Unique SERM-like properties of the novel fluorescent tamoxifen derivative FLTX1

Potential of covalently linked tamoxifen hybrids for cancer treatment: recent update

Cancer is a complex disease and the second leading cause of death globally, and breast cancer is still a leading cause of cancer death in women. Tamoxifen is the most commonly used drug for breast cancer (ER-positive) treatment and chemoprevention, saving the lives of millions of patients every year. In addition, the tamoxifen template has been explored extensively for the development of selective estrogen receptor modulators (SERMs) applicable in breast cancer, osteoporosis, and postmenopausal symptom treatment. Numerous anticancer drugs, including tamoxifen, are in use, but the complexity and heterogeneous nature of cancer complicate the effect of conventional targeted drugs, leading to adverse reactions and resistance. One of the significant approaches to overcome these shortcomings is drug hybrids, generated by covalently linking two or more active pharmacophores. These drug hybrids are remarkably effective in acting on multiple drug targets with higher selectivity and specificity. In recent years, several tamoxifen hybrids have been discovered as potential candidates for cancer treatment. The review highlights the recent progress in developing anticancer hybrids, including organometallic, fluorescent, photocaged, and novel ligand-based tamoxifen hybrids. It also demonstrates the significance of merging various pharmacophores with tamoxifen to produce more potent, precise, and effective anticancer agents. The study offers valuable knowledge to researchers working on cancer research with the hope of enhancing drug potency and reducing drug toxicity to improve cancer patients' lives.

Tamoxifen for the treatment of myeloproliferative neoplasms: A Phase II clinical trial and exploratory analysis

Current therapies for myeloproliferative neoplasms (MPNs) improve symptoms but have limited effect on tumor size. In preclinical studies, tamoxifen restored normal apoptosis in mutated hematopoietic stem/progenitor cells (HSPCs). TAMARIN Phase-II, multicenter, single-arm clinical trial assessed tamoxifen's safety and activity in patients with stable MPNs, no prior thrombotic events and mutated JAK2V617F, CALRins5 or CALRdel52 peripheral blood allele burden ≥20% (EudraCT 2015-005497-38). 38 patients were recruited over 112w and 32 completed 24w-treatment. The study's A'herns success criteria were met as the primary outcome ( ≥ 50% reduction in mutant allele burden at 24w) was observed in 3/38 patients. Secondary outcomes included ≥25% reduction at 24w (5/38), ≥50% reduction at 12w (0/38), thrombotic events (2/38), toxicities, hematological response, proportion of patients in each IWG-MRT response category and ELN response criteria. As exploratory outcomes, baseline analysis of HSPC transcriptome segregates responders and non-responders, suggesting a predictive signature. In responder HSPCs, longitudinal analysis shows high baseline expression of JAK-STAT signaling and oxidative phosphorylation genes, which are downregulated by tamoxifen. We further demonstrate in preclinical studies that in JAK2V617F+ cells, 4-hydroxytamoxifen inhibits mitochondrial complex-I, activates integrated stress response and decreases pathogenic JAK2-signaling. These results warrant further investigation of tamoxifen in MPN, with careful consideration of thrombotic risk.

Research progress on tamoxifen and its analogs associated with nuclear receptors

Tamoxifen, a triphenylethylene-based selective estrogen-receptor modulator, is a landmark drug for the treatment of breast cancer and is also used for treating liver cancer and osteoporosis. Structural studies of tamoxifen have led to the synthesis of more than 20 novel tamoxifen analogs as receptor modulators, including 16 ERα modulators 2-17, an ERRβ inverse agonist 19 and six ERRγ inverse agonists 20-25. This paper summarizes the research progress and structure-activity relationships of tamoxifen analogs modulating these three nuclear receptors reported in the literature, and introduces the relationship between these three nuclear receptor-mediated diseases and tamoxifen analogs to guide the research of novel tamoxifen analogs.

Modulating biomolecular condensates: a novel approach to drug discovery

In the past decade, membraneless assemblies known as biomolecular condensates have been reported to play key roles in many cellular functions by compartmentalizing specific proteins and nucleic acids in subcellular environments with distinct properties. Furthermore, growing evidence supports the view that biomolecular condensates often form by phase separation, in which a single-phase system demixes into a two-phase system consisting of a condensed phase and a dilute phase of particular biomolecules. Emerging understanding of condensate function in normal and aberrant cellular states, and of the mechanisms of condensate formation, is providing new insights into human disease and revealing novel therapeutic opportunities. In this Perspective, we propose that such insights could enable a previously unexplored drug discovery approach based on identifying condensate-modifying therapeutics (c-mods), and we discuss the strategies, techniques and challenges involved.

Discovery of Highly Functionalized 5-hydroxy-2H-pyrrol-2-ones That Exhibit Antiestrogenic Effects in Breast and Endometrial Cancer Cells and Potentiate the Antitumoral Effect of Tamoxifen

Tamoxifen improves the overall survival rate in hormone receptor-positive breast cancer patients. However, despite the fact that it exerts antagonistic effects on the ERα, it can act as a partial agonist, resulting in tumor growth in estrogen-sensitive tissues. In this study, highly functionalized 5-hydroxy-2H-pyrrol-2-ones were synthesized and evaluated by using ERα- and phenotype-based screening assays. Compounds 32 and 35 inhibited 17β-estradiol (E2)-stimulated ERα-mediated transcription of the luciferase reporter gene in breast cancer cells without inhibition of the transcriptional activity mediated by androgen or glucocorticoid receptors. Compound 32 regulated E2-stimulated ERα-mediated transcription by partial antagonism, whereas compound 35 caused rapid and non-competitive inhibition. Monitoring of 2D and 3D cell growth confirmed potent antitumoral effects of both compounds on ER-positive breast cancer cells. Furthermore, compounds 32 and 35 caused apoptosis and blocked the cell cycle of ER-positive breast cancer cells in the sub-G1 and G0/G1 phases. Interestingly, compound 35 suppressed the functional activity of ERα in the uterus, as demonstrated by the inhibition of E2-stimulated transcription of estrogen and progesterone receptors and alkaline phosphatase enzymatic activity. Compound 35 showed a relatively low binding affinity with ERα. However, its antiestrogenic effect was associated with an increased polyubiquitination and a reduced protein expression of ERα. Clinically relevant, a possible combinatory therapy with compound 35 may enhance the antitumoral efficacy of 4-hydroxy-tamoxifen in ER-positive breast cancer cells. In silico ADME predictions indicated that these compounds exhibit good drug-likeness, which, together with their potential antitumoral effects and their lack of estrogenic activity, offers a pharmacological opportunity to deepen the study of ER-positive breast cancer treatment.

Recent advances in estrogen receptor-targeted probes conjugated to BODIPY dyes

Estrogens, is a class of steroid hormones associated with the occurrence and development of breast cancer, that bind to estrogen receptors (ER). The development of BODIPY-based fluorescent ligands for the ER has continued to gain tremendous attention over the past 20 years. This review focuses on the synthesis methods, optical properties, and biological activity of BODIPY fluorescent probes conjugated to ER ligands. These will provide new strategy for designing fluorescent probes for targeting estrogen receptors.

Design, Semisynthesis, and Estrogenic Activity of Lignan Derivatives from Natural Dibenzylbutyrolactones

Based on molecular docking studies on the ERα, a series of lignan derivatives (3–16) were designed and semisynthesized from the natural dibenzylbutyrolactones bursehernin (1) and matairesinol dimethyl ether (2). To examine their estrogenic and antiestrogenic potencies, the effects of these compounds on estrogen receptor element (ERE)-driven reporter gene expression and viability in human ER+ breast cancer cells were evaluated. Lignan compounds induced ERE-driven reporter gene expression with very low potency as compared with the pure agonist E2. However, coincubation of 5 μM of lignan derivatives 1, 3, 4, 7, 8, 9, 11, 13, and 14 with increasing concentrations of E2 (from 0.01 pM to 1 nM) reduced both the potency and efficacy of pure agonists. The binding to the rhERα-LBD was validated by TR-FRET competitive binding assay and lignans bound to the rhERα with IC₅₀ values from 0.16 μM (compound 14) to 6 μM (compound 4). Induced fit docking (IFD) and molecular dynamics (MD) simulations for compound 14 were carried out to further investigate the binding mode interactions. Finally, the in silico ADME predictions indicated that the most potent lignan derivatives exhibited good drug-likeness.

FLTX2: A Novel Tamoxifen Derivative Endowed with Antiestrogenic, Fluorescent, and Photosensitizer Properties

Tamoxifen is the most widely used selective modulator of estrogen receptors (SERM) and the first strategy as coadjuvant therapy for the treatment of estrogen-receptor (ER) positive breast cancer worldwide. In spite of such success, tamoxifen is not devoid of undesirable effects, the most life-threatening reported so far affecting uterine tissues. Indeed, tamoxifen treatment is discouraged in women under risk of uterine cancers. Recent molecular design efforts have endeavoured the development of tamoxifen derivatives with antiestrogen properties but lacking agonistic uterine tropism. One of this is FLTX2, formed by the covalent binding of tamoxifen as ER binding core, 7-nitrobenzofurazan (NBD) as the florescent dye, and Rose Bengal (RB) as source for reactive oxygen species. Our analyses demonstrate (1) FLTX2 is endowed with similar antiestrogen potency as tamoxifen and its predecessor FLTX1, (2) shows a strong absorption in the blue spectral range, associated to the NBD moiety, which efficiently transfers the excitation energy to RB through intramolecular FRET mechanism, (3) generates superoxide anions in a concentration- and irradiation time-dependent process, and (4) Induces concentration- and time-dependent MCF7 apoptotic cell death. These properties make FLTX2 a very promising candidate to lead a novel generation of SERMs with the endogenous capacity to promote breast tumour cell death in situ by photosensitization.

FRET mechanism between a fluorescent breast-cancer drug and photodynamic therapy sensitizers

Tamoxifen is one of the most frequently used drugs for the treatment of estrogen receptor positive breast cancer, which is the most prevalent form of hormone dependent breast cancer. A few years ago, we developed a fluorescent derivative of tamoxifen formed by the covalent binding of tamoxifen to a common dye biomarker. The new compound, known as FLTX1, showed the pharmacological activity of the tamoxifen moiety and efficient fluorescence properties, which could be used synergistically to improve the effect of the drug. In this paper, we demonstrate that irradiation at the absorption band of FLTX1 can result in fluorescence resonance energy transfer to photosensitizers such as Rose Bengal and Merocyanine 540, activating the production of reactive oxygen species (ROS). Indeed, the generation of ROS was demonstrated using a colorimetric assay. Since FLTX1 mostly binds estrogen-receptor overexpressing cancer cells, the results obtained are very promising and suggest a new therapeutic strategy combining chemo- and photodynamic therapies.

Rational design of ERα targeting hypoxia turn-on fluorescent probes with antiproliferative activity for breast cancer

The overexpression of estrogen receptor (ER) α is not only closely related to the development of ER⁺ breast cancer, but is also an important biomarker for clinical diagnosis and treatment. Herein, we report several ERα targeting hypoxia turn-on fluorescent probes with antitumor activity for breast cancer cells. Among them, probes 3 and 5 displayed good ERα targeting ability and favorable hypoxia turn-on response in MCF-7 cells. Moreover, the probes 3 and 5 exhibited good antiproliferative activity towards MCF-7 cells (IC₅₀ = 8.5 μM, 10.3 μM) and a much lower cytotoxicity to normal cells compared with the positive control. It is expected that these novel fluorescent probes may provide useful tools for the theranostics of ER⁺ breast cancer.

Partitioning of cancer therapeutics in nuclear condensates

The nucleus contains diverse phase-separated condensates that compartmentalize and concentrate biomolecules with distinct physicochemical properties. Here, we investigated whether condensates concentrate small-molecule cancer therapeutics such that their pharmacodynamic properties are altered. We found that antineoplastic drugs become concentrated in specific protein condensates in vitro and that this occurs through physicochemical properties independent of the drug target. This behavior was also observed in tumor cells, where drug partitioning influenced drug activity. Altering the properties of the condensate was found to affect the concentration and activity of drugs. These results suggest that selective partitioning and concentration of small molecules within condensates contributes to drug pharmacodynamics and that further understanding of this phenomenon may facilitate advances in disease therapy.

Review of fluorescent steroidal ligands for the estrogen receptor 1995-2018

The development of fluorescent ligands for the estrogen receptor (ER) continues to be of interest. Over the past 20 years, most efforts have focused on appending an expanding variety of fluorophores to the B-, C- and D-rings of the steroidal scaffold. This review highlights the synthesis and evaluation of derivatives substituted primarily at the 6-, 7α- and 17α-positions, culminating with our recent work on 11β-substituted estradiols, and proposes an approach to new fluorescent imaging agents that retain high ER affinity.

A new selective fluorescent probe based on tamoxifen

Developing targeted validation probes that can interrogate biology is of interest for both chemists and biologists. The synthesis of suitable compounds provides a means for avoiding the costly labeling of cells with specific antibodies and the bias associated with the interpretation of biological validation experiments. The chemotherapeutic agent, tamoxifen has been routinely used in the treatment of breast cancer for decades. Once metabolized, the active form of tamoxifen (4-hydroxytamoxifen) competes with the binding of estrogens to the estrogen receptors (ER). Its selectivity in ER modulation makes it an ideal candidate for the development of materials to be used as chemical probes. Here we report the synthesis of a fluorescent BODIPY®FL conjugate of tamoxifen linked through an ethylene glycol moiety, and present proof-of-principle results in ER positive and ER negative cell lines. Optical microscopy indicates that the fluorescent probe binds selectively to tamoxifen sensitive breast cancer cell lines. The compound showed no affinity for the tamoxifen resistant breast cancer lines. The specificity of the new compound make it a valuable addition to the chemical probe tool kit for estrogen receptors.

Colocalization of Estrogen Receptors with the Fluorescent Tamoxifen Derivative, FLTX1, Analyzed by Confocal Microscopy

Tamoxifen is a selective estrogen receptor modulator that competitively binds the ligand-binding domain of estrogen receptors. Binding of tamoxifen displaces its cognate ligand, 17β-estradiol, thereby hampering the activation of estrogen receptors. Cellular labeling of ER is typically carried out using specific antibodies which require permeabilization of cells, incubation with secondary antibodies, and are expensive and time consuming. In this article, we describe the usefulness of FLTX1, a novel fluorescent tamoxifen derivative, which allows the labeling of estrogen receptors in immunocytochemistry and immunohistochemistry studies, both under permeabilized and non-permeabilized conditions. Further, besides labeling canonical estrogen receptors, this novel fluorescent probe is also suitable for the identification of unconventional targets such membrane estrogen receptors as well as other noncanonical targets, some of which are likely responsible for the number of undesired side effects reported during long-term tamoxifen treatments.

Estrogen Receptor Ligands: A Review (2013-2015)

Estrogen receptors (ERs) are a group of compounds named for their importance in both menstrual and estrous reproductive cycles. They are involved in the regulation of various processes ranging from tissue growth maintenance to reproduction. Their action is mediated through ER nuclear receptors. Two subtypes of the estrogen receptor, ERα and ERβ, exist and exhibit distinct cellular and tissue distribution patterns. In humans, both receptor subtypes are expressed in many cells and tissues, and they control key physiological functions in various organ systems. Estrogens attract great attention due to their wide applications in female reproductive functions and treatment of some estrogen-dependent cancers and osteoporosis. This paper provides a general review of ER ligands published in international journals patented between 2013 and 2015. The broad physiological profile of estrogens has attracted the attention of many researchers to develop new estrogen ligands as therapeutic molecules for various clinical purposes. After the discovery of the ERβ receptor, subtype-selective ligands could be used to elicit beneficial estrogen-like activities and reduce adverse side effects, based on the different distributions and relative levels of the two ER subtypes in different estrogen target tissues. Therefore, recent literature has focused on selective estrogen ligands as highly promising agents for the treatment of some types of cancer, as well as for cardiovascular, inflammatory, and neurodegenerative diseases. Estrogen receptors are nuclear transcription factors that are involved in the regulation of many complex physiological functions in humans. Selective estrogen ligands are highly promising targets for treatment of some types of cancer, as well as for cardiovascular, inflammatory and neurodegenerative diseases. Extensive structure-activity relationship studies of ER ligands based on small molecules indicate that many different structural scaffolds may provide high-affinity compounds, provided that some basic structural requirements are present.