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

Abstract

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.

Derivatives Incorporating Acridine, Pyrrole, and Thiazolidine Rings as Promising Antitumor Agents

“…Some of the remaining phenyl protons experienced partial or complete overlap with one another. The doubling of certain resonances in the 13 C NMR spectrum of 6c was evident (Figure 4). Analogously, the doubling of specific resonances in both the 1 H and 13 C NMR spectra was a consistent observation across all spiro derivatives 6 (Figures S1-S3).…”

“…These transformations lead to distinct chemical environments for specific proton and carbon atoms, resulting in variations in chemical shifts for the same proton and carbon nucleus, thus manifesting as signal doubling. The dynamic properties stemming from these intramolecular rearrangements are frequently discernible in the 1 H and 13 C NMR spectra [26]. Solvent effects also present another potential factor for the observed signal doubling.…”

“…This allowed us to measure the 13 C and 2D NMR spectra for all spiro derivatives 6a-e. Based on 2D NMR data, including gCOSY, NOESY, gHSQC, and gHMBC, all chemical shifts and multiplicities were reliably and unambiguously assigned. Other solvents, such as methanol-d4, acetonitrile-d3, and benzene-d6, also reduced line broadening (Figure 2), but due to the poor solubility of spiro derivatives 6a-e, it was not possible to obtain highquality 13 C and 2D spectra. Preliminary measurements of the 1 H NMR spectra of spiro derivatives 6a-e in DMSOd 6 showed only broadened signals.…”

“…This prompted us to obtain NMR spectra in acetone-d 6 , where the signals exhibited significantly less broadening. This allowed us to measure the 13 C and 2D NMR spectra for all spiro derivatives 6a-e. Based on 2D NMR data, including gCOSY, NOESY, gHSQC, and gHMBC, all chemical shifts and multiplicities were reliably and unambiguously assigned. Other solvents, such as methanol-d 4 , acetonitrile-d 3 , and benzene-d 6 , also reduced line broadening (Figure 2), but due to the poor solubility of spiro derivatives 6a-e, it was not possible to obtain high-quality 13 C and 2D spectra.…”

“…Chronic inflammation is closely associated with tumor development and progression [ 12 ]. By targeting inflammatory pathways, pyrrole-based compounds have the potential to modulate the tumor microenvironment and inhibit cancer cell proliferation [ 13 ]. Additionally, these derivatives exhibit antioxidant activity, protecting cells from oxidative stress-induced damage [ 14 ].…”