Valentina Gigliotti

We previously demonstrated that in BAP1-proficient pleural mesothelioma cells, CDKN2A is critical for mediating the response to selective EZH2 inhibition and highlighted a complex interplay between epigenetic regulation and the tumor immune microenvironment. In this study, we employed a quantitative proteomic mass spectrometry approach to assess alterations in protein expression following EZH2 inhibition in BAP1- and CDKN2A-proficient mesothelioma cells cultured as spheroids. Additionally, we analyzed extracellular vesicles (EVs), which were isolated through tangential flow filtration. Flow cytometric analysis and co-culture systems were used to characterize the effects of EVs on neutrophils. Upon EZH2 inhibition, we demonstrated RAB27b and CD63 upregulation and increased release of extracellular vesicles. We found that a brief exposure to EVs derived from EZH2 inhibitor-treated cells skewed naïve neutrophils toward a pro-tumor phenotype characterized by high levels of PD-L1 and MSLN (Mesothelin) expression on the surface. These EV-elicited neutrophils suppressed T cell proliferation while enhancing tumor cell growth. Moreover, we observed changes in the EV cargo derived from EZH2 inhibitor-treated spheroids. Our findings highlight the significant role of EVs in creating an immunosuppressive microenvironment, and underscore the urgent need for further investigation into the regulation of neutrophil biology and function in the PM.

Background/Objectives: Methyltransferase EZH2-mediated H3K27me3 is involved in liver inflammation and fibrosis, but its role in hepatic metabolic derangements is not yet clearly defined. We investigated if a high-fat diet (HFD) induced early changes in EZH2 expression and H3K27 me3 in the liver of mice. Methods: Five-week-old mice were fed an HFD or a low-fat diet (Control) for 2 weeks (2 W) or 8 weeks (8 W). Body weight was recorded weekly. Glycemia and oral glucose tolerance were assessed at baseline and after 2 W–8 W. Finally, livers were collected for further analysis. Results: As expected, mice that received 8 W HFD showed an increase in body weight, glycemia, and liver steatosis and an impairment in glucose tolerance; no alterations were observed in 2 W HFD mice. Eight weeks of HFD caused hepatic EZH2 nuclear localization and increased H3 K27me3; surprisingly, the same alterations occurred in 2 W HFD mice livers, even before overweight onset. We demonstrated that selective EZH2 inhibition reduced H3K27me3 and counteracted lipid accumulation in HUH-7 cells upon palmitic acid treatment. Conclusions: In conclusion, we point to EZH2/H3K27me3 as an early epigenetic event occurring in fatty-acid-challenged livers both in vivo and in vitro, thus establishing EZH2 as a potential pharmacological target for metabolic derangements.

Aldehyde dehydrogenases of the subfamily 1A (ALDH1A) are enzymes necessary for the oxidation of all-trans or 9-cis retinal to retinoic acid (RA). Retinoic acid and its derivatives are important for normal development and maintenance of epithelia, reproduction, memory, and immune function in adults. Moreover, in recent years, it has been demonstrated that ALDH1A members are also expressed and functional in several human cancers where their role is not limited to the synthesis of RA. Here, we review the current knowledge about ALDH1A3, one of the 1A isoforms, in cancers with an emphasis on two of the deadliest tumors that affect humans: glioblastoma multiforme and mesothelioma. In both tumors, ALDH1A3 is considered a negative prognostic factor, and its level correlates with excessive proliferation, chemoresistance, and invasiveness. We also review the recent attempts to develop both ALDH1A3-selective inhibitors for cancer therapy and ALDH1A3-specific fluorescent substrates for fluorescence-guided tumor resection.