Steroidal epoxides as anticancer agents in lung, prostate and breast cancers: The case of 1,2-epoxysteroids.

Cancer continues to be a serious threat to human health worldwide. Lung, prostate and triple-negative breast cancers are amongst the most incident and deadliest cancers. Steroidal compounds are one of the most diversified therapeutic classes of compounds and they were proven to be efficient against several types of cancer. The epoxide function has been frequently associated with anticancer activity, particularly the 1,2-epoxide function. For this reason, three 1,2-epoxysteroid derivatives previously synthesised (EP1, EP2 and EP3) and one synthesised for the first time (oxysteride) were evaluated against H1299 (lung), PC3 (prostate) and HCC1806 (triple-negative breast) cancer cell lines. A human non-tumour cell line, MRC-5 (normal lung cell line) was also used. EP2 was the most active compound in all cell lines with IC50 values of 2.50, 3.67 and 1.95 µM, followed by EP3 with IC50 values of 12.65, 15.10 and 14.16 µM in H1299, PC3 and HCC1806 cells, respectively. Additional studies demonstrated that EP2 and EP3 induced cell death by apoptosis at lower doses and apoptosis/necrosis at higher doses, proving that their effects were dose-dependent. Both compounds also exerted their cytotoxicity by ROS production and by inducing double-strand breaks. Furthermore, EP2 and EP3 proved to be much less toxic against a normal lung cell line, MRC5, indicating that both compounds might be selective, and they also demonstrated suitable in silico ADME and toxicity parameters. Finally, none of the compounds induced haemoglobin release. Altogether, these results point out the extreme relevance of both compounds, especially EP2, in the potential treatment of these types of cancer.

Synthetic and natural guanidine derivatives as antitumor and antimicrobial agents: A review.

Guanidines are fascinating small nitrogen-rich organic compounds, which have been frequently associated with a wide range of biological activities. This is mainly due to their interesting chemical features. For these reasons, for the past decades, researchers have been synthesizing and evaluating guanidine derivatives. In fact, there are currently on the market several guanidine-bearing drugs. Given the broad panoply of pharmacological activities displayed by guanidine compounds, in this review, we chose to focus on antitumor, antibacterial, antiviral, antifungal, and antiprotozoal activities presented by several natural and synthetic guanidine derivatives, which are undergoing preclinical and clinical studies from January 2010 to January 2023. Moreover, we also present guanidine-containing drugs currently in the market for the treatment of cancer and several infectious diseases. In the preclinical and clinical setting, most of the synthesized and natural guanidine derivatives are being evaluated as antitumor and antibacterial agents. Even though DNA is the most known target of this type of compounds, their cytotoxicity also involves several other different mechanisms, such as interference with bacterial cell membranes, reactive oxygen species (ROS) formation, mitochondrial-mediated apoptosis, mediated-Rac1 inhibition, among others. As for the compounds already used as pharmacological drugs, their main application is in the treatment of different types of cancer, such as breast, lung, prostate, and leukemia. Guanidine-containing drugs are also being used for the treatment of bacterial, antiprotozoal, antiviral infections and, recently, have been proposed for the treatment of COVID-19. To conclude, the guanidine group is a privileged scaffold in drug design. Its remarkable cytotoxic activities, especially in the field of oncology, still make it suitable for a deeper investigation to afford more efficient and target-specific drugs.

The Structural Diversity and Biological Activity of Steroid Oximes.

Steroids and their derivatives have been the subject of extensive research among investigators due to their wide range of pharmacological properties, in which steroidal oximes are included. Oximes are a chemical group with the general formula R1R2C=N-OH and they exist as colorless crystals and are poorly soluble in water. Oximes can be easily obtained through the condensation of aldehydes or ketones with various amine derivatives, making them a very interesting chemical group in medicinal chemistry for the design of drugs as potential treatments for several diseases. In this review, we will focus on the different biological activities displayed by steroidal oximes such as anticancer, anti-inflammatory, antibacterial, antifungal and antiviral, among others, as well as their respective mechanisms of action. An overview of the chemistry of oximes will also be reported, and several steroidal oximes that are in clinical trials or already used as drugs are described. An extensive literature search was performed on three main databases-PubMed, Web of Science, and Google Scholar.

An Exemestane Derivative, Oxymestane-D1, as a New Multi-Target Steroidal Aromatase Inhibitor for Estrogen Receptor-Positive (ER+) Breast Cancer: Effects on Sensitive and Resistant Cell Lines.

Around 70-85% of all breast cancer (BC) cases are estrogen receptor-positive (ER+). The third generation of aromatase inhibitors (AIs) is the first-line treatment option for these tumors. Despite their therapeutic success, they induce several side effects and resistance, which limits their efficacy. Thus, it is crucial to search for novel, safe and more effective anti-cancer molecules. Currently, multi-target drugs are emerging, as they present higher efficacy and lower toxicity in comparison to standard options. Considering this, this work aimed to investigate the anti-cancer properties and the multi-target potential of the compound 1α,2α-epoxy-6-methylenandrost-4-ene-3,17-dione (Oxy), also designated by Oxymestane-D1, a derivative of Exemestane, which we previously synthesized and demonstrated to be a potent AI. For this purpose, it was studied for its effects on the ER+ BC cell line that overexpresses aromatase, MCF-7aro cells, as well as on the AIs-resistant BC cell line, LTEDaro cells. Oxy reduces cell viability, impairs DNA synthesis and induces apoptosis in MCF-7aro cells. Moreover, its growth-inhibitory properties are inhibited in the presence of ERα, ERß and AR antagonists, suggesting a mechanism of action dependent on these receptors. In fact, Oxy decreased ERα expression and activation and induced AR overexpression with a pro-death effect. Complementary transactivation assays demonstrated that Oxy presents ER antagonist and AR agonist activities. In addition, Oxy also decreased the viability and caused apoptosis of LTEDaro cells. Therefore, this work highlights the discovery of a new and promising multi-target drug that, besides acting as an AI, appears to also act as an ERα antagonist and AR agonist. Thus, the multi-target action of Oxy may be a therapeutic advantage over the three AIs applied in clinic. Furthermore, this new multi-target compound has the ability to sensitize the AI-resistant BC cells, which represents another advantage over the endocrine therapy used in the clinic, since resistance is a major drawback in the clinic.

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

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

Design, synthesis, and antitumor activity evaluation of steroidal oximes.

Steroidal compounds were proven to be efficient drugs against several types of cancer. Oximes are also chemical structures frequently associated with anticancer activity. The main goal of this work was to combine the two referred structures by synthesizing steroidal oximes and evaluating them in several cancer cell lines. Compounds (17E)-5α-androst-3-en-17-one oxime (3,4 - OLOX), (17E)-3α,4α-epoxy-5α-androstan-17-one oxime (3,4 - EPOX), (17E)-androst-4-en-17-one oxime (4,5 - OLOX) and (17E)-4α,5α-epoxyandrostan-17-one oxime (4,5 - EPOX) were synthesized and their cytotoxicity evaluated in four human cancer cell lines, namely colorectal adenocarcinoma (WiDr), non-small cell lung cancer (H1299), prostate cancer (PC3) and hepatocellular carcinoma (HepG2). A human non-tumour cell line, CCD841 CoN (normal colon cell line) was also used. MTT assay, flow cytometry, fluorescence and hemocompatibility techniques were performed to further analyse the cytotoxicity of the compounds. 3,4 - OLOX was the most effective compound in decreasing tumour cell proliferation in all cell lines, especially in WiDr (IC50 = 9.1 µM) and PC3 (IC50 = 13.8 µM). 4,5 - OLOX also showed promising results in the same cell lines (IC50 = 16.1 µM in WiDr and IC50 = 14.5 µM in PC3). Further studies also revealed that 3,4 - OLOX and 4,5 - OLOX induced a decrease in cell viability accompanied by an increase in cell death, mainly by apoptosis/necroptosis for 3,4 - OLOX in both cell lines and for 4,5 - OLOX in WiDr cells, and by necrosis for 4,5 - OLOX in PC3 cells. These compounds might also exert their cytotoxicity by ROS production and are not toxic for non-tumour CCD841 CoN cells. Additionally, both compounds did not induce haemoglobin release, proving to be safe for intravenous administration. 3,4 - OLOX and 4,5 - OLOX might be the starting point for an optimization program towards the discover of new steroidal oximes for anticancer treatment.

Oxymestane, a cytostatic steroid derivative of exemestane with greater antitumor activity in non-estrogen-dependent cell lines.

A new promising steroid derivative of Exemestane (Exe), the drug used for the treatment of estrogen-dependent breast cancer, was synthesized and evaluated against a set of human cancer cell lines. The new compound (Oxymestane-D1, Oxy) was tested comparatively with Exe against colon (C2BBe1, WiDr), liver (HepG2, HuH-7), lung (A549, H1299) and prostate (LNCaP, PC3) human cancer cell lines. Likewise, its effect on human colon normal cells (CCD-841 CoN) and human normal fibroblast cells (HFF-1) was studied. The cytostatic activity of Oxy was also compared with that of the reference cytostatic drugs used in chemotherapy protocols, namely carboplatin, cisplatin, doxorubicin, epirubicin, etoposide, flutamide, 5-fluorouracil, irinotecan, oxaliplatin and sorafenib. In all cell lines tested, Oxy proved to be more powerful cytostatic than Exe. Additionally, the IC50 at 72 h showed a three-fold activity greater than 5-fluorouracil in the WiDr cell line, twice as high as cisplatin for cell line A549 and five times higher than cisplatin for cell line H1299. Also, Oxy surprisingly revealed to induce DNA damage and inhibit the DNA damage response (DDR) proteins ATM, ATR, CHK1 and CHK2. The results obtained allow concluding that Oxy can be a promising anticancer agent to be used in chemotherapy protocols. Furthermore, its ability to inhibit crucial components of DDR can also be useful for the monotherapy or for combination with chemo and/or radiotherapy of cancer.

Epoxide containing molecules: A good or a bad drug design approach.

Functional group modification is one of the main strategies used in drug discovery and development. Despite the controversy of being identified for many years as a biologically hazardous functional group, the introduction of an epoxide function in a structural backbone is still one of the possible modifications being implemented in drug design. In this manner, it is our intention to prove with this work that epoxides can have significant interest in medicinal chemistry, not only as anticancer agents, but also as important drugs for other pathologies. Thus, this revision paper aims to highlight the biological activity and the proposed mechanisms of action of several epoxide-containing molecules either in preclinical studies or in clinical development or even in clinical use. An overview of the chemistry of epoxides is also reported. Some of the conclusions are that effectively most of the epoxide-containing molecules referred in this work were being studied or are in the market as anticancer drugs. However, some of them in preclinical studies, were also associated with other different activities such as anti-malarial, anti-arthritic, insecticidal, antithrombotic, and selective inhibitory activity of FXIII-A (a transglutaminase). As for the epoxide-containing molecules in clinical trials, some of them are being tested for obesity and schizophrenia. Finally, drugs containing epoxide groups already in the market are mostly used for the treatment of different types of cancer, such as breast cancer and multiple myeloma. Other diseases for which the referred drugs are being used include heart failure, infections and gastrointestinal disturbs. In summary, epoxides can be a suitable option in drug design, particularly in the design of anticancer agents, and deserve to be better explored. However, and despite the promising results, it is imperative to explore the mechanisms of action of these compounds in order to have a better picture of their efficiency and safety.

New phenolic cinnamic acid derivatives as selective COX-2 inhibitors. Design, synthesis, biological activity and structure-activity relationships.

Selective inhibition of cyclooxygenase (COX)-2 enzyme is an important achievement when looking for potent anti-inflammatory agents, with fewer gastrointestinal side effects. In this work, a new series of cinnamic acid derivatives, namely hexylamides, have been designed, synthesized and evaluated in human blood for their inhibitory activity of COX-1 and COX-2 enzymes. From this, new structure-activity relationships were built, showing that phenolic hydroxyl groups are essential for both COX-1 and COX-2 inhibition. Furthermore, the presence of bulky hydrophobic di-tert-butyl groups in the phenyl ring strongly contributes for selective COX-2 inhibition. In addition, a correlation with the theoretical log P has been carried out, showing that lipophilicity is particularly important for COX-2 inhibition. Further, a plasma protein binding (PPB) prediction has been performed revealing that PPB seems to have no influence in the activity of the studied compounds. From the whole study, effective selective inhibitors of COX-2 were found, namely compound 9 (IC50 = 3.0 ±â€¯0.3 µM), 10 (IC50 = 2.4 ±â€¯0.6 µM) and 23 (IC50 = 1.09 ±â€¯0.09 µM). Those can be considered starting point hit compounds for further optimization as potential non-steroidal anti-inflammatory drugs.

C-6α- vs C-7α-Substituted Steroidal Aromatase Inhibitors: Which Is Better? Synthesis, Biochemical Evaluation, Docking Studies, and Structure-Activity Relationships.

C-6α and C-7α androstanes were studied to disclose which position among them is more convenient to functionalize to reach superior aromatase inhibition. In the first series, the study of C-6 versus C-7 methyl derivatives led to the very active compound 9 with IC50 of 0.06 µM and Ki = 0.025 µM (competitive inhibition). In the second series, the study of C-6 versus C-7 allyl derivatives led to the best aromatase inhibitor 13 of this work with IC50 of 0.055 µM and Ki = 0.0225 µM (irreversible inhibition). Beyond these findings, it was concluded that position C-6α is better to functionalize than C-7α, except when there is a C-4 substituent simultaneously. In addition, the methyl group was the best substituent, followed by the allyl group and next by the hydroxyl group. To rationalize the structure-activity relationship of the best inhibitor 13, molecular modeling studies were carried out.

miR-145-loaded micelleplexes as a novel therapeutic strategy to inhibit proliferation and migration of osteosarcoma cells.

Osteosarcoma (OS), the main primary malignancy of bone, is the second leading cause of cancer in children and young adults. Despite the advances in modern treatments, the 5-year survival rate is retained in 60-70%, since the conventional treatment options available are associated with relapse, chemoresistance, and development of metastases, which frequently lead to patients death. In this regard, there is an increasing need to search and develop novel and alternative therapeutic approaches. Concerning this, gene therapy appears as an innovative and promising treatment option. This therapeutic option aims to deliver genetic material, through nanosystems, to repress or replace the expression of mutated genes involved in important regulatory pathways. To attain this goal, gene therapy is decidedly dependent on the efficiency of utilized vectors, constituting such a very important parameter to take in consideration. In this work, the main goal was centered on the development and full characterization of an efficient micellar nanosystem, based on the chemical conjugation between the amphiphilic copolymer Pluronic® L64 and the cationic polymer polyethyleneimine (PEI), to deliver the therapeutic miRNA-145 into OS cells leading to inhibition of cell proliferation and migration, and ultimately inducing cell death, crafting a novel anticancer therapeutic approach to OS.

Hormone-dependent breast cancer: Targeting autophagy and PI3K overcomes Exemestane-acquired resistance.

The leading cause of cancer death in women around the world is breast cancer. The aromatase inhibitors (AIs) are considered - as first-line treatment for estrogen receptor-positive (ER+) breast tumors, in postmenopausal women. Exemestane (Exe) is a powerful steroidal AI, however, despite its therapeutic success, Exe-acquired resistance may occur leading to tumor relapse. Our group previously demonstrated that autophagy acts as a pro-survival process in Exe-induced cell death of ER+ sensitive breast cancer cells. In this work, the role of autophagy and its relationship with the PI3K/AKT/mTOR pathway in Exe-acquired resistance was explored. In that way, the mechanism behind the effects of the combination of Exe with pan-PI3K, or autophagic inhibitors, was studied in a long-term estrogen deprived ER+ breast cancer cell line (LTEDaro cells). Our results indicate that Exe induces autophagy as a cytoprotective mechanism linked to acquired resistance. Moreover, it was demonstrated that by inhibiting autophagy and/or PI3K pathway it is possible to revert Exe-resistance through apoptosis promotion, disruption of cell cycle, and inhibition of cell survival pathways. This work provides new insights into the mechanisms involved in Exe-acquired resistance, pointing autophagy as an attractive therapeutic target to surpass it. Thus, it highlights new targets that together with aromatase inhibition may improve ER+ breast cancer therapy, overcoming AIs-acquired resistance.

Anti-tumor efficacy of new 7α-substituted androstanes as aromatase inhibitors in hormone-sensitive and resistant breast cancer cells.

The majority of breast cancer cases are estrogen receptor positive (ER+). Although, third-generation aromatase inhibitors (AIs) are used as first-line treatment in post-menopausal women, they cause endocrine resistance and bone loss, which limits their success. Therefore, there is a demand to discover new potent molecules, with less toxicity that can circumvent these drawbacks. Our group has previously demonstrated that new 7α-substituted steroidal molecules, 7α-(2ξ,3ξ-epoxypropyl)androsta-1,4-diene-3,17-dione (3), 7α-allylandrost-4-ene-3,17-dione (6), 7α-allylandrost-4-en-17-one (9), 7α-allyl-3-oxoandrosta-1,4-dien-17ß-ol (10) and 7α-allylandrosta-1,4-diene-3,17-dione (12) are potent AIs in placental microsomes. In this work, it was investigated their anti-aromatase activity and in vitro effects in sensitive and resistant breast cancer cells. All the steroids efficiently inhibit aromatase in breast cancer cells, allowing to establish new structure-activity relationships for this class of compounds. Moreover, the new AIs can inhibit breast cancer cell growth, by causing cell cycle arrest and apoptosis. The effects of AIs 3 and 12 on sensitive cells were dependent on aromatase inhibition and androgen receptor (AR), while for AI 9 and AI 10 were AR- and ER-dependent, respectively. In addition, it was shown that all the AIs can sensitize resistant cancer cells being their behavior similar to the sensitive cells. In summary, this study contributes to the understanding of the structural modifications in steroidal scaffold that are translated into better aromatase inhibition and anti-tumor properties, providing important information for the rational design/synthesis of more effective AIs. In addition, allowed the discovery of new potent 7α-substituted androstane molecules to inhibit tumor growth and prevent endocrine resistance.

Combined dual effect of modulation of human neutrophils' oxidative burst and inhibition of colon cancer cells proliferation by hydroxycinnamic acid derivatives.

Colon cancer is one of the most incident cancers in the Western World. While both genetic and epigenetic factors may contribute to the development of colon cancer, it is known that chronic inflammation associated to excessive production of reactive oxygen and nitrogen species by phagocytes may ultimately initiate the multistep process of colon cancer development. Phenolic compounds, which reveal antioxidant and antiproliferative activities in colon cancer cells, can be a good approach to surpass this problem. In this work, hydroxycinnamic amides and the respective acid precursors were tested in vitro for their capacity to modulate human neutrophils' oxidative burst and simultaneously to inhibit growth of colon cancer cells. A phenolic amide derivative, caffeic acid hexylamide (CAHA) (4) was found to be the most active compound in both assays, inhibiting human neutrophils' oxidative burst, restraining the inflammatory process, inhibiting growth of colon cancer cells and triggering mitochondrial dysfunction that leads cancer cells to apoptosis. Altogether, these achievements can contribute to the understanding of the relationship between antioxidant and anticancer activities and based on the structure-activity relationships (SAR) established can be the starting point to find more effective phenolic compounds as anticancer agents.

Exploring new chemical functionalities to improve aromatase inhibition of steroids.

In this work, new potent steroidal aromatase inhibitors both in microsomes and in breast cancer cells have been found. The synthesis of the 3,4-(ethylenedioxy)androsta-3,5-dien-17-one (12), a new steroid containing a heterocycle dioxene fused in the A-ring, led to the discovery of a new reaction for which a mechanism is proposed. New structure-activity relationships were established. Some 5ß-steroids, such as compound 4ß,5ß-epoxyandrostan-17-one (9), showed aromatase inhibitory activity, because they adopt a similar A-ring conformation as those of androstenedione, the natural substrate of aromatase. Moreover, new chemical features to increase planarity were disclosed, specifically the 3α,4α-cyclopropane ring, as in 3α,4α-methylen-5α-androstan-17-one (5) (IC50=0.11µM), and the Δ(9-11) double bond in the C-ring, as in androsta-4,9(11)-diene-3,17-dione (13) (IC50=0.25µM). In addition, induced-fit docking (IFD) simulations and site of metabolism (SoM) predictions helped to explain the recognition of new potent steroidal aromatase inhibitors within the enzyme. These insights can be valuable tools for the understanding of the molecular recognition process by the aromatase and for the future design of new steroidal inhibitors.

Exemestane metabolites suppress growth of estrogen receptor-positive breast cancer cells by inducing apoptosis and autophagy: A comparative study with Exemestane.

Around 60-80% of all breast tumors are estrogen receptor-positive. One of the several therapeutic approaches used for this type of cancers is the use of aromatase inhibitors. Exemestane is a third-generation steroidal aromatase inhibitor that undergoes a complex and extensive metabolism, being catalytically converted into chemically active metabolites. Recently, our group showed that the major exemestane metabolites, 17ß-hydroxy-6-methylenandrosta-1,4-dien-3-one and 6-(hydroxymethyl)androsta-1,4,6-triene-3,17-dione, as well as, the intermediary metabolite 6ß-Spirooxiranandrosta-1,4-diene-3,17-dione, are potent aromatase inhibitors in breast cancer cells. In this work, in order to better understand the biological mechanisms of exemestane in breast cancer and the effectiveness of its metabolites, it was investigated their effects in sensitive and acquired-resistant estrogen receptor-positive breast cancer cells. Our results indicate that metabolites induced, in sensitive breast cancer cells, cell cycle arrest and apoptosis via mitochondrial pathway, involving caspase-8 activation. Moreover, metabolites also induced autophagy as a promoter mechanism of apoptosis. In addition, it was demonstrated that metabolites can sensitize aromatase inhibitors-resistant cancer cells, by inducing apoptosis. Therefore, this study indicates that exemestane after metabolization originates active metabolites that suppress the growth of sensitive and resistant breast cancer cells. It was also concluded that, in both cell lines, the biological effects of metabolites are different from the ones of exemestane, which suggests that exemestane efficacy in breast cancer treatment may also be dependent on its metabolites.

Plant derived and dietary phenolic antioxidants: anticancer properties.

In this paper, a review of the literature on the phenolic compounds with anticancer activity published between 2008 and 2012 is presented. In this overview only phenolic antioxidant compounds that display significant anticancer activity have been described. In the first part of this review, the oxidative and nitrosative stress relation with cancer are described. In the second part, the plant-derived food extracts, containing identified phenolic antioxidants, the phenolic antioxidants isolated from plants and plant-derived food or commercially available and the synthetic ones, along with the type of cancer and cells where they exert anticancer activity, are described and summarized in tables. The principal mechanisms for their anti-proliferative effects were also described. Finally, a critical analysis of the studies and directions for future research are included in the conclusion.

Exemestane metabolites: Synthesis, stereochemical elucidation, biochemical activity and anti-proliferative effects in a hormone-dependent breast cancer cell line.

Exemestane is a third-generation steroidal aromatase inhibitor that has been used in clinic for hormone-dependent breast cancer treatment in post-menopausal women. It is known that exemestane undergoes a complex metabolization, giving rise to some already identified metabolites, the 17ß-hydroxy-6-methylenandrosta-1,4-dien-3-one (17-ßHE) and the 6-(hydroxymethyl)androsta-1,4,6-triene-3,17-dione (6-HME). In this study, four metabolites of exemestane have been analyzed, three of them were synthesized (6ß-spirooxiranandrosta-1,4-diene-3,17-dione (2), 1α,2α-epoxy-6-methylenandrost-4-ene-3,17-dione (3) and 17-ßHE (4)) while one was acquired, the 6-HME (6). The stereochemistry of the epoxide group of 2 and 3 has been unequivocally elucidated for the first time on the basis of NOESY experiments. New structure-activity relationships (SAR) have been established through the observation that the substitution of the double bonds by epoxide groups led to less potent derivatives in microsomes. However, the reduction of the C-17 carbonyl group to a hydroxyl group originating 17-ßHE (4) resulted in a significant increase in activity in MCF-7aro cells when compared to exemestane (IC50 0.25 µM vs 0.90 µM, respectively). All the studied metabolites reduced MCF-7aro cells viability in a dose and time-dependent manner, and metabolite 3 was the most potent one. Altogether our results showed that not only exemestane but also its main metabolites are potent aromatase inhibitors and reduce breast cancer cells viability. This suggests that exemestane efficacy may also be due to the active metabolites that result from its metabolic transformation. Our results emphasize the importance of performing further studies to expand our understanding of exemestane actions in breast cancer cells.

New steroidal 17ß-carboxy derivatives present anti-5α-reductase activity and anti-proliferative effects in a human androgen-responsive prostate cancer cell line.

The androgens testosterone (T) and dihydrotestosterone (DHT), besides playing an important role in prostate development and growth, are also responsible for the development and progression of benign prostate hyperplasia (BPH) and prostate cancer. Therefore, the actions of these hormones can be antagonized by preventing the irreversible conversion of T into DHT by inhibiting 5α-reductase (5α-R). This has been a useful therapeutic approach for the referred diseases and can be achieved by using 5α-reductase inhibitors (RIs). Steroidal RIs, finasteride and dutasteride, are used in clinic for BPH treatment and were also proposed for chemoprevention of prostate cancer. Nevertheless, due to the increase in bone and muscle loss, impotency and occurrence of high-grade prostate tumours, it is important to seek for other potent and specific molecules with lower side effects. In the present work, we designed and synthesized steroids with the 3-keto-Δ(4) moiety in the A-ring, as in the 5α-R substrate T, and with carboxamide, carboxyester or carboxylic acid functions at the C-17ß position. The inhibitory 5α-R activity, in human prostate microsomes, as well as the anti-proliferative effects of the most potent compounds, in a human androgen-responsive prostate cancer cell line (LNCaP cells), were investigated. Our results showed that steroids 3, 4 and 5 are good RIs, which suggest that C-17ß lipophylic amides favour 5α-R inhibition. Moreover, these steroids induce a decrease in cell viability of stimulated LNCaP cells, in a 5α-R dependent-manner, similarly to finasteride.

Steroidal aromatase inhibitors inhibit growth of hormone-dependent breast cancer cells by inducing cell cycle arrest and apoptosis.

Different hormonal therapies are used for estrogen receptor positive (ER(+)) breast cancers, being the third-generation of aromatase inhibitors (AIs), an effective alternative to the classical tamoxifen. AIs inhibit the enzyme aromatase, which is responsible for catalyzing the conversion of androgens to estrogens. In this study, it was evaluated the effects of several steroidal AIs, namely 3ß-hydroxyandrost-4-en-17-one (1), androst-4-en-17-one (12), 4α,5α-epoxyandrostan-17-one (13a) and 5α-androst-2-en-17-one (16), on cell proliferation, cell cycle progression and cell death in an ER(+) aromatase-overexpressing human breast cancer cell line (MCF-7aro). All AIs induced a decrease in cell proliferation and these anti-proliferative effects were due to a disruption in cell cycle progression and cell death, by apoptosis. AIs 1 and 16 caused cell cycle arrest in G0/G1, while AIs 12 and 13a induced an arrest in G2/M. Moreover, it was observed that these AIs induced apoptosis by different pathways, since AIs 1, 12 and 13a activated the apoptotic mitochondrial pathway, while AI 16 induced apoptosis through activation of caspase-8. These results are important for the elucidation of the cellular effects of steroidal AIs on breast cancer cells and will also highlight the importance of AIs as inducers of apoptosis in hormone-dependent breast cancers.