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

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.

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, ERβ 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, 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.