KDM6B histone demethylase is an epigenetic regulator of estrogen receptor β expression in human pleural mesothelioma

A Selective ALDH1A3 Inhibitor Impairs Mesothelioma 3-D Multicellular Spheroid Growth and Neutrophil Recruitment

Aldehyde dehydrogenase 1A3 (ALDH1A3), one of the three members of the aldehyde dehydrogenase 1A subfamily, has been associated with increased progression and drug resistance in various types of solid tumours. Recently, it has been reported that high ALDH1A3 expression is prognostic of poor survival in patients with malignant pleural mesothelioma (MPM), an asbestos-associated chemoresistant cancer. We treated MPM cells, cultured as multicellular spheroids, with NR6, a potent and highly selective ALDH1A3 inhibitor. Here we report that NR6 treatment caused the accumulation of toxic aldehydes, induced DNA damage, CDKN2A expression and cell growth arrest. We observed that, in CDKN2A proficient cells, NR6 treatment induced IL6 expression, but abolished CXCL8 expression and IL-8 release, preventing both neutrophil recruitment and generation of neutrophil extracellular traps (NETs). Furthermore, we demonstrate that in response to ALDH1A3 inhibition, CDKN2A loss skewed cell fate from senescence to apoptosis. Dissecting the role of ALDH1A3 isoform in MPM cells and tumour microenvironment can open new fronts in the treatment of this cancer.

Unsymmetric Cisplatin-Based Pt(IV) Conjugates Containing a PARP-1 Inhibitor Pharmacophore Tested on Malignant Pleural Mesothelioma Cell Lines

Cisplatin is widely employed as a first-line chemotherapeutic agent for many solid tumors, including malignant pleural mesothelioma (MPM). However, its clinical use is limited by heavy side effects and acquired resistance, the latter being mainly related to enhanced DNA repair. Many clinical trials using combinations of platinum drugs and PARP-1 inhibitors (PARPis) have been carried out, with the hope that such combinations might lead to improved therapeutic efficacy against tumors. Here, the synthesis and efficacy in reducing MPM cell viability of four cisplatin-based Pt(IV) prodrugs containing the PARPi 3-aminobenzamide (3-ABA) fragment are described. The most promising conjugate is more effective than cisplatin or cisplatin/3-ABA combination, administered in equimolar doses, in inhibiting PARP-1 activity and inducing apoptosis in BRCA1/2 wild type MPM cells, grown as monolayer or as multicellular spheroids.

CDKN2A Determines Mesothelioma Cell Fate to EZH2 Inhibition

Malignant pleural mesothelioma is an aggressive cancer, heterogeneous in its presentation and behaviour. Despite an increasing knowledge about molecular markers and their diagnostic and prognostic value, they are not used as much as they might be for treatment allocation. It has been recently reported that mesothelioma cells that lack BAP1 (BRCA1 Associated Protein) are sensitive to inhibition of the EZH2 (Enhancer of Zeste Homolog 2) histone methyltransferase. Since we observed strong H3K27me3 (histone H3 lysine 27 trimetylation) immunoreactivity in BAP1 wild-type mesothelioma biopsies, we decided to characterize in vitro the response/resistance of BAP1 wild-type mesothelioma cells to the EZH2 selective inhibitor, EPZ-6438. Here we demonstrate that BAP1 wild-type mesothelioma cells were rendered sensitive to EPZ-6438 upon SIRT1 (Sirtuin 1) silencing/inhibition or when cultured as multicellular spheroids, in which SIRT1 expression was lower compared to cells grown in monolayers. Notably, treatment of spheroids with EPZ-6438 abolished H3K27me3 and induced the expression of CDKN2A (Cyclin-Dependent Kinase Inhibitor 2A), causing cell growth arrest. EPZ-6438 treatment also resulted in a rapid and sustained induction of the genes encoding HIF2α (Hypoxia Inducible Factor 2α), TG2 (Transglutaminase 2) and IL-6 (Interleukin 6). Loss of CDKN2 is a common event in mesothelioma. CDKN2A silencing in combination with EPZ-6438 treatment induced apoptotic death in mesothelioma spheroids. In a CDKN2A wild-type setting apoptosis was induced by combining EPZ-6438 with 1-155, a TG2 selective and irreversible inhibitor. In conclusion, our data suggests that the expression of CDKN2A predicts cell fate in response to EZH2 inhibition and could potentially stratify tumors likely to undergo apoptosis.

Inhibition of the Histone Methyltransferase EZH2 Enhances Protumor Monocyte Recruitment in Human Mesothelioma Spheroids

Malignant pleural mesothelioma (MPM) is a highly aggressive cancer with a long latency period and dismal prognosis. Recently, tazemetostat (EPZ-6438), an inhibitor of the histone methyltransferase EZH2, has entered clinical trials due to the antiproliferative effects reported on MPM cells. However, the direct and indirect effects of epigenetic reprogramming on the tumor microenvironment are hitherto unexplored. To investigate the impact of tumor-associated macrophages (TAMs) on MPM cell responsiveness to tazemetostat, we developed a three-dimensional MPM spheroid model that recapitulates in vitro, both monocytes’ recruitment in tumors and their functional differentiation toward a TAM-like phenotype (Mo-TAMs). Along with an increased expression of genes for monocyte chemoattractants, inhibitory immune checkpoints, immunosuppressive and M2-like molecules, Mo-TAMs promote tumor cell proliferation and spreading. Prolonged treatment of MPM spheroids with tazemetostat enhances both the recruitment of Mo-TAMs and the expression of their protumor phenotype. Therefore, Mo-TAMs profoundly suppress the antiproliferative effects due to EZH2 inhibition in MPM cells. Overall, our findings indicate that TAMs are a driving force for MPM growth, progression, and resistance to tazemetostat; therefore, strategies of TAM depletion might be evaluated to improve the therapeutic efficacy of pharmacological inhibition of EZH2.

KDM6B (JMJD3) and its dual role in cancer

Epigenetic modifications play a fundamental role in the regulation of gene expression and cell fate. During the development of cancer, epigenetic modifications appear that favor cell proliferation and migration, but at the same time prevent differentiation and apoptosis, among other processes. KDM6B is a histone demethylase that specifically removes methyl groups from H3K27me3, thus allowing re-expression of its target genes. It is currently known that KDM6B can act as both a tumor suppressor and an oncogene depending on the cellular context. Therefore, in this work we summarize the current knowledge of the role that KDM6B plays in different oncological contexts, and we try to orient it towards its clinical application.

Hypoxia-driven epigenetic regulation in cancer progression: A focus on histone methylation and its modifying enzymes

The mechanism underlying hypoxia-driven chromatin remodeling is a long-lasting question. For the last two decades, this question has been resolved in part. It is now widely agreed that hypoxia dynamically changes the methylation status of histones to control gene expression. Hypoxia-inducible factor (HIF) plays a central role in cellular responses to hypoxia through transcriptional activation of numerous genes. At least in part, the hypoxic regulation of histone methylation is attributed to the HIF-mediated expression of histone modifying enzymes. Protein hydroxylation and histone demethylation have emerged as the oxygen sensing processes because they are catalyzed by a family of 2-oxoglutarate (2OG)-dependent dioxygenases whose activities depend upon the ambient oxygen level. Recently, it has been extensively investigated that the 2OG dioxygenases oxygen-dependently regulate histone methylation. Nowadays, the hypoxic change in the histone methylation status is regarded as an important event to drive malignant behaviors of cancer cells. In this review, we introduced and summarized the cellular processes that govern hypoxia-driven regulation of histone methylation in the context of cancer biology. We also discussed the emerging roles of histone methyltransferases and demethylases in epigenetic response to hypoxia.

Specific low-frequency electromagnetic fields induce expression of active KDM6B associated with functional changes in U937 cells

In this study, we investigated the effects of specific low-frequency electromagnetic field sequences on U937 cells, an in vitro model of human monocyte/macrophage differentiation. U937 cells were exposed to electromagnetic stimulation by means of the SynthéXer system using two similar sequences, XR-BC31 and XR-BC31/F. Each sequence was a time series of 29 wave segments, equal to a total duration of 77 min. Here, we report that exposure (4 d, once a day) of U937 cells to the XR-BC31 setting, but not to the XR-BC31/F, resulted in increased expression of the histone demethylase KDM6B along with a global reduction in histone H3 lysine 27 tri-methylation (H3K27me3). Furthermore, exposure to the XR-BC31 sequence induced differentiation of U937 cells towards a macrophage-like phenotype displaying a KDM6B dependent increase in expression and secretion of the anti-inflammatory interleukins (ILs), IL-10 and IL-4. Importantly, all the observed changes were highly dependent on the nature of the sequence. Our results open a new way of interpretation for the effects of low-frequency electromagnetic fields observed in vivo. Indeed, it is conceivable that a specific low-frequency electromagnetic fields treatment may cause the reprogramming of H3K27me3 and cell differentiation.

Expression of estrogen receptor beta (ERβ) and its prognostic value in pleural mesothelioma

Background

Overexpression of estrogen receptors in malignant pleural mesothelioma has shown an independent relation with a better prognosis of survival, and the use of selective estrogen receptor beta (ERβ) agonists increases the susceptibility to antitumor treatment.

Methods

This was a retrospective single center study that analyzed the response of malignant pleural mesothelioma with an expression of ERβ to first-line chemotherapy. The study included patients with pleural mesothelioma pathologically confirmed between 2013 and 2016 at the National Institute for Respiratory Disease (INER), who underwent an immunohistochemistry assay for ERβ (mouse monoclonal antibody PPG5/10). The primary endpoint was the response to chemotherapy based on RECIST 1.1 according to the ERβ expression; secondary outcomes were the overall survival (OS) and progression-free survival (PFS).

Results

We included 22 patients, regarding the expression of ERβ, 17 (77.2%) patients had high or moderate degree, while 5 (22.7%) had low degree or null expression. The response to treatment as by RECIST 1.1, 12 (54.5%) had partial response, 5 (22.7%) had stable disease, and 3 (13.6%) had progression. None of the patients had a complete response. Of those who had a partial response, 9 (75%) had a high or moderate degree of ERβ expression in tumor cells, and 3 (25%) had a low or null degree of expression.

Conclusions

High and moderate expression of ERβ group with advanced clinical stage malignant pleural mesothelioma was associated with a tendency of higher OS and better response to chemotherapy treatment resulting in longer PFS although statistical significance was not achieved.

Regulation of sex hormone receptors in sexual dimorphism of human cancers

Gender differences in the incidences of cancers have been found in almost all human cancers. However, the mechanisms that underlie gender disparities in most human cancer types have been under-investigated. Here, we provide a comprehensive overview of potential mechanisms underlying sexual dimorphism of each cancer regarding sex hormone signaling. Fully addressing the mechanisms of sexual dimorphism in human cancers will greatly benefit current development of precision medicine. Our discussions of potential mechanisms underlying sexual dimorphism in each cancer will be instructive for future cancer research on gender disparities.

Hypoxia promotes acquisition of aggressive phenotypes in human malignant mesothelioma

BACKGROUND

Hypoxia is a hallmark of the solid tumor microenvironment and is associated with poor outcomes in cancer patients. The present study was performed to investigate mechanisms underlying the hypoxia-induced phenotypic changes using human malignant mesothelioma (HMM) cells.

METHODS

Hypoxic conditions were achieved by incubating HMM cells in the air chamber. The effect of hypoxia on phenotype changes in HMM cells was investigated by performing in vitro clonogenicity, drug resistance, migration, and invasion assays. Signaling pathways and molecules involved in the more aggressive behaviors of HMM cells under hypoxia were investigated. A two-tailed unpaired Student's t-test or one-way ANOVA with Bonferroni post-test correction was used in this study.

RESULTS

Hypoxic conditions upregulated hypoxia-inducible factor 1 alpha (HIF-1α) and HIF-2α in parallel with the upregulation of its target, Glut-1, in HMM cells. In vitro clonogenicity of HMM cells was significantly increased in hypoxic conditions, but the proliferation of cells at a high density in hypoxia was lower than that in normoxic conditions. The expression levels of HIF-2α and Oct4 were increased in hypoxic HMM cells. The percentage of cells with high CD44 expression was significantly higher in HMM cells cultured in hypoxia than those cultured in normoxia. Hypoxia significantly enhanced the resistance of HMM cells to cisplatin, which occurred through cytoprotection against cisplatin-induced apoptosis. While cisplatin treatment decreased the ratio of Bcl-2 to Bax in normoxic condition, hypoxia conversely increased the ratio in HMM cells treated with cisplatin. Hypoxia increased the mobility and invasiveness of HMM cells. Epithelial to mesenchymal transition was promoted, which was indicated by the repression of E-cadherin and the concomitant increase of vimentin in HMM cells.

CONCLUSIONS

The data illustrated that hypoxic conditions augmented the aggressive phenotypes of HMM cells at the biological and molecular levels. The present study provides valuable background information beginning to understand aggressiveness of HMM in tumor microenvironments, suggesting that a control measure for tumor hypoxia may be an effective therapeutic strategy to reduce the aggressiveness of cancer cells in HMM patients.

Potential Health Risk of Endocrine Disruptors in Construction Sector and Plastics Industry: A New Paradigm in Occupational Health

Endocrine disruptors (EDs) belong to large and diverse groups of agents that may cause multiple biological effects associated with, for example, hormone imbalance and infertility, chronic diseases such as diabetes, genome damage and cancer. The health risks related with the exposure to EDs are typically underestimated, less well characterized, and not regulated to the same extent as, for example, carcinogens. The increased production and utilization of identified or suspected EDs in many different technological processes raises new challenges with respect to occupational exposure settings and associated health risks. Due to the specific profile of health risk, occupational exposure to EDs demands a new paradigm in health risk assessment, redefinition of exposure assessment, new effects biomarkers for occupational health surveillance and definition of limit values. The construction and plastics industries are among the strongest economic sectors, employing millions of workers globally. They also use large quantities of chemicals that are known or suspected EDs. Focusing on these two industries, this short communication discusses: (a) why occupational exposure to EDs needs a more specific approach to occupational health risk assessments, (b) identifies the current knowledge gaps, and (c) identifies and gives a rationale for a future occupational health paradigm, which will include ED biomarkers as a relevant parameter in occupational health risk assessment, surveillance and exposure prevention.

Targeting estrogen receptor beta (ERβ) for treatment of ovarian cancer: importance of KDM6B and SIRT1 for ERβ expression and functionality

Estrogen receptor (ER) β has growth inhibitory and chemo drug potentiating effect on ovarian cancer cells. We studied the dependence of ERβ function on the presence of KDM6B and SIRT1 in human ovarian cancer cells in vitro. Activation of ERβ with the subtype-selective agonist KB9520 resulted in significant inhibition of human ovarian cancer cell growth. KB9520-activated ERβ had an additive effect on growth inhibition in combination with cisplatin and paclitaxel, respectively. Loss of KDM6B expression had a negative effect on ERβ function as a ligand-dependent inhibitor of ovarian cancer cell growth. In contrast, loss or inhibition of SIRT1 deacetylase activity restored ligand-activated ERβ functionality. Presented data suggest that selective targeting of ERβ with an agonist potentiate chemotherapy efficacy for the treatment of ovarian cancer and that downregulation or inhibition of SIRT1 may further enhance its therapeutic effect.