β-Lactam type molecular scaffolds for antiproliferative activity: Synthesis and cytotoxic effects in breast cancer cells

Investigation of the Antitumor Effects of Tamoxifen and Its Ferrocene-Linked Derivatives on Pancreatic and Breast Cancer Cell Lines

Tamoxifen is a long-known anti-tumor drug, which is the gold standard therapy in estrogen receptor (ER) positive breast cancer patients. According to previous studies, the conjugation of the original tamoxifen molecule with different functional groups can significantly improve its antitumor effect. The purpose of this research was to uncover the molecular mechanisms behind the cytotoxicity of different ferrocene-linked tamoxifen derivates. Tamoxifen and its ferrocene-linked derivatives, T5 and T15 were tested in PANC1, MCF7, and MDA-MB-231 cells, where the incorporation of the ferrocene group improved the cytotoxicity on all cell lines. PANC1, MCF7, and MDA-MB-231 express ERα and GPER1 (G-protein coupled ER 1). However, ERβ is only expressed by MCF7 and MDA-MB-231 cells. Tamoxifen is a known agonist of GPER1, a receptor that can promote tumor progression. Analysis of the protein expression profile showed that while being cytotoxic, tamoxifen elevated the levels of different tumor growth-promoting factors (e.g., Bcl-XL, Survivin, EGFR, Cathepsins, chemokines). On the other hand, the ferrocene-linked derivates were able to lower these proteins. Further analysis showed that the ferrocene-linked derivatives significantly elevated the cellular oxidative stress compared to tamoxifen treatment. In conclusion, we were able to find two molecules possessing better cytotoxicity compared to their unmodified parent molecule while also being able to counter the negative effects of the presence of the GPER1 through the ER-independent mechanism of oxidative stress induction.

Recent Advances in β-lactam Derivatives as Potential Anticancer Agents

Cancer, accounts for around 10 million deaths annually, is the second leading cause of death globally. The continuous emergency of drug-resistant cancers and the low specificity of anticancer agents are the main challenges in the control and eradication of cancers, so it is imperative to develop novel anticancer agents. Immense efforts have been made in developing new lead compounds and novel chemotherapeutic strategies for the treatment of various forms of cancers in recent years. β-Lactam derivatives constitute versatile and attractive scaffolds for the drug discovery since these kinds of compounds possess a variety of pharmacological properties, and some of them exhibited promising potency against both drug-sensitive and drug-resistant cancer cell lines. Thus, β-lactam moiety is a useful template for the development of novel anticancer agents. This review will provide an overview of β-lactam derivatives with the potential therapeutic application for the treatment of cancers covering articles published between 2000 and 2020. The mechanisms of action, the critical aspects of design and structureactivity relationships are also discussed.

Rational approaches of drug design for the development of selective estrogen receptor modulators (SERMs), implicated in breast cancer

Drug discovery and development have gained momentum due to the rational drug design by engaging computational tools and bioinformatics methodologies. Bioisosteric replacements and hybrid molecular approaches are the other inventive processes, used by medicinal chemists for the desired modifications of leads for clinical drug candidates. SERMs, ought to produce inhibitory activity in breast, uterus and agonist activity in other tissues, are beneficial for estrogen-like actions. ER subtypes α and β are hormone dependent modulators of intracellular signaling and gene expression, and development of ER selective ligands could be an effective approach for treatment of breast cancer. This report has critically investigated the possible designing considerations of SERMs, their in silico interactions, and potent pharmacophore generation approaches viz. indole, restricted benzothiophene [3, 2-b] indole, carborane, xanthendione, combretastatin A-4, organometallic heterocycles, OBHS-SAHA hybrids, benzopyranones, tetrahydroisoquinolines, Dig G derivatives and their specifications in drug design and development, to rationally improve the understanding in drug discovery. This also includes various strategies for the development of dual inhibitors for the management of antiestrogenic resistance.

Development of the β-lactam type molecular scaffold for selective estrogen receptor α modulator action: synthesis and cytotoxic effects in MCF-7 breast cancer cells

The estrogen receptors (ERα and ERβ) which are ligand inducible nuclear receptors are recognized as pharmaceutical targets for diseases such as osteoporosis and breast cancer. There is an increasing interest in the discovery of subtype Selective Estrogen Receptor Modulators (SERMs). A series of novel β-lactam compounds with estrogen receptor modulator properties have been synthesized. The antiproliferative effects of these compounds on human MCF-7 breast tumor cells are reported, together with binding affinity for the ERα and ERβ receptors. The most potent compound 15g demonstrated antiproliferative effects on MCF-7 breast tumor cells (IC₅₀=186 nM) and ERα binding (IC₅₀=4.3 nM) with 75-fold ERα/β receptor binding selectivity. The effect of positioning of the characteristic amine containing substituted aryl ring (on C-4 or N-1 of the β-lactam scaffold) on the antiproliferative activity and ER-binding properties of the β-lactam compounds is rationalized in a molecular modeling study.

β-Lactam estrogen receptor antagonists and a dual-targeting estrogen receptor/tubulin ligand

Twelve novel β-lactams were synthesized and their antiproliferative effects and binding affinity for the predominant isoforms of the estrogen receptor (ER), ERα and ERβ, were determined. β-Lactams 23 and 26 had the strongest binding affinities for ERα (IC50 values: 40 and 8 nM, respectively) and ERβ (IC50 values: 19 and 15 nM). β-Lactam 26 was the most potent in antiproliferative assays using MCF-7 breast cancer cells, and further biochemical analysis showed that it caused accumulation of cells in G2/M phase (mitotic blockade) and depolymerization of tubulin in MCF-7 cells. Compound 26 also induced apoptosis and downregulation of the expression of pro-survival proteins Bcl-2 and Mcl-1. Computational modeling predicted binding preferences for the dual ER/tubulin ligand 26. This series is an important addition to the known pool of ER antagonists and β-lactam 26 is the first reported compound that has dual-targeting properties for both the ER and tubulin.

A formal synthesis of ezetimibe via cycloaddition/rearrangement cascade reaction

A formal synthesis of a powerful cholesterol inhibitor, ezetymibe 1, is described. The crucial step of the synthesis is based on Cu(I)-mediated Kinugasa cycloaddition/rearrangement cascade reaction between terminal acetylene derived from acetonide of L-glyceraldehyde and suitable C,N-diarylnitrone. The adduct with (3R,4S) configuration at the azetidinone ring, obtained with high stereoselectivity, was subsequently subjected to deprotection of the diol side chain followed by glycolic cleavage and base-induced isomerization at the C3 carbon atom to afford the (3S,4S) aldehyde, which has been already transformed into ezetimibe by the Schering-Plough group.

Antiproliferative lactams and spiroenone from adlay bran in human breast cancer cell lines

Two new lactams, coixspirolactam D (1) and coixspirolactam E (2), and a new spiroenone, coixspiroenone (3), together with seven known compounds, coixspirolactam A (4), coixspirolactam B (5), coixspirolactam C (6), coixlactam (7), coixol (8), ethyl dioxindole-3-acetate (9), and isoindol-1-one (10), and two neolignans, zhepiresionol (11) and ficusal (12), were isolated from the bioactive subfraction of adlay bran ethanolic extract (ABE). Compounds 9 and 10 are the first isolates from natural resources. The structures of new compounds were identified by spectroscopic methods, including infrared (IR) spectrum, 1D and 2D nuclear magnetic resonance (NMR), and mass spectrum (MS). All of the isolated compounds were tested for antiproliferative effects on MCF-7, MDA-MB-231, and T-47D cells. Results showed that compounds 1, 3, 4, 6, and 7 at 50 μM significantly inhibited MCF-7 cell proliferation by 30.2, 19.2, 21.0, 13.5, and 32.4%, respectively; compounds 2, 4, and 7 significantly inhibited T-47D cells at 50 μM by 20.7, 24.8, and 28.9%; and compounds 1, 2, and 12 significantly inhibited MDA-MB-231 cells at 50 μM by 47.4, 25.3, and 69.3%, respectively. In conclusion, ABE has antiproliferative activities, and this effect is partially related to the presence of lactams and spiroenone.

Synthesis and evaluation of azetidinone analogues of combretastatin A-4 as tubulin targeting agents

The synthesis and antiproliferative activity of a new series of rigid analogues of combretastatin A-4 are described which contain the 1,4-diaryl-2-azetidinone (β-lactam) ring system in place of the usual ethylene bridge present in the natural combretastatin stilbene products. These novel compounds are also substituted at position 3 of the β-lactam ring with an aryl ring. A number of analogues showed potent nanomolar activity in human MCF-7 and MDA-MB-231 breast cancer cell lines, displayed in vitro inhibition of tubulin polymerization, and did not cause significant cytotoxicity in normal murine breast epithelial cells. 4-(4-Methoxyaryl)-substituted compound 32, 4-(3-hydroxy-4-methoxyaryl)-substituted compounds 35 and 41, and the 3-(4-aminoaryl)-substituted compounds 46 and 47 displayed the most potent antiproliferative activity of the series. β-Lactam 41 in particular showed subnanomolar activity in MCF-7 breast cancer cells (IC₅₀= 0.8 nM) together with significant in vitro inhibition of tubulin polymerization and has been selected for further biochemical assessment. These novel β-lactam compounds are identified as potentially useful scaffolds for the further development of antitumor agents that target tubulin.

Lead identification of conformationally restricted β-lactam type combretastatin analogues: synthesis, antiproliferative activity and tubulin targeting effects

The synthesis and study of the structure-activity relationships of a series of rigid analogues of combretastatin A-4 are described which contain the 1,4-diaryl-2-azetidinone (β-lactam) ring system in place of the usual ethylene bridge present in the natural combretastatin stilbene products. The 1,4-diaryl-2-azetidinones are unsubstituted at C-3, or contain methyl substituent(s) at C-3. The most potent compounds 12d and 12e display antiproliferative activity at nanomolar concentrations when evaluated against the MCF-7 and MDA-MB-231 human breast carcinoma cell lines. 12d exerts antimitotic effects through an inhibition of tubulin polymerisation and subsequent G2/M arrest of the cell cycle in human MDA-MB-231 breast cancer cells, with similar activity to that of CA-4. These novel β-lactam compounds are identified as potentially useful scaffolds for the further development of antitumour agents which target tubulin.