Dual EZH2 and EHMT2 histone methyltransferase inhibition increases biological efficacy in breast cancer cells

Background: Many cancers show aberrant silencing of gene expression and overexpression of histone methyltransferases. The histone methyltransferases (HKMT) EZH2 and EHMT2 maintain the repressive chromatin histone methylation marks H3K27me and H3K9me, respectively, which are associated with transcriptional silencing. Although selective HKMT inhibitors reduce levels of individual repressive marks, removal of H3K27me3 by specific EZH2 inhibitors, for instance, may not be sufficient for inducing the expression of genes with multiple repressive marks. Results: We report that gene expression and inhibition of triple negative breast cancer cell growth (MDA-MB-231) are markedly increased when targeting both EZH2 and EHMT2, either by siRNA knockdown or pharmacological inhibition, rather than either enzyme independently. Indeed, expression of certain genes is only induced upon dual inhibition. We sought to identify compounds which showed evidence of dual EZH2 and EHMT2 inhibition. Using a cell-based assay, based on the substrate competitive EHMT2 inhibitor BIX01294, we have identified proof-of-concept compounds that induce re-expression of a subset of genes consistent with dual HKMT inhibition. Chromatin immunoprecipitation verified a decrease in silencing marks and an increase in permissive marks at the promoter and transcription start site of re-expressed genes, while Western analysis showed reduction in global levels of H3K27me3 and H3K9me3. The compounds inhibit growth in a panel of breast cancer and lymphoma cell lines with low to sub-micromolar IC50s. Biochemically, the compounds are substrate competitive inhibitors against both EZH2 and EHMT1/2. Conclusions: We have demonstrated that dual inhibition of EZH2 and EHMT2 is more effective at eliciting biological responses of gene transcription and cancer cell growth inhibition compared to inhibition of single HKMTs, and we report the first dual EZH2-EHMT1/2 substrate competitive inhibitors that are functional in cells

Chiroptical studies on brevianamide B: Vibrational and Electronic Circular Dichroism confronted

Chiroptical spectroscopy, such as electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) are highly sensitive techniques to probe molecular conformation, configuration, solvation and aggregation. Here we report the application of these techniques to study the fungal metabolite brevianamide B. Comparison of the experimental ECD and VCD spectra with the density functional theory (DFT) simulated counterparts establishes that VCD is the more reliable technique to assign absolute configuration due to the larger functional and dispersion dependence of computed ECD spectra. Despite a low amount of available material, and a relatively unusual example of using VCD carbonyl multiplets, the absolute configuration could be reliably predicted, strengthening the case for application of VCD in the study of complex natural products. Spectral evidence for or against the formation of a dimeric aggregate is discussed; in solution the VCD spectra strongly suggest only monomeric species are present.Chiroptical spectroscopy, such as electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) are highly sensitive techniques to probe molecular conformation, configuration, solvation and aggregation. Here we report the application of these techniques to study the fungal metabolite brevianamide B. Comparison of the experimental ECD and VCD spectra with the density functional theory (DFT) simulated counterparts establishes that VCD is the more reliable technique to assign absolute configuration due to the larger functional and dispersion dependence of computed ECD spectra. Despite a low amount of available material, and a relatively unusual example of using VCD carbonyl multiplets, the absolute configuration could be reliably predicted, strengthening the case for application of VCD in the study of complex natural products. Spectral evidence for or against the formation of a dimeric aggregate is discussed; in solution the VCD spectra strongly suggest only monomeric species are present.Chiroptical spectroscopy, such as electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) are highly sensitive techniques to probe molecular conformation, configuration, solvation and aggregation. Here we report the application of these techniques to study the fungal metabolite brevianamide B. Comparison of the experimental ECD and VCD spectra with the density functional theory (DFT) simulated counterparts establishes that VCD is the more reliable technique to assign absolute configuration due to the larger functional and dispersion dependence of computed ECD spectra. Despite a low amount of available material, and a relatively unusual example of using VCD carbonyl multiplets, the absolute configuration could be reliably predicted, strengthening the case for application of VCD in the study of complex natural products. Spectral evidence for or against the formation of a dimeric aggregate is discussed; in solution the VCD spectra strongly suggest only monomeric species are present

On the histone lysine methyltransferase activity of fungal metabolite chaetocin.

Histone lysine methyltransferases (HKMTs) are an important class of targets for epigenetic therapy. 1 (chaetocin), an epidithiodiketopiperazine (ETP) natural product, has been reported to be a specific inhibitor of the SU(VAR)3-9 class of HKMTs. We have studied the inhibition of the HKMT G9a by 1 and functionally related analogues. Our results reveal that only the structurally unique ETP core is required for inhibition, and such inhibition is time-dependent and irreversible (in the absence of DTT), ultimately resulting in protein denaturation. Mass spectrometric data provide a molecular basis for this effect, demonstrating covalent adduct formation between 1 and the protein. This provides a potential rationale for the selectivity observed in the inhibition of a variety of HKMTs by 1 in vitro and has implications for the activity of ETPs against these important epigenetic targets

Real‐world data for marginal zone lymphoma patients in the French REALYSA cohort: The REALMA study

International audienceAbstract Marginal Zone Lymphoma (MZL) comprises three subtypes: extranodal MZL (EMZL), splenic MZL (SMZL) and nodal MZL (NMZL). Since clinical trials have limited representativeness, there is a need for real‐world data (RWD) evidence in MZL. Real‐world data in Lymphoma and survival in Adults (REALYSA) is a prospective multicentric French cohort of newly diagnosed lymphoma patients. This study consists of the first abstraction of MZL patients prospectively included in REALYSA between 12/2018 and 01/2021 with at least 1 year of follow‐up. It provides a landscape description of clinical characteristics, initial workup, quality of life and first‐line therapy performed in routine practice. Among 207 included patients, 122 presented with EMZL, 51 with SMZL and 34 with NMZL. At baseline, median age was 67 years (range 28–96), and patients reported a favorable global health status (75/100 (IQR 58,83)) – which was higher in NMZL and lower in SMZL patients ( p = 0.006). 18FDG‐PET/CT was frequently performed at initial workup (EMZL 72%, SMZL 73%, NMZL 85%). Active surveillance was the initial management for 58 (28%) patients. The most prescribed therapies were rituximab‐chlorambucil in the EMZL population (30%), rituximab monotherapy in the SMZL population (37%) and R‐CHOP (24%)/bendamustine‐rituximab (15%) in the NMZL population. At end of first line, overall response rate was 93% among treated patients with 75% of complete response. This French nationwide study provided for the first time prospective RWD on clinical characteristics, initial management and treatment response of MZL patients