terms of interaction with drugs used in the treatment of breast cancer, due to their frequent use, including their use in alleviating the adverse effects of hormone therapy. Analyzing the current state of knowledge, it seems that phytoestrogens intake should be avoided during conventional anti-cancer treatment. Of the other xenoestrogens, bisphenol A (BPA) is one of the best-tested compounds for interactions with drugs used to treat breast cancer. It has been shown that bisphenol A could reduced therapeutic effect of active tamoxifen metabolite and cytostatics used in breast cancer treatment. Confirmation in clinical trials of the results obtained in vitro and in vivo tests, would enable the creation of specific recommendations for patients undergoing breast cancer treatment, especially hormone therapy. An area requiring further research is the analysis of the effects of xenoestrogens other than phytoestrogens, e.g. metalloestrogens, on the effects of drugs used in the treatment of breast cancer.

SAT-LB130 Tamoxifen Affects MiRNA Expression in Uterus and Breast Tamoxifen Affects MiRNA Expression in Uterus and Breast Tamoxifen Affects MiRNA Expression in Uterus and Breast

In addition to genetic factors, environmental factors and lifestyle can play a significant role in the development of hormone-dependent tumors, such as endometrial cancer (EC) and breast cancer (BC). The discovery of microRNAs (miRs) involved in the post-transcriptional regulation of many genes, including those of hormonal carcinogenesis, namely, steroid receptors and their target genes, strengthened the epigenetic direction in the study of carcinogenesis mechanisms. A critical event in the development of hormone-dependent human tumors is violation in the metabolism of steroid hormones, primarily estradiol. An interesting aspect of the problem of ERα inhibition is the use of tamoxifen (TAM) in clinical practice in the treatment of hormone-dependent BC. A well-known side effect of TAM is increased proliferation in the endometrium and an elevated risk of EC. One of the mechanisms explaining such differences in the effects of TAM is formation of DNA adducts in endometrial cells, but this mechanism has not yet been substantiated. Therefore, the problem of carcinogenesis of the uterus with this drug remains unresolved and requires further research. The aim of our study was to evaluate the expression of miRs and target genes for hormonal carcinogenesis in the uterus and mammary gland under the exposure with TAM. As an object of study, we used female rats, primary human cell cultures and tissues of TAM-induced human endometrial hyperplasia. The results showed that estradiol enhances the expression of oncogenic microRNAs miR-21-, 221, -222 by three-ten times, both in the rat mammary gland and endometrium, which confirms its oncogenic properties. In the rat endometrium, TAM, to a greater extent than estradiol, increased the expression of oncogenic miRs, especially miR-419, -23a, 24-2,- 27, and significantly reduced the expression of their target genes. In addition, TAM caused a multiple (8-fold) increase in the expression of cyclin D in uterus compared with mammary gland. In most cases, TAM reduced expression of oncogenic miR-21,-221,-222 by 50% in BC primary cell culture whereas in EC primary cell culture expression of oncogenic 190a was increased. We also investigated the activity of estrogen-metabolizing enzymes in tamoxifen-induced human endometrial hyperplasia. A significant difference was found in the expression of estrogen-metabolizing genes (CYP1A,1B, CYP19, SULT1A1, SULT1E1, GSTP1,2, COMT, STS) in TAM-induced endometrial hyperplasia, which may be due to the difference in miRNA expression. Thus, both for the animal model and human cell cultures, it was shown that TAM causes other changes in the expression of microRNAs in the endometrium compared with the breast. Further studies with the identification of target miRNA genes will help identify molecular targets of TAM-induced endometrial hyperplasia. This work was supported by Russian Science Foundation, grant # 19-15-00319.

Current understanding of selective estrogen receptor modulators

Despite the variety of selective estrogen receptor modulators of different classes of compounds and their active use for the treatment of hormone-dependent breast cancer, climacteric conditions, and polycystic ovary syndrome, as well as for ovulation stimulation and for prevention and treatment of postmenopausal osteoporosis and vertebral fractures, there are a number of serious side effects, such as thromboembolic disorders, uterine cancer and endometrial cancer. Among the selective estrogen receptor modulators used in clinical practice, it is worth noting: Raloxifene, for the prevention and treatment of postmenopausal osteoporosis and vertebral fractures; Tamoxifen, for the treatment of breast cancer; Toremifene, for the treatment of metastatic breast cancer in postmenopausal women; Lasofoxifene, for the treatment of osteoporosis; Bazedoxifene, for the treatment and prevention of postmenopausal osteoporosis; Clomiphene, for the treatment of anovulatory infertility; Ospemifene, for the treatment of moderate to severe dyspareunia associated with postmenopausal syndrome. An ongoing search for an effective and safe selective estrogen receptor modulator for the treatment of endometriosis is currently underway.

Protective effect of lycopene against tamoxifen-induced hepatotoxicity in albino rats

Background: Tamoxifen citrate (TAM) is a drug of choice for the treatment of hormone-dependent breast cancer, but its use has been associated with frequent hepatotoxicity. Aim: This study evaluated the protective effect of lycopene (LYP) against hepatotoxicity induced by TAM in albino rats. Methods: Adult female albino rats (200–250 g) were divided into eight groups of n = 5. Group 1 (control) received normal saline (0.2mL) intraperitoneally (i.p.), daily for 7 days. Groups 2–4 were treated daily with LYP (10 mg/kg, 20 mg/kg, and 40 mg/kg) (i.p.) for 7 days, respectively. Group 5 was treated daily with TAM (45 mg/kg) i.p. for 7 days. Groups 6–8 were supplemented daily with LYP (10 mg/kg, 20 mg/kg, and 40 mg/kg) before treatment with TAM (45 mg/kg) i.p. for 7 days, respectively. At the end of treatment, the rats were anesthetized and blood samples were collected and assessed for serum markers of liver function. Liver samples were harvested for histology and biochemical assessments. Results: Significant (P

Cardiovascular effects of rehabilitation in hormone-dependent breast cancer patient with the postcastration syndrome.

e14530Background: The treatment of hormone-dependent breast cancer (BC) involves, among other procedures, ovariectomy. This can result in the development of the postcastration syndrome (PCS) with e...

Pharmacokinetic profile of PBRM in rodents, a first selective covalent inhibitor of 17β-HSD1 for breast cancer and endometriosis treatments

The development of a covalent inhibitor of 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) is a promising approach for the treatment of hormone-dependent breast cancer and endometriosis. After reporting the steroid derivative PBRM as a first potent covalent inhibitor of 17β-HSD1 without estrogenic activity, we are now interested in studying its pharmaceutical behavior. The metabolism study in a human liver microsomal preparation showed a gradual transformation of PBRM into PBRM-O, an oxidized ketonic form of PBRM at position C17. Interestingly, PBRM-O also inhibits 17β-HSD1 and is not estrogenic in estrogen-sensitive T-47D cells. However, when PBRM was injected subcutaneously (sc) in mice, a very small proportion of PBRM-O was measured in a 24 h-time course experiment. A pharmacokinetic study in mice revealed suitable values for half-life (T1/2 = 3.4 h), clearance (CL = 2088 mL/h kg), distribution volume (Vz = 10.3 L/kg) and absolute bioavailability (F = 65%) when PBRM was injected sc at 14.7 mg/kg. A good F value of 33% was also obtained when PBRM was given orally. A tritiated version of PBRM, 3H-PBRM, was synthesized and used for an in vivo biodistribution study that showed its gradual accumulation in various mouse tissues (peak at 6 h) followed by elimination until complete disappearance after 72 h. Elimination was found to occur in feces (93%) and urine (7%) as revealed by a mass balance experiment. PBRM was also evaluated for its toxicity in mice and it was found to be very well tolerated after weekly sc administration (30–405 mg/kg for 8 weeks) or by po administration (300–900 mg/kg for 4 weeks). Overall, these experiments represent important steps in the preclinical characterization of the pharmaceutical behavior of PBRM, as well as for its translation to clinical trials.

Aromatase inhibitors: A new approach for controlling ovarian function in cattle

Numerous treatments and protocols have been used to control the reproductive cycle in cattle, with varying effectiveness and many involving the administration of steroid hormones. Steroid hormones, such as estradiol, are perceived as having a negative impact on consumer health. This internationally shared opinion has led to a ban on the use of steroid hormones in food producing animals in many countries (i.e., European Union, New Zealand, and Australia). Letrozole, a non-steroidal aromatase inhibitor, inactivates the aromatase enzyme responsible for the synthesis of estrogens by reversibly binding to the “heme” group of the P450 subunit. Letrozole is approved as an adjuvant or first-line treatment for hormone-dependent breast cancer in post-menopausal women, but has been used increasingly for ovulation induction in the treatment of infertility in women. Using the bovine model to determine the effects on ovarian function, letrozole treatment was found to extend the lifespan of the dominant follicle and thereby delay emergence of the next follicle wave and/or ovulation. Letrozole treatment also had a luteotrophic effect; that is, larger CL and/or higher circulating concentrations of progesterone were detected in letrozole-treated heifers. Results of the initial studies in cattle provided the impetus for the development of aromatase inhibitor-based synchronization and fertility treatment in cattle. Biologically active concentrations of letrozole were achieved via intravenous, intramuscular or intravaginal administration, but the intravaginal route of administration is of particular interest because it permits extended and defined treatment periods, is minimally invasive, and reduces animal handling. Recent results revealed that irrespective of the stage of the cycle, a 4-day letrozole-based protocol induced ovulation in a significantly greater proportion of animals and with significantly greater synchrony than the control treatment. Evidence and reasons for the increasing use of programmed breeding and fixed-time artificial insemination are discussed in this review as a background to current development of an innovative aromatase inhibitor-based protocol as a safe and effective method of controlling the estrous cycle and ovulation in cattle.

Fulvestrant-loaded polymer-based nanoparticles for local drug delivery: Preparation and in vitro characterization

The present investigation was aimed at optimizing Fulvestrant (FLV)-loaded nanoparticulate formulations to overcome side effects caused by the intramuscular injection of FLV, and to prolong local intratumoral action at high drug concentration. Novel poly(ethylene glycol) (PEG) conjugated poly(ethylene glycol)-block-poly(lactide-co-glycolide) (PEG-b-PLGA), and poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) nanoparticles were used as the drug-loading vehicles. The influence of hydrophobicity of the two different polymeric materials based nanoparticles was investigated with respect to in vitro properties, cytotoxic capacity and cell uptake potency. The sphere-shaped nanoparticles ranged between 84.56 and 220.20 nm, had negative surface charges, and exhibited sustained release profiles. In-vitro cytotoxicity results demonstrated that nanoparticles prepared with the higher hydrophilic form of PEG-b-PCL, a diblock copolymer composition, exerted the highest inhibitory effect on the proliferation of MCF-7 cells and significantly increased the intracellular uptake, compared to free FLV and the other tested polymer-based formulations. The final data of this research indicated that polymer hydrophobicity was a key to improving the major characteristics, especially anti-proliferative activity of the developed polymer-based nanoparticles. The drug delivery systems formulated here are promising nanocarriers for FLV delivery and have potential for the treatment of hormone-dependent breast cancers.

Binding mode of triazole derivatives as aromatase inhibitors based on docking, protein ligand interaction fingerprinting, and molecular dynamics simulation studies.

Aromatase inhibitors (AIs) as effective candidates have been used in the treatment of hormone-dependent breast cancer. In this study, we have proposed 300 structures as potential AIs and filtered them by Lipinski's rule of five using DrugLito software. Subsequently, they were subjected to docking simulation studies to select the top 20 compounds based on their Gibbs free energy changes and also to perform more studies on the protein-ligand interaction fingerprint by AuposSOM software. In this stage, anastrozole and letrozole were used as positive control to compare their interaction fingerprint patterns with our proposed structures. Finally, based on the binding energy values, one active structure (ligand 15) was selected for molecular dynamic simulation in order to get information for the binding mode of these ligands within the enzyme cavity. The triazole of ligand 15 pointed to HEM group in aromatase active site and coordinated to Fe of HEM through its N4 atom. In addition, two π-cation interactions was also observed, one interaction between triazole and porphyrin of HEM group, and the other was 4-chloro phenyl moiety of this ligand with Arg115 residue.